Ethylene-propylene rubbers blends with plastics

In rubber-plastic blends, clay reportedly disrupted the ordered crystallization of isotactic polypropylene (iPP) and had a key role in shaping the distribution of iPP and ethylene propylene rubber (EPR) phases larger filler contents brought about smaller, less coalesced and more homogeneous rubber domains [22]. Clays, by virtue of their selective residence in the continuous phase and not in the rubber domains, exhibited a significant effect on mechanical properties by controlling the size of rubber domains in the heterophasic matrix. This resulted in nanocomposites with increased stiffness, impact strength, and thermal stability. 

A comparatively new group of materials— thermoplastic elastomers or thermoplastic rubbers —combines the ease of processing of thermoplastics with qualities of traditional vulcanized rubbers, especially elasticity. Because of convenience in processing there is much interest too in blends of plastics with elastomers, which may be modified by the inclusion of filler or glass fibre. As an example, a rubber-like material that can be processed as a thermoplastic can be made by blending and melt-mixing an ethylene-propylene rubber with polypropylene. The use of such blends may be helpful when there are needs to reclaim and re-process material, and in order to obtain products with qualities intermediate between those of the main components of the blends. 

Figure 9.11 Dimensionless droplet size (capillary number) as a function of viscosity ratio M for various blends of 15 wt% ethylene-propylene rubbers in nylon or polyester produced by ex-trusion at an effective shear rate of around 100 sec The components are shear thinning, and the viscosity ratio M is evaluated at the effective shear rate. (From Wu 1987, reprinted with permission from the Society of Plastics Engineers.)...

Adhesive applications can be widespread including contact cmnents, pressure-sensitive adhesives and hot melts. In solid compounded articles footwear is a large volune application such as molded-ln-place soling or unit soles to be cemented to uppers. Additional uses are in toys, milk tubing, cove base, mats and miscellaneous coatings or molded parts. Potential uses include blends with ethylene-propylene rubber and ethylene-vinyl acetate copolymers to provide ozone-resistant fomulations or blends to improve crack- or impact-resistance of plastics. 

This class of TPEs consists of blends of the thermoplastic PP with an unvulcanized ethylene propylene rubber/elastomer. May contain smaller amounts of other materials, for example, HDPE, plasticizers and carbon black. 

Elastomers, plastics, fabrics, wood and metals can be joined with themselves and with each other using nitrile rubber/epoxy resin blends cured with amines and/or acidic agents. Ethylene-propylene vulcanizates can also be joined using blends of carboxylated nitrile rubber, epoxy resin and a reactive metal filler (copper, nickel, cobalt). However, one of the largest areas of use of nitrile rubber modified epoxy systems is in the printed circuit board area [12]. 

A significant development is the appearance of supertough nylon plastics, which are blends in nylon-6,6 with other resins, such as an ionomer resin used in the initial grades or a modified ethylene-propylene-diene terpolymer rubber (EPDM rubber) used in later grades. 

The Tg of an ethylene-propylene copolymer rubber is — 50 C. When the EPR is blended with PA6.6, the fracture resistance of the blend in slow bending tests on notched bars, first shows a significant increase at — 50 C. In this test, the time taken to reach peak load is Is. Toughening occurs when the rubber particles have time to stress relax and to initiate plastic deformation in the PA6.6 matrix. Calculate the minimum temperature required to achieve toughening in the Charpy impact test. Use the WLF equation,... 

Several flexible polymers, such as natural rubber (NR) synthetic rubber (SR) polyalkyl acrylates copolymers of acrylonitrile, butadiene, and styrene, (ABS) and polyvinyl alkyl ethers, have been used to improve the impact resistance of PS and PVC. PS and copolymers of ethylene and propylene have been used to increase the ductility of polyphenylene oxide (PPO) and nylon 66, respectively. The mechanical properties of several other engineering plastics have been improved by blending them with thermoplastics. 

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