Crystallization behaviour of poly(phenylene sulphide)/polystyrene blend

High-resolution solid-state 13C nuclear magnetic resonance study on poly(vinyl alcohol)/poly(vinylpyrrolidone) blends

Abstract: The miscibility and domain structure of poly(vinyl alcohol)/poly(vinylpyrrolidone) (PVA/PVP) blends are investigated by high-resolution solid-state 13 C nuclear magnetic resonance methods. The observed 13 C spectra and the intermolecular cross-polarization of the blends suggest a hydrogen-bonding interaction between the two polymers. 1 H T 1 and T 1 ϱ results indicate that the blends are miscible at all compositions on a scale of 200–300 A. On a scale of 20–30 A, however, the miscibility of the blends depends significantly on the composition. When the PVA composition is more than 46 wt%, the blends are composed of two phases, an amorphous miscible phase of PVP plus PVA and a pure PVA phase. The crystallinity of the PVA phase decreases rapidly with decreasing PVA composition. When the PVA composition is less than 46 wt%, the blend is completely miscible. The composition of PVA phase in the blends was inferred from the results of 1 H T 1 ϱ .

Effect of CaCO3 on the crystallization behaviour of polypropylene

Abstract: The effect of CaCO3 on the crystallization behaviour and the modification of structure in polypropylene (PP) has been investigated using X-ray diffraction and optical microscopy. The crystallization half time deduced from spherulitic growth rate was found to vary sharply and decreased considerably from 5–6 min for pure polymer to less than 2 min in the presence of CaCO3. The ultimate spherulite size also decreased considerably for PP containing CaCO3. Its dependance on composition however, showed a plateau region at about 10–15 wt % of additive. The intensities of certain reflections especially the 130 and 040 of the α phase were greatly affected by the presence of CaCO3 and large variations in the crystallinity (Ci) values were observed with composition. The ratio of intensities of 130 and 040 reflections and theCi revealed a maximum at a certain concentration of CaCO3. The above results can be explained on the basis of nucleation and preferential growth of the α phase of PP crystallites.

Crystallization behavior of polyphenylene sulfide in blends with a liquid crystalline polymer

Abstract: Blends of polyphenylene sulfide (PPS) with a commercial, wholly aromatic, liquid crystal copolyesteramide (Vectra-B950) have been prepared by meltblending. The crystallization behavior of neat and blended PPS has been studied by differential scanning calorimetry (DSC), under both non-isothermal and isothermal conditions. It has been found that blending PPS with Vectra-B leads to an increase of the temperature of non-isothermal crystallization and to a pronounced acceleration of the isothermal crystallization, without any reduction of the degree of crystallinity. All these effects have been found to occur independent of the Vectra-B concentration, within the investigated range (2 to 20%, w/w). The results have been interpreted in terms of an incrased nucleation density of the blends, probably due to heterogeneous substances, initially present in the Vectra-B bulk, which dissolve to saturation in the PPS phase, during melt-blending.

Effect of casting solvent on the crystallization in PEO/PMMA blends

Abstract: The crystallization in polyethylene oxide/polymethyl methacrylate (PEO/PMMA) blends was investigated with respect to composition and different casting solvents. Sharp changes in the intensities of the major reflections (120 and 112/004 from PEO) were observed in their X-ray diffraction scans when these blends were cast from different solvents. Large deviations were noted in the crystallinity values as well as the intensities of the peaks from those expected from simple rules of mixture or dilution law. The various results could be explained on the basis of restricted growth of the PEO crystallites along certain directions in the presence of PMMA.

Miscibility of poly(vinyl alcohol)/poly(methacrylic acid) and poly(vinyl alcohol/poly(acrylic acid) systems. II. High-resolution solid-state CP/MAS 13C NMR studies.

Abstract: Miscibility of poly(vinyl alcohol)/poly(methacrylic acid) complexes and poly(vinyl alcohol)/poly(acrylic acid) blends is investigated by high-resolution 13C solid-state NMR method. Observed 13C spectra are discussed in terms of hydrogen-bonding effects on chemical shift. The results indicate that poly(vinyl alcohol) and poly(methacrylic acid) are intimately mixed on a scale of 20–30 A due to intermolecular hydrogen bonding to form equimolar-ratio complexes. For the poly(vinyl alcohol)/poly(acrylic acid)=1/1 blend, the two polymers are also miscible, the crystalline phase of PVA is destroyed completely and no detectable domain can be observed for the blend on a scale of 20–30 A. Poly(vinyl alcohol)/poly(acrylic acid)=2/1 and 1/2 blends are homogenous on a scale of 200–300 A, but heterogeneous on a smaller scale.

The crystal structure of poly-p-phenylene sulphide

Abstract: The structure of crystalline poly-p-phenylene sulphide has been determined through the application of X-ray diffraction methods. The structure appears to be similar to that of poly-p-phenylene oxide. The orthorhombic unit cell ( a = 8 · 67 A , b = 5 · 61 A and c ( fibre axis) = 10 · 26 A ) contains four monomeric units. The space group is PbcnD2h14. Two molecular chains pass through the unit cell-one through the centre and the other through a corner. The sulphur atoms of a molecular chain are arranged in a zig-zag manner in the (100) plane. The planes of the phenylene groups are alternately at +45° and −45° to the (100) plane. The sulphur bond angle is about 110°, just as in aliphatic sulphide polymers.

Applications of polymer blends: Emphasis on recent advances

Abstract: In the past decade, polymer blend technology has achieved an important position in the field of polymer science. With increased academic and industrial research interest, the application of polymer blend technology to commercial utility has grown significantly. This review on the applications of polymer blends will cover the major commercial blends in the categories of styrene-based polymer blends, poly(vinyl chloride) blends, polyacrylate blends, polyester and polycarbonate blends, polyolefin blends, elastomer blends, polyelectrolyte complexes, and interpenetrating polymer networks. New developments in polymer blend applications will be discussed in more detail. These systems include linear low-density polyethylene blends with either low- or high-density polyethylene, styrenemaleic anhydride terpolymer/ABS (acrylonitrile-butadiene-styrene) blends, polycarbonate/poly(butylene tetephthalate) blends, new PPO/polystyrene blends, and tetramethyl bisphenol A polycarbonate/impact polystyrene blends. Areas for future research to enhance the potential for polymer blend applications will be presented. The need for improved methods for predicting miscibility in polymer blends is discussed. Weldline strength is a major property deficiency of two-phase systems (even those with mechanical compatibility), and future research effort appears warranted to resolve this deficiency. The use of polymeric compatibilization additives to polymer blends has shown promise as a method to improve mechanical compatibility in phase-separated blends, and will be expected to be the subject of future research programs. Finally, the reuse of polymer scrap is discussed as a future application area for polymer blends. Unique applications recently proposed for polymer blends include immobilization of enzymes, permselective membranes, reverse osmosis membranes, selective ion-exchange systems, and medical applications using polyelectrolyte complexes.

Thermo-optical and differential scanning calorimetric observations of mobility transitions in polystyrene-poly(2,6-dimethyl-1,4-phenylene oxide) blends

Abstract: Transition temperatures by thermo-optical analysis (TOA) and by DSC were measured on films of polystyrene (PS), poly(2,6-dimethyl-1,4-phenylene oxide) (PPO resin) and nine homogeneous blends of these polymers. The TOA procedure consists of automatically monitoring light transmission through birefringent scratches in a film during heating at constant rate in a microscope hot stage between crossed (90°) plane polarizers. The TTOA transition temperature, defined as the temperature of birefringence disappearance in the scratches, increased monotonically from 113°C for pure PS to 222°C for pure PPO resin at a 10°/min heating rate. The Tg (DSC) similarly ranged from 99°C to 212°C at a 20°/min heating rate. The TOA technique as described should be a useful addition to thermomechanical studies of transparent polymers and polymer blends.