Synergistic preparation of a straw fiber/polylactic acid composite with high toughness and strength through interfacial compatibility enhancement and elastomer toughening.

Plant fiber-reinforced polylactic acid (PLA) composites are extensively utilized in eco-friendly packaging, sports equipment, and various other applications due to their environmental benefits and cost-effectiveness. However, PLA suffers from brittleness and poor toughness, which restricts its use in scenarios demanding high toughness. To expand the application range of plant fiber-reinforced PLA-based composites and enhance their poor toughness, this study employed a two-step process involving wheat straw fiber (WF) to improve the interfacial compatibility between WF and PLA. Additionally, four elastomeric materials-poly (butylene adipate-co-terephthalate) (PBAT), poly (butylene succinate) (PBS), polycaprolactone (PCL), and polyhydroxyalkanoate (PHA)-were incorporated to achieve a mutual reactive interface enhancement and elastomeric toughening. The results demonstrated that Fe3+/TsWF/PLA/PBS exhibited a tensile strength, elongation at break, and impact strength of 34.01 MPa, 14.23 %, and 16.2 kJ/m2, respectively. These values represented a 2.4 %, 86.7 %, and 119 % increase compared to the unmodified composites. Scanning electron microscopy analysis revealed no fiber exposure in the cross-section, indicating excellent interfacial compatibility. Furthermore, X-ray diffraction and differential scanning calorimetry tests confirmed improvements in the crystalline properties of the composites. This work introduces a novel approach for preparing fiber-reinforced PLA-based composites with exceptional toughness and strength.

Synergistic modification of polylactic acid by oxidized straw fibers and degradable elastomers: A green composite with good strength and toughness.

Polylactic acid-based (PLA) composites are widely used in biomedicine, electrical components, food packaging and other fields, but their unsatisfactory mechanical properties such as high brittleness and poor toughness, cause problems in functional applications. This work developed a green and environmentally friendly strategy to improve PLA mechanical properties. Flexible polybutylene succinate (PBS) and alkaline hydrogen peroxide (AHP) treated straw fibers (SF) synergistically modified PLA. AHP is decomposed into a large amount of HOO-, which oxidizes the hydroxyl groups in SF to carboxyl groups to obtain oxidized straw fiber (OSF), which reacts with PLA in the molten state to form new ester bonds. The tensile strength of the OSF/PLA composite is 41.78 MPa, 38 % higher than the SF/PLA composite. The impact toughness of OSF/PBS/PLA composite is 14.47 KJ/m2 increased by 54 % after the adding PBS, while the tensile strength was also better than the control group. The synergistic action of PLA and PBS in OSF is attributed to the formation of new chemical bonds, efficient crystallization, and compatible interface. This study provides a new strategy to produce fiber-reinforced PLA composites with good toughness. It takes positive significance for developing degradable plastics with good performance and controllable cost.

Effect of silane coupling agent on compatibility interface and properties of wheat straw/polylactic acid composites.

To improve the performance of wheat straw/polylactic acid (WS/PLA) composites, four different silane coupling agents were used for constructing compatible interfaces and then examined by scanning electron microscopy, Fourier transform-infrared spectroscopy, X-ray diffractometry and thermogravimetric analysis. The blending and tensile strengths of silane-modified composites were effectively enhanced, with KH-570-modified composite exhibiting the best blending and tensile strengths. Water resistance analysis of silane-modified composites was reduced and contact angles larger, indicating that water resistance performance of this composite had been effectively improved. The KH-570-modified composite exhibited the best water resistance performance. Strain scanning showed that, in the linear viscoelastic region, the storage modulus (G') of modified composite was larger than that of unmodified composites. Frequency scanning showed that the G' and complex viscosity (η*) of modified composites were greater than those of unmodified composites. From strain analysis and frequency scanning, the modified performance of the silane agent was observed to effectively improve composite interfacial compatibility, with KH-570-modified composite exhibiting the best effect. XRD analysis showed that silane coupling agent modification improved the crystallinity of composites with the improvement of KH-570 the best. And the thermal stability of silane-modified composites was improved and the thermal stability of KH-570-modified composite the best.