1999 рік

3,3''-Di(4-aminophenyl)-5,5''-di(4-biphenylyl)-p-terphenyl and 3,3''-di(4-aminophenyl)-5,5'',6,6''-tetraphenyl-p-terphenyl as well as the corresponding acid chlorides were synthesized through pyrylium salts. The polyamides and polyimides prepared from them were characterized by inherent viscosity, elemental analyses, FTIR, UV–vis, 1H-NMR, 13C-NMR, X-ray diffraction, DSC, TMA, TGA, isothermal gravimetric analysis and moisture absorption. The polymers were amorphous and dissolved in polar aprotic solvents and CCl 3COOH. They did not show melting and their I g values ranged from 212 to 305°C. No weight loss was observed up to 357–386°C in air and the anaerobic char yields were 61–75% at 800°C.

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A mathematical model was developed to predict the isothermal drying kinetics of semicrystalline polymer films. The model considers the mechanism of semicrystalline polymer drying that was proposed by us based on experimental studies. Experimental studies have indicated an increase in the degree of crystallinity of semicrystalline poly(vinyl alcohol) (PVA) during drying, which slows down the rate of diffusion of the solvent remaining in the polymer film. The model considers the crystallization kinetics and the changes in the polymer degree of crystallinity produced in semicrystalline polymers during solvent removal. The model also takes into account rubbery–glassy transition and skin formation during solvent removal and its effect on the drying kinetics. Model predictions include polymer film thickness, skin thickness, rate of solvent removal and degree of crystallinity of the polymer as functions of time. These predictions were compared with experimental results for drying of PVA films and good agreement was observed between the model predictions and the experimental data.

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Synthetic methods leading to novel polysiloxanes and polystyrene copolymers are described. Both types of polymer could be modified by incorporation of the highly sterically demanding tris(trimethylsilyl)methyl substituent (Me$i)&. The modification increases the rigidity of polymers as shown by d.s.c. analyses. The effect is especially dramatic in the case of silyl substituted polysiloxane copolymer. In that case the steric bulk of the tris(trimethylsilyl)methyl group renders 8% of Si-H bonds in poly(methylhydrosiloxane) (PMHS) unreactive towards the hydrosilylation process. The Si-H bonds of the resultant copolymer can be utilised in crosslinking of the linear polysiloxane.

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In this paper, the structural gradients developed in co-injection molded polypropylene/polystyrene parts were investigated as a function of process history and injection sequence. For this purpose, a series of parts with PP skin/PS core, PS skin/PP core, and PP skin/PP core were prepared under selected mold temperatures and injection speeds and detailed structural analyses were performed using a series of structural analysis techniques. The optical microscopy, microbeam-WAXS and birefringence techniques revealed that crystalline orientation levels in PP are high when it is injected first to form the outer (skin) layer of the part. On going from the mold surface to the polystyrene surface the orientation level decreases slightly but remains high even at the PS/PP interface that is located at the interior of the part. This result is mainly caused by the additional deformation that the PP experiences as a result of secondary shearing by the polystyrene injection that occurs a short time delay after the primary injection. When PP is injected as a core layer, the orientation levels in PP were found to be low and mainly concentrated near the PP/PS interface. This low level of orientation is as a result of slower cooling that causes the relaxation of the chain orientation developed during the flow prior to the crystallization. In all polystyrene skin samples, the birefringence between the two skins was found to be the highest at the intermediate distances. When the injection speed of the core polypropylene is increased, this peak position shifts towards the mold surface as a result of shear heating. The use of low injection speeds in the core layer injection was found to distribute this layer more uniformly along the flow path. This is attributed to the attainment of increased levels of viscosity for the first injected layers during the course of injection of core layers at slower speeds.

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The solvent transport in poly(ethylene terephthalate) (PET) and related phenomena were investigated. Based on Harmon’s model for Case I (Fickian), Case II (swelling) and anomalous transport, the data of mass uptake were analyzed. Pure Case I or Case II behavior did not appear in our study and is affected by the annealing atmospheres and the preheating environments. The mass transport in PET is accompanied by a large-scale structural rearrangement, which leads to the induced crystallization of the original amorphous state. During this process, the matrix is under compressive stress. Solvent-induced crystallization was confirmed by X-ray diffraction (XRD), Differential Scanning Calorimeter (DSC), which is quite different from the thermal crystallization. The different behaviors of sorption between the solvent-treated PET crystallites and thermally treated PET can be explained in terms of the results of XRD, DSC and density measurement.

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EPDM containing dicyclopentadiene (DCPD) as diene monomer was hydroborated with 9-borabicyclo(3.3.1)nonane (9-BBN). The subsequent amination with monochloroamine was expected to result in EPDM with primary amine groups. The conversion of the residual unsaturation of DCPD of EPDM was complete, but the chemical structure of the amine-modified EPDM could not be fully elucidated. Hydrogenated DCPD (DCPDH), the low-molecular-weight analogue of DCPD incorporated in EPDM, was also hydroborated and aminated and the resulting product was isolated and extensively characterized. It was shown to consist of DCPDH coupled to 9-BBN via the B-atom with an NH unit inserted in one of the B–C bonds of the 9-BBN unit. The product is in fact a zwitterion RR'B-(OH)NH+R'', which converts to the neutral RR'BNHR'' upon dehydration. Using the analytical data of the low-molecular-weight product it was deduced that a similar structure is present in the amine-containing EPDM. Surprisingly, both amine-modified EPDM and DCPDH reacted as primary amines; for example, in the presence of anhydrides imides were formed. Finally, application of the amine-containing EPDM resulted in compatible blends of EPDM with poly(styrene-co-maleic anhydride).

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The ribbon-like nanopolymers were prepared by the cross-linking reaction of poly(a-methylstyrene)-block-poly(4-vinylpyridine) (PMSblock-P4VP) diblock copolymer films exhibiting P4VP cylindrical microdomains with the vapour of 1,4-dibromobutane in the solid state. It was indicated from the transmission electron microscopy (TEM) and the small-angle X-ray scattering (SAXS) that these cross-linked products had a structure of ribbon-like nanopolymers. It was found from the curve fitting on the static light scattering (SLS) intensity that such nanopolymers were in agreement with the conformation of the Gaussian model.

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A series of maleimide-terminated amorphous poly(dimethylsiloxanes) were synthesized from amino-terminated poly(dimenthylsiloxanes) with various molecular weights. The oligomers were characterized by Fourier transform infrared spectroscopy and proton magnetic resonance spectroscopy. Thermally induced polymerization kinetics was investigated using differential scanning calorimetry. Kinetic parameters could be obtained by a dynamic method. The results of these experiments are quite close to first-order reaction for the maleimide double bond polymerization, regardless of the length of the imide end-capped oligomers which can be explained from theory (reaction mechanism) and experiment. Apparent activation energies (Ea) in the range of 101.52–118.09 kJ/mol and pre-exponential factors (K0) in the range of 1.35 × 10 9 –1.63 × 10 11 min 21 were obtained.

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The effects of blend composition and take-up velocity on structural variations and physical properties of poly(ethylene terephthalate) [PET]/poly(ethylene-2,6-naphthalate) [PEN] blend fibres were studied using WAXS, n.m.r., d.s.c., density, tensile and thermal shrinkage tests. Over the ranges studied, the structure and properties of the blend fibres were significantly influenced by the composition and melt spinning velocity. With the increase in content of any second component (PEN or PET), the crystallization process in the as-spun fibres becomes difficult, because of the formation of random copolymers via a transesterification reaction occurring between PET and PEN molecules. This reaction also produces a miscible amorphous phase with the result that all blend samples exhibit a single glass transition temperature intermediate to those of the two homopolymers. The WAXS results of annealed samples, however, indicate separate crystals for the two components rather than a co-crystallization. Room temperature mechanical properties, for fibres spun at constant take-up velocity, improved gradually with increasing PEN content. The thermal shrinkage, however, is relatively high for blend fibres and reaches a maximum for the 50/50 PET/PEN blend, indicating that the copolymer chains are oriented fairly well, but exist in the amorphous state.

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Interpenetrating polymer networks (IPNs) of 2-hydroxyethyl methacrylate terminated polyurethanes (HPU) and polyurethanes (PU) with different ether-type polyols were prepared by simultaneous solution polymerization. Differential scanning calorimetry showed that the compatibility of polymers in IPN formation depends on the molecular weight of the prepolymers. Compatible IPN systems resulted in greater-than-average density values and reduced swelling behaviour. Water absorption of the IPNs was found to be mainly determined by the hard-to-soft segment ratio of the materials. The maximum tensile modulus occurred at a 25 wt% HPU content for the compatible systems and a 12.5 wt% HPU content for those that were incompatible. The maximum tensile strength occurred at a 25 wt% HPU content for all the IPN systems. Morphological observations using a scanning electron microscope revealed different fracture surfaces between the compatible and incompatible systems.

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