Toughened thermoplastics

Block copolymers have become commercially valuable commodities because of their unique stmcture—property relationships. They are best described in terms of their appHcations such as thermoplastic elastomers (TPE), elastomeric fibers, toughened thermoplastic resins, compatibilizers, surfactants, and adhesives (see Elastot rs, synthetic—thermoplastic). 

Block copolymers possess unique and novel properties for industrial applications. During the past 20 years, they have sparked much interest, and several of them have been commercialized and are available on the market. The most common uses of block copolymers are as thermoplastic elastomers, toughened thermoplastic resins, membranes, polymer blends, and surfactants. From a chemist s point of view, the most important advantage of block copolymers is the wide variability of their chemical structure. By choice of the repeating unit and the length and structure of both polymer blocks, a whole range of properties can be adjusted. 

Hourston, D. J., Lane, S. and Zhang, H. X., Toughened thermoplastics Part 2 impact properties and fracture mechanisms of rubber modified PBT, Polymer, 32, 2215-2220 (1991). 

Deyrup, E. J., Toughened thermoplastic polyester compositions, US Patent 4 753 980 (to DuPont Company, Wilmington, DA), 1988. 

Chorvath I et al. (2001) Silicone rubber-toughened thermoplastic resin composition. WO Patent 2001018 116... 

Precrosslinked particles with low crosslink density exhibit elastic properties and ean be applied for toughening thermoplastics or thermosets. The size of the elastic domains in blends consisting of elastic particles and a polymer matrix can be adjusted precisely, provided that the particles are dispersible. Via functional groups, microparticles can be covalently attaehed to a (thermoset) matrix. The grafting of polymer shells onto elastic microparticles improves the compatibility with the polymer matrix to be modified [3]. Thus, after processing of the polymer alloy discrete elastic particles can be observed as disperse phase in a continuous thermoplastic matrix. 

Aciylonitrile-butadiene-styrene (ABS) copolymer, an important rubber-toughened thermoplastic, is widely used owing to its favorable cost/performance ratio. The advantages of ABS include its luster and resistance to impact [1-2]. ABS is therefore used in various instruments and structures for small elemental parts as well as large structural ones. In spite of... 

Keywords rubber-toughened thermoplastic glass fibre ternary blends mechanical tests fracture toughness J-integral image analysis fractographic observations acoustic emission. 

One way of overcoming this is to have the second phase already separated before cure, i.e. the toughener is insoluble in the epoxy resin before cure. Examples are found in toughened thermoplastics, where core-shell particles that optimize adhesion and compatibility and have a particle-size distribution to maximize toughness have been synthesized. These particles can be added at the desired volume fraction to achieve toughness without compromising performance rather than relying on the phase trajectory to achieve the desired... 

Investigations of Micromechanical and Failure Mechanisms of Toughened Thermoplastics by Electron Microscopy... 

The distinguishing feature of the A-B-A thermoplastic elastomer structure is that a three-dimensional network is established by the dispersed domains serving as cross-link junctions of high functionality (see Figure 1). With Increase of the proportion of A, the stress-strain response changes and successively approximates that of a nonreinforced vulcanizate, a reinforced vulcanlzate, a flexible thermoplastic, and a toughened thermoplastic. 

Linear elastic fracture mechanics studies on toughened brittle plastics at room temperature concentrated on thermosetting resins, which have sufficiently high yield stresses to meet the requirements of Eq. 12.7. There has been increasing emphasis on ductile fracture mechanics in testing the toughened thermoplastics. An alternative approach is to determine the parameter, Jj, which is the quantity corresponding to Gj in linear elastic fracture mechanics, as discussed below. 

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