Research On Modification Of Fly Ash Fibers And Enhancement Of Tensile Strength Of Paper Made From Fly Ash Fibers

Due to weak interaction between the fibers, the strength of paper made from fly ash fibers (FAFs) is low. In this paper, we have researched to improve the tensile strength of paper through the modification of FAFs to enhance the force between the FAFs.The silane coupling agent KH550 was used to pretreat FAFs, making the surface of FAFs with primary amine functional groups from KH550. Then acidic groups were introduced on the molecular chain of PVA by using chloroacetic acid or sulfuric acid to react with PVA which can adsorb on the surface of FAFs by the reaction of acidic groups and primary amino groups. Therefore, the tensile strength of paper was increased through hydrogen bonding produced by PVA enhancing the force between FAFs.Similarly, KH560 was used to modify the surface of FAFs, enhancing the adsorption of PVA on FAFs by the reaction of hydroxyl groups in PVA and epoxy groups in KH560. Then the tensile strength of paper was improved.IR spectra and SEM images illustrated thatFAFs were modified by silane coupling agent. Acid base titration and TG showed that adding the silane coupling agent and PVA solution into the pulp of FAFs resulted in the low conversion of fiber surface modification. The amount of silane coupling agent on the surface of FAFs was extremely fewer than the original amount, thus affecting the enhancement of the paper strength by PVA. While sprinkling the silane coupling agent on the FAFs to wet fibers directly and spraying PVA solution on the paper after papermaking would lead to the enhancement of paper strength significantly. The results of the tensile strength showed the tensile strength of paper was enhanced with the increasment of PVA amount. Silane coupling agents could promote the dispersion of FAFs in water, but limited contribution to improve the tensile strength of paper. The role of silane coupling agents was increased more PVA molecular chains to adsorb on FAFs, thereby enhancing the effect of PVA on the tensile strength of paper. In this study, the tensile strength of cellulose fiber paper was 1045N/m. While the amount of KH550 or KH560 was 15wt% of FAFs and the amount of acidific PVA or PVA was 5wt% of papermaking fibers, the tensile strength of paper adding "KH550-chloroacetic PVA", "KH550- sulfuric PVA" or "KH560-PVA" was 1132,1443 and 2363N/m respectively when the amount ratio of FAFs and cellulose fibers was 1:2. The tensile strength was 611,823 and 1208N/m respectively when the amount ratio was 2:1 in the same conditions. The sulfuric PVA (DS:20.54%) increasing the tensile strength of paper was higher than the chloroacetic PVA (DS:1.25%). The tensile strength of paper increased by "KH560-PVA" was higher than by "KH550-acidific PVA" in the same amount, but the drying temperature of paper was also high.