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Article

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

1
Department of Material and Environmental Technology, Tallinn University of Technology, Ehitajate tee 5, 19086 Tallinn, Estonia
2
InnoRenew CoE, Livade 6, 6310 Izola, Slovenia
3
Department of Civil Engineering and Architecture, Tallinn University of Technology, Ehitajate tee 5, 19086 Tallinn, Estonia
*
Author to whom correspondence should be addressed.
Academic Editor: Costantino Menna
Materials 2021, 14(15), 4332; https://doi.org/10.3390/ma14154332
Received: 22 June 2021 / Revised: 28 July 2021 / Accepted: 30 July 2021 / Published: 3 August 2021
(This article belongs to the Special Issue Laser Processing for Composite Materials)
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). View Full-Text
Keywords: hemp fiber composites; water absorption; hygroscopic properties; thermal properties; fire resistance hemp fiber composites; water absorption; hygroscopic properties; thermal properties; fire resistance
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MDPI and ACS Style

Alao, P.F.; Marrot, L.; Kallakas, H.; Just, A.; Poltimäe, T.; Kers, J. Effect of Hemp Fiber Surface Treatment on the Moisture/Water Resistance and Reaction to Fire of Reinforced PLA Composites. Materials 2021, 14, 4332. https://doi.org/10.3390/ma14154332

AMA Style

Alao PF, Marrot L, Kallakas H, Just A, Poltimäe T, Kers J. Effect of Hemp Fiber Surface Treatment on the Moisture/Water Resistance and Reaction to Fire of Reinforced PLA Composites. Materials. 2021; 14(15):4332. https://doi.org/10.3390/ma14154332

Chicago/Turabian Style

Alao, Percy F., Laetitia Marrot, Heikko Kallakas, Alar Just, Triinu Poltimäe, and Jaan Kers. 2021. "Effect of Hemp Fiber Surface Treatment on the Moisture/Water Resistance and Reaction to Fire of Reinforced PLA Composites" Materials 14, no. 15: 4332. https://doi.org/10.3390/ma14154332

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