聚酰胺-胺添加比例对超支化聚合物改性脲醛树脂的影响

将聚酰胺-胺作为改性剂添加至低摩尔比脲醛树脂(UF树脂)中,以提高低摩尔比UF树脂的固化速度,增强树脂的胶合强度。通过在UF树脂合成过程中添加不同比例的聚酰胺-胺,考察聚酰胺-胺对不同摩尔比UF树脂的影响,包括树脂性能和所制备板材的力学强度。结果表明:聚酰胺-胺添加比例为2%～3%时,UF树脂的固体含量增加、固化时间缩短、固化温度降低,并且这种优势在低摩尔比UF树脂中的改善效果更为显著。改性后的UF树脂制备板材的内结合强度增大,即使是摩尔比为1.1的UF树脂,所制板材的内结合强度也远大于国标要求。聚酰胺-胺改性UF树脂在固化特性和所制板材性能上的优异表现可以在保证板材力学性能的前提下明显提高板材生产效率,降低生产能耗,这种改性是非常有前途的。
In this study, the hyperbranched poly(amidoamine)s(PAMAMs)was used to modify urea formaldehyde(UF)resin with low molar ratio in order to accelerate the curing rate of the UF resin and reinforce its bonding performance. Different proportions of PAMAMs were added individually during the acid-stage of the UF resin synthesis. The basic properties of modified UF resin, such as viscosity, solid content, gel time and formaldehyde emission were evaluated according to GB/T 14074―2006 standard. The curing behavior of obtained UF resin was determined using dynamic mechanical analyzer(DMA)and differential scanning calorimetry(DSC). Particleboards were fabricated with modified UF resin in laboratory scale, and the dry internal bonding strength of prepared particleboard was investigated. The results showed that the solid content of UF resin increased and the curing temperature decreased with only small addition(2% to 3%)of PAMAMs. The acceleration of curing rate of modified UF resin was confirmed by DMA and DSC as well as the gel time measurement. The internal bonding strength of prepared particleboard was significantly increased by 45% when compared with the control sample. However, the addition of PAMAMs had no obvious effect on free formaldehyde emission of the particleboard. The ratio of PAMAMs to UF resin had significant effects on the solid content, curing time and temperature of UF resin. The internal bonding strength of prepared particleboard with modified UF resin with low PAMAMs to UF molar ratio met the requirement of the national standard. This result indicated that the modification of PAMAMs on UF resin can increase the efficiency and reduce the energy consumption of particleboard production without any decrease of the mechanical properties of the particleboard, which makes it a very promising method for UF resin modification