Thermal properties of composite

The thermal properties of composite boards were the subject of a recent report by Place and Maloney (58). Thermal conductivity tests were made on three-layer boards with surfaces of white pine wood flakes and cores of either Douglas-fir or grand fir bark. Density was varied at 34, 42, and 52 pounds per cubic foot. The composite boards containing bark proved to be better insulators than wood particleboard of comparable density. Douglas-fir bark cores had lower thermal conductivity than did grand fir. 

M. Ragoubi, B. George, S. Molina, D. Bienaime, A. Merlin, J.-M. Hiver, and A. Dahoun, Effect of corona discharge treatment on mechanical and thermal properties of composites based on miscanthus fibres and polylactic acid or polypropylene matrix. Compos. A 43, 675-685 (2012). 

Zhou and co-workers [27] studied the effects of surface treatment on the mechanical and thermal properties of composites comprising calcium carbonate particles with varying proportions of PEEK. Tensile impact and flexural testing were carried out and the effect of particle size, loading and surface treatment on deformation and crystallinity was investigated. 

Kuan, H.C., C. Ma, K. Chen et al. 2004. Preparation, electrical, mechanical and thermal properties of composite bipolar plate for a fuel cell. Journal of Power Sources 134 7-17. 

Carbon nanotubes (CNTs) are highly desirable materials possessing unique structural, mechanical, thermal, and electrical properties [25-30], Electrospun nanotube-polymer composite nanofibers are very attractive materials for a wide range of applications. This is due to the fact that the use of the electrospinning technique to incorporate CNTs in polymer nanofibers induces ahgnment of nanotubes within the nanofiber structure, which could greatly enhance the mechanical, electrical and thermal properties of composite fibers. " ... 

When the same approach is used to simulate thermal conductivity, quantum theory might be needed again to predict the resulting thermal properties of composite structures. On the other hand chirality, diameter, and the thickness of, for example, multi-walled carbon nanotubes, as well as morphology (both non-aligned and random - whiskers or straight and curved nanotubes), may play an important role in how to approach the effective determination of properties. Finally, the conductance at the metal catalyst-nanotube junction in the catalyst layers may be different... 

The presence of STEX straw fibers in both matrices (iPP and iPPMA) does not produce a worsening of thermal properties of composites T, and T).)-... 

Orts et al. [17] investigated composites of wheat or potato starch blended with pectin and reinforced with cellulose nanofibrils extracted from cotton, softwood, or bacterial cellulose. Mechanical and thermal properties of composites produced by casting and extrusion (extruded under a low and high shear mode) were evaluated. The addition of cellulose microfibrils to starch had a significant effect on mechanical properties at low concentrations. For example. Young s modulus of wheat starch nanocomposites reinforced with cotton nanofibrils increased by five times with the addition of only 2.1 wt% of nanofibrils (see Table 11.1). 

In this study, a novel proach is plied to prepare polymer composites reinforced by both nanoparticles and long fibers. Carbon nanofibers were pre-boimd onto glass fiber mats, and then unsaturated polyester conposites were synthesized through vacuum assisted resin transfer molding. These composites were compared with those synthesized by pre-mixing carbon nanofibers into the polymer resin. Mechanical and thermal properties of composites were measured. Flexural strength and modulus of composites were improved with the incorporation of nanoparticles. It was also found that carbon nanofibers increased the glass transition temperature and reduced the thermal expansion coefficients of imsaturated polyester resin. 

Flame retardancy tests were performed following the procedure of Underwriter s Laboratory Bulletin 94 entitled Tests for Flammability of Plastic Materials, UL94. According to this procedure, materials may be classified as HB, VO, VI, V2, VA and/or VB on the basis of the test results obtained for five samples. In this study, UL test was done at 0.8 mm thickness for all samples. Heat deflection Temperature (HDT, ISO 75/Be flat, 1.8 Mpa load) and Vicat softening temperature (Vicat, ISO 306, Vicat B, heating rate 120 °C/min load of 50 N) were used to determine thermal properties of compositions. Standard impact bars were used to measure these properties. Duplicate measurements were done and average of two samples were reported. 

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