Infection Behavior During Ageing of Polymers: A Review

When polymers are in blends or used together, the ageing process of polymer components or polymers affects each other, which is called infection behavior of ageing. Due to the infection behavior during ageing of polymer, the research results of an individual polymer cannot be used to predict the life of this polymer material in blends or being used with other polymers. Therefore, infection behavior is an important topic in the field of ageing study. This article mainly features the research progress towards infection behavior of polymer ageing. Firstly, the "contacting" and "non-contacting" behaviors are emphatically illustrated, which are the two typical patterns of infection behavior of ageing. Ageing spreads via infection agents within a polymer or polymer blend, and between different polymers separated from each other. Infection agents play an important role in infection behavior. Then, the source and effects of infection agents are analyzed. Infection agents include radicals, volatile organic small molecules, gases, volatile additives and so on. All these infection agents work in "contacting" behavior, while volatile and gaseous matter are more important in "non-contacting" behavior. Benzoyl peroxide (BPO), formaldehyde and acetic acid are found to accelerate the thermo-oxidative ageing of polypropylene (PP). Eighteen volatile organic small molecules including acids, esters, aldehydes, ketones and alcohols are demonstrated to accelerate the photo-oxidative ageing of PP to different extents. Finally, the applications of infection behavior in the field of environmental protection and heritage protection are introduced and the challenges and prospects are proposed. The characterization of infection agents and their mechanism of action remain to be clarified systematically.