A hydrolytic degradation study of two bio-based polyesters, poly(trimethylene malonate) (PTM) and poly(trimethylene itaconate) (PTI) with bimodal molecular weight distribution, was performed in aqueous solutions adjusted to pH values from ~5.5 to 11. Final weight loss varied from 20 to 37 wt% for PTM and from 7 to 21 wt% for PTI as a function of degradation time and initial solution pH. Fourier transform infrared (FTIR) spectroscopy was used to monitor ester bond concentration of these bioplastics, and the molecular weights and polydispersity index were obtained by gel-permeation chromatography (GPC). Solutions with lower initial pH values resulted in lower molecular weights for both PTM and PTI after one week of degradation.Degradation especially affected the amorphous region, leading to an increase in crystallinity of PTI samples.
The aim of this work was to enhance poly(lactic acid)'s (PLA) flexibility and ductility by blending it with another bioplastic. Poly(trimethylene malonate) (PTM), developed as part of this study, was synthesized from 1,3-propane diol and malonic acid via melt polycondensation. Blend films of PLA and PTM were prepared by solvent casting from chloroform. Differential scanning calorimetry and thermogravimetric analysis were used to show shifted phase transitions and a single glass-transition temperature, indicating miscibility of PTM in the blend films. Morphology and mechanical characterizations of the PLA/PTM blend films were performed by atomic force microscopy using a quantitative nanomechanical property mapping mode, tensile testing, and scanning electron microscopy. Miscible blends exhibited Young's modulus and elongation at break values that can significantly extend the usefulness of PLA in commercial applications. The blending of PTM with PLA resulted in films with a 27-fold increase in toughness compared with neat PLA film.
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