Toughness properties

Reportedly, OjoCdiaHylbispheaol A is an attractive comonomer for bismaleimides because the corresponding copolymer is tough and temperature resistant (41). Toughness, however, is a function of the BMI—diaHylbisphenol A ratio employed. In one study optimized toughness properties were achieved when BMI and diaHylbisphenol were employed at a close to 2 1 molar ratio (42). In Table 9, the mechanical properties of BMI—bis(3-allyl-4-hydroxyphenyl)-7 -diisopropylbenzene resias are provided, showiag optimized properties for the 60/40 BMI—diaHylbisphenol composition. The 0,(9 diaHylbisphenol A is commercially available under the trademark Matrimide 5292. Another bisaHylphenyl compound is available from SheH Chemical Company/Technochemie under the trademark COMPIMIDE 121. 

An example of this improvement in toughness can be demonstrated by the addition of Vamac B-124, an ethylene/methyl acrylate copolymer from DuPont, to ethyl cyanoacrylate [24-26]. Three model instant adhesive formulations, a control without any polymeric additive (A), a formulation with poly(methyl methacrylate) (PMMA) (B), and a formulation with Vamac B-124 (C), are shown in Table 4. The formulation with PMMA, a thermoplastic which is added to modify viscosity, was included to determine if the addition of any polymer, not only rubbers, could improve the toughness properties of an alkyl cyanoacrylate instant adhesive. To demonstrate an improvement in toughness, the three formulations were tested for impact strength, 180° peel strength, and lapshear adhesive strength on steel specimens, before and after thermal exposure at 121°C. 

Acrylonitrile-butadiene-styrene (ABS). ABS materials have superior strength, stiffness and toughness properties to many plastics and so they are often considered in the category of engineering plastics. They compare favourably with nylon and acetal in many applications and are generally less expensive. However, they are susceptible to chemical attack by chlorinated solvents, esters, ketones, acids and alkalis. 

Poly(2,6-dimethyl-l,4-oxyphenylene) (poly(phenylene oxide), PPG) is a material widely used as high-performance engineering plastics, thanks to its excellent chemical and physical properties, e.g., a high 7 (ca. 210°C) and mechanically tough property. PPO was first prepared from 2,6-dimethylphenol monomer using a copper/amine catalyst system. 2,6-Dimethylphenol was also polymerized via HRP catalysis to give a polymer exclusively consisting of 1,4-oxyphenylene unit, while small amounts of Mannich-base and 3,5,3, 5 -tetramethyl-4,4 -diphenoquinone units are always contained in the chemically prepared PPO. 

TRITIUM AGING EFFECTS ON THE FRACTURE TOUGHNESS PROPERTIES OF FORGED STAINLESS STEEL... 

Tritium Aging Effects on the Fracture Toughness Properties of Forged Stainless Steel... 

The purpose of this study was to measure and compare the fracture toughness properties of Type 21-6-9 stainless steel for high-energy-rate and conventional forgings in the unexposed, hydrogen-exposed and tritium-exposed-and-aged conditions. 

M. J. Morgan and M. H. Tosten, Tritium and Decay Helium Effects on the Fracture Toughness Properties of Types 316L, 304L, and 21Cr-6Ni-9Mn Stainless Steels , Hydrogen Effects in Materials, ed. A. W. Thompson and N. R. Moody, (Warrendale, PA TMS, 1996), p. 873. 

Copolymers. Mixtures of two or more different bifunctional monomers can undergo additional polymerization to form copolymers. Why copolymerize Well, polymers have different properties that depend on their composition, molecular weight, branching, crystallinity, etc. Many copolymers have been developed to combine the best features of each monomer. For example, polystyrene is low cost and clear, but it is also brittle with no toughness. It needs internal plasticization. By copolymerizing styrene with a small amount of acrylonitrile or butadiene, the impact and toughness properties are dramatically improved. 

In another study, optimized toughness properties were achieved when BMI and diallylbisphenol were employed at about 2 1 molar ratio (68). In Table 7,... 

Padture, N.P. and Lawn, B.R. (1994), Toughness properties of a silicon carbide with an in situ induced heterogeneous grain structure , J. Am. Ceram. Soc., 77(10), 2518-22. 

Thermal-Mechanical Criteria. The thermal and mechanical properties must not be degraded. The toughness properties (crack and impact resistance) must be improved, and the system should be rather insensitive to the rate of loading (or temperature) of a given test. 

The block copolymers by themselves also have very attractive toughness properties. In them crazing occurs through another mechanism involving internal cavitation of the rubber block domains. 

By association of mineral particles with different size (0,1 pm, and 2 pm), a synergy effect can be developed. These results show that it is possible to develop thermoplastic materials with a high modulus and also good fracture toughness properties by using mineral fillers. 

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