COMPATIBILIZATION OF HIGH-DENSITY POLYETHYLENE/POLYISOPRENE BLENDS WITH POLYETHYLENE/POLYISOPRENE THREAD-THROUGH COPOLYMERS

The compatibilization of high density polyethylene (HDPE)/polyisoprene (PI) blends with polyethylene/polyisoprene (PE/PI) ''thread-through'' copolymers was investigated. The proliferating structure of PE/PI with segments chemically identical to HDPE and PI, respectively, is different from that of graft copolymers. Studies showed that the dispersed domain size in the blends was significantly reduced and interfacial adhesion was improved by the compatibilization action of the copolymer. In the differential scanning calorimetry (DSC) analysis, the crystallization peak of HDPE in the blends became broad with adding the copolymer and fractionated crystallization appeared in the HDPE/PI blend compatibilized with the copolymer at a weight ratio of 30/70 while it appeared in the blend without copolymer at a weight ratio of 20/80. DMA results showed that by adding the copolymer, both the glass transition temperature (T-g) of the PI component and the alpha-relaxation of HDPE shifted to lower temperature, demonstrating the enhanced penetration of the two components. Mechanical properties of the blends were improved, especially the elongation at break, by the presence of the copolymers. The characteristic yielding at the fractured surface of the blends compatibilized with the copolymer indicates the fractural behavior of the material changed from brittle to tough.

MODIFICATION OF PP/HDPE BLENDS BY PP-PE SEQUENTIAL POLYMERIZATION PRODUCT

The morphology and mechanical properties of polypropylene/high-density polyethylene (PP/HDPE) blends in a wide range of compositions modified by a sequential Ziegler-Natta polymerization product (PP-PE) have been investigated. PP-PE contains multiple components such as PP, ethylene-propylene copolymer (EPC), and high molecular weight polyethylene (HMWPE). The effects of PP-PE on the mechanical properties and morphology of the PP/HDPE blends are the aggregative results of all its individual components. Addition of PP-PE to the blends not only improved the tensile strength of the blends, but the elongation at break increased linearly while the moduli were nearly unchanged. Morphological studies show that the adhesion between the two phases in all the blends of different compositions is enhanced and the dispersed domain sizes of the blends are reduced monotonously with the increment of the content of PP-PE. PP-PE has been demonstrated to be a more effective compatibilizer than EPC. Based on these results, it can be concluded that the tensile strength of the blends depends most on the adhesion between the two phases and the elongation at break depends most on the domain size of the dispersed component. (C) 1995 John Wiley & Sons, Inc.

NMR-STUDY ON THE RELATIONSHIP BETWEEN MISCIBILITY AND ANTIAGING PERFORMANCE OF BLENDS CONTAINING BLOCK-COPOLYMERS

The anti-aging performance of blends of polystyrene (PS), styrene-butadiene triblock copolymers (SBS), and PS/styrene-butadiene (SB)-4A (Carm star SE block copolymer) has been studied by means of C-13 NMR techniques. It is found that the anti-aging performance of these kinds of blends largely depends on their miscibility with PS of different molecular weight M(PS). The larger the quantities of PS solubilized in polybutadiene (PBD) domains, the better the anti-aging performance of the blends. It is also found that the anti-aging performance of these blends has dependence on molecular architectures of the SE block copolymers. For the aged blends, the double bonds of PBD were broken, meanwhile serious cross-linking networks formed in the blends. The proposed anti-aging mechanism is that the PS solubilized in PBD domains can efficiently prevent oxygen molecules from diffusing into PBD domains, therefore, successfully stop the oxidative process of PBD.

IN-SITU COMPOSITE - PHENOLPHTHALEIN POLYETHERSULFONE-THERMOTROPIC LIQUID-CRYSTALLINE POLYMER BLENDS

Phase behavior, thermal, theological and mechanical properties plus morphology have been studied for a binary polymer blend. The blend is phenolphthalein polyethersulfone (PES-C) with a thermotropic liquid crystalline polymer (LCP), a condensation copolymer of p-hydroxybenzoic acid with ethylene terephthalate (PHB-PET). It was found that these two polymers form optically isotropic and homogeneous blends by means of a solvent casting method. The homogeneous blends undergo phase separation during heat treatment. However, melt mixed PES-C/PHB-PET blends were heterogeneous based upon DSC and DMA analysis and SEM examination. Addition of LCP in PES-C resulted in a marked reduction of melt viscosity and thus improved processability. Compared to pure PES-C, the charpy impact strength of the blend containing 2.5% LCP increased 2.5 times. Synergistic effects were also observed for the mechanical properties of blends containing < 10% LCP. Particulates, ribbons, and fibrils were found to be the typical morphological units of PHB-PET in the PES-C matrix, which depended upon the concentration of LCP and the processing conditions.

PHASE-BEHAVIOR IN MIXTURES OF A HOMOPOLYMER AND A BLOCK-COPOLYMER .1. FTIR AND DSC STUDIES

Miscibility in blends of three styrene-butadiene-styrene and one styrene-isoprene-styrene triblock copolymers containing 28%, 30%, 48%, and 14% by weight of polystyrene, respectively, with poly(vinyl methyl ether) (PVME) were investigated by FTIR spectroscopy and differential scanning calorimetry (DSC). It was found from the optical clarity and the glass transition temperature behavior that the blends show miscibility for each kind of triblock copolymers below a certain concentration of PVME. The concentration range to show miscibility becomes wider as the polystyrene content and molecular weight of PS segment in the triblock copolymers increase. From the FTIR results, the relative peak intensity of the 1100 cm-1 region due to COCH3 band of PVME and peak position of 698 cm-1 region due to phenyl ring are sensitive to the miscibility of SBS(SIS)/PVME blends. The results show that the miscibility in SBS(SIS)/PVME blends is greatly affected by the composition of the copolymers and the polystyrene content in the triblock copolymers. Molecular weights of polystyrene segments have also affected the miscibility of the blends. (C) 1995 John Wiley & Sons, Inc.

STUDIES ON COMPATIBILIZATION OF POLYPROPYLENE THERMOPLASTIC POLYURETHANE BLENDS AND MECHANISM OF COMPATIBILIZATION

This paper reports a study of compatibilization and the mechanism of compatibilization of polypropylene (PP)/thermoplastic polyurethane (TPU) blends with maleated polypropylene (PP-MA) and its graft copolymer with polyethylene oxide (PEO), (PP-MA)-g-PEO.

COMPATIBILIZATION OF POLYPROPYLENE POLY(ETHYLENE OXIDE) BLENDS AND CRYSTALLIZATION BEHAVIOR OF THE BLENDS

The compatibilization of incompatible polypropylene (PP)/poly(ethylene oxide) (PEO) blends was studied. The experimental results showed that the graft copolymer [(PP-MA)-g-PEO] of maleated PP (PP-MA) and mono-hydroxyl PEO (PEO-OH) was a good compatibilize

EXCIMER FLUORESCENCE STUDY ON THE MISCIBILITY OF POLY(VINYL METHYL-ETHER) AND STYRENE-BUTADIENE STYRENE TRIBLOCK COPOLYMER

The excimer fluorescence of a triblock copolymer, styrene-butadiene-styrene (SBS) containing 48 wt% polystyrene was used to investigate its miscibility with poly(vinyl methyl ether) (PVME). The excimer-to-monomer emission intensity ratio I(M)/I(E) can be used as a sensitive probe to determine the miscibility level in SBS/PVME blends: I(M)/I(E) is a function of PVME concentration, and reaches a maximum when the blend contains 60% PVME. The cloud point curve determined by light scattering shows a pseudo upper critical solution temperature diagram, which can be attributed to the effect of PB segments in SBS. The thermally induced phase separation of SBS/PVME blends can be observed by measuring I(M)/I(E), and the phase dissolution process was followed by measuring I(M)/I(E) at different times.

ENTANGLEMENT FLUCTUATION DURING PHASE-SEPARATION IN POLYMER BLENDS

For perhaps the first time, the dynamics of liquid-liquid phase separation was studied by time-resolved mechanical spectrometry in order to establish the relationship between blends' properties and the phase structures during spinodal decomposition (SD). The selected system was chlorinated polyethylene (CPE)/ethylene-vinyl acetate copolymer (EVA). It was found that in the early and intermediate stage of SD, the storage modulus (G') and the loss modulus (G'') increase with time after the initiation of the isothermal phase separation; in the later stage, G' and G'' decrease as phase separation proceeds. An entanglement fluctuation model was presented to manifest this phenomenon; it was found that the rheological behavior agrees well with the expections of the model in the early stage. For the later stage, the reduction of G' and G'' can be attributed to the increment of phase-domain size. (C) 1993 John Wiley & Sons, Inc.

MISCIBILITY AND PHASE-BEHAVIOR IN BLENDS OF POLY(HYDROXYETHER OF BISPHENOL-A) WITH POLY(ETHYLENE OXIDE-CO-PROPYLENE OXIDE)

The miscibility of poly(hydroxyether of bisphenol A) (phenoxy) with a series of poly(ethylene oxide-co-propylene oxide) (EPO) has been studied. It was found that the critical copolymer composition for achieving miscibility with phenoxy around 60-degrees-C is about 22 mol % ethylene oxide (EO). Some blends undergo phase separation at elevated temperatures, but there is no maximum in the miscibility window. The mean-field approach has been used to describe this homopolymer/copolymer system. From the miscibility maps and the melting-point depression of the crystallizable component in the blends, the binary interaction energy densities, B(ij), have been calculated for all three pairs. The miscibility of phenoxy with EPO is considered to be caused mainly by the intermolecular hydrogen-bonding interactions between the hydroxyl groups of phenoxy and the ether oxygens of the EO units in the copolymers, while the intramolecular repulsion between EO and propylene oxide units in the copolymers contributes relatively little to the miscibility.

COMPATIBILIZING EFFECT OF POLY(ETHYLENE OXIDE)-B-POLYSTYRENE-B-POLY(ETHYLENE OXIDE) IN PHENOLPHTHALEIN POLY(ETHER ETHER KETONE) POLY(2,6-DIMETHYL-1,4-PHENYLENE OXIDE) BLENDS

The morphology and mechanical behaviour of phenolphthalein poly(ether ether ketone) (PEK-C)/poly(2,6-dimethyl-1,4-phenylene oxide) (PPO) blends has been investigated. A poly(ethylene oxide)-b-polystyrene-b-poly(ethylene oxide) (PEO-PS-PEO) triblock copolymer was used as compatibilizer. It was found that PEO-PS-PEO has a compatibilizing effect on the PEK-C/PPO blends. The addition of PEO-PS-PEO to the blends greatly improves phase dispersion and interfacial interfacial adhesion and also enhances the ultimate tensile strength and Young's modulus at compositions ranging from 30 to 70% PEK-C. However, all the values of the ultimate tensile strength within the whole composition range are lower than those expected by simple additivity, probably owing to the poor mechanical properties of PEO-PS-PEO copolymer.

XPS STUDY ON TERNARY CROSSLINKED BLOCK-COPOLYMER FROM CONDENSATION OF OLIGODIMETHYLSILOXANE WITH POLY-PARA-HYDROXYSTYRENE AND POLYARYLSULFONE OLIGOMERS

XPS has extensively been applied to the study of polymers, in which a considerably important topic is the surface phase separations in block copolymers and blends. Copolymers (or blends) will produce a phase separation if their components are in-

Studies on NBR/PVC Blends

Studies conducted on butadiene-acrylonitrile copolymer (NBR)/poly(vinyl chloride) (PVC) blends at different temperatures indicate that an optimum temperature exists for the formation of a particular blend. The mechanical properties of the blends confirm this observation. PVC stabilizer based on, magnesium oxide , zinc oxide, and stearic acid was found to be very useful in NBR/PVC blends.

Novel adhesive systems based on neoprene-phenolic blends

The aim of the investigation is to develop new high performance adhesive systems based on neoprene-phenolic blends. Initially the effect of addition of all possible ingredients like fillers, adhesion promoters, curing agents and their optimum compositions to neoprene solution is investigated. The phenolic resin used is a copolymer of phenol-cardanolformaldehyde prepared in the laboratory. The optimum ratio between phenol and cardanol that gives the maximum bond strength in metal-metal, rubber-rubber and rubber-metal specimens has been identified. Further the ratio between total phenols and formaldehyde is also optimised. The above adhesive system is further modified by the addition of epoxidized phenolic novolacs. For this purpose, phenolic novolac resins are prepared in different stoichiometric ratios and are subsequently epoxidized. The effectiveness of the adhesive for bonding different metal and rubber substrates is another part of the study. To study the ageing behaviour, different bonded specimens are exposed to high temperature, hot water and salt water and adhesive properties have been evaluated. The synthesized resins have been characterized by FTIR , HNMR spectroscopy. The molecular weights of the resins have been obtained by GPC. Thermogravimetric analysis and differential scanning calorimetry are used to study the thermal properties. The fractured surface analysis is studied by scanning electron microscopy. The study has brought to light the influence of phenol/ formaldehyde stoichiometric ratio, addition of cardanol (a renewable resource), adhesion promoters and suitability of the adhesive for different substrates and the age resistance of adhesive joints among other things.

Synthesis and Characterization of Novel Ionomers based on Styrene Butadiene Copolymer

Novel thermo-reversible zinc sulphonated ionomers based on styrene butadiene rubber (SBR), and high styrene rubber (HSH) were synthesized by sulphonation followed by neutralization with zinc. The sulphonate content of the ionomer was estimated by using x-ray fluorescence spectroscopy. Presence of sulphonate groups has been confirmed by FTIR and FTNMR spectra. The TGA results show improvement in the thermo~oxidative stability of the modified rubber. Both DSC and DMTA studies show that the incorporation of the ionic groups affect the glass rubber transition of the base polymer. lntroduction ol ionic functionality in to the base material improved the physical properties. Retention of the improved physical properties of the novel ionomers even after three repeated cycles of mixing and molding may be considered as the evidence for the reprocessability of the ionomer. Effect of particulate fillers (HAF black, silica and zinc stearate) on the properties of the zinc sulphonated styrene butadiene rubber ionomer has been evaluated. Incorporation of tillers results in improvement in mechanical properties. Zinc stearate plays the dual role of reinforcement and plasticization. The evaluation of dielectric properties of zinc sulphonated styrene butadiene rubber iorpmers at microwave frequencies reveal that the materials show conductivity at semiconductor level. The real and imaginary parts of the complex permittivity increases with increase in ionic functionality. Use of the 38.5 ZnS-SBR ionomer as a compatibiliser for obtaining the technologically compatible blends from the immiscible SBR/NBR system has been discussed.