Evaluating Modified Tannin Esters as Functional Additives in Polypropylene and Biodegradable Aliphatic Polyester

Abstract

Esterified and native condensed tannins have been evaluated in polypropylene and the aliphatic polyester Bionolle. Tannin esters at typical plastic additive loadings have minimal effect on plastic mechanical properties. In assessing functional equivalence tannin esters inhibit the effects of UV degradation in both polypropylene and Bionolle with tannin hexanoate acetate having greater efficacy than a synthetic UV stabiliser at comparable loading. Oxidative induction testing also suggests the tannin esters can act to prevent oxidative degradation of polypropylene. However, retention of antioxidant capacity was crucial to inhibiting oxidative degradation. Outcomes suggest bio‐based tannin additives have potential to substitute synthetic additives and improve plastic sustainability credentials.

Dynamically Cross-Linked Tannin as a Reinforcement of Polypropylene and UV Protection Properties

“…Moreover, this chemical modified biopolymer reduces not only the hydrophilicity but also develops in some cases functional property. For example, tannin-based epoxy resin (with 5, 10 or 20 phr) can provide enhanced dynamic thermal and process stability and improved the rheological properties on PVC [26]; acetylated tannin or esterified tannin exhibited improved miscibility with hydrophobic plastic matrix (e.g., poly(butylene succinate), PP, aliphatic polyester, poly(lactic acid)), and UV stability [27,28,29]. The addition of compatibilizers is also an effective pathway to improve biopolymers and plastics matrix by the formation of bonds, maleic anhydride grafted polypropylene (MAPP) being one of the most important compatibilizers for a PP matrix due to the high reactivity of maleic anhydride [30,31].…”

Modifying biodegradable plastics with additives based on condensed tannin esters

“…There is a range of bioderived plastic additives in development ranging from fermentation products and modified vegetable oils to those based on plant extracts such as lignin . The use of polyphenolic tannins remains relatively unexplored with few examples of these compounds blended with plastics . Condensed tannins are polyphenolic oligomers based on a flavanyl repeat unit (Figure ).…”

Natural antioxidants as stabilizers for polymers

“…Attempts are made to improve the miscibility of these compounds with polymers by esterification with anhydrides. The application of various pine bark tannin esters increased resistance against photo-degradation caused by ultraviolet radiation in PLA [176], while photo-and thermo-oxidative degradation was hindered in PP and Bionell (poly-butylene-succinate-adipate) [177]. The efficiency of the additives increased with the length of the esters, which beneficially modified the solubility of the substance in the polymers [178].…”