coating developments | Polyethylene
Figure 1: Illustrative thickness models of SureBond compared to 3LPE and DFBE coating systems
Figure 2: The in-line curing oven where the SureBond 100 curing process is initiated
Process development Bredero Shaw’s research scientists were presented with a mandate based on this customer feedback and allocated over two years to develop and evaluate the optimal formulation platform that would meet clients’ needs. The research team fi nally settled on a polyolefi n matrix (primarily PE) with a novel and patented molecular design which gives SureBond performance similar to typical 3LPE systems yet does not require the often problematic adhesive interlayer. The coating construction is shown in Figure 1. This novel approach is based on a tightly controlled set of chemical reactions that take place between the topcoat and the non-fully cured FBE substrate during application. The result is a fully fused, chemically bonded system with exceptional performance. The functionalised PE blend results in a topcoat that exceeds 3LPE performance requirements due to creation of a
tough secondary network in the polymer while offering an improved cutback substrate for fi eld joint application. The next stage in the development process was to
scale the laboratory formulation to an industrial solution ready for the factory fl oor. This additional twelve month programme pulled in Bredero Shaw’s extensive plant network, global engineering expertise and material science expertise to ensure a reliable coating solution that meets stringent and proven capability require- ments. Multiple trials were held at several manufactur- ing facilities to bring together fundamental knowledge and operational expertise within a cross-functional initiative designed to compress time-to-market. As part of this programme, new plant equipment had to be designed to accommodate the nature of the topcoat, which reacts with a non-gelled FBE substrate, without impacting on plant accreditation or line speed perfor- mance. Figure 2 shows an inline curing oven developed as part of the industrialisation process.
Performance benefi ts Over the course of these process trials samples were sent to globally recognised testing labs across several geographies to independently validate the enhanced performance observed during the research stage. The results showed that the engineered formulation comfortably exceeded specifi cations such as ISO21809- 1. The SureBond coating has excellent barrier proper- ties, which minimises the diffusion of corroding species such as oxygen and water to the coating/steel interface. Consequently, adhesion to the steel is very stable in service environments. The system shows excellent performance in 28 day cathodic disbondment tests at up to 95°C compared to equivalent systems, working synergistically with cathodic protection systems to
18 PIPELINE COATING | May 2014
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