New formulation technology to boost sun protection.

OBJECTIVE: As every skin type worldwide is concerned by photoprotection, with consumers preferring cosmetic elegant and efficient sunscreen products, we aim at developing the most performant and desirable sun care products. METHODS: We selected an interesting polymer, abbreviated AAHCP and designed scanning electron cryomicroscopy (cryoSEM), small angle and wide angle X-ray scattering and confocal laser scanning microscopy studies to understand its behaviour in solution and in simplex sun care formulations. This allowed us to develop innovative sunscreen formulation technology that was demonstrated by in vitro and in vivo photoprotection methods. Comprehensive photoprotection evaluations were made on the fully developed sun protection product. RESULTS: We observed the polymer oil structuring properties as well as its ability to form small and stable droplets in simplex emulsions. In vitro and in vivo sun protection factor (SPF) measurements demonstrated the sun protection boosting efficacy of AAHCP polymer in several emulsions or as a stand-alone emulsifier. This formulation technology also allowed to filtering system concentration optimization. Use-test performed on a fully developed AAHCP-based sunscreen validated its optimal performances as well as its ideal cosmetic features, with non-sticky, non-greasy perception and invisible skin result. CONCLUSION: For the first time, thanks to a new specific polymer creating a new type of emulsion, we succeed in reconciliate in a single sun care product maximal SPF efficacy, resistance to numerous stresses and optimal sensoriality.

OBJECTIF: Tous les types de peau du monde étant concernés par la photoprotection, avec des consommateurs qui préfèrent des produits solaires élégants et efficaces, nous nous sommes donné pour mission de développer les produits de protection solaire les plus performants et les plus agréables. MÉTHODES: Nous avons sélectionné un polymère intéressant, l'« AAHCP ¼ dans sa forme abrégée, et avons conçu les études de cryomicroscopie électronique à balayage (CryoSEM), de diffusion des rayons X et de microscopie confocale à balayage laser (Confocal Laser Scanning Microscopy) pour comprendre son comportement en solution et dans des formulations de protection solaire simples. Cela nous a permis de développer une technologie innovante de formulation de protection solaire, qui a été démontrée par des méthodes de photoprotection in vitro et in vivo. Le produit de protection solaire a fait l'objet d'évaluations exhaustives de la photoprotection à la fin de sa phase de développement. RÉSULTATS: Nous avons observé les propriétés de structuration de l'huile polymère, ainsi que sa capacité à former de petites gouttelettes stables dans les émulsions de simplex. Les mesures du facteur de protection solaire (sun protection factor, SPF) in vitro et in vivo ont montré que la présence du polymère AAHCP dans plusieurs émulsions ou comme émulsifiant autonome optimise le niveau de protection solaire obtenu. Cette technologie de formulation a également permis d'ajuster la concentration du système de filtration. Le test en conditions réelles d'utilisation effectué sur une protection solaire à base d'AAHCP à la fin de la phase de développement a permis de valider ses performances optimales, ainsi que ses caractéristiques cosmétiques idéales, avec une sensation non collante et non grasse, et un résultat invisible sur la peau. CONCLUSION: Pour la première fois, grâce à un nouveau polymère spécifique créant un nouveau type d'émulsion, nous avons réussi à développer un produit de protection solaire simple à l'efficacité SPF maximale, qui résiste à de nombreuses contraintes et possède une sensibilité optimale.

Aging of cornstarch particles suspended in aqueous solvents at room temperature.

Starch suspensions are often used as model systems to demonstrate extreme shear-thickening effects. We study the aging of cornstarch particles in aqueous suspensions at room temperature by granulometry and rheological measurements. When starch is diluted in glycerol, no long-term changes are observed. The situation differs when water is used as solvent. For volume fractions up to 20 vol %, when the cornstarch suspensions in water are stored under continual agitation, we observe an increase in viscosity. When the cornstarch suspension is aged under quiescent conditions, no evolution of the particle size is observed. In the concentrated situation, the rheological properties vary independent of the storage condition. We show that the increase in viscosity is related to air trapped in the pore space and to the swelling of the granules and leakage of the amylopectin component of the starch into the surrounding water. The relative importance of the two processes depends upon the particle concentration and upon the energy brought to the system.

Impact of the Wetting Length on Flexible Blade Spreading.

We study the spreading of a Newtonian fluid by a deformable blade, a common industrial problem, characteristic of elastohydrodynamic situations. Here, we consider the case of a finite reservoir of liquid, emptying as the liquid is spread. We evidence the role of a central variable: the wetting length l_{w}, which sets a boundary between the wet and dry parts of the blade. We show that the deposited film thickness e depends quadratically with l_{w}. We study this problem experimentally and numerically by integration of the elastohydrodynamic equations, and finally propose a scaling law model to explain how l_{w} influences the spreading dynamics.