Polymers - TA仪器

What Your Material Specification Sheet Doesn’t Tell You

Juli Varvarezis — Mon, 23 Sep 2024 20:31:25 +0000

What Your Material Specification Sheet Doesn’t Tell You

Julienne Regele | Andy Simon | Morgan Ulrich
September 23, 2024

When it comes to selecting materials for your next innovative product, the material specification sheet is likely the first place that you will turn. This document provides core properties measured by the manufacturer and serves as an essential tool for supplier verification and new product development. However, while these sheets are reliable and provide a standard method for comparison, they often fail to tell the whole story.

For successful material selection, product performance, failure prevention, it is important to go beyond the spec sheet and conduct in-house testing. This proactive approach will save you both time and money by facilitating informed material choices and enhancing product design.

The Role of a Material Specification Sheet

A material specification sheet provides a snapshot of a material’s key properties as measured by the manufacturer. These properties are typically measured using standardized methods such as ASTM or ISO standards, offering some consistency and comparability across different materials. The spec sheet can be used for various purposes:

Supplier Verification: Ensuring that the material provided by a supplier meets the necessary criteria for production.
New Product Development: Aiding in the selection of new materials during the design phase of a product.

While spec sheets provide a foundational understanding, relying solely on them can be risky; they often provide incomplete information to know the material’s performance or predict lifetime of a product, especially in real-world application conditions.

The Limitations of Spec Sheets

Spec sheets are foundational for understanding general material properties, but they often lack detailed information about how a material will behave under specific conditions, such as the effects of different temperatures, prolonged stress or stress cycles, or exposure to harsh environments. Uncovering these blind spots is necessary for improving processing conditions, understanding material lifespan, and ultimately selecting the right material at the start of your development process.

What Should You Consider?

To fully understand a material’s properties and ensure it meets your specific requirements, additional testing is required. Here are some critical aspects to consider:

Environmental Impacts

Materials can perform differently under various environmental conditions, such as UV exposure, or humidity. Due to the impracticality of inspecting materials in active use, such as polymer coatings on wires embedded in walls, a quick test lasting only a few minutes to hours is conducted to estimate the long-term stability of these materials over decades.¹

Differential scanning calorimetry (DSC) with oxidative induction time (OIT) analysis helps predict the aging and degradation of polymers, guiding material selection for longevity and reliability. For instance, polymers exposed to heat, oxygen, or light degrade faster, and OIT provides insights into their lifespan.

A variation of the OIT test, known as high-pressure OIT (HPOIT), is becoming increasingly popular. Proponents argue that oxidative data obtained under high pressure and temperature conditions align more closely with results from traditional, accelerated aging tests. The HPOIT test offers two primary advantages: high pressure raises the boiling points of additives, reducing their volatility, and it increases the concentration of the reacting oxidizing gas. This enables the use of lower test temperatures or significantly reduces test durations at comparable temperatures.²

Alternatively, high-pressure thermogravimetric analysis (HP-TGA) simulates extended exposure to harsh environments by using a combination of heat and elevated pressure. It is particularly useful for materials used in industrial applications, such as cabling for electrical or fiber optic systems. Safeguarding polymers against catastrophic degradation when exposed to direct sunlight or buried underground is crucial for these applications.³

Mechanical Behavior

Understanding the mechanical properties of materials beyond the scope of the datasheet is essential for nearly every application. For example, the following should be considered:

Temperature Effects: Materials can exhibit drastically different properties at varying temperatures. Datasheets typically only list tensile properties at room temperature, but materials are frequently expected to perform under higher or lower temperatures.
Long-Term Loading: What happens if a material is subjected to a load for weeks, months, or even years? Will it deform over time, i.e., creep? Will it crack under prolonged stress, i.e., creep rupture? For example, a clothing hanger may perform well under normal use, but storing a heavy coat over winter could cause the neck to elongate and eventually break. In this example, the clothing hanger began failing to perform its function (holding up clothes) due to creep and fell off the rod. Had it not fallen due to deformation, it would have eventually cracked due to creep rupture.

Repeated Loading: In a process known as fatigue, repeated loading can cause accumulating damage, leading to fracture. It is important to know the stress levels and number of loading cycles a material can withstand before failure. Polymers exhibit fatigue in a very different way than metals and fatigue life estimates cannot be extrapolated from tensile strength as easily. Additionally, the usage temperature can have a significant impact on fatigue life at much lower temperatures than metals.

Mechanical test instruments evaluate durability and mechanical characteristics under various stresses (forces), frequencies, and environmental conditions. Specifically, Electroforce load frame instruments measure a sample’s response to force, whether it is a single push or pull (tensile test), repetitive load (fatigue), or creep/stress-relaxation test. Mechanical testing also accounts for environmental effects by testing in temperature-controlled air, gas, or fluid submersion.

Why Does It Matter?

Material testing is crucial in manufacturing and product development because it minimizes the risk of product failure, which can have costly and even dangerous consequences. Unexpected material behavior can lead to malfunctions, product recalls, and reputational damage.

For example, a woven fiberglass composite had a manufacturer’s recommended operating temperature up to 130°C. However, Dynamic Mechanical Analysis (DMA) testing revealed that the material’s storage modulus and loss modulus began to change around 100°C.⁴ Further fatigue testing data revealed that the material had a 90% reduction in its fatigue life at 100°C.⁵ Manufacturers could have mistakenly put this material into products used at high temperatures, such as baking, without realizing that it was highly likely to break.

Conducting thorough testing upfront provides higher confidence in material choices, ultimately saving time, money, and resources. Moreover, comprehensive material testing contributes to better long-term product reliability and performance. By thoroughly examining how a material responds to factors like fatigue, creep, and environmental degradation, manufacturers can design products that not only meet initial requirements but also maintain integrity throughout their life cycle. This proactive approach fosters innovation in product design, as engineers gain a deeper understanding of the material’s limits and capabilities, allowing for the creation of more efficient, safer, and longer-lasting products.

Comprehensive Testing: A Necessity, Not a Luxury

Going beyond the spec sheet is not just a recommendation; it is a necessity. By investing in additional testing, such as OIT using DSC and HP-TGA, you can uncover profound insights about material performance. By adding DMA and Electroforce fatigue testing to your testing suite, you can better predict material properties at various temperature conditions and repeat loading. These insights will ensure you make informed decisions that save time, money, and valuable resources by selecting the proper material for your application conditions. TA Instruments is here to support you with precision instruments and technical expertise, ensuring you have the tools needed to expertly evaluate materials and make the best decisions for your projects.

References and Further Reading

TA Instruments. [Online] Oxidative Stability of Polyolefins. Available at: https://www.tainstruments.com/applications-notes/oxidative-stability-of-polyolefins-ta481/
Tikuisis, T., et al. High Pressure Oxidative Induction Time Analysis By Differential Scanning Calorimetry. TA Instruments: Thermal Analysis & Rheology.
TA Instruments. [Online] Prevent Failing of Performance Polymers Applied at High Pressures. Available at: https://www.tainstruments.com/applications-notes/prevent-failing-of-performance-polymers-applied-at-high-pressures/
TA Instruments. [Online] 4 Polymer Insights from Dynamic Mechanical Analysis. Available at: https://www.tainstruments.com/4-polymer-insights-from-dynamic-mechanical-analysis/
TA Instruments. [Online] Flexural Fatigue Behavior of Woven Fiberglass Composites at Elevated Temperature. Available at: https://www.tainstruments.com/applications-notes/flexural-fatigue-behavior-of-woven-fiberglass-composites-at-elevated-temperature/

Other Resources

eBook – How to Ensure Polymer Strength and Durability with Mechanical Testing
Blog – 3 Essential Types of Mechanical Testing for Polymer Development
Blog – 4 Polymer Insights from Dynamic Mechanical Analysis
Application Note – Tensile and Fatigue Properties of Additively Manufactured Polyamides
Application Note – Evaluation Of The Loss Of Polymer Strength And Durability Due To Fatigue Loading And Manufacturing Artifacts
Application Note – Flexural Fatigue Behavior of Woven Fiberglass Composites at Elevated Temperature

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Linear Viscoelastic Region: Why It’s Crucial in Materials Testing

Juli Varvarezis — Mon, 09 Sep 2024 20:29:09 +0000

Linear Viscoelastic Region: Why It’s Crucial in Materials Testing

Keith Coasey | Morgan Ulrich
September 9, 2024

Our world is brimming with viscoelastic materials: The dough you knead before baking a fresh loaf, the Silly Putty your toddler slaps against the wall, the rubber gaskets that create an airtight seal on an airplane door. Testing those materials by applying controlled deformations (strains) or forces (stresses) at various timescales, temperatures, and/or humidities allows for the optimization of properties and ensures durability and safety. Only through specialized tools in a lab setting can researchers thoroughly characterize (and thus predict in the real world) an essential material property: the linear viscoelastic region.

Researchers and product development teams across industries (from construction to food processing to pharmaceuticals and more) work with viscoelastic materials every day. Understanding and accurately modeling viscoelastic behavior supports innovation when developing the snacks you eat, the polymer fibers that make up your clothing, and creating more durable sustainable materials for the structures where you live. Like the word itself, viscoelasticity combines two properties in materials science:

Viscosity: The way material flows over time in response to stress such as gravity (i.e., the slow flow of honey compared to water, comparing the “thickness” of tomato juice to ketchup)

Elasticity: The tendency of a solid to resist deformation (Such as comparing the mechanical resistance of a metal spring to that of a rubber band)

When a material combines both properties (in varying degrees), it’s considered viscoelastic. Ketchup, gelatin, and rubber, for example, all have viscoelastic properties. Although they are drastically different upon first glance, all share solid-like (elastic) and liquid-like (viscous) characteristics, but in different proportions. How, then, do researchers understand the ways those materials change, deform, or even fail under certain types of stress (like flowing, stretching or temperature fluctuation)?

You’ll need to explore the material’s linear viscoelastic region.

What is the Linear Viscoelastic Region (LVR)?

In scientific terms, it’s the linear relationship between the complex stress put on a material and the overall magnitude of deformation (strain), which remains linear at relatively low strains. At strains/stresses that extent beyond the LVR, the relationship becomes nonlinear, with the stress typically increasing less with additional strain, indicative of the onset of network failure. A complex liquid will have a larger LVR than a brittle solid which typically fails at lower strains. In simpler terms, it’s the range in which a material predictably reacts (and can return to its original form) under different amounts of strain/stress.

Think of a rubber band. Pull it gently before letting go, and it will return to its original, relaxed state. Stretch it more and more, and it will still return to form – up to a point. Eventually, you might see a slight tear or a color change when it relaxes. Pull hard enough, and the band will snap altogether. Once you have materially changed the band’s properties, you’ve left the linear viscoelastic region and entered its “critical strain” — the threshold at which the material’s molecular structure fundamentally changes.

Characteristics of the Linear Viscoelastic Region

Determining the LVR should be one of the first steps when studying or testing viscoelastic materials. The LVR is a function of temperature, humidity, and the rate of the deformation. Generally, the LVR increases with increasing temperature, so once the LVR is characterized at a single deformation rate at a specific temperature, the temperature can be increased without exceeding the critical strain.

There are two ways to consider the LVR and its relation to strain/stress. First, when a material is within the LVR, the force (stress) required to deform the material increases or decreases in a fashion relative to the extent deformation. Once stretched beyond the critical deformation, it requires increasingly less additional force to achieve incrementally higher deformations. In another case, if considering hanging weights from a spring or rubber band, one is applying stress (force) in the form of weight in order to deform the sample. Within the LVR, if the weight is incrementally increased, the spring or rubber band will elongate in proportion to the weight. Once beyond the critical strain (which corresponds to a critical stress), the spring or rubber band starts to elongate more and more with each additional unit of stress/weight.

Figure 1: Stress vs strain in an oscillation strain sweep experiment on polystyrene at 250 °C and 1 Hz. The critical strain is marked on the plot.

Say you’re developing a delicious new yogurt (itself, a viscoelastic material). But you know that the trucks headed to deliver that yogurt will traverse bumpy roads. You’ll need to test how that yogurt reacts under all of that shaking (gravitational forces). If the network structure of the yogurt is too weak, in the sense that the end of the LVR corresponds to low strains or stresses relative to those experienced in the truck, then the yogurt network structure will be disrupted. Rather than having a continuous creamy texture, the yogurt can be broken up into separate chunks, sometimes with separated liquid, and in essence more akin to the texture of cottage cheese than yogurt.

Understanding the characteristics within the yogurt’s LVR helps not only formulate a yogurt that is mechanically robust enough for transport, but also still has a texture/viscoelasticity that is favorable to eat. Eating creates its own characteristic stresses and deformations in the mouth, which need to be accounted for (Who would want to eat chewy yogurt?).

Why is the Linear Viscoelastic Region Crucial in Materials Testing?

Think of the LVR as a set of guardrails. When you use too much stress, you’ll cross the critical strain threshold and irrevocably change its structure. Add too little stress, though, and you end up with noisy data. Staying within the LVR during dynamic (oscillatory) mechanical testing allows for the ideal probing of the sample in a quasi-equilibrium state; where its mechanical structure can be probed at a variety of conditions such as at various temperatures (mimicking real-world conditions), without disrupting destroying the sample structure mechanically and with excellent data resolution/reproducibility.

The LVR is also essential in understanding the complete rheological characteristics of a material (how it flows through the environment around it). Practically, this helps manufacturers and product researchers choose, replace, or refine the materials they need before full-scale production begins.

How to Determine a Material’s Linear Viscoelastic Region

Three variables will change the LVR of any material: Temperature, humidity, and the rate of deformation (frequency). A piece of rubber pulled in sub-freezing weather 1,000 times will react differently than one pulled twice on a humid August afternoon.

Because our environment (and how we use materials) constantly changes, there are two accurate methods to determine LVR.

Experimental: Specialized lab equipment like a dynamic mechanical analyzer (DMA) which is primarily for solids or a rheometer which primarily deals with liquids, provide precise data to determine the LVR. These instruments can change temperature, humidity, and stress levels—efficiently repeating a cycle thousands of times.
Analytical: Because the LVR is, by its nature, linear, you can accurately model it using math (software like TA Instrument’s TRIOS, makes this process easier). Leverage this information back in the lab, and you often don’t need to discern the exact critical strain of a material. Once you know the LVR, you can stick within that threshold. Conversely, the analytical approach models the minuscule stress and strain data at the range’s bottom end, meaning you don’t need to waste lab time gathering that data.

LVR in the Real World: Top Industries & Applications

When you’re on the 60th floor of a skyscraper or swallowing a Vitamin D supplement, you rely on the predictable viscoelasticity of materials all around (and inside!) you. That’s why you will find LVR testing is crucial in a vast array of industries, including:

Polymer and Plastics: Both materials are in products we use every day (probably even every hour). Knowing when and how they fail–and, for sustainability purposes, how they will react when they’re recycled–requires determining their LVR in a lab setting. With knowledge of the LVR, temperature ramps can be performed on polymers, effectively characterizing glass transitions (softening points), mechanically properties through thermal transitions (melting, crystallization), and properties such as crosslink density (essential for cured materials and rubbers – UV curable materials, epoxy, etc.)

Pharmaceuticals and Food: Your body itself is a viscoelastic structure, and so are the methods and materials used to keep it at its healthiest. From the capsule of a pill to plant oil emulsions that could replace saturated fat–understanding a material’s properties makes for an overall better quality of life. The LVR can give knowledge of the yield stress of a therapeutic cream and therefore its shelf life, or similarly the yield stress of a yogurt.

Construction: Cement is a fantastic example of a viscoelastic material that changes states due to time and temperature. The building you are in – right now – has not collapsed because researchers know how durable and stable its materials are over time and under stress. The LVR can be an effective characterization tool for paints which help maximize building material lifetime (critical for combating mold, UV, humidity, corrosion), with the LVR again characterizing shelf stability through the yield stress. The LVR can also help characterize the durability of composite materials commonly used in flooring, ceilings, and benchtops.

Conclusion: Materials Innovation Starts in the Lab

The world simply works better because we understand (and can innovate) viscoelastic materials: From the soap that morphs into foam when pumped from a bottle to the way a vaccine exits a syringe. These advances, however trivial or monumental, only happen because of research in the lab. Just like you can’t sprint before learning to crawl, you can’t make your product safer, healthier, lighter, cheaper, or more durable without understanding its linear viscoelastic region. If viscoelastic materials are building blocks to a better world, then the LVR is a building block to creating better versions of those materials. Contact TA Instruments for expert guidance in testing and optimizing your materials.

Other Resources

Application Note – Determining the Linear Viscoelastic Region in Oscillatory Measurements
Application Note – Temperature and Frequency Trends of the Linear Viscoelastic Region
Application Note – Determining the Linear Viscoelastic Region in Creep and Stress Relaxation Tests
Tech Tip – Discussing the Linear Viscoelastic Region and Selecting a Strain Value
Webinar – Jan Vermant – Orthogonal Superposition Rheology
Webinar – Connecting Polymer Processing and Product Performance through Rheology & DMA on the New DHR
Contact – Contact TA Instruments Today

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3 Essential Types of Mechanical Testing for Polymer Development

Juli Varvarezis — Mon, 10 Jun 2024 18:59:20 +0000

3 Essential Types of Mechanical Testing for Polymer Development

Andy Simon | Morgan Ulrich
June 10, 2024

High-performance polymers are a critical material for manufacturers due to their combination of mechanical, thermal, and chemical properties, but especially their cost. Without adequate testing, manufacturers could run into a slew of issues, from immediate product failure to poor performance or failure after some time in usage. In this post, we review the three most important types of mechanical testing to better predict and ensure performance, safety and reliability.

As high-performance and technical industries innovate, so do the materials they use to build their products. A car company might have to design a specialized part to handle increased torque from an EV. An engineer might need to develop a novel storage solution for critical scientific cargo in a rocket headed to the International Space Station. No matter the goal, each component must perform safely, reliably, and predictably. Success requires a multi-faceted testing approach in the development stage, because the stakes could not be higher when a product reaches the real world (or leaves it).

Whether a new supplier is necessary because of lingering supply chain complexities after the COVID-19 pandemic, weight and cost reduction are required to innovate, or sustainability is mission critical, more and more industries around the globe–from aerospace to automotive to life sciences and beyond–have shifted toward one common materials solution: High-performance, synthetic polymers.

What Are High-Performance Polymers?

High-performance polymers are a category of chemically-produced substances such as polyamides, polyethylene, Teflon, and synthetic rubber. They offer numerous benefits, including reduced production costs and lower weight than historical engineering materials like steel and aluminum.

However, implementing any new material into your production process takes extensive lab time to answer two key questions: How does this material change over time? And how does this material respond to specific types of stress? Proactively answering these questions before launching your product isn’t just essential to your P&L. It’s also crucial to establish parameters for safe and reliable use.

Polymer Mechanical Testing Basics: Fatigue, Tensile and DMA

Here are three types of mechanical testing that measure polymer behavior–whether that polymer is headed through the grocery store parking lot or into low earth orbit.

Fatigue Testing

Polymers usually fail in one of two ways:

Over time from repeated use.
All at once under extreme stress.

Manufacturers almost always test number two, yet they frequently overlook number one. But plastics are actually more sensitive to failure over time. Which is why fatigue testing is critical in any high-performance product–it reproduces the conditions in which a material behaves tomorrow, next week, or in 10 years.

Fatigue testing ensures you know precisely how many “pulls” it takes to break a product or material. Specialized equipment, like Load Frame Instruments, replicates real-world conditions, using predetermined levels of force over and over until a failure occurs. This information can predict product endurance, optimize structural design, inform safety limits, or help determine durability.

Observing a material after its first or even 10th use might be relatively simple. But what about its 40,000th? Fatigue testing is the most accurate and timely way to answer that question before your product leaves R&D into the real world.

Tensile (Monotonic) Testing

What happens to a polymer under a single, powerful blow? How much force is required to break it? Tensile–or monotonic–testing gets the answer.

Data like this is necessary in its own right, but tensile testing provides even more valuable insight when combined with fatigue testing. An initial tensile test provides thresholds that can then repeat over thousands of cycles. An instrument like the ElectroForce 3200 can perform both by applying precise levels of force and then duplicating those levels – thousands or even millions of times.

That testing rigor provides a fuller understanding of a material’s weakness – from catastrophic failure to normal wear and tear. This means you will gain the insight needed to save both money and time during the pre- and post-production cycles. More importantly, you’ll also get information that can save lives.

Dynamic Mechanical Analysis (DMA)

Time and force are crucial variables in polymer research. But so is temperature. Dynamic Mechanical Analysis combines all three to measure three fundamental material properties:

Storage modulus: The stored energy (stiffness) of a material, and how that energy returns when it’s stretched and returns back into shape.
Loss modulus: The energy lost to heat from the materials’ viscous properties, also known as damping.
Glass transition: The temperature range in which a material changes from its rigid “glassy” state into a more rubbery, viscous state.

From testing the modulus difference between multiple samples of one polymer, understanding how a modulus changes across a temperature range, or finding the precise temperature ranges where a material loses its structural rigidity, DMA provides robust data with a wide range of applications. Quality control, product development, and product performance just to name a few.

Conclusion: Why You Need All Three

A complete understanding of a polymer’s behavior is not possible through any single form of mechanical testing. You might know how much force it takes to break a single sample. But what about when 50% of that force is applied 10,000 times? Or if that force is applied next to a running engine at midday?

Any one mechanical test–be it fatigue, tensile, or DMA–provides an incomplete picture. As more and more industries need to navigate the polymer development journey, only combining all three ensures they’re fully equipped to ensure they do it successfully. But with the proper tools and a rigorous testing process, polymers will continue to fuel innovation in industries worldwide.

Other Resources

eBook – Essential Polymer Material Analysis Techniques for Scientists, Researchers, and Engineers
Blog – How Sustainable Polymer Development is Supported by Dynamic Mechanical Analysis
Application Note – Flexural Fatigue Behavior of Woven Fiberglass Composites at Elevated Temperature
Application Note – Tensile and Fatigue Properties of Additively Manufactured Polyamides
Application Note – Evaluation Of The Loss Of Polymer Strength And Durability Due To Fatigue Loading And Manufacturing Artifacts

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Characterization Considerations when Sourcing PCR

Juli Varvarezis — Wed, 08 May 2024 18:24:28 +0000

Characterization Considerations when Sourcing PCR

Julienne Regele | Morgan Ulrich
May 8, 2023

Against the backdrop of a plastic waste crisis, the global demand for plastic is set to quadruple by 2060.¹ This has driven a shift toward sustainability and away from linear use models of plastic production. Post-consumer resin (PCR) has emerged as a key player in circular economy initiatives, though ensuring the quality and performance of PCR requires several characterization considerations.

This article explores the intricacies of PCR, challenges in processing, and techniques to verify its suitability for various applications.

Understanding PCR

PCR represents a group of plastics that have fulfilled their intended purpose and undergone a process of collection, cleaning, and re-pelletization for reuse. Reincorporating PCR into new products and packaging is crucial for circularity. By closing the loop of plastic consumption, the industry is able to reduce the demand for virgin resources and minimize the environmental impact caused by pollution and extracting natural resources.
Similar though distinct materials include post-industrial resin (PIR) and rework. The former consists of resins that have undergone conversion into a product deemed either out-of-specification or unsalable and, therefore, has never reached the end customer or consumer. Rework relates to waste generated within a manufacturing process that is subsequently reused within the same process instead of being sold to another manufacturer.

Material Characterization Considerations

Material Purity

In contrast to virgin resins, PCR feedstocks exhibit greater complexity and substantial variability due to their diverse origin. Despite advancements in sorting technology, this diverse origin can present significant challenges for processing engineers, such as the risk of contamination.

Differential scanning calorimetry (DSC) can play a role in testing the purity of PCR by scanning for unidentified peaks within the material. These peaks can be compared to reference polymers, enabling the determination of the composition and purity of the PCR sample. This method facilitates the detection of contaminants or impurities, supporting batch-to-batch quality control efforts and ensuring the integrity of the recycled material.²

Material Behavior

As mentioned above, PCR obtained from various sources can exhibit heterogeneity. This can extend beyond impurities to variations in molecular weight and molecular weight distribution, leading to inconsistencies in crystallinity, crystal melting behavior, and resin melt viscosity across different batches.²

DSC
DSC enables precise assessments of PCRs’ crystallinity and crystal melts, which is necessary information for determining the appropriate processing temperature and cooling rates during manufacturing processes such as extrusion or injection molding.

By reporting on glass transition temperature (Tg), DSC provides essential data for understanding the material’s mechanical and thermal behavior during processing and in the final product. By correlating crystallinity data from DSC with Tg, manufacturers can optimize processing parameters to ensure efficient production and the desired material properties in PCR-based products. Additionally, Waters | TA Instruments’ DSC has the capability to implement Guided Methods, which walks new users through experiments like this with step by step instructions.

For those handling multiple samples, TA Instruments’ Discovery X3 DSC is ideal. This model incorporates a multi-sample cell capable of providing high-quality heat flow data for three samples concurrently.^2,3

Rheometry
Rotational rheometry can be used to obtain information on how the molecular structure of PCR feedstocks impacts processing characteristics. Through measuring melt viscosity over time and temperature, rheological analysis facilitates the evaluation of thermal stability at processing temperatures and the optimization of processing conditions.²

The ARES-G2 and Discovery Hybrid Rheometers (DHR) from TA Instruments offer advanced capabilities for assessing the rheology of PCR polymers. The ARES-G2 provides unparalleled data accuracy through separate motor and transducer technology (SMT) and precise temperature control, optimizing material processability and defining critical quality attributes (CQAs).

The DHR, on the other hand, offers unmatched performance, ease of use, and versatility.Regardless of the desired stress, shearing or oscillating force, or deformation, the DHR is a keystone instrument for top laboratories worldwide. With intuitive designs and an integrated Dynamic Mechanical Analysis (DMA) mode, these rheometers support advancements in materials science and product development.^4,5

Material Performance

The variety of plastics present in PCR poses significant challenges for secondhand processing in value-added applications. Variety introduces incompatibility of blends, leading to undesirable mechanical properties and impacting the rheology and dynamics of the plastic. These factors are crucial in determining the material’s viability for use in manufacturing processes and its suitability for specific applications. To enhance compatibility and stabilize the morphology of PCR, compatibilizers like block co-polymers, carbon nanotubes, and silica nanoparticles are added.⁶

Throughout their lifespan and reprocessing cycles, recycled plastics also experience degradation, characterized by a reduction in molecular length.⁷ Accordingly, there is typically a trade-off that needs to be assessed when incorporating recycled content into virgin plastics.

Dynamic Mechanical Analysis (DMA) proves highly effective in evaluating the thermal and mechanical attributes of solid polymer samples. This technique facilitates the characterization of a material’s viscoelastic properties, including storage modulus, loss modulus, and tan δ, aiding in evaluating the ultimate performance characteristics of solid products and their correlation with material chemistry. DMA also stands out as one of the most sensitive methods for determining a material’s glass transition temperature, valuable for quality control, development, guiding processing conditions, and diagnosing product failures.⁸

Mechanical testing of polymers in end applications, including test techniques like fatigue, creep, and bending, can be performed using TA Instruments’ suite of ElectroForce instruments. These machines are specifically crafted for ultra-durable and high-precision testing to provide outstanding force capacity, speed, precision, and accuracy.⁹

Building a Greener Future with PCR

The utilization of PCR underscores a pivotal paradigm shift towards sustainable plastic development. As the imperative to combat plastic waste intensifies, embracing PCR emerges as a pragmatic solution for realizing a greener future. Through the application of proper characterization techniques such as DSC, rheometers, and mechanical testing, stakeholders can navigate the complexities of material selection and uphold stringent quality standards, thereby advancing the integration of PCR into mainstream manufacturing processes.

Leveraging TA Instruments’ cutting-edge products tailored to the unique demands of PCR characterization, the industry can catalyze transformative change and chart a course toward a more sustainable and resilient future.

To learn more about these instruments, contact TA Instruments’ material characterization experts today.

References and Further Reading

Smith, P., et al. (2024). A data-driven analysis of HDPE post-consumer recyclate for sustainable bottle packaging. Resources, Conservation & Recycling. doi.org/10.1016/j.resconrec.2024.107538
TA Instruments. [Online] RH122: Using Rheology and Thermal Analysis to Help Optimize Processing Conditions of Recycled PET. Available at: https://www.tainstruments.com/pdf/literature/RH122.pdf
TA Instruments. [Online] Multi-Sample X3 DSC. Available at: https://www.tainstruments.com/x3-dsc/ (Accessed on 29 March 2024).
TA Instruments. [Online] ARES-G2. Available at: https://www.tainstruments.com/ares-g2/ (Accessed on 29 March 2024).
TA Instruments. [Online] Discovery Hybrid Rheometers. Available at: https://www.tainstruments.com/products/rheology/discovery-hybrid-rheometers/ (Accessed on 29 March 2024).
Muzata, T.S., et al. (2024). Challenges in the mechanical recycling and upcycling of mixed postconsumer recovered plastics (PCR): A review. Current Research in Green and Sustainable Chemistry. doi.org/10.1016/j.crgsc.2024.100407
Hinczica, J., et al. (2022). Influence of Recyclates on Mechanical Properties and Lifetime Performance of Polypropylene Materials. Procedia Structural Integrity. doi.org/10.1016/j.prostr.2022.12.017
TA Instruments. [Online] Introduction to Dynamic Mechanical Analysis and its Application to Testing of Polymer Solids. Available at: https://www.tainstruments.com/applications-notes/introduction-to-dynamic-mechanical-analysis-and-its-application-to-testing-of-polymer-solids/ (Accessed on 29 March 2024).
TA Instruments. [Online] ElectroForce Mechanical Test Instruments. Available at: https://www.tainstruments.com/products/electroforce-mechanical-testers/ (Accessed on 29 March 2024).

Other Resources

Blog – How Sustainable Polymer Development is Supported by Dynamic Mechanical Analysis
Blog – 3 Time-Saving Techniques for Your Polymer Research
Blog – Material Analysis for Bioplastics Quality Assurance and Degradation
eBook – Essential Polymer Material Analysis Techniques for Scientists, Researchers, and Engineers
Webinar – Compatibilizers for Mechanical Recycling
Webinar – Developments in Advanced Recycling
Application Note – Characterization of Bio-Derived Polymer Under Controlled Humidity
Application Note – Using Rheology and Thermal Analysis to Help Optimize Processing Conditions of Recycled PET
Application Note – Comparison of the Thermal Behavior of Different Types of Recycled PET for Advanced Honeycomb Structures
Case Study – A Greener Approach to Polymers

The post Characterization Considerations when Sourcing PCR first appeared on TA仪器.

4 Polymer Insights from Dynamic Mechanical Analysis

Juli Varvarezis — Tue, 12 Dec 2023 20:00:33 +0000

4 Polymer Insights from Dynamic Mechanical Analysis

How DMA can make your fatigue testing more efficient

Morgan Ulrich | Andy Simon
December 12, 2023

From material selection and failure analysis to end-use application, Dynamic Mechanical Analysis (DMA) offers crucial polymer insights. Polymer scientists and design engineers pair DMA with fatigue testing to gain a complete view of their material’s properties and performance attributes.

What is Dynamic Mechanical Analysis?

Dynamic Mechanical Analysis (DMA) measures a material’s modulus, damping, and glass transition as the material is deformed under a periodic stress. DMA is particularly useful for evaluating polymeric materials that exhibit time, frequency, and temperature effects on mechanical properties because of their viscoelastic nature.¹

DMA measures two kinds of modulus: Storage modulus is a material’s stored energy or elasticity; when you pull the material, it returns the energy and moves back into shape. Loss modulus is a material’s energy that is lost to heat; this is also known as viscous or damping properties.

DMA also measures glass transition (Tg), the temperature range in which a polymer changes from a hard “glassy” material to a softer, rubbery material with more viscous properties.² This is useful information for designing processing conditions, predicting product performance, and ensuring quality control.

Four Polymer Insights from DMA

Difference in Modulus

DMA efficiently and accurately measures the modulus of a polymer, offering quick comparisons of different samples’ stiffness. While modulus is usually included in a material’s data sheet, running DMA tests allows polymer labs to verify their material’s modulus under specific conditions and draw accurate comparisons between samples.

Change in Modulus

DMA can measure how your material’s stiffness changes as a sample is heated or cooled from room temperature to the temperature of interest. Tracking changes in modulus is especially useful for quickly evaluating the influence of temperature on your materials, especially in a temperature range of interest which can help identify where to focus other mechanical tests such as fatigue studies.

Approaching Transitions

DMA is useful for tracking overall material properties as you approach a temperature of interest, such as an application-specific temperature range or potential failure temperatures. Even if you know that a material’s glass transition is at 145° C, how does it change up until that transition? Mapping the temperatures that impact your material beyond simple failure or transition temperatures offers a much more accurate and complete picture of material behavior.

Deeper Insights than Manufacturer’s Operating Ratings

While manufacturers offer suggested temperature ranges for use, those ranges often overlook more subtle changes that take place in the material. In the example below, the manufacturer’s operating rating is 130°. However, the material is clearly changing well below that temperature rating, meaning significant effects on strength and fatigue life are likely, but the exact effect is not possible to predict from DMA data alone.

Upon seeing the change in loss modulus well below the temperature rating, researchers were able to zero in on a temperature range where the material is changing and focus their effort in that range. They decided to perform a fatigue test at 100° C to evaluate the effect of the increased temperature on the fatigue life. Their fatigue testing data revealed that at 100° C, the material had a 90% reduction in fatigue life. DMA highlighted that the manufacturer’s rating was incomplete, and fatigue data completed the picture with a more accurate understanding of the material at “approved” temperatures.

Combining DMA and Fatigue for the Complete Picture

As the example above illustrates, DMA data can effectively inform fatigue testing to offer the complete picture of polymer performance. DMA offers deeper insights into material behavior that may be oversimplified in operating ratings and on data sheets. Learn more about fatigue testing and see the rest of the fatigue data for this sample in the TA application note “Flexural Fatigue Behavior of Woven Fiberglass Composites at Elevated Temperature.”

References:

Introduction to Dynamic Mechanical Analysis and its Application to Testing of Polymer Solids – TA Instruments. https://www.tainstruments.com/applications-notes/introduction-to-dynamic-mechanical-analysis-and-its-application-to-testing-of-polymer-solids/
Measurement of Glass Transition Temperatures by Dynamic Mechanical Analysis and Rheology – TA Instruments. https://www.tainstruments.com/applications-notes/measurement-of-glass-transition-temperatures-by-dynamic-mechanical-analysis-and-rheology/

Other Resources

Blog – What is Dynamic Mechanical Analysis?
Blog – How Sustainable Polymer Development is Supported by Dynamic Mechanical Analysis
Blog – 3 Time-Saving Techniques for Your Polymer Research
Webinar – Fingerprinting recycled thermoplastic resins for process optimisation
Webinar – Connecting Polymer Processing and Product Performance through Rheology & DMA on the New DHR
Application Note – Evaluation Of The Loss Of Polymer Strength And Durability Due To Fatigue Loading And Manufacturing Artifacts
Application Note – Tensile and Fatigue Properties of Additively Manufactured Polyamides
Application Note – Flexural Fatigue Behavior of Woven Fiberglass Composites at Elevated Temperature
Application Note – Characterization of Bio-Derived Polymer Under Controlled Humidity

The post 4 Polymer Insights from Dynamic Mechanical Analysis first appeared on TA仪器.

用于聚合物研究的 3 个省时技巧

Sam Barnes — Thu, 09 Mar 2023 12:18:52 +0000

用于聚合物研究的 3 个省时技巧

Kim Anderson | Alina Latshaw | Neil Demarse | Morgan Ulrich
February 28, 2023

节省聚合物研究的时间存在多种益处，可通过不同的方式实现，包括减少操作员操作适应时间、提高研究通量以及获得准确和可重复的结果。此处的 3 种技术（流变、TGA 和 DSC）所提供的解决方案是可节省聚合物研究时间的 3 个机会。

1. 在流变工作流程中实施自动修边技术

聚合物熔体流变可用于对影响加工质量（如挤出和成型部件）的分子结构进行指纹图谱分析。根据制造工艺的不同，材料可能会在不同的时间段内经历多个温度和加工速度，因此，早期预测聚合物的熔体行为以优化加工条件至关重要。优化可能涉及将聚合物在等温条件下保持特定时间或提高温度，以提高聚合物注入模具时的流动性。

聚合物熔体流变的常用设置是平行板夹具。与测试低粘度材料（如油和液体）时常用的锥体夹具不同，平行板夹具样品内的速度梯度在外边缘处最大。这意味着仪器和数据所测得的扭矩大部分代表了该边缘的测量值。为获得准确和可重复的结果，用户必须持续去除多余的样品（称为 “修边”）以防止边缘效应。

自动修边技术消除了与用户错误和多用户不一致性相关的多种差异根源。该技术的应用可将测量的一致性、可重复性和准确性提高达 5 倍，同时可将无人值守时间增加 80%，并可将新操作员的操作适应时间降至不到 30 分钟。

阅读技术简介 – 聚合物熔体流变工作流程自动化：流变仪的自动修边

2. 使用 TGA 测试聚合物寿命作为烘箱老化测试的替代方法

ANSI/ASTM 程序 D-2307 是估算电线绝缘寿命的常用测试。在该程序中，双绞绝缘线在高温（最高 240℃）下进行烘烤老化（长达 50 天），直到发生电压击穿。

该程序虽然有用，但非常耗时，通常需要几个月的时间，对于高稳定性材料而言尤其如此。随着越来越多的稳定的聚合物电气绝缘材料的出现，全套测试所需的时间变得过于冗长。

热重分析 (TGA) 可监测材料随温度变化的重量变化，提供了一种可替代烤箱老化的测试方案。评估一种材料的总时间不到一天，使用自动 TGA 时的人员实际操作时间更短，可进行通宵评估。

阅读完整的研究 – 通过 TGA 分解动力学估计聚合物寿命

3. 同时分析半结晶 PET 热塑性塑料

差示扫描量热仪 (DSC) 技术是了解材料热性能和形态的关键工具。聚对苯二甲酸乙二醇酯 (PET) 是一种普遍存在的半结晶热塑性聚合物的示例。影响 PET 材料特性的关键因素之一是结晶度百分比，可通过热加工条件对结晶度百分比进行控制。

在相同的条件下同时研究 PET 样品，可实现在同等条件下对样品进行直接比较，并可确定作为热历史函数的热性能差异。并行运行样品有可能提高研究通量、减少运行时间并提高实验室的整体效率。

阅读完整的研究 – 使用 X3 DSC 进行半结晶热塑性分析

欲了解更多信息或提交产品查询，请访问我们的联系页面。

其他资源

Application Note – Polymer Melt Rheology Workflow Automation: Auto-Trim for Rheometers
Application Note – Estimation of Polymer Lifetime by TGA Decomposition Kinetics
Application Note – Semi-Crystalline Thermoplastic Analysis using an X3 DSC
Product: Auto-Trim Accessory
Technique – Rheology
Application – Polymers

The post 用于聚合物研究的 3 个省时技巧 first appeared on TA仪器.

如何利用流变改进增材制造（3D 打印）技术

Sam Barnes — Thu, 02 Feb 2023 12:41:42 +0000

如何利用流变改进增材制造（3D 打印）技术

表征聚合物以有效制造产品

Morgan Ulrich | Corinna Johannisson
January 25, 2023

成功的增材制造产品取决于材料的特性和行为。流变可为安全、高效和可重现的聚合物制造提供有价值的信息。

3D printing and other additive manufacturing processes can be optimized using rheological analysis. Rheology also applies to numerous other manufacturing processes.

聚合物产品无处不在，从包装薄膜、酸奶杯到复杂的汽车零件均使用聚合物产品。尽管应用广泛，但塑料产品通常均通过相同的简单步骤进行制造：

制造的起始步骤是应用聚合物基材料（通常为颗粒或粉末形式）
加热材料以形成自由流动的熔体
通过吹膜、注塑成型、挤出或增材制造（3D 打印）等工艺实现熔化材料的成型
冷却并凝固产品

终产品的特性和物理形态在很大程度上取决于其加工过程。制造商需要深入了解他们的材料和应用，以达到预期的终产品质量。在加工过程中了解材料是可能的，但这会导致更大的材料损失和更高的生产成本。

如果在加工前以实验室规模进行材料表征，则表征会更为有效并且会提高最终的生产率。然后，制造商可根据材料的测量特性设计加工条件。

制造商和研究人员都利用流变来研究材料的变形和流动。流变可提供有关液体和固体材料的关键、精确的见解，为成功的增材制造提供信息。

质量控制挑战

虽然增材制造为高效率和独特形状产品的制造提供了新机会，但在创造完美产品的过程中仍存在多种障碍。

在增材制造过程中，聚合物被熔化到熔融状态并通过 3D 打印机的管线和喷嘴挤出。因此，聚合物必须能够自由流动，并且需要具有尽可能低的黏度。同时，聚合物必须在挤出后立即保持其形状，并且在冷却过程中不能出现变形。Waters – TA Instruments 的应用专家 Lukas Schwab 指出，3D 打印中使用的材料需要在黏度（液体流动性特征）和固体弹性之间实现精确的平衡。

3D 打印涉及通过狭窄的模具压制聚合物。可能会发生一种称为“线性膨胀”的现象，即在出模后，聚合物股线直径与成型模具直径相比略有增加。可应用流变仪检测直径变化的程度。预测和测量线性膨胀有助于制造商确保其 3D 打印产品的精度。

将回收材料用于打印产品对聚合物制造商提出了另一个挑战。废旧塑料通常含有残留添加剂、颜色和填料，它们会影响熔体的质量、可加工性及其在制造过程中的行为。因此，再生塑料的加工及其终产品可能难以预测。因此，需要对生物塑料进行详细的分析。

预先质量控制

尽管存在这些潜在的干扰和不确定性，制造商仍然可以执行强有力的预先产品控制和质量保证。其中的关键是分析性思考的两个角度：

产品中使用的所有材料成分的相互作用
必要的工艺参数，包括温度、压力和流量

Waters 的应用和支持专家 Marco Coletti 在他的网络研讨会上解释了如何借助流变研究来优化 3D 打印和增材制造工艺。

轻松表征材料

Lukas Schwab 解释说，使用相应的功能强大的高精度流变仪可确定流变特性，这是材料表征的重要组成部分。

Waters 的应用专家表示：“特别是在应用聚合物熔体等液态物质的情况下，如果没有足够的仪器，了解和预测流变特性可能会非常耗时。” 样品行为通常会根据作用于样品上的力的大小而发生变化，这意味着“样品的流动和变形行为只能通过实验模糊地预测，或通过流变进行更为精确的测量。”

A look into the heart of an HR rheometer: The viscoelasticity of polymers can be checked easily, safely and reliably. Manufacturing processes, including 3D printing, can be optimized on a laboratory scale for the ideal production result.

3D 打印的关键流变测量

Discovery 混合流变仪 (DHR) 是用于流变的多功能分析平台。该仪器配置了最新的专利技术并且极为人性化，可以很容易地测量直接张力、变形控制以及轴向力规格。

通过应用流变仪完成流变测量。流变仪测量材料（液体或固体）在受力时的变形。应力、变形和剪切行为的结合构成了流变、材料变形科学的基础。

进行旋转流变测量时，将样品放置在两个圆板之间的圆筒中并将圆板和样品压在一起。例如，之后可按规定的速度和方向旋转其中的一个圆板。Lukas Schwab 解释说：“旋转测量是确定材料黏度的合适方法，该方法可确定如在 3D 打印中的泵送和加工能力。”

相比之下，振荡测量（两个圆板中的一个以小振幅正弦方式来回移动）可提供有关样品平衡结构的更多信息，因此更多地用于确定材料的特性。振荡测量有助于解答不同产品批次的分子量或材料在较低力量作用下的行为等问题。

通常借助流变测量法来确定材料的黏度或黏弹性，Lukas Schwab 总结道：“黏度是对内部摩擦引起的流动阻力的测量，其测量值取决于系统的微观特性，如粒径。反之，黏弹性是材料对变形力所作反应的特性的测量。就纯弹性材料而言，对其施加负载后不会耗散能量；反之，黏弹性材料由于材料变形，其应力-应变行为的效应存在一定程度的差异（滞后效应）。”

Lukas Schwab 解释说：在许多生产过程中将流变测量用作质量控制的方法，因为不良的黏弹性行为会导致材料性能不佳和变脆。黏弹性也可用于确定固体的耐久性和热机械分解行为。

测量所有必要的特性（黏度、分子量、材料行为和黏弹性）可能看起来令人生畏，但 Discovery 混合流变仪具有独特的能力，能够以行业领先的准确性和易用性提供熔融或固体聚合物材料的完整图像。

请访问我们的聚合物应用页面，以了解更多的有关可持续、高效聚合物生产的其他类型的材料分析。同时请联系 TA Instruments，与聚合物材料分析专家取得联系。

其他资源

Webinar – Improving Li-ion Battery Technology through Advanced Material Analysis
Webinar – Unlock a New Dimension in your Battery Research Through Isothermal Microcalorimetry
Webinar – Applications for Isothermal Heat Flow Calorimetry – Lithium Ion Battery Chemistry
Webinar – Enhanced Understanding of Lithium ion Battery Chemistry Through Isothermal Calorimetry
Application Note – Investigations into Dry Cell Battery Discharge Rates Using TAM Air
Application Note – The Impact of Electrolyte Additives in Lithium-ion Batteries Determined Using Isothermal Microcalorimetry
Application Note – Microcalorimetry for studying the electrolyte stability of lithium/manganese dioxide batteries

The post 如何利用流变改进增材制造（3D 打印）技术 first appeared on TA仪器.

经济且高效地升级实验室仪器的 4 种方法

Sam Barnes — Mon, 19 Sep 2022 12:25:30 +0000

经济且高效地升级实验室仪器的 4 种方法

Sarah Cotts | Stephanie Keller | Morgan Ulrich
September 19, 2022

技术的发展日新月异。无论您是升级旧设备还是为您的工作台添加新技术，使用尖端仪器都一定会提高您实验室的效率和成果。新型仪器可提供更可靠的数据和更先进的功能，这对于始终立足于材料创新前沿而言至关重要。

但是，如何在升级仪器以获得最佳投资回报的同时最大限度地减少停机时间呢？以下是可让您无缝且轻松地升级实验室的 4 种方法。

1. 以旧换新

用最新型号的仪器更换服务多年的老旧仪器是改善实验室结果的最简单的方法之一。更好的消息是，您可以用旧仪器换取升级折扣。

2000 年推出的 TA Instruments Q 系列热分析仪彻底革新了测量方法，Discovery 系列以其改进的测量和易用性延续了品牌传统。用户可对其 Q 系列 DSC、TGA、DMA、SDT、TMA 仪器或竞争型号仪器进行以旧换新，以节省购买新的 Discovery 系列热分析仪的费用。Discovery 系列提供无与伦比的灵敏度和准确性，可检测样品中的最小变化，并通过强大的 TRIOS 软件提供革命性的用户体验。点击此处以解更多信息并联系我们以对您的热分析仪进行以旧换新。

同样，您可以对 TA Instruments AR 流变仪或竞争型号仪器进行以旧换新，以节省购买新的 Discovery 混合流变仪的费用。升级到 DHR 实现了卓越的功能改进 – 由于 DHR 优异的扭矩灵敏度，用户可使用更少的样品测量更低的黏度和更小的应力。该仪器的混合功能是游戏规则的改变者：可在一台含集成线性 DMA 的流变仪上进行剪切流变学、黏性/剥离、拉伸黏度测量，以及张力、弯曲和压缩测量。DHR 广泛的功能和配件（包括与许多 AR 配件的兼容性）可为您实验室未来可能需要的任何测量提供保障。联系我们以了解有关流变仪以旧换新的更多信息。

除节省成本外，对您的热分析仪或流变仪进行以旧换新也非常易于操作且回报丰厚：

通过承接已有的历史数据和操作程序实现平稳过渡
使用新的“无人值守”自动进样器减少瓶颈（可在特定的热分析仪型号上使用）
借助专为每个用户级别的易用性而构建的 TRIOS 软件，最大限度地减少操作适应时间
通过可靠的结果和更高的准确性提高数据可信度
通过新功能和测量选项扩展实验室能力

2. 租用新仪器

您是否知道租用新仪器比租用汽车更容易？Waters Capital 为 TA Instruments 提供灵活的租用选项和优惠价格。租用仪器可让您：

通过可预测的每月付款来扩展您的预算
无需预付金即可在需要时立即采用新技术
根据每月付款金额与大量初始投资加速您的投资回报率（ROI）
购买前试用最新的仪器

租用可避免预算超支，无需直接购买即可使用新仪器。如果您需要一项技术的时长有限，您可通过仅租用与工作相关的技术来节省大量的开支。或者，如果您决定保留该仪器，您所有的租用付款都将计入最终的购买价格。无论您选择哪种方式，租用都可让您在受益于最新技术的同时节省重要的资本。点击此处以了解有关租用新仪器的更多信息。

3. 通过资助配套项目使您的资金翻倍

学术和政府实验室，请不要错过该项目！我们重视您对研究和教育的贡献，我们希望可帮助您的实验室取得更多的成就。我们的学术资助配套项目为我们的全新仪器提供仅限于学术用途的特殊定价，以确保您能够使用最先进的设备。

我们可靠耐用的仪器为各种经验水平的用户设计。从任期最长的教授到刚入校的新生，都可以轻松设置和运行测量。

希望保护您的投资并节省耗材和维修？我们的学术支持计划旨在降低拥有成本并最大限度地延长正常运行时间和产品寿命。该计划包括用品和消耗品折扣，以及我们定期安排的免学费的理论和应用培训课程。

单击此处以了解更多信息并联系我们以获取报价。

4. 关注以获得提示和销售信息

您最大限度地利用您的仪器吗？您是否了解新的促销和升级？

关注 TA Instruments 的 LinkedIn、 Facebook 和 Twitter，以获取有关优惠、新产品和仪器使用技巧的频繁更新信息。在您购买之前，请查看 TA Instruments 当前的促销活动，以了解是否有您需要的设备的优惠。

无论您何时购买，我们的销售代表都会通知您任何相关的促销活动，并帮助您选择适合您需求的技术。请联系 TA Instruments 销售代表，以确保为您的实验室采购最好的仪器。

其他资源

The post 经济且高效地升级实验室仪器的 4 种方法 first appeared on TA仪器.

水凝胶流变学

Super Admin — Thu, 30 Jun 2022 13:30:03 +0000

Rheology of Hydrogels

Sarah Cotts | Morgan Ulrich
June 20, 2022

水凝胶的表征与应用

水凝胶为三维多孔隙结构，能够吸收大量的水分。水凝胶可由聚合物、蛋白质、多肽、胶体、表面活性剂或者脂类物质产生。¹ 水凝胶具有超强的吸水能力，因此可应用于许多生物学领域，包括药物递送和组织工程。吸收水分后水凝胶的性质会发生改变，因此科学家们需要准确表征水凝胶在不同水饱和度以及在变化条件下的行为特性。

天然形成水凝胶的一个示例是胶原蛋白，它是人体主要的结构蛋白。胶原蛋白具有纤维特性，因此是构建组织结构的理想材料。胶原蛋白分子以长纤维的形式紧密排布在一起，而且某种确切的结构排布可以产生拉伸强度与钢相似但具有一定柔韧性的原纤维。

胶原蛋白非凡的结构特性和生物相容性使其成为一种使用广泛的材料，特别是用于组织工程中的基础框架材料。² 胶原蛋白是一种天然材料，其质量在不同的样品间存在差异。因此，以胶原蛋白为基础材料制造具有一致性能的产品往往存在挑战性。但是，天然起始原料所固有的差异性难题并非不可战胜，我们需要的仅仅是进行正确的材料性能测试，以预测材料在最终应用中的
行为。

在本博客中，我们将使用胶原蛋白作为对水凝胶进行表征的主要示例。但是，同样的技术也可应用于任何材料来源的任何水凝胶。

水凝胶流变学

流变学是衡量液体和固体的流动和变形行为的学科，是研究如胶原蛋白等水凝胶的一个理想方法。水凝胶具有固有的粘弹性质，也就是说，它们可同时表现出粘性行为和弹性行为。动态（振荡）流变学可对这些复杂材料进行表征，并给出粘弹性的定量测量报告：

储能模量：使样品发生扭曲需要施加的能量
损耗模量：材料变形后恢复其原有形状时所损失的能量
损耗角正切：损耗模量与储能模量的比值，该指标用于测量水凝胶的阻尼能力

在试图了解不同水凝胶样品在交联度、玻璃化转变、异质性和分子量方面存在的差异以及这些差异如何影响最终的使用性能时，对这些粘弹性指标进行测量至关重要。1 流变仪可轻松测量粘弹性，是优化上述特性的理想工具。

另一个重要指标是屈服应力，该指标对于衡量水凝胶也很关键。很多水凝胶均为可注射性材料，而屈服应力之所以重要的原因是，该指标决定了在注射点保留水凝胶的程度。剪切响应也决定了水凝胶溶液在注射时的难易程度。

不同的胶原蛋白起始材料可以具有非常不同的物理和热学性质，研究者们需要在实际应用条件下对胶原蛋白进行详细表征，以选择用于特定用途的最佳材料。³ 流变学测试设备的快速筛选能力使得胶原蛋白的工业生产既高效又具有成本效益。

选择最佳水凝胶流变仪

进行高质量、可重复的流变学测量需要使用合适的测试设备。TA Instruments 在设计和生产材料特性的测试系统领域（包括流变学）位于全球领先地位。

我们的标志性流变仪Discovery 混合流变仪（DHR）是行业领先的流变学测量仪器。DHR 便于使用，测试范围广泛，可以执行对表征水凝胶至关重要的多种标准和高级分析测量。

Discovery 混合流变仪 (HR)

Discovery 混合流变仪可通过多种标准操作程序对胶原蛋白水凝胶进行质量控制，包括粘弹性评估，以及评估在哪些压力条件下变形水凝胶的弹性开始消失。⁴该项评估对水凝胶而言尤其重要，因为在很低的应变百分数下表现出此类粘弹性的样品将不适用于制备终产品。Discovery 混合流变仪使得快速筛选出最适合于特定医疗应用的候选材料成为了可能。

Discovery 混合流变仪的设计目的是在简单和高级测量中均易于使用。仪器与 TRIOS AutoPilot 软件也是兼容的，可以创建自动化常规程序，包括测量、分析和生成报告。对于时间是其关键考量因素的工业生产而言，该软件可加速决策制定进程并缩短新用户的培训时间。

对于流变学测量，Discovery 混合流变仪拥有多个温度系统和温度室，包括一个相对湿度系统，该系统可用于在不同环境条件下测量吸湿性水凝胶。

Discovery 混合流变仪能够在同一台仪器上以不同的温度控制条件执行旋转流变学和线性动态力学分析。Discovery 混合流变仪拥有出色的灵敏度，因此可以测量多种硬度的材料，包括钢以及较柔韧的胶原蛋白。

欲了解更多的有关水凝胶的流变学评估，请阅读我们新列出的水凝胶流变学应用说明（rheology of hydrogels application note）。只需拨打电话或点击联系我们（contact us）即可获得个性化解决方案和专家建议，并了解 TA Instruments 流变仪可如何帮助您在处理复杂生物材料时提高效率和质量控制。

参考文献:

Baby, D. K. (2020). Chapter 9 – Rheology of hydrogels. In Rheology of Polymer Blends and Nanocomposites. Elsevier Inc. https://doi.org/10.1016/B978-0-12-816957-5.00009-4
Dong, C., & Lv, Y. (2016). Application of Collagen Scaffold in Tissue Engineering: Recent Advances and New Perspectives. Polymers, 8(42), 1–20. https://doi.org/10.3390/polym8020042
Meyer, M. (2019). Processing of collagen based biomaterials and the resulting materials properties. BioMedical Engineering OnLine, 18(24), 1–74. https://doi.org/10.1186/s12938-019-0647-0
Perez-Puyana, V. et al. (2020). Fabrication and Characterization of Hydrogels Based on Gelatinised Collagen with Potential Application in Tissue Engineering. Polymers, 12(5):1146. https://doi.org/10.3390/polym12051146

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如何通过热分析优化 3D 打印材料

Super Admin — Mon, 30 May 2022 02:55:08 +0000

如何通过热分析优化 3D 打印材料

Jason Saienga | Gray Slough | Morgan Ulrich
May 30, 2022

3D 打印也称为增材制造，许多行业都将其视为一种多功能制造技术。3D 打印可以实现快速成型和按需打印服务，以避免批量运行带来的潜在浪费。

3D 打印拥有创造复杂形状的独特能力，被广泛应用于制造业。许多标准制造方法无法在结构中产生空腔和底切。添加模式可以轻松创造各类独特形状。

3D 打印目前已扩展到一系列材料，包括生物相容性聚合物和各类金属。3D 打印甚至被用于医疗保健等领域，用于定制打印医疗设备。¹

为了优化 3D 打印材料，制造商需要仔细考虑最终材料的机械和热性能。虽然 3D 打印部件往往很轻，而且聚合物部件的正确组合可以拥有与金属相似的抗拉强度，但克服增材制造部件较低的机械和热性能是最大的挑战之一。²

3D 打印产品性能的工艺优化

了解挤压过程如何影响打印材料的最终性能是一个非常热门的研究领域。汽车应用对材料的拉伸和热性能要求最高。

幸好，目前有许多含有碳纤维、玻璃纤维和凯夫拉纤维的热塑性聚合物基质可用于 3D 打印部件，并能够在汽车应用中充分实现高性能。²

在 3D 打印过程中，要打印的基材被熔化，然后分层沉积以创建最终对象。在此过程中有多个参数可以优化，例如聚合物床层和喷嘴温度以及层间固化时间。

3D 打印有多种方法，包括选择性激光烧结、生物打印和熔融沉积建模。熔融沉积建模是最常用的方法。

玻璃态转化温度是选择正确温度挤压非晶态聚合物的必要信息。对于半结晶聚合物，其熔化温度是应重点关注的数值。结晶度强烈影响聚合物的机械性能。

许多聚合物用紫外线固化，紫外线在聚合物材料中产生自由基，作为最终聚合物生产中交联过程的引发剂。交联程度越高，材料的硬度和强度就越高。通过改变样品暴露在紫外线下的时间长度可以影响交联的材料强度。

温度和固化时间都会影响聚合物在材料中的分子结构及其性能。因此，为了优化这些参数并探索其对最终材料的影响，材料设计师使用对聚合物性能细节敏感的测试技术。

3D 打印材料的热分析

用于研究挤压过程对最终材料性能影响的主要热分析工具包括热重分析 (TGA)、差示扫描量热分析 (DSC)、热机械分析 (TMA)和动态机械分析(DMA)。³ 每种技术都提供一些互补信息，可以将这些信息结合起来，以便人们对打印材料的性能有更深的了解。

热重分析测量材料重量随温度或时间变化的幅度和变化率。TGA 对于了解表征挤压的影响非常重要，因为许多材料在加热时会发生氧化或分解，从而导致重量变化。⁴热重分析是确定样品在挤压过程中是否发生降解的最佳方法之一。

差示扫描量热法是一种强大的技术，用于测量材料放热和吸热转变与温度的函数关系 – 挤压过程的常见关注点包括玻璃态转化温度、熔化温度和材料的热容量。

差示扫描量热法和热重分析是用于了解挤压影响的强大而互补的技术组合。这些技术可用于分析聚合物在挤出温度下的热性能。³

测量热膨胀系数 (CTE) 和玻璃化转变温度的热机械分析是另一种配套工艺。由于玻璃态转化温度取决于材料的热历史，热机械分析可以用于检查挤压过程不会给成品带来任何不必要的力学行为。此外，增强材料在 CTE 中可能显示出各向异性，这取决于相对于纤维方向的测量方向。³

动态热机械分析也被广泛用于材料工程，用于分析聚合物复合材料，因为其可以揭示材料在动态负载条件下的行为信息。⁵DMA 对于表征 3D 打印成品部件特别重要，反映了不同的配方和加工方法如何影响最终使用性能。

选择合适的 3D 打印热分析技术

大多数 3D 打印生产线依赖于上述技术的组合。作为全球热分析领域的领导者，TA Instruments 是全球添加物制造商的首选仪器供应商。

我们致力于帮助各行各业的用户找到适合其独特 3D 打印目标的仪器和方法。我们提供一系列行业领先的热分析仪器，这些仪器的设计易于使用且效率高。TA Instruments 的综合热分析产品系列拥有所有必要的设备，可以完全表征基板的热性能和机械性能。

立即联系我们的专家，了解 TA Instruments 系列热分析和机械分析仪器如何提高 3D 打印产品的质量。

参考:

Trenfield, S. J., Awad, A., Madla, C. M., Hatton, G. B., Goyanes, A., Gaisford, S., Basit, A. W., Trenfield, S. J., Awad, A., Madla, C. M., & Hatton, G. B. (2019). Shaping the future: recent advances of 3D printing in drug delivery and healthcare. Expert Opinion on Drug Delivery, 16(10), 1081–1094. https://doi.org/10.1080/17425247.2019.1660318
Mohammadizadeh, M., & Fidan, I. (2019). Thermal Analysis of 3D Printed Continous Fiber Reinforced Thermoplastic Polymers for Automotive Applications. Solid Freeform Fabrication 2019: Proceedings of the 30th Annual International Solid Freeform Fabrication Symposium – An Additive Manufacturing Conference, 899–906. https://utw10945.utweb.utexas.edu/sites/default/files/2019/078%20Thermal%20Analysis%20of%203D%20Printed%20Continuous%20Fiber%20Re.pdf
Billah, K. M., Lorenzana, F. A. R., Martinez, N. L., Chacon, S., Wicker, R. B., & Espalin, D. (2019). Thermal Analysis of Thermoplastic Materials Filled with Chopped Fiber for Large Area 3D Printing. Solid Freeform Fabrication 2019: Proceedings of the 30th Annual International Solid Freeform Fabrication Symposium – An Additive Manufacturing Conference, 892–898. https://utw10945.utweb.utexas.edu/sites/default/files/2019/077%20Thermal%20Analysis%20of%20Thermoplastic%20Materials%20Filled.pdf
TA Instruments (2022) 3D Printing Webinar, https://www.tainstruments.com/3-d-printing-and-additive-manufacturing-process-optimization-a-thermal-approach/, accessed May 2022
Saba, N., Jawaid, M., Alothman, O. Y., & Paridah, M. T. (2016). A review on dynamic mechanical properties of natural fibre reinforced polymer composites. Construction and Building Materials, 106, 149–159. https://doi.org/10.1016/j.conbuildmat.2015.12.075

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