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There are principally two mechanisms to improve the impact resistance of polymer-based composites, intrinsic toughening and extrinsic toughening. But the interplay between them is far from being well understood. Here, glass fiber was incorporated into polypropylene to promote extrinsic toughening mechanism, while addition of elastomer and annealing were adopted for intrinsic toughening. In this way, the interaction among glass fiber, elastomer and annealing could be discussed based on various characterizations, and their combined effect on mechanical properties of the composites could be determined. The results show that the intrinsic toughening mechanism of elastomer will be suppressed by glass fiber irrespective of the support of annealing, though annealing could work synergistically with glass fiber to toughen polypropylene. The possible structure-property relations are discussed. This work will provide deeper insight into the toughening behavior of polymer composites and practical guidance for the design of composites with excellent stiffness-toughness balance. [ABSTRACT FROM AUTHOR]

Abstract: β-Modification and annealing were adopted to improve the impact strength of long glass fiber reinforced (LFPP) composites. It was found that either β-modification or annealing is an efficient way to toughen LFPP composites, and largely enhanced impact toughness can be achieved via simultaneously using β-modification and annealing, particularly for the toughness at low temperatures (−40°C to −20°C). Meanwhile, the tensile strength and Young’s modulus of the composites could be maintained. Various characterizations were used to understand the microstructure changes and toughening mechanism after β-modification and annealing. The results show that the higher extent of the matrix plastic deformation could be the main reason for the enhanced toughness as induced by β-modification and annealing. The possible structural origins for the higher extent of matrix plastic deformation are also discussed. [Copyright &y& Elsevier]

Abstract: In this study, by directly melt-blending with 10wt% poly(lactic acid) (PLA) and 1.5wt% multiwalled carbon nanotubes (CNTs), yield strength of a biodegradable poly(propylene carbonate) (PPC) was increased more than one order of magnitude, and its Young’s modulus was enhanced by 8 times. Meanwhile, the high elongation at break of PPC was maintained. This overall property reinforcement could not be observed by adding either PLA or CNTs separately. At room temperature, the obtained mechanical properties of the reinforced PPC are comparable to or even better than those of some traditional petroleum-based polymers such as low density polyethylene, high density polyethylene and polypropylene (PP). Together with good biodegradability and excellent conductivity, the PPC/PLA/CNT composites prepared in this work exhibit a potential to be used as a sustainable alternative to petroleum-based polymers such as PP around room temperature. [Copyright &y& Elsevier]

Damping materials are used to control mechanical vibrations, and piezoelectric damping composite is a very promising material due to its unique mechanism. In this study, a potential piezoelectric damping composite was developed by simply melt mixing poly(vinylidene fluoride) (PVDF) with small amounts of organic modified montmorillonite (OMMT) and multi-walled carbon nanotubes (MWCNTs). The piezoelectric, mechanical and electrical properties were investigated using a dynamic mechanical analyser, direct current electrical resistivity measurements, X-ray diffraction, Fourier transform infrared spectroscopy and the direct quasi-static d33 piezoelectric coefficient method. It was found that the damping property of PVDF can be greatly improved by adding both MWCNTs and OMMT, and the composite containing 1.9 wt% of MWCNTs and 3 wt% of OMMT showed the best damping property. A model and an approximate calculation were applied to explain the improved damping property. Moreover, similar mechanical properties of PVDF composites were observed in the tensile testing and dynamic mechanical analyser measurements. Copyright © 2012 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

Abstract: Long fiber reinforcement is well known to offer thermoplastic materials with high performances. But little work has been done to systematically investigate the effect of shear on the structures and properties of long glass fiber reinforced thermoplastics. The purpose of this work is to investigate the effect of shear on fiber orientation, fiber breakage and matrix molecular orientation in long glass fiber reinforced polypropylene composites, and to construct the structure–property relations. A so-called dynamic packing injection molding (DPIM) technique, which imposed oscillatory shear (10s−1) on the gradually cooled melt during the packing solidification stage, was used to prepare the dynamic samples, and optical microscope (OM), scanning electron microscope (SEM), micro-Fourier transform infrared spectroscopy (FTIR) and differential scanning calorimetry (DSC) were used to characterize the samples. The results show that despite the well-published enhanced fiber and matrix orientation, shear will cause a remarkable fiber breakage. Combined effect of fiber breakage and orientation on the mechanical properties of the composites was qualitatively investigated and tensile properties of the dynamic samples, the conventional injection molded samples and the short glass fiber reinforced samples were compared. It is demonstrated that shear will induce more severe fiber breakage in long glass fiber reinforced polypropylene than in short glass fiber reinforced polypropylene, and that compromising the decreased strength caused by the severe fiber breakage is very difficult. [Copyright &y& Elsevier]

Highlights: [•] Biodegradable PPC/PMMA composites were prepared via a supercritical fluid route. [•] PMMA was dispersed on a nanometer scale (50–200nm) in the PPC substrate. [•] The yield strength of PPC sharply increased 4 times by incorporating 5wt% PMMA. [•] This study introduced an effective modification method of biodegradable PPC. [ABSTRACT FROM AUTHOR]