106 / 2021-10-29 20:05:33

Potential alternatives to plastics: preparation of lignin-cellulose composites with high strength and great water resistance

p-toluenesulfonic acid; Lignocellulose; Hot pressing; Composites; Plastic substitutes

Plastics are widely used around the world because of their high specific strength, light weight and malleability. However, plastic products are difficult to recycle in most areas and are almost not completely degradable. The use of a large number of single-use plastic products has led to the accumulation of plastic particles in the food chain, posing a great threat to the environment and human health, and a great ecological and environmental burden. In order to solve this problem, it has become a global trend to ban the use of single-use plastic products. The development of alternatives to single-use plastic products has become an urgent issue. However, the current commercial biodegradable alternatives are not as satisfactory as they could be due to the disadvantages of poor natural degradability, high cost, low mechanical properties and poor water stability. Cellulose-based materials have the advantages of biodegradability, abundant stock, and low material cost, but its disadvantages such as poor water stability and low mechanical strength hinder its replacement of plastic products. Inspired by the properties of natural wood, lignin was used to enhance the strength and water resistance of bagasse cellulose materials and develop an alternative material made of plastic. In order to avoid the disadvantages of lignin layering and uneven distribution of lignin in current commercial lignocellulosic materials, this study preserved about 30% of lignin and 35% of hemicellulose by pretreatment with p-toluene sulfonic acid. After grinding and pumping into a film, the lignin-containing cellulose film was mechanically hot-pressed (at the condition of 5 MPa, 150℃ and 48 h, respectively). The lignin was gradually penetrated into the cellulose skeleton as a reinforcing and waterproofing agent. The lignin-cellulose composite was obtained. The composite has excellent isotropic tensile strength (32 MPa to 146 MPa for the original bagasse paper) and great hydrophobic properties (108° water contact angle, 92° after 30 min). Furthermore, the addition of lignin allows the cellulose material to possess excellent thermal stability and UV resistance (98% UVC and 99% UVB). This work reveals the conversion of agricultural waste into purely natural lignin-cellulose composites with biodegradability and eco-friendliness, promising as a potential alternative to plastic products.