In order to provide good adhesion for natural nail coatings and to avoid loss of adhesion between the substrate and the coating, the mechanical properties of the coating should be close to those of the substrate. Three different mono-functional monomers (HPMA, THFA, THFMA) and one bi-functional monomer (EGDMA) have been added to decrease the viscosity of un-polymerized composition. Optimal monomer concentration was found evaluating monomer concentration effect on viscosity. Polymerized coatings were tested with monomer concentrations of 30% and 40%. The tensile strength properties of the polymerized coatings were determined 24 hours after polymerization. Polymerization T and conversion rate of unsaturated links were also studied to find the best monomer for natural nail coatings.

Increased interest in aesthetic, natural nail coatings has encouraged more in-depth studies, and particularly of ultraviolet curable coatings, their formation, processing, characteristics, and removal. This study investigated the impact of various thixotropic agents (organically modified hectorite and bentonite clays) on water-based oligomer system rheology. Ingredients were evaluated to determine their influence on unreacted composite characteristics (viscosity and pigment suspension stability) and reacted film characteristics (modulus of elasticity, elongation at break, and film adhesion force). It is concluded that clay-based thixotropic agents are suitable for use as a suspension agent in nail polish formulations and, depending on the concentration, can decrease the risk of pigment sedimentation and syneresis.

An increased demand for new and improved coating systems, for environmental & health & safety and performance reasons, have appeared during the recent decades. Currently, there is new interest in preparation of thin UV curable urethane acrylate (UA) composite coatings with short-term properties. Cellulose based additives: nitrocellulose, cellulose acetate butyrate, sucrose benzoate and silica were evaluated to determine their influence on unreacted composite characteristics (viscosity, pigment suspension stability) and characteristics of cured film (ultimate tensile strength, elongation at break, surface gloss, surface scratch resistance and film adhesion loss time). The most suitable additive content was found to provide required viscosity. All additives increase surface scratch resistance, but cellulose based additives increase surface gloss values and decrease the time of adhesion loss. Silica has great effect on the interaction between linear and hyperbranched urethane acrylates, which has crucial influence on the stability of uncured pigmented mixture samples.

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Individuals working in nail salons are exposed to 2-hydroxyethyl methacrylate (HEMA). HEMA has been found to have several effects on the skin: skin itching, peeling, redness and allergic contact dermatitis. The purpose of the study was to compare the effects of nail coatings containing HEMA and 2-hydroxypropyl methacrylate (HPMA) on the skin. In this study we explored the irritation properties of HEMA and HPMA containing nail coatings in cell cultures in-vitro and in skin PATCH tests under dermatological control. The cytotoxicity of coatings was tested in BALB/c3T3 and HaCaT cell lines by a neutral red uptake assay. Cytotoxicity was expressed as a concentration-dependent reduction of the uptake of neutral red, compared to the untreated controls. Open patch tests were supervised by a certified dermatologist. Polymerized coating extracts have little effect on Balb/c 3T3 cell viability, while having mild cytotoxic effects on HaCaT keratinocytes. Among two tested samples, extracts of HEMA containing coating exhibited higher cytotoxicity – reduction of keratinocyte viability by 28.29 % in case of undiluted 24 h extract and even by 48.26 % in case of 50 % extract was observed. Coating cytotoxiaty observed on HaCaT showed that the keratinocyte cell line was more sensitive to HEMA than to HPMA containing coating.