by 2019 Abstracts No Comments

This is the first of a series of three papers on the science of calcium carbonate in adhesives and sealants. The subsequent publications will tackle the fundamentals of rheological modification and mechanical reinforcement.

Calcium carbonates are the most used filler in adhesives and sealants. While coarse products (extenders) are essentially aimed at cost reduction, fine and treated products (functional fillers) offer added functionalities such as mechanical reinforcement and rheological modification.

When micrometric and submicrometric products are used in moisture-curing and moisture-sensitive systems, the amount of water carried into the systems by the functional fillers needs to be taken into consideration. To prevent variability of the product quality and performance of the adhesives and sealants, costly corrective measures are required, including: filler pre-drying, long mixing times under vacuum, heating/cooling and chemical drying.

Given the economical and operational relevance of moisture in calcium carbonate fillers, it is important for the formulator and the production engineer to understand the root cause of the problem. This paper will describe the fundamental behaviour of calcium carbonate in relation to environmental humidity. We first describe the mechanism using model systems and then expand to interpret real-world production conditions. The fundamentals of surface treatment, a common mitigation technology, will be presented. We will then outline advanced process and material engineering solutions. Finally, we will give an overview of the industrial relevance of the phenomena, supported by a separate set of case studies.

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