Effects of Alkali Treatment on the Mechanical Properties and Moisture Absorption Behavior of Flax/polypropylene Composites

ABSTRACT

Flax fiber is one of the strongest natural fibers. However, it is highly susceptible to moisture absorption and has poor adhesion with polymer matrix. Alkali treatment of flax fiber was considered in this study aiming to overcome this issue. Four alkali solutions with different NaOH concentrations, i.e., 1 wt. %, 5 wt. %, 10 wt. %, and 15 wt. %, were prepared covering both low and high concentrations. It is successfully demonstrated that polypropylene composites reinforced by alkali-treated flax fibers not only absorbed less moisture but had better tensile and bending properties. At a NaOH concentration of 5 wt. %, maximum decrease in moisture absorption and optimum improvement in mechanical properties were simultaneously achieved. Further increase in NaOH concentration resulted in degradation of both hygrothermal durability and mechanical properties. The underlying mechanisms were comprehensively explored considering both compositional and microstructural changes due to alkali treatment.

摘要

亚麻纤维是最强的天然纤维之一. 然而, 它极易吸湿, 与聚合物基体的附着力差. 为了解决这一问题, 本研究考虑了亚麻纤维的碱处理. 制备了四种不同NaOH浓度的碱溶液, 即1 wt.%、5 wt.%, 10 wt.%和15 wt.%, 涵盖低浓度和高浓度. 研究表明, 经碱处理的亚麻纤维增强聚丙烯复合材料不仅吸湿量少, 而且具有较好的拉伸和弯曲性能. 当NaOH浓度为5 wt.%时, 吸湿性最大降低, 机械性能最佳改善. NaOH浓度的进一步增加导致湿热耐久性和机械性能的退化. 综合考虑碱处理引起的成分和微观结构变化, 对其潜在机理进行了全面探讨.

关键词:

• 亚麻纤维
• 半纤维素
• 碱处理
• 湿热
• 拉伸
• 弯曲

KEYWORDS:

• Flax fiber
• hemicellulose
• alkali treatment
• hygrothermal
• tensile
• bending

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

This research work was supported by “the Fundamental Research Funds for the Central Universities” [WUT: 2019III074GX] and the Foshan Xianhu Laboratory of the Advanced Energy Science and Technology Guangdong Laboratory.