Elastomer phase diagram

The phase diagram (see Figure 1) shows that there are two solution processes a low-temperature process (below 100 °C) for the production of amorphous copolymers like ethylene/propylene elastomers (EPR or EPM) [2], and a high-tempera-ture process (far beyond 100 °C) for the production of semicrystalline homo- and copolymers like high-density polyethylenes (PE-HD), linear low-density poly-ethylenes (PE-LLD) and ethylene waxes [1, 3]. Polypropylenes (PP) cannot be made in high-temperature solution processes, except for propylene waxes. 

The process of phase separation during cure arises from the change in the phase diagram as the cure reaction of the epoxy resin progresses. This is shown schematically in Figure 1.34 (Pascault et al, 2002) for a system with an upper critical solution temperature (UCST) in which the lower curve represents the system miscible at room temperature, with the fraction cpRo of elastomer corresponding to the initial composition of the rubber-epoxyresin system before any cure reaction has taken place. 

Figure 4.6 Theoretical illustration of a phase diagram for elastomer blends [2].

Four series of IPNs were polymerized, the compositions of which are given in Table 5.2. The underlined polymer was polymerized first. This was always the elastomer PEA (normal IPNs), except for series I (inverse series), where the plastic homopolymer PS or PMMA was polymerized first. The B in PEAB indicates that the PEA contained 1% butadiene as a comonomer to permit staining for electron microscopy. The letters E, L, P, and I denote elastomeric, leathery, plastic, and inverse series, respectively. In compositions containing both S- and MMA-mers, a random copolymer was formed with the indicated composition. The actual compositions employed can be portrayed with the aid of a pseudoternary phase diagram, as shown in Figure 5.1 for the normal IPNs. Only the border compositions (no random... 

In practice, the existence of both UCST and LCST has been established for polymer-solvent systems. About 10 years ago, Schmitt discussed UCST, LCST and combined UCST and LCST behavior in blends of poly(methyl methacrylate) with poly(styrene-co-acrylonitrile) (PMMA-PSAN), Ueda and Karasz reported the existence of UCST in chlorinated polyethylene (CPE) blends using DSC, Inoue found that elastomer blends of cis-l,4-polybutadiene and poly(styrene-co-butadiene) exhibit both UCST and LCST behavior and Cong et al. (72) observed that blends of polystyrene and carboxylated poly(2,6-dimethyl-l,4-phenylene oxide) copolymers with a degree of carboxylation between molar fraction 8% and 10% exhibit both UCST and LCST behavior. They used DSC to establish the phase diagram. 

Fig. 16. Electrostriction of a ferroelectric LC-elastomer (43). Big diagram Thickness variation Ah as a function of the applied ac voltage (/ac- Interferometric data were obtained at the fundamental frequency of the electric field (piezoelectricity, first harmonic -t) and at twice the frequency (electrostriction, second harmonic o). Sample temperature 60°C. Inset Electrostrictive coefficient a (-I-) versus temperature. At the temperature where the non-cross-linked polymer would have its phase transition Sc -Sa (about 62.5 0, the tilt angle of 0° is unstable. That is why the electroclinic effect is most effective at this temperature. An electric field of only 1.5 MV/m is sufficient to induce lateral strains of more than 4%.

Figure 20.3.4. Schematic diagram representing the synthetic process-mixture of components in a heterogeneous solid phase (A), the Udocaine-based DES (B), the lidocaine-loaded prepolymer (C), and elastomer (D), and the lidocaine release based on polymer swelling and degradation [Adapted, by permission, from M.

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