Effects of plasticizers on physical and mechanical properties of modified cellulose films from waste cotton fabrics

Abstract

The aim of this research was to study the effects of type and concentration of plasticizer on the properties of cellulose laurate films. Firstly, cellulose from waste cotton fabric was modified with lauroyl chloride under esterification reaction by conventional and microwave heating methods. Then, the optimum condition for esterification reaction under both heating methods was investigated in terms of temperature, microwave power, and time. In addition, the chemical structure of the obtained product was characterized by FTIR and 1H-NMR. The results showed that the maximum degree of substitution value and %weight increase (WI) for conventional and microwave heating were at 60 °C for 12 hours and at 240 watt 90 second, respectively. Cellulose laurate showed the existence of the ester carbonyl group stretching at 1746cm-1(C=O) and the increase in the intensity of two peak at 2853 and 2924 cm-1,attributed to the methyl band (C-H stretching) associated with the lauroyl substituent. Furthermore, the morphology of esterified cellulose revealed aggregation of acyl group on surface of cellulose. Then, the cellulose laurate powder from both heating methods was converted into plastic film by casting method using triethyl citrate (TEC), dibutyl phthalate (DBP), and epoxidized soy bean oil (ESO) as the plasticizers. The content of their plasticizers was varied from 3%, 5%, 7% and 9% (w/w) of dry cellulose laurate. It was found that the films from cellulose laurate prepared under conventional heating showed better mechanical properties than the films from cellulose laurate prepared under microwave heating. However, the film from cellulose laurate prepared under microwave heating exhibited higher water absorption and biodegradability than that from conventional heating. In the case of plasticizer, it was found that type and content of plasticizer had effects on the tensile properties and significant effects on the water absorption and biodegradability of cellulose laurate films. The effect of plasticizer on properties of the films from cellulose laurate prepared under both heating sources showed a similar trend. The films plasticized with TEC was found to be a more efficient plasticizer than DBP and ESO, respectively. The suitable concentration of TEC was 5 %( w/w).