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Departures from the geometric mean assumption for the interaction energy between unlike polymer repeat unit pairs i/j computed from experimental data, were correlated with the molecular connectivity indices for the repeat units. The effects of various factors on the correlation results were investigated. A better correlation is obtained when terms involving the solubility parameters for the repeat...
The phase behavior of blends of S–nBMA copolymers with monodisperse PS homopolymers was studied at three temperatures: 120, 150 and 180 °C. Quantitative evaluation of the binary interaction energy density between styrene (S) and n-butyl methacrylate (nBMA), B S/nBMA , was made at each temperature by analyzing the miscibility data using the copolymer/critical molecular weight method. The temperature...
The phase behavior of blends of SMMA copolymers with other SMMA copolymers of different compositions, with monodisperse PS homopolymers, and with monodisperse PMMA homopolymers was studied using static light scattering to assess the state of miscibility at three different temperatures: 120, 150, and 180°C. Contrary to prior reports, the phase diagrams were found to be consistent with the binary interaction...
Free radical polymerization kinetics of N-vinylformamide was investigated in bulk and in aqueous solution. The molecular weight development with N-vinylformamide conversions was measured using a gel permeation chromatography (GPC). The bulk process showed a typical “gel effect” from the beginning of the polymerization. The molecular weight increased steadily at low conversion and leveled off at high...
When thermoplastics is added as a low-profile additive (LPA) to an unsaturated polyester (UP) resin, microvoids are introduced and compensate for the high volume shrinkage of the resin. The characteristics and mechanisms involved in the microvoid formation of a low-shrinkage UP resin system with poly(vinyl acetate) (PVAc) as LPA were investigated in this work. Both PVAc and styrene were found to play...
This paper describes the rheological properties of a number of aqueous solutions of a poly(vinyl alcohol) (PVA) as a function of the degree of polymer hydrolysis, ambient temperature, pressure and variations induced upon the addition of electrolytes to these solutions. Experimental results reported show that the rheological behaviour of these aqueous PVA solutions mainly depends upon the relative...
We report an experimental investigation on long chain branching (LCB) in ethylene slurry polymerization with bis(cyclopentadienyl) zirconium dichloride (Cp 2 ZrCl 2 )/modified methylaluminoxane (MMAO) using a semi-batch reactor. The effects of the reaction temperature, pressure, MMAO concentration, and catalyst feeding method on the long chain branching density (LCBD, number of branches...
Several types of commercial and developmental aluminoxanes were studied in the semi-batch polymerization of ethylene using bis(cyclopentadienyl) zirconium dichloride (Cp 2 ZrCl 2 ). High temperature gel permeation chromatography (GPC) measurements of polyethylene (PE) formed using various types of aluminoxanes approximated Flory's most probable distribution from a single site-type...
The supercritical fluid extraction of a low polymer using supercritical fluids with a linear density program is modelled. It shows that this density program gives an approximately constant polydispersity in the polymer being extracted at a particular time. Experiments are carried out on the supercritical extraction of polyisobutene and polydimethylsiloxane which show qualitative agreement with the...
A chain copolymerization of macromonomers generates branched polymers with comb structure. This work presents analytical expressions to predict the bivariate distributions of molecular weight and branching density for the comb polymers. The macromonomers are assumed to have a random or uniform distribution. The distribution functions are determined by the average number of branching points per backbone...
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