Effect of Hemp Hurd Biochar and Humic Acid on the Flame Retardant and Mechanical Properties of Ethylene Vinyl Acetate

Abstract

In this work, the combination of biochar produced through a pyrolytic process of hemp hurd with commercial humic acid as a potential biomass-based flame-retardant system for ethylene vinyl acetate copolymer is thoroughly investigated. To this aim, ethylene vinyl acetate composites containing hemp-derived biochar at two different concentrations (i.e., 20 and 40 wt.%) and 10 wt.% of humic acid were prepared. The presence of increasing biochar loadings in ethylene vinyl acetate accounted for an increasing thermal and thermo-oxidative stability of the copolymer; conversely, the acidic character of humic acid anticipated the degradation of the copolymer matrix, even in the presence of the biochar. Further, as assessed by forced-combustion tests, the incorporation of humic acid only in ethylene vinyl acetate slightly decreased both peaks of heat release rate (pkHRR) and total heat release (THR, by 16% and 5%, respectively), with no effect on the burning time. At variance, for the composites containing biochar, a strong decrease in pkHRR and THR values was observed, approaching −69 and −29%, respectively, in the presence of the highest filler loading, notwithstanding, for this latter, a significant increase in the burning time (by about 50 s). Finally, the presence of humic acid significantly lowered the Young’s modulus, unlike biochar, for which the stiffness remarkably increased from 57 MPa (unfilled ethylene vinyl acetate) to 155 Mpa (for the composite containing 40 wt.% of the filler).

Developing Flame Retardant Solutions for Partially Aromatic Polyamide with Phosphine Oxides

“…The absence of reaction between PAP and the three flame retardants was confirmed by 31 . Besides, it is reported in the literature that the effect of EX on the complex viscosity is not only due to the establishment of hydrogen bonds but also to metal cations grafted onto polymer chains by a single link [17,19,46,47]. It is reported that the presence of EX in the polyamide lead to corrosion phenomena, potentially due to the formation of free diethylphosphinic acid [17,35].…”

Industrial Cannabis sativa-Hemp: Biochar applications and disadvantages

“…The electrical conductivity was related to the evolution of the biochar microstructure (development of graphite-like structure and changes in microporosity) in regard with the thermochemical conversion process parameters [44]. Hemp biochar carbonized at 400-600°C were classified as lignocellulosic materials with a good potential for solid biofuel applications [40][41][42][43][44]54]. Specifically, the resulting carbonized biochar presented low moisture content (below 2.50%) favourable for high fuel quality, low volatile matter (27.1-10.4%) likely to show lower particle matter emissions, limited ash content (6.8-9.8%) resulting in low risk of fouling issues during the combustion, high carbon content (73.8-86.8%) suggesting strong energy density, associated with high higher heating values (28.45-30.95 MJ kg− 1) [40][41][42][43][44].…”

“…One of the study investigated reinforcing bio-composites by using biochar produced from hemp straw in E-glass fibre in a vinyl-ester polymer matrix [40][41][42][43][44][45][46][47][48][49][50][51]54]. Another study indicated that the addition of biochar in polyvinyl alcohol/biochar composites increased tensile modulus and storage modulus above the glass transition temperature but reduced the tensile strength, increased the thermal decomposition temperature of the composites, and provided to the composites an electrical conductivity similar to the most carbon nanotube and graphene reinforced polyvinyl alcohol composites [40][41][42][43][44][45][46][47][48][49][50][51].…”

“…Another study indicated that the addition of biochar in polyvinyl alcohol/biochar composites increased tensile modulus and storage modulus above the glass transition temperature but reduced the tensile strength, increased the thermal decomposition temperature of the composites, and provided to the composites an electrical conductivity similar to the most carbon nanotube and graphene reinforced polyvinyl alcohol composites [40][41][42][43][44][45][46][47][48][49][50][51]. The electrical conductivity of biochar, specifically, has attracted attention for the development of batteries, supercapacitors, and pressure sensor materials [40][41][42][43][44][45][46][47][48][49][50][51]54]. Recent other study reported that bio-based carbon from hemp hurds and bast fibres prepared via hydrothermal processing and chemical activation showed interesting specific capacitance and high energy density with good potential for an application as supercapacitor electrodes [40][41][42][43][44][45][46][47][48][49][50][51].…”