Preparation and characterization of EVA/PLA/sugarcane bagasse composites for water purification

Abstract

Poly(lactic acid)/ethylene vinyl acetate blends and poly(lactic acid)/ethylene vinyl acetate/sugarcane bagasse composites were prepared by melt mixing. The lower viscosity of poly(lactic acid), the lower interfacial tension between poly(lactic acid) and sugarcane bagasse, and the wetting coefficient of poly(lactic acid)/sugarcane bagasse being larger than one, all suggested that sugarcane bagasse would preferably be in contact with poly(lactic acid). A fairly good dispersion of sugarcane bagasse was observed in the composites. Exposed fibre ends were observed in the composite micrographs, which were believed to add to the efficiency of metal adsorption. The impact properties depended more on the poly(lactic acid):ethylene vinyl acetate ratio than on the presence of sugarcane bagasse. The poly(lactic acid)/ethylene vinyl acetate blends showed two melting peaks at approximately the same temperatures as those of the neat polymers, which confirms the complete immiscibility of poly(lactic acid) and ethylene vinyl acetate at all the investigated compositions. Sugarcane bagasse-related weight loss occurred at higher temperatures for sugarcane bagasse in the composites, which could have been the result of the sugarcane bagasse being protected by the polymers, or a delay in the diffusion of the sugarcane bagasse decomposition products out of the sample. Water absorption increased with an increase in sugarcane bagasse loading in the composites. More lead was adsorbed than one would expect if the partial coverage of the fibre by the polymer is taken into account, and therefore it may be assumed that some of the lead was trapped inside the cavities in the composites and that the polymers may also have played a role in the metal complexation process, since both polymers have functional groups that could interact with the lead ions. The metal impurities underwent monolayer adsorption.

Poly(lactic acid)/ethylene vinyl acetate copolymer blend composites with wood flour and wollastonite: Physical properties, morphology, and biodegradability

“…From Fig. , the TG and DTG curves of WF disclosed a gradual evaporation of the absorbed moisture and/or the volatilization of the extractives (low molecular mass compounds) existed in the WF (~3 wt%) in the range of 64°C–93°C , and a further three‐step process of the major WF constituents (hemicellulose, cellulose, and lignin) in the range of 275°C–460°C. The degradation temperature intervals of these constituents were partially overlapped with each other, and also depended on their contents.…”

“…7). The first step in the range of 316.6 C-360.3 C with the T max 1 at 345 C-348 C was assigned to the PLA decomposition and the EVA deacetylation together with the first main step of the WF degradation, while the second one in the range of 443.8 C-486.3 C with the T max 2 at 467.3 C-468.8 C was a combination of the degradation of the EVA main chain and the lignin [14]. It is seen that the incorporation of WF and/or WT into the 90/10 (wt%/wt%) PLA/EVA blend caused the composites to start degrading at a lower temperature, and thus negatively affected the thermal stability of the composites.…”

“…The DTG curve of WF (Fig. 7b) showed a small shoulder (275 C-325 C) related to the degradation of hemicellulose and the starting degradation of lignin, a large degradation peak (~365 C) attributed to the cleavage of glycosidic linkages in the cellulose molecules [14], and then a small shoulder at a higher temperature region (410 C-460 C) which mainly involved the complete degradation of lignin [14]. The char yield of the WF (20% at 600 C) was noticeably higher than that of the pure polymers, owing to the ring structure of cellulose and the phenolic structure of lignin.…”

“…To work out some of these drawbacks, PLA needs soft/flexible polymers and fillers to improve its flexibility, toughness, strength, and workability for practical applications . A number of researchers have modified PLA by incorporating the second polymeric minor phase, such as polycaprolactone , poly(butylene succinate) , thermoplastic polyurethane , ethylene vinyl acetate (EVA) copolymer , poly(butylene adipate‐ co ‐terephthalate) , epoxidized natural rubber , and linear low‐density polyethylene in an attempt to improve the properties and processability.…”

“…Among these polymers, EVA is a good candidate to be blended with PLA owing to its high flexibility and excellent impact strength . EVA is commercially available as rubbers, thermoplastic elastomers, and plastics, depending mainly on its vinyl acetate (VA) content and molecular weight .…”