Thermal Treatment of Melt-Spun Fibers Based on High Density PolyEthylene and Lignin

Abstract

Abstract:The purpose of this study was the synthesis of novel low-cost carbon fibers along with the investigation of the optimal parameters of temperature and time for the stabilization of hybrid high-density polyethylene (HDPE) and lignin melt-spun fibers. These fibers were manufactured by physical compounding of HDPE and chemically-modified softwood kraft lignin (SKL) in order to produce green fiber precursors for carbon fiber synthesis. Stabilization tests were performed with respect to thermal treatment (physical method) and sulfonation treatment (chemical method). The results revealed that only chemical methods induce the desired thermal process-ability to the composite fibers in order to manufacture carbon fibers by using a simple method. This investigation shed light on the stabilization techniques of polymeric fibers in the absence of any cyclic groups in terms of environmentally-friendly mass production of carbon fibers using low-cost and green raw materials. This study facilitates incorporation of softwood lignin in homegrown polymeric fibers by a low-cost production process via melt-spinning of composite fibers, which were successfully stabilized using a facile chemical method and carbonized. Additionally, a comprehensive investigation of the thermal behavior of the samples was accomplished, by examining several ways and aspects of fiber thermal treating. The properties of all studied fibers are presented, compared, and discussed.

Synthesis and Characterization of a Core-Shell Copolymer with Different Glass Transition Temperatures

“…The morphology and composition of the produced materials were estimated with an ultra-high resolution scanning electron microscope (UHR-SEM) using NOVA NANOSEM 230 (FEI Company) coupled with a Hitachi electron microscope TM3030 and an energy dispersive x-ray spectrophotometer (EDS) (QUANTAX 70) [33]. In addition, the morphology of the core-shell copolymers was also characterized by TEM (model FEI CM20), operated at an accelerating voltage of 200 kV [34][35][36].…”

Introduction of a Methodology to Enhance the Stabilization Process of PAN Fibers by Modeling and Advanced Characterization

“…This can be better achieved by modifications of the stabilization process [4][5][6][7][8][9][10], since carbonization is a straightforward process that cannot be essentially altered and that investigation on novel CF precursors is time a consuming procedure. PAN-based CFs are more efficiently manufactured (due to their high carbon yield) and demonstrate a structure with less defects and voids, affording CF with high tensile strength in comparison to CFs derived from pitch, Rayon, or renewable precursors [1,[10][11][12][13][14][15]. Given that PAN-based CFs represent about 80-90 % of the world production, there is a strong incentive for improving the process design, so that it might be further optimized [9,14,16].…”

“…PAN-based CFs are more efficiently manufactured (due to their high carbon yield) and demonstrate a structure with less defects and voids, affording CF with high tensile strength in comparison to CFs derived from pitch, Rayon, or renewable precursors [1,[10][11][12][13][14][15]. Given that PAN-based CFs represent about 80-90 % of the world production, there is a strong incentive for improving the process design, so that it might be further optimized [9,14,16].…”

“…Stabilization is considered as the most crucial step; obtaining a proper structure is critical for achieving high performance CFs. This oxidation step, leads to an infusible and inflammable ladder polymer structure, suitable for carbonization [11,14,[17][18][19]. Regarding the thermal treatment, processability of PAN fibers is enhanced at temperatures exceeding glass transition temperature (Tg), commonly above 170 o C [20].…”

“…Generally, the main chemical reactions that occur during stabilization are dehydrogenation, cyclization and oxidation; their initiation depends on the treatment temperature, which also determines the relative effect and the relative rate of each reaction at the specific treatment stage [7,11,13,14,23,28,31,36]. Dehydrogenation reactions are considered to precede cyclization, while the oxidation takes place in the whole temperature region of stabilization.…”