Optimization of the parameters for the preparation of straw fiber raw material by biological pretreatment and synergistic expansion blasting

Mulching as a traditional field management technique, boasts the benefits of improving soil ecology and maintaining soil temperature and moisture. The biodegradable plant fiber mulch produced from crop straw boasts abundant raw material sources and has similar temperature and moisture retention effects to plastic mulch, which would have no phenomenon of soil hardening, and compromised crop cultivation and sowing quality. The quality of straw fiber obtained through physical methods cannot meet the demand of mulch film. To improve the mechanical properties of straw fiber mulch film and reduce pulping time, this study introduces a method of preparing straw fiber mulch raw materials through biological pretreatment combined with extrusion-explosion. To explore the optimal combination of process parameters for this technology, three-factor and five-level quadratic orthogonal central composite rotatable design experimental approach was employed, with pretreatment time, spindle speed, and Clearance of mould head selected as the experimental factors, and tensile index, pulping time, and fiber aspect ratio as performance indicators. The results showed that pretreatment time and spindle speed, spindle speed and clearance of mould head had very significant effects on the tensile index (P<0.01). Pretreatment time and clearance of mould head have significant effect on tensile index (P<0.05). Pretreatment time and spindle speed, pretreatment time and clearance of mould head have significant effect on pulping time (P<0.05). Spindle speed and pretreatment time had very significant effect (P<0.01) on pulping time, the spindle speed and clearance of mould head has no significant effect on fiber aspect ratio (P>0.05). Pretreatment time and spindle speed have very significant effect on fiber aspect ratio (P<0.01). Pretreatment time and clearance of mould head have significant effect on fiber aspect ratio (P<0.05). The optimal combination of process parameters was determined to be 10 days of pretreatment, a spindle speed of 120 r/min, and a Clearance of mould head of 3 mm. The resulting fiber mulch exhibited a tensile index of 9.57 N·m/g, a pulping time of 81.4 minutes, and a fiber aspect ratio of 10.97, with a relative error not exceeding 5% compared to the theoretical optimal values. The rice straw fiber-based mulch prepared under these conditions meets the technical requirements for crop cultivation in both irrigated and dry fields. This study provides a basis and technical support for the production of fully biodegradable plant fiber mulch film from rice straw.