原位聚合法制备可降解纤维基地膜及机理分析

为提高农作物秸秆综合利用率，通过原位聚合法，以水稻秸秆作为纤维原料制备陇上覆盖方式的功能型可降解地膜。结果表明，改性后，秸秆纤维基地膜的干抗张力等物理力学性能得到提高。X射线衍射结果显示，改性后秸秆纤维基地膜的相对结晶度从38.11%提升到64.42%，说明功能型助剂可渗透到纤维素的无定形区内，使无定形区的微纤丝向结晶区靠拢引起细胞壁纤维素微纤丝结晶区的宽度增加。改性后秸秆纤维基地膜的接触角从95.35°提高到121.03°，表明改性后地膜的抗水性能提高，能较好的适应户外陇上覆盖要求。TG结果表明，改性后地膜的热稳定性能得到提高。FTIR谱图显示改性剂中的功能性基团与地膜中的纤维结构发生了化学交联反应。XPS结果表明，改性后的秸秆纤维基地膜氧与碳的原子浓度比增加，说明改性剂与地膜纤维发生化学交联反应从而含氧官能团增加。SEM-EDXA结果表明改性剂较好的分布在秸秆纤维基地膜中，有利于纤维的交联。烟草覆盖试验表明，秸秆纤维基地膜提高了烟草种植整体水平。因此，功能型秸秆纤维基地膜能未来可应用于烟草、大蒜、西红柿和水稻等高经济附加值作物，为农作物秸秆综合利用提供新的方向。

Fabrication and mechanism analysis of degradable fiber membrane by in situ polymerization

Plastic films have been widely adopted to improve plant growth in agriculture, covering soil temperature, evaporation reduction, and water conservation in the soil. The most extensively-used materials are polyethylenes (PEs) for agricultural mulching applications, due to their excellent tensile strength and resistance to degradation, such as the low-density polyethylene (LDPE), linear low-density polyethylene (LLDPE), and copolymer poly (ethylene-vinyl acetate) (EVA). However, conventional film is made of polyethylene, leading to serious "White Pollution". Therefore, degradable materials can be expected to improve the polluted environment. Among them, crop straw can serve as the biggest renewable material with a variety of sources on the earth. Particularly, film mulching can be one of the most important approaches for the growth of crops. Normally, the degradable mulch film is commonly composed of biobased materials that rely on the biodegradable effects of sunlight (ultraviolet rays) and soil microorganisms. Furthermore, the biodegradable mulch film can be decomposed into carbon dioxide, water, and minerals, indicating a friendly environment. Moreover, the degradation rate of biodegradable films is influenced by the chemical components of the polymers. Crop straw can be obtained from corn, rice, wheat, sorghum, soybean, or sugar cane, indicating an abundant source of biomaterials. For instance, 700 million tons of various types of crop straw have been generated each year in China. Many attempts have been made to manufacture wood-based composites with agricultural residues, such as straw. Crop straw is an abundant agricultural residue with higher ash content, leading to the potential additional application as fodder. This study aims to improve the comprehensive utilization rate of crop straw. The straw film was made of rice straw by the in-situ polymerization, and tested as the ridge mulch for the crops. The results demonstrate that the mechanical properties of the straw fiber film were significantly enhanced by the modification. XRD results show that the crystallinity index of the modified film increased to 64.42% (raw film=38.11%). The enhancement in the crystallinity of the straw fiber film can be attributed to the functional additives, which penetrated into the amorphous region of cellulose. Microfibriles were obtained in the amorphous region, particularly close to the crystalline region, resulting in an increase in the width of the crystalline region of cell wall cellulose microfibril. The contact angle of the modified mulching film increased from 95.35° to 118.43°. Thermogravimetric (TG) analysis results indicated that the thermal stability of the modified film was improved after treatment. Moreover, the different chemical bonds in the unmodified and modified films revealed the chemical cross-linking between the film fibers and modifier after FTIR analysis. XPS analysis showed that there was an increase in the atomic concentration ratio of oxygen and carbon in the straw fiber base membrane after modification, indicating that the chemical cross-linking reaction between the modifier and the mulch fiber resulted in the increase of oxygen-containing functional groups. SEM-EDXA indicated that the modifier was uniformly dispersed in the fiber film, indicating an improvement in the mechanical properties. The experiment of tobacco mulch showed that the straw fiber base membrane improved the overall level of tobacco planting. Overall, the superior properties of the modified straw fiber film can make great potential for agricultural application.