In this work, green composites have been developed and characterized using a bio-based polymeric matrix such as BioPBSA and the introduction of 30 wt.% short hemp fibers as a natural reinforcement to obtain materials with maximum environmental efficiency. In order to increase the interfacial adhesion between the matrix and the fiber to obtain better properties in the composites, a reactive extrusion process has been carried out. On the one hand, different additives derived from bio-based itaconic acid have been added to the BioPBSA/HEMP composite, such as dibutyl itaconate (DBI) and a copolymer of PBSA grafted with itaconic acid (PBSA-g-IA). On the other hand, a different copolymer of PBSA grafted with maleic anhydride (PBSA-g-MA) was also tested. The resulting composites have been processed by injection-molding to obtain different samples which were evaluated in terms of mechanical, thermal, chemical, dynamic-mechanical, morphological and wettability and color properties. In relation to the mechanical properties, the incorporation of hemp fibers resulted in an increase in the stiffness of the base polymer. The tensile modulus of pure BioPBSA increased from 281 MPa to 3482 MPa with 30% fiber. The addition of DBI shows a remarkable improvement in the ductility of the composites, while copolymers with IA and MA, generate mechanically balanced composites. In terms of thermal properties, the incorporation of hemp fiber and compatibilizing agents led to a reduction in thermal stability. However, from the point of view of thermomechanical properties, a clear increase in rigidity is achieved throughout the temperature range studied. As far as the color of the samples is concerned, the incorporation of hemp generates a typical color, while the incorporation of the compatibilizing agents does not modify this color excessively. Finally, the introduction of lignocellulosic fibers greatly affects water absorption and contact angle, although the use of additives helped to mitigate this effect.

This research work reports the potential of maleinized linseed oil (MLO) as biobased compatibilizer in polylactide (PLA) and a thermoplastic elastomer, namely, polystyrene-b-(ethylene-ran-butylene)-b-styrene (SEBS) blends (PLA/SEBS), with improved impact strength for the packaging industry. The effects of MLO are compared with a conventional polystyrene-b-poly(ethylene-ran-butylene)-b-polystyrene-graft-maleic anhydride terpolymer (SEBS-g-MA) since it is widely used in these blends. Uncompatibilized and compatibilized PLA/SEBS blends can be manufactured by extrusion and then shaped into standard samples for further characterization by mechanical, thermal, morphological, dynamical-mechanical, wetting and colour standard tests. The obtained results indicate that the uncompatibilized PLA/SEBS blend containing 20 wt.% SEBS gives improved toughness (4.8 kJ/m2) compared to neat PLA (1.3 kJ/m2). Nevertheless, the same blend compatibilized with MLO leads to an increase in impact strength up to 6.1 kJ/m2, thus giving evidence of the potential of MLO to compete with other petroleum-derived compatibilizers to obtain tough PLA formulations. MLO also provides increased ductile properties, since neat PLA is a brittle polymer with an elongation at break of 7.4%, while its blend with 20 wt.% SEBS and MLO as compatibilizer offers an elongation at break of 50.2%, much higher than that provided by typical SEBS-g-MA compatibilizer (10.1%). MLO provides a slight decrease (about 3 °C lower) in the glass transition temperature (Tg) of the PLA-rich phase, thus showing some plasticization effects. Although MLO addition leads to some yellowing due to its intrinsic yellow colour, this can contribute to serving as a UV light barrier with interesting applications in the packaging industry. Therefore, MLO represents a cost-effective and sustainable solution to the use of conventional petroleum-derived compatibilizers.

This work reports on the development of polylactide (PLA) and polycarbonate (PC) blends with different compatibilizers with enhanced toughness. Since both polymers are immiscible, two types of compatibilizers are tested: petrochemical-based copolymers Xibond 160 and Xibond 920 with maleic anhydride and epoxy groups, respectively, and natural-based compatibilizers with the same functionalities, namely maleinized linseed oil (MLO) and, epoxidized linseed oil (ELO). Mechanical, thermal, and morphological characterization shows better properties for the PLA/PC (80/20 wt%) blends with chemically modified natural oils (ELO and MLO). The addition of 5 phr (parts per hundred resin) of MLO gives the maximum values for impact strength and elongation at break. Moreover, the glass transition temperature (T g ) slightly decreases with the addition of natural compatibilizers, thus showing some plasticization effect. Petroleum-derived compatibilizers give interesting results regarding tensile strength and stiffness without plasticization. PLA/PC blends show higher thermal stability than neat PLA, regardless of the compatibilizer used, since PC is much more thermally stable than PLA. The obtained results indicate that both petroleum-based and natural-derived compatibilizers positively contribute to enhance the properties of the binary PLA/PC blends. Nevertheless, the results with MLO suggest this is an interesting biobased solution to provide increased toughness to PLA/PC blends.

In this work, we report the development and characterization of polylactide (PLA) blends with improved toughness by the addition of 10 wt.% lactic acid oligomers (OLA) and assess the feasibility of reactive extrusion (REX) and injection moulding to obtain high impact resistant injection moulded parts. To improve PLA/OLA interactions, two approaches are carried out. On the one hand, reactive extrusion of PLA/OLA with different dicumyl peroxide (DCP) concentrations is evaluated and, on the other hand, the effect of maleinized linseed oil (MLO) is studied. The effect of DCP and MLO content used in the reactive extrusion process is evaluated in terms of mechanical, thermal, dynamic mechanical, wetting and colour properties, as well as the morphology of the obtained materials. The impact strength of neat PLA (39.3 kJ/m2) was slightly improved up to 42.4 kJ/m2 with 10 wt.% OLA. Nevertheless, reactive extrusion with 0.3 phr DCP (parts by weight of DCP per 100 parts by weight of PLA–OLA base blend 90:10) led to a noticeable higher impact strength of 51.7 kJ/m2, while the reactive extrusion with 6 phr MLO gave an even higher impact strength of 59.5 kJ/m2, thus giving evidence of the feasibility of these two approaches to overcome the intrinsic brittleness of PLA. Therefore, despite MLO being able to provide the highest impact strength, reactive extrusion with DCP led to high transparency, which could be an interesting feature in food packaging, for example. In any case, these two approaches represent environmentally friendly strategies to improve PLA toughness.

This work addresses the potential of two biobased terpenoids, linalyl acetate and geranyl acetate, as environmentally friendly monomeric plasticizers for polylactide (PLA). Plasticized formulations of PLA containing 10 wt.% and 20 wt.% terpenoids were melt-compounded in a twin-screw co-rotating extruder and, subsequently, processed by injection moulding for further characterization. In addition, a reactive extrusion process (REX) was carried out on plasticized formulations containing 20 wt.% terpenoids with dicumyl peroxide to anchor the plasticizer molecules into the PLA backbone. Both terpenoids led to a remarkable plasticization effect on PLA, with a noticeable increase in ductile properties. In particular, the elongation at break of PLA, around 4.7%, was improved to values above 230% for all the plasticized formulations, even for low terpenoid concentration of 10 wt.%. Terpenoids also provide increased crystallinity because polymers chains have more mobility and are more readily arranged. This was observed by shifting the cold crystallization process to lower temperatures. As with other monomeric plasticizers, a clear decrease in the glass transition temperature from 61.5 °C (neat PLA), to values of around 40 °C for the plasticized formulations with 20 wt.% terpenoid was obtained. The obtained formulations show high potential since the plasticization efficiency of these terpenoids is very high, thus leading to new toughened-PLA formulations with improved ductility.