Pineapple leaf fiber reinforced thermoplastic composites: Effects of fiber length and fiber content on their characteristics

Pineapple leaf fiber (PALF) was used as a reinforcement in polyolefins. Polypropylene (PP) and low‐density polyethylene (LDPE) composites with different fiber lengths (long and short fibers) and fiber contents (0–25%) were prepared and characterized. The results showed that the tensile strength of the composites increased when the PALF contents were increased. It was observed that the composites containing long fiber PALF were stronger than the short fiber composites as determined by greater tensile strength. An SEM study on the tensile fractured surface confirmed the homogeneous dispersion of the long fibers in the polymer matrixes better than dispersion of the short fibers. The unidirectional arrangement of the long fibers provided good interfacial bonding between the PALF and polymer which was a crucial factor in achieving high strength composites. Reduction in crystallinity of the composites, as evident from XRD and DSC studies suggested that the reinforcing effect of PALF played an important role in enhancing their mechanical strength. From the rule of mixtures, the stress efficiency factors of the composite strength could be calculated. The stress efficiency factors of LDPE were greater than those of PP. This would possibly explain why the high modulus fiber (PALF) had better load transfers to the ductile matrix of LDPE than the brittle matrix of PP. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Properties of sericin–glucomannan composite films

Sericin is a natural silk protein which is removed from silk in a process called degumming. Thus, finding a use for the extracted sericin as a biopolymer film will create added value which will benefit both the economy and society. It was found that extracted sericin could not form stand-alone films. Therefore, glucomannan was incorporated with or without glycerol to form a flexible film. Sericin and glucomannan ratio (S:G) affected film properties. Increasing sericin content (S:G = 2:1) slightly reduced film water vapour permeability (WVP) without adding glycerol (Gly). This indicated that sericin provided film flexibility without increasing film WVP. As expected, increasing glycerol content increased film WVP as well as decreased tensile strength and elastic modulus but increased dramatically % elongation. It is interesting that adding beeswax to form a composite film did not improve film water vapour barrier. Thus, sericin-based film properties are dependent on components used to form film and can tailor to form the desired film flexibility and minimise permeability of films for application.     

Influence of Eri silk fibre on the physical characteristics and dyeing properties of Eri silk/cotton blended yarn

Different blending ratios of Eri silk and cotton fibres were prepared. The optimum bleaching condition chosen for the blends containing 0–25% silk content was the oxidative bleaching method, whereas the blends at 50–100% should be bleached using the two‐stage bleaching method (oxidative bleaching followed by reductive bleaching). These conditions did affect the force–displacement characteristics of the fibres with no yield point. X‐Ray diffraction results showed that the percentage of crystallinity of the cotton yarn tended to increase after bleaching, whereas the percentage of crystallinity of the Eri yarn decreased marginally. Dyeing properties of the blended yarns were investigated using warm‐dyeing reactive dyes. Percentage exhaustion and the colour yield of the blends tended to decrease with the increasing silk content. Shade variation was observed on the yarns at different blend ratios. This was expected to be caused by the different physical nature of Eri silk and cotton fibres. Consequently, the dye uptake and visual shade of each dye on the two fibres were different.     

Polyethylene green composites reinforced with cellulose fibers (coir and palm fibers): effect of fiber surface treatment and fiber content

Coir and palm fibers from agricultural waste were investigated as reinforcement for low density polyethylene (LDPE). The effect of fiber preparation with alkaline treatment and with/without bleaching on fiber physical properties was also an objective of this study. The chemical composition and FTIR (Fourier transform infrared spectroscopy) results confirmed that palm fibers had less impurity than coir fibers. This could be the reason for a greater fiber-matrix interfacial interaction of the palm fibers as compared to that of coir fibers, which was in good agreement with the estimation of surface free energy of the dispersion component. Moreover, fiber bleaching improved the single fiber pullout stress. Composites with both alkaline treated and bleached fibers, at different fiber contents (5, 10, 15, and 20 wt.%), were manufactured using a compression molding machine. Addition of both fibers in the LDPE matrix resulted in composites with a higher Young’s modulus compared to that of homopolymer. The Young’s modulus of the composites increased with the effect of either fiber content or fiber bleaching. Differential scanning calorimetry (DSC) showed that composites reinforced with both types of fibers had a single melting temperature peak, indicating the existence of only one type of crystalline species. Moreover, there were no significant differences in the melting temperatures for the fiber reinforced composites and the homo-LDPE. The heat of fusion decreased in the case of fiber reinforced composites.