1999 рік

Linear relationships of variations of crystalline c-parameters of orthorhombic, triclinic and monoclinic n-alkane structures as a function of n, the carbon atom number, are established by linear least square fitting the data taken from the literature and compared with the relationships previously determined. In particular, the results correspond well with the predictions of Nyburg and Potworowski for Pbcm orthorhombic structures: they allow the precise determination of the mean carbon–carbon distance projected onto the chain axis that is equal to 1.2724 Å and the gap value of 3.1476 Å between the end-methyl-group carbon atom planes of the two consecutive molecule layers.

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A new class of N-halamine polymers has been synthesized. These polymers can be emulsified in water to produce coatings which, once chlorinated, act as contact disinfectants. The surfaces inactivate bacterial organisms efficiently, requiring relatively brief contact times of several minutes. The latexes can be formed by copolymerization of a N-halamine precursor monomer with other monomers in water with the aid of a surfactant, or by chemically grafting the N-halamine precursor monomer onto an emulsified polymer backbone, followed by chlorination.

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In Part 1 of this series (Polymer 1999;40:3685), the concept for the preparation of expandable polystyrene (PS) applying water as a blowing agent was presented. In order to achieve this goal, water was emulsified by means of a commercially available surfactant (sodium bis(2-ethylhexyl)sulfosuccinate) in a prepolymerised styrene/PS mixture. This mixture was subsequently suspended in water and polymerisation was continued to complete conversion. This procedure resulted in spherical PS beads containing tiny water droplets which were capable of expanding the material upon heating above its glass transition temperature. In certain cases (especially at high surfactant concentrations), miscibility problems between the surfactant and the PS matrix caused unstable systems during polymerisation. For this reason, a new technique was developed to synthesise in-situ amphiphilic copolymers with good miscibility in the PS matrix. This novel route to incorporate very finely dispersed water into polystyrene is described in this paper. This procedure also has potential for the preparation of amphiphilic species with other applications, e.g. as detergents, dispersants, in the enhanced oil recovery, etc., since a very simple radical copolymerisation is applied, whereas the syntheses of most surfactants require a relatively complicated reaction sequence.

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Melt blends of poly(phenylene oxide)(PPO) with glass fiber reinforced syndiotactic polystyrene(GFRsPS) were prepared using a single screw extruder. DSC and dynamic mechanical measurements indicate that the PPO/GFRsPS blends are miscible in amorphous state as shown by the existence of a single Tg whose values are blend composition-dependent. From the mechanical test results, it is shown that the tensile and flexural modulus increase, but the tensile and flexural strength do not improve as the GFRsPS content increases. An increase in the melt flow index (MFI) as GFRsPS contents increase implies that the processing problem of neat PPO is improved.

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The laser Raman and the Fourier transform infra-red (FTi.r.) microspectroscopic analyses were conducted to monitor the interfacial degradation process in a model composite of an aramid fibre (Kevlar 49) and unsaturated polyester (UP) exposed to water at 30 and 90°C. For micro-laser Raman spectroscopy, a single long fibre was embedded in the UP resin being subjected to static tension. Removing the applied tension after curing the film specimen introduced the residual tensile stress into the fibre. The progress of degradation by water in a region of interface was monitored by measuring the peak shift of the Raman spectrum varying proportionally to the stress generated in the fibre. The micro-FTi.r. measurements were done to examine the quantity and the state of absorbed water in the UP resin very near the interface. The thin film specimen, in which the long fibre was not subjected to pre-tension during the cure, was analysed under transmission mode. The residual tensile stress in the fibre was monotonously decreased in hot water at 90°C, and completely released for about 150 h, although the stress reduction for early period of 24 h was mainly caused by the relaxation of elastic modulus of the UP matrix. In water at 30°C, on the contrary, the residual stress remained the initial value for a long time above 1000 h. The micro-FTi.r. analyses revealed that at an early stage the isolated water is mainly observed, and then larger amount of clustered water is absorbed with increasing soaking time, particularly at 90°C. At present, however, it is not clear which type of water more strongly participates in the interfacial degradation.

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In Part 1 (Polymer 1999;40:3685) of this series, the concept for the preparation of expandable polystyrene (PS) applying water as a blowing agent was presented. This paper focuses on the expansion characteristics of water expandable polystyrene (WEPS) beads. The influence of temperature, amount of blowing agent, molar mass of the PS matrix and slight crosslinking of the matrix were investigated in view of the expansion performance in hot air. A maximum volume expansion by a factor of 25 was achieved for WEPS in hot air (135°C) as the heating medium.

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The influence of vinylidenefluoride (three different compositions, viz. 0, 0.5 and 3.0%) on the free volume of the polymer poly(chlorotrifluoroethylene) has been investigated using the Positron Annihilation Lifetime technique. The lifetime results indicate that, with the increase in the composition of vinylidenefluoride, the average free volume size of the polymer decreases whereas their number density increases. Further, it has been observed that the glass transition temperature (Tg) of this polymer decreases with the increase in vinylidenefluoride content. The present results complement the literature report that vinylidenefluoride influences mainly the amorphous regions of poly (chlorotrifluoroethylene).

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Blends of poly(methyl-n-propylsilane) (PMPrS) and poly(di-n-hexylsilane) (PDHS) were prepared in various compositions by solution mixing method. The blends were studied using differential scanning calorimetry, optical microscopy, fluorescence and UV spectroscopy. The blend samples were isothermally crystallized at temperatures in which only the PMPrS crystallized. The equilibrium melting point of PMPrS was estimated from the Hoffman–Weeks plots. Depression of equilibrium melting point of PMPrS with increasing PDHS content indicated some degree of miscibility. Fluorescence spectroscopic studies indicated that energy transfer occurs form PMPrS to PDHS. Comparison with an immiscible blend showed that energy transfer occurs only in miscible blends. Optical microscopy studies using crossed polarizers showed liquid crystalline mesophase in all the blends with PMPrS/PDHS ¼ 90/10–0/100.

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Blends of poly(caprolactone)–poly(ethylene glycol) block copolymer (PCE) with polypropylene (PP) were extruded followed by compression moulding. The compatibility and degradation behaviour of the blends were investigated. The results showed that the PCE phase tended to disperse as discrete particles in the PP matrix of the PP/PCE 75/25 blend. This discrete PCE phase was incompatible with the PP matrix. Maleic anhydride (MA) grafted PP was found to improve the compatibility between the PCE and PP phases effectively. Consequently, the MA-compatibilized PP/PCE 75/25 blend experienced significant losses in weight and tensile strength, compared with uncompatibilized PP/PCE 75/25 blend, after immersion in a buffer solution (pH ˆ 6.0) at 45°C for extended periods of time. Water sorption and contact angle measurements also revealed that MA-compatibilized PP/PCE 75/25 blend is more hydrophilic than the uncompatibilized counterpart. The effect of the compatibilizing agent on the morphology and degradation behaviour of PP/PCE blends is discussed.

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To avoid electrostatic charging of an insulating matrix an electrical conductivity above s ˆ 10 26 Sm 21 is needed. At present, the most common practice to achieve this conductivity is to use a conductive filler such as carbon black. In this work, untreated catalytically-grown carbon nanotubes were dispersed in an epoxy matrix. After curing the epoxy, the electrical properties of the composite were measured in order to relate the filler volume fraction to the electrical conductivity. The intense stirring process used to disperse the carbon nanotubes has made it possible to achieve a matrix conductivity around s ˆ 10 22 Sm 21 with filler volume fractions as low as 0.1 vol.%. These figures represent an advance on best conductivity values previously obtained with carbon black in the same epoxy matrix. These low filler fractions ensure that the mechanical properties of the matrix are not compromised.

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