Renan Demori

Films based on neutralized chitosan citrate as innovative composition for cosmetic application

In this work, citrate and acetate buffers, were investigated as neutralizers to chitosan salts in order to provide biocompatible and stable films. To choose the appropriate film composition for this study, neutralized chitosan citrate and acetate films, with and without the plasticizer glycerol, were prepared and characterized by thickness, moisture content, degree of swelling, total soluble matter in acid medium, simultaneous thermal analysis and differential scanning calorimetry. Chitosan films neutralized in citrate buffer showed greater physical integrity resulted from greater thicknesses, lower moisture absorbance, lower tendency to solubility in the acid medium, and better swelling capacities. According to thermal analyses, these films had higher interaction with water which is considered an important feature for cosmetic application. Since the composition prepared in citrate buffer without glycerol was considered to present better physical integrity, it was applied to investigate hyaluronic acid release in a skin model. Skins treated with those films, with or without hyaluronic acid, show stratum corneum desquamation and hydration within 10min. The results suggest that the neutralized chitosan citrate film prepared without glycerol promotes a cosmetic effect for skin exfoliation in the presence or absence of hyaluronic acid.

Morphological, thermo-mechanical, and thermal conductivity properties of halloysite nanotube-filled polypropylene nanocomposite foam

Studies about polypropylene nanocomposite foams are receiving attention because nanoparticles can change physical and mechanical properties, as well as improve foaming behavior in terms of homogeneous cell structure, cell density, and void fraction. In this research, the foaming behavior of polypropylene, polypropylene/long-chain branched polypropylene (LCBPP) 100/20 blend, and polypropylene/LCBPP/halloysite nanocomposites with 0.5 and 3 parts per hundred of resin (phr) is studied. The LCBPP was used to improve the rheological properties of polypropylene/LCBPP blend, namely the degree of strain-hardening. Transmission electron microscopy observation indicated that halloysite nanotube particles are well distributed in the matrix by aggregates. Subsequent foaming experiments were conducted using chemical blowing agent in injection-molding processing. Polypropylene foam exhibited high cell density and cell size as well as a collapsing effect, whereas the polypropylene/LCBPP blend showed a reduction of the void fraction and cell density compared to expanded polypropylene. Also, the blend showed reduction of the collapsing effect and increase of homogeneous cell size distribution. The introduction of a small amount of halloysite nanotube in the polypropylene/LCBPP blend improved the foaming behavior of the polypropylene, with a uniform cell structure distribution in the resultant foams. In addition, the cell density of the composite sample was higher than the polypropylene/LCBPP sample, having increased 82% and 136% for 0.5 and 3 phr of loaded halloysite nanotube, respectively. Furthermore, the presence of halloysite nanotube increased crystallization temperature (Tc) and slightly increased dynamic-mechanical properties measured by dynamic-mechanical thermal analysis. By increasing halloysite nanotube content to 3 phr, the insulating effect increased by 13% compared to polypropylene/LCBPP blend. For comparative purposes, the effect on foaming behavior of polypropylene/LCBPP was also investigated using talc microparticles.

Evaluation of surfactants addition as compatibilizers for halloysite nanotubes filled polypropylene nanocomposites

PP nanocomposites were obtained with halloysite nanotubes (HNT) by melting blending using a twin screw extrusion. Some additives were used for obtaining good mechanical and thermal properties, such as PP-g-MA and nonionic surfactants to increase the force of adhesion between the clay and the thermoplastic matrix. Three dimensional, edge-to-edge and face-to-edge interactions between HNT occurred, which are the main reasons for the simultaneous increases in Young modulus and impact Izod of PP/HNT nanocomposites. The use of PP-g-MA increases the formation of aggregates of the HNT in the matrix. On the other hand, the use of nonionic surfactants increase the dispersion of HNT in PP matrix and showed some individual HNT in the matrix. Tm and Xc were not affected by its presence, PP-g-MA or nonionic surfactants. The use of HNT showed a slight nucleation effect in the crystallization of PP. The use of PP-g-MA reduces the mechanical and thermal properties due to the larger-sized aggregates of HNT formed in the ma...

Mistura polipropileno/poliestireno: um exemplo da relação processamento-estrutura-propriedade no ensino de polímeros

Polymer blends remain an important research topic in different areas, in spite of innumerous studies over the years. In particular, mixtures of polypropylene and polystyrene are among the most studied, mainly owing to their low cost and technological relevance. In this work, the students enrolled in the discipline Polymer Processing I (PG24) in the Materials Science Graduate Program (PGCIMAT-UFRGS) produced blends of polypropylene and polystyrene, where all polymer processing steps were performed during lab classes. Then, each student undertook a characterization procedure with a specific technique, which included samples preparation, the analysis itself and discussion of the results. Subsequently, the results were confronted in the classroom, where we sought the correlations. Finally, all students reviewed this article, including suggestions and criticisms. As expected, the mixture of polystyrene and polypropylene formed an immiscible blend. Furthermore, the processing affected the characteristics of the polymers, leading to a reduction in molecular weight, and as a result a drop in its physical properties. In the PP/PS mixtures, phase separation produced PS domains with micrometers in size, and low adhesion to the PP matrix, which explains the loss of mechanical properties.

Evaluation of foaming polypropylene modified with ramified polymer

Polypropylene foams have great industrial interest because of balanced physical and mechanical properties, recyclability as well as low material cost. During the foaming process, the elongational forces applied to produce the expanded polymer are strong enough to rupture cell walls. As a result, final foam has a high amount of coalesced as well as opened cells which decreases mechanical and also physical properties. To increase melt strength and also avoid the coalescence effect, one of the current solution is blend PP with ramified polymers as well as branched polypropylene (LCBPP) or ethylene-octene copolymer (POE). In this research to provide extensional properties and achieve uniform cellular structures of expanded PP, 20 phr of LCBPP or POE was added into PP matrix. The blend of PP with ramified polymers was prepared by twin-screw extrusion. Injection molding process was used to produce PP foams using azodicarbonamide (ACA) as chemical blowing agent. The morphological results of the expanded PP displ...

Recycling cycle of materials applied to acrylonitrile-butadiene-styrene / policarbonate blends with styrene-butadiene-styrene copolymer addition

The scope of this research is the recycling of polymers from mobile phones hulls discarded and the performance evaluation when they are submitted to the Recycling Cycle of Materials (RCM). The studied material was the ABS/PC blend in a 70/30 proportion. Different compositions were evaluated adding virgin material, recycled material and using the copolymer SBS as impact modifier. In order to evaluate the properties of materials composition, the samples were characterized by TGA, FTIR, SEM, IZOD impact strength and tensile strength tests. At the first stage, the presented results suggest the composition containing 25% of recycled material and 5% of SBS combines good mechanical performance to the higher content of recycled material and lower content of impact modifier providing major benefits to recycling plans. Five cycles (RCM) were applied in the second stage; they evidenced a decrease trend considering the impact strength. At first and second cycle the impact strength was higher than reference material ...

Occurrence and recovery of small-sized plastic debris from a Brazilian beach: characterization, recycling, and mechanical analysis

Small-sized plastic debris are an increasing global concern, particularly in environmental protected areas. Consequently, tourism-based economy of poor coastal regions is also impaired. Nevertheless, little interest has been shown about recycling approaches of such materials, mostly because of the natural degradation of polymers on these conditions. This research presents the report of the occurrence of plastic debris nearby Lençóis Maranhenses National Park, on the northeast Brazilian coast, aiming to provide a feasible method for recycling. We collected more than 80 samples from the sediment and classified them via FT-IR. Degraded polypropylene samples were selected for blending with virgin material using different concentration rates, and were mechanically tested. Tensile testing results suggest that 5% recycled material concentration mixture has suitable mechanical properties on the elastic regime for applications on new parts. Our findings show that particular interest should be addressed on the recovery of commodity plastic debris from environmental protected areas.

Design, materiais e sustentabilidade: micronização de produto multi-material visando sua reciclagem

A aplicacao do ecodesign na selecao de materais e de extrema importância. Entretanto, percebe-se uma tendencia contraria a essa pratica, a de utilizacao de diversos materiais em um componente do produto (chamado multi-materiail). Apesar de apresentarem vantagens de fabricacao,a reciclagem dos multi-materiais e complexa devido a dificuldade de separacao dos materiais. Nesse contexto, apresenta-se como hipotese a utilizacao da micronizacao como alternativa para viabilizar o reprocessamento dos multi-materiais. Assim sendo, essa pesquisa buscou analisar a possibilidade de aplicacao da micronizacao na reciclagem de produtos multi-materias co-injetados. Para tanto, o estudo pratico consistiu na micronizacao de escovas de dente multi-materiais e posterior extrusao com polietileno de baixa densidade linear (PEDBL) virgem. Os resultados demonstraram que a micronizacao pode ser utilizada na reciclagem desses produtos, uma vez que o processo analisado se mostrou factivel, utilizando metodos acessiveis. Alem disso, nao houve degradacao do material ao longo do processo, assim como, o mesmo nao danificou os equipamentos.