High-impact polyblends

Typical physical properties for an injection-molded transparent acrylic polyblend resin are given in Table II. The injection molding conditions used are given in Table III. Tensile, flexural, and impact properties are within the range reported for typical ABS and high impact polystyrene resins. Optical properties approach those of the acrylics [i.e., poly (methyl methacrylate)]. The strength properties are on the low side of those reported in the first paper for the transparent diene... 

Craze formation is a dominant mechanism in the toughening of glassy polymers by elastomers in polyblends. Examples are high-impact polystyrene (HIPS), impact poly(vinyl chloride), and ABS (acrylonitrile-butadiene-styrene) polymers. Polystyrene and styrene-acrylonitrile (SAN) copolymers fracture at strains of 10 , whereas rubber-modified grades of these polymers (e.g., HIPS and ABS) form many crazes before breaking at strains around 0.5. Rubbery particles in... 

Compatible Polyblends. When the polymeric materials are compatible in all ratios, and/or all are soluble in each other, they are generally termed polyalloys. Very few pairs of polymers are completely compatible. The best known example is the polyblend of polyCphenylene oxide) (poly-2,6-dimethyl-l,4-phenylene oxide) with high-impact polystyrene (41). which is sold under the trade name of Noryl. It is believed that the two polymers have essentially identical solubility parameters. Other examples include blends of amorphous polycaprolactone with poly(vinyl chloride) (PVC) and butadiene/acrylonitrile rubber with PVC the compatibility is a result of the "acid-base" interaction between the polar substituents (1 ). These compatible blends exhibit physical properties that are intermediate to those of the components. 

Polyblends, also in most cases as high-impact-strength thermoplastics. The soft phase is an elastomer or semicrystalline thermoplastic with a low glass transition temperature Tg... 

The simplest method of polyblending involves equipment such as rolls or extruders, which can effect the mechanical blending of the two polymeric components in the molten state (Matsuo, 1968). High-impact polystyrene (HiPS) is an important example of a polyblend made by this technique. Such materials commonly contain 5-20 % of rubber, usually polybutadiene, dispersed in a polystyrene matrix. As shown in Figure 3.1, electron microscopy studies on specimens stained with osmium tetroxide reveal well-defined, irregular rubber particles (1-10 fim in diameter) dispersed in the polystyrene matrix. The elastomer domains appear dark because the osmium tetroxide stains the elastomer preferentially (see Section 2.4). 

Various additives show considerable extraction resistance, such as impact modifiers (polyacrylates and polyblends PVC/EVA, PVC/ABS, etc.), highpolymeric processing aids (PMMA-based), elastomers as high-MW plasticisers, reactive flame retardants (e.g. tetrabromobisphenol-A, tetrabromophthalic anhydride, tetrabromophthalate diol, dibromostyrene). Direct measurement of additives by UV and IR spectroscopy of moulded films is particularly useful in analysing for additives that are difficult to extract, although in such cases the calibration of standards may present a problem and interferences from other additives are possible. 

Saturated polyesters such as poly(ethylene terephthalate) and poly(butylene terephthalate) are characterized by high rigidity, good impact resistance, and low creep at room temperature. By polyblending with special graft polymers (49). it became possible to maintain these fine properties at -20 C and -40 C without sacrificing chemical resistance. 

Poly(vinyl acetals) are used in mechanical engineering as a polyblend with rubber for moldings, since the gapped joint impact strength and the flexural modulus are high. 

In the manufacture of engineering materials based on plastics, much emphasis has been placed on high modulus and great strength. The practice of polyblending small quantities of rubber into plastics has already been mentioned as a way to improve impact resistance and strain to break. The addition of carbon black to rubber increases tensile strength and abrasion resistance. 

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