Robust polyvinyl alcohol with broad thermoplastic window enabled by controlled citrate-plasticizing adding ways

Abstract

Given that the decomposition temperature is close to the melting point, polyvinyl alcohol (PVA) fails thermoplastic processing. Developing a suitable plasticizer-enhancing system to reduce melting point or increase the decomposition temperature, resulting in generating a temperature window of thermoplastic processing is an urgent research topic in practical processing applications. In this work, triethyl citrate (TEC) (or tributyl citrate (TBC)), as a green plasticizer, was successfully introduced in the PVA matrix by rational and scientific means. To systematically explore the effects of plasticizers on melting point and mechanical properties of the PVA, distinguishing from traditional plasticizer-adding means, the optimized plasticizer was added to the PVA precursor (i.e., polyvinyl acetate (PVAc)), generating a highly effective blend at upon molecular level, which can achieve a uniform phase mixture of plasticizer molecules in PVA after alcoholysis. In this case, small molecular plasticizers participate in the formation of intermolecular hydrogen bonds between PVA molecules, thus forming abundant effective energy dissipation sites. As a result, thus-obtained A-PVA/TEC10 exhibited an elongation at break of 385.3% and toughness of 154.4 MPa, which are 2.87 times and 1.75 times than those of unplasticized PVA, respectively. Also, the elongation at break and toughness of A-PVA/TEC10 are far superior to those of PVA that are prepared by directly blending way. Most importantly, along with the augmentation of the TEC plasticizer in the PVA system, the melting temperature of plasticized PVA achieved after the alcoholysis reaction of PVAc/TEC10 decreased significantly, and slightly increased in decomposition temperature. This work offers a valuable and justified plasticizing strategy for the processability of PVA materials.