A novel approach to PLA toughening is proposed in this study. Poly(lactic acid) (PLA) is toughened using poly(ethylene‐n‐butylene‐acrylate‐co‐glycydyl methacrylate) (EBA‐GMA) as a reactive compatibilizer with the aid of an epoxy‐based chain extender. It is found that the toughening effect of EBA‐GMA in the binary blend investigated is strongly influenced by blending temperature. Blending at high temperatures which are non‐typical for PLA processing (over 250 °C) allows toughness to be increased by an order of magnitude when compared to the toughness of blends prepared at low temperatures (below 200 °C). This effect is attributed to a combination of factors, namely an increasing rate of reactive bonding between PLA and EBA‐GMA at elevated temperatures and enhanced interfacial adhesion between PLA and EBA‐GMA phases. DSC studies show that PLA/EBA‐GMA bonding on the interface acts as an efficient nucleator for PLA. The nucleation ability of the PLA/EBA‐GMA interface strongly depends on blend processing temperature and gradually increases with increasing blending temperature. The PLA/EBA‐GMA interface shows its highest nucleation ability at 250 °C.
We aim to show the existence of agglomeration by measuring and modelling secondary nucleation and crystal growth rates of calcium sulphate hemihydrate, CaSO4-0.5 H2O, in concentrated phosphoric acid solutions. Using a batch crystallizer we measured the evolution of the population density as a function of supersaturation, H2SO4 excess and stirring rates. All experiments were carried out at 90 °C in solutions at 40 wt.% of P2O5, simulating the usual conditions for crystallizing hemihydrate in the industrial processes of phosphoric acid production. Nucleation and growth rates were calculated from the population number densities, using the moments analysis method. A model is presented for describing the crystallization process of hemihydrate. It is shown that secondary nucleation and growth rates are quadratic functions of supersaturation. H2SO4 concentrations affect supersaturation but at the same supersaturation the growth rates are not significantly different. Nucleation is independent of the stirring rate, whereas growth rates are slightly affected for stirring rates up to 500 rpm. Taking agglomeration into account, the moments method fits very well the experimental data. 相似文献
Niobium pentoxide (T form, orthorhombic system) was utilized to promote devitrification in Li2O · Al2O3· 6SiO2 glasses. Two or more mole percentage of this nucleating dopant enhanced crystallization in these glasses. Glasses containing 4.0 and 8.0 mol% T-Nb2O5 exhibited a high tendency to form dispersed TT-Nb2O5 (monoclinic system) precipitates during the glass quenching process. The crystallization process in glasses containing 2.0 or 4.0 mol% T-Nb2O5 occurred as microphase separation, followed by the formation of dispersed TT-Nb2O5 crystalline precipitates (760°C), followed by β-quartz solid-solution ( ss ) formation (850° to 900°C) heterogeneously nucleated from the precipitates. β-quartz( ss ) transformed to β-spodumene( ss ), along with a polymorphic transition from the TT-Nb2O5 to M-Nb2O5 (tetragonal system) crystalline phase. 相似文献
The influence of thiourea on the nucleation of copper from a 0.30 M CuSO4-1 M H2SO4 solution on polycrystalline platinum electrodes covered by a copper adlayer was investigated. In the case of diffusion controlled nucleation and growth the conditioning potential, that is, the potential of the electrode prior to the application of a large negative potential step, has a strong influence on the nucleation transients. This can result in either a promotion or an inhibition of the nucleation (which is characterized by a change in the nucleation rate constant and/or the site density) depending on the applied potential and the concentration of thiourea. In the region of mixed kinetics and for a fixed value of the conditioning potential (0.175 V vs Cu2+|Cu, that is, in the region of strongest inhibition), a new and rather unexpected effect was observed. Thus, after an induction period, which is proportional to the concentration of thiourea, the current increases sharply to a much higher value, but after reaching a maximum drops again to its original value. At present there is no ready explanation for this phenomenon, which has been called 'nucleation outbursts', but it deserves more investigation because the linearity between the induction time and the concentration of thiourea might have practical applications. 相似文献