Crystallization Behavior in Poly(propylene) Containing Wollastonite Microfibrils
TL;DR: In this article, the structure development and crystallization behavior of poly(propylene) (PP) filled with wollastonite mineral was studied with respect to different particle sizes of the filler.
Abstract: The structure development and crystallization behavior of poly(propylene) (PP) filled with wollastonite mineral was studied with respect to different particle sizes of the filler. The decrease in particle size led to increase in crystallization rates and decrease of crystallization half time, indicating greater nucleation efficiency for smaller sizes of the wollastonite particles. This was also reflected in the higher crystallinity values obtained for small filler particles. The WAXD analysis of PP/wollastonite revealed significant changes in the relative intensity of certain peaks (110 reflection) at small particle size, indicanting preferential growth of PP on wollastonsite. The exact co-relationship of nucleation rate/crystallization rate and the additive particle size (d) was determined which showed that for any given concentration of the additive, it was proportional to (I/d) 3 .
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TL;DR: In this paper, an accelerated weathering test was carried out on wood-polypropylene composites containing mineral fillers, including calcium carbonate, wollastonite and talc.
Abstract: Accelerated weathering tests were carried out on wood–polypropylene composites containing minerals. Three different mineral fillers were studied: calcium carbonate, wollastonite and talc. Colour changes were evaluated after distinct periods; the total time of exposure of the composites to UV irradiation was 2000 h. The weathering resulted in significant colour fading of the composites. The composites containing mineral fillers had higher changes of colour (lightness) than the reference composite. Scanning electron microscopy analysis revealed deterioration of the polymer surface layer in all weathered composites. Exposure of the reference composite to UV irradiation resulted in the disappearance of the polypropylene surface layer and disclosure of wood fibres, which led to a higher drop in the lignin content of this composite compared to mineral-containing composites. A substitution of part of the wood with mineral fillers resulted in decreased water absorption and thickness swelling of mineral-containing composites, compared to the reference composite. Exposure to water immersion-freeze–thaw cyclic treatment and UV irradiation led to a decrease in the Charpy impact strength of the composites, except for the composite containing talc.
33 citations
TL;DR: In this article, the authors investigated the crystallization behavior, structure, and morphology of polypropylene composites containing different fillers such as silica, calcium carbonate, talc, mica, graphite, etc.
Abstract: The crystallization behavior, structure, and morphology developed was investigated for polypropylene containing different fillers such as silica, calcium carbonate, talc, mica, graphite, etc. by using compression-molded samples prepared at several cooling rates. It was observed that the crystallinity obtained for any given composition depended on the thermal conductivity of the filler and the PP composite containing it as well as the cooling rate to which it was subjected. These composites exhibited skin-core type of morphology and the skin layer thickness was found to depend not only on the cooling rate but also on the type of filler, its thermal conductivity, etc. These various experimental findings were discussed in light of the phenomenological model described in our earlier work, which correlates thermal conductivity and degree of crystallinity for various compositions of PP containing additives. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 615–623, 2004
32 citations
TL;DR: In this article, a wood plastic composite was prepared by mixing wood fibrils into polypropylene with an internal mixer and nano wollastonite was dispersed in the composite to compensate for the poor thermal characteristics of the product.
Abstract: Wood plastic composite was prepared by mixing wood fibrils into polypropylene with an internal mixer. Nano wollastonite was dispersed in the composite to compensate for the poor thermal characteristics of the product. Thermal properties of the obtained composite were studied by different techniques including thermo gravimetrical analysis, differential scanning calorimetry, limited oxygen index and oxidative induction time. It was found that introduction of nano wollastonite increased thermal stability as well as crystallinity in the composite due to high specific surface area of nano inorganic fiber filler. Also, flammability resistance and the required oxygen content to burn the composite were enhanced as wollastonite was added to the wood plastic composite. However, wollastonite increased oxidation of the sample because it is composed of metal oxides.
27 citations
Cites background from "Crystallization Behavior in Poly(pr..."
...It can be a result of nano inorganic fibers which act as nucleation agents and accelerate the crystallization process of the nano composite in comparison to pure PP (Saujanya et al. 2002; Ning et al. 2007; Chen et al. 2008)....
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...It could be due to high specific surface area of the nano filler which involved more chains to attain crystals around nucleus (Saujanya et al. 2002)....
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TL;DR: In this article, the authors examined the thermal conductivity of polypropylene-filler composites with a standard model for various fillers such as calcium carbonate, talc, silica, wollastonite, mica, and carbon fibers.
Abstract: The thermal conductivity of a filler and the thermal conductivity of a composite made from that filler influence the heat-transfer process during melt processing. The heat-transfer process from the melt to the mold wall becomes an important factor in developing the skin–core morphology. These aspects were examined in this study. The thermal conductivity of polypropylene–filler composites was estimated with a standard model for various fillers such as calcium carbonate, talc, silica, wollastonite, mica, and carbon fibers. The rate of cooling under given conditions, including the melting temperature, mold wall temperature, mass of the composite, and filler content, was estimated with standard heat-transfer equations. The time to attain the crystallization temperature for polypropylene was evaluated with a regression method with differential temperature steps. The crystallization curves were experimentally determined for the different fillers, and from them, the induction period for the onset of crystallization was estimated. These observations were correlated with the expected trends from the aforementioned formalism. The excellent fit of the curves showed that in all these cases, the thermal conductivity of the filler and composite played a dominant role in controlling the onset of the crystallization process. However, the nucleation effects became important in the later stages after the crystallization temperature was attained. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 2994–2999, 2003
21 citations
TL;DR: Results suggest that three types of inorganic particle in this system promote the crystallinity of PPDO and act as an effective nucleating agent.
Abstract: In this work, poly(para-dioxanone) (PPDO) was mixed with 1% (by weight) calcium carbonate (CaCO(3)), beta-tricalcium phosphate (beta-TCP), or calcium sulphate dihydrate (CSD) by solution co-precipitation. Samples were compression molded into bars using a platen-vulcanizing press. The morphology, thermal and mechanical properties, and crystalline structure of the composites were investigated using differential scanning calorimetry, polarized optical microscopy, scanning electron microscopy, and X-ray diffraction. All results suggest that three types of inorganic particle in this system promote the crystallinity of PPDO and act as an effective nucleating agent: the relative degree of crystallinity of PPDO increased from 30.74% to 100%, and the crystallization temperature of PPDO was increased by 18 degrees C. On the other hand, the mechanical properties of PPDO were changed by the presence of inorganic particles: the tensile strength of PPDO/CSD increased by 11.46%.
15 citations