Mechanical, and Thermal Properties of Biocomposites based on Polylactic Acid and natural fibers: Sisal and Coir

CARLOS RAMIREZ; PETTARIN VALERIA; AGALIOTIS ELIANA M.

Buenos AIres, Caba

Congreso; WCCE11 - 11th WORLD CONGRESS OF CHEMICAL ENGINEERING; 2023

Asociacion Argentina de Ingenieros Quimicos

In recent years, there has been an increasing interest in polylactic acid (PLA) as a substitute for commodity polymers such as polyethylene or polypropylene which is based on its 100% renewable origin, biodegradability, and relatively low cost. However, its low fracture resistance and mechanical properties need to be improved to extend their commercial applications. To overcome this, PLA is reinforced with natural fibers in order to keep biopolymer and biocomposite qualification. This work aims to evaluate the effect of sisal or coir (short length fibers ≈ 3mm) addition in different contents (1; 3 and 5%wt) on surface morphology, mechanical and thermal properties of PLA biocomposite. First, fibers were chopped to 3 mm length and then mixed with PLA 4043D in a Brabender mixer at 50 rpm and 175 ºC for 8 minutes. Then, the mix was dried at 70 ºC in an oven for 24 hours, and it was finally molded in a hydraulic heat press at 170 ºC and applied pressure of 800 psi for 17 min. Biocomposites were evaluated via differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), attenuated total reflection (ATR), mechanical and fracture testing, and scanning electron microscopy (SEM).DSC results showed a crystallinity increased for both biocomposites highlighting that both fibers (sisal and coir) promote polymer crystallization. ATR spectra results for biocomposites showed only the characteristic peaks corresponding to PLA matrix, sisal and coir fibers’, indicating that there are no chemical reactions between the fiber and the resin. Thermal stability of composites decreases with the incorporation of fibers, for both studied systems. On the other hand, Young’s modulus increased for both biocomposites in comparison with neat PLA, where the best value was found with a 3% wt. of coir. It was also observed a slight decrease in tensile strength in comparison with neat PLA which could be to a poor adhesion of fibers with the matrix [1]. Fracture toughness increases with fiber’s concentration in both systems,which could be correlated with SEM observations where was found evidence of voids and fiber detachment from the matrix in fracture surfaces. These results indicate that even though there is a poor interface adhesion between matrix and reinforcement, fibers can induce extra deformation mechanisms increasing energy consumption before fracture.Through this work, the mechanical and thermal properties of PLA/sisal fiber and PLA/coir fiber have been successfully evaluated. The incorporation of natural fibers improves the fracture performance of PLA even though there is a poor adhesion between matrix and fibers. Further work should be done to promote adhesion between components, what is expected to positively affect mechanical performance of biocomposites.