Multi-wall carbon nanotubes (MWNT) were used as reinforcement for melamine-formaldehyde (MF). They were oxidised in HNO3/H2SO4 mixture and analyzed by means of X-ray Photoelectron Spectroscopy (XPS). Two anionic surfactants: sodium dodecyl sulphate (SDS) and sodium dodecylbenzenesulfonate (NaDDBS) were used to assist the dispersion of nanotubes. The MWNT content was varied from 0 to 1.0 wt%, and the influence of nanotubes on viscosity (flow curves) was measured. The viscosity of SDS-assisted aqueous solution of MF containing a small amount (0.1 wt%) of MWNT is low, and thus promising towards manufacturing processes. A film stacking-like manufacturing route was adapted to prepare ternary MWNT/cellulose/MF thin composite layers. Transmission electron microscopy (TEM) and Light microscopy (LM) were used to observe dispersion. The addition of 0.1 wt% MWNT assisted with SDS increased the storage modulus and tensile strength by 50%. Conventional calculations of the Young’s modulus were made. Values underestimating the modulus were found. The observed discrepancy was attributed to polymer chain immobilisation as a result of crosslinking.

The aim of this investigation was to evaluate the possibility of mechanically recycling blends of ABS with minor amounts of semicrystalline engineering plastics, such as polyamide, poly(ethylene terephthalate), and poly(butylene terephthalate). Compatibilizers and a core-shell impact modifier were incorporated into the blends in order to improve the mechanical properties. The toughness values, measured by the J-integral method, and the Charpy impact strength did not always exhibit consistent results, due to the significant difference in deformation rate and in fracture mechanism. The formation of co-continuous structures in the blends were noted and discussed. The fibrillation in the fracture surface contributed to the toughness as measured by the J-integral method. (C) 2002 Wiley Periodicals, Inc.

The aim of this work is to evaluate routes to upgrade recycled engineering plastics, especially mixed plastics with acrylonitrile-butadiene-styrene copolymers (ABS) as the major component. A core-shell impact modifier was successfully used to improve the impact strength of blends of ABS and ABS/polycarbonate (PC) blends recycled from the automotive industry. However, the presence of other immiscible components like polyamide (PA), even in small amounts, can lead to a deterioration in the overall properties of the blends. A styrene-maleic anhydride (SMA) copolymer and other commercial polymer blends were used to promote the compatibilization of ABS and PA. The core-hell impact modifier was again found to be an efficient additive with regard to the impact strength of the compatibilized ABS/PA blends. The results obtained with fresh material blends were quite promising. However, in blends of recycled ABS and glass-fiber-reinforced PA, the impact strength did not exhibit the desired behavior. The presence of poorly bonded glass fibers in the blend matrix was the probable reason for the poor impact strength compared with that of a blend of recycled ABS and mineral-filled PA. Although functionalized triblock rubbers (SEBS-MA) can substantially enhance the impact strength of PA, they did not improve the impact strength of ABS/PA blends because the miscibility with ABS is poor. The possibilities of using commercial polymer blends to compatibilize otherwise incompatible polymer mixtures were also explored giving promising results. (C) 2002 Wiley Periodicals, Inc.

The influence on the adhesion to some metal surfaces and the damping properties of various modified styrene-ethylene/butylene-styrene (SEBS) materials was evaluated. Modification of the different phases of the SEBS with resins was shown to have a large effect on the damping properties of the polymers, which were evaluated by dynamic mechanical analysis (DMA). A small amount of maleic anhydride grafted onto the EB block was found to lead to a significant improvement in the adhesion of the polymer to some metal surfaces without affecting the damping properties of the polymers. The results of the DMA tests on the polymers were used to calculate the composite loss factor (CLF) for a steel laminate, which consisted of two steel plates with a polymeric layer in between, according to the theory proposed by Ross, Ungar, and Kerwin. The calculated results were compared with the measured CLFs determined in vibrating beam tests (VBTs). The agreement between the calculated and measured values was quite fair, provided that the DMA values used for the calculations were recalculated to the actual higher frequencies used in the VBTs, using the time-temperature superposition principle. (C) 2001 John Wiley & Sons, Inc.

The influence of platelet mica fillers on the damping properties of a polymer specimen produced from a core-shell latex based on styrene, methyl methacrylate and ethylhexylacrylate was evaluated. This polymer is expected to exhibit an interpenetrating network (IPN) structure, and in the unfilled state it exhibits a rather broad glass transition (T-g) region. The damping peak (tan delta), evaluated by dynamic mechanical analysis (DMA), became somewhat higher when mica filler was added to the polymer but the T-g-region became somewhat narrower. The filler particle size had no appreciable influence on the damping properties of the filled polymer. Silane treatment of the mica resulted in a slight broadening of the glass transition (lower temperature side of the peak) and a decrease in the magnitude of the damping peak compared to the result obtained with untreated mica of the same particle size. The results of the DMA measurements on the polymer samples were used to calculate the composite loss factor (CLF) for a steel laminate consisting of two steel plates with a thin intermediate polymeric layer, using the theory proposed by Ross, Ungar and Kerwin (RUK). The calculated results were compared with the measured composite loss factors at higher frequencies (200 Hz or more) determined in vibrating beam tests (VBT). The agreement between the calculated and measured values with regard to the temperature location of the damping peak was reasonably good for the unfilled material, provided that the DMA values used for the calculations were recalculated using the time-temperature superposition principle to the actual higher frequencies used in the VET. For the filled systems, the RUK theory predicted the location of the CLF-damping peak to be ca. 5 degrees C higher than was observed experimentally. Possible reasons for this are discussed. Addition of the mica to the polymer affected the experimentally determined CLF values somewhat, but the changes were not very dramatic.

The aim of this work within the framework of mechanical recycling of polymers is upgrading recycled engineering plastics by means of a blending technique. Four different plastics from dismantled Volvo cars have been investigated. They are poly(acrylonitrile-butadiene-styrene) (ABS) and ABS-polycarbonate (ABS/PC) as major components and poly(methyl methacrylate) (PMMA) and polyamide (PA) as minor components. Blending recycled ABS and PC/ABS (70/30) with a small amount of methyl methacrylate-butadiene-styrene core-shell impact modifiers gives the mixture better impact properties than any of its individual components. Some 10% of PMMA from tail light housings can follow the PC/ABS blends made. The property profile will rather be improved. However, PA is an incompatible component that should be sorted out from the mixture. Antioxidants and metal deactivators do not help the recyclates show better mechanical properties. Two toughness measurements, Charpy impact strength and J-integral method, show complimentary results for such blends. (C) 1999 John Wiley & Sons, Inc.

The small particle size of ceramic and hardmetal powders significantly increases the risk of particle agglomeration with an associated increase in viscosity of plastisols used in powder injection moulding. The agglomeration is counteracted by adding surface active compounds to the powder containing plastisol. A model is presented for the functioning of such additives in injection moulding or fine (ceramic, hardmetal) powder. The idea is to create a thin, dense adsorbed layer which reduces the attractive van der Waals forces without adding considerably to particle size, thus decreasing viscosity without creating perfect stability. In this manner, the pseudoplasticity necessary for the injection moulding is retained. The approach outlined shows that the adsorbates working as dispersants should be short molecules such as stearic acid, stearyl alcohol, and octadecyl silanes, all built around a C18 chain. (C) 1997 EPMA.

The automotive, electrical and electronic sectors account for over 12 % of all plastics consumed. A large fraction of these polymers are engineering plastics representing a value considerably higher than that of commodity thermoplastics; hence, mechanical recycling including upgrading efforts appears economically attractive. This paper shows some methods of upgrading the property profile of ABS from dismantled automobiles using polymer blend technology. The results for blends of ABS with PC or PA are reported. The aim of blending of the waste materials is twofold: to reduce the number of plastic materials to be recycled in car dismantling plants, and to improve properties of the ABS scrap, which is the main engineering plastic in the waste stream from automobiles.

The distribution of aluminium borate whiskers in blends of polyethylene/polyisobutylene (PE/PIB) was studied with respect to viscosities of the components. Both polymers are non-polar with slightly higher surface energy for the PE, i.e. weak filler–polymer interactions of about equal strength. The significance of the polymers' viscosity disparity can thus be studied in isolation. Two PEs and two PIBs with clearly separated flow curves (ηPE1>ηPIB1≫ηPE2>ηPIB2) were used. The whiskers were found in the high viscosity phase except when they promoted coherency of the low viscosity minority phase. However, the PE's slightly higher surface energy ruled the absorption although PIB was slightly more viscous showing the relative weakness of this rheological phenomenon. Furthermore, the viscosity distributing factor was found to be less important than polar interactions. A rheological explanation is presented that supports the observed selective absorption.

The rheological time dependencies of both whisker-filled (composites) and unfilled PE/PIB and SAN/PA6 blends were studied as functions of composition and shear history. A three-step experiment of steady dynamic—steady shear was designed. Rupture and formation of the morphology in batch-compounded blends/composites was conveniently and accurately studied in the first steady shear. The second step emphasises morphological sensitivity in blends close to phase inversion. During the oscillation phase metamorphosis and whisker transport were noticed. The third step together with microscopy studies confirmed these observations.

The influence of a filler on melt-mixed conducting polymer blends of poly(3-octylthiophene) (POT) has been examined with respect to their morphology, rheology, conductivity and acid-base properties. The matrix polymers used were low density polyethylene (LDPE), poly(vinyl chloride) (PVC) and poly(methyl methacrylate) (PMMA) and the filler was non-conducting aluminum borate whiskers. These blends show two-phase behavior when examined by scanning electron microscopy. It was found that the adhesion at the polymer-filler interface in combination with the viscosity ratios between the polymers exerts a considerable influence on the morphology and hence on the conductivity. For the PE/POT blends, addition of whiskers changed the morphology and increased the conductivity by several orders of magnitude. The conductivity of blends with PVC was almost unchanged while the conductivity of PMMA blends slightly decreased upon addition of whiskers. The interactions between whiskers and the polymers used decreased in the order: PMMA > POT > PVC > PE. This is in accordance with the Lewis acid-base properties determined by inverse gas chromatography.

Gas- and water-atomized stainless steel powders of small particle diameter were injection molded with a binder consisting of polyolefins and low melting waxes. The critical powder loadings for injection molding were 65 and 56v/o for the gas- and water-atomized powders, respectively. The binder removal rate was established by measuring the weight decrease during heating of the components. Binder removal was performed in nitrogen gas at either 400 degrees C or 500 degrees C for times varying from 4h to 23h. After debinding the specimens were vacuum sintered at 1200 degrees C or 1250 degrees C for times ranging from 4h to 8h. Maximum tensile strength was obtained for the gas-atomized powder sintered at 1250 degrees C. The tensile strength of the water-atomized powder sintered at the same temperature was lower due to higher porosity Gas-atomized powder sintered to the same high porosity level as the water-atomized showed the same tensile strength values as the latter If was also shown that binder removal at the lower temperature (400 degrees C), resulted in higher strength, due probably to a more effective reduction of the oxide by binder residuals during sintering.

Instrumentation for time-dependent stress dilatometry of polymers was constructed. Volumetric measurements in creep for polycarbonate and in stress relaxation for polyethylene were carried out. The advantage of the transverse and axial strain rate ratio for volumetric analysis, in creep, is emphasized. An experimental finding of volume-stress linearity in stress relaxation measurements is presented and discussed.

Theoretical calculations of the volume strain behavior of the standard linear solid model and the generalized model of Voigt-Kelvin type were in agreement with the experimental data, predicting an increase or decrease in ɛν with time for μ < 0.5 and μ > 0.5, respectively.

This paper is concerned with the creep behavior of short fiber-reinforced thermoplastics, especially with regard to the role of fiber orientation. Rectangular samples of low density polyethylene (LDPE) and polycarbonate (PC) containing varying amounts of carbon fibers were prepared by compression and injection molding. The materials were compounded using a technique producing a concentration independent fiber length distribution. The orientation distribution, on the other hand, was found to be strongly influenced by fiber concentration. The creep parameters were measured for both LDPE and PC. The contraction ratio was determined for the PC samples. In the case of LDPE reliable data could not be obtained due to the low modulus of the matrix. The creep properties of the PC and LDPE samples varied significantly with the orientation of the fibers. The creep strain was measured as a function of time for both polymers for different fiber concentrations and orientations. The predictions of the Halpin-Tsai equation underestimated the experimental strain figures somewhat when the stress direction coincided with that of the fiber orientation. When the stress acted across the fibers the theoretical and experimental results showed satisfactory agreement. A plausible explanation is that incorporation of carbon fibers changes the morphology of the matrix material. We conclude that the contraction ratio is an important measure of the volume and its changes during deformation, especially with regard to its relation to the free volume and similar quantities. We have shown that the necessary data can be obtained, in spite of experimental difficulties even for anisotropic samples.

This paper describes the properties of a kinetic formula derived from a differential equation based on a time-domain induction mechanism reminiscent of that encountered in Bose-Einstein statistics, d(n/n)/dt = -an/n + beta(n/n)2, with n denoting the relaxing quantity and n its time derivative. While, as shown earlier, the corresponding equation without the normalization of n with regard to n produced an exponential relation between n and n, a generalized power law is obtained in the present case. As in the former case the distribution of relaxation times is discrete, the spectral lines being integer-valued fractions of a fundamental time constant.

This paper explores the properties of a relaxation function derived from a differential equation mimicking the distribution mechanism of Bose-Einstein statistics in the time domain. Within a significant portion of the process, the relaxation quantity n decreases linearly with log time. The relation between dn/dt and n is an exponential one. In this respect, the present approach produces results largely equivalent to those obtained using the hypothesis of stress-dependent thermal activation or a box-like spectrum of relaxation times, τ. The τ spectrum of the model proposed here is discrete, with integer valued fractions of a characteristic -centering the equations.