Rubber formulation Tear resistance

Blends of polyolefins (e.g., HPDE/LDPE, LDPE/ ethylene copolymers, PP/EPDM, PP/HDPE/EPDM, HDPE/butyl rubber) have been commercial since the late 1960 s and early 1970 s. Specific film formulations were commonly based on polyolefin blends to achieve the proper balance of processing, environmental stress crack resistance, modulus, toughness, cling, transparency, filler acceptance, printability, tear resistance, shrinkage characteristics, and permeability. Ethylene-propylene mbber (EPR, EPDM) was commonly incorporated into polypropylene as an impact modifier at moderate levels and as a flexibilizer at high levels. One of... 

Before World War II (1939-1945) natural rubber was used for practically all rubber applications. Natural rubber is preferred in many products because of its superior building tack, green stock strength, better processability, high strength in non-black formulations, hot tear resistance, retention of strength at elevated temperatures, better resilience, low heat build-up, fatigue resistance, and better dynamic properties. Rubber products are broadly classified as dry rubber products and latex based products [60]. 

The essential ingredients of a free-radical adhesive formulation are an acrylate-terminated prepolymer and a photoinitiator. A wide range of prepolymers can be acrylated, including epoxies, urethanes, polyesters, polyethers, and rubbers. Those most commonly used in adhesive formulations are epoxy and urethane acrylates. Epoxy acrylates have properties similar to those of the parent epoxy resin, with excellent adhesion, chemical resistance, and toughness. Urethane acrylates, on the other hand, are noted for their high reactivity, good adhesion, flexibility, and tear resistance. 

Approximately 95% of the pits are reproduced as holes in the rubber sheet. The holes are not exactly cylindrical in shape but are reinforced by slight constrictions which contribute to strength and tear resistance. This type is referred to as "plain," and can be made with fabric backing on one or both sides to control stretching characteristics. If the unvulcanized material is first stretched, and then vulcanized while stretched, it is called "expanded." Resulting holes are oval and have a higher porosity (sometimes up to 30%). Special compounds have been formulated for resistance to specific chemicals under high concentrations at elevated temperatures, such as 25% sulfuric acid at 180°F. 

Sandstrom and co-workers utilized the cyclized polyisoprene polymers incorporated into tyre tread compounds to improve traction, tread wear and tear resistance. Cyclized polyisoprene is further based upon the discovery that blends of cyclized polyisoprene polymers with halobutyl rubber and/or NR can be employed as tyre inner liner formulations. 

Carbon black or silicas are added to rubber formulations to improve tear resistance and raise the modulus. 

Fillers have been used in the formulation of rubber compounds since the early days of the rubber industry. Whilst their primary function is to reduce cost, it has been found that fillers have a reinforcing effect in the rubber mechanical properties sueh as tensile strength, modulus, tear resistance and abrasion resistanee and thus very few mbber compounds are prepared without substantial quantities of filler. The performance of filler in the rubber matrix is governed by its characteristics, such as the particle size and concentration, particle shape, surface activity, degree of interactions with rubber matrix and structure of the particle agglomerates. 

Compared with similar natural rubber compositions of the same hardness, styrene butadiene rubber (SBR) formulations are characterized by lower tensile strength, elongation, and resilience, lower resistance to tear, flexing, abrasion, ozone, and sunlight, and higher permanent set. The freeze resistance and permeability to gases of styrene butadiene are equivalent to those of comparable natural rubber, and so are the electrical characteristics. 

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