Impact-modified polystyrene

ISO 14631 1999 Extruded sheets of impact-modified polystyrene (PS-I) - Requirements and test methods... 

Figure 4.40 shows an example of impact strength versus low temperatures for a given impact-modified polystyrene. 

ISO 2897-1 1997 Plastics - Impact-resistant polystyrene (PS-I) moulding and extrusion materials - Part 1 Designation system and basis for specifications ISO 2897-2 2003 Plastics - Impact-resistant polystyrene (PS-I) moulding and extrusion materials - Part 2 Preparation of test specimens and determination of properties ISO 14631 1999 Extruded sheets of impact-modified polystyrene (PS-I) - Requirements and test methods... 

We have tested the following polymers polycarbonate (PC), poly-carbonate/4% polyethylene blend (PC/PE), poly (ethylene terephthal-ate) (PET), ABS, and impact modified polystyrene (HIPS). All materials except PC were compression molded into nominal Vs-inch sheets. The PC used was an Vs-inch extruded sheet heat-treated in a manner previously described (22). These PC specimens were considered to be... 

Rubber-modified polystyrene was the next logical evolution after general-purpose polystyrene. Very early on it was apparent that the Achilles heel of polystyrene was its inherent brittleness. Rubber-modified polystyrene is a two-phase system consisting of a dispersed rubber phase and a continuous polystyrene phase (or matrix). Impact-modified polystyrene was invented as early as 1927 by Ostromislensky [15] by addition of natural rubber either polymerized with styrene or blended in polystyrene. 

To overcome the brittleness of GPPS, the material was modified by incorporation of polybutadiene. Impact-modified polystyrene (IPS) was invented by Ostromislensky [1] and has been commercialized since the 1950s. IPS consists of a polystyrene matrix with embedded cellular rubber particles. By rubber... 

Impact-modified polystyrene is mainly produced by mass polymerization, either in tower cascades or tank/tower cascades. In the latter case, particle size and morphology can be defined by variation of the viscosity ratio between the continuous and the discontinuous phases, the stirrer velocity, the molecular weight of the poly butadiene rubber and the amount of rubber. Typical particles sizes are 2-20 xm, this being the optimum for effectively dissipating impact energy. 

Zinc and castor oil cream was tested in a polystyrene jar using a four start lug finish to simplify removal of the closure (mother holding baby). Samples were stored at 4°C, 20°C, 30°C and 37°C. Jars cracked at the four stress points created by the four lug closure, first at 4°C then at the higher temperatures in ascending order of temperature (i.e. 6 weeks, 3 months, 7 months, 10 months). The subsequent use of an impact modified polystyrene with the return to a conventional continuous screw thread and screw cap ultimately provided a satisfactory pack. 

The characteristics of these TPEs depend on the relative proportions of the polymerized styrene and diene nnits as weU as the chemical nature of the monomers. At low styrene levels, the TPEs are soft and rnbbery. With increasing styrene contenf the TPE progressively becomes stiffer at room temperature, and it becomes a glossy, hard material similar to an impact-modified polystyrene (HIPS). Removal of the mbbery-block nnsatnr-ation by hydrogenation (to give S-EB-S materials) makes the styrenic TPEs mnch more resistant to oxidation and ozone attack. Commercially available styrenic TPEs range in hardness from 20 Shore A to 60 Shore D. 

General name given to a variety of grades which, except for the general purpose grades, include impact modified polystyrene. 

Polystyrene impact modifier Polystyrene additive for synthetic paper... 

Thermal oxidation of polystyrene is suppressed by adding phenols, such as 2,6 di-tert-butyl-p-cresol (BHT), long chain 3-(3,5-di-tert-butyl-4-hydroxyphenyl)-propion-ates or sebacates in combination with phosphorous compounds, such as substituted phenyl phosphites (TNPP) or phosphonites. Impact modified polystyrene is stabilized only by phenols, because phosphites affect the polymerization kinetics. 

Impact modified polystyrene and ABS are prone to oxidation because of their polybutadiene content. Under weathering conditions degradation begins at the surface and is seen in yellowing and rapid decline of mechanical properties such as impact strength. The development of sterically hindered amines allowed, albeit to a limited extent, the use of SB and ABS in outdoor applications [86]. 

Traces of copper or iron scarcely influence the photo-oxidative stability of PPE. However, if PPE containing copper or iron compounds is mixed with impact modified polystyrene (SB), the result is a significant reduction in photo-oxidative stability. Iron(III)chloride causes strong degradation, followed by copper(II)chloride and acetate the least damaging is iron(III)acetate [86]. 

Impact modified polystyrene is sensitive to oxidation because of its unsaturated bonds, similar to ABS. Selective oxidation initially starts with chain cleavages of grafted positions in impact modified polystyrene, thus reducing the number of double bonds. Higher temperatures result in thermal degradation of impact modified polystyrene [766]. 

Figure 5.182 shows thermal-oxidative aging behavior of non-stabilized and stabilized impact modified polystyrene exemplified by the change in mechanical properties. 

Change in impact strength and strain for impact modified polystyrene as a funotion of aging time at 80 °C [86]... 

Relative yield strain of specimens of impact-modified polystyrene exposed to tensile stress as a function of storage time In trichlorofluoromethane (Freon) atmosphere [193]... 

Synthetic rubbers, discussed in Section 15.16, are often copolymers chemical repeat units that are employed in some of these rubbers are shown in Table 14.5. Styrene-butadiene rubber (SBR) is a common random copolymer from which automobile tires are made. Nitrile rubber (NBR) is another random copolymer composed of acrylonitrile and butadiene. It is also highly elastic and, in addition, resistant to swelling in organic solvents gasohne hoses are made of NBR. Impact-modified polystyrene is a block copolymer that consists of alternating blocks of styrene and butadiene. The rubbery isoprene blocks act to slow cracks propagating through the material. 

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