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An investigation was carried out into the effect of amine/epoxy stoichiometry and thermal history during cure on physical and mechanical properties of epoxy networks. The formulation studied consisted of a diglycidyl ether of bisphenol A epoxy resin and 4,4 -diaminodiphenyl sulfone curing agent. The experimental matrix was based upon three amine/epoxy ratios and seven different thermal histories...
A Co(II) chelate membrane from a poly(vinyl alcohol)/poly(allyl amine) blend was synthesized. As an intermediate step the blend membrane was modified to a Schiff-base type. Structures of blend and Schiff-base membrane were confirmed by the FTi.r. subtraction method. Differential scanning calorimetry thermograms of blend and Schiff-base membranes showed that the glass transition temperature (T ...
The phase behaviour of binary blends of styrene-methacrylonitrile (SMAN) copolymers and methyl methacrylate copolymers with cyclohexyl methacrylate and t-butyl methacrylate has been determined as a function of composition of each copolymer at 130, 150 and 180°C. These miscibility maps are compared with those of recently reported blends of styrene-acrylonitrile (SAN) copolymers with methacrylate copolymers...
The mechanism of phase separation of sol-gel alkoxy-derived silica systems obtained by acid catalysis in the presence of poly(methyl methacrylate) (PMMA) and tetrahydrofuran was investigated by light scattering. Spinodal decomposition (SD) was confirmed for systems with intermediate PMMA/alkoxy compositions occurring with a simultaneous viscosity increase. The initial stages of phase separation...
High-density polyethylene (HDPT) specimens were obtained by standard extrusion and also by a procedure of solidification from a highly deformed melt (Sodem) in wide ranges of temperature T, time t, and draw ratio λ from 1.0 to 12.2. Tensile tests were conducted isothermally between 20 and 120°C and stress relaxation at constant tensile strain studied as a function of time also isothermally at several...
Sonication of a non-ionic polymerizable chlosterol-based amphiphile, 1-ethenyl-3-(8-(cholest-5-en-3β-yloxy)-3,6-dioxaoctyl)-2-pyrrolidone, in water resulted in the formation of bilayer vesicles. The vesicle formation was evidenced by transmission electron microscopy and [ 14 C] sucrose entrapment. Polymeric vesicles, prepared by polymerization in the bilayer, showed increased stability.
A polyfunctional arylacetylenic monomer, 1,2,4-tris(phenylethynyl)benzene, thermally polymerizes by a free-radical mechanism to a highly crosslinked structure of interest as a precursor matrix for carbon/carbon composites. The polymerization reaction was characterized by Fourier transform infra-red spectroscopy and differential scanning calorimetry (d.s.c.). The disappearance of the acetylenic stretching...
Blends of poly(ethylene terephthalate) (PET)/poly(ethylene-co-ethyl acrylate) were found to have good mechanical properties when melt-mixed at optimum conditions, i.e. at 290°C for 25 min. Characterization studies based on tensile testing, dynamic mechanical analysis, differential scanning calorimetry and Fourier transform infra-red spectroscopy of blend extracts and morphological evidence using...
This paper deals with experimental and theoretical investigations on the compatibility of binary polymer blends in solution. The experimental phase boundary of a crystalline polymer such as poly(vinylidene fluoride) with polystyrene (an amorphous polymer) in dimethylformamide as solvent has been determined by size-exclusion chromatography at 25°C. The composition of the coexisting phases has been...
Poly(N-isopropylacrylamide) (PNIPAM) was synthesized by free-radical polymerization. High resolution n.m.r. was used to confirm its chain composition and linear chain configuration. The solution properties of both unfractionated and fractionated PNIPAM samples in THF and water at 20°C were investigated by laser light scattering (LLS). Owing to its polyelectrolyte nature, it is extremely difficult,...
The combinatory entropy in the ternary solution of crystalline polymers (2), with n c rod-like parts and c segments per part, with solvent (1) and holes (0) has been derived based on the Flory-Huggins theory, which is given by:S P-S-H /R = (φ 2 /r)ln{[z - 1)/e] m-1 m} - φ 0 ln φ 0 - φ 1 ln φ 1 -...
The statistical and kinetic aspects of exchange reactions between a polyarylate and poly(butylene terephthalate) are considered. This theoretical approach enables us to calculate the average sequence length, the degree of randomness and the values of the kinetic parameters as a function of temperature and catalyst concentration from triad determination by n.m.r. spectroscopy.
Molecular processes in large uniaxial stretching of amorphous polyethylene are studied by molecular dynamics simulation. An initial isotropic amorphous sample nearly free from internal strain is made at 200 K with the aid of Monte Carlo chain generation followed by relaxation of residual strain by the molecular dynamics simulation. The initial sample is cooled to 100 K, and then subjected to a uniaxial...
The results of experiments with a supported Ziegler-Natta catalyst were interpreted by a two-site model of the active sites, in order to enhance the understanding of multiple types of catalyst active sites and in particular the role of the external donor. The applicability of the two-site model is discussed and the stochastic parameters of the model are correlated with both the experimental and molecular...
Molecular dynamics (MD) simulations have been used to study the diffusion of methane as a small molecule penetrant example in cis-1,4-polybutadiene (PBD). The non-bonded potential for an anisotropic united atom (AUA) representation of the -CH group was calibrated by adjusting the constants to fit experimental volume temperature data for the polymer melt. This potential was used along with...
A series of model unsaturated polyesters derived from maleic anhydride and various diols were synthesized and a study of their structures was carried out by means of 13 C n.m.r. spectroscopy. The n.m.r. spectra of polyesters produced by different procedures are reported and interpreted in terms of variety in the arrangement of diol components. Both fumarate and ester carbon atoms were...
A spin-labelled poly(octyl isocyanate) has been synthesized by copolymerizing a nitroxide radical having an isocyanate function, with n-octyl isocyanate. The electron paramagnetic resonance spectra of the labelled polymer in various solvents are sensitive to the local conformation and flexibility of the polyisocyanate chain. The motion of the label is less restricted in a polar solvent (chloroform)...
Simultaneous measurements of stress relaxation and differential dynamic modulus were made at 20°C for polyisobutylene in large shearing deformations on which intermittent small oscillations were superposed perpendicularly. Static shear strain varied from 0.1 to 1.0 while the frequency of the superposed oscillations was 0.1 Hz, which falls in the middle of the plateau zone of the polymer. The strain...
The photophysical behaviour of benzophenone (BP) in poly(methyl methacrylate) (PMMA) has been studied as a function of temperature. Time-resolved phosphorescence data reveal that at no temperature between 77 and 420 K can the decay behaviour of the triplet state of BP in PMMA be described adequately by a single exponential function. This contrasts with the phosphorescence behaviour of BP in low temperature,...
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