Correlation Between Thermal Diffusivity and Dynamic Mechanical Properties of Soft Magnetic Particle Filled Thermoplastic Composites

Measurements of thermal diffusivity α by laser flash method (LFA) and storage modulus E′ by dynamic mechanical analysis (DMA) have been performed on polypropylene-iron silicon (PP/FeSi6.8) composites with filler particle content from 10 vol.-% to 60 vol.-% at temperatures from 300 K to 415 K and 200 K to 425 K, respectively. The thermal diffusivity induces a decline with increased temperature for all examined materials. The drop in thermal diffusivity versus temperature corresponds with the filler fraction. Observing the behavior of the storage modulus of FeSi6.8 filled PP one can show that the larger the filler fraction of particles in the polymer the stronger is the decrease of storage modulus versus temperature. The inflection point of the dynamic mechanical measurement curve at about 360 K corresponds very well with starting increase of thermal conductivity. The achieved results can be explained by the relation of the velocity v of phonons and its free path length l to the thermal diffusivity α according to α = (1/3)vl (Einstein approximation). Moreover, v is correlated to the bulk modulus K (and specific density ρ) via v ≈ (K/ρ)0.5.

Application of Liquefied Wood to a New Resin System—Synthesis and Properties of Liquefied Wood/Epoxy Resins

Summary A new resin system was developed by reacting liquefied wood with various epoxy compounds. Examination of the optimum conditions for the synthesis of the resins, and the behavior of liquefied wood in the cured resins were undertaken. Generally, the compatibility and film forming performance of liquefied wood/epoxy resins became better as the wood content increased. The presence of only one broad dispersion peak, due to the glass transition, was observed during dynamic mechanical measurement of resin films suggesting that the different components of the resin were compatible. The glass transition temperature of the cured resins could be modified by changing the kinds of epoxy compounds and the wood contents of liquefied wood. The presence of rubber elasticity at higher temperatures suggests that the resin systems consisted of cross-linking polymer networks.