No abstract

A model material simulating the mechanical and surface properties of a real human skin was developed for use as a substrate in adhesion-to-skin evaluation. It is a protein-lipid composition possessing film-forming ability. The composition is based on gelatin plasticized by glycerol, polysaccharides and a mixture of lipids that mimick the skin's lipid structure and creates a hydrophobic surface. To enhance the material hydrolytic stability, the composition was cross-linked by formaldehyde, producing a water-swellable but insoluble matrix. The surface topography of a real skin was achieved by a silicone replica technique. Thin films with thickness of 100 ± 10 µm were cast. The effect of the components ratio and preparation technique on the film mechanical, surface and hydrolytic properties was studied. Based on the results obtained, a formulation having mechanical and surface properties comparable to that of a human skin was selected. The relevance of the model material was evaluated in lap-shear and 180 • -peel adhesion tests and the results were compared to a finger or a forearm skin of ten healthy volunteers (in vivo tests). For validation purposes, commercial surgical tapes Micropore™ and Transpore™ and Mylar ® polyester film were also used. The effects of substrate, adhesive, conditions of the joint preparation and the test employed on adhesion strength were studied. The results obtained show that the mechanical and surface properties of the model material are close to those of the human skin.

No abstract

The objective of the present study is to investigate the effect of electrospun nanofiber reinforcement on the properties of commercially available, hyperbranched polymer modified (Hybrane, 0.3 wt.% DSM) dental formulations. The emergence of functionalized nanoscale reinforcements having large surface area (hundreds of square meters/gram) has enabled the design of novel nanocomposites with new and complex structures leading to enhanced mechanical and physical properties. Electrospun nanofibers from a range of polymer chemistries (PVOH, PLLA, Nylon 6) have been investigated as a reinforcing phase at levels between 0.01 and 0.3 wt.%, with and without a silane coupling agent surface treatment. The experimental results indicate that 0.05 wt.% reinforcement with 250 nm diameter PVOH nanofibers leads to a 30% improvement in compressive strength, coupled with a shrinkage reduction of about 50%. Electrospun fiber reinforcement by other chemistries or at other diameters showed either no property improvement or led to property loss.