| Recorded: |
September 21, 2011 |
| Presented by: |
Dr. Richard Rabe, RTP Company |
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Whether you’re new to thermoplastic elastomers or you’re looking to expand your knowledge of these diverse and flexible materials, let Dr. Richard Rabe, Technology Manager for TPEs at custom compounder RTP Company, be your guide as he reviews the world of TPEs from formal definition to practical applications.
During this hour long webinar Dr. Rabe will get you up-to-date on the complete range of TPE materials available today: what are thermoplastic elastomers, how TPEs function in comparison to rubbers and plastics, performance characteristics of different TPE chemistries, and typical applications for each family of TPEs.
Questions Asked by Attendees
Q: Which TPE material will hold up to multiple autoclave steam sterilizations? Can any hold up as well as silicone rubber?
A: PP+EPDM TPVs and harder (say >70 ShrA) styrenic TPEs can survive autoclave environments (whereas thermoset silicones can be much softer) ; however, a main concern is distortion of the TPE part at the elevated temperatures within the autoclave cycle. Fully supporting the TPE in the part design is strongly recommended, along with minimizing molded-in stresses.
Q: What TPE's have excellent Gasoline and Ethanol resistance, good cyclic flexibility and cyclic compression and and abrasion/wear resistance?
A: This I answered verbally. First, is it gasoline / ethanol splash or immersion resistance? If splash, then an olefinic TPV or a co-polyether-ester will serve; for immersion you will need one of the "super" TPEs such as the polyamide based TPSiV or Zeotherm. Co-polyether-ester or polyether-block-amide are best for flex life; TPU based TPSiV for cyclic compression. TPU's are best for abrasion and wear resistance. No single currently available TPE is "best" at all of these performance criteria. Compromise and optimization will be necessary.
Q: Actually the question is not specific to corks, just general opinion on differences between TPV technology leaders
A: see the next question
Q: I believe that wine corks are extruded as a solid tube and then cut. What is the difference between performance quality of branded TPVs from leaders like technologies practiced by Exxon or Teknor?
A: some corks are extruded as cylinders and then cut; some are injection molded. The TPV technology leaders do an equally good job of providing quality products. The differences will be in subtle performance differences that stem from the specific property sets around which their TPV's were designed. The raw materials, formulations and cure state for a product intended for injection molding will be different from one designed for extrusion; they will be different for a product designed to maximize tensile properties vs. compressive or sealing properties, etc.
Q: How would the annealing characteristic be defined on a technical data sheet? Is it called out specifically in the test description on the TDS?
A: Annealing is sometimes performed on TPUs. Normally, the annealing conditions are specified on the supplier's TDS for the specific grade (time and temperature of annealing are reported).
Q: What are the primary differences between TPEs and TPUs?
A: A TPU is a TPE (TPE is an umbrella term). We will be covering later in the presentation (the different types of TPEs).
Q: Thanks for the food analogies. A fantastic way to present the concepts. :)
A: thank you. More people understand food than understand physics or chemistry!
Q: Which type of TPE is best suited for homogeneous distribution of fillers? Thanks.
A: Pure block copolymers because 100% of the volume is available (although some filler will be excluded for glassy or crystalline domains). Fillers are excluded from the cured rubber particles in a TPE and blends and alloys will usually result in some selectivity of where fillers reside.
Q: How again do you specifically define lower and upper static use temps?
A: The laboratory test method for upper use temperature entails a series of heat agings to find the highest temperature at which a TPE will retain 50% of some property of interest (usually tensile strength and elongation at break). The laboratory test for lower use temperature entails a brittle point measurement by which you find the lowest temperature at which five out of ten or seven out of ten samples do not fracture when struck (simultaneously) by a striker bar. Use temperature will be affected by application specific conditions like clamping forces, flex requirements and other dynamic situations and should be validated during prototype testing.
Q: First of all, thanks for these very clear explantations. Second, which of the elastomeric type can stand the migration test EN -1186-2 which means with simulant D in this case olive oil at 40 degree Celsius for at least 24 hours. Elastomeric with a shore A around 70 ( medical application).
A: The presentation will be made available through the folks at IDES. Olive oil at 40 deg. C is a tricky proposition for TPE's; the problem is that some can pass it at higher durometers that are otherwise not suitable for the application but they have trouble at lower durometers that are required. So it is not a TPE "type", but specialty grades or compounds that are designed to pass the migration test (not easy).
Q: Are there halogen free versions of TPE
A: Yes, halogen-free FR TPEs are available.
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