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It is shown that loading ultra-high molecular weight polyethylene (UHMW-PE) fibres up to about 50% of their theoretical strength causes bond scission to occur as corroborated from the number of radicals monitored. In addition, a creep test on UHMW-PE fibres also showed an ongoing production of radicals in the polymer. Although precise quantification of the radical concentration is difficult, a first...
In this communication we try to provide a straightforward but critical discussion on the meaning of the degree of crystallinity defined by the enthalpy of melting. We show that the widely used crystallinity obtained by Δh f h 0f can be called the equivalent weight crystallinity , signifying the amount of perfect crystals that can be melted by the measured enthalpy of melting...
A rheo-optical study has been developed to examine the nature of the structural changes, other than the well known chain orientation, that can appear during uniaxial drawing of polyethylene samples. Stretching was performed at room temperature in samples of melt-crystallized high- and low-density polyethylene. Raman spectra were simultaneously collected along with stress and strain data in order...
In numerous applications of gels, one sometimes needs to control the gelation process. Here we focus our investigations on a particular means to attain this aim for the scleroglucan-zirconium system. For this purpose some oxyacids have been added to the system. Since the oxyacids involved are known to form complexes of various stability with zirconium, the whole gelation system follows from competition...
The effect of hydrostatic pressures up to 500 MPa on the position of the 1616 cm -1 Raman line of amorphous, randomly oriented poly(ethylene terephthalate) has been studied. The shift varies linearly with pressure, with a sensitivity of 5.6±0.3cm -1 GPa -1 . This value is in excellent agreement with the value of 6.4 ± 1.4 cm -1 GPa -1...
The miscibility and phase behaviour of the ternary blend consisting of poly(ε-caprolactone) (PCL), poly(styrene-co-acrylonitrile) with 15 wt% acrylonitrile (SAN15) and poly(styrene-co-maleic anhydride) with 14 wt% maleic anhydride (SMA14) have been investigated by means of visual observations, light transmission measurements, differential scanning calorimetry (d.s.c.) and dynamic mechanical thermal...
The purpose of this brief communication is to demonstrate how near-infra-red (n.i.r.) spectroscopy can be used to characterize molecular orientation in stretched polymers. Combined with the polarization modulation technique, n.i.r. provides a useful way of measuring small anisotropy with high precision in thick polymer films.
The unseeded semicontinuous emulsion copolymerization of methyl methacrylate and n-butyl acrylate using mixed surfactant systems (anionic SLS (sodium lauryl sulfate) and non-ionic Brij35) in a wide range of concentrations and at different SLS/Brij35 ratios (1, 1, 1,1 , 0) was studied. Two different kinetic behaviours led to reactor starved conditions with single anionic or with mixed surfactant...
Free radical polymerization of glyceryl methacrylate (GMA) has been conducted (i) in bulk, (ii) in moderately concentrated aqueous solution and (iii) in dilute aqeous solution. For (i) and (ii) the resultant poly(glyceryl methacrylate) (PGMA) was either insoluble or only swelled in a wide range of common solvents, whereas for (iii) solubility occurred in three polar liquids of which only one (2-methoxyethanol)...
The important results from the substantial body of experimental data on the formation of poly(1,4-phenylene sulfide) by polymerization of copper(i) 4-bromobenzenethiolate (CBT) have been documented. Single-electron transfer (SET) mechanisms are proposed that are capable of explaining all the experimental observations in a self-consistent manner. An S RN 1-type mechanism is thought to...
The effect of the amount of crystallinity on fracture and yielding of polyethylenes as a function of temperature is reviewed. In particular, the effect of fracture toughness, K c , at low temperatures is investigated. Generally, K c increased linearly as density decreased. However, it was found that very low-density polyethylene shows a significant decrease in K c from this...
A study of the effects of some chlorinated organic solvents on the physical and spectral properties of poly(ether ether ketone) (PEEK) has been carried out. Infra-red and Raman spectroscopy, as well as mass diffusion studies, were used to examine the consequences of exposing PEEK to carbon tetrachloride, methylene chloride, chloroform and tetrachloroethane. Certain solvents were found to cause swelling...
Unsaturated polyesters and dicarboxy diesters from maleic anhydride and various diols were investigated by means of 1 H and 13 C nuclear magnetic resonance spectroscopy. The carbons of diol units were found to be sensitive to maleate/fumarate transformation, enabling the process to be followed in detail. The cis-trans isomerism of dicarboxy diesters was described and related...
Solvent uptake in thin, amorphous samples of poly(ether ether ketone), poly(ether imide) and a 50 blend has been measured as a function of temperature. Diffusion coefficients, percentage weight increase and apparent activation energies have been calculated. The 50 blend shows anomalous diffusion behaviour which may be attributed to specific interactions between the homopolymers and density changes...
The morphology of injection moulded samples of polyamide-polybutadiene blends (85.15) with an average particle size of 0.3 μm was studied. The samples were fractured in a notched tensile test at crosshead speeds of 10 -4 and 1 m s -1 and the structure of the deformation zone was studied using various techniques: polarized light microscopy, scanning electron microscopy, transmission...
The effect of high energy radiation on halogenated butyl rubbers was studied using electron spin resonance and nuclear magnetic resonance spectroscopies and gas chromatography. During high energy irradiation, most of the radicals were found to be generated on the halogenated isoprene units. A higher radiation yield for scission was observed in chlorinated butyl rubber than in brominated butyl rubber...
Permeability measurements were performed on several polymeric films used for packaging applications. The results were analysed in terms of the ratio of the permeabilities between two gases. Moreover, recent experimental results and data reported in the literature have been compared with a simple relationship reported by van Krevelen for predicting the transport properties of high molecular weight...
Cross-polarization/magic angle spinning (CP/MAS) 13 C nuclear magnetic resonance (n.m.r.) spectra of several random ethylene (E)/vinyl alcohol (VOH) copolymers, including both homopolymers, have been obtained. Contributions to these spectra arising from the crystalline and non-crystalline regions of these materials have been isolated and from these spectra the average concentrations of...
The mechanisms of tri-dimensional polyesterifications in bulk at 180°C of ternary mixtures of o-phthalic anhydride (P) + azelaic acid (Z) + trimethylolpropane (T), as well as the distributions of acid branches on the potential crosslinking T units, have been studied by liquid 13 C n.m.r. before (sol) and after (gel) gelation. The critical time for gelation is found to decrease when Z...
An investigation into the mechanism of formation of poly(1,4-phenylene sulfide) (PPS) by solution polymerization of copper (i) 4-bromobenzenethiolate (CBT) at 200°C in quinoline under nitrogen at atmospheric pressure is reported. The polymerization has been monitored as a function of reaction time by electron spin resonance (e.s.r.) spectroscopy and by evaluating the yield and molar mass of the PPS...
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