Natural fibres are likely to replace conventional mechanical reinforcements in composite materials. Among these fibres, pineapple leaves have been the subject of several studies, unlike the other parts of this plant, namely the stems and roots, which nevertheless represent a potential to be exploited, hence our interest in the subject. In this work, the aim is to characterize physically, mechanically and chemically the fibres from pineapple leaves, stems and roots for possible use in composite materials. After extraction of the various fibres by beaten, scraping and retting, physical tests (water absorption and density test) revealed that the water absorption rate and density increase from the roots to the leaves. Then, mechanical tests through mechanical strength and Youngʼs modulus allowed us to observe that fibres from roots perform better than those from leaves and stems. Finally, chemical tests allowed us to have the composition of each fibre after extraction by water retting (cellulose, Hemicellulose, Lignin, Pectin and ashes).
This review focuses on the previous and recent results as well as related literatures regarding the anti-HIV mechanism of sulfated alkyl poly- and oligosaccharides. .To clarify the anti-HIV mechanism of sulfated polysaccharides, curdlan sulfate was mainly used because of having potent anti-HIV activity and low cytotoxicity. Curdlan sulfate was prepared by sulfation of a natural occurring polysaccharide curdlan bearing linear (1→3)-β-D-glucopyranosidic structure. Nuclear magnetic resonance (NMR) analysis of the mixture of curdlan sulfate and an oligopeptide from the C-terminus of HIV envelope (surface) glycoprotein gp120 (HIV gp120) suggested that the anti-HIV activity of curdlan sulfate depended on electrostatic interactions between negatively charged sulfate groups in sulfated polysaccharides and positively charged amino acids in HIV gp120. The mechanism was assumed to be similar to the electrostatic interaction between a natural blood anticoagulant sulfated polysaccharide heparin and a protease inhibitor antithrombin III. In addition, the anti-HIV mechanism of curdlan sulfate was quantitatively investigated using surface plasmon resonance (SPR) and dynamic light scattering (DLS) measured with oligopeptides from three regions in HIV gp120, V3 loop, C-terminus, and CD4 binding domain. These studies revealed the interaction between oligopeptides of the V3 loop and C-terminus bearing positively charged amino acid accumulated regions in each sequence. These results indicated that the anti-HIV activity of sulfated polysaccharides involves electrostatic interactions. It was reported that a long-chain alkyl group in sulfated alkyl oligosaccharides plays a key role in the enhancement of anti-HIV activity. The interaction between sulfated alkyl poly- and oligosaccharides and liposomes as a model of HIV was also discussed by SPR and DLS measurements, suggesting that the long-chain alkyl group penetrated into the lipid bilayer of HIV, and then sulfated poly- and oligosaccharide portions electrostatically interacted with HIV gp120 to produce potent anti-HIV activity.
Knot-pull strength is as important as tensile strength, but the mechanism by which the fiber in a knot breaks has not been sufficiently elucidated. In the present study, the effects of the draw ratio and a melt-kneaded additive on the knot-pull strength of polypropylene monofilament, that is, a thick single fiber, were discussed by comparing the tensile and loop strengths of the fiber. The knot deformation behavior during a knot-pull test was also investigated. In contrast to the increase in tensile strength at a high draw ratio, the knot-pull strength was hardly affected by the additive, and the loop strength was reduced by the additive. During a knot-pull test on a high-draw-ratio fiber, the knot thickness continued to decrease to breakage, even after the knot length stopped decreasing. This behavior indicates that the highly drawn fiber breaks at the buckled part in the knot owing to the lateral compressional forces.
Hydrophobicity of polyester is the main problem being faced in the processing of polyester from fibre to yarn formation stages. Manufacturing of polyester with improved moisture properties have been tried but the static problem of polyester is not answered by the research. Alkaline hydrolysis is a more versatile process for polyester with commercial name as Weight reduction process will not only impart the silk like feeling but also enhances the moisture management properties. On the other hand, Jute is being a natural fibre, will be undergoing ʻwoollanisationʼeffect following treatment with Caustic. In this research, a passionate attempt is made to treat the polyester /jute union fabrics with an aim to improve the low-stress mechanical properties. Two groups of union fabrics are considered for the study and are hydrolyzed in alkali medium with identical conditions. The products were characterized for KES-F data and results were analysed statistically.