Effects of different pretreatments on compression molding of wheat straw and mechanism analysis

This study investigated effects of various pretreatments on characteristics of compression molded wheat straw and molding energy consumption. And correlative mechanism was explored. Pretreatments included natural air drying, vacuum sealing, 4% ammonium hydroxide + vacuum sealing. Hemicellulose and lignin contents and crystallinity decreased following pretreatments, while surface porosities increased. Cellulose and ash levels and lower heat value were not significantly affected (P > .05), while water resistance decreased and relax density and fall strength satisfied relevant standards. Ignition index and comprehensive combustibility index of samples treated with 4% ammonium hydroxide + vacuum sealing were the greatest, and molding energy consumption was also the lowest. Optimal pretreatment time was 21 days. Mechanism analysis indicated that crystallinity affected water resistance, lignin affected combustion characteristics and hemicellulose affected molding energy consumption to the greatest extent. Overall, 4% ammonium hydroxide + vacuum sealing pretreatment had the most beneficial effect on compression molding and resulted in the lowest energy consumption.