硅酸钠表面施胶改善纸张防水性能的机理探讨

分别利用硅酸钠、硅酸钠与淀粉复配进行纸张表面施胶,表面施胶体系中有机硅油用量控制为3%(相对于硅酸钠绝干质量);探讨了施胶量和施胶体系对纸张孔隙率、纸张平均孔径、表面平滑度、Cobb30值和表面接触角的影响;依据毛细管现象公式,探讨及分析了表面施胶纸张的防水机理;利用扫描电镜(SEM)观察分析了表面施胶纸张的表面形貌。结果表明,硅酸钠-淀粉复配体系中,淀粉最佳用量为33%;随着表面施胶体系施胶量的增加,表面施胶纸张的孔隙率和平均孔径均下降;经硅酸钠和硅酸钠-淀粉复配表面施胶后,纸张的表面接触角较原纸大幅提高且硅酸钠-淀粉复配体系对纸张抗水性的改善效果优于硅酸钠。此外,研究还发现,纸张平均孔径的降低、表面接触角的增加及胶层在纸张表面的覆盖是硅酸盐及其复配体系表面施胶纸张产生抗水性的主要原因。

Discussion on the Mechanism of Improving Waterproof Property of Paper by Surface Sizing of Sodium Silicate

Sodium silicate,sodium silicate and starch mixture were respectively used for paper surface sizing in this study.The paper porosity,aperture,surface smoothness,Cobb30,and contact angle were used to characterize the paper’s porous structure and surface wettability after surface sizing,and according to the capillary phenomenon formula,the paper waterproof mechanism was discussed and analyzed.The structure and morphology of paper surface after surface sizing were also analyzed by SEM.The results showed that the optimal dosage of starch in sodium silicate-starch compound was 33%.With the increment of surface sizing,the porosity and average aperture of surface-sized paper decreased,and the contact angles of surface-sized papers were greater compared with the base paper,and the sodium silicate-starch performed better than the sodium silicate in improving water resistance of paper.In addition,the study also found that reduction of average aperture,increase of the surface contact angle,and the glue film produced by surface sizing in/on the paper are main reasons for water resistance of paper sized with sodium silicate and sodium silicate-starch compound.