Influence of accelerated weathering on the physical and structural properties of poly(Lactic-acid)/ poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (pla/phbv) blends

Abstract

The paper aims to study the poly(lactic acid) (PLA) and poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) blend properties after their degradation under 2000 h of accelerated weathering conditions following the ASTM D4329 stan-dard. PLA/PHBV blends form a biphasic system shown by the presence of two distinct glass transition temperatures and melting temperatures in differential scanning calorimetry (DSC) analysis, attributed to the neat polymers regardless of the blend composition. Scanning electron microscopy (SEM) indicated that the addition of high PHBV content to the blend results in a very heterogeneous surface with cavities available for moisture and UV penetration resulting in easier bulk and in-depth degradation of the samples. Thus, the wettability properties (evaluated by contact angle measurements) of the blends changed significantly over the weathering time. On the other hand, the PLA content delays the degradation process of the blends because of the resultant crystallinity from weathering degradation which exhibits a physical barrier to protect the PHBV fraction. PHBV improves the toughness of the blend and acts as a nucleating agent for PLA, promoting its crystallinity during sample preparation. Fourier-transform infrared (FTIR) confirmed photodegradation of all the blends via a Norrish II mechanism.