Impact-resistant materials block copolymers

A final application is in blends with thermoplastics or other polymeric materials. Styrenic block copolymers are technologically compatible with a surprisingly wide range of other polymers. Blends with many other thermoplastics have improved impact resistance. These block copolymers can also be used as compatibilizers— that is, they can produce useful products from blends of thermoplastics that otherwise have poor properties [6]. 

Thanks to their multiphase constitution, block copolymers have the originality to add advantageously the properties of their constitutive sequences. These very attractive materials can display novel properties for new technological applications. In this respect, thermoplastic elastomers are demonstrated examples (l, 2, 3) they are currently used without any modification as elastic bands, stair treads, solings in the footwear industry, impact resistance or flexibility improvers for polystyrene, polypropylene and polyethylene whereas significant developments as adhesives and adherends are to be noted (5.). 

G. Morales-Balado, R. Flores-Flores, A. Montalvo-Robles, R.E. Diaz De Leon-Gomez, and P. Acuna-Vazquez, Preparation of impact-resistant thermoplastic materials on the basis of styrene/butadiene copolymers with polydisperse blocks, US Patent 7608669, assigned to Dynasol Elastomeros, S.A. De C.V. (Altamire (Tamaulipas), MX), October 27, 2009. 

Some of these block copolymers have improved low temperature impact strength and higher stress-crack resistance than neat BPA polycarbonate Blends. The concept of blending two or more commercially available materials to create a new material having properties different from either starting material has generated a great deal of interest. Polycarbonate blends are used to tailor performance and price to specific markets. 

As block copolymers are still rather expensive materials, it may be advantageous to use them as additives to important industrial polymers. In this domain, possibilities are extremely numerous and diverse. They include an improvement of chemical properties such as resistence to degradation agents, or rheological properties such as adhesion of vinylic paints, high impact properties of conventional thermoplastics, or a compatibilization of polyolefins, polystyrene and poly(vinyl chloride) allowing the reuse of polymeric waste products. The above examples illustrate the great intrinsic potential of block copolymers in the quest of new materials with specific properties. 

Impact modifiers are rubbery additives that improve the resistance of materials. Proper compatibility between the phases is essential. This is often achieved with graft and block copolymers. Most impact modifiers are elastomers such as ABS, BS, methacrylate-butadiene-styrene, acrylic, ethylene-vinyl acetate, and chlorinated polyethylene. 

Study of impact-resistant polymer blends has elucidated the fundamental role of block and graft copolymers (Cop) in a typical system like PS-PI-Cop (I, 2) and also in the case of two-phase materials formed by two resins... 

With both the PEA/P(S-co-MMA) and PB/PS IPN s, an important variable is the ratio of elastomer to plastic in the final material. When the plastic component predominates, a type of impact-resistant plastic results. In this manner the PB/PS IPN s are analogous to the impact-resistant graft copolymers. When the elastomer component predominates, a self-reinforced elastomer results, the behavior resembling that of the ABA-type block copolymers (thermoplastic elastomers) described in Section 4.4. When the overall compositions of both the PB/PS and the PEA/P(S-co-MMA) series are close to 50/50, the materials behave like leathers. 

Polyolefin (PO = PP, HOPE, EPR, or PMP) was blended with an impact modifier, 0.1-5 wt% colorant and/or 5-50 wt% of opadfios, and a styrene-diolefin block copolymer, grafted with 1-6 mol% of acrylic acid, maleic anhydride, or snlftniale functionality (SEBS, SEPS, radial SEB, or SEP). To improve scratch resistance the blend contained 100-3,000 ppm Zn stearate and 16-22C fatty acid amide. The alloys were injection molded into parts showing impact, scratch, and abrasion resistance. They were used to manufacture interior trim for vehicles and in other applications where a scratch- and scuff-resistant plastic material is required ... 

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