Failure and Damage Analysis of a Polymeric Finish Topcoat on Vinyl Coated Fabrics for Marine Applications

During the standard development process of a new vinyl coated fabric for the marine sector, all materials are thoroughly tested and exposed to harsh environmental conditions to confirm they meet the requirements of this segment. Through this process, a vinyl product exhibiting significant topcoat layer delamination was identified. To investigate the root cause of this failure, a factorial experimental design with 16 samples involving four key components of the vinyl coated fabric as factors (nature of basecoat, plasticizer type, plasticizer concentration, number of lacquer’s layers) was conducted. All the different constructions were evaluated through contact angle measurements and the identification of the plasticizer extraction profile. Furthermore, the different constructions were exposed to weathering conditions (thermal, salt fog, UV exposure) and analyzed by scanning electron microscopy (SEM) for detecting any possible integrity damage in the coating system. The finishing layers—basecoat and topcoat—were also individually studied by infrared spectroscopy, thermal gravimetric analysis, differential scanning calorimetry, and gel permeation chromatography to expedite identifying any possible change in their thermal behavior and chemical structure. As result of this exhaustive analysis, it was confirmed that one of the sample test groups (samples 9–16), which included one of the basecoat formulations (basecoat 2) in the vinyl coated fabric construction, displayed a lower UV resistance due to severe polymer degradation when compared to the alternative test group assembled with a different basecoat (basecoat 1) during the UV exposure test. In addition, a decrease of at least 45% in the surface free energy polar component (γsp) ascribed to a reduction from 100 phr (parts per hundred resin) to 80 phr in the plasticizer content was also identified for vinyl coated fabric samples containing basecoat 2. This finding allowed us to identify a strong correlation of the surface energy for basecoat 2 with the plasticization level of the PVC and explained the early delamination observed for the topcoat after thermally induced plasticizer migration, which was confirmed by SEM analysis. This analysis methodology not only promoted the identification of the failure root cause but also guided the choice of the most UV resistant and stable basecoat formulation to be included in future vinyl coated fabric constructions for marine upholstery applications.