Morphology and Properties of Polylactic Acid Composites with Butenediol Vinyl Alcohol Copolymer Formed by Melt Blending

Abstract

Due to its poor toughness and hydrophilicity, the application of polylactic acid (PLA) in the field of absorbent sanitary materials is restricted. A butenediol vinyl alcohol copolymer (BVOH) was used to improve PLA via melt blending. The morphology, molecular structure, crystallization, thermal stability, tensile property, and hydrophilicity of PLA/BVOH composites with different mass ratios were investigated. The results show that the PLA/BVOH composites possessed a two-phase structure with good interfacial adhesion. The BVOH could effectively blend into PLA without a chemical reaction. The addition of the BVOH promoted the crystallization of PLA, improved the perfection of the crystalline region, and increased the glass transition temperature and melting temperature of PLA in the heating process. Moreover, the thermal stability of PLA was markedly improved by adding the BVOH. The addition of the BVOH also had a significant effect on the tensile property of the PLA/BVOH composites. When the content of the BVOH was 5 wt.%, the elongation at the break of the PLA/BVOH composites could reach 9.06% (increased by 76.3%). In addition, the hydrophilicity of PLA was also significantly improved, and the water contact angles decreased with the increase in the BVOH content and time. When the content of the BVOH was 10 wt.%, the water contact angle could reach 37.3° at 60 s, suggesting good hydrophilicity.

Enhanced hydrophilicity of low melting point polylactic acid by butenediol vinyl alcohol copolymer via melt blending

“…These images clearly indicate that LMAB x blends possess a clear two-phase structure (sea-island structure). It is obvious that LMPLA (major component) forms the continuous phase (sea phase), and BVOH (minor component) forms the dispersed phase (island phase) [35]. It can be observed that LMAB x blends all exhibit a homogenous morphology with no visible aggregates, confirming a good dispersion of BVOH in a granular state.…”

“…The bands at 1180 cm −1 and 1081 cm −1 are related to the stretching vibration of C-O-C. Moreover, the small bands at 2996 cm −1 and 2948 cm −1 belong to the asymmetric and symmetric stretching vibration of -CH 3 , respectively [28,[34][35][36]. For original BVOH, the broad band at 3310 cm −1 belongs to the O-H stretching vibrations of the hydroxyl groups.…”

“…The bands at 2918 cm −1 and 2851 cm −1 belong to the asymmetric and symmetric stretching of -CH 2 . The bands at 1452 cm −1 and 1088 cm −1 are associated with C-OH stretching vibration, and at 1249 cm −1 to the C-C stretching vibration [32,33,35]. Furthermore, the band at 1735 cm −1 is attributed to the C=O stretching vibration which indicates the existence of byproducts during the synthesis of BVOH, because there is no C=O bond in the molecular structure of BVOH.…”

“…As a multifunctional new copolymer, BVOH exhibits good melt processibility, biodegradability and hydrophilicity [33,34]. In our previous research [35], BVOH has also been used to modify the mechanical property and hydrophilicity of conventional PLA via melt blending, indicating that BVOH shows good compatibility with conventional PLA and decreases the water contact angle. Therefore, the hydrophilicity of LMPLA is also improved by melt blending with BVOH in this work.…”