Preparation And Performance Exploration Of Biodegradable Polymer/Tannin Composites

Tannins are polyphenols that are present in many plants.The tannin resources of China are pretty rich;however,high-value applications are needed to explore.The composites based on tannins and three biodegradable polymers bearing various characteristics,poly(lactic acid)(PLA),polyvinyl alcohol(PVA)and soy protein isolate(SPI),were carried out in the current study.The PLA/tannin composites were prepared via melt extrusion,the properties of resulting composites caused by the poor compatibility of PLA and tannin was improved by acetylation of tannin and dicumyl peroxide(DCP).Young's modulus,tensile property and elongation at break of the composite based on PLA and acetylated tannin increased 11.7%,6.4% and 100% than that of the composite based on PLA and unmodified tannin.In addition,acetylated tannin contributed to an enhanced crystallinity and thermal property of the resulting composites.For the first time,the 3D printing filament was prepared by PLA and up to acetylated tannin,and excellent 3D printing capacity was found between180??220?.Moreover,a stronger interfacial adhesion between PLA and acetylated tannin can be improved via the free radical reaction initiated by low concentration DCP.Higher glass transition temperature,crystallinity and thermal stability of DCP modified PLA/acetylated tannin composite were observed compared with the unmodified one.More efficient free radical reaction can be found in PLA and tannin in high acetylation degree.Simple one-step compatibilization of PLA and tannin with the help of polymeric methylene diphenyl diisocyanate(p-MDI)and 3-aminopropytriethoxysilane was firstly investigated.With this approach,the tensile strength and Young's modulus of p-MDI/3-aminopropytriethoxysilane modified PLA/tannin composites were 19.1%/12.8% and nearly 10% higher than the unmodified one.Besides,the crystalline,melting temperature and thermal stability of the modified PLA/tannin composite improved with the enhanced interfacial adhesion property.Especially for p-MDI modified PLA/tannin composite,the initial and maximum degradation temperature were significantly improved.PVA/tannin film was prepared by using a simple solvent casting method and the effects of three cross-linkers(glyoxal,glutaraldehyde and dialdehyde starch)on the properties of PVA/tannin films were investigated in this study.The presence of cross-linkers promoted the transparency,water vapour permeability(except glyoxal),mechanical property and thermal stability of the resulting PVA/BT films.The glutaraldehyde cross-linked PVA/tannin film exhibited lower DHHP radical scavenge activity since glutaraldehyde promoted the interfacial adhesion of PVA and tannin,slowing the release of tannin from the film.Based on the experimental results,glutaraldehyde was considered the most suitable cross-linker to prepare PVA/tannin film.The tensile strength of PVA/tannin composite displayed no obvious deterioration when PVA incorporated with less than 15 wt% tannins.The thermal stability of PVA/BT films increased with increasing tannin loading content,however,the DPPH free radical scavenge activity of resulting films were barely affected.SPI films were cross-linked by tannin and prepared using a solvent casting method.The tensile strength of SPI film incorporated with tannin increased nearly two times,however,tannin loading content barely affected the tensile strength but slightly decreased the flexibility of the resulting films.The moisture content,water-solubility,water vapour permeability and oxygen permeability of SPI/tannin films tend to decrease,while the DPPH free radical scavenging activity and thermal stability increased with increasing tannin content.The tensile strength,elongation at break,and thermal stability of the SPI/tannin films increased with the increase of p H and temperature,however,the free radical scavenging ability decreases.