Improving the Toughness and Thermal Resistance of Polyoxymethylene/Poly(lactic acid) Blends: Evaluation of Structure-Properties Correlation for Reactive Processing.

Jacek Andrzejewski,Arkadiusz Kloziński,Katarzyna Skórczewska

doi:10.3390/polym12020307

Abstract

The study focuses on the development of polyoxymethylene (POM)/poly(lactic acid) (PLA) blends with increased impact and thermal resistance. The study was conducted in two phases; in the first part, a series of unmodified blends with PLA content of 25, 50, and 75 wt.% was prepared, while the second part focused on the modification of the PLA/POM (50/50) blends. An ethylene/butyl acrylate/glycidyl methacrylate terpolymer (E/BA/GMA) elastomer (EBA) was used to improve the impact strength of the prepared blends, while reactive blending was used to improve interfacial interactions. We used a multifunctional epoxy chain extender (CE) as the compatibilizer. Static tensile tests and notched Izod measurement were used to evaluate the mechanical performance of the prepared samples. The thermomechanical properties were investigated using dynamic mechanical thermal analysis (DMTA) analysis and heat deflection temperature (HDT)/Vicat softening temperature (VST) methods. The crystallinity was measured using differential scanning calorimetry (DSC) and wide-angle X-ray diffraction (WAXS) measurements, while the rheology was evaluated using a rotational rheometer. The paper also includes a structure analysis performed using the SEM method. The structural tests show partial miscibility of the POM/PLA systems, resulting in the perfect compatibility of both phases. The impact properties of the final blends modified by the EBA/CE system were found to be similar to pure POM resin, while the E modulus was visibly improved. Favorable changes were also noticeable in the case of the thermomechanical properties. The results of most of the conducted measurements and microscopic observations confirm the high efficiency of the reaction for PLA as well as for the modified POM/PLA mixtures.

Highlights

The use of a polymer mixture based on poly(lactic acid) (PLA) has been one of the dominant trends in the modification of biopolymers and biocomposites over the last few years
The second polymer used for the preparation of the blends was the poly(lactic acid) Ingeo 3251D produced by Nature Works (Minnetonka, MN, USA); this PLA is a biopolymer made of renewable raw materials for which the manufacturing process is based on the polymerization of lactic acid fermented sugars obtained from plants
Blend, the pure andincreased the pure trend was for the for annealed samples; duePOM, to the crystallinity level the initial values of the tensile modulus for the POM/PLA blend, the pure POM, PLA

Summary

Introduction

The use of a polymer mixture based on poly(lactic acid) (PLA) has been one of the dominant trends in the modification of biopolymers and biocomposites over the last few years. The first one is the need to facilitate or accelerate the biodegradation process of PLA. This issue is a significant problem in the packaging industry, where biopolymers are expected to have a simple and rapid decomposition process, most preferably under composting conditions. This polymer normally requires composting under industrial conditions at a temperature of about 80◦ C

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