Heat and Moisture Modelling of Vacuum Insulated Retrofits with Experimental Validation

Vacuum insulation panels (VIPs) offer 8-10 times the thermal resistance of fiberglass insulation and would fit the need for a low conductivity exterior insulation. A composite insulation panel using VIPs encased in rigid foam was developed, built, and tested. Two different sizes of VIPs were used for that stage of the project, and after monitoring and evaluation, they showed contrasting results. A simulation study was performed to find the optimal VIP solution that maximized the effective thermal conductivity and minimized the mould growth potential. In total, 5 wall assemblies with VIPs used as the exterior insulation were simulated using WUFI and WUFI2D. The simulations showed that the humidity levels at the inside face of the OSB inboard of the VIPs decreased when 200 mm by 300 mm VIPs were used, but they did not reach the thermal performance thresholds of R5.28 m2K/W. The hygrothermal analysis showed that under similar conditions, a VIP insulated wall assembly would have a lower relative humidity at the sheathing surface compared to EPS and XPS. The one-and two-dimensional simulations were compared and found that WUFI Pro was capable to evaluate a VIP-insulated wall assembly.

Design and Mechanical Evaluation of Sutureless Implants for the Surgery Treatment of Rotator Cuff Tears

Rotator cuff (RC) tears cause pain and functional disability of the shoulder. Despite advances in suture anchors, there are still reports about the incidence of surgical-related injuries to RC mainly associated with sutures. The purpose of this study was to design and evaluate the mechanical behavior of sutureless implants to repair RC tears. We hypothesized that the implants present mechanical characteristics suitable for the surgical treatment of RC tears as suture anchors. Three different implants (T1,T2,T3) were designed and fabricated with titanium: T1 has two rods and rectangular head; T2 has two rods with a small opening and enlarged rectangular head and T3 has three rods and a circular head. The implants were fixed in rigid polyurethane foam blocks by a series of blows, and the applied mechanical loads along with the number of blows were quantified. Pullout tests using tapes fixed between the implant head and testing machine grip were conducted until implant failure. The maximum pullout strength and displacement of the implant relative to the rigid foam block were computed. Statistical significance was set at p < 0.05. Owing to its geometric configuration, implant T2 presented the best characteristics related to stability, strength, and ease of insertion. Implant T2 confirms our hypothesis that its mechanical behavior is compatible with that of suture anchors which could lead to the reduction of RC repair failures and simplify the arthroscopic procedure.

Melamine-formaldehyde rigid foams – Manufacturing and their thermal insulation properties

The manufacturing of novel melamine-formaldehyde rigid foam material, by blowing the melamine-formaldehyde (MF) resin emulsion with pentane and further catalytic and thermal curing, is presented in this work. The process of foaming is described in terms of particular process parameters, which are; the proportions of blowing, curing, emulsifying agents. The examination of the foam, by SEM images, shows that the foam pore sizes are in the range from 150 to 250 µm. The thermal characterization of the obtained foams, is described in terms of thermal conductivity contributions of solid, gas and radiation conduction to total thermal conductivity at atmospheric and vacuum condition. The foam with densities from 50 to 80 kg/m3 achieve thermal conductivity at an atmospheric pressure of 33–34 mW/(m × K), while in a vacuum of 6–7 mW/(m × K). Compared to other organic polymer foams, MF foams have superior fire resistance and chemical stability. The innovation of MF rigid foams presented here, compared to other well-known MF flexible foam, is in their rigid structure, combined with low density and thermal conductivity, which makes this particular foam potentially useful in the manufacture of vacuum insulation panels (VIP).