Thermal and mechanical properties of polyethylene glycol (PEG)-modified lignin/polylactic acid (PLA) biocomposites.

In this study, a method was proposed to prepare biocomposites from polylactic acid (PLA) and polyethylene glycol (PEG)-modified lignin using twin-screw extrusion process. The structure of PEG-modified lignin was studied by Fourier transform infrared spectroscopy (FTIR) and gel permeation chromatographic (GPC) analysis. The effects of different contents of soda lignin and PEG-modified lignin on PLA composites were studied by tensile test, differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), scanning electron microscopy (SEM), dynamic mechanical analysis (DMA) and degradation analysis. The experimental results showed that the addition of PEG-modified lignin enhanced the heat resistance of PLA composite. PLA could be combined with up to 30 % PEG-modified lignin, with no significant reduction in tensile strength properties. Compared with PLA-L30, the tensile stress and elongation at break of PLA-PL30 were increased by 26.4 % and 78.9 %, respectively. This approach provided a new way to produce high-performance lignin based-PLA composites and had certain industrial application value.

Polypropylene Blend with Polyphenols through Dynamic Vulcanization: Mechanical, Rheological, Crystalline, Thermal, and UV Protective Property.

Tannin and lignin were blended with polypropylene (PP) through dynamic vulcanization technique. Their influence of mechanical property, crystallinity, thermal stability, as well as ultraviolet (UV) protection property on the PP matrix was investigated and compared with native tannin and lignin. According to our experimental results, tannin and lignin undergo dynamic vulcanization and were more compatible with the PP matrix. Besides, tannin and vulcanized tannin can perform as nucleating agents of PP because of their relatively small particle size. Moreover, vulcanized tannin/lignin have a better performance on the thermal stability of PP compared with native tannin/lignin, especially PP/vulcanized lignin blend. Furthermore, vulcanized tannin/lignin present better UV protective performance, concluded from fewer changes on surface morphology, carbonyl index, crystallinity, viscosity, and tensile property.

Dynamically Cross-Linked Tannin as a Reinforcement of Polypropylene and UV Protection Properties.

Tannins were used as reinforcing components for polypropylene with anti-UV properties via dynamic curing extrusion. The influence of cross-linked tannins in different weight fraction and their anti-UV capacity on morphological, mechanical, rheological, crystallize and thermal properties were studied. The experimental results indicated that the cross-linked tannins improve Young's modulus, crystallinity, and thermal stability and reinforce the internal network of polypropylene. After UV accelerated weathering, polypropylene had fewer surface cracks, lower carbonyl index, fewer crystallinity decreases and less mechanical properties loss with increasing tannin content.