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Highly engineered thermoplastic elastomers are finding broad application use these days. Traditionally, elastomers often involved silicones, polyurethanes, or crosslinked rubbers. For applications requiring greater mechanical properties, such as impact strength, modulus, and fatigue strength, block copolymers comprised of polyether amide (PEBA) are often found.

PEBAs are formed from the condensation polymerization of a carboxylic polyamide with a polyether (often a polyethylene glycol terminated by alcohols). Varying the relative lengths and amounts of the blocks results in a range of mechanical properties, including elasticity and energy damping.

PEBA in Sports Equipment

PEBAs are often used in sports equipment. Its fatigue resistance and relative immunity to temperature-related property change makes it a good candidate for the shells of ski boots, and the energy damping behavior and low density makes PEBAs attractive for the damping system in running shoes.

PEBA in Medical Devices

PEBAs can be injection molded and extruded, which permits forming into narrow wall constructs. This behavior, coupled with its biocompatibility and the lack of a need for plasticizers, has resulted in PEBAs use in catheters, tubing, and cannula.

Contact CPG for assistance in selecting polymer materials for your specific application. 

Material Characterization of Synthetic vs. Leather Balls 

The argument of synthetic over natural leather in football and other sports, such as rugby or basketball, ultimately comes down to ball feel and grip. Rugby has transitioned to synthetic surfaces (and anyone who ever caught a high ball made from leather in wet conditions is grateful for that), but in football the preferred elite ball composition is leather.  Is that choice advantageous or is it purely a preference for the traditional? CPG scientists sought to determine how different the two types of footballs really are. 

Leather vs. Pleather: Chemical Composition & Surface Topography

Fourier Transform Infrared Spectroscopy (FTIR) analysis confirmed that the leather football is comprised of animal hide, while the synthetic football is polyurethane-based. Not surprisingly, the FTIR spectra for the leather and synthetic material are markedly different.

Scanning Electron Microscopy (SEM) showed differences in the surfaces of the two footballs.  Natural animal hide is embossed to add the raised features into the leather football for improved friction.  The added topography increases the surface area of the football, making it easier to catch. Synthetic materials were designed to mimic the same embossed texture, yet the details of the microscopic fibrous nature of the leather are not captured in the man-made football (see below).

SEM micrographs of the surface of a leather (left) and synthetic (right) football. At higher magnification, the leather football appears fibrous while the synthetic surface is covered with small bumps on the order of 10 µm in diameter.

Ranking Football Friction Properties

CPG scientists determined the friction on a synthetic and natural leather ball using a conventional method to yield a coefficient of friction (CoF) that allows ranking of relative frictional properties, and also how those frictional properties vary with speed and wet versus dry.

Images of ball testing configuration (left) on AR-G2 rheometer, and leather (middle) and synthetic (right) balls. Blue material is silly putty used as a barrier to enable water to be trapped in the contact region.

Dry

Under dry conditions, the synthetic material appears to have higher friction than the leather at all speeds.  In both cases, the friction force increases with compression load, suggesting the grip gets better the harder the ball is held.

Wetted

The picture changes somewhat when the balls are wetted with distilled water.  The synthetic ball actually exhibits a marked drop in frictional force at higher loads (the leather ball also sees a slight decrease).  The leather ball would therefore have fairly consistent levels of grip, irrespective of how hard the ball were held, but the synthetic ball would have less grip at higher loads.  Although minor, this observation already indicates that the leather ball may have an advantage in less-optimal playing conditions.

Soaked

When the balls are soaked in water, the difference is even more dramatic. The synthetic ball is impacted by the soak, but to the detriment of grip, with a gradual decrease in frictional force. In contrast, the frictional force on the leather ball goes up as the ball gets wet, suggesting in fact that this ball should have improved grip in wet conditions.

The weakness in this friction discussion is the choice of counterface.  Most players either use bare hands (in the case of the quarterback) or silicone coated gloves (in the case of receivers).  The steel counterface used here was a pragmatic choice, and may not truly represent the frictional force, which can be very sensitive to both the surface chemistry, and the conformability of the material.  Nonetheless, this simple non-destructive ranking experiment yields insights into why the leather ball is still the choice of the elite sport divisions. GO PATS!

Read more about these results in this application note.

Join CPG scientists Stephen Spiegelberg and Gavin Braithwaite for a webinar on medical device cleanliness. The discussion will include examples of what happens when cleaning processes are not properly verified and validated, how to establish the number of samples to test, how to test for device cleanliness, and how to establish acceptable residue limits.

Dr. Spiegelberg is the chairman of the ASTM task group on Medical Device Cleanliness, and Dr. Braithwaite regularly consults on cleaning issues in the medical device area. 

This webinar is targeted towards:

• Medical device manufacturers
• Medical device engineers
• Process engineers
• Quality engineers
• Regulatory personnel

Duration: 30 minutes

Cleanliness in Medical Devices Webinar

Thursday, February 23, 2 p.m., Eastern Standard Time

To register, click here

A group of Irish researchers from Trinity College, Dublin have created a new, extremely sensitive pressure detector using Silly Putty. Physicist Jonathan Coleman mainly works with graphene, a 2D material that was isolated in 2004 with remarkable properties. Graphene is strong (200 times greater than steel), thin (1 million times thinner than a human hair), and the most conductive material on earth.

Silly putty, developed by industrial scientists nearly 70 years ago, also has unique properties of its own. Depending on how it is handled, Silly Putty can bounce, shatter, or flow like a viscous liquid. This rheological behavior is characterized by the Deborah number, which is the ratio of the response time of the material to the time scale of the experiment. A Deborah number much greater than 1 indicates the material will act like an elastic solid, whereas a Deborah less than 1 indicates the material will act like a fluid. This behavior is further illustrated in our application note on Silly Putty.

One of Coleman’s students came up with the idea of mixing graphene with Silly Putty, and the resulting material substantially altered the Silly Putty’s electromechanical properties. The new material, "G-putty," displayed unusual behaviors such as postdeformation temporal relaxation of electrical resistance and nonmonotonic changes in resistivity with strain due to the high mobility of graphene in the low-viscosity polymer matrix of Silly Putty. With a gauge factor greater than 500, this electromechanical sensor can measure pulse, blood pressure, and even the impact associated with the footsteps of a small spider.

Before "G-putty" fulfills its potential to become a wearable medical device, it must be shown to be reproducible in large quantities. Additionally, it must be tested to determine long term performance.

Earlier this week, Samsung announced the results of their investigation into the Galaxy Note 7 failure.  The Galaxy Note 7 phones spontaneously caught fire, leading to a recall of approximately 2.5 million devices and losses of over $2 billion dollars. Though the initial defective phones were recalled, their replacements also began to catch fire, spawning an investigation by Samsung.

According to an internal investigation aided by outside experts, the root cause of the failure was battery short circuits. Of the two companies that supplied batteries for the Galaxy Note 7, both had separate issues ultimately leading to fires.

Battery “A”, the original battery, suffered from a deformation in the negative electrode that caused it to touch the positive electrode. The deformation was caused by a design flaw in the pouch (a “case” surrounding the battery components) that did not allow sufficient space for the battery components to expand and contract during charging and discharging cycles. This caused the negative electrode to become bent; weakening a component designed to keep the positive and negative electrodes from touching, eventually allowing the positive and negative electrodes to come into contact.

Battery “B”, the replacement batteries, failed due to a welding issue on the positive tab. A small piece of welding material was left sticking out and was enough to perforate the separator that keeps the positive and negative electrodes from touching, causing a short circuit. The short circuit caused temperatures high enough to melt copper elements inside of the phone.

Samsung said it is implementing an 8-point battery safety check intended to ensure the quality and safety of its products going forward.

Samsung’s battery issues highlight several areas broader than the battery technology field.  Having a robust quality system in place that encompasses vendors, incoming components, internal procedures and final product quality is essential to avoiding the situation in which Samsung found itself – high-profile and dangerous field failures of its products.  One specific aspect of such a quality system would include sufficient reliability testing of both components and final assemblies to catch potential failure modes before a product is released. Whether failures are discovered during internal testing or during service, detailed failure analysis to determine the root cause of the failures is essential to reaching a solution. 

Cambridge Polymer Group identifies opportunities for quality system improvements, designs and implements effective reliability testing, and conducts failure analysis employing a variety of analytical techniques and multi-disciplinary professional expertise. Ensure your products perform to your customers’ satisfaction, minimizing the risk of embarrassing field failures.  

Olive oil, which is simply the oil extracted from the fruit of olive trees, has been cultivated for thousands of years across the Mediterranean Basin. Today, olive oil is steadily increasing in popularity across the globe due to its health benefits. Some studies suggest that long-term consumption of small amounts of olive oil may aid in a lower incidence of heart disease due to the chemicals polyphenol and oleocanthal, an antioxidant, obtained from the oil.

Bottom of the Barrel

The highest grade of olive oil, called extra-virgin, is an unrefined oil which contains a higher amount of natural vitamins and minerals found in olives. The International Olive Council (IOC) governs approximately 95% of international olive oil production and regulates the use of labels for olive oils. According to the IOC standard for extra-virgin olive oil, the oil must not contain more than 0.8% acidity and is judged to have superior taste and no sensory defects.

Of all varieties of olive oil, extra-virgin accounts for only about 10% of oils in major producing countries. Unfortunately, the United States is not a member of the IOC, and with only voluntary standards put in place by the USDA, Americans are often left with the “bottom of the barrel.” In a 2010 study performed by the University of California, Davis it was found that nearly 69% of supermarket oils marketed as “extra-virgin” were not actually extra-virgin according to IOC standards.

Migration Testing in Food Packaging

At CPG, we test olive oil, but not to determine its IOC grade. Instead, we use olive oil as a fatty food stimulant for migration testing in food packaging. Samples of food packaging, or plastic that is contact with food, such as conveyor systems, are immersed in olive oil for specified lengths of time.  The amount of extracted products from the plastic into the oil must be determined by accounting for the weight loss in the sample, corrected by the amount of absorbed olive oil into the sample. Typically, extraction with derivatization of the oil, followed by GC-MS, allows quantitative assessment of the amount of absorbed oil. In addition, GC-MS, along with LC-MS, can be used to quantify and identify individual species extracted by the oil from the plastic. Details of the requirements for food contacting materials in Europe can be found in EU No. 10/2011.

For more information, please visit our packaging analysis page.