Impact of model contaminants on surface active marine coating addtives

Marine coatings are often based on silicone resins, with further additives to inhibit biofouling or enable release of adhered species. The efficiency of additives decreases with time and particularly with exposure to common contaminants, such as oils. We have started to explore this for model PDMS/additive systems by studying changes in surface property via dynamic contact angle. These experiments reveal dramatic changes in surface property upon exposure to hydrocarbon oil and we propose to use NR on simplified models to elucidate the molecular origins of this change in surface property. We postulate that alkane contaminants may promote surfactant leaching from PDMS film either by swelling the matrix (osmotic stress) or by compatibilising the additive, enabling it to diffuse out more easily. NR experiments will isolate these effects, so helping to formulate better marine coatings.

船舶涂料通常以硅树脂为基材，辅以各类添加剂以实现抑制生物污损或促进附着物种脱离的功能。添加剂的效能会随时间推移逐渐下降，尤其在暴露于油类等常见污染物时。我们已针对聚二甲基硅氧烷（Polydimethylsiloxane, PDMS）与添加剂构成的模型体系，通过动态接触角（dynamic contact angle）表征表面性质变化，开展了相关探索。实验结果显示，暴露于烃类油品后，样品表面性质会发生显著变化；我们计划在简化模型体系中借助NR（Neutron Reflectometry）阐明该表面性质变化的分子起源。我们假设，烷烃污染物可通过两种途径促进PDMS薄膜中的表面活性剂浸出：一是溶胀基体（渗透胁迫），二是对添加剂起到增容作用，使其更易扩散逸出。NR实验可分离这两种作用机制，从而助力开发性能更优异的船舶涂料。