Polyethylene/clay resistivity

As stated previously, styrene-diene triblock copolymers are the most important category of thermoplastic elastomers. Unlike most other TPEs, they can be blended with large quantities of additives without a drastic effect on properties. In almost all applications, the actual triblock copolymer content is less than 50%. Oils are used as a processing aid and do not result in a significant loss of properties if the polystyrene domains are not plasticized. For this reason, naphthalenic oils are preferred. The use of inert fillers such as clays or chalks reduces the cost of the final material. Unlike conventional rubbers, inert fillers do not have a substantial effect on the mechanical properties of TPEs. Thermoplastics such as polyethylene or polypropylene are also used to improve the solvent resistance and can increase the upper service temperature. Polystyrene homopolymer is used as a processing aid, which also increases the hard phase weight fraction and causes the material to stiffen. 

There is some overlap in the performance of metakaolinite and calcined clay in certain polymers and hence some contiguous applications such as low-voltage rubber cable insulation, but there are significant differences, which leads to separate use patterns. Thus, metakaolinite is mainly used in PVC cable insulation because it improves (uniquely) the electrical resistivity of plasticised PVC, while calcined clay is used in polyethylene (PE) film, rubber cables, rubber pharmaceutical applications and rubber extrusions for a variety of reasons linked to its shape, size and chemical inertness. The refractory product finds limited use in epoxy and unsaturated polyester mouldings, which have to resist abrasion and chemical attack. 

Dintcheva, N.T., Filippone, G., La Mantia, F.P., Aciemo, D. Photo-oxidation behaviour of polyethylene/polyamide 6 blends filled with organomodified clay improvement of the photo-resistance through morphology modification. Polym. Degrad. Stab. 95, 527-535... 

The base polymer for this t5q>e of sealant exists in the form of an emulsion of micron- and submicron-sized partides of the polymer suspended in water. The base polymer formed by free radical polymerization may be a homopolymer of an acrylic monomer but is more likely to be a copolymer of a number of different monomers chosen to provide the correct balance of properties. The polymer latex has to be made more permanent and therefore a nonionic surfactant such as a nonyl phenol/ polyethylene oxide is added to help stabilize the emulsion. Other additives to the sealant formulation include plastid-zers, fillers, solvents, and silanes. A plasticizer is added to the formulation in order to improve upon or maintain the flexibility of the sealant. Solvents (usually a small amount) are added to improve the tooling of the sealant after it is applied. In addition, a solvent could be a material such as ethylene or propylene glycol which can improve the resistance of the packaged sealant to temperatures below freezing. The most widely used filler for this type of sealant is calcium carbonate. Silanes are often added to acrylics to improve the wet adhesion of the sealant to glass. Other additives include antimildew agents (for tub and tile applications) and clay for rheological control. 

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