Mechanistic insights on nanosilica self-networking inducing ultra-toughness of rubber-modified polylactide-based materials

Jérémy Odent,Jean-Marie Raquez,Jean-Michel Thomassin,Jean-Michel Gloaguen,Franck Lauro,Christine Jérôme,Jean-Marc Lefebvre,Philippe Dubois

doi:10.1179/2055033215y.0000000005

Abstract

Developing novel strategies to improve the impact strength of PLA-based materials is gaining a significant importance in order to enlarge the range of applications for this renewable polymer. Recently, the authors have designed ultra-tough polylactide (PLA)-based materials through co-addition of rubber-like poly(ϵ-caprolactone-co-d,l-lactide) (P[CL-co-LA]) impact modifier and silica nanoparticles (SiO2) using extrusion techniques. The addition of silica nanoparticles into these immiscible PLA/P[CL-co-LA] blends altered their final morphology, changing it from rubbery spherical inclusions to almost oblong structures. A synergistic toughening effect of the combination of P[CL-co-LA] copolymer and silica nanoparticles on the resulting PLA-based materials therefore occurred. To explain this particular behavior, the present work hence aims at establishing the mechanistic features about the nanoparticle-induced impact enhancement in these immiscible PLA/impact modifier blends. Incorporation of silica nanoparticles of different surface treatments and sizes was thereby investigated by means of rheological, mechanical and morphological methods in order to highlight the key parameters responsible for the final impact performances of the as-produced PLA-based materials. Relying on video-controlled tensile testing experiments, a toughening mechanism was finally proposed to account for the impact behavior of resulting nanocomposites.

Highlights

To generate rubber-toughened thermoplastics with optimal mechanical properties, the rubber phase morphology and polymeric matrix–rubbery domain interfacial properties must be properly controlled.[1,2,3,4,5] The morphology of a two-phase system usually results to a balance between the breakup and coalescence of the dispersed domains in the flow field.[6]
As reported, loading silica nanoparticles into PLA/P[CL-coLA] blends leads to the increase in viscosity of the resulting compositions, retarding the coalescence of P[CL-co-LA] droplets and affecting the overall shape and average size of dispersed microdomains
The compatibility of PLA/P[CL-co-LA] blends can be dramatically improved by the addition of silica nanoparticles, leading to the formation of self-networked structures originated from rubbery impact modifier within the matrix

Summary

Introduction

To generate rubber-toughened thermoplastics with optimal mechanical properties, the rubber phase morphology (domain size and related size distribution) and polymeric matrix–rubbery domain interfacial properties must be properly controlled.[1,2,3,4,5] The morphology of a two-phase system usually results to a balance between the breakup and coalescence of the dispersed domains in the flow field.[6]. Incorporation of silica nanoparticles of different surface treatments and sizes was thereby investigated by means of rheological, mechanical and morphological methods in order to highlight the key parameters responsible for the final impact performances of the as-produced PLA-based materials.

Results

Conclusion