Materials Roundup
Swedish polymer compounder Hexpol has announced that its Mediprene brand of custom formulated TPEs—manufactured by its Elasto subsidiary—has been used to manufacture a brand of high-quality ear plugs, Happy Ears.
According to Hexpol, ordinary earplugs can often muffle both lower and higher frequencies which can lead to a tinny, muddy sound. Happy Ears, on the other hand, give an average noise-reduction of around 20 dB at all frequencies. This means that the earplugs protect the ears from harmful noises as well as retaining sound quality and feeling
The ear plug’s construction, said to be unique, comprises a hardened “foot” at one end and a soft “leg” at the other. The design helps to preserve sound quality whilst providing high levels of protection and comfort. Happy Ears are made from ABS in the core and Mediprene TPE on the outer surface.
Mediprene TPEs have been engineered to address the demands of the medical device industry. Representative grades have passed cytotoxicity tests according to ISO 10993-5 and biocompatibility tests according to USP Class VI. The materials are latex free, which reduces the risk of allergic reactions; Mediprene TPEs have been classified as non-sensitisers. This was a key factor in the decision to use Mediprene TPE in Happy Ears.
The softness of the Mediprene TPE compound means that when the earplug’s soft hat is placed in the outer ear, it automatically moulds itself according to the shape of the ear, becoming almost round. The soft material then tries to return to its original oval state and it is this which creates pressure against the outer ear canal. This pressure means that the Happy Ears earplug fits securely, thus preventing sound from reaching the eardrum.
Happy Ears combination of unique design and advanced materials helped them win the Swedish design competition ‘Object of the Year’ in 2012.
Medical grade silicones manufacturer Wacker has launched Silpuran 2410 A/B, a new silicone rubber of variable hardness for orthopaedic and prosthetic applications. The new material is an addition-curing silicone which consists of two components, A and B. The material can be made to be harder or softer in the lower shore A range by varying the mixing ratio of the two components. This gives manufacturers the flexibility to regulate the hardness of the elastomer during processing.
Having this flexibility is expected to benefit manufacturers of small runs. Whereas they would previously have needed to stock many different grades of silicone if they wanted to make products of different hardness, they now have in the new Slipuran range a product whose hardness can be flexibly adjusted to suit the intended application. Thus, a single silicone raw material is now capable of satisfying different specifications.
US medical and pharmaceutical silicone formulator NuSil Technology has introduced a translucent liquid injection moulding grade fluorosilicone elastomer.
The material, MED-5440, resists swell when in contact with or immersed in dimethyl fluids and most solvents or oils. Some typical applications for MED-5440 include O-rings, gaskets, seals, and precision moulded parts for implant applications requiring silicones of medium durometers that resist swell.
“MED-5440 is an excellent choice for moulding high quality silicone parts that require some degree of resistance to solvents, alcohols, fluids or oils,” said Brian Reilly, NuSil’s marketing and sales director for medical implants.
MED-5440 is a two-part silicone rubber with a 1:1 mix ratio and a type A durometer of 40. During moulding, it cures rapidly when exposed to heat.
US manufacturer of silicone for medical applications Dow Corning is promoting QP1, a new silicone technology for the company's high consistency rubber (HCR) product line.
Said to be well suited for medical tubing and other extruded applications—including short-term implants—the one-part QP1 HCR bases are supplied uncatalysed to offer medical device OEMs and fabricators flexibility in processing, enabling them to choose the most suitable formulation for each application. The materials provide high strength and can be platinum catalysed using Dow Corning masterbatches. Alternatively, the products can be cured using a peroxide initiated system.
QP1 silicone elastomers, available in Shore A hardnesses of 30, 50, 60 and 70, are formulated without the use of solvents, phthalates or latex additives.
Researchers at synthetic fibre manufacturer Teijin Aramid, based in the Netherlands, and Rice University in the USA have published findings on a new generation of “super” fibres in the leading scientific journal, <i>Science</i>.
According to the report, for the first time in history it has been possible to spin carbon nanotubes (CNTs) into a super fibre that has very high thermal and electrical conductivity and good textile performance. Carbon nanotubes, the building blocks of the fibre, which is as thin as a strand of DNA, combine the best properties of thermal and electrical conductivity, strength, modulus and flexibility.
To spin a high-performance carbon nanotube textile fibre, the nanotubes must be perfectly stacked and orientated along the fibre’s axis. The most efficient method to produce this fibre is to dissolve CNTs in a super acid, followed by wet-spinning. This is a patented process which has been used since the 1970s in spinning Teijin Aramid’s Twaron super fibre.
US manufacturer of flexible polymer compounds Teknor Apex has developed two high-hardness grades in its Medalist MD-200 series of thermoplastic vulcanisate (TPV) elastomers, extending the already broad durometer range of these resilient, high-purity compounds for replacing rubber in medical applications.
Previously ranging in shore A durometer from an ultra-soft 15 to a semi-hard 80, the Medalist MD-200 series now includes an 87 shore A compound, MD-240, and a 43 shore D grade, MD-245. The 43 shore D durometer is roughly equivalent to a shore A hardness of 93 (see image).
The new compounds are suitable for extrusion, injection moulding, and blow molding. Suggested applications include peristaltic tubes, collection and drainage tubes, stoppers for vials, caps and plugs, seals and gaskets, device handles, ergonomic soft grips, valves, and diaphragms.
The rubber-like properties of Medalist MD-240 and MD-245 include low long-term compression set, high fatigue resistance, prolonged flex life, stability at high temperatures, abrasion resistance, and long-term sealability.
“Among the benefits of the TPV technology developed by Teknor Apex for the MD-200 series are the elimination of the need for pre-drying, since all grades are non-hygroscopic, and a light natural colour that permits efficient use of colorants,” said Keith Saunders, senior market manager for the thermoplastic elastomer division. “What also sets us apart is that we manufacture our TPV compounds ‘from scratch,’ starting with polymers and all other basic ingredients, rather than using a masterbatch intermediary. This gives us tight control over properties and considerable freedom to formulate custom compounds that precisely meet customer requirements.”