Morphology, crystallinity, and melting behaviour of solution-cast films of poly(ethy1ene oxide) (PEO)/poly(methyl methacrylate) (PMMA) blends were investigated as a function of composition, using optical and scanning electron microscopy, differential scanning calorimetry, and dilatometry. Up to a content of about 40 wt.40 of PMMA the blend films are completely filled with PEO spherulites, no separated domains of PMMA being observed. This observation suggests, in agreement with small angle X-ray scattering analysis, that for such compositions the PMMA molecules are incorporated in interlamellar regions of PEO spherulites. Blends with higher content of PMMA show islands of crystalline PEO within a matrix of PMMA; large amorphous regions coexist with not well developed PEO spherulites. Addition of PMMA strongly increases the nucleation density for PEO crystals. The solubility parameters 6 of PEO and PMMA were calculated from specific volume values as a function of temperature. It was found that at temperatures higher than that of PEO melting the difference 6(PEO) -G(PMMA) is very low suggesting that the two polymers are compatible in the melt. Compatibility of PEO and PMMA was also predicted by using a theoretical approach which allows to calculate the free energy of mixing as a function of composition and temperature.

synopsisThe elastic and structural properties of polybutadiene vulcanized with magnesium methacrylate were investigated. Structural infprmation was obtained by x-ray smallangle diffusion diagrams. Results clearly indicate that in the elastomeric network there is a random distribution of rigid particles. The elastic behavior was analyzed in terms of the Mooney-Rivlii equation. Experimental evidence for the direct correlation between elastic and structural properties is given.

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Samples of cis‐polybutadiene were cross‐linked in the presence of decalin at values of ϕr (the volume fraction of rubber) ranging from 0.25 to 0.50. After the diluent had been removed, a study was made of the force‐extension and thermoelastic behavior of the networks. Within experimental error, the ratio of the Mooney‐Rivlin constants 2C2/2C1 was found to be zero for networks prepared at low ϕr (0.25 and 0.30) but started to increase towards the conventional value at higher ϕr. The quantity fe/f was found to be independent of the ratio 2C2/2C1 and of the extension ratio α; the average value of fe/f was found to be 0.11.

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