This study focuses on creating an optimal grafting compatibilizer for blends of polypropylene carbonate (PPC) and polybutylene succinate (PBS). PPC and PBS were blended separately with different amounts of maleic anhydride (MAH) and with and without dicumyl peroxide (DCP) to aid the free-radical grafting. Titration analysis evidenced that MAH reacted with the polymers terminal groups and backbones using free-radical functionalization. Thermogravimetric analysis (TGA) and gas permeation chromatography (GPC) results demonstrated how the thermal stability of PPC improves with the addition of MAH. Proton NMR proved that, in both PPC and PBS formulations, ring-opening reactions and grafting of the intact MAH ring occur, as well as interchain grafting producing network structures. The rheological analysis showed that small quantities of MAH and DCP increase the viscosity of the resins. The compatibilizer that was determined to be most reactive and stable of all the formulations analyzed was PPC with 2% MAH and DCP and its effect in the morphology of PPC-PBS blends was proven successful by a reduction of the PPC droplet size.

The free radical functionalization of immiscible blends of polybutylene succinate (PBS) and polypropylene carbonate (PPC) was successfully achieved on a novel quad screw extruder. A premade compatibilizer, PPC-grafted-maleic anhydride (gPPC), was added in various amounts to trigger the chemical compatibilization and tailor the properties of the final blend. Titration of acid groups on the functionalized blends showed that the grafting efficiency increases with the addition of gPPC. Proton NMR corroborated the formation of new graft copolymers in the reactive blends. A change in the rheological behavior of the formulations evidenced the grafting reactions occurring at the interphase of the components. Also, gPPC suppressed droplet coalescence as seen in the SEM images. Finally, the addition of compatibilizer increased the tensile strain at break by more than 100%, improved up to 50% the impact resistance, and produced a small increase on flexural and elastic modulus.

This work studies, for the first time, the influence of specific mechanical energy (SME) on the reaction efficiency and blend's performance during reactive extrusion of biopolymer compounds. Poly(lactic acid) (PLA) and poly-(butylene succinate) (PBS) were compounded separately with poly(propylene carbonate) (PPC) and a premade maleic anhydride (MAH) compatibilizer to achieve functionalization. Different screw speeds (reaching 1000 rpm) and flow rates were tested. Results indicated that the grafting efficiency was directly proportional to the SME imparted in the system. The PBS blends compounded at shorter times and faster speeds experienced less degradation and better mechanical properties than blends compounded at longer times. The effect was similar but less pronounced for the PLA formulations. It is possible to optimize the reactive compatibilization of biopolymer blends by means of SME calculations and that better blend performance is achieved when conducting high-speed extrusion at short residence times.

Poly(propylene carbonate) (PPC) is a promising new sustainable polymer produced from carbon dioxide. PPC has inferior thermal stability which could be enhanced by synergistic blending with other polymers. Blends of PPC and the engineering thermoplastic polyoxymethylene are produced by melt compounding in various weight ratios. The compatibility of the blends is investigated using thermogravimetric analysis (TGA), differential scanning calorimetry, Fourier transform infrared spectroscopy (FTIR), density measurements, and scanning electron microscopy (SEM). TGA reveals that thermal stability of the blends increases dramatically in comparison to the neat PPC. A small shift in the glass transition temperature demonstrates the immiscibility of the blends but also indicates some compatibility, attributed to potential dipole–dipole interactions which are also corroborated with the FTIR results. A deviation of the rule of mixtures for density is found for some of the blends. SEM analysis of the blends shows two phase morphology; however, the interfacial adhesion appeared to be enhanced with increasing PPC content. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018, 135, 45823.

This work studies two functionalization routes during high-speed reactive extrusion of biobased and biodegradable polymer blends: exchange reactions and free radical grafting with maleic anhydride.