Thermoplastic elastomer concentration

Blends of isobutylene polymers with thermoplastic resins are used for toughening these compounds. High density polyethylene and isotactic polypropylene are often modified with 5 to 30 wt % polyisobutylene. At higher elastomer concentration the blends of butyl-type polymers with polyolefins become more mbbery in nature, and these compositions are used as thermoplastic elastomers (98). In some cases, a halobutyl phase is cross-linked as it is dispersed in the polyolefin to produce a highly elastic compound that is processible in thermoplastic mol ding equipment (99) (see Elastomers, synthetic-thermoplastic). ... 

TiCl4 concentration, and blocking time. The star blocks exhibit an excellent combination of thermoplastic elastomer properties. The products exhibited excellent strengths and elongations (up to 27 MPa and 500%), in spite of the presence of 10-15% contaminants. They are potential easily processiable TPEs. 

Processing oil is a well-known additive for rubbers and is commonly employed in PP/EPDM TPVs [10-12]. It lowers the hardness and improves the processability. The oil, in most cases paraffinic oil, can be considered as a low molecular weight olefin. The difference in polarity between the three components is small, and the oil is present in both the PP and in the elastomer phases [67]. In order to understand the mechanical and the rheological properties of olefinic thermoplastic elastomers (OTPEs), the concentration of oil in each phase must be known. 

Block copolymers are widely used industrially. In the solid and rubbery states they are used as thermoplastic elastomers, with applications such as impact modification, compatibilization and pressure-sensitive adhesion. In solution, their surfactant properties are exploited in foams, oil additives, solubilizers, thickeners and dispersion agents to name a few. Particularly useful reviews of applications of block copolymers in the solid state are contained in the two books edited by Goodman (1982,1985) and the review article by Riess etal. (1985). The applications of block copolymers in solution have been summarized by Schmolka (1991) and Nace (1996). This book is concerned with the physics underlying the practical applications of block copolymers. Both structural and dynamical properties are considered for melts, solids, dilute solutions and concentrated solutions. The book is organized such that each of these states is considered in a separate chapter. 

T [Tick] free Tm TMPCl TPE o Glass transition temperature Concentration of free and uncomplexed TiCl4 Melting temperature 2-Chloro-2,4,4-trimethylpentane Thermoplastic elastomer Tensile strength... 

The synthesis, characterization, and mechanical properties of a novel star block copolymer thermoplastic elastomer with eight poly(isobutylene-b-sty-rene) arms radiating from a calix[8]arene was recently reported by Jacob et al. [41]. The process involved the synthesis of eight arm star PIB by a method essentially identical to that described above, followed by sequential addition of S after the IB conversion has reached 95%. To minimize alkylation and to obtain high MW PS blocks, moderate TiCl4 concentration (0.059 mol 1 x) and a 2- to... 

Polysulfide resins combine with epoxy resins to provide adhesives and sealants with excellent flexibility and chemical resistance. These adhesives bond well to many different substrates. Tensile shear strength and elevated-temperature properties are low. However, resistance to peel forces and low temperatures is very good. Epoxy polysulfides have good adhesive properties down to -100°C, and they stay flexible to -65°C. The maximum service temperature is about 50 to 85°C depending on the epoxy concentration in the formulation. Temperature resistance increases with the epoxy content of the system. Resistance to solvents, oil and grease, and exterior weathering and aging is superior to that of most thermoplastic elastomers. 

During the industry s restructuring in the early 1980s, Exxon Chemical sold off most of its specialty petrochemical units to Du Pont and other chemical companies, and concentrated its R D on intermediates and polymers. In the early 1990s product development was accomplished through joint ventures, such as one begun in 1990 with Monsanto to improve thermoplastic elastomers, another in 1992 with Mitsui Petrochemicals for the next generation of ethylene polymer resins, and a third in 1994 with Hoechst to refine... 

While the first efforts [11, 12] of the biotechnological generation of aliphatic homopolyesters and random copolyesters have been restricted essentially on monomers from 3-hydroxybutyric acid (3HB) and 3-hydroxypentanic acid (3HV), newer investigations concentrate on mraiomers with branches in the range of medium chain length, the so-called thermoplastic elastomers [13—15]. Steinbiichel et al. [3] catalogued more than 100 hydroxyalkanoic acids as craistituents of biosynthetic PHAs. 

Commercial BC s are prepared from monomers that upon polymerization yield immiscible macromolecular blocks, one rigid and the other flexible, that separate into a two-phase system with rigid and soft domains. The concentration and molecular weights provide control of the size of the separated domains, thus morphology and the interconnection between the domains. The existence of a dispersed rigid phase in an elastomeric matrix is responsible for its thermoplastic elastomer behavior. For symmetric block copolymers, Leibler [1980] showed that a sufficient condition for microphase separation is (%abN) = 10.5, where binary thermody-... 

The EP thermoplastic elastomers are distinguished from the crossUnked analogues, which are not thermoplastics since reforming is impossible. A very important thermoplastic elastomer is comprised of a blend of an EP copolymer with an ethylene-propylene-diene (EPDM) terpolymer. This latter material is, of course, a crosslinkable thermoset however, these materials can be processed as thermoplastics if the crosslinkable component is present at low enough concentration to be present as an isolated phase. Melt-processing causes the formation of chemical bonds within the isolated rubber phase, a process called dynamic vulcanization. A commercial example of this type of material is Santoprene [4] manufactured by Advanced Elastomer Systems. Other blends of noncrosslinkable TPEs with crosslinkable materials are used commercially. These materials are classified as elastomer blends and are the subject of Chapter 12. 

Block polymers and polymer blends deserve now a great intere because of their multiphase character and their related properties. The thermodynamic immiscibility of the polymeric partners gives rise indeed to a phase separation, the extent of which controls the detailed morphology of the solid and ultimately its mechanical behavior. The advent of thermoplastic elastomers and high impact resins (HIPS or ABS type) illustrates the importance of the industrial developments that this type of materials can provide. In selective solvents, and depending on molecular structure, concentration and temperature, block polymers form micelles which influence the rheological behavior and control the morphology of the material. 

Samples with concentration of rr defects in the range 7-11% are thermoplastic elastomers with high strength. For these samples, the 7 form present in unstretched films (Fig. 17.2e,f) transforms by stretching into the a form, which, in turn, transforms into the mesomorphic form at very high defor-... 

Fig. 17.15. Classification of i-PP samples prepared with different catalysts, as stiff-plastic materials, fiexible-plastic materials, and thermoplastic elastomers depending on concentration of rr defects of stereoregulaiity and Young s modulus (E)...

Figure 9.7 Flexural modulus versus filler concentration in a thermoplastic elastomer, TPO comparison of talc (CA53) with nanoclay (CA53-15A) in the presence of maleated PP (PB3200).

This study concentrated on the effect of carbon black on the characteristics of the thermoplastic elastomers. Figure 5 shows the shear viscosity behavior of three triblock copolymers. The figure also shows the shear thinning behavior of polymers. In the case of carbon black-filled polymers, the slopes are more sharply increased than are those of the raw polymers, and the viscosity increase by carbon black is greater than the values predicted theoretically by Equation 7. The viscosity of SEBS is higher than that of the other polymers. This is apparently attributed to the large segmental incompatibility of SEBS, as previously stated. The addition of carbon black to the raw polymers is frequently induced to increase the viscosity. The reason is that the carbon black particles within the polymer increase the fluid friction. 

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