The Infona portal uses cookies, i.e. strings of text saved by a browser on the user's device. The portal can access those files and use them to remember the user's data, such as their chosen settings (screen view, interface language, etc.), or their login data. By using the Infona portal the user accepts automatic saving and using this information for portal operation purposes. More information on the subject can be found in the Privacy Policy and Terms of Service. By closing this window the user confirms that they have read the information on cookie usage, and they accept the privacy policy and the way cookies are used by the portal. You can change the cookie settings in your browser.
Four different grades of polyethylene have been annealed under high pressures, to transform the morphology, and then oriented by hydrostatic extrusion. The pre-extrusion morphology is shown to have a significant influence on the mechanical properties of the extrudates. At high crystallinities the mechanical behaviour of the extrudates can be interpreted using a simple aggregate model. This model...
The sedimentation velocity of hydroxypropyl cellulose acetate and cyanoethylhydroxypropyl cellulose molecules has been investigated in dilute solution in organic solvents. For these polymers, a linear dependence of the standard deviation of the displacement spectrum of macromolecules in an ultracentrifuge field on the sedimentation boundary shift was observed. The method of moments with linear approximations...
This communication reports the synthetic steps and characterization required to make pure poly(glycidyl nitrate), also known as polyGLYN or POWA3, from cheap commercially available starting materials using dinitrogen pentoxide (N 2 O 5 ) technology. Conditions are given whereby a range of well defined and characterized polyGLYN samples may be safely and reproducibly prepared by the...
Polycarbonate (PC) can be easily crystallized by injecting a very dilute benzene solution of PC directly into liquid nitrogen, and then freeze-drying to remove the solvent. The crystallinities of these prepared samples were characterized by wide-angle X-ray diffraction (WAXD). The results of WAXD studies showed that there is a concentration boundary in very dilute solution for crystallizability...
The miscibility of blends of nylon 6 with poly(maleic anhydride-co-vinyl acetate) (poly(MAH-co-VAc)), or hydroxylated poly(maleic anhydride-co-vinyl acetate) (poly(MAH-co-VAc)H) was investigated by means of Fourier transform infra-red (FTi.r.) spectroscopy, differential scanning calorimetry (d.s.c.), and X-ray diffraction. Poly(MAH-co-VAc) was prepared by radical copolymerization and the copolymers...
The proton nuclear magnetic resonance (n.m.r.) relaxation times of poly(ethylene oxide) grafted on silica were determined at 300 MHz. The dependence of the temperature and grafting ratio on the relaxation times is discussed qualitatively from a phenomenological point of view. Two models are proposed for the surface layer for the two extreme grafting ratio levels. At a low grafting ratio the chains...
The peroxide crosslinking of plasticized poly(vinyl chloride), PVC, blended with trimethylolpropane trimethacrylate, TMPTMA, has been studied by following gel formation and changes in mechanical properties. By applying the right preparation conditions and peroxide type, it was possible to avoid crosslinking while dry-blending the materials. During compression moulding, gel yield was found to increase...
We report the epitaxial polymerization and characterization of poly(p-oxybenzoate) (POBA) on various crystalline substrates. Acetoxybenzoic acid was polymerized onto solid crystalline substrates immersed in the paraffin solution. The resulting POBA films were characterized by polarized Fourier transform infra-red spectroscopy, transmission electron microscopy, scanning electron microscopy, wide-angle...
Polymer composites based on an epoxy resin oligomer, an amine terminated oligomer or maleic anhydride, and one or several monomers among styrene, methyl methacrylate, butyl methacrylate, glycidyl methacrylate, and acrylonitrile have been prepared using the concentrated emulsion pathway. Each of the components of the composite was first transformed in a concentrated emulsion in which water with a low...
Poly(N-vinylimidazole) was synthesized by free radical polymerization. It was quaternized with methyl iodide. The samples were doped with iodine and borontrifluoride. Products were characterized by elemental analysis, Fourier transform infra-red spectroscopy and differential scanning calorimetry techniques. The maximum electrical conductivities achieved were 10 -4 S cm -1...
A recently disclosed development 1-3 comprising a composite of flame retardant cellulose fibres and an intumescent has shown unusually high flame and heat resistance with a char structure that can withstand air exposure temperatures up to 1200°C. Char structures of selected flame retardant cellulose fibres when alone and blended with inert E-glass and aromatic char-forming novoloid...
Poly(hydroxybutyrate) (PHB) is a biodegradable thermoplastic. Melt-cast PHB sheets normally become brittle on storage. The embrittlement has been associated with cracks formed during cooling due to differences in radial and circumferential thermal expansion coefficients. We show that the cracks are in fact due to differences in thermal expansion between the PHB film and the constraining glass slides...
The complexation behaviour between poly(hydroxyether of bisphenol-A) (phenoxy) and three isomeric tertiary amide polymers, namely poly(N-methyl-N-vinylacetamide) (PMVAc), poly(N,N-dimethylacrylamide) (PDMA) and poly(2-ethyl-2-oxazoline) (PEOx), has been studied. Phenoxy forms interpolymer complexes with PMVAc and PDMA from tetrahydrofuran solutions over the entire feed composition range. However,...
The gas permeability and permselectivity properties were investigated of polyimides, prepared from 3,3 ,4,4 - and 2,2 ,3,3 -thiaphthalic dianhydride (p-TDPA and m-TDPA, respectively), or 1,4-bis(3,4-dicarboxyphenoxy)- and 1,4-bis(2,3-dicarboxyphenoxy) benzene dianhydride (p-HQDPA and m-HQDPA, respectively), and 4,4-oxydianiline. The polyimides prepared from meta-dianhydrides, which have lower...
A method is presented to evaluate the Koningsveld g-functions for quasi-ternary polymer solutions and blends, involving binary and ternary interactions. A robust set of 12 equations derived from the Flory-Huggins lattice theory, dealing with liquid-liquid phase separation conditions, have been solved using as input data the experimental volume fractions of each component in each coexisting phase...
Incorporation of up to 30 phr of high abrasion furnace (HAF) carbon black into a thermoplastic elastomer of composition 100 phr maleated EPDM rubber, 10 phr ZnO, 1 phr stearic acid and 30 phr zinc stearate, improves its physical properties like modulus and tear resistance. While the glass-rubber transition temperature (T g ) of the thermoplastic elastomer occurring around -37°C remains unaltered...
A synthetic methodology is reported for the preparation of spin-labelled side-chain liquid crystal polymers in which the label is covalently attached to the polymer backbone. Thus, a mesogenic methacrylate, 6-(4-methoxy-4 -oxy-azobenzene) hexyl methacrylate, was copolymerized with methacryloyl chloride and the resulting copolymer esterified using 4-hydroxy-2,2,6,6-tetramethylpiperidinyloxy (4-hydroxy...
The annihilation of positrons in amorphous tetramethylpolycarbonate (TMPC) has been investigated in the temperature range from 30 to 300 K. The dependences of the mean lifetime of the ortho-positronium τ 3 and its relative intensity I 3 on temperature can be described by the empirical relations: τ 3 = 2.08(1 + 4.8 10 -4 T) (ns) and I 3 = 20.2(1 + 7...
The changes in the molecular network of several grades of polyethylene subjected to high pressure annealing are followed using a simple model which combines thermal expansion and mechanical measurements. It is found that annealing reduces the degree of molecular entanglement, particularly when performed well within the intermediate hexagonal phase. It is shown that this process can be used to improve...
We have studied the applicability of Fourier transform (FT)-Raman spectroscopy to the determination of isotacticity in polypropylene. We have compared FT-Raman and Fourier transform infra-red (FTi.r.) spectroscopy as isotacticity determination methods and used 13 C nuclear magnetic resonance (n.m.r.) spectroscopy as a reference method. Calibration curves relating Raman scattering and...
Set the date range to filter the displayed results. You can set a starting date, ending date or both. You can enter the dates manually or choose them from the calendar.