Poly impact properties

Most of the polymer s characteristics stem from its molecular stmcture, which like POE, promotes solubiUty in a variety of solvents in addition to water. It exhibits Newtonian rheology and is mechanically stable relative to other thermoplastics. It also forms miscible blends with a variety of other polymers. The water solubiUty and hot meltable characteristics promote adhesion in a number of appHcations. PEOX has been observed to promote adhesion comparable with PVP and PVA on aluminum foil, cellophane, nylon, poly(methyl methacrylate), and poly(ethylene terephthalate), and in composite systems improved tensile strength and Izod impact properties have been noted. 

BiaxiaHy oriented films have excellent tensile strength properties and good tear and impact properties. They are especially well regarded for their brilliance and clarity. Essentially all poly(ethylene terephthalate) film is biaxiaHy oriented, and more than 80% of polypropylene film is biaxiaHy oriented. Polystyrene film is oriented, and a lesser amount of polyethylene, polyamide, poly(vinyl chloride), and other polymers are so processed. Some of the specialty films, like polyimides (qv), are also oriented. 

The use of ABS has in recent years met considerable competition on two fronts, particularly in automotive applications. For lower cost applications, where demands of finish and heat resistance are not too severe, blends of polypropylene and ethylene-propylene rubbers have found application (see Chapters 11 and 31). On the other hand, where enhanced heat resistance and surface hardness are required in conjunction with excellent impact properties, polycarbonate-ABS alloys (see Section 20.8) have found many applications. These materials have also replaced ABS in a number of electrical fittings and housings for business and domestic applications. Where improved heat distortion temperature and good electrical insulation properties (including tracking resistance) are important, then ABS may be replaced by poly(butylene terephthalate). 

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... 

As block copolymers are still rather expensive materials, it may be advantageous to use them as additives to important industrial polymers. In this domain, possibilities are extremely numerous and diverse. They include an improvement of chemical properties such as resistence to degradation agents, or rheological properties such as adhesion of vinylic paints, high impact properties of conventional thermoplastics, or a compatibilization of polyolefins, polystyrene and poly(vinyl chloride) allowing the reuse of polymeric waste products. The above examples illustrate the great intrinsic potential of block copolymers in the quest of new materials with specific properties. 

Table 11.18 shows the effect of increasing the poly sulfide-epoxy ratio on impact properties the effect at concentrations of polysulfide polymer greater than 1 1 is especially significant. The combination of increased flexibility, tensile strength, and elongation is very desirable in certain adhesive applications. 

The acrylic plastics use the term acryl such as polymethyl methacrylate (PMMA), polyacrylic acid, polymethacrytic acid, poly-R acrylate, poly-R methacrylate, polymethylacrylate, polyethylmethacrylate, and cyanoacrylate plastics. PMMA is the major and most important homopolymer in the series of acrylics with a sufficient high glass transition temperature to form useful products. Repeat units of the other types are used. Ethylacrylate repeat units form the major component in acrylate rubbers. PMMAs have high optical clarity, excellent weatherability, very broad color range, and hardest surface of any untreated thermoplastic. Chemical, thermal and impact properties are good to fair. Acrylics will fail in a brittle manner, independent of the temperature. They will suffer crazing when loaded at stress about halfway to the failure level. This effect is enhanced by the presence of solvents. 

The impact properties of poly(methyl methacrylate) (PMMA) may be improved by mechanical blending of small rubber particles with the matrix. Several authors have investigated the toughening mechanisms of these materials, which at present are only partially understood. In 1989, Mauzac and Schirrer (1) studied the effect of the rubber particles at the crack tip. They looked at particle volume fractions that ranged over five decades of concentra-... 

EVAl/poly(hydroxybutyrate-valerate) biodegradability, and good impact properties Webb etal., 1992... 

Poly(propylene) (PP) resins are improved in mechanical properties and in rigidity without loss in thermal processability when blended with PPA resins together with a minor amount of compatibilizer [30]. Blends of PP and functionalized PP with PPA in a weight ratio of 1 3-3 1 generally exhibit excellent impact properties [31]. Similarly, filled compositions, including glass-filled PPs, are improved when blended in the same way. 

Various approaches have been undertaken for reactive compatibilization of poly-amide/ABS alloys. Maleic anhydride can be grafted to the ABS. Styrene maleic anhydride (SMA) copolymers have been employed as compatibilizers for polyamide/ABS blends. SMA and SAN copolymers are miscible when the AN and maleic anhydride (MA) contents are equal. The impact strength of these blends has been found to be sensitive to the amount and composition of the SMA copolymer. Addition of SMA to SAN/polyamide blends was found to enhance the tensile and impact properties of these blends. Imidized acrylic polymers have been used as compatibilizers for nylon-6/ABS blends. Glycidyl methacrylate and methyl methacrylate (GMA/MMA) copolymers are used as compatibilizing agents. The epoxide functionality in GMA is capable of reaction with polyamide end groups. GMA/MMA copolymers can be shown to be miscible with SAN over the range of AN content of ABS. Styrene/GMA copolymers have been reported to be used as compatibilizers for polymer pairs such as... 

Dynamic mechanical analysis has also been used to determine the mechanical and thermal properties of low-density polyethylene and ethylene-propylene-diene terpolymer containing jute filler, which had improved flexural and impact properties compared to those of the base polymer [198]. Jeong and coworkers [196] and others [195] investigated the dynamic mechanical properties of a series of polyhexamethyl-ene lerephthalale, poly(l,4-cyclohexylenedimethylene terephthalate), and random copolymers thereof in the amorphous state as a function of temperature and frequency. The effect of copolymer composition on dynamic mechanical properties was examined and the dynamic mechanical properties interpreted in terms of the cooperativity of segmental motions. 

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. 

Phosphorus-based flame retardants are usually more suitable for engineering plastics that undergo charring than for commodity polymers. In some plastics, such as PC-ABS or poly(phenylene oxide)-HIPS blends, phosphorus-based flame retardants are more effective then halogenated flame retardants. Antimony trioxide, which is a part of halogen-containing formulations, is a Lewis acid and may destabilize some condensation polymers. Furthermore, the impact properties of engineering polymers may suffer due to the presence of powdery antimony trioxide. 

A TEM study of poly(vinyl chloride)/chlori-nated polyethylene (PVC/CPE) assessed the dispersed phase morphology for correlation with impact properties [342]. Microtomed sections of the blend were stained by a two stage osmium tetroxide method to reveal the CPE phase [343] as the concentration increased, the discrete two phase morphology changed to a continuous network resulting in a transition from brittle to ductile impact fracture (shown... 

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