High-impact polystyrene electrical properties

In this context numerous changes were made. The chapter Properties of Polymers was revised and a new section Correlations of Structure and Morphology with the Properties of Polymers was added. The chapter Characterization of Macromolecules was revised and enlarged. 15 examples have been deleted as they did no longer represent the state of the art and/or were of minor educational value. Several new experiments (plus background text) were added, as, for example controlled radical polymerization - enzymatic polymerization - microemulsions - polyelectrolytes as superabsorbants - hyperbranched polymers - new blockcopolymers - high impact polystyrene - electrical conducting polymers. 

As mentioned earlier, unmodified polystyrene first found application where rigidity and low cost were important prerequisites. Other useful properties were the transparency and high refractive index, freedom from taste, odour and toxicity, good electrical insulation characteristics, low water absorption and comparatively easy processability. Carefully designed and well-made articles from polystyrene were often found to be perfectly suitable for the end-use intended. On the other hand the extensive use of the polymers in badly designed and badly made products which broke only too easily caused a reaction away from the homopolymer. This resulted, first of all, in the development of the high-impact polystyrene and today this is more important than the unmodified polymer (60% of Western European market). 

Perhaps the best known member of the "heat-resistant" styrene plastics family is General Electric s Noryl (34). Noryl is an alloy of poly(phenylene oxide) and high-impact polystyrene. Heat deflection temperatures for Noryl range as high as 300 °F. The balance of mechanical properties is excellent, although processability is more difficult than for conventional styrene plastics. 

Chlorinated paraffins are claimed to be one of the lowest cost FRs besides the hydrated metal oxides. They can be used with antimony oxide as FRs in unsaturated polyester resin systems. Special grades have been developed by Dover Chemical in its Hordaresin and Chlorez ranges for flame retarding high-impact polystyrene, offering an absence of polyhalogenated biphenyls or dioxins, low cost, improved melt flow, and better UV stability than aromatic brominated FRs. They are also used in rubber compounds, where they can also improve tensile and tear properties of neoprene, SBR, and nitrile, and in EPDM rubber for electrical or roofing products. 

The most important commercial polymer is a blend of poly[oxy-(2,6-dimethyl-phenylene)] with high-impact polystyrene (HIPS). The corresponding material exhibits variable characteristics, depending on the PS content. It is a widely used technical polymer in mechanical engineering. Indeed, it exhibits a good impact resistance at very low temperatures in addition to its good thermal and mechanical properties. Its marked electrical insulating character even in wet atmospheres finds applications in electric and electronic industries. 

HIPS (High impact polystyrene) - the major application for this plastic is in the packaging industry, where low cost and rigidity are economically emd technically vital. The material has a tendency to yellow and shows very poor mar resistance. The most important application for the coating supplier is the widespread use of this plastic in the consumer electronics industry. Electrical insulation properties are good and cost is low. 

Around 8% bromine content in the final PBT compound is sufficient to achieve the V-0 test rating for all types of brominated flame retardants, but some affect the physical and mechanical properties of the resultant materials more than others. Polymeric brominated styrene additives would be preferred in glass-filled compounds. Brominated polystyrene, such as Saytex HP-7010 from Albemarle Corp. and poly(dibromostyrene) are such materials. They retain excellent properties after heat ageing. High impact strengfti and excellent electrical properties are especially noted for HP-7010 due to the additive s high purity and low aliphatic halogen content. 

---