HIPS, additives Flame retardants

Noryl. Noryl engineering thermoplastics are polymer blends formed by melt-blending DMPPO and HIPS or other polymers such as nylon with proprietary stabilizers, flame retardants, impact modifiers, and other additives (69). Because the mbber characteristics that are required for optimum performance in DMPPO—polystyrene blends are not the same as for polystyrene alone, most of the HIPS that is used in DMPPO blends is designed specifically for this use (70). Noryl is produced as sheet and for vacuum forming, but by far the greatest use is in pellets for injection mol ding. 

It should be mentioned that fire retardant-polypropylene has higher impact energy than polypropylene without HBCD and this improved impact energy resulting from the addition of fire retardant is a rare phenomenon. Usually the addition (15-25%) of low molecular components decreases the high impact properties of plastics although we know that HIPS flame-retarded with decabromodiphenyl oxide (DECA), for example, has almost the same impact energy as non-retarded HIPS (Table 5). 

Material balances for the pyrolysis products from HIPS equipped with flame retardants have been given (53). The pyrolysis experiments were performed to some extent in the presence of zeolite catalysts. The zeolites were added in order to remove organic bromine from the products of pyrolysis. In addition to their potential of destroying toxic brominated flame retardants, zeolites have been believed to be suitable to upgrade the pyrolysis products. 

In Reference 142, PET was used in blends with HIPS and modified MMT clay. The use of PET was justified since this polymer self-extinguishes under fire. In addition to study the flame-retardant properties of the HIPS-clay and HIPS-PET-clay systems, mechanical and rheological properties were measured to provide explanations on the... 

Impact strength reduction compared to an untreated HIPS resin can be offset by the addition of around 3% of a styrene-butadiene-styrene (SBS) rubber impact modifier. For black E E applications such as TVs the UV stability is no problem, but for lighter coloured goods this becomes an issue. An appropriate stabiliser and pigment presence is required. The presence of EBP also reduces the discoloration of HIPS after repeated cycles of regrind and further moulding and has little effect on mechanical, physical or flame retardant properties over this period. 

Noryl. Noiyl engineering thermoplastics are polymer blends formed by melt-blending DMPPO and HIPS or other polsrmers such as nylon with proprietary stabilizers, flame retardants, impact modifiers, and other additives (75). Because the rubber characteristics that are required for optimiun performance in... 

HIPS is currently processed by procedures such as injection molding, extrusion, blow-molding, and tbermoforming. HIPS properties can be further modified by incorporation of special additives such as flame retardants, stabilizers, antistatic agents, etc. The main production fraction of HIPS is consumed in the manufacture of packaging materials, technical products, toys, and various consumer goods. 

Commercial plastics are invariably mixtures of one or more polymers blended with a variety of additives such as colorants, flame-retardants, biocides, etc., all tailored to achieve cost-effective performance for specific applications or processibility requirements. For example, flexible PVC for wire insulation contains one or more plasticizers, and poly (2,6-dimethyl-1,4-phenylene oxide) (PPO), an engineering plastic, is marketed in several grades which may contain varying amounts of lubricants, stabilizers, fillers etc., in addition to the high-impact PS (HIPS) which is added to PPO to modify impact properties and melt viscosity. 

Wilkie and co-workers [69, 70] synthesized two organically modified clays to produce nanocomposites of PS, HIPS, and ABS terpolymer. They used the following copolymers to modify clay vinylbenzyl chloride (COPS) and methyl methacrylate and vinylbenzyl chloride (MAPS). The cation head for clay modification with these compounds was ammonium. After melt-blending, styrene copolymer-modified clays yielded exfoliated nanocomposites, whereas the methacrylate copolymer clays yielded a mixture of immiscible and intercalated nanocomposites. In general, all nanocomposites exhibited improved thermal stability and mechanical properties, in addition to improvements in flame retardancy, depending on the quality of clay dispersion. 

In contrast to the Cloisite clays, addition of phosphate-coated clays was able to improve the flame retardant response in certain classes of polymers. For example, addition of 5% RDP-coated clays to PC was able to achieve a UL-94 VI rating, whereas the addition of Cloisite 20A failed. Similarly, addition of 10% RDP-coated clays to HIPS achieved a rating of VI, whereas no effect was observed with Cloisite clays. 

PyGC-MS enables differentiation between various brominated flame retardants. Pyrograms of the reference materials (pure FRs) need to be compared with that of the sample to be examined in order to identify the flame retardant class. Selection of the pyrolysis temperature is most important. A compromise between mobilisation of the flame retardants and minimisation of thermal reaction products has to be found. Flame retardants were identified in EPR/TBBA, ABS/TBBA, PBT/TBBA, PP/PBDE, HIPS/PBB, using an optimised pyrolysis temperature (430°C) for these systems [791]. PyGC-MS was also used for polymer and additive (FR) characterisation of a Japanese TV cabinet [792]. Figure 2.36 shows the additive fragments isolated, together with a proposed (sub)structure, sufficient to identify the flame retardant as tetrabromobisphenol-5 -bis-(2,3-dibromopropylether) (TBBP-S) on the basis of patent search. 

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