Rubber elasticity thermoplastic

Coran and Patel [33] selected a series of TPEs based on different rubbers and thermoplastics. Three types of rubbers EPDM, ethylene vinyl acetate (EVA), and nitrile (NBR) were selected and the plastics include PP, PS, styrene acrylonitrile (SAN), and PA. It was shown that the ultimate mechanical properties such as stress at break, elongation, and the elastic recovery of these dynamically cured blends increased with the similarity of the rubber and plastic in respect to the critical surface tension for wetting and with the crystallinity of the plastic phase. Critical chain length of the rubber molecule, crystallinity of the hard phase (plastic), and the surface energy are a few of the parameters used in the analysis. Better results are obtained with a crystalline plastic material when the entanglement molecular length of the... 

Kikuchi Y., Eukui T., Okada T., and Inoue T. Origin of rubber elasticity in thermoplastic elastomers consisting of crossUnked rubber particles and ductile matrix, J. Appl. Polym. Sci., Appl. Polym. Symp., 50, 261, 1992. 

A wide variety of such topics are covered in this book. Most of the chapters are from papers presented at a symposium held in August 1981. This symposium was preceded by a half-day tutorial session, with corresponding introductory review articles on synthesis of elastomers by G. Odian and rubber elasticity by J. E. Mark (published in the November 1981 issue of the Journal of Chemical Education). To aid the reader, a brief review of thermoplastic elastomers is included in this book. 

Example 5-23) and of ABS-polymers (made from acrylonitrile, butadiene, and styrene), whereby grafting occurs in situ at the beginning of the polymerization process. The formed graft copolymers act in two ways As emulsifiers during the polymerization process and, secondly, in the solid end product as compatibilizer between the thermoplastic hard phase and the rubber-elastic dipersed phase (already in concentrations below 3%). 

Unlike simple mixtures of polystyrene and polybutadiene such blends can be thermoplastically processed without phase separation ( splicing ) Furthermore, they can to a certain extent withstand mechanical impact without disintegration. This is because the above-mentioned graft polymers function also as compatibilizer at the borderline of the hard phase and the rubber-elastic dispersed phase (already at concentrations below 3%). 

As a result of its saturated polymer backbone, EPDM is more resistant to oxygen, ozone, UV and heat than the low-cost commodity polydiene rubbers, such as natural rubber (NR), polybutadiene rubber (BR) and styrene-butadiene rubber (SBR). Therefore, the main use of EPD(M) is in outdoor applications, such as automotive sealing systems, window seals and roof sheeting, and in under-the-hood applications, such as coolant hoses. The main drawback of EPDM is its poor resistance to swelling in apolar fluids such as oil, making it inferior to high-performance elastomers, such as fluoro, acrylate and silicone elastomers in that respect. Over the last decade thermoplastic vulcanisates, produced via dynamic vulcanisation of blends of polypropylene (PP) and EPDM, have been commercialised, combining thermoplastic processability with rubber elasticity [8, 9]. 

Modification of thermoplastics to achieve high-impact resistance —> Blending with rubber elastic components... 

The polyvinylethers form a further group of thermoplastics which are not used as containers or packaging films. They are atactic polymers forming oils, sticky soft resins or nonsticky rubber elastic materials according to their molecular weight and composition. All polyvinylethers are very resistant to saponification by dilute acids and alkalis. They can subsequently be used as unsaponifiable polymer plasticizers and for the manufacture of glues. 

It will be shown in Chapter 11 that the correlations developed in this monograph can be combined with other correlations that are found in the literature (preferably with the equations developed by Seitz in the case of thermoplastics, and with the equations of rubber elasticity theory with finite chain extensibility for elastomers), to predict many of the key mechanical properties of polymers. These properties include the elastic (bulk, shear and tensile) moduli as well as the shear yield stress and the brittle fracture stress. In addition, new correlations in terms of connectivity indices will be developed for the molar Rao function and the molar Hartmann function whose importance in our opinion is more of a historical nature. A large amount of the most reliable literature data on the mechanical properties of polymers will also be listed. The observed trends for the mechanical properties of thermosets will also be discussed. Finally, the important and challenging topic of the durability of polymers under mechanical deformation will be addressed, to review the state-of-the-art in this area where the existing modeling tools are of a correlative (rather than truly predictive) nature at this time. 

There has been the question why the TPV materials with ductile thermoplastic matrix display rubber elasticity. Several models have been suggested to answer this question (41 7). Inoue group first analyzed the origin of mbber elasticity in TPVs (43). They constructed a two-dimensional model with four EPDM mbber inclusions in ductile PP matrix and carried out the elastic-plastic analysis on the deformation mechanism of the two-phase system by finite-element method (FEM). The FEM analysis revealed that, even at highly deformed states at which almost the whole matrix has been yielded by the stress concentration, the ligament matrix between mbber inclusions in the stretching direction is locally preserved within an elastic limit and it acts as an in-situ formed adhesive for interconnecting mbber particles. 

TPE are rubber-elastic at temperatures from 20 °C to -1-120 °C (assuming no major deformations), but show thermoplastic behavior in the melting range (160-180 °C). 

Lai J, Mark JE (eds) (1986) Advances in elastomers and rubber elasticity. Plenum, New York Legge NR, Holden G, Schroeder HE (eds) (1987) Thermoplastic elastomers. Hanser, Munich Lewis RJ (1999) Sax s dangerous properties of industrial materials, 10th edn. Wiley, New York Mark JE, Bikales NM, Overberger CG, Menges G (eds) (2004) Encyclopedia of polymer science and engineering, vol 1-12. Wiley, New York... 

Dynamically vulcanized, elastomeric thermoplastic alloys or TPVs display properties as good as or even better than the block copolymers, viz., a high degree of rubber elasticity yet good melt processability. The main advantages of the thermoplastic vulcanizate elastomer blends over the uncured thermoplastic/elasto-mer blends are... 

The above selective cross-linking of acrylate rubbers in a polyamide thermoplastic matrix leads to a PA-acrylate rubber-blend TPV with the melt-processing advantages of the PA and the high-performance properties of a thermoset acrylate rubber. The PA matrix provides the high heat resistance and solvent resistance while the cross-linked polyacrylate provides the rubber elasticity coupled with its own excellent weatherabdity and oil resistance properties to the TPV. 

Polyurethanes are versatile polymers typically composed of polyisocyanates and polyols. By varying constituents, a broad range of thermosets and thermoplastics can be produced and used in different applications. Possible systems include high-strength, high-modulus, structural composites soft rubbers elastic fibers and rigid or flexible foams. Although isocyanates have the ability to form many different polymers, very few types are used in actual production. The most common diisocyanates are methylene diphenylene diisocyanate (MDI) and toluene diisocyanate (TDI). Of these, TDI is the most commercially important dimer. 

Kikuchi, Y., Fukui, T., Okada, T. and Inoue, T. (1991) Elastic-plastic analysis of the deformation mechanism of PP-EPDM thermoplastic elastomer Origin of rubber elasticity. Polymer Engng Sci., 31, 1029-1032. 

Linear Elastic and Rubber Elastic Behavior. Although stiffening is quite noticeable in the glassy regime of the amorphous phase, the most spectacular effect is seen in the rubber elastic regime phase, as already evoked in the case of reinforcement by cellulose whiskers (2). The PA6-clay hybrids example presented in Table 3 is quite representative of the situation encoimtered with semi crystalline thermoplastics, but elastomeric networks benefit as well of clay layer dispersion with a two- to threefold increase in modulus for polyurethane or epoxy networks... 

---