Kazuko Fujiwara

Glass Transition Behaviour of PMMA/PVA Incompatible Blend

Dynamic viscoelastic properties and morphology of poly(methyl methacrylate) (PMMA)/poly(vinyl alcohol) (PVA) blend prepared by melt kneading was investigated. These solubility parameter values differ greatly. Two kinds of PVA with saponification degrees of 88 and 98 mol.% were used. Micrometre-order domains were observed by scanning electron microscopy for 88 mol.% PVA, whereas no clear domain was observed for 98 mol.%. Both the blends were incompatible systems because two loss modulus peaks based on PMMA and PVA were observed by dynamic mechanical analysis. The loss modulus peak based on the PMMA-rich phase was higher than that of pure PMMA; the increase of the corresponding glass transition temperature (Tg) caused by blending was more remarkable for 98 mol.% PVA than 88 mol.%. It was thought that the intermolecular interaction of OH group in PVA and carbonyl group in PMMA caused the increase in Tg, but no clear evidence of the interaction for the blend was observed by a Fourier transform infrared spectroscopic analysis. The poly(vinyl acetate)/PMMA blend was incompatible. The unsaponificated vinyl acetate unit in PVA decreased the interaction between PMMA and PVA. This is the reason why the effect of Tg rising was lower for 88 mol.% PVA than for 98 mol.%.

Surface treatment of CaCO3 with a mixture of amino- and mercapto-functional silane coupling agents and tensile properties of the rubber composites

Abstract In order to reinforce the composite consisting of isoprene rubber (IR) and calcium carbonate (CaCO3) particles, the surface treatment of CaCO3 particles with a mixture of amino- and mercapto-functional silane coupling agents was investigated. The quantity of chemisorbed silanes in treated CaCO3 measured using thermogravimetry was greater for amino- than for mercapto-silane and for the tri- than for the dialkoxy structure. Second, the molecular mobility of polycondensate of the mixtures with the trialkoxy structure measured using 1H pulse nuclear magnetic resonance had the least molecular mobility, i.e., formed the highest density network. The greater values of stress at 500% strain, fracture stress, and elongation at break were determined for the treatment with amino- and mercapto-functional silanes having a trialkoxy structure from the stress-strain curves of composite. The mixture treatment with dialkoxy structure and with amino- or mercapto-functional silane only did not improve the mechanical properties sufficiently. Interactions between the amino group and the CaCO3 surface, covalent bonding between the mercapto group and the IR, and high density network formation of trialkoxy silane were important for improving the mechanical properties of the composite.

Effect of the degree of crosslinking on the interfacial layer structure of poly(vinyl chloride) dispersed with crosslinked poly(n-butyl methacrylate) particles

Abstract The interfacial layer structure of a model incompatible polymer blend system was analyzed using 1H pulse nuclear magnetic resonance (pulse NMR) spectroscopy. Non-crosslinked and crosslinked poly(n-butyl methacrylate) particles with a mean size of ca. 0.9 μm were prepared by seeded emulsion polymerization, and the degree of crosslinking was varied. The particles were powdered using a freeze-dry method and dispersed in poly(vinyl chloride) by melt blending. Dynamic mechanical analysis indicated that the non-crosslinked particles were completely compatible. In contrast, mutual diffusion of the polymer chains in the crosslinked particles was restricted within the particle/matrix interfacial layer. As a result, an incompatible phase structure in which the crosslinked particles were dispersed in the continuous phase was formed. Pulse NMR analysis indicated that the interfacial layer thickness was in the range of 17–98 nm. The thickness decreased with an increase in the degree of crosslinking in the particles. The interfacial layer thickness in the particles was approximately 10 times larger than that for the incompatible polymer pair. Tensile test results indicated that the elongation at break was dependent on the thickness of the interfacial layer. The yield stress was developed for the particles with high hardness that was independent of the interfacial thickness.