Advances in peroxide‐initiated graft modification of thermoplastic biopolyesters by reactive extrusion

Abstract

We report recent advances in the solvent‐free reactive extrusion of thermoplastic biopolyesters, in the presence of peroxide initiators and tri‐functional cross‐linking/ chain extending agents. The resulting compounds have improved processability and properties compared to the starting materials, including higher melt strength due to long‐chain branching, higher crystallinity, faster crystallization kinetics, and improved mechanical properties. We demonstrate that these strategies are effective in thermoplastic biopolyesters, such as poly(lactide) (PLA) and various poly(hydroxyalkanoates) (PHAs), including poly(hydroxybutyrate) (PHB), and medium‐chain length PHAs. In addition to the improvements in properties, this approach has significant benefits in polymer processing operations, including blend compatibilization, and foaming. We also demonstrate that crosslinked PLA particles prepared by reactive extrusion using peroxide and a tri‐functional coagent, serve as very effective nucleating additives, resulting in crystallization half‐times as low as 1 min, and heat deflection temperature as high as 140°C. These modifications do not have adverse effects on the hydrolytic degradation characteristics of PLA.

The Effects of Nucleating Agents and Processing on the Crystallization and Mechanical Properties of Polylactic Acid: A Review

“…The potassium salt of 5-dimethyl sulfoisothalate, also known as LAK-301 and commercialized by Takemoto Oil & Fat Company (Takemoto Oil & Fat, Aichi, Japan), has proven effective in modifying the crystallization of PLA. LAK-301 exhibits a notable nucleation effect on PLA, enhancing both the nucleating density and the initial crystallization rate while reducing the size of PLA spherulites [ 61 , 79 , 125 , 126 , 127 , 128 ]. Barczewski et al incorporated basalt powder (BP) as an inorganic filler and combined it with LAK-301 as an organic nucleating agent in PLA [ 125 ].…”

In Service Performance of Toughened PHBV/TPU Blends Obtained by Reactive Extrusion for Injected Parts

“…Regarding the limitations in mechanical behavior, reactive blending with elastomeric thermoplastics seems to be an efficient approach to enhance the toughness of brittle polymers by rubber toughening, where the dispersed elastomeric secondary phase acts as an impact modifier, increasing the impact-absorbed energy of the resin [20][21][22]. Reactive blending could also play an important role in improving the thermal stability if the compositions are properly formulated [23][24][25].…”

Influence of Branching on the Rheology, Filmability and Mechanical and Optical Properties of a Biodegradable and Compostable Co-Polyester

“…Recently, the same strategy has been applied also to biodegradable polymers with excellent results. For example, Tiwary et al [30] added chain extenders agents (peroxide initiators), in reactive extrusion, to thermoplastic biopolyesters, such as poly(lactide) (PLA) and various poly(hydroxyalkanoates) (PHAs), including poly(hydroxybutyrate) (PHB), aiming to improve the processability and the proprieties of the polymers. Similarly, Zhao et al [31] and Tuna et al [32] used a commercial multi-epoxide chain extender (Joncryl ® ) to improve PLA melt strength, obtaining strain-hardening behavior comparable with film grade LDPE.…”