Toughening of poly(lactic acid) without sacrificing stiffness and strength by melt-blending with polyamide 11 and selective localization of halloysite nanotubes

Abstract

Abstract. This paper aims at improving the mechanical behavior of biobased brittle amorphous polylactide (PLA) by extrusion melt-blending with biobased semi-crystalline polyamide 11 (PA11) and addition of halloysite nanotubes (HNT). The morphological analysis of the PLA/PA11/HNT blends shows a strong interface between the two polymeric phases due to hydrogen bonding, and the migration of HNTs towards PA11 phase inducing their selective localization in one of the polymeric phases of the blend. A 'salami-like' structure is formed revealing a HNTs-rich tubular-like (fibrillar) PA11 phase. Moreover, HNTs localized in the dispersed phase act as nucleating agents for PA11. Compared to neat PLA, this leads to a remarkable improvement in tensile and impact properties (elongation at break is multiplied by a factor 43, impact strength by 2, whereas tensile strength and stiffness are almost unchanged). The toughening mechanism is discussed based on the combined effect of resistance to crack propagation and nanotubes load bearing capacity due to the existence of the fibrillar structure. Thus, blending brittle PLA with PA11 and HNT nanotubes results in tailor-made PLA-based compounds with enhanced ductility without sacrificing stiffness and strength.

Bio‐based thermoplastic polyurethane and polyamide 11 bioalloys with excellent shape memory behavior

“…Interestingly at low PA11 content, this crystallization temperature shifts to 80 °C. As per the reported literature, crystallization at the higher temperature corresponds to bulk crystallization of PA11, which takes place due to effective heterogeneity in the PA11 phase, and crystallization at the lower temperature corresponds to crystallization of PA11 droplets, which needs much larger super‐cooling, this confirms that PA11 is dispersed in TPU matrix in droplets form in PA11–20% blends. Crystallization temperature increases with increase in PA 11 content blend and maximum crystallinity was observed in PA11–50% owing to co‐continuous morphology of the blends.…”

Compatibility in biobased poly(L‐lactide)/polyamide binary blends: From melt‐state interfacial tensions to (thermo)mechanical properties

“…These new classes of biobased PA could theoretically represent ideal blending partners with PLA for high‐performance applications while optimizing the biobased content in the final blend system. Several types of PLA/PA blends have been reported in the recent years such as PLA/PA6, PLA/PA6‐10, PLA/PA10‐10, and PLA/PA11 . Immiscible blends with characteristic matrix/droplet or cocontinuous morphologies are encountered and various compatibilizers have been successfully employed such as the poly(ethylene‐ co ‐octene) elastomer grafted with pendant maleic anhydride moieties, poly(ethylene‐ co ‐glycidyl methacrylate‐ graft ‐styrene‐ co ‐acrylonitrile), and epoxide‐based compounds .…”

“…Improved tensile strength, elongation at break, flexural strength, and unnotched impact strength are reported with high concentrations of epoxy compatibilizer (approximately 3 phr). PLA/PA11 blends have been widely considered in the recent years as both are renewable and form a 100% biobased system in addition to interesting final properties . Compatibilization strategies include ester amide exchange reactions using titanium(IV)isopropoxide and p‐toluenesulfonic acid or the incorporation of nanoparticles such as halloysites, organo‐modified montmorillonite, and sepiolite to get refined morphologies and improved mechanical properties .…”

“…PLA/PA11 blends have been widely considered in the recent years as both are renewable and form a 100% biobased system in addition to interesting final properties . Compatibilization strategies include ester amide exchange reactions using titanium(IV)isopropoxide and p‐toluenesulfonic acid or the incorporation of nanoparticles such as halloysites, organo‐modified montmorillonite, and sepiolite to get refined morphologies and improved mechanical properties . The case of PLA/PA11 blends was thoroughly investigated, and interestingly, several authors concluded about an inherent good compatibility between these two materials without any compatibilizer .…”

Preparation of high toughness and high transparency polylactide blends resin based on multiarmed polycaprolactone-block-poly(l-lactide)

“…Excellent toughness and flexibility of PLA are the basic prerequisites for developing the PLA resin with desired properties. Therefore, development of the PLA-based materials with high toughness has attracted significant research attention in recent years [8][9][10].…”