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New composite materials with a high percentage of their composition based on renewable resources, matrix and reinforcement, were prepared. The excellent compatibility of the main phases lead to an unusual outstanding composite behavior as follows: higher modulus and strength, but also higher deformability and fracture resistance than the neat polymer. A bio‐based polyol was obtained by chemical modification of tung oil to be used in the production of polyurethane composites reinforced with pine wood flour (WF). The mechanical behavior as a function of wood flour content was evaluated through tensile and impact tests. Increasing the filler content induced an increase in tensile modulus and strength as well as in impact strength. Composites containing 10 and 15 wt% of wood flour presented higher tensile ultimate strain than that of the unfilled polyurethane. These results were explained by a strong interfacial adhesion (physical and chemical bonding), which was also supported by SEM micrography and strength modeling. POLYM. ENG. SCI., 2009. © 2009 Society of Plastics Engineers

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A model portraying the carrier dynamics for an inhomogeneous array of quantum dots (QDs) interacting with a number of photon modes is presented. The model treats an ensemble of QDs with one confined level coupled to a wetting layer or quantum well level and explicitly considers only the electrons. The model is derived by numerically solving a set of rate equations that includes the inhomogeneity of the dot size, multimode photon modes and temperature dependence. Explicitly the inhomogeneous size distribution is included within a inhomogeneous broadening parameter and the temperature dependence within the homogeneous broadening parameter as well as carrier thermal escape. This is similar to the well-known Sugawara model 1 but in the Sugawara model the carriers are assumed to occupy the inhomogeneous quantum dots equally at all temperatures. Experimental and theoretical work in ref.(2) and (3) believes this is true only for a low temperature regime. Above the temperature where a global minima exists, Fermi-Dirac statistics have been used. This results in different gain and lasing behaviour for higher temperatures from those calculated using the Sugawara model.

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