Abstract
In the perspective of producing a rigid renewable and environmentally friendly rigid packaging material, two comb-like copolymers of cellulose acetate (AC) and oligo(lactic acid) OLA, feeding different percentages of oligo(lactic acid) segments, were prepared by chemical synthesis in solvent or reactive extrusion in the melt, using a diepoxide as the coupling agent and were used as compatibilizers for poly(lactic acid)/plasticized cellulose acetate PLA/pAC blends. The blends were extruded at 230 °C or 197 °C and a similar compatibilizing behavior was observed for the different compatibilizers. The compatibilizer C1 containing 80 wt% of AC and 14 wt% of OLA resulted effective in compatibilization and it was easily obtained by reactive extrusion. Considering these results, different PLAX/pAC(100-X) compounds containing C1 as the compatibilizer were prepared by extrusion at 197 °C and tested in terms of their tensile and impact properties. Reference materials were the uncompatibilized corresponding blend (PLAX/pAC(100-X)) and the blend of PLA, at the same wt%, with C1. Significant increase in Young’s modulus and tensile strength were observed in the compatibilized blends, in dependence of their morphologic features, suggesting the achievement of an improved interfacial adhesion thanks to the occurred compatibilization.
Highlights
Poly(lactic acid) (PLA), a recyclable and compostable thermoplastic polyester, produced from renewable resources, is currently proposed for many applications, in the perspective of circular and green economy principles [1,2,3,4]
The present work keeps into account the results reported in a previous work [24], where the properties of the PLA/Plasticized AC (pAC) blends were studied in a wide composition range
The copolymers were characterized by infrared spectroscopy after purification and some deacetylation as well as slight grafting of oligomeric lactic acid (OLA) on the AC was observed in a similar extent in all the produced samples, despite of they were produced by synthesis in solvent or reactive extrusion and despite of they were obtained by feeding different OLA and diepoxide contents in the reaction
Summary
Poly(lactic acid) (PLA), a recyclable and compostable thermoplastic polyester, produced from renewable resources, is currently proposed for many applications, in the perspective of circular and green economy principles [1,2,3,4]. The blending with rigid and thermally resistant polymers like for instance polycarbonate (PC) [9,10,11,12], poly(ethylene terephthalate) (PET) [13], and polyamides [14] was explored, but the resulting materials were not fully biodegradable and partially from fossil sources. Cellulose acetate (AC), a biodegradable cellulose ester, is a rigid material, obtained by acetylation of renewable cellulose, and it is currently used in a wide range of applications [15,16,17,18]. PLA and pAC are immiscible materials [23], and need proper compatibilization to improve compounds properties, especially in terms of toughness. Different approaches have been reported on the compatibilization of PLA/AC blends, such as the preparation, by ring opening polymerization, of AC-g-PLA copolymers to be used as compatibilizers [24,25,26]
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