Sensitive methods for studying the environmental performance of protective coatings

The safe working lifetime of a structure in a corrosive or other harsh environment is frequently not limited by the material itself but rather by the integrity of the coating material. Advanced surface coatings are usually crosslinked organic polymers such as epoxies and polyurethanes which must not shrink, crack or degrade when exposed to environmental extremes. While standard test methods for environmental durability of coatings have been devised, the tests are structured more towards determining the end of life rather than in anticipation of degradation. We have been developing prognostic tools to anticipate coating failure by using a fundamental understanding of their degradation behaviour which, depending on the polymer structure, is mediated through hydrolytic or oxidation processes. Fourier transform infrared spectroscopy (FTIR) is a widely-used laboratory technique for the analysis of polymer degradation and with the development of portable FTIR spectrometers, new opportunities have arisen to measure polymer degradation non-destructively in the field. For IR reflectance sampling, both diffuse (scattered) and specular (direct) reflections can occur. The complexity in these spectra has provided interesting opportunities to study surface chemical and physical changes during paint curing, service abrasion and weathering, but has often required the use of advanced statistical analysis methods such as chemometrics to discern these changes. Results from our studies using this and related techniques and the technical challenges that have arisen will be presented

Prognostic tools for lifetime prediction of aircraft coatings: Paint degradation

A direct interrogation, portable analysis technique (portable FT-IR) and a novel environment-monitoring profluorescent sensor for studying aircraft coating degradation have been developed. For the direct interrogation approach, a standard military aircraft paint: 459-line Anzothane flexible polyurethane (lead free) has been used to illustrate a new potential field technique to evaluate coating service lifetime, portable FT-IR. This technique allows direct analysis of chemical changes within the degrading coatings and has the potential to evaluate service lifetime when coupled with advanced statistical analysis methods (chemometrics). The degradation environment monitoring sensors are embodied in a profluorescent environment-sensitive witness patch that may be analysed in-service by a field-deployable fluorescence spectrometer. Accelerated ageing for both the paint and the witness patches has been undertaken and their capabilities as aircraft paint degradation monitors assessed. © (2010) Trans Tech Publications

Subcutaneous Direct-to-Implant Breast Reconstruction

BACKGROUND: Direct-to-implant breast reconstruction can be achieved more easily by means of soft-tissue replacement devices such as dermal matrices and synthetic meshes. The feasibility of a subcutaneous approach has been recently investigated by some studies with different devices functioning as implant support. Aim of this study is to analyze the long-term results, both objective and subjective, of a previous nonrandomized trial comparing prepectoral (subcutaneous) and retropectoral breast reconstructions. METHODS: Patients enrolled in a nonrandomized prospective trial, comparing the standard retropectoral reconstruction and the prepectoral subcutaneous approach, using a titanium-coated mesh in both techniques, were followed up and evaluated for long-term results. Cases were compared in terms of the causes and rate of reinterventions, of the postoperative BREAST-Q questionnaire results, and of an objective surgical evaluation. RESULTS: The subcutaneous group had a rate of implant failure and removal of 5.1% when compared with 0% in the retropectoral group. Aesthetic outcome was significantly better for the subcutaneous group both at a subjective and at an objective evaluation. Capsular contracture rate was 0% in the subcutaneous group. CONCLUSIONS: A higher rate of implant failure and removal, although not significant, always because of skin flaps and wound problems, should be taken into account for a careful patients selection. The subcutaneous breast reconstruction shows good long-term results. A coherent subjective and objective cosmetic advantage of this approach emerges. Moreover, no capsular contracture is evident, albeit in a relatively limited number of cases