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.