LIGNOCELLULOSE NANOFIBERS/POLYLACTIC ACID COMPOSITE WITH ENHANCED DISPERSION AND COMPATIBILITY BY A WET-SHEAR PRETREATMENT
ID：22
Submission ID：31 View Protection：PRIVATE
Updated Time：2021-10-29 10:42:12 Hits：190
Oral Presentation
Abstract
Cellulose nanofibers (CNFs), which hold excellent mechanical, thermal, and chemical properties, have great potential as sustainable reinforcement fillers. However, the structure of cellulose nanofibers with a large number of hydroxyl groups on the surface with fibers tightly bound together by hydrogen bonding, causes strong polarity and hydrophilicity. It is one of the challenges to prepare cellulose nanofibers reinforced polymer composites by extrusion because of its strong hydrophilicity, easy to dry and difficult to disperse evenly in hydrophobic polymer matrix; Meanwhile, biodegradable polylactic acid (PLA) has been widely used in a variety of packaging materials because of its high mechanical strength, transparency and biocompatibility, but the crystallization of PLA is slow and the temperature of thermal deformation is low, which restricts its further application. To overcome the aggregation of cellulose nanofibers and improve the mechanical and thermal properties of PLA, in this work, a green wet-shear pretreatment process combined with simple silane modification was used to effectively disperse the oven dried lignocellulose nanofibers into polylactic acid matrix, and then the silane-modified lignocellulose nanofiber/ polylactic acid (SLCNF/PLA) composites were prepared by extrusion. SEM and polarized optical microscopy in molten state showed that wet-shear pretreatment combined with silane modification effectively promoted the dispersion of lignocellulose nanofibers, formed crosslinked network structure in the matrix and further improved the interfacial compatibility, so the tensile strength and elongation at break of the composites were improved. In particular, the tensile strength and elongation at break of the composites increased by 12.6% and 32.4% respectively with 1% SLCNF. Non isothermal crystallization and isothermal crystallization tests showed that SLCNF as heterogeneous nucleating agent promoted the crystallization of PLA, and the crystallinity of the composite increased by up to 260.2%. After isothermal crystallization at 110℃ for 60 min, the crystallinity of PLA composite increases from 7.15% to 31% -37%, and the crystallization rate increased observed by POM. Due to the improvement of dispersion and compatibility of SLCNF, the storage modulus and hot deformation temperature of PLA were improved, which further broadened the application field of PLA. This work provides an effective way for low-cost drying and effective dispersion of cellulose nanofibers for reinforcing polymer matrix composites.
Keywords
Wet-shear pretreatment, lignocellulose nanofiber, polylactic acid, dispersion, mechanical and thermal properties
Submission Author
Hongkun Wang
Technical Institute of Physics and Chemistry, Chinese Academy of Sciences
Min Wu
Technical Institute of Physics and Chemistry, Chinese Academy of Sciences
Yong Huang
Technical Institute of Physics and Chemistry of the Chinese Academy of Sciences
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