Effect of lamellar thickness on the epitaxial crystallization of PE on oriented iPP films

The effects of lamellar thickness on the epitaxial crystallization of polyethylene on the oriented isotatic polypropylene have been studied by means of transmission electron microscopy. The results obtained from the bright field electron microscopy and electron diffraction show that the epitaxial orientation of the PE crystals on the iPP substrate depends not only on the thickness of the oriented iPP lamellae, but also on the lamellar thickness of PE crystals. No epitaxial orientation relationship between PE crystal and iPP substrate can be found, when the PE crystals are thicker than the lamellar thickness of iPP along the matching direction. This suggests, that the epitaxial nucleation of PE in the PE/iPP epitaxial system is controlled not only by the chain-row matching, but also by a secondary nucleation process.

Use of SAXS to characterize the morphology of poly(polyethylene glycol diacrylate)/epoxy resin interpenetrating networks

Interpenetrating polymer networks (IPNs) have been synthesized from prepolymers that form miscible blends. All IPNs made from polyacrylate ((polyethylene glycol diacrylate), PEGDA) and epoxy (diglycidyl ether of bisphenol A, DGEBA) can be made in phase separated states by incorporating crosslinks. However, blends of these prepolymers, having a negative Flory-Huggins interaction parameter, are highly miscible. This indicates that formation of IPNs favours phase separation relative to blends. The microphase separation characteristics in the PEGDA/DGEBA IPNs were determined using smalt-angle X-ray scattering (SAXS). The Debye-Bueche and Guinier methods were used to calculate the correlation lengths of the segregated phases existing in the PEGDA/DGEBA IPNs. The results from SAXS showed that the size of the phase segregation zones changed with composition from about 50 to 100 Angstrom.

Morphology and mechanical properties of PP/HMWPE blends

Mechanical properties and morphology of blends of polypropylene (PP) with high molecular weight polyethylene (HMWPE) prepared by coprecipitation from xylene solution are investigated. Compared to blends of PP with commercial high-density polyethylene (HDPE), the mechanical properties of the blends of PP/HMWPE are much superior to those of PP/HDPE blends. Not only is the tensile strength stronger, but also the elongation at break is much higher than that of the PP/HDPE blends of the same composition. These differences increase with increasing HMWPE and HDPE content. Scanning electron microscopy of the fracture surface resulting from the tensile tests shows that the compatibility in PP/HMWPE blends is much better than that in PP/HDPE blends. This is most likely attributable to the enhanced chain entanglement of HMWPE with the PP in the amorphous phase due to the lower crystallinity, owing to the high molecular weight of the HMWPE, and a much more flexible chain. The thermal behavior and spherulite morphology of both blends are also investigated.

The phase inversion and morphology of nylon 1010 polypropylene blends

Noncompatibilized and compatibilized blends of nylon 1010/PP blends having five different viscosity ratios were prepared by melt extrusion. Glycidyl methacrylate-grafted-polypropylene (PP-g-GMA) was used as the compatibilizer to enbance the adhesion between the two polymers and to stabilize the blend morphology. The effect of the viscosity ratio on the morphology of nylon 1010/polypropylene blends was investigated, 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. Investigation of the morphology of the blends by microscopy indicated that the smaller the viscosity ratio (eta(PP)/eta(PA)) the smaller was the polypropylene concentration at which the phase inversion took place and polypropylene became the continuous phase. The compatibilizer induced a sharp reduction of particle size, but did not have a major effect on the phase-inversion point. An improvement :in the mechanical properties was found when nylon 1010 provided the matrix phase. (C) 1996 John Wiley & Sons, Inc.

Studies on morphology and crystallization of polypropylene/polyamide 12 blends

Scanning electron microscopy (SEM) and an image analyser are used to study morphologies of the fractured surface, etched by hot phenol, of polypropylene/maleated polypropylene/polyamide 12 PP/PP-MA/PA12) = 65/10/25 blend and PP-MA/PA12 = 75/25 blend. The particle dimension and its distribution of PA12 dispersed phase in these blends are much lower and narrower than that of the PP/PA12. blends. Especially, most of the particles in the PP-MA/PA12 = 75/25 blend are smaller than 0.1 mu m. The effect of the morphology of PP/PA12 blends on their crystallization behaviour is studied using differential scanning calorimetry and SEM. PA12 dispersed phase coarsens during annealing in the PP/PP-MA/PA12 = 65/10/25 blend. The mechanism of coarsening of the PA12 dispersed phase is a coalescence process. The intense mixing between the PP component and the PA12 component through reaction of PP-MA and PA12 leads to a change of dynamic mechanical behaviour of the components. A separation method is used to separate the polyolefin parts (precipitated from hot phenol), from PA12 parts (hot phenol filtrate). Of PP/PP-MA/PA12 = 65/10/25 blend, infra-red measurements and elementary analysis show that the precipitate has a lower PA12 content than the feed, whereas the filtrate has a higher PA12 content. From PP-MA/PA12 = 75/25 blend, PA12 contents in the precipitate and the filtrate are the same as in the feed. This implies that all PA12 has reacted with all PP-MA in the latter case while not in the former case. Using the method of interface exposure, interfacial reaction of PP-MA with PA12 is studied by X-ray photoelectron spectrometry (X.p.s.). Copyright (C) 1996 Elsevier Science Ltd.

Morphological studies on a novel poly(aryl ether ketone)

The morphology of a novel poly(aryl ether ketone) [PEDEKmK] was investigated via polarizing optical microscopy (POM), TEM, DSC, SAXS and electron diffraction (ED). A distinct change in lamellar thickness, orientation, and spherulitic morphology was observed due to crystal melting and recrystallization. However, the crystal packing mode is found to be identical before and after the recrystallization process.

Miscibility, crystallization, and morphology studies of thermosetting polyimide PMR-15/PEK-C blends

Miscibility, crystallization, and mechanical properties of blends of thermosetting polyimide PMR-15 and phenolphthalein poly(ether ketone) (PEK-C) were examined. With the exception of the 90/10 blend, which has two glass transition peaks, all the blends with PMR-15 less than 90 wt % are miscible in the amorphous state according to DMA results. Addition of PEK-C hindered significantly the crystallization of PMR-15, indicating that there must exist some kind of interaction between molecular chains of PMR-15 and those of PEK-C. The semi-IPN system of PMR-15/PEK-C blends exhibits good toughness. Two distinct microphases, interweaving at the phase boundaries, were found in the PMR-15/PEK-C 60/40 blend. The toughness effect of the blends is discussed in terms of the interface adhesion between the two distinct phases and the domain sizes of the phases. The relation between miscibility and toughness of the blends was investigated. (C) 1996 John Wiley & Sons, Inc.

MORPHOLOGY AND DYNAMIC-MECHANICAL PROPERTIES OF NYLON 66/POLY(ETHER IMIDE) BLENDS

The morphology and dynamic mechanical properties of blends of poly(ether imide) (PEI) and nylon 66 over the full composition range have been investigated. Torque changes during mixing were also measured. Lower torque values than those calculated by the log-additivity rule were obtained, resulting from the slip at the interface due to low interaction between the components. The particle size of the dispersed phase and morphology of the blends were examined by scanning electron microscopy. The composition of each phase was calculated. The blends of PEI and nylon 66 showed phase-separated structures with small spherical domains of 0.3 similar to 0.7 mu m. The glass transition temperatures (T(g)s) of the blends were shifted inward, compared with those of the homopolymers, which implied that the blends were partially miscible over a range of compositions. T-g1, corresponding to PEI-rich phase, was less affected by composition than T-g2, corresponding to nylon 66-rich phase. This indicated that the fraction of PEI mixed into nylon 66-rich phase increased with decreasing PEI content and that nylon 66 was rarely mixed into the PEI-rich phase. The effect of composition on the secondary relaxations was examined. Both T-beta, corresponding to the motion of amide groups in nylon 66, and T-gamma, corresponding to that of ether groups in PEI, were shifted to higher temperature, probably because of the formation of intermolecular interactions between the components.

IN-SITU AFM STUDY OF THE SURFACE-MORPHOLOGY OF POLYPYRROLE FILM

In this paper we focus on the surface morphology of polypyrrole film by using in situ atomic force microscopy (AFM). The formation process of polypyrrole film and the transformation process of the film from the oxidized to reduced state were clearly observed.

EFFECT OF ETHYLENE-PROPYLENE COPOLYMER WITH RESIDUAL PE CRYSTALLINITY ON MECHANICAL-PROPERTIES AND MORPHOLOGY OF PP/HDPE BLENDS

Morphology and mechanical properties of polypropylene (PP)/high density polyethylene (HDPE) blends modified by ethylene-propylene copolymers (EPC) with residual PE crystallinity were investigated. The EPC showed different interfacial behavior in PP/HDPE blends of different compositions. A 25/75 blend of PP/HDPE (weight ratio) showed improved tensile strength and elongation at break at low EPC content (5 wt %). For the PP/HDPE = 50/50 blend, the presence of the EPC component tended to make the PP dispersed phase structure transform into a cocontinuous one, probably caused by improved viscosity matching of the two components. Both tensile strength and elongation at break were improved at EPC content of 5 wt %. For PP/HDPE 75/25 blends, the much smaller dispersed HDPE phase and significantly improved elongation at break resulted from compatibilization by EPC copolymers. (C) 1995 John Wiley & Sons, Inc.

THE COMPATIBILITY AND MORPHOLOGY OF CHITOSAN-POLY(ETHYLENE-OXIDE) BLENDS

Thermal behavior and morphology of blends prepared by solution casting of mixtures of chitosan and poly( ethylene oxide) were studied by means of differential scanning calorimetry (DSC) and scanning electron microscopy (SEM). The preliminary results indicate that both melting point and crystallinity depend on the composition of the blends, and that they exhibit minimum values when the blend contains 50% chitosan. From the prediction of melting point depression analysis, the compatibility of the blends shows a transition at this specific composition. This conclusion was further confirmed by observation of the morphology.

NMR-STUDY OF MISCIBILITY AND MORPHOLOGY OF POLYIMIDE POLYIMIDE BLENDS

The miscibility and morphology of polyimide/polyimide blends, PEI-E/PTI-E(a)) and PBPI-E/IPTI-E(a)), have been studied by means of C-13 CPMAS NMR technique. The results indicate that PEI-E/PTI-E blends are miscible on a molecular level, but molecular aggregation exists in pure PBPI-E specimen as well as PBPI-E/PTI-E blends with high content of PBPI-E, which vanishes in the blends with high content of PTI-E. When the content of PBPI-E is higher than that of PTI-E, the addition of PTI-E to PBPI-E has almost no effect on the size of the PBPI-E rigid domains, but has a large effect on the populations of the PBPI-E rigid domains. It is the intermolecular charge-transfer interaction that plays a critical role in the miscibility of PEI-E/PTI-E and PBPI-E/PTI-E blends.

MISCIBILITY, MICROSTRUCTURE, AND DYNAMICS OF BLENDS CONTAINING BLOCK-COPOLYMER .2. MICROSTRUCTURE OF BLENDS OF HOMOPOLYSTYRENE WITH STYRENE-BUTADIENE BLOCK-COPOLYMERS

The microstructures of styrene-butadiene triblock (SBS) and styrene-butadiene four-arm star block (SB-4A) copolymers and their blends with homopolystyrene (PS) of different molecular weights, MPS, have been investigated by means of small-angle X-ray scatt

GLASS-TRANSITION AND CRYSTALLIZATION OF POLY(VINYL ALCOHOL)-G-POLY(METHYL METHACRYLATE) GRAFT-COPOLYMERS

The glass transition behaviour, microphase separation morphology and crystallization of poly(vinyl alcohol)-g-poly(methyl methacrylate) graft copolymers (PVA-g-PMMA) were studied. A lamellar microphase separation morphology was formed, even for a copolyme