The aging of polyacrylate latex films (PLF) in simulating acid rain is complicated, involving crosslink, degradation and etching. This paper focused on the aging mechanism of PLF in simulation acid rain on molecular scale through studying the change of the free volume by positron lifetime spectrum. Via examining the variations of weight, gel content, absorption of water and the microstructure of PLF with ageing time in simulating of environment, it is found that the dominating mechanism of PLF aging in acid rain has three stages: crosslinking first, followed by degradation and erosion finally.
