Fe^(2+)/H_2O_2对脲醛树脂胶ζ电位及其稳定性的影响

Influences of Fe^(2+)/H_2O_2 on ζ Potential and Stability of Colloidal Urea-Formaldehyde Resins

采用胶体化学的方法对Fe2+/H2O2影响脲醛树脂(UF)胶ζ电位及其稳定性的因素进行了研究。结果表明,在pH=8.0时,脲醛树脂胶粒的ζ电位平均值约-32.5mV,粒子带负电,并以单分散形式存在。随着Fe2+离子或H2O2加入量的增加,脲醛树脂胶ζ电位的绝对值迅速减小,从而使胶粒间排斥势垒降低,胶粒发生聚集,体系粘度随之增大并最终产生凝胶。其中,Fe2+离子对脲醛树脂胶粒的ζ电位和粘度η变化的影响幅度比H2O2更为明显。pH值对胶体稳定性的影响主要表现在,pH值约为9时,体系具有最大的ζ电位,除此之外,pH值增大或减小ζ电位的绝对值均迅速减小,其中pH>9时ζ电位的绝对值下降幅度更为明显。采用胶体的双电层理论对Fe2+/H2O2影响脲醛树脂胶稳定性的机理进行了探讨。

The influences of Fe2＋/H2 O2 on the ζ potential and stability of colloidal urea-formaldehyde （UF） resins were studied by means of a colloidal chemistry method. The results show that the average ζ potential of urea-formaldehyde colloidal particles is about - 32.5 mV at a pH value of 8.0 and they exist in monodisperse state. The ζ potential is decreased rapidly with the addition of ferrous ions or hydrogen peroxide, which causes a decrease of expulsion potential, the aggregation of colloidal particles, an increase of viscosity and eventually the formation of stable UF resin gels. However, the influences of hydrogen peroxide on ζ potential and the viscosity ηof UF colloidal particles are much less than those of the ferrous ions. pH value plays an important role in keeping the stability of the colloidal particles. The system has the highest ζ potential at pH =9. When pH 〉 9, the absolute value of ζ potential decreases more significantly. The mechanism of Fe2＋/H2O2 affecting the stability of UF adhesive was discussed based on colloidal electric double layers theory.