Value-adding to cellulosic ethanol: lignin polymers.

Effects of lysine-based diisocyanate (LDI) as a coupling agent on the properties of biocomposite from poly (lactic acid) (PLA), poly (butylene succinate) (PBS) and bamboo fiber (BF) were investigated. Tensile properties, water resistance, and interfacial adhesion of both PLA/BF and PBS/BF composites were improved by the addition of LDI, whereas thermal flow became somewhat difficult due to cross-linking between polymer matrix and BF. Crystallization temperature and enthalpy in both composites were increased and decreased with increasing LDI content, respectively. The heat of fusion in both composites was decreased by addition of LDI, whereas there was no significant change in melting temperature. Thermal degradation temperature of both composites was lower than those of pure polymer matrix, but the composites with LDI showed higher degradation temperature than those without LDI. Enzymatic biodegradability of PLA/BF and PBS/BF composites was investigated by Proteinase K and Lipase PS, respectively. Both composites could be quickly decomposed by enzyme and the addition of LDI delayed the degradation.

Biodegradable polymers/bamboo fiber biocomposite with bio-based coupling agent

Among the main contributors to the gross domestic product of all countries are their natural resources, whose improper utilization adds problems to the lack of proper data on their availability and structure/property correlations. If these data were made available, they would help in achieving objectives of value addition and employment generation. This paper describes the availability of some of the Brazilian lignocellulosic fibers, their market, extraction methods, reported morphology, properties and their present applications. Some perspectives for these fibers are also presented, considering their growing importance and their whole spectrum of promising opportunities and challenges for Brazil and other developing countries.

Studies on lignocellulosic fibers of Brazil. Part I: Source, production, morphology, properties and applications

Properties and chemical modifications of lignin: Towards lignin-based nanomaterials for biomedical applications

In this review, insight into the use of bio-based fibers as composite reinforcement has been addressed. Specifics on the varieties of natural fibers, and the resultant properties from their constituents and hierarchal structures are described. The methods used to enhance the interface of these fibers with a variety of polymer matrices are reviewed. In addition, the influence of textile operations on creating various fiber architectures with resulting reinforcing capabilities, along with the methods in which natural fiber reinforced composites can be processed, are addressed. Finally, discussion of the correlation between structure, processing, and final composite properties are provided.

Natural Fiber Reinforced Composites

Biobased composites from tannin–phenolic polymers reinforced with coir fibers

A new chemical modification of sugar cane bagasse fibers for phenolic thermoset composites is presented. It consists in creating quinones in the lignin portions of fiber and react them with furfuryl alcohol to create a coating around the fiber more compatible with the phenolic resins used to prepare polymeric matrix. Sodium periodate was used in suitable conditions to oxidize mainly phenolic syringyl and guaiacy units of the lignin polymer to create quinones, which were characterized by UV-visible diffuse reflectance spectroscopy by comparison with model compounds. The reactivity of furfuryl alcohol (FA) with fibers was greatly enhanced after they were oxidized: 13% weight percent gain compared to 2% without oxidation. Chemical analysis of unmodified and FA-modified fibers have shown an important degradation of hemicellulose and a slight one of cellulose which almost maintains its crystallinity. A 25% decrease of strength and length properties of the fibers after FA chemical treatment was measured by dynamic mechanical analysis. The lignin-like proportion of the fiber was greatly enchanced after the FA-treatment. This was confirmed by thermal analysis, DSC, and TGA experiments, on unmodified and FA-modified fibers. SEM analysis of the fibers and of phenolic composites with modified fibers have confirned the FA grafting and shown a better comptability at the interface between the chemically modified fibers and the phenolic matrix. Nevertheless, the chemical treatment of the fibers decreased the impact strength of the composite, which could be caused by the fiber damage suffered during the chemical modification and for the more intense adhesion at the interface, wich in some cases decrease somewhat the impact strength.

Phenolic Thermoset Matrix Reinforced with Sugar Cane Bagasse Fibers: Attempt to Develop a New Fiber Surface Chemical Modification Involving Formation of Quinones Followed by Reaction with Furfuryl Alcohol

Alkali and ionized air treated and untreated lignocellulosic fibers, such as sisal, jute and curaua, were used to reinforce phenolic and lignophenolic matrix materials. The results favor sisal fiber for its excellent performance as a reinforcing agent of phenolic and lignophenolic matrices, increasing the impact strength up to 35 fold in relation to that obtained with thermoset composites. The use of lignin as a partial substitute for phenol in closed cell lignophenolic foams reduces the thermal conductivity and allows classifying the lignophenolic foam as a thermal isolating structural foam.

Plastics and Composites from Lignophenols

Composites based on a thermoset phenolic matrix and jute fibers were prepared and characterized. The fibers were alternatively treated with ionized air or aqueous alkaline solution (mercerization) with the aim of introducing changes in the morphology, dispersive component of surface free energy, γSD (estimated by Inverse Gas Chromatography, IGC) and the acid/base character of their surfaces, shown by their ANs/DNs ratio (estimated by IGC), and their degree of crystallinity. The final objective was to investigate the influence of these modifications on the adhesion at the jute fiber/phenolic matrix interface in the composites. The untreated jute fiber showed 50% crystallinity, γSD=18 mJ m - 2 and ANs/DNs= 0.9 (amphoteric surface), tensile strength = 460 MPa and maximum elongation = 0.7%, while the respective composite had an impact strength of 72.6 J m - 1. The treatments positively modified the fibers and the adhesion at the interface was better in the composites reinforced with treated fibers than with untreated fibers. The best set of results was exhibited by the fiber treated with 10% NaOH [46% crystallinity, γSD = 26 J m - 2 (phenolic matrix γSD = 32 J m - 2), ANs/DNs = 1.8 (surface predominantly acidic, similar to phenolic matrix, ANs/DNs = 1.4), tensile strength approximately 900 MPa, maximum elongation = 2%, impact strength of respective composite approximately 95 J m - 1)]. The fibers treated for 5 h with ionized air exhibited favorable properties [(45% crystallinity, γSD = 27 J m - 2, ANs/DNs = 2.1 (acidic surface)] for further use as reinforcement of a phenolic matrix, but their partial degradation during the treatment decreased their tensile properties (395 MPa and 0.5% for tensile strength and maximum elongation, respectively) and their action as reinforcement (impact strength of the respective composite approximately 73 J m - 1).

https://www.scielo.br/pdf/po/v24n4/02.pdf

Ilce Aiko Tanaka Razera

Papers

Biobased composites from tannin–phenolic polymers reinforced with coir fibers

Phenolic Thermoset Matrix Reinforced with Sugar Cane Bagasse Fibers: Attempt to Develop a New Fiber Surface Chemical Modification Involving Formation of Quinones Followed by Reaction with Furfuryl Alcohol

Plastics and Composites from Lignophenols

Treatments of jute fibers aiming at improvement of fiber-phenolic matrix adhesion

Coconut fibers as reinforcement of lignophenolic matrices