Study on interfacial properties of unidirectional flax/vinyl ester composites: Resin manipulation on vinyl ester system

Abstract

Flax fibers are widely used as reinforcements in bio-based polymer matrix composites. This study investigated the hydrophilic nature and surface purity of flax fiber that affects fiber/matrix adhesion in combination with hydrophobic structural polymers via matrix modification and the utilization of fiber treatment, specifically in a flax/vinyl ester (VE) composite. A new method to manipulate the vinyl ester system with acrylic resin (AR) was developed to produce flax reinforced. On the other hand, different types of chemical and physical treatments were applied on the flax fiber. FTIR was applied to evaluate the effects of surface treatments. Dynamic mechanical analysis (DMA) was used to analyze the unmodified and modified VE resin system. The surface of untreated and treated flax fibers and their composites were analyzed by scanning electronic microscopy (SEM). Sodium ethoxide-treated flax/ VE with 1% (wt) AR caused the best mechanical performance among all the flax/VE composites evaluated.

Effect of Chemical Treatment of Flax Fiber and Resin Manipulation on Service Life of Their Composites Using Time-Temperature Superposition

“…However, when both treatments are combined, flexural modulus is increased by 5%. Similar results were observed in the study done by Huo et al [34,36]. Alkaline treatment of North American (NA) flax had 5%-10% increasing effect on flexural strength.…”

“…Addition of AR to the VE resin has increased the tensile strength between 8% and 11% for untreated and alkaline treated flax fiber composites, respectively. This is the indication that as expected, addition of AR has improved the efficiency of load transfer to the matrix [36]. Alkaline treatment has been effective in increasing tensile strength of the composite by 5% and when combined with the addition of AR to the resin, the increase in tensile strength is 17% resulting in the highest tensile strength.…”

“…In order to minimize the effect of shrinkage of the fiber as the result of alkaline treatment [36], NaOH/ethanol solution was used. To perform the alkaline treatment, fibers were immersed into 1500 mL of 10 g/L sodium hydroxide/ethanol solution at 78˝C for 2 h. Fibers were then washed with distilled water until no color remained in the water.…”

“…Addition of compatibilizer with the same repeat unit as the initial matrix will reduce the phase separation of the thermoset resin and result in internal stress and improvement of mechanical performance of the matrix [33,35]. Huo et al [33,34,36] used Acrylic Resin (AR) to manipulate VE system in order to improve mechanical performance of natural fiber reinforced composites. Acrylic resin is a highly viscous liquid, and is used particularly in combination with cellulose nitrate [34].…”

“…There are numerous studies that investigate the effect of fiber treatment on mechanical properties of resulting composites [36,[53][54][55][56]. However, to the best of authors' knowledge, there are no studies that investigate the effect of these treatments on long-term creep behavior of long continuous natural fibers/thermoset composites.…”