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The thermal and crystallization behaviour of polyphenylene sulfide (PPS) in its blends with high density polyethylene (HDPE) is reported. Three grades of HDPE ranging in MFI from 0.4 to 52 were used in the investigation. The effect of composition and molecular weight of HDPE on the crystallization process and morphology of PPS in the blends has been investigated by the technique of Differential Scanning Calorimetry (DSC).

The thermal and crystallization behaviour of polyphenylene sulfide (PPS) in its blends with high density polyethylene (HDPE) is reported. Three grades of HDPE ranging in MFI from 0.4 to 52 were used in the investigation. The effect of composition and molecular weight of HDPE on the crystallization process and morphology of PPS in the blends has been investigated by the technique of Differential Scanning Calorimetry (DSC).

Addition of metal halides to nylons has been shown to be advantageous in a number of ways. The decrease in melting temperature, increase in glass transition temperature and melt viscosity by such additions have allowed more convenient processing of low molecular weight polymers and thermally unstable polymers. Rheological data depicting the variation of melt viscosity with shear rate at temperatures relevant to processing are necessary in optimizing and trouble-shooting plastics processing operations. In the present paper, a method has been proposed to estimate, complete flow curves or rheograms of nylon—metal halide systems with the use of a master curve knowing the melt flow index and glass transition temperature of the system. The validity of the approach has been verified for the nylon 6—lithium chloride system and shown to hold good for any nylon—metal halide combination.

The dynamic mechanical, electrical and magnetic properties of highly filled magnetic polymeric composites containing 75 to 85 wt % barium ferrite in a thermoplastic elastomer matrix styrene-isoprene-styrene (SIS), are reported. The dependence of the properties on the volume fraction of the filler has been investigated. It is shown that the toughness and shore hardness of the composite may be correlated to its dynamic mechanical parameters. The use of coupling agents for surface treatment of ferrites has been shown to improve the magnetic properties of the composite due to better filler dispersion.

A method proposed earlier has been extended to estimate complete flow curves or rheograms of engineering plastics. Master curves that are independent of the grade and temperature have been generated and presented for acrylics, polyacetal, nylons, polyethylene terephthalate, polycarbonate and polysulfone. The influence of the various molecular parameters on the viscosity behaviour of polymer melts have been explained rationally. More specifically, the effects of chain branching and of chain rigidity on the master curve of a resin type have been elucidated with reference to polyacetal and polysulfone, respectively. The method presented here can be used effectively by processors of engineering plastics.

The modification of structure, crystallinity and orientation have been studied in powder processed polytetrafluoroethylene by various techniques. It was found that crystallinity (as determined from regression curve analysis) in unsintered samples decreased with increase of compaction pressure while in sintered specimen it increased with increase of pressure. The crystallinity was also found to vary inversely with logarithm of cooling rate. Microfocus X-ray diffraction revealed the orientation of c-axis lying preferentially in the plane perpendicular to applied pressure. There was slight variation in the lattice dimension especially the c-axis in completely sintered specimen. The infrared studies showed the presence of some of the bands depended upon the molding/sintering conditions. These various findings have been explained on the basis of compaction and recrystallization behaviour under constrained conditions.

Polymer blends have received a lot of attention in recent years due to the possibility of getting compounds with novel and/or different properties through proper marriage of the properties of the respective mono-components. The flow behaviour of blends when subjected to stresses is complex and is often found not to vary monotonically with composition. Mixing rules and mixture theories have been used for estimating melt viscosity of a blend at zero shear rate. However a knowledge of the entire rheogram is desirable for process optimization, process design and trouble shooting.In the present paper a method proposed earlier to estimate the rheograms of polymer melts through the use of the melt flow index has been extended to polyblends. A method for obtaining the melt flow index of the polymer blends at various compositions from the melt flow index of the individual components and the blend ratio has been suggested based on the altered free volume state model. Curves that are coalesced using the melt flow index of the blend at different blend ratios have been presented for a polypropylene-high density polyethylene blend, a high density polyethylene-polymethyl methacrylate blend, a polystyrene-polymethyl-methacrylate blend, a polystyrene-polyacetal blend and a polymethylmethacrylate-polyacetal blend.

The crystaIIinity, particle size and morphology of polyphenylene sulphide synthesized under various conditions have been investigated by X-ray diffraction and scanning electron microscopy. It was found that crystaIIinity decreased from 71 to 66% with increase of reaction time. The growth of particle size as well as total polymer mass followed a time dependence of the formX =X0 (1 -e-at) The particle size distribution curve was noted to be sharp centring at 3 µn for short reaction time, high speed of stirring and also for low concentration of reactants. The particle morphology showed very strong dependence on various reaction parameters. Intricate sheaf-like morphology was noted for the particles at long reaction times or low stirring speeds while oblong platelet type two-dimensional morphology was noted when a low concentration of reactants was used.

This paper concerns poly(hexamethylene) ureas produced by the technique of interfacial polycondensation. The polymer has been produced under various conditions of preparation and aspects of its structure have been elucidated using x-ray diffraction, differential scanning calorimetry, and other thermal analyses such as ther-mogravimetric analysis. The polymer has been shown to be a high-melting thermoplastic, with a melting point of about 285°C. The polymer is semicrystalline. The rate at which the polymerization takes place has an important influence on the crystal structure and the degree of crystallinity of the polymer as formed, and hence offers the possibility of manipulating the structure through a choice of preparation conditions. Chemical treatment of the formed polymer is another possible way of manipulating the structure, and some exploratory experiments on end capping show promise in this direction.

Acid-catalyzed polycondensation of phenol and crotonaldehyde results in soluble thermoplastic resins over a broad range of compositions. The thermal and curing behavior of the resins are found to vary markedly with the phenol to crotonaldehyde mole ratio and the purity of crotonaldehyde. Infrared analysis of the resins and their fractions separated by column chromatography indicates that all the resins are structurally similar. The number-average molecular weights of the resins fall in the range of 400 to 600. The resins from distilled crotonaldehyde exhibit higher molecular weights than those from crude crotonaldehyde. The thermal properties of the resins are comparable to the Novolak-type phenol-formaldehyde resins. The thermoplastic nature is retained even at higher fraction of crotonaldehyde, unlike for the conventional Novolak resins.

The crystallinity, particle size and morphology of polyphenylene sulphide synthesized from 1, 4-dibromobenzene and sodium sulphide have been investigated by X-ray diffraction and scanning electron microscopy. It was found that the crystallinity increased from 62 to 68% with an increase in reaction time. A reordering of crystalline structure with increase of reaction time was also noted. The particle size growth was slower as compared to the reaction rate and the distribution was very sharp. The results are compared with those for polyphenylene sulphide obtained from 1, 4-dichlorobenzene and sodium sulphide.

The structure development during melt curing of poly(phenylene sulfide) (PPS) is reported. The changes in the structure were monitored using various characterization techniques such as differential scanning calorimetry, thermogravimetric analysis, infrared spectroscopy, and optical microscopy. It was observed that the thermal parameters such as melting point and heat of fusion are very sensitive to the structural changes and can be effectively used to monitor the curing process. The effect of curing environment was also investigated, and it was found that the rate of change of structure is considerably higher in air than in nitrogen. The results are discussed on the basis of the different mechanisms for curing of PPS.

The nonisothermal and isothermal crystallization behavior of the thermoplastic copolyester based on 1-4 cyclohexane dimethanol, ethylene glycol, and terephthalic acid was investigated by differential scanning calorimetry. The copolyester is normally an amorphous polymer with the cyclic moiety in the main chain suppressing crystallization. However, the amorphous pellets crystallize during the heating mode. The crystallization behavior from the glassy solid state was found to be influenced by the melt temperature and the dwell time at the melt temperature. The onset of crystallization shifts progressively to lower temperatures, and the peak becomes narrower with increasing melt temperature and dwell time. The isothermal crystallization time at a given temperature of crystallization was also found to decrease significantly with increasing melt temperature. Thus, the crystallizing ability of the polymer and the rate of crystallization were found to be influenced by the melt temperature and the dwell time. The results are interpreted in terms of the temperature-dependent equilibrium ratio between the two possible chain conformations corresponding to the "Trans" and "gauche" forms of the cyclohexane moiety in the chain.

Asphalt materials are used in a variety of applications such as road paving, waterproofing, roofing membranes, adhesive binders, rust proofing and water resistant coatings. There are available in a number of grades distinguished in terms of their softening point and flow resistance. The selection of the proper grade of asphalt for a particular application is governed by the desired flow behaviour. A knowledge of the complete flow curve depicting the variation of melt viscosity with shear rate at the relevant temperatures is necessary not only for proper grade selection, but also for specifying processing conditions for aggregate mixing and spraying. The rheological data are also useful in assessing end use performance. The scientific techniques for generating the rheological data involve the use of expensive, sophisticated instruments. Generation of the necessary flow data using these instruments is beyond the financial and technical means of most processors of asphalt materials. The engineering techniques involving the use of inexpensive vacuum viscometers are relatively easy, but provide a single point viscosity measurement at low shear rate. In the present work, a method is proposed for unifying the viscosity versus shear rate a data at various temperatures for a number of asphalt grades. A master curve has been generated that is independent of the grade of asphalt and the temperature of viscosity measurement. The master curve can be used to generate rheograms at desired temperatures for the asphalt grade of interest, knowing its zero-shear viscosity at that temperature.

The properties of molded PPS parts are dependent on the crystalline morphology developed during processing. Even though processed under identical conditions, the crystalline morphology may differ owing to the differences in the crystallization process. The crystallization behaviour of a polymer is known to depend on its molecular architecture which in turn depends upon polymerization process. Thus the study of the crystallization behaviour of polymer with reference to its molecular architecture is essential for obtaining product with desirable properties. In the present paper, the crystallization behaviour of two grades of polyphenylene sulfide was investigated using differential scanning calorimetry (DSC). An attempt has been made to explain the differences in the crystallization behaviour of PPS samples on the basis of the differences in their molecular architecture. The structural differences of PPS manifest themselves in terms of the depression in the equilibrium melting point, retardation of nucleation and overall crystallization rate and coarsening of spherulitic texture.

Thin films of polyphenylene sulphide (PPS) and polyethylene (PE) polymers have been deposited in a bilayer configuration using pulsed excimer laser ablation. Such bilayer specimens have been annealed at different temperatures, up to a maximum of 120°C, and for different time intervals, up to a maximum of 110 min, to investigate the evolution of the interface. By employing the technique of spectroscopic ellipsometry, the nature and the degree of thermally induced polymeric transport across the interface are brought out.

Solid thermoplastic resins were prepared by acid-catalyzed condensation of phenol and crotonaldehyde (both crude and distilled). The thermal and curing properties were compared with the conventional phenol-formaldehyde (PF) novolak resins. Phenol-crotonaldehyde (PC) resins were found to be thermoplastic even after curing with the crosslinking agent hexamethylenetetramine up to 160°C. This curing behavior was observed irrespective of the purity of the crotonaldehyde or the phenol-to-crotonaldehyde mole ratio in the resin. Postcuring of these resins at elevated temperatures yielded insoluble and infusible thermoset products. This unique thermal characteristic could lead to interesting processing possibilities for the resins. The technical feasibility of thermoplastic processing of the PC resins followed by postcure heat treatment for transforming the molded part into a thermoset has been demonstrated.

The temperature dependence of the rate of solid-state polymerization of trithiane was investigated in conjunction with calorimetric measurements of the heat capacity of the irradiated monomer as a function of temperature. It was found that the rate of change of entropy with temperature exhibited a maximum at about 175° C. The curve of per cent polymerization versus isochronal, post-irradiation polymerization temperature also peaked at some 175° C. Finally, the existence of a crystalline phase-transition in the monomer at about 194° C was discovered by DSC and was confirmed by X-ray powder diffraction and by optical microscopy. Two models which may interrelate this set of phenomena are suggested.