High-molecular-weight rubber

HCR heat-cured rubber HMWR high-molecular-weight rubber... 

Recently Nitto Denko developed a battery separator made by a wet process that had high puncture strength and high heat rupture resistance. They used a polyolefin resin with a high-molecular-weight rubber as its main component materials and cross-linked through oxidation in air. The melt rupture temperature, as measured by thermomechanical analysis, was over 200°C in this material. They also tried cross-linking UHMWPE with electron-beam and ultraviolet irradiation, but this had the... 

However, dispersion of high-molecular weight rubbers into the monomeric or prepolymer mixtures of the thermosetting resin matrix is usually difficult due to a viscosity mismatch and a lack of solubility or compatibility. 

Thus, in brief, a successful pressure-sensitive adhesive not only has low resistance to small strain deformation in order to facilitate wetting, but also it can resist large strains without flowing apart easily. Certain neat elastomers such as acrylate-based PSAs possess these features and are intrinsically tacky without additives. Other PSAs are formulated by diluting high molecular weight rubbers with special resins called tackifiers. 

Modern guayule is farmed as a biennial crop with repeated harvests of the same plants. The high molecular weight rubber present in the root and stem base latex sample [Table 5 (12)] indicates that the high 5delding, last harvest of shrub, when a stand is dug in order to replant a new line, also will be of high quality. Film tests of latex purified from stems and roots confirmed high performance characteristics (unpublished data). 

These factors show that compounds suitable for use in oil fields are difficult to produce because they have to be based on high molecular weight rubbers and highly reinforcing fillers. Unfortunately, such compounds have undesirable higher compression set values. 

High molecular weight rubbers are the best choice for strength at high temperatures. 

In practice zinc and calcium peroxides are also widely used with the high molecular weight rubbers ... 

Another procedure for preparing polymer blends involves in-situ polymerization. In many cases, the polymerization of one polymer is conducted in the presence of the other polymer. Impact polystyrene and ABS are typically prepared by polymerization of styrene or styrene-acrylonitrile in the presence of a high molecular weight rubber. Polyolefin blends can be made by the sequential polymerization of compositionally differing polyolefins (e.g., PP/EPR) or by the simultaneous polymerization of polyolefin variants with multiple catalyst systems. 

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