Influence of flax fibers on network formation of DGEBA/DETA matrix

ABSTRACT

Natural fibers and particularly flax fibers have a great potential to replace glass fibers in composite materials. However, the interaction between these fibers and thermoset matrices remains unclear and results in a weak interface affecting the mechanical properties of the composite. This study was carried out to investigate the impact of natural fibers on the chemical reaction between the resin and the hardener, studying the interaction of fibers with each component separately to understand more precisely the phenomena involved. The results show that the contact with the fibers involves a change of the matrix properties that has been attributed to the water absorbed on their surface. On the one hand, water could modify amine functions of the hardener leading to a decrease of 40°C of matrix glass transition temperature (T_g). This issue could be corrected by adding a 16% excess of hardener. On the other hand, the water added to the resin could also accelerate the epoxide/amine reaction increasing slightly the T_g of the matrix and also generating weaker distinct networks of lower T_g by post-modification of the hardener. Therefore, the control of the water content in flax fibers is a crucial parameter for composite manufacturing.

KEYWORDS:

• Curing reaction
• flax fibers
• composite manufacturing
• absorbed water
• epoxy resin
• amine hardener

Disclosure Statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

The research leading to these results has received funding from ADEME under the grant agreement no [1501C0050]. Thesis of Mathieu BOUTIN was partially funded by ANRT (National Association of Research and Technology).