Efeito dos tratamentos de silanização e acetilação em fibras de Luffa cylindrica para aplicação em compósitos

Abstract

Although lignocellulosic fibers (LF) have several advantages, these fibers have a hydrophilic character, which considerably decreases the fiber/matrix interfacial interaction in polymer composites. Due to this, chemical or surface treatments are required to increase fiber/matrix compatibility. The present work had the objective of improving the interaction between Luffa cylindrica (LC) fiber and polyester matrix. Polyester matrix composites were developed and reinforced with 10, 20, and 30% in volume of untreated LC fibers, initially. Subsequently, the chemical treatments of silanization with silane coupling agent (3-methacryloxypropril-trimethoxy-silane) diluted in acetone and acetylation treatment with acetic anhydride and acetic acid with sulfuric acid as catalyst in the 30% composition were performed. From the X-ray diffractometry analysis, it was possible to observe the similarity of the diffractogram of the silanized fiber with the characteristic curve of LF, in contrast, the acetylated fiber obtained a distinct result, being similar to cellulose acetate. The spectrograms confirmed the chemical modification that acetylation caused in the fiber. An increase of 1380% and 1864% in impact strength was obtained for the silanized and acetylated composites, respectively. Meanwhile, the thermal analysis showed the thermal stability of the acetylated fiber up to 200ºC, while the raw fiber and silanized fiber started their degradation process at 261ºC. Photomicrographs obtained by Scanning Electron Microscopy confirmed the higher adherence of treated fibers in the matrix, and the Energy Dispersive X-Ray Spectroscopy analysis verified the incorporation of Si in the fiber. The moisture absorption test assured the hydrophobicity of the acetylated fiber. Given these results, this work indicates that the treatments performed were efficient in increasing the fiber/matrix compatibility.