Low‐density polyethylene/spherical silica (LDPE/SGS) nanocomposites, containing 1, 2, and 6 wt % neat and modified (having amine functional groups) silica nanoparticles, were prepared by melt mixing using a twin‐screw corotating extruder. To improve the dispersion degree of the nanoparticles, glicydyl methacrylate grafted ethylene/n‐octene copolymer (EOR‐g‐GMA) containing 0.6 wt % GMA was used as a compatibilizer. It was observed that mechanical properties such as tensile strength, Young's modulus, and impact strength increase and are mainly affected by the loading and size of silica nanoparticles as well as by the EOR‐g‐GMA. The addition of modified silica and EOR‐g‐GMA resulted in a further enhancement of mechanical properties due to the improved interfacial adhesion. Storage and loss modulus values of prepared nanocomposites measured by dynamic‐mechanical thermal analysis were sensitive to the microstructure of the nanocomposites. Higher storage and loss modulus are evidence that the nanocomposites became stiffer. By adding the modified silica and EOR‐g‐GMA further increase in storage and loss modulus were observed due to the better dispersion of silica nanoparticles and increased compatibility between silica and the LDPE matrix. Both permitted a much more efficient transfer of stress from the polymer matrix to the silica nanoparticles. The improved barrier properties of all nanocomposites can also be mentioned as a positive effect. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012

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The effect of plasticizer (polydimethylsiloxanol) and neat (SiO2) or modified (having amine functional groups) silica (A-SiO2) on morphology, thermal, mechanical, and rheological properties of PLA/TPS blends compatibilized by maleated PLA (MPLA) was investigated. Toughened PLA/MPLA/TPS (60/10/30) blend containing 3 wt.% of plasticizer and various contents (1, 3, or 5 wt.%) of silica were prepared in a corotating twin-screw extruder. From SEM, it is clear that plasticized PLA/MPLA/TPS blend continuous porous structure is highly related to the silica content and its functionality. The results indicate that polydimethylsiloxanol enhances ductility and the initial thermal stability of the plasticized blend. DSC and DMTA analyses show that nucleation ability and reinforcing effect of A-SiO2on plasticized blend crystallization are much better than those of SiO2. Silica practically had no effect on the thermo-oxidative degradation. However, the composites with A-SiO2had better thermal stability than those with SiO2. Moreover, silica significantly improved the elongation at break.

Silica having amine functional groups (A-SiO2) obtained by the sol-gel process was used to improve compatibility of polyamide 11 and poly(phenylene oxide) (PA11/PPO 80/20) blend via reactive extrusion in a co-rotating twin screw extruder. Amine functional groups of A-SiO2 can react with the carboxyl groups of PA11 to form graft copolymer with PA11 which can efficiently control the phase morphology of the blend. Silica, thanks to the reinforcing effect, significantly increased stiffness of PA11/PPO blend. On the other hand, it greatly improved impact strength and reduced the crystallinity without affecting the crystallization temperature of PA11due to excellent compatibilizing effect. SEM results showed that despite the lower content of PPO, it formed a continuous phase and PA11 - a dispersed. The addition of A-SiO2 changed the morphology from the droplet-matrix to co-continuous with interpenetrating phases. The greatest size-reduction of both phases, reflecting the highest impact toughness, was observed for the content of 3 wt % A-SiO2. With a higher silica loading, phase inversion was observed with the reappearance of the droplet structure, resulting in a slight decrease in impact strength and significant in elongation at break. TGA showed that the composites exhibited better thermal properties as evidenced by the higher initial degradation temperature (Tonset) and the maximum weight loss rate temperature (Tmax).