Effect of a chain extender on the rheological and mechanical properties of biodegradable poly(lactic acid)/poly[(butylene succinate)‐co‐adipate] blends

Abstract

Biodegradable polymer blends based on poly(lactic acid) (PLA) and poly[(butylene succinate)-co-adipate] (PBSA) were prepared with a laboratory internal mixer. An epoxy-based, multifunctional chain extender was used to enhance the melt strength of the blends. The morphology of the blends was observed with field emission scanning electron microscopy. The elongational viscosities of the blends, with and without chain extender, were measured with a Sentmanat extensional rheometer universal testing platform. The blends with chain extender exhibited strong strain-hardening behavior, whereas the blends without chain extender exhibited only weak strain-hardening behavior. Measurements of the linear viscoelastic properties of the melts suggested that the chain extender promoted the development of chain branching. The results show that PBSA contributed to significant improvements in the ductility of the PLA/PBSA blends, whereas the chain extender did not have a significant effect on the elastic modulus and strain at break of the blends. The combined blending of PLA with PBSA and the incorporation of the chain extender imparted both ductility and melt strength to the system. Thus, such an approach yields a system with enhanced performance and processability.

Biopolymer Blends Based on Poly (lactic acid): Shear and Elongation Rheology/Structure/Blowing Process Relationships

“…The observed increase could be due to shorter overlapping time of macromolecules during elongational flow. Thus, the occurrence of the strain hardening behavior of linear PLA has been reported in few studies and might be due to its stereo-regularity [15][16][17][18][19][20][21][22][23][24][25][26][27]. In fact, the stereo-regularity of high L-content PLA (98% of L-content in our case) may allow them to form a range of structures when stretched, where helical conformations may form in the melt as a precursor to strain-induced crystallization.…”

“…According to Figure 6b,c, the Cox-Merz rule works fairly well with neat polymers into the shear thinning region but still shows slightly deviation for the modified polymers and their blends. The polydispersity and the heterogeneity explain this deviation from the rule [12][13][14][15][16][17][18][19][20][21][22]. By this way, the elongation properties during processing can ben also influenced.…”

“…However, few works have been dedicated to study the elongational behavior of blends based on PLA in the molten state. Eslami et al [18] evaluated the elongational rheology of PLA/PBSA blends with different blend compositions. They found that PLA/ PBSA blends containing less than 50 wt% PBSA showed no clear strain-hardening behavior.…”

Reactive extrusion of PLA, PBAT with a multi-functional epoxide: Physico-chemical and rheological properties

“…Meng et al [23] reported that Joncryl showed a remarkable thermal stabilization effect on PLA/organo-modified clay nano-composites without negatively affecting the clay dispersion. Recently, Eslami et al [26] investigated the effects of an epoxy-functionalized chain extender (CESA) on the rheological, mechanical and elongation properties of PLA. They found that the shear viscosity, the elasticity and the elongational viscosity of PLA increased as the concentration of chain extender increased.…”

Reactive extrusion of bio-based polymer blends and composites – Current trends and future developments

“…These results are related to formation of low amount of PLA-PBAT copolymers, which act as compatibilizers between phases boundary. Eslami and Kamal [105] used commercial chain extender with tradename CESA ® Extend to modify poly(lactic acid)/poly(butylene succinate-co-adipate) (PLA/PBSA) blends. CESA ® Extend is a multifunctional epoxy-based copolymer produced by Clariant.…”