Electrical grade polyester

The polyester alkyd resins are lower in cost than the DAP resins but are weaker mechanically, have a lower resistance to cracking round inserts and do not maintain their electrical properties so well under severe humid conditions. Fast-curing grades are available which will cure in as little as 20 seconds. 

Polyester, thermoplastic TP polyesters have different grades. Polybutylene tereph-thalate (PBT) a crystalline polymer and an excellent engineering material. It has marginal chemical resistance but resists moisture, creep, fire, fats, and oils. Molded items are hard, bright colored, and retain their impact strength at temperatures as low as — 40°F (-40°C). Uses include auto louvers, under-the-hood electricals, and mechanical parts. 

Polyesters are good insulators even in wet environments with high dielectric resistivities and rigidities, and low or moderate loss factors. Special grades are marketed for electrical applications such as connectors. 

The process is used extensively for the production of yarns and fibres monofilaments and strapping for recycling of scrap polyesters in production of PET containers and soft-drink bottles engineering grades of PET and PBT for electrical, engineering and automotive applications. 

Kaolin deposits are cored and analyzed before mining to determine quality. Mined clays are then either wet or dry processed by air floatation or water fractionation. Surface-modified clays can be made by treating standard, delaminated, and calcinated grades with surface modifiers. The treatment can be performed by either the supplier or the end user. These surface modifiers include silane, titanate, polyester, and metal hydroxide. The objective of these surface treatments is to increase filler loadings and/or improve physical properties such as melt viscosity, thermal stability, and modulus without loss of physical characteristics. Electrical applications represent the largest use of surface-modified kaolin in plastics. 

The glass-reinforced thermoplastic polyester resins are nnusual in that they are the first thermoplastic that can compare with, or are better than, thermosets in electrical, mechanical, dimensional, and aeep properties at elevated temperatures (approximately 150°C), while having superior impact properties. The glass fiber concentration usually ranges from 10 to 30 percent in commercially available grades. In molded parts, the glass fibers remain slightly below the surface so that finished items have a very smooth surface finish as well as an excellent appearance. 

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. 

Renewed development and marketing effort is expected with brominated epoxy oligomers, now in the hands of Resolution Performance Products, following a sell-off from Shell. These materials are well established for thermosets, such as epoxy resins, phenolics, and vinyl esters, but modified grades have recently been introduced aiming at thermoplastics, such as styrenic and (significantly, because of its potential in electrical and electronics equipment) ABS. Thermoplastic polyesters, elastomers, and polyolefins can also be flame retarded with these materials which have a bromine content of 50-60% weight... 

A flame retardant polyester offering good electrical properties when vacuum bag or autoclave processed. Meets MIL-R-7575, Grade A, Class 3. 

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