Rubber modified polyblends

Perhaps the most important conclusion to emerge from the study of bound antioxidants is that it is much more cost-effective to attach antioxidants to those domains in the polymer that are most susceptible to oxidation. In the case of rubber-modified polyblends,... 

Polybutadiene based polyblends (Table 3.19) are very important plastics with industrial applications, e.g. impact resistance polymers and impact modifiers for rigid poly(vinyl chloride). These polyblends are very susceptible to photo-oxidative degradation, because of the presence of polybutadiene. Intensive studies of the photo-oxidation of the rubber modified polyblends lead to the following conclusions [761-764, 1936] ... 

KESKKULA, H., Chapter entitled Rubber-modified Styrene Polymers in Polyblends and Composites (Ed. bruins, p. f.). Interscience, New York (1970)... 

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... 

The commercial success of ABS polymers has led to the investigation of many other polyblend materials. In some cases properties are exhibited which are superior to those of ABS and some of the materials are commercially available. For example, the opacity of ABS has led to the development of blends in which the glassy phase is modified to give transparent polymers whilst the limited light aging has been countered by the use of rubbers other than polybutadiene. 

IR spectroscopy can be used to characterise not only different rubbers, but also to understand the structural changes due to the chemical modification of the rubbers. The chemical methods normally used to modify rubbers include hydrogenation, halogenation, hydrosilylation, phosphonylation and sulfonation. The effects of oxidation, weathering and radiation on the polymer structure can be studied with the help of infrared spectroscopy. Formation of ionic polymers and ionomeric polyblends behaving as thermoplastic elastomers can be followed by this method. Infrared spectroscopy in conjunction with other techniques is an important tool to characterise polymeric materials. 

The physical mixing of two or more polymers to crate a material with properties different from each of the components has become an increasingly popular route to new materials development. The resulting blend or alloy greatly reduces the associated time and costs while permitting improved processibility and enhanced properties tailored to specific application areas. Many commercial examples of two-phase polyblends consist of a matrix polymer impact modified by the addition of rubber particles. Recently, however, TLCPs have received increasing attention in the scientific and technical literature as in situ reinforcements in polymer blends and microcomposites. The matrices examined in the literature include polyimides, PES, PEI, PEEK, polycarbonate, PET, PPS, and polyarylate. 

Figure 4.14 (Top) Dependence of the number average diameter of die rubber particles on the reduced carb(NH2)/MA molar ratio for the 75/25 SAN/EPR polyblend modified by SAN-carb(NH2) of various contents of reactive groups (type a 0.0004, type b 0.028 and type c 0.049 mol/wt% of either NH2 or carbamate) in the SAN phase and 50 wt % EP-g-MA in die EPR phase (bottom) Dependence of the notched Charpy impact strength on the reduced carb(NH2)/MA molar ratio for die 75/25 SAN/EPR polyblends modified by SAN>carb(NH2) of various contents of reactive groups (type a 0.004, type b 0.028 and type c 0.049 mol/wt% of either NH2 or carbamate) in the SAN phase and 50wt% EP-g-MA in the EPR phase. Reprinted with permission from Macromolecules. Copyright (2001) American Chemical Society...

Figure 7.8 [17] shows the relationship between the viscosity ratio of a polyamide-rubber binary blending system and the size of domain particles obtained by mixing and kneading with a twin screw extruder [16-18]. Generally, it is easier to obtain the fine domain size under conditions where the two melt viscosities are close. Furthermore, the domain size reduction easily occurs when the surface tension tt between each polymer particle is low, even if there exists a considerable melt-viscosity difference. This means that both the addition of a compatibilizer or interfacial copolymerization reactions result in lower surface tension and, consequently, the domain size reduction is effectively accelerated. To analyze the domain size in polyblending, the Weber Number Wg or the following modified... 

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