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Abstract  

In this work, the influence of attapulgite concentration on the nucleating efficiency of isotactic polypropylene (iPP) and on the kinetics of non-isothermal crystallization were ascertained.The study was conducted by DSC. The nucleating efficiency was determined according to the procedure described by Fillon and the kinetics of non-isothermal crystallization was determined using Ozawa's method using cooling rates of 2, 5 and 10C min−1.Our results indicate that both the relative crystallinity and the crystallization temperature increase with filler content and that a maximum occurs at 2% mass/mass filler content. Both parameters decrease with increasing cooling rates. The Ozawa's exponent tended to increase with temperature and filler content.

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) Direction of heat transfer Fabrics The fabrics were made from polypropylene multifilament yarns on an interlock knitting machine. Six types of knitted fabrics with different constructional parameters: mesh, cardigan loop

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Abstract  

The interest in lignocellulosic composites has been growing in recent years because of their specific properties. In this study, a new technique of wood treatment using γ-irradiation was used. This research focuses on the influence of the gamma irradiation on the chemical composition of wood and on the nucleation ability of polypropylene matrice. The inner morphology of the transcrystalline layer was investigated using hot stage optical microscopy. Differential scanning calorimetry was used to investigate the kinetic parameters of polypropylene crystallization in the presence of wood surface. The results showed that the gamma irradiation can decrease the content of the cellulose in the wood, but it has a slightly negative effect on the transcrystallization process of polypropylene. This treatment also affects the crystal conversion and the half-time of PP crystallization. These results suggested that the gamma irradiation of wood may play a useful role in changing the microstructure of the matrice near the wood. It was observed that the nucleation of the wood surface was selective, indicating that the chemical characteristics of the lignocellulosics might have influence on the polypropylene crystallization. A possible mechanism for the appearance of transcrystallinity involving chemical composition of lignocellulosic is also proposed.

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Abstract  

In this study, isothermal crystallisation kinetic data of poly(propylene terephthalate) (PPT) are obtained using differential scanning calorimetry (DSC) and polarized light microscopy (PLM). Data from each method are analyzed according to the secondary nucleation theory of Lauritzen–Hoffmann and the procedures and results are critically presented. The assumption that the growth rates obtained from PLM can be equally well described from crystallisation rate data using the half-crystallisation time, is tested.

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Abstract  

An intelligent hydrogel with both pH and temperature sensitivity was obtained by grafting acrylic acid and dimethylaminoethylmethacrylate onto preirradiated polypropylene (PP) film by two-step reactions. The effect of first and second reactions on the degree of grafting was studied. The grafted sample films were checked by Fourier transform infrared spectrophotometry in the attenuated total reflectance mode. The morphology of the PP samples was observed by scanning electron microscope in different conditions before and after grafting, respectively.

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Abstract  

Monitoring of personnel working with enriched uranium implies development of techniques for excreta analysis, mainly for urine, with very low detection limits.The method described allows the determination of enriched uranium after extraction in tri-n-octylphosphine oxide (TOPO), 0.5M in toluene, supported on polypropylene capillary columns1. Alpha activity is later measured in a low background liquid scintillation equipment2 and a fluorimetric determination is performed3 with detection limits for 800 ml of urine of 12±4 mBq/l and 0.08±0.01 ug/l.

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Abstract  

Transport of uranyl ions through liquid membranes consisting of tri-n-butylphosphate (TBP) in kerosene oil supported in Celgard 2400 polypropylene microporous film has been studied. Various parameters, such as the effect of nitric acid concentration in the feed solution, TBP concentration in the organic membrane phase, stripping agent concentration and temperature on the flux of uranium across the liquid membrane, have been investigated. The results obtained have been used to elucidate the mechanism of uranium transport and stoichiometry of the diffusing species.

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Abstract  

A discussion on the influence of grafted polar groups (succinic anhydride and succinil-fluorescein) in glass transition behaviour of atactic polypropylene is shown in this work, on the basis of the reaction conditions used to obtain the modified polymers, kind and amount of grafted groups, and the degradation processes which may take place. The Box-Wilson experimental design methodology for two independent variables (reactant concentration to obtain the modified polymer) has been used to follow variations in glass transition temperatures. The existence of undesired degradation processes is considered as independent of the grafting reactions, and the model predictions seem to agree with this latter.

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Summary The influence of calcium carbonate nanoparticles with different shapes (spherical and elongated) on the thermal properties and crystallization behavior of isotactic polypropylene was investigated. CaCO3 nanoparticles were covered by an appropriate coating agent to improve the interfacial adhesion between the filler and the polyolefin matrix. The nanocomposites were prepared by melt mixing and subsequent compression molding. A remarkable effect of CaCO3 on the thermal properties of iPP was observed. Moreover, the analysis of crystallization kinetics showed that CaCO3 nanopowder coated with PP-MA are efficient nucleating agents for iPP, and the overall crystallization rate results higher than plain iPP.

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The effects of low-density polyethylene or isotactic polypropylene on the thermal properties of ethylene-propylene-diene rubber were examined by using a rheometer and a derivatograph. Pronounced changes in the thermal properties of the rubber were observed as a result of the polyolefin addition.

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