The extensive use of plastics in agriculture has increased the need for development and implementation of polymer materials that can degrade in soils under natural conditions. The biodegradation behavior in soil of polyhydroxyalkanoate (PHA) composites with 10 wt% distiller's dried grains with solubles (DDGS) was characterized and compared to pure PHA over 24 weeks. Injectionmolded samples were measured for degradation weight loss every 4 weeks, and the effects of degradation times on morphological, thermomechanical, and viscoelastic properties were evaluated by scanning electron microscopy (SEM), dynamic mechanical analysis (DMA), and small-amplitude oscillatory shear flow experiments. Incorporation of DDGS had a strong effect on biodegradation rate, mechanical properties, and production cost. Material weight loss increased linearly with increasing biodegradation time for both neat PHA and the PHA/DDGS 90/10 composites. Weight loss after 24 weeks was approximately six times greater for the PHA/DDGS 90/10 composites than for unaltered PHA under identical conditions. Rough surface morphology was observed in early biodegradation stages (≥8 weeks). With increasing biodegradation time, the composite surface eroded and was covered with well-defined pits that were evenly distributed, giving an areolate structure. Zero shear viscosity, T g , gelation temperature, and cold crystallization temperature of the composites decreased linearly with increasing biodegradation time. Addition of DDGS to PHA establishes mechanical and biodegradation properties that can be utilized in sustainable plastics designed to end their lifecycle as organic matter in soil. Our results provide information that will guide development of PHA composites that fulfill application requirements then degrade harmlessly in soil.
Tall oil‐based polyamide (PA) was blended with lignin‐cellulose fiber (LCF), an inexpensive, highly abundant byproduct of the pulp and paper industries, to produce environmental‐friendly thermoplastic biocomposites. The effects of the concentration of LCF on the thermal, rheological, and mechanical properties of the composites were studied using differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), thermogravimetric analysis (TGA), rheological testing, and mechanical testing. The morphologies of the composites were investigated using scanning electron microscopy (SEM). The incorporation of LCF did not change the glass relaxation process of the polyamide significantly. Results from rheological testing showed that the complex viscosity and shear storage modulus were increased by LCF. Both the modulus and strength increased with increasing LCF content; however, LCF substantially reduced the tensile elongation of the composites. The thermal stability of the composites was strongly influenced by the concentration of LCF. The onset of the degradation process shifted to lower temperatures with increasing LCF content. We conclude that LCF has strong potential for use as filler that is compatible with tall oil‐based polyamide. Adding LCF to form PA‐LCF composites can lower material costs, reduce material weight, and increase strength and rigidity compared to neat PA. Composites of PA‐LCF could serve as sustainable replacements for petroleum plastics in many industrial applications and would provide additional opportunities to utilize LCF, a highly abundant biorenewable material. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 42592.
In situ cationic polymerization of bio-based tung oil in the presence of poly(ε-caprolactone), a crystallizable, biodegradable, and biocompatible polymer, was performed to produce novel semiinterpenetrating polymer networks (IPNs). The macromolecular structure and properties of these IPNs were investigated as a function of composition using small amplitude oscillatory shear flow rheology, FT-IR spectroscopy, dynamic mechanical analysis (DMA), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and scanning electron microscopy (SEM). This versatile and low-cost strategy successfully produced bio-polymer blends with various degrees of miscibility, morphology, and crystallization behavior. The carbon-carbon double bonds in tung oil were consumed quickly after adding the cationic initiator to form a three-dimensional (3D) crosslinked network in all measured samples as confirmed by FT-IR. A complete miscible structure with a single glass transition temperature and onephase morphology was observed for a tung oil/PCL 90/10 blend. On the other hand, a two-phase structure exhibiting a nanoscale morphology of the dispersed minor phase as small as 100 nm was observed for blends with 20 and 30 wt% PCL. For a 50 wt% PCL blend, an interconnected, co-continuous microstructure of the two phases was also detected. DMA and DSC measurements confirmed the miscibility (or partial miscibility) of the blends by following the changes in the glass transitions of phases as a function of the composition. The value of the elastic modulus (E′) in the glassy state as obtained from the DMA measurements was strongly dependent on the composition, reaching a maximum at 20 wt% PCL.
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