RESUMEN
Polylactide (PLA) nanofiber membranes with enhanced hydrophilic properties were prepared through electrospinning. As a result of their poor hydrophilic properties, common PLA nanofibers have poor hygroscopicity and separation efficiency when used as oil-water separation materials. In this research, cellulose diacetate (CDA) was used to improve the hydrophilic properties of PLA. The PLA/CDA blends were successfully electrospun to obtain nanofiber membranes with excellent hydrophilic properties and biodegradability. The effects of the additional amount of CDA on the surface morphology, crystalline structure, and hydrophilic properties of the PLA nanofiber membranes were investigated. The water flux of the PLA nanofiber membranes modified with different CDA amounts was also analyzed. The addition of CDA improved the hygroscopicity of the blended PLA membranes; the water contact angle of the PLA/CDA (6/4) fiber membrane was 97.8°, whereas that of the pure PLA fiber membrane was 134.9°. The addition of CDA enhanced hydrophilicity because it tended to decrease the diameter of PLA fibers and thus increased the specific surface area of the membranes. Blending PLA with CDA had no significant effect on the crystalline structure of the PLA fiber membranes. However, the tensile properties of the PLA/CDA nanofiber membranes worsened due to the poor compatibility between PLA and CDA. Interestingly, CDA endowed the nanofiber membranes with improved water flux. The water flux of the PLA/CDA (8/2) nanofiber membrane was 28,540.81 L/m2·h, which was considerably higher than that of the pure PLA fiber membrane (387.47 L/m2·h). The PLA/CDA nanofiber membranes can be feasibly applied as an environmentally friendly oil-water separation material because of their improved hydrophilic properties and excellent biodegradability.
RESUMEN
Cellulose diacetate (CDA) and L-lactide (L-LA) were used to prepare CDA-g-PLLA with a low glass transition temperature under different process conditions. Given the high glass transition temperature (Tg) of CDA, the thermal processing performance of CDA is poor, which greatly limits its application fields. To decrease the Tg of CDA, graft copolymerization was used in this research. A CDA-g-PLLA graft copolymer was synthesized by grafting CDA with L-LA under different reaction conditions using stannous octanoate as the catalyst and variations in the grafting rate under different reaction conditions were compared. The chemical structure and crystal structure of the CDA-g-PLLA were investigated, and thermal properties were also studied. The results showed that the grafting rate was the highest at the L-LA/CDA mass ratio of 4:1 under a reaction temperature of 150 °C for 90 min, and no poly-L-lactide (PLLA) homopolymer was found among the CDA-g-PLLA graft copolymers after purification. The Tg of CDA-g-PLLA was 54.2 °C, and the initial temperature of weightlessness of CDA-g-PLLA was 218.7 °C. The regularity of the original CDA molecular chains was destroyed after grafting PLLA molecular chains. In this research, we investigated the optimal grafting conditions for CDA-g-PLLA and the CDA-g-PLLA had a low Tg, which improves the thermal processing performance of CDA and broadens its application prospects in the industry.
