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Polydimethylsiloxanes (PDMSs) with a narrow molecular weight distribution and fitted at one chain end with a hydrogenodimethylsilyl or a dimethylvinylsilyl function were prepared by the anionic ring-opening reaction of hexamethylcyclotrisiloxane in a 50 vol% benzene-tetrahydrofuran solution, followed by endcapping with chlorodimethylsilane or chlorodimethylvinylsilane. The experimental conditions...
Using dynamic (viscometry) and static (light scattering) measurements we study solutions of polystyrene and poly(methyl methacrylate) fractions ranging from extremely dilute solutions up to the critical concentration c * . When viscometry is used, a crossover phenomenon is observed, separating the dilute solutions into extremely dilute and dilute solutions. The critical concentration c ...
Ubbelohde viscosity measurements were performed on dilute solutions of perfluorosulfonated ionomers (PFSI) in various solvents exhibiting quite different dielectric constants. With aliphatic alcohols as solvents an increase of the reduced viscosity with dilution is evident. This effect is analogous to the so-called polyelectrolyte effect observed for highly charged ionic polymers in polar solvents...
Ultra-high-molecular-weight poly(ethylene terephthalate) (UHMW-PET) with an intrinsic viscosity exceeding 2 dl g -1 (M n 1.1 10 5 ) was obtained by swollen-state polymerization with hydrogenated terphenyl as the solvent. The rate of swollen-state polymerization was described well by Tomita's kinetics for a melt-phase polycondensation reaction. This suggested that there...
The relaxation behaviour of coextruded linear low-density polyethylene (LLDPE) films, prepared from copolymers of ethylene-1-octene, is reported. The spectra, expressed in terms of loss tan δ, present a γ relaxation of lower intensity than that exhibited for conventional low density polyethylene of the same crystallinity, followed, with increasing temperature, by a β relaxation process that appears...
Changes in the luminescence of poly(ethylene terephthalate) (PET) degraded in the absence and presence of oxygen at melt temperatures has been investigated. On oxidative degradation monomer fluorescence is reduced, with a concurrent increase in dimer fluorescence at long wavelengths. This is consistent with main chain breakdown and aggregation of the terephthalate fragments produced. Longer wavelength...
The fluoropolymer poly[2,3-bis(trifluoromethyl)norbornadiene] (poly(BTFMND)) has been synthesized via ring-opening metathesis polymerization, using initiators based on W, Mo or Ru compounds or via variations of the Schrock-type initiator Mo(CHR)(N-2,6-C 6 H 3 -i-Pr 2 )(OR ) 2 (R = CMe 3 , CMe 2 Ph; R = CMe 3 , CMe(CF 3 ) 2 ...
The viscoelastic properties of polypropylene fibres are investigated in a single-step stress relaxation test for small strains at temperatures between -50 and +30°C, thus well encompassing the glass transition temperature. For the analysis of the curves a formal two-component (TC) model is applied, which comprises an elastic and a viscoelastic component, the time-dependence of which is described...
A poly(ether imide) (Ultem), which is an amorphous engineering thermoplastic, was melt blended with two liquid crystalline polymers: one based on p-hydroxybenzoic acid and 2-hydroxy-6-naphthoic acid (Vectra A900) and the other based on phenylhydroquinone, ethylphenylhydroquinone and terephthalic acid (Granlar). The miscibility of these two blend systems was studied by means of differential scanning...
The chloromethylation of poly(methylsilane) is readily achieved using chloromethyl methyl ether in a tin(IV) chloride-catalysed reaction in chloroform solution at 0°C. A convenient, less hazardous reaction, in which chloromethyl methyl ether is prepared in situ, is also reported. The accompanying variations of the polymer molecular-weight parameters are recorded for chloromethylations extending...
Relaxation/transition behaviours for copolyesters made from poly(ethylene terephthalate) (PET) andp -acetoxybenzoic acid (POB) have been characterized by thermally stimulated current (TSC) measurement. The sequence distribution, in terms of the degree of blockiness, in dual chemidomains of POB/PET copolyester is simulated from a model developed by us to predict the probability between block sequence...
The critical concentration, c * , at which overlapping between macromolecular chains occurs, has been studied using dynamic (viscometry) and static (light scattering) methods. With the same polymer-solvent system this critical concentration has a higher value when viscometry is used, compared to the concentration obtained when using a light scattering technique. This difference is attributed...
For the purpose of developing an effective surface finish for copper, imidazole-silane copolymers were synthesized by radical copolymerization of 1-vinylimidazole and methacryl or styryl silane coupling agents. It was found that the reactivity of 1-vinylimidazole was very low as in the case of the copolymerization with styrene or other vinyl monomers. Monomer reactivity ratios obtained from Kelen-Tudus...
Drawn multifilament poly(ethylene terephthalate) yarn was heat-set isothermally at temperatures between 180 and 258°C in the slack and taut conditions. The apparent crystal widths of these samples in the undeformed state and when axially stretched by 5-40% were monitored by X-ray diffraction. Significant reduction of crystal width occurred in the [010] direction in samples heat-set at high temperatures...
A 13 C nuclear magnetic resonance study (with cross polarization and magic angle spinning) is presented of commercially available cellulose acetate and cellulose propionate as powder samples and also in different membranes. Some physical properties of the films are interpreted in the light of data obtained for the principal components of the shielding tensor of 13 C nuclei...
A model was developed for interdiffusion at interfaces of polymers with dissimilar physical properties. This model is based on the assumption that the monomeric friction coefficients of the two polymers are identical but a strong function of the matrix composition. The composition dependence of the monomeric friction coefficient was evaluated from the blend zero-shear viscosity using the reptation...
The intrinsic viscosity of poly(ethyl methacrylate) in isopropyl alcohol (propan-2-ol) around the theta (θ) temperature was measured using a capillary viscometer. Contraction and collapse were observed below the θ temperature. Because of experimental difficulties around the cloud point, mathematically curve-fitted experimental points were obtained instead of experimental data at lower temperatures...
The current demand for environmentally degradable composites has initiated the use of novel biodegradable copolyamides reinforced with E-glass fibres by using the hand lay-up technique. Differential thermal analysis, wide-angle X-ray diffraction patterns and density measurements were employed for the characterization of polymeric composites. The thermal properties of composites, namely T g ...
After synthesis, poly(seleno-p-arylene diamine)s were doped with chlorine. The polymers were studied before and after doping by X-ray photoelectron spectroscopy (X.p.s.), electron spin resonance (e.s.r.) and conductivity measurements. It is suggested that chain ends may be partly terminated by groups containing oxygen. After doping, there is charge transfer complex formation as shown by X.p.s. analysis...
The aqueous electrochemically initiated polymerization of pyrrole has been successfully performed on graphite fibres from a solution containing the monomer and toluene-4-sulfonic acid sodium salt. The effects of the initial monomer concentration, supporting electrolyte concentration and applied voltage on the rate of electropolymerization of pyrrole have been investigated in an attempt to ascertain...
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