HIPS-polymers

In general, the properties of a HIPS type are superior in comparison to a general purpose PS. Properties of a HIPS polymer are shown in Table 9.2. 

HIPS is a thermoplastic that is widely used in packaging, toys, bottles, housewares, electronic appliances, and light-duty industrial components, because of its good rigidity and ease of coloring and processing. Flame retardant HIPS polymers find application in housings for business machines. Here we present recent issues and examples on applications of HIPS. 

Table 9.4 Examples for Commercially Available HIPS Polymers (14)...

Figures 14-1 and 14-2 show estimations of shelf life in a 7.5 g PS containing portion pack before two different taste threshold concentrations (2 and 0.1 mg/kg) of styrene are exceeded in the product. In each graph the diffusion coefficients from Linssen et al. (1992) for a 1 1 PS HIPS polymer blend at room temperature (23 °C) and refrigeration temperature (4 °C) are used. The estimation using Eq. (14-5) at 23 °C and 4 °C and an calculated apparent diffusion coefficient for PS/PE and PS/EVOH/PE structures (see Table 14-3) are used in Eq. (14-4) (see example 14-5) to calculate the days before a styrene taint is detected in the product. The shelf life is decreased by a factor of the square of the increase in the material s residual styrene content. As seen in Figures 14-1 and 14-2 a reduction in the taste threshold by a factor of ten means almost a 100 times decrease in the shelf life.

As explained earlier, most authors quote nominal mbber contents rather than mbber phase volumes, and there is therefore very little information in the literature on the relationship between Oyc and 0 for mbber-modified plastics. A rare exception occurs in the work of Oxborough and Bowden vdio measured yield stresses in tension and compression for a series of HIPS polymers ccmtaining composite rubber particles. Their results are presented in Fig. 7. Equation (9) underestimates the yield stresses both in tension and compression, and it must be concluded fiiat the effective area model does not provide a satisfactory basis for correlating yield data in this class of material. Either the model itself must be modified in some way, or some allowance must be made for load sharing with the mbber particles, if the effective area apprcrach is to be retained. 

HIPS polymers consist of a matrix of polystyrene containing approximately spherical particles of rubbery polybutadiene ranging in size from about 0.1 to 10 pm depending on the precise composition and method of polymerisation. The rubber particles may themselves contain small regions of PS as shown in fig. 12.7. Another series of rubber-toughened blends is the acrylonitrile-butadiene-styrene (ABS) terpolymers, which are basically... 

Styrene homopolymer is a rigid but brittle polymer with poor impact strength. Rubber is grafted to polystyrene to improve the impact strength of polystyrene. Fine rubber particles (0.5-10 p,m) are dispersed in the polymer matrix. The incorporated rubber particles are cross-linked and contain grafted polystyrene. The inner structure of the polymer is determined by the polymerization process. Because the refractive indices of the rubber and the polystyrene phases are different, HIPS polymer is a translucent-to-opaque white polymer which exhibits high-impact strength and is resistant to wear. Cis-polybutadiene is the most common rubber used in the manufacture of HIPS. The properties of HIPS depend on the amount and type of rubber as well as many other reaction variables. Rubber particles that are too small or... 

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. 

Rubber-Modified Copolymers. Acrylonitrile—butadiene—styrene polymers have become important commercial products since the mid-1950s. The development and properties of ABS polymers have been discussed in detail (76) (see Acrylonitrile polymers). ABS polymers, like HIPS, are two-phase systems in which the elastomer component is dispersed in the rigid SAN copolymer matrix. The electron photomicrographs in Figure 6 show the difference in morphology of mass vs emulsion ABS polymers. The differences in stmcture of the dispersed phases are primarily a result of differences in production processes, types of mbber used, and variation in mbber concentrations. 

Polystyrene. Polystyrene [9003-53-6] is a thermoplastic prepared by the polymerization of styrene, primarily the suspension or bulk processes. Polystyrene is a linear polymer that is atactic, amorphous, inert to acids and alkahes, but attacked by aromatic solvents and chlorinated hydrocarbons such as dry cleaning fluids. It is clear but yellows and crazes on outdoor exposure when attacked by uv light. It is britde and does not accept plasticizers, though mbber can be compounded with it to raise the impact strength, ie, high impact polystyrene (HIPS). Its principal use in building products is as a foamed plastic (see Eoamed plastics). The foams are used for interior trim, door and window frames, cabinetry, and, in the low density expanded form, for insulation (see Styrene plastics). 

High-distortion temperature (HDT) of the styrenic materials is around 100°C. Blending with polymers of high HDT may lead to blends of high HDT. Both compatible and noncompatible polymers can be used judiciously for this purpose, e.g., PS is compatible with PPE (HDT = 220°C) [150] on a molecular level. Therefore, it is not surprising that a blend of HIPS with PPE will... 

Dow ABS Nylon 6/6 Polycarbonate Polyethylene, HDPE, LDPE, LLDPE, ULDPE Polypropylene HPPP, CPPP Polystyrene HIPS, GPPS, Recycled, Advanced Styrenic Resin SAN Polyurethane Elastomers Polyolefin Plastomer PC/ABS Crystalline Polymer ABS/TPU... 

Hexamethylphosphoramide (HMPT), 185 HFBPA-based poly(arylene ether)s, 362 HFCs. See Hydrofluorocarbons (HFCs) High-impact polystyrene (HIPS), 219 High-melting polymers, 33 High-melting-point fiber-forming polyesters, 19... 

Table I provides an overview of general reactor designs used with PS and HIPS processes on the basis of reactor function. The polymer concentrations characterizing the mass polymerizations are approximate there could be some overlapping of agitator types with solids level beyond that shown in the tcd>le. Polymer concentration limits on HIPS will be lower because of increased viscosity. There are also additional applications. Tubular reactors, for example, in effect, often exist as the transfer lines between reactors and in external circulating loops associated with continuous reactors.

An idea of the range of materials and applications for polymers in medicine can be gained from the information in Table 10.1. As can be seen from this table a number of polymers are used in medical applications. One particular such polymer is poly (methyl methacrylate), PMMA. Early on it was used as the material for fabricating dentures later other biomedical applications developed. For example, PMMA is now used as the cement in the majority of hip replacement operations worldwide. 

Surprisingly, phosphorus when combined with bromine is effective in nonoxygen containing polymers. In another reference, a mixture of a brominated compound and a triaryl phosphate was claimed to be effective in HIPS where antimony oxide is generally required as a synergist for bromine (ref. 7). 

Cortes et al. [975] have used on-line p,SEC-CGC for rapid determination of a great variety of additives in an emulsion ABS-PVC blend, HIPS and a styrene-acrylate-ethylene rubber polymer. These systems are difficult to analyse, because of the high levels of insolubles such as fillers, pigments, or rubber modifiers. The additives were separated from the polymer fraction in a polymer/additive dissolution using p,SEC, and were... 

Abrasive wear of polymers has two components material can be removed by the rasping action of a countersurface or it can be sheared off viscoelastically by a countersurface to which it adheres. The precise balance of mechanisms depends on the characteristics of the counterface and the conditions under which the abrasion takes place. Many polymers exhibit excellent wear resistance, which in combination with their low coefficients of friction suit them for applications where lubrication is either impossible or undesirable. We use wear resistant polymers in such diverse applications as bushings in business machines, pump seals, and replacement hip and knee joints. 

Transition from liquid behavior to solid behavior has been reported with fine particle suspensions with increased filler content in both Newtonian and non-Newtonian liquids. Industrially important classes are rubber-modified polymer melts (small rubber particles embedded in a polymer melt), e.g. ABS (acrylo-nitrile-butadiene-styrene) or HIPS (high-impact polystyrene) and fiber-reinforced polymers. Another interesting suspension is present in plasticized polyvinylchloride (PVC) at low temperatures, when suspended PVC particles are formed in the melt [96], The transition becomes evident in the following... 

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