Influence of pretreatment on mechanical and dielectric properties of short sunn hemp fiber-reinforced polymer composite in correlation with fine structure of the fiber

Abstract

Present investigation is aimed on chemically modified of Sunn Hemp (Crotalaria juncea) fiber for composite fabrication. An increment in cellulose crystallinity with crystallite size is observed from X-ray diffraction study. The signature of impurities removal and an uneven surface are confirmed from Fourier Transmission Infrared Spectroscopy and Field Emission Scanning Electron Microscopy. Afterwards, both raw sunn hemp-reinforced fiber composite and dewaxed sunn hemp fiber-reinforced composite were fabricated using hand lay out method and the mechanical as well as dielectric properties of composite are studied. A better mechanical strength is found in DSHC which may attribute to rough surface and increased cellulose crystallinity through dewaxing process that promoted a fine interfacial bonding between fiber and matrix. Dielectric constants and losses are found to be less in dewaxed sunn hemp fiber-reinforced composite in comparison to raw sunn hemp-reinforced fiber composite due to decrease of water polar groups, which lead to lessening the effect of space charge polarization by treatment. Complex impedance and modulus study revealed the presence of single relaxation process in both systems. Lower ac conductivity value is observed in dewaxed sunn hemp fiber-reinforced composite due to decreasing of conducting polar OH groups. As a whole, the effort is established to correlate the mechanical and dielectric properties with fine structural parameters of the fiber.

Complex Impedance and Modulus Analysis on Porous and Non-Porous Scaffold Composites Due to Effect of Hydroxyapatite/Starch Proportion

“…The HAp/ST interactions hinder the polymer cooperative chain segmental dynamics and induce the accumulation of mobile charge carriers on the HAp/ST interfaces for the formation of a self-induced potential well. Hence, the short-range hopping of charge carriers is confined to the self-induced potential well [ 27 , 33 , 34 , 35 ]. As can be observed from Figure 3 , M′ and M″ of the porous HAp/ST composites decrease and increase, respectively, when the ST proportion increases from 60 wt% to 90 wt%.…”

Investigation of Dielectric and Mechanical Properties of Pretreated Natural Sunn Hemp Fiber-Reinforced Composite in Correlation with Macromolecular Structure of the Fiber

“…The dewaxing process is carried out by soaking fiber in the solution mixture of ethanol and benzene in the volume ratio of 1:2, cooked for 2 h of a heating−cooling method in a water bath at a range of 40−80 °C for 12 h. A comprehensive study of the effect of dewaxing on the fiber correlating with the mechanical and dielectric properties of composites is reported elsewhere. 22 The untreated and dewaxed fibers are denoted as raw sunn hemp (RSH) and dewaxed sunn hemp (DSH), respectively.…”

Recent developments and challenges in natural fiber composites: A review

“…The optimum value of DC was observed in 20 wt% fiber‐loaded composites, because of interfacial polarization at a lower frequency range. [ 80 ] Dash et al (2020) [ 81 ] evaluated the dielectric properties of hemp fiber‐reinforced polymer composites under temperature and frequency dependence. The DC value of hemp composite was continuously improved until the temperature reaches up to 413 K. A steady variation of DC values was observed from ambient temperature to nearer 318 K and further goes high.…”