DuPont Mobility & Materials announced that it has rebranded its full portfolio of silicone masterbatches for thermoplastics as MULTIBASE™ products. The new brand took effect this month and applies to all legacy Dow Corning silicone-based masterbatch products
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Thermoplastic elastomers (TPEs) and polycarbonates (PCs) offer an interesting combination of rigid and soft materials for housings and interfaces in wearable applications. However, strong adhesion between TPE and PC materials is critical to achieve durable devices that can withstand repeated use. A recent study conducted by Covestro and Teknor Apex, “Adhesion of TPEs on Polycarbonates for Medical Wearables,” examined the adhesion and chemical resistance of medical grade resins that are candidates for wearable applications. In the study, the team evaluated the adhesion of newly introduced TPE grades designed specifically for overmolding on various medical grade PC substrates.
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Thermoplastic elastomers (TPE) are a class of materials that combine the advantages of a rubber, such as excellent compression set for good sealing, with the processability of conventional thermoplastics. Thermoplastic vulcanizate (TPV) is a subset of TPEs produced from a blend of vulcanized-crosslinked rubber finely dispersed in a continuous thermoplastic matrix. TPVs are produced by dynamic vulcanization, whereby a rubber is cured/ vulcanized within a thermoplastic polymer while the polymers are undergoing intimate mixing or mastication at elevated temperatures. Elasticity, tensile properties and hardness of the TPV are controlled by the ratio of the harder thermoplastic phase to the softer rubber phase. It is well known that TPVs exhibit the advantageous sealing properties of conventional cured rubber, excellent physical properties, good high temperature resistance and outstanding chemical resistance. Due to these benefits Santoprene TPVs have become a workhorse material for a variety of automotive sealing applications. The applications for TPVs in automotive sealing include glass run channels, dynamic seals, cowl vent grille seals and outer belt line seals
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In this study, Engage polyolefin thermoplastic elastomers (POEs) from Dow Chemical are used, which are random ethylene-octene copolymers with relatively low melting temperatures (Tm), and elastic recovery that is tunable and dependent on comonomer content. POE bilayers are molded, but unlike other natural and synthetic systems, each layer does not contain any anisotropy. So there is no orientation difference between the layers. Upon stretching and releasing, the bilayers exhibit bending, curling and twisting, depending on the elastic recovery difference between the layers and the applied strain. This has been termed mechanical programming. The shape change can be further controlled through the length (L) to width (W) ratio, L/W, of the formed bilayers
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The process for compounding thermoplastic elastomer formulations is comprised of multiple unit operations. These typically include, but are not limited to, feedstock introduction, polymer/ polymer or polymer/filler melt-mixing, distributive/dispersive downstream mixing of oil extenders/minerals/additives, removal of volatiles, and pressurization for die discharge. While each unit operation has an impact on process productivity and quality of the finished product, melt mixing and downstream feeding/filler incorporation have a significantly greater impact than the others in TPE compounding processes
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