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High-density and low-density polyethylene (HDPE and LDPE) were melt-blended with the intent of building a morphological model from the unit cell level as a function of weight content and heat treatment. The compression-moulded sheets were slowly and rapidly cooled to compare the extremes in crystallization conditions. Based on the d-spacings, there is no apparent distortion on the unit cell level...
Poly(ethylene terephthalate) and poly(butylene terephthalate) homopolymers and mixtures of these two polymers have been heated in the absence of oxygen at 573 K for 30 min and 476 K for 6 h. The resultant polymers have been analysed using solution viscometry, d.s.c., density determination and 13 C n.m.r. Degradation has been observed when the polyesters are heated at 573 K and this...
Copolymers of 4-vinylpyridine and N-alkylacrylamides (alkyl chain bearing 6, 10 and 12 carbon atoms) were prepared by bulk free radical copolymerization using 2,2 -azobisisobutyronitrile and 2,2 -azobis(2,4-dimethylvaleronitrile) as initiators. Poly(N-alkylacrylamide-co-4-vinylpyridine)s were then converted into cationic copolymers by quaternization of the pyridine rings with methylbromide. Their...
A thermo-optical analysis technique is used to obtain cloud-point curves of binary monodisperse polymer/solvent systems containing polystyrene (PS), poly(α-methylstyrene) (PMS) and poly(styrene-co-α-methylstyrene) (PSMS) random copolymer having 20 mol% styrene. Solvents include cyclohexane, cyclopentane, trans-decalin, n-butyl acetate, n-pentyl acetate and n-hexyl acetate. The systems studied in...
Imide ring formation upon heat treatment of diacylated diamines and dianhydrides was shown to be highly efficient. Evidence to support this conclusion was obtained from thermal gravimetric analysis, differential scanning calorimetry and infra-red spectroscopy. Equimolar mixtures of diacylated diamines and dianhydrides form eutectic mixtures, which quantitatively eliminate the corresponding acid...
Short-length polymers selectively end-capped with a metal carboxylato group at both ends, i.e. metal carboxylato-telechelic polymers, exhibit an unusual shear-thickening behaviour in apolar solvents, depending on the main experimental parameters that control the ion-pair association, such as metal cation, concentration and temperature. In contrast to the non-ionic precursors, metal carboxylato-telechelics...
Wide-angle X-ray scattering studies of Bivoltine silk fibres have been carried out to obtain the crystal size distribution along the [201] direction. The minimum enthalpy for the formation of fibres has been estimated. The crystal size varies with annealing temperature, the values of g and a * remaining almost constant, which is a unique feature of Bivoltine silk fibre. Using paracrystalline...
Neglecting turbidity leads to an overestimation of the second virial coefficient in light scattering experiments. Although this effect is totally negligible for polymers in good solvents, it is dominant for systems consisting of large compact particles and for polymers at theta conditions. The turbidity correction is proportional to the characteristic constant of light scatterning K and thus inversely...
Copolymer AX-co-MMA (1) of S-acryloyl O-ethyl xanthate (AX) and methyl methacrylate (MMA) was prepared and employed as a soluble macrophotoinitiator for the polymerization of MMA. The photoinitiation efficiency of AX-co-MMA was compared with that of S-acetyl O-ethyl xanthate (2) which is a low molecular weight photoinitiator. The kinetic parameters of polymerization, initiator efficiency ( ) and...
New fluoroalkylated allyl- and diallylammonium chloride oligomers with carbon-carbon bond formation have been prepared by the oligomerization of allylammonium chloride and the cyclo-oligomerization of diallylammonium chloride by the use of fluoralkanoyl peroxides, respectively. These obtained fluoroalkylated cationic oligomers were able to reduce the surface tension of water to around 10 mN m ...
This study developed Kuhn-Mark-Houwink-Sakurada (KMHS) equations for kraft lignin, based on the absolute molecular weight characterized with low-angle laser light scattering. The KMHS exponential factors of kraft lignin were found to be 0.11, 0.13 and 0.23 in dimethylformamide (DMF) at 318.2 K, in DMF at 350.7 K and in 0.5 N sodium hydroxide at 303.2 K, respectively. Lignin molecules in solution...
A new approach to estimate conversion and copolymer composition in semicontinuous emulsion copolymerization systems based on calorimetric measurements was developed. The proposed approach was checked for two different monomer systems: butyl acrylate-styrene and vinyl acetate-butyl acrylate. The estimated values of conversion and copolymer composition obtained from calorimetric data were compared...
Blends of polychloroprene (CR) and epoxidized natural rubber (ENR) are crosslinked during high temperature moulding for a prolonged time. As studied by dynamic mechanical spectroscopy, the 30 CR/ENR-50 blend is miscible and its miscibility is unaffected by the incorporation of high abrasion furnace carbon black filler. The 50 CR/ENR-50 blend is miscible, but its miscibility is adversely affected...
In this work, a theoretical approach based on diffusion and the Flory-Huggins theory of the free energy of mixing is considered to predict the weld-line strength in injection-moulded polycarbonate (PC) and its blend with high-density polyethylene (PE) as a function of melt temperature and contact time. A comparison between the model predictions and experimental results was also performed for pure...
General possibilities of velocity sedimentation in the hydrodynamic study of macromolecules are discussed. It is shown that, using the mass-spectrometric effect of the ultracentrifuge together with the calculation of molecular weights by means of a recently introduced sedimentation parameter β s , allows complete analysis of all the macromolecular parameters of polymers by velocity sedimentation...
The non-isothermal crystallization behaviour of blends of poly(phenylene sulfide) (PPS) with the thermotropic liquid-crystalline copoly(ester amide) Vectra-B950 (VB) was studied by means of differential scanning calorimetry. The PPS crystallization temperature and the crystallization rate coefficient were found to increase markedly upon addition of 2-50% VB. It was shown that the Ozawa equation is...
The morphological structure of an extremely highly crystalline poly(ethylene terephthalate) (PET) which was obtained by very long term annealing after direct esterification was characterized by small angle and wide angle X-ray diffraction, infra-red spectroscopy, and density and fusion measurements. The specimen has a high melting point of 302.5°C, an observed density of 1.468 g cm -3 ...
When amorphous polymers of same type are brought into contact at temperatures above the glass transition, the interface gradually heals and junction boundaries eventually disappear. Here we used a steady-state fluorescence technique to examine the healing and interdiffusion of polymer molecules during annealing of latex film above the glass transition. The film was prepared from a mixture of naphthalene-...
The kinetics of polyelectrolyte hydrogel collapse in water solutions of CuSO 4 was studied. It was shown that the equilibrium degree of contraction essentially depends on the route by which the equilibrium is attained. The hydrogel kinetics of collapse in solutions of polyvalent metal salts is interpreted from the point of view of two different mechanisms of gel collapse. The transition...
The intrinsic viscosity, [η], and the Huggins constant, k , of a poly(acrylic acid) (PAA) sample have been measured at different degrees of neutralization, i, ranging from i=0.25 to i=1.00 and different ionic strengths,I , in the region 1.0 10 -4 M < I < 1.0 10 -1 M, using the isoionic dilution method in aqueous solutions. The results show that the variations...
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