Compatibilization of polyamide 6/isotactic polypropylene blends was investigated by mechanical, morphological, thermal, and rheometrical methods. The primary objective was to obtain blends combining the desirable properties of the two components. Four compatibilizers including maleic anhydride, fumaric acid, or glycidyl functionalities were applied at two concentrations (5 and 10%). Maleic anhydride grafted styrene-ethylene-butylene-styrene block copolymer (SEBS-g-MAH) was observed to give excellent mechanical properties, especially at high polyamide/polypropylene ratios. The correlation between morphology and mechanical and rheological properties is discussed, and the interesting effect of blending on the kinetics of crystallization is noted.

SYNOPSISIn polymer blends, the crystallization of the dispersed semicrystalline component depends on the type and distribution of the nucleating heterogeneities and on the level of the dispersion. Either fractionated or coincident crystallization may result. In this study, the effect of compatibilizers on the crystallization of polyamide 6/isotactic polypropylene ( P P ) blends was investigated. The morphology was controlled with 10 w t % of four different commercial compatibilizers-PPgMAH, EBAgFA, SEBSgMAH, and E-EA-GMA-each leading to specific morphology and crystallization behavior. The compatibilized blends show more complex crystallization compared with the corresponding binary blends. In the compatibilized blends, the dispersed PA6 seems to crystallize coincidently with PP, probably due to its small particle size. The crystallization of PP takes place a t temperatures above the bulk value at all compositions in blends compatibilized with PPgMAH and blends without the compatibilizer. By contrast, in blends compatibilized with EBAgFA, SEBSgMAH, and E-EA-GMA, the crystallization takes place either at PP bulk temperature or over the temperature range of 76-87"C a t the cooling rate of 10°C/min. The amount of the shift cannot be explained solely by the size of the PP dispersion. 0 1993

Superior impact properties were obtained when maleic anhydride grafted styrene ethylene/butylene styrene block copolymer (SEBS‐g‐MAH) was used as a compatibilizer in blends of polyamide 6 (PA 6) and isotactic polypropylene (PP), where polyamide was the majority phase and polypropylene the minority phase. The optimum impact properties were achieved when the weight relation PA:PP was 80:20 and 10 wt% SEBS‐g‐MAH was added. The blend morphology was systematically investigated. Transmission electron microscopy (TEM) indicated that the compatibilizer forms a cellular structure in the PA phase in addition to acting as an interfacial agent between the two polymer phases. In this cellular‐like morphology the compatibilizer appears to form the continuous phase, while polyamide and polypropylene form separate dispersions. In microscopy, PA appeared as a fine dispersion and PP as a coarse dispersion. The mechanical properties indicated that in fact PA, too, is continuous, and the blend can be interpreted as possessing a modified semi‐interpenetrating network (IPN) structure with separate secondary dispersion of PP. The coarser PP dispersion plays an essential role in impact modification. Binary blends of the compatibilizer and one blend component were also investigated separately. The same cellular structure was observed in the binary PA/SEBS‐g‐MAH blends, and SEBS‐g‐MAH again appeared to form the continuous phase when the elastomer concentration was at least 10 to 20 wt%. By contrast, in PP/SEBS‐g‐MAH only conventional dispersion of elastomeric SEBS‐g‐MAH was observed up to 40 wt% elastomer. Impact strength was improved and the elastic modulus was lowered in both PA/SEBS‐g‐MAH and PP/SEBS‐g‐MAH blends when the elastomer content was increased. The changes in modulus indicate that the semi‐IPN‐like structure is formed in the binary PA/SEBS‐g‐MAH blends as well as in the ternary structure.

SYNOPSISThe rheological properties of the blend components are an important parameter in the formation of a blend morphology. The effect of viscosity ratio on the morphology of polyamide 66/polypropylene blends was studied, with primary attention to the phase-inversion behavior and the average particle size of the dispersed phase. The relationship between the mechanical properties and the phase-inversion composition was investigated as well. Noncompatibilized and compatibilized blends having five different viscosity ratios were prepared by twin-screw extrusion. Maleic anhydride-grafted polypropylene was used as the compatibilizer to increase the adhesion between the two polymers and to stabilize the blend morphology. Investigation of the morphology of the blends by microscopy (SEM and TEM) showed that the smaller the viscosity ration (QP..,/Q~~) the smaller was the polyamide 66 concentration a t which the phase inversion took place and that polyamide 66 became the continuous phase. The results are in accord with the model of Jordhamo. The compatibilizer induced a sharp reduction of particle size, but did not have a major effect on the phaseinversion point. The tensile and impact properties of the compatibilized blends were found to correlate with the phase inversion. An improvement in the mechanical properties was observed when polyamide 66 provided the matrix phase.

SYNOPSISBinary blends of a reactive ethylene-based terpolymer with polybutylene terephthalate (PBT) and with a liquid crystalline polyester (LCP) were studied to clarify the possible interactions between the blended polymers. The aim was to determine the suitability of the reactive terpolymer containing epoxy reactivity as a compatibilizer in blends of polypropylene (PP) and these two polyesters. The binary blends exhibited increased viscosity during blending, changes in the crystallization of the P B T phase, and a n intimate contact between the blended polymers, which pointed to strong interactions or chemical reactions between the compatibilizer and both P B T and LCP. FTIR analysis confirmed the reaction of the epoxide and formation of new esters. Most probably the carboxyl end groups of the polyesters reacted with the epoxy group of the compatibilizer. In the second part of the work the same terpolymer was shown to act as a compatibilizer in PP/PBT and PP/LCP blends. This behavior was based on good mixing with the PP phase and on the chemical reactivity or strong interactions with the polyesters demonstrated in the investigations on binary blends. Addition of 5 wt % of the compatibilizer improved the impact strength, especially in P P / P B T blends where synergistic behavior was found a t compositions of 801 20 and 20/80. In PP/LCP blends, the compatibilizer significantly improved the impact strength of unnotched samples at 20 wt % LCP content. In both blends, the compatibilizer reduced the size of the dispersed domains and caused them to attach better in the matrix.