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Issues of product safety are the most serious problems of an injection molded product due to their risk to human health. Such a safety problem can be the needle-shaped vestige at the gate zone of injection molded products, called a gate vestige. Only observations of the formation of gate vestiges can be found in the literature, but the processing parameters influencing their dimensions, especially their height have not been studied yet. Our goal was to study the effect of various injection molding processing parameters and gate constructions on gate vestige formation. [ABSTRACT FROM AUTHOR]

In this work, all-polypropylene composites (all-PP composites) were manufactured by injection moulding. Prior to injection moulding, pre-impregnated pellets were prepared by a three-step process (filament winding, compression moulding and pelletizing). A highly oriented polypropylene multifilament was used as the reinforcement material, and a random polypropylene copolymer (with ethylene) was used as the matrix material. Plaque specimens were injection moulded from the pellets with either a film gate or a fan gate. The compression moulded sheets and injection moulding plaques were characterised by shrinkage tests, static tensile tests, dynamic mechanical analysis and falling weight impact tests; the fibre distribution and fibre/matrix adhesion were analysed with light microscopy and scanning electron microscopy. The results showed that with increasing fibre content, both the yield stress and the perforation energy significantly increased. Of the two types of gates used, the fan gate caused the mechanical properties of the plaque specimens to become more homogeneous (i.e., the differences in behaviour parallel and perpendicular to the flow direction became negligible). [ABSTRACT FROM AUTHOR]

This paper focuses on the reinforcing of Poly(lactic acid) with chopped basalt fibres by using silane treated and untreated basalt fibres. Composite materials with 5-10-15-20-30-40 wt% basalt fibre contents were prepared from silane sized basalt fibres using extrusion, and injection moulding, while composites with 5-10-15 wt% basalt fibre contents were also prepared by using untreated basalt fibres as control. The properties of the injection moulded composites were extensively examined by using quasi-static (tensile, three-point bending) and dynamic mechanical tests (notched and unnotched Charpy impact tests), dynamic mechanical analysis (DMA), differential scanning calorimetry (DSC), heat deflection temperature (HDT) analysis, dimensional stability test, as well as melt flow index (MFI) analysis and scanning electron microscopic (SEM) observations. It was found that silane treated chopped basalt fibres are much more effective in reinforcing Poly(lactic acid) than natural fibres; although basalt fibres are not biodegradable but they are still considered as natural (can be found in nature in the form of volcanic rocks) and biologically inert. It is demonstrated in this paper that by using basalt fibre reinforcement, a renewable and natural resource based composite can be produced by injection moulding with excellent mechanical properties suitable even for engineering applications. Finally it was shown that by using adequate drying of the materials, composites with higher mechanical properties can be achieved compared to literature data. [ABSTRACT FROM AUTHOR]

Poly(N-isopropylacrylamide-co-N,N"-methylene-bisacrylamide) (P(NIPAAm-co-MBA)) hydrogels were prepared in water using redox initiator. The copolymer composition at high conversion (> 95%) was determined indirectly by HPLC (high performance liquid chromatography) analysis of the leaching water and directly by solid state 13C CP MAS NMR (cross polarization magic angle spinning nuclear magnetic resonance) spectroscopy of the dried gels, and was found to be close to that of the feed. The effect of cross-linker (MBA) content in the copolymer was investigated in the concentration range of 1.1-9.1 mol% (R:90-10; R = mol NIPAAm/mol MBA) on the rheological behaviour and mechanical strength of the hydrogels. Both storage and loss modulus decreased with decreasing cross-linker content as revealed by dynamic rheometry. Gels R70 and R90 with very low cross-linker content (1.2-1.5 mol% MBA) have a very loose network structure, which is significantly different from those with higher cross-linker content manifesting in higher difference in storage modulus. The temperature dependence of the damping factor served the most accurate determination of the volume phase transition temperature, which was not affected by the cross-link density in the investigated range of MBA concentration. Gel R10 with highest cross-linker content (9.1 mol% MBA) behaves anomalously due to heterogeneity and the hindered conformation of the side chains of PNIPAAm. [ABSTRACT FROM AUTHOR]

Poly(lactic acid) (PLA) and polypropylene (PP) were comparatively investigated as matrices for injection-moulded composites containing small (1–3 wt%) amounts of short sisal fibre. The morphology, thermal and dynamic mechanical properties, as well as degradation characteristics were investigated. The scanning electron microscopy (SEM) micrographs of the composites show more intimate contact and better interaction between the fibres and PLA, compared to PP. This improved interaction was confirmed by the Fourier-transform infrared (FTIR) spectroscopy results which showed the presence of hydrogen bonding interaction between PLA and the fibres. The thermal stability (as determined through thermogravimetric analysis [TGA]) of both polymers increased with increasing fibre content, with a more significant improvement in the case of PP. The differential scanning calorimetry (DSC) results showed a significant influence of the fibres on the cold crystallization and melting behaviour of PLA, even at the low fibre contents of 1–3%. The influence of the fibres on the melting characteristics of the PP was negligible, but it had a significant influence on the nonisothermal crystallization temperature range. Both the storage and loss moduli of the PLA decreased with increasing fibre content below the glass transition of PLA, but the influence on the loss modulus was more significant. The dynamic mechanical analysis (DMA) results clearly show cold crystallization of PLA around 110°C, and the presence of fibres gave rise to higher modulus values between the cold crystallization and melting of the PLA. The presence of fibres also had an influence on the dynamic mechanical properties of PP. This article further describes basic biodegradation observations for the investigated samples. [ABSTRACT FROM PUBLISHER]

This article focuses on the drying of native maize starch before compounding with poly(lactic acid) (PLA) and on the water absorption of injection-molded starch-filled PLA products. The mass loss of starch was examined while drying in a vented oven at various temperatures, and a proposal was made for complete drying. A temperature-dependent mathematical model was established to describe the moisture loss of native starch. The dried starch was mixed with PLA, compounded with a twin-screw extruder, and finally injection-molded into 80 × 80 mm area, 2-mm-thick flat specimens. These specimens were placed into distilled water to analyze the water uptake and the change in mechanical properties and deformation caused by water uptake for 1 month. Another mathematical model was established to describe the water absorption of the specimens. With the proper drying of starch and PLA, a 30 wt% starch content PLA product was injection-molded with significantly higher tensile strength compared with literature data. POLYM. ENG. SCI., 2011. © 2011 Society of Plastics Engineers [ABSTRACT FROM AUTHOR]

We report on the discovery of new members of nearby young moving groups, exploiting the full power of combining the Radial Velocity Experiment (RAVE) survey with several stellar age diagnostic methods and follow-up high-resolution optical spectroscopy. The results include the identification of one new and five likely members of the β Pictoris moving group, ranging from spectral types F9 to M4 with the majority being M dwarfs, one K7 likely member of the ε Cha group and two stars in the Tucana-Horologium association. Based on the positive identifications, we foreshadow a great potential of the RAVE data base in progressing towards a full census of young moving groups in the solar neighbourhood. [ABSTRACT FROM AUTHOR]

This paper focuses on the crystalline structure of injection moulding grade poly(lactic acid) (PLA) and the effect of crystalline structure on the processing. The research is induced by the significant differences in crystallinity of the pure PLA resin, and the injection moulded product, and thus the reprocessing of PLA products. 2 mm thick PLA sheets were injection moulded and re-crystallized in a conventional oven at 60-140°C, for 10-60 minutes to achieve various crystalline contents. The properties of these sheets were investigated by dynamic mechanical analysis (DMA), differential scanning calorimetry (DSC), and wide angle X-ray diffraction (WAXD). In a processing plant the rejected parts are recycled and reused as raw material for further cycles, accordingly the various crystalline content PLA products were reprocessed as a resin, to investigate the processing itself. When PLA products are reprocessed, due to the adherent feature of amorphous PLA processing difficulties may occur. This adherent effect of the amorphous PLA was investigated and characterized. [ABSTRACT FROM AUTHOR]

The article presents a study on the effects of glass bead content and diameter on the shrinkage and warpage behavior of injection-molded polyamide 6 (PA6). Three deformation factors have been defined to characterize shrinkage and warpage of injection-molded PA6. According to the study, the flow directional shrinkages can be described by the change in the bead content and diameter. It is noted that increase in bead content and in bead diameter induces a reduction in flow directional shrinkage and increases the deformation factor.