The word ‘chock’ is used to describe materials used in the marine industry to seat machinery in ships. To ensure that the machine fulfils its function, precise alignment and a stable base are critical. Using a chock to provide this intermediary support is easier than attempting to match the machine base with the ship directly.
Since the 1960’s, epoxy resins have been the material of choice for marine chocking. Their pourable nature allows for in-situ preparation, which eliminates the previously laborious process of hand fitting metallic chocks.
Prior to installation, epoxy resin chocks must be approved by a marine classification society. The aim of the approval is to ensure that the material is fit for use in industry. Properties such as cure shrinkage, compressive strength and compressive creep (amongst others) are all assessed.
In collaboration with Swansea University, R-TECH Materials conducted a research project focused on the compressive creep properties of marine chocking materials. Given the range of possible working stresses and post-cure temperatures that in-service epoxy resin chocks may experience, an investigation was conducted to investigate whether thermal analysis techniques could be used to predict compressive creep performance.
Two thermal analysis techniques – DSC (differential scanning calorimetry) and DMA (dynamic mechanical analysis) were used to investigate cure and viscoelastic properties of two different marine chocking resins. A positive correlation was found between compressive creep behaviour and percentage cure. This correlation is a useful tool in determining ‘how cured’ a resin must be to pass the requirements for the compressive creep test. In addition, results from DMA generated interesting findings relating to the storage of material before testing. This information has been used to develop the methodology of the compressive creep test.
The outcomes of the research were shared in Cologne at the beginning of April, at the Polymer Analysis and Testing 2017 conference.