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Properties Decreased (property + decreased)

Distribution by Scientific Domains

Polymers and Materials Science	75%

Selected Abstracts

Formulation and development of a patch containing tamarind fruit extract by using the blended chitosan,starch as a rate-controlling matrix

INTERNATIONAL JOURNAL OF COSMETIC SCIENCE, Issue 3 2003
J. Viyoch
Synopsis A cosmetic patch containing tamarind fruit extract was formulated and developed by blending two types of natural polymers: chitosan with molecular weight of 100 000 and starch such as corn, potato or tapioca starch. The physicochemical characteristics, i.e. flexibility, colour, transparency, integrity, gloss, water sorption and bioadhesion property and the stability of the patch without tamarind content were investigated. Stability test was performed by keeping the prepared patches at 4 °C, at room temperature or at 45 °C for 2 weeks. The results showed that the formulations composed of chitosan:corn starch ratio of 4.5 : 0.5 (CC4.5 : 0.5) and chitosan:tapioca starch ratios of 4.5 : 0.5 (CT4.5 : 0.5) and 4.0 : 1.0 (CT4 : 1) provide patches with favourable physical characteristics, high water sorption, good bioadhesion ability and good stability. After the lyophilized tamarind extract in an amount corresponding to 5% of tartaric acid was incorporated into the formulations of CC4.5 : 0.5, CT4.5 : 0.5 and CT4 : 1, the ability of the patches to adhere to skin was improved. However, after keeping the test patches at room temperature or at 45 °C for 6 weeks, their colours were intensified while their flexibilities and skin adhesion properties decreased. A 12-h in vitro permeation was investigated by studying the cumulative amount of tartaric acid permeated through the Silastic® membrane (Dow-Coming, Midland, MI, USA). The CC4.5 : 0.5 patch tended to give the highest amount of tartaric acid released. The release pattern of all the blended polymeric matrices was exhibited in two distinct phases: the rapid phase, where the flux averaged 3.61 µg min,1 mm,2; and the slow phase, where the flux averaged 1.89 µg min,1 mm,2. Résumé Un patch cosmétique contenant un extrait de fruit de Tamarin a été formulé et développé en mélangeant deux types de polymères naturels, le chitosan d'un poids moléculaire de 100 000 et d'amidon de maïs, de pomme de terre ou d'amidon de tapioca. Les caractéristiques physico chimiques, i.e. de flexibilité, couleur, transparence, intégrité, brillance, pouvoir de sorption de l'eau, la propriété de bio adhésion et la stabilité des patchs sans tamarin ont été déterminées. Le test de stabilité A été effectué en gardant les patchs préparés à 4 °C, température ambiante ou 45 °C pendant 2 semaines. Les résultats montrent que la formulation composée de chitosan:amidon de maïs au taux relatif de 4.5 : 0.5 (CC4.5 : 0.5), de chitosan:amidon de tapioca aux taux relatifs de 4.5 : 0.5 (CT4.5 : 0.5) et de 4.0 : 1.0 (CT4 : 1) conduit aux propriétés physiques les plus favorables, haute sorption d'eau, bonnes capacité de bio adhésion et stabilité. Après que l'extrait lyophilisé de tamarin ait été incorporé au taux correspondant à 5% d'acide tartrique dans les formulations CC4.5 : 0.5, CT4.5 : 0.5 et CT4 : 1, la capacité des patchs à adhérer à la peau a été améliorée. Cependant, la conservation des patchs à température ambiante et à 45 °C pendant 6 semaines conduisait à une intensification de leurs couleurs tandis que leur propriété d'adhésion diminuait. La perméation in vitro sur 12 heures a étéétudiée en suivant le taux cumulé d'acide tartrique passant à travers la membrane de Silastic®. Le CC4.5 : 0.5 tendait à donner le taux le plus élevé d'acide tartrique re largué. Le profil de relarguage de toutes les matrices de polymères montrait deux phases distinctes, l'une, rapide au flux moyen de 3.61 µg min,1 mm,2 et une, plus lente, de flux moyen 1.89 µg min,1 mm,2. [source]

Microstructure and Mechanical Properties of Silicon Nitride Ceramics with Controlled Porosity

JOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 6 2002
Jian-Feng Yang
Porous silicon nitride ceramic with a porosity from 0,0.3 was fabricated by partial hot-pressing of a powder mixture of ,-Si3N4 and 5 wt% Yb2O3 as sintering additive. Irrespective of the porosity, the samples exhibited almost the same microstructural features including grain size, grain aspect ratio, and pore size. Porosity dependences of Young's modulus, flexural strength, and fracture toughness (KIC) were investigated. All these properties decreased with increasing porosity. However, because of the fibrous microstructure, the decreases of flexural strength and fracture toughness were moderate compared with the much greater decrease of Young's modulus. Thus, the strain tolerance (fracture strength/Young's modulus) increased with increasing porosity. The critical energy release rate also increased slightly with an increasing volume fraction of porosity to 0.166 and remained at the same level with that of the dense sample when the porosity was 0.233. They decreased as porosity increased further. [source]

Thermal, electrical, and mechanical properties of Si3N4 filled LLDPE composite

POLYMER COMPOSITES, Issue 7 2009
Qunli An
Silicon nitride (Si3N4) filled linear low-density polyethylene (LLDPE) composite was prepared. The effects of Si3N4 filler content, dispersion, and LLDPE particle size on the thermal conductivity, and Si3N4 filled content on the mechanical and electrical properties of Si3N4 reinforced LLDPE composites prepared using powder mixing were investigated. The results indicate that there existed a unique dispersion state of Si3N4 particles in LLDPE, shell-kernel structure, in which Si3N4 particles surrounded LLDPE matrix particles. With increasing filler content and LLDPE particles size, thermal conductivity increased, and reached 1.42 W/m K at 30 vol% of filler, seven times as that of unfilled LLDPE. Furthermore, the examinations of Agari model demonstrate that larger size LLDPE particles form thermal conductive networks easily compared with smaller ones. The values predicted by theoretical model underestimate the thermal conductivity of Si3N4/LLDPE composites. In addition, the composites still possessed rather higher electrical resistivity and dielectric properties, but the mechanical properties decreased. POLYM. COMPOS., 2009. © 2008 Society of Plastics Engineers [source]

Effects of addition of functionalized SEBS on rheological, mechanical, and tribological properties of polyamide 6 nanocomposites

POLYMER ENGINEERING & SCIENCE, Issue 1 2010
Yosuke Nishitani
The effects of the addition of styrene-ethylene/butylene-styrene copolymer (SEBS) with various functionalized groups on the rheological, mechanical, and tribological properties on polyamide 6 nanocomposite filled with layered silicate (PA6/Clay) were investigated. Four types of SEBS: unmodified SEBS (SEBS), maleic anhydride grafted SEBS (SEBS- g -MA), amine group grafted SEBS (SEBS- g -NH2), and carboxyl group grafted SEBS (SEBS- g -COOH) were added with PA6/Clay nanocomposite to prepare various polymer blends. These polymer blends were extruded by a twin screw extruder and injection molded. Dynamic viscoelastic properties of these blends in the molten state and their tensile, impact, and tribological properties were evaluated. The viscoelastic properties were found to increase with the addition of SEBS and were highly influenced by the types of functionalized groups contained. Influence of the addition of SEBS on the mechanical properties of these systems differed for each mechanical property. Although the tensile properties decreased with SEBS, Izod impact properties improved with the addition of various functionalized SEBS. These mechanical properties and viscoelastic properties correlated closely with the size of dispersed SEBS particles and interparticle distance. The tribological properties also improved with the addition of SEBS, and the influence of the amount added was higher than the type of SEBS used. POLYM. ENG. SCI., 2010. © 2009 Society of Plastics Engineers [source]