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- Rigdahl, M, et al.
(författare)
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The clustering mechanism underlying a kinetic model related to Bose-Einstein statistics
- 2004
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Ingår i: Mechanics of time-dependant materials. - 1385-2000 .- 1573-2738. ; 8:2, s. 95-103
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Tidskriftsartikel (refereegranskat)abstract
- The present paper discusses the clustering of elementary events in a kinetic relaxation model based on a time-domain analog of Bose-Einstein statistics. The clustering results in a spectrum of relaxation times which are integer-valued fractions of the relaxation time of single events, thus providing a stretching of the overall process towards shorter times. The predictions of the model are combined with an expression describing the 'universal' behaviour of solids of various structure and composition in a stress relaxation experiment. This yields the remarkable result that the average cluster size relating to the entire process is six. Correspondingly, the average relaxation time is found to be 1/6 of the relaxation time of the single events.
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- Thunwall, M., et al.
(författare)
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Processing and properties of mineral-interfaced cellulose fibre composites
- 2008
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Ingår i: Journal of Applied Polymer Science. - : Wiley. - 0021-8995 .- 1097-4628. ; 107:2, s. 918-929
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Tidskriftsartikel (refereegranskat)abstract
- Polypropylene (PP) or, in some cases, poly (lactic acid) (PLA) were compounded with cellulosic fibres. The amount of fibres used was in the range 10-30 vol % and, in case of PP, a series of compounds was prepared with a minor amount of maleated PP as a compatibiliser. This matrix was denoted MAPP. Before compounding the polymers and the fibres, undelaminated bentonite (industrial scale) or delaminated clay (nanoclay) was deposited on the fibres in different amounts to improve the dispersion of the fibres in the polymer matrix, i. e., to avoid detrimental fibre bundles. The PP-based compounds were either extruded or injection moulded, whereas the PLA-compounds were only injection moulded. The mechanical properties were primarily evaluated for the injection moulded specimens. In general, the fibres had a strong effect on the mechanical behaviour of the materials, especially in the case of PLA and MAPP. Treating the fibres with undelaminated clay or nanoclay improved to some extent the dispersion of the fibres and the mechanical performance of the composites, but further optimization of the function of the mineral in this respect is probably required. The combination of the mineral treatment with a debonding agent appeared to be an interesting route here. With such a combination, a visually very good dispersion of the fibres in the PP-based matrix could be obtained, partly at the expense of the mechanical performance. The compounding of the cellulosic fibres with PP led in this case to a marked decrease in the fibre length. © 2007 Wiley Periodicals, Inc.
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- Arino, I., et al.
(författare)
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On the relation between surface texture and gloss of injection-molded pigmented plastics
- 2005
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Ingår i: Polymer Engineering and Science. - : Wiley. - 0032-3888 .- 1548-2634. ; 45:10, s. 1343-1356
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Tidskriftsartikel (refereegranskat)abstract
- The relation between the surface topography of injection-molded plastic objects with deliberately imposed textures and their gloss, measured by means of a conventional glossmeter at incident angles of 20 degrees, 60 degrees and 85 degrees, was investigated. A modification of the general scalar Kirchhoff approximation, which accounts for geometrical features of the glossmeter, is used to describe the experimental gloss values of the textured surfaces. The agreement between the measured and the calculated values for incidence angles of 20 degrees and 60 degrees confirms the usefulness of the approach, though several of the textured surfaces used here are too rough for the Kirchhoff theory to be strictly valid. A poorer agreement, however, was noted at higher incidence angles (85 degrees in this case). For very smooth surfaces (without any texture), the classical Bennett-Porteus theory could in many cases describe the gloss level with sufficient accuracy. The influence on the measured gloss of the polymer material (in terms of its refractive index) and the color of the injection-molded object is also discussed. Light beige specimens in three different polymeric materials (acrylonitrile-butadiene-styrene, acrylonitrile-butadiene-styrene/polycarbonate blend, and polypropylene) as well as three acrylonitrile-butadiene-styrene products with different colors were used. The refractive index of the polymer had no major influence on the measured gloss. The gloss level increased slightly with increasing lightness of the specimens, which can be associated with an increased contribution from the bulk scattering. However, the surface texture governed most of the gloss variations.
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