RESUMEN
Plant waste is a huge source of natural fibers and has great potential in the field of reinforced polymer composites to replace the environmentally harmful synthetic composites. In this study, fibers were extracted from water hyacinth (WH) petiole and sugarcane bagasse (SB) to make nonwovens by wet-laid web formation, and reinforced on the polyester (P) and epoxy (E) resins to make four types of composites namely, water hyacinth nonwoven reinforced epoxy (WH + E), water hyacinth nonwoven reinforced polyester (WH + P), sugarcane bagasse nonwoven reinforced epoxy (SB + E) and sugarcane bagasse nonwoven reinforced polyester (SB + P) composites. Water repellent (WR) on the nonwovens and gamma radiation (GR) on the composites were applied to improve the hydrophobicity and mechanical properties, such as tensile strength (TS), elongation at break and tensile modulus (TM) of the composites. The morphological structure of the fiber surfaces and tensile fractures were analyzed by SEM. FTIR spectra showed changes in functional groups before and after treatment. XRD analysis exhibited an increase in crystallinity for gamma-irradiated composites and a decrease in crystallinity for WR-treated composites compared to untreated composites. The SB composites (SB + E, SB + P) and polyester composites (WH + P, SB + P) showed higher water absorbency and lower mechanical properties than the WH composites (WH + E, WH + P) and epoxy composites (WH + E, SB + E), respectively. Hydrophobicity improved significantly by approximately 57% (average) at a concentration of 10% WR. However, TS and TM were reduced by approximately 24% at the same concentration. Thus, 5% WR is considered an optimum concentration due to the very low deterioration of TS and TM (<10%) but significant improvement in hydrophobicity (~39%) at this dose. On the other hand, GR treatment significantly improved TS, TM and hydrophobicity by 41, 32 and 25%, respectively, and decreased Eb% by 11% at a dose of 200 krd. However, mechanical properties and hydrophobicity deteriorated with further increase in dose at 300 krd. Thus, 200 krd is considered the optimum dose of GR.
RESUMEN
Four types of nonwovens were prepared from different sections of the banana tree e.g., outer bark (OB), middle bark (MB), inner bark (IB) and midrib of leaf (MR) by wet laid web formation. They were reinforced with two different types of matrices e.g., epoxy and polyester, to make eight variants of composites. Treatments including alkali on raw fibers, water repellent on nonwovens and gamma radiation on composites were applied in order to investigate their effects on properties of the composites such as water absorbency, tensile strength (TS), flexural strength (FS) and elongation at break (Eb%). Variations in the morphological structure and chemical composition of both raw banana fibers and fibers reinforced by the treatments were analyzed by Fourier Transform Infrared (FTIR) and Scanning Electron Microscopy (SEM). OB composites exhibited higher water absorbency, TS and FS and lower Eb% compared to other types of composites. Epoxy composites were found to have 16% lower water absorbency, 41.2% higher TS and 39.1% higher FS than polyester composites on an average. Water absorbency of the composites was reduced 32% by the alkali treatment and a further 63% by water repellent treatment. TS and FS of the composites were on average improved 71% and 87% by alkali treatment and a further 30% and 35% by gamma radiation respectively.
RESUMEN
Pineapple leaf fiber (PALF) reinforced polypropylene (PP) composites were prepared by compression molding. The fiber content varied from 25% to 45% by weight. Water uptake percentages of the composites containing various wt% of fiber were measured. All the composites demonstrated lower water uptake percentages and maximum of 1.93% for 45 wt% PALF/PP composite treated with 7(w/v)% NaOH. Tensile Strength (TS), Tensile Modulus (TM), Elongation at Break (Eb %), Bending Strength (BS), Bending Modulus (BM), and Impact Strength (IS) were evaluated for various fiber content. The 45 wt% PALF/PP composite exhibited an increase of 210% TS, 412% TM, 155% BS, 265% BM, and 140% IS compared to PP matrix. Moreover, with the increasing of fiber content, all the mechanical properties increase significantly; for example, 45 wt% fiber loading exhibited the best mechanical property. Fibers were also treated with different concentration of NaOH and the effects of alkali concentrations were observed. The composite treated with 7 (w/v)% NaOH exhibited an increase of 25.35% TS, 43.45% TM, 15.78% BS, and 52% BM but 23.11% decrease of IS compared to untreated composite. Alkali treatment improved the adhesive characteristics of fiber surface by removing natural impurities, hence improving the mechanical properties. However, over 7% NaOH concentration of the tensile strength of the composite reduced slightly due to overexposure of fibers to NaOH.