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Composite Foams (composite + foam)
Selected AbstractsDevelopment of an extrusion system for producing fine-celled HDPE/wood-fiber composite foams using CO2 as a blowing agentADVANCES IN POLYMER TECHNOLOGY, Issue 4 2004H. Zhang Abstract This paper presents an innovative design of a tandem extrusion system for fine-celled foaming of plastic/wood-fiber composites using a physical blowing agent (PBA). The plastic/wood-fiber composites utilize wood-fibers (WF) as a reinforcing filler in the plastic matrix and are known to be advantageous over the neat plastics in terms of the materials cost and some improved mechanical properties such as stiffness and strength. However, these improvements are usually accompanied by sacrifices in the ductility and impact resistance. These shortcomings can be reduced by inducing fine-celled or microcellular foaming in these composites, thereby creating a new class of materials with unique properties. An innovative tandem extrusion system with continuous on-line moisture removal and PBA injection was successfully developed. The foamed composites, produced on the tandem extrusion system, were compared with those produced on a single extruder system, and demonstrated significant improvement in cell morphology, resulting from uniform mixing and effective moisture removal. The effects of WF and coupling agent (CA) on the cell morphology were studied. An increase in the WF content had an adverse affect. The cell morphology and foam structures were improved when an appropriate CA was added. © 2004 Wiley Periodicals, Inc. Adv Polym Techn 23: 263,276, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/adv.20016 [source] Composites of rigid polyurethane foam and cellulose fiber residueJOURNAL OF APPLIED POLYMER SCIENCE, Issue 6 2010M. C. Silva Abstract Rigid polyurethane composite foams were prepared with cellulose fibers as a filler. The cellulose fibers were an industrial residue of blanched cellulose pulp production. The influence of the cellulose fiber concentration on the structural, thermal, mechanical, and morphological properties of the foams was investigated. We also studied the influence of the cellulose fibers on the foam's resistance to fungal attack by placing a suspension of known fungus in contact with the surface of the foam and following the morphological evolution as a function of time (for 60 days). The increase in the cellulose filler concentration in the foams, up to 16% w/w with respect to the polyol, changed their properties as follows: (1) the cell size decreased, (2) the thermooxidative stability and mechanical properties remained approximately constant, (3) the thermal conductivity decreased slightly, and (4) fungal growth was observed. Therefore, a cellulosic fibrous industrial residue was rationally valorized as a filler in classical rigid polyurethane foams; this yielded materials with mechanical resistance and a susceptibility to fungi in a wet environment. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010 [source] Using Chitosan as a Nucleation Agent in Thermoplastic Foams for Heavy Metal AdsorptionMACROMOLECULAR SYMPOSIA, Issue 1 2009Milton O. Vázquez Abstract Thermoplastics/chitosan-powder composite foams were prepared by extrusion using azodicarbonamide (ACA) as chemical blowing agent. The effect of chitosan content on morphology (cell size, nucleation density and foam density) of the foams was studied. Chitosan particles are located on the bubbles periphery. Morphological quantification showed that foam cell size decreased and cell population increased with addition of chitosan into polymeric matrix from 1 to 10%. Further, optimum chitosan content was obtained for each polymer. Polymers foamed with chitosan were tested as a chelating resin to adsorb chromium (Cr VI) from different concentration solutions. [source] Effect of eggshell powder as nucleating agent on the structure, morphology and functional properties of normal corn starch foams,PACKAGING TECHNOLOGY AND SCIENCE, Issue 3 2007Yixiang Xu Abstract Corn starch and eggshell powder (with particle sizes of 4,5µm and 8,10µm) composite foams were prepared by extrusion. Effects of eggshell on the structure, morphology, physical properties (unit density and expansion ratio), mechanical properties (spring index and compressibility) and thermal behaviour (thermal transition and stability) of the foams were investigated. Foam cell size decreased and cell population increased with addition of eggshell into starch matrix. The foam unit density, expansion ratio and compressibility decreased significantly (p < 0.05), while the spring index increased significantly (p < 0.05) as the eggshell content increased from 0 to 6wt%. Further increasing eggshell content to 10wt% increased the unit density and compressibility and decreased the expansion ratio and spring index. The thermal transition and stability increased with the addition of eggshell. The optimum eggshell content was 6wt% and the smaller-sized eggshell powder had a favourable effect on the functional properties of the foams. Copyright © 2006 John Wiley & Sons, Ltd. [source] Formation and characterization of polyurethane,vermiculite clay nanocomposite foamsPOLYMER ENGINEERING & SCIENCE, Issue 9 2008T. Umasankar Patro Nanocomposites of rigid polyurethane foam with unmodified vermiculite clay are synthesized. The clay is dispersed either in polyol or isocyanate before blending. The viscosity of the polyol is found to increase slightly on the addition of clay up to 5 pphp (parts per hundred parts of polyol by weight). The gel time and rise time are significantly reduced by the addition of clay, indicating that the clay acts as a heterogeneous catalyst for the foaming and polymerization reactions. X-ray diffraction and transmission electron microscopy of the polyurethane composite foams indicate that the clay is partially exfoliated in the polymer matrix. The clay is found to induce gas bubble nucleation resulting in smaller cells with a narrower size distribution in the cured foam. The closed cell content of the clay nanocomposite foams increases slightly with clay concentration. The mechanical properties are found to be the best at 2.3 wt% of clay when the clay is dispersed in the isocyanate; the compressive strength and modulus normalized to a density of 40 kg/m3 are 40% and 34% higher than the foam without clay, respectively. The thermal conductivity is found to be 10% lower than the foam without clay. POLYM. ENG. SCI., 2008. © 2008 Society of Plastics Engineers [source] Expansion mechanisms of plastic/wood-flour composite foams with moisture, dissolved gaseous volatiles, and undissolved gas bubbles,POLYMER ENGINEERING & SCIENCE, Issue 7 2003G. M. Rizvi The large quantity of moisture in wood-flour may lead to the deterioration of the cell structure of foamed plastic wood-flour composites in terms of cell size, non-uniformity, and poor surface quality. Since these anomalies can cause poor mechanical properties of the foamed composites, the removal of the moisture from wood-flour becomes a critical issue with respect to the improvement of these properties. The wood-flour in this experimental study was first oven-dried at different temperatures and then subjected to acetone extraction and thermogravimetric analysis (TGA). The oven-dried wood-flour was blended with plastic and then subjected to extrusion foaming. The results obtained from the TGA studies indicate that most volatiles were released from the extractives. Conversely, a comparative experimental study of the foaming behavior of these plastic/wood-flour composites versus that of undried wood-flour composites confirms that removal of the adsorbed moisture from wood-flour results in a better cell morphology. However, it seems that some gaseous emissions released from wood-flour are soluble in plastic and thereby favorably contribute to the development of the cell morphology. This paper describes the expansion mechanisms of wood-flour composite foams resulting from the adsorbed moisture and dissolved gaseous emissions as well as resulting from the finely dispersed undissolved gas bubbles released from a chemical blowing agent. [source] Foaming of PS/wood fiber composites using moisture as a blowing agentPOLYMER ENGINEERING & SCIENCE, Issue 10 2000Ghaus Rizvi This paper presents an experimental study on foam processing of polystyrene (PS) and high-impact polystyrene HIPS/wood-fiber composites in extrusion using moisture as a blowing agent. Wood-fiber inherently contains moisture that can potentially be used as a blowing agent. Undried wood-fiber was processed together with PS and HIPS materials in extrusion and wood-fiber composite foams were produced. The cellular morphology and volume expansion ratios of the foamed composites were characterized. Because of the high stiffness of styrenic materials, moisture condensation during cooling after expansion at high temperature did not cause much contraction of the foamed composite and a high volume expansion ratio up to 20 was successfully obtained. The experimental results showed that the expansion ratio could be controlled by varying the processing temperature and the moisture content in the wood fiber. The effects of a small amount of a chemical blowing agent and mineral oil on the cell morphologies of plastic/wood-fiber composite foams were also investigated. [source] | ||||||||||