Biochar filled into plant fibers can be used to manufacture black ground films,which have the benefits of reducing light transmission to inhibit weed growth,while also decreasing thermal radiation to help retain moisture.However,the addition of biochar leads to low alkyl ketene dimmer(AKD)sizing efficiency and reduced material mechanical properties.This study proposed a process to improve the AKD sizing efficiency using cationic starch(CS)and cationic polyacrylamide(CPAM)as wet-end additives.The adsorption experiment indicated that the main adsorption mechanism of addi-tives by biochar was chemical adsorption on the monolayer.The effect of sizing efficiency was significantly improved when AKD content was 0.6 wt%,with a sizing degree of 37.77 s.The optimal content of cationic starch was 1.0 wt%,which increased the sizing degree by 57.51%,dry tensile strength by 35.10%,tearing strength by 32.94%,and bursting strength by 18.56%.The optimal content of cationic polyacrylamide was 0.1 wt%,which increased the sizing degree by 55.65%,dry tensile strength by 29.23%,tearing strength by 22.94%,and bursting strength by 25.98%.The the addition of filler under the optimal additives content would have a negative impact on the AKD sizing efficiency and mechanical properties.Cationic starch encapsulated the AKD particles and then the cationic poly-acrylamide bridged the AKD particles and the fibers through asymmetric bridging.Compared to the conventional sizing process,the sizing degree of the composite was increased by 25.04%,dry tensile strength by 12.54%,tearing strength by 10.35%,and bursting strength by 15.74%.This study provided an improvement method for the sizing process of high-loaded porous materials.
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