title: Role of the excess monomer in the growth of urea and formaldehyde resin deposit particles.
abstract: The role of excess monomer (i.e., Urea (U) or Formaldehyde (F)) in UF precipitation reaction was investigated at 28°C. The maximum output of the UF resin deposit was found around the U:F molar ratio 1.0:1.0 and this output decreased if excessive urea (or formaldehyde) was used in the reaction system. The excess monomer was considered to decrease the polymerization degree of UF resin deposit and increased the bonding saturation of its copolymerization monomer as well as the solubility of the UF resin deposit. The Influence of the excess monomer on the lamellar crystallinity of the resultant deposit, involving the polymerization degree and bonding saturation of the monomer, was examined. Three different dynamic regions containing excess monomers were revealed according to the behaviors of the deposit nucleation. The density and water absorption of the UF resin particles were finally demonstrated relative to the dynamic regions in their nucleation reactions.
authors: Department of Chemistry, Tongji University, Siping Road 1239, Shanghai 200092, China. Electronic address: haozhixian@tongji.edu.cn.
authors: Zhixian
authors: Z
authors: Hao
authors: Department of Chemistry, Tongji University, Siping Road 1239, Shanghai 200092, China.
authors: Yuqing
authors: Y
authors: Guo
authors: Department of Chemistry, Tongji University, Siping Road 1239, Shanghai 200092, China.
authors: Mulati
authors: M
authors: Mansuer
authors: Department of Chemistry, Tongji University, Siping Road 1239, Shanghai 200092, China.
authors: Junfu
authors: J
authors: Zhu
authors: Department of Chemistry, Tongji University, Siping Road 1239, Shanghai 200092, China.
authors: Zhirong
authors: Z
authors: Zhu
keywords: Excess monomer; Lamellar crystallinity; Nucleation reaction; UF resin microsphere; Water absorption