Effect of Hemp Fiber Surface Treatment on the Moisture/Water Resistance and Reaction to Fire of Reinforced PLA Composites

Abstract

The effects of surface pretreatment (water and alkali) and modification with silane on moisture sorption, water resistance, and reaction to fire of hemp fiber reinforced polylactic acid (PLA) composites at two fiber loading contents (30 and 50 wt.%) are investigated in this work. Moisture adsorption was evaluated at 30, 50, 75 and 95% relative humidity, and water resistance was determined after a 28-day immersion period. The cone calorimetry technique was used to investigate response to fire. The fiber surface treatment resulted in the removal of cell wall components, which increased fiber individualization and homogeneity as shown in scanning microscopic pictures of the composite cross-section. Although the improved fiber/matrix bonding increased the composite’s water resistance, the different fiber treatments generated equal moisture adsorption results for the 30 wt.% reinforced composites. Overall, increasing the fiber amount from 30 to 50 wt.% increased the composite sensitivity to moisture/water, mainly due to the availability of more hydroxyl groups and to the development of a higher pore volume, but fire protection improved due to a reduction in the rate of thermal degradation induced by the reduced PLA content. The new Oswin’s model predicted the composite adsorption isotherm well. The 30 wt.% alkali and silane treated hemp fiber composite had the lowest overall adsorption (9%) while the 50 wt.% variant produced the highest ignition temperature (181 ± 18 °C).

Effect of Biochar Addition on Mechanical Properties, Thermal Stability, and Water Resistance of Hemp-Polylactic Acid (PLA) Composites

“…Reinforcing PLA with plant fibers can enhance the resulting mechanical [ 6 ] and thermal properties [ 7 ]. In particular, long hemp fibers were reported as a potentially effective reinforcement in PLA-based composites that showed improved features [ 8 , 9 , 10 ]. However, the current high price of PLA and other shortcomings, such as thermal, mechanical, and moisture resistance remain key challenges that have limited the use of plant fibers reinforced-PLA composites.…”

Investigation of Efficient Alkali Treatment and the Effect of Flame Retardant on the Mechanical and Fire Performance of Frost-Retted Hemp Fiber Reinforced PLA

“…Chemical or physical treatment of natural fibers has been used in numerous studies to increase performance and minimize many of the issues associated with biocomposite applications [ 5 , 11 ]. The impact of chemical fiber surface treatment on the mechanical and water behavior features of NFRCs has been extensively examined in recent and past research [ 9 , 12 , 13 , 14 , 15 , 16 , 17 , 18 , 19 , 20 , 21 , 22 , 23 , 24 , 25 , 26 ]. However, there is limited research output regarding improving fire performance.…”

Effect of Eco-Friendly Peanut Shell Powder on the Chemical Resistance, Physical, Thermal, and Thermomechanical Properties of Unsaturated Polyester Resin Composites

“…The most common natural filler is wood fiber or flour, which is a waste product in the production of paper [13][14][15]. However, waste rice husks, nut shells, stalks of hemp, sisal, jute, or corn cobs are being used more often [16][17][18]. These natural ingredients reduce the polymer product costs, and on the other hand, they are characterized by good reinforcing properties and biodegradability.…”