Control of Protective Coating Performance Aspects Through Manipulation of Polymer Fragility

液体涂层、在环境条件下应用的高性能防护涂层必须经过成膜，以提供连贯、附着力和功能性的涂层，以提供必要的性能。膜形成的速度和程度在工艺方面(涂层制品处理或储存的速度)和涂层性能(已开发的性能)方面都是最重要的。确保涂层具有可行的罐用期、在经济的时间范围内干燥以及涂层在投入使用时具有足够的性能是成功成膜的关键要素。双组分热固性环氧胺配方代表了大多数需要防腐或耐化学腐蚀的环境固化涂料技术。在常温固化条件下，聚合物粘结剂中的所有活性基团在玻璃化到玻璃态之前很少实现完全转化，在经过一段时间的扩散控制过程后，反应基本上停止。因此，涂层通常必须在欠固化状态下达到必要的性能。为了提高应用生产率和最终性能之间的理想平衡，需要更好地了解固化温度、反应基团的转化率、聚合物体系结构的选择和聚合物玻璃转变(Tg)对涂层性能的相互关系，以指导涂层配方的设计。聚合物玻璃脆性的概念与聚合物迁移率随温度变化的程度有关。“脆弱”体系是指聚合物迁移率在Tg附近有较大变化(伴随着较大的热容量变化)，而“强”体系具有较低的流动性(以及较低的热容量变化)。脆性量化了材料从液体转变为固体的速度，并与聚合物链段的填充效率有关，而聚合物链段的填充效率又被认为与各种关键性能标准(特别相关的是机械性能和分子扩散阻挡性能)相关。通过选择反应组分，控制聚合物的脆性可能为控制干燥过程和最终涂层性能标准提供一条途径。我们建议检验通过选择反应组分带来的聚合物结构来控制聚合物脆性的假说。本课程将探讨现代环氧胺涂料配方(包括叔胺促进剂)中主要环氧胺粘结剂组分和其他常见活性助剂的影响。利用模型配方，探索应用最先进的调制DSC方法来解释复杂的玻璃化转变区域。通过评估原料和相应的完全固化薄膜的热容变化，可以确定脆性的差异。红外线技术的应用将量化反应转化率，并允许探索聚合物结构、转化率和脆性之间的关系。将探索聚合物脆性对关键薄膜性能属性的影响。主要是干燥过程，也包括使用正电子湮没谱(PALS)或动态蒸汽吸附(DVS)的固化薄膜的透过膜扩散分子传输特性，以及使用动态机械分析(DMA)的聚合物薄膜老化过程。

Liquid applied, high performance protective coatings applied under ambient conditions must undergo film formation to deliver a coherent, adherent and functioning coating film to deliver the necessary performance. The rate and extent of film formation is of the highest importance both in terms of the process (how quickly a coated article can be handled or stored) and also in terms of coating performance (what properties have developed). Ensuring the coating has a workable pot-life, is dried in an economic timeframe and that coating performance is adequate when placed into service are vital components of successful film formation. Two component thermosetting epoxy-amine formulations represent the majority of ambient cured coating technology where corrosion protection or chemical resistance is required. Complete conversion of all reactive groups in the polymer binder is rarely achieved under ambient curing conditions before vitrification to the glassy state occurs and, following a period of diffusion controlled processes, reaction essentially stops. Consequently the coating must often achieve necessary performance in an under-cured state.In order to improve the desired balance of application productivity alongside final performance properties, greater understanding of the inter-relationships between cure temperature, extent of conversion of reactive groups, choice of polymer architecture and polymer glass transition (Tg) on coating film performance is required to guide design of coating formulations.The concept of polymer glass fragility is associated with the extent that polymer mobility changes with temperature close to Tg. "Fragile" systems are described as those that have large changes in polymer mobility close to Tg (accompanied by large heat capacity change) whereas "strong" systems have lower mobility (and lower change in heat capacity). Fragility quantifies how quick a material changes from liquid to solid and is related to polymer segment packing efficiency which, in turn, is believed correlated with various key performance criteria (of particular relevance is mechanical properties and molecular diffusion barrier properties). Through choice of reactive components, manipulation of polymer fragility may thus provide a route to manipulate both drying processes and final coating performance criteria.We propose to examine the hypothesis that polymer fragility can be manipulated through polymer architecture brought about through choice of reactive components. Influence of main epoxy-amine binder components and other common reactive additives used in modern epoxy-amine coating formulations including tertiary amine accelerators will be explored.Using model formulations, application of state-of-the-art Modulated DSC methodology will be explored to interpret complex glass transitions regions. Assessment of changes in heat capacity of starting materials and corresponding fully cured films will allow determination of differences in fragility. Application of Infra-Red techniques will quantify reaction conversion and allow relationships between polymer architecture, conversion and fragility to be explored.The implications of polymer fragility on key film performance attributes will be explored. Primarily drying processes, but also those associated with through-film diffusional molecular transport properties of cured films using Positron Annihilation Spectroscopy (PALS) or Dynamic Vapour Sorption (DVS) and polymer film aging processes using Dynamic Mechanical Analysis (DMA).