Inner defects elimination and significant reinforcement of rice straw/high‐density polyethylene composites by extractives removal process

Abstract

The effects on the internal defects of the rice straw (RS)/high-density polyethylene (HDPE) composites are investigated by removing the extractives with cold water (CW), hot water (HW), and 1% alkaline (AL) solution. The characteristics of the RSs are measured by chemical composition, Fourier transform infrared, X-ray diffractometry, scanning electron microscopy, thermogravimetric analysis, and bulk density testing. The three extractive removal methods change the surface features of the RS and increase the interphase adhesion between the RS and the HDPE matrix. As a result, the inner defects of the RS/HDPE composites are eradicated and the die swell phenomenon disappear. The flexural modulus, flexural strength, and impact strength of the final composites increase by 95.59, 83.29, and 154.79% in the HW extraction method. The CW and the AL extraction also significantly improve the static mechanical properties of the obtained RS/HDPE composites.

Non-Isothermal Crystallization of Titanium-Dioxide-Incorporated Rice Straw Fiber/Poly(butylene succinate) Biocomposites

“…The tensile strength and tensile modulus of the RS/PBS composites increased by 16.03% and 306.06%, respectively, compared with the neat PBS. These results are similar to those of rice straw/high-density polyethylene composites and PBS/miscanthus fiber biocomposites [ 23 , 35 ].…”

“…This result was attributed to the removal of the extractives of rice straw fiber and the improvement of the interfacial interaction with the help of MA- g -PBS. Similar findings have been seen in rice straw fiber/HDPE composites [ 23 ], coir fiber/PBS composites [ 42 ], cotton stalk bast fibers/PBS composites [ 60 ], apple pomace/PBS composites [ 21 ], and grape pomace/PBS composites [ 61 ].…”

“…Removing the extractives of rice straw fibers results in a higher cellulose content and lower ash content. The altered chemical composition of rice straws could show different performances in the fiber-matrix adhesion [ 23 ].…”

Delignification and Densification as a Route to Enable the Use of Wheat Straw for Structural Materials

“…Therefore, there is a clear trend of increasing crystallinity index from the untreated material (Xc = 0.54) to the hot-water extracted (Xc = 0.62) and the mildly alkaline treated variant (Xc = 0.65). Similar results were obtained in other alkaline extractions with straw. ,, These chemical changes are highly favorable since a higher crystallinity in cellulosic materials is associated with a higher tensile strength of the single fibers …”

“…42 In the FTIR spectra of straw, these bands thus originate from lignin. 43,44,46 The spectra show a decrease in the intensity of these bands due to alkaline extraction, which can indicate the partial removal of lignin. A comparison of the alkaline treatments suggests that the severe treatment led to a higher extent of delignification than the mild variant.…”