The performance of cotton–kapok fabric–polyester composites

Abstract Cotton–kapok fabric, at a ratio of 2:3, has been incorporated with unsaturated polyester resin in various fibre volume fractions. The fabric was also treated with 5% sodium hydroxide with the aim of improving fibre–matrix adhesion. A simple manual lay up technique was used in fabricating the composites. A hand operated hydraulic electrically heated press was used and the composites were cured at 100°C for 60 min and post cured overnight in the oven at 80°C. Mechanical properties such as tensile strength, tensile modulus, impact strength, and flexural properties of composites not subjected to weathering conditions and weathered composites have been evaluated. Composites with untreated fibres had higher fibre volume fractions than composites prepared using treated fibres. The tensile strength of composites with untreated fibres was higher than that of composites prepared using treated fibres but had, on average, higher tensile modulus than composites manufactured using untreated fibres. The impact strength decreased with increase in fibre volume fractions for both composites, with or without alkali treated fibres. Reductions in flexural strength and moduli were observed with weathered composites. The specific strength of the composites was comparable to that of other vegetable fibre reinforced resins

Changes on content, structure and surface distribution of lignin in jute fibers after laccase treatment

Effect of laccase treatment on the content, structure, and surface distribution of lignin in jute fibers were fundamentally investigated. Four percent lignin was removed from jute fibers via the laccase treatment. The residual lignin in the laccase-treated jute fibers showed increased molecular weights, which indicated polymerization between lignins on jute fibers. Meanwhile, the phenolic hydroxyl content in lignin decreased during the laccase oxidation accompanied by demethylation of methoxyl groups and generation of carbonyl groups. Due to the degradation and subsequent polymerization of lignin by laccase, the bulgy lignins on jute fiber surfaces were redistributed, which made the surface neat and glossy.This work was financially supported by the National Natural Science Foundations of China (51603087, 51673087), Program for Changjiang Scholars and Innovative Research Team in University (IRT_15R26), Fundamental Research Funds for the Central Universities (JUSRP51717A), Key R&D Program of Jiangsu Province (BE2016208), Portuguese Foundation for Science and Technology (UID/BIO/04469/2013 unit), and COMPETE 2020 (POCI-01-0145-FEDER006684).info:eu-repo/semantics/publishedVersio

Expression Profiling Reveals Novel Hypoxic Biomarkers in Peripheral Blood of Adult Mice Exposed to Chronic Hypoxia

Hypoxia induces a myriad of changes including an increase in hematocrit due to erythropoietin (EPO) mediated erythropoiesis. While hypoxia is of importance physiologically and clinically, lacunae exist in our knowledge of the systemic and temporal changes in gene expression occurring in blood during the exposure and recovery from hypoxia. To identify these changes expression profiling was conducted on blood obtained from cohorts of C57Bl-10 wild type mice that were maintained at normoxia (NX), exposed for two weeks to normobaric chronic hypoxia (CH) or two weeks of CH followed by two weeks of normoxic recovery (REC). Using stringent bioinformatic cut-offs (0% FDR, 2 fold change cut-off), 230 genes were identified and separated into four distinct temporal categories. Class I) contained 1 transcript up-regulated in both CH and REC; Class II) contained 202 transcripts up-regulated in CH but down-regulated after REC; Class III) contained 9 transcripts down-regulated both in CH and REC; Class IV) contained 18 transcripts down-regulated after CH exposure but up-regulated after REC. Profiling was independently validated and extended by analyzing expression levels of selected genes as novel biomarkers from our profile (e.g. spectrin alpha-1, ubiquitin domain family-1 and pyrroline-5-carboxylate reductase-1) by performing qPCR at 7 different time points during CH and REC. Our identification and characterization of these genes define transcriptome level changes occurring during chronic hypoxia and normoxic recovery as well as novel blood biomarkers that may be useful in monitoring a variety of physiological and pathological conditions associated with hypoxia

Thermal and mechanical properties of chitosan nanocomposites with cellulose modified in ionic liquids

In this paper, ionic liquid treatment was applied to produce nanometric cellulose particles of two polymorphic forms. A complex characterization of nanofillers including wide-angle X-ray scattering, Fourier transform infrared spectroscopy, and particle size determination was performed. The evaluated ionic liquid treatment was effective in terms of nanocrystalline cellulose production, leaving chemical and supermolecular structure of the materials intact. However, nanocrystalline cellulose II was found to be more prone to ionic liquid hydrolysis leading to formation larger amount of small particles. Each nanocrystalline cellulose was subsequently mixed with a solution of chitosan, so that composite films containing 1, 3, and 5% mass/mass of nanometric filler were obtained. Reference samples of chitosan and chitosan with micrometric celluloses were also solvent casted. Thermal, mechanical, and morphological properties of films were tested and correlated with properties of filler used. The results of both, tensile tests and thermogravimetric analysis showed a significant discrepancy between composites filled with nanocrystalline cellulose I and nanocrystalline cellulose II