| 1. |
- Altskär, Annika, et al.
(författare)
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Some effects of processing on the molecular structure and morphology of thermoplastic starch
- 2008
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Ingår i: Carbohydrate Polymers. - : Elsevier BV. - 0144-8617 .- 1879-1344. ; 71:4, s. 591-597
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Tidskriftsartikel (refereegranskat)abstract
- Hydroxypropylated and oxidised potato starch (HONPS) was used together with glycerol and water to produce thermoplastic starch. The amount of glycerol was kept constant at 22 parts by weight per 100 parts of dry starch. The thermoplastic starch was converted into films/sheets using three different processing techniques; casting, compression moulding and film blowing. The last two methods represent typical thermoplastic conversion techniques requiring elevated processing temperatures. By means of size-exclusion chromatography, it was found that compression moulding and film blowing led to some degradation of high-molecular weight amylopectin as well as of high-molecular weight amylose-like molecules. The degradation was significantly less pronounced for the cast films. The morphology of the specimens was quite complex and phase separations on different levels were identified. In the cast films and, to a lesser extent, in the compression-moulded specimens, a fine network structure could be distinguished. Such a structure could however not be ascertained in the film-blown material and this is discussed in terms of the thermo-mechanical treatment of the starch materials. © 2007 Elsevier Ltd. All rights reserved.
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| 2. |
- Arino, I., et al.
(författare)
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The Influence of the Measuring/Viewing Angle on the Color of Injection-Molded Plastics
- 2010
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Ingår i: International Journal of Polymeric Materials and Polymeric Biomaterials. - : Informa UK Limited. - 0091-4037 .- 1563-535X. ; 59:4, s. 292-306
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Tidskriftsartikel (refereegranskat)abstract
- A multi-angle spectrophotometer was used to measure the CIELab coordinates L∗, a∗ and b∗ in different angles relative to the incident light. The specimens used were acrylonitrile-butadiene-styrene injection-molded plaques in different colors and with different surface textures. Variations in the coordinates when changing the measuring angle depended on the color and the texture. In general, however, smooth (glossy) surfaces were measured to be darker and of higher chroma than textured surfaces and as the gloss of the surfaces decreased (due to texturing), the lightness of the surfaces increased and the absolute values of a∗ and b∗ decreased over the range of measuring angles (not too close to the specular reflection angle). A psychometric study involving a human test panel was used as a complement to the measurement. The agreement between the measurements and this study cannot be said to be satisfactory, unless the variation in the color coordinates was quite clear. Possible reasons are discussed.
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| 3. |
- Arino Marine, Ruth, 1980, et al.
(författare)
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Barrier screw compounding and mechanical properties of EAA copolymer and cellulose fiber composite
- 2013
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Ingår i: International Polymer Processing. - : Walter de Gruyter GmbH. - 0930-777X .- 2195-8602. ; 28:4, s. 421-428
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Tidskriftsartikel (refereegranskat)abstract
- The difficulty of feeding cellulose fibers and thermoplastics into the extruder or injection molding machine is addressed, this being a serious problem in the production of cellulose fiber composites for industrial applications. Agglomerates consisting in cellulose fibers and ethylene-acrylic acid copolymer (EAA) with different cellulose contents and different fiber lengths were processed with two different screws in order to better understand how the dispersion of the fibers can be improved by melt extrusion. A conventional screw with a compression ratio of 4 : 1 and a screw with barrier flights were used at different screw rotation speeds. The fiber length and fiber content were measured and microscopic analyses were performed in order to estimate the number and size of the cellulose fiber aggregates in the final composites. It was concluded that the barrier screw was more effective than the conventional screw in breaking up the fiber aggregates and dispersing the fibers. More but smaller cellulose aggregates were observed when the barrier screw was used, and the reduction of length was significantly greater for long than for short fibers. In contrast to that was expected, the samples containing the shorter fibers had better mechanical properties, probably due to a better dispersion of the fibers.
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| 4. |
- Arino Marine, Ruth, 1980, et al.
(författare)
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Injection molding of beverage container caps made of a composite consisting of wood cellulose fiber and an ethylene-acrylic acid copolymer
- 2014
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Ingår i: International Polymer Processing. - : Walter de Gruyter GmbH. - 0930-777X .- 2195-8602. ; 29:4, s. 507-514
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Tidskriftsartikel (refereegranskat)abstract
- The influence of processing parameters on injection-molded bottle caps consisting of 20 wt% of cellulose fibers and an ethylene-acrylic acid copolymer was studied. The study included three cylinder barrel temperatures and three mold temperatures. For each combination of temperatures, the holding pressure time was varied and the mold sealing time was determined. High density polyethylene caps were also produced as reference material, and injection-molded tensile test bars were also produced in order to assess the tensile mechanical properties. The results showed no major differences in sealing time for the caps containing cellulose fibers, except for the highest melt and mold temperatures where a slightly longer time was observed. The viscosity of the composite material was higher than that of the polymeric matrix. For the highest temperature and high shear rates, the viscosity of the composite material was close to the viscosity of the matrix material. The moisture content of the injection-molded bars was less than 1%, showing that almost no water was absorbed during the compounding or after several months. The crystallinity decreased when the fibers were included but was not influenced by the mold temperature. Enhanced mechanical properties were obtained by using the fibers compared to the pure ethylene-acrylic acid copolymer, both in the tensile test bars and in the caps. The reference high density polyethylene had, however, a higher mechanical performance than the composite.
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| 5. |
- Arino Marine, Ruth, 1980, et al.
(författare)
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Melt processing of wood cellulose tissue and ethylene-acrylic acid copolymer composites
- 2013
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Ingår i: International Polymer Processing. - : Walter de Gruyter GmbH. - 0930-777X .- 2195-8602. ; 28:4, s. 429-436
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Tidskriftsartikel (refereegranskat)abstract
- The difficulty of feeding cellulose fibers together with the polymer into the melt processing equipment is a serious disadvantage for the production of cellulose-containing composites on a large scale. In the present work, a continuous method of feeding cellulose in the form of a tissue into a twin-screw extruder through an opening downstream of the extruder cylinder was studied. With this method, composites with different fiber contents were obtained. The tissues used were one made mainly of softwood fibers and another mainly of hardwood fibers. In order to better understand how to improve the fiber dispersion by melt mixing, a second extrusion was performed with a single screw extruder with a barrier-flighted screw and also with the twin-screw used to compound the tissue with the polymer. The compounds produced were then injection molded into test bars. The test bars containing the softwood tissue exhibited some fiber aggregates also after a second extrusion, whereas no fiber aggregates were observed in samples made with the tissue containing hardwood fibers and two passes through the twin screw. The fiber length was in general reduced by each melt processing stage and the shortest fiber length was observed after two extrusions with the twin-screw and injection molding. The tensile modulus increased with increasing fiber content. A higher stiffness was obtained with more softwood fibers in the tissue whereas more hardwood fibers gave a higher tensile strength and greater elongation at break.
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| 6. |
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| 7. |
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| 8. |
- Arino Marine, Ruth, 1980, et al.
(författare)
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Processing and mechanical properties of thermoplastic composites based on cellulose fibers and ethylene-acrylic acid copolymer
- 2012
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Ingår i: Polymer Engineering and Science. - : Wiley. - 0032-3888 .- 1548-2634. ; 52:9, s. 1951-1957
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Tidskriftsartikel (refereegranskat)abstract
- The melt processing and the tensile mechanical properties of composites consisting of 30 wt% softwood kraft pulp cellulose fibers and ethylene-acrylic acid copolymer (EAA) with 7% acrylic acid content were studied. The compounding techniques used were extrusion mixing performed with a single screw extruder and elongation dispersive mixing performed with the injection-molding machine. All blends were injection-molded in a final step. Fiber length, fiber content, and mechanical properties were measured and the number and the size of the fiber aggregates were determined by microscopy analysis. It was concluded that two passes of elongation dispersive mixing had a beneficial effect on the mechanical properties, which could be related to the fewer and smaller amounts of aggregates. The different types of processing performed had a small or insignificant effect on the fiber length since the fiber lengths measured were within the same range as that of the starting material. POLYM. ENG. SCI., 52:1951-1957, 2012. © 2012 Society of Plastics Engineers Copyright © 2012 Society of Plastics Engineers.
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