RESUMO O desenvolvimento de compósitos poliméricos reforçados com fibras naturais tem recebido grande destaque como tecnologia alternativa para o processamento de novos materiais que proporcionem um menor impacto ambiental, associado a uma baixa densidade, biodegradabilidade e propriedades mecânicas interessantes.Fibras naturais provenientes do coco verde apresentam, devido à sua composição química, maior rigidez e resistência mecânica comparada a outras fibras vegetais. Porém, fibras vegetais possuem uma baixa interação com a matriz polimérica, em virtude de seu caráter hidrofílico quando comparado à matriz polimérica, hidrofóbica. Neste trabalho, fibras de coco (FC) foram tratadas quimicamente por extração alcalina com hidróxido de sódio (NaOH) e mecanicamente utilizando uma ponteira ultrassônica em meio aquoso, e a técnica para averiguar os efeitos dos tratamentos nas fibras foi a microscopia eletrônica de varredura (MEV). Compósitos de polietileno de baixa densidade (LDPE) com diferentes teores de fibra de coco (5 e 10% m/m) foram preparados por mistura no estado fundido, utilizando um homogeneizador de alta rotação (DRAIS), seguido por prensagem a quente e estampagem para preparação de corpos de prova. Os compósitos de LDPE/FC foram caracterizados quanto às propriedades térmicas (calorimetria exploratória diferencial – DSC), mecânicas (ensaio de tração uniaxial e ensaio de dureza), características morfológicas (MEV) e de superfície (teste de ângulo de contato). O teor de fibra em massa exerceu influência nas propriedades mecânicas, de forma que um aumento do teor de fibra de coco em massa reduz ligeiramente a resistência à tração e provoca um aumento em torno de 100% no valor do módulo elástico do compósito. Por meio dos resultados obtidos por MEV e ângulo de contato, ambos os tratamentos se mostraram eficientes, porém sugerindo melhor eficiência no tratamento via extração alcalina.
Polypropylene (PP)/ethylene-vinyl acetate (EVA) (60/40) blends-based glassy carbon (GC) composites with different contents of GC (0.1 to 5 wt%) were melting processed in a twin-screw extruder and the thermal, mechanical, electrical and morphological properties were evaluated to verify the effectiveness of the addition of GC as filler. Moreover, the effect of the addition of maleic anhydride grafted polypropylene (PP-g-MA) as a compatibilizer agent was also verified. The composites presented dispersed phase morphology with preferential localization of GC on interfacial regions and into the EVA phase. The mechanical properties were improved with the addition of PP-g-MA as a compatibilizer agent for the blend and the addition of GC had little influence on these properties. The results obtained from thermal properties revealed that the GC contributes to the increase in the degree of crystallinity and thermal stability of the composites. The addition of 0.1 wt% of GC increased the elastic modulus and the ultimate tensile strength without loss in the impact strength when compared to the compatibilized blend. The addition of GC increases a decade of magnitude in the electrical conductivity of the PP/EVA blends.
The development of polymeric nanocomposites using clay minerals as a Nano filler is of great interest to researchers and industry. Many clay minerals are used to modify the properties of the polymers; this strategy improves the thermal and mechanical performance and changes the surface finishing and the processing characteristics. The Attapulgite (ATP), which is a clay mineral of the hydrated magnesium silicates family, has gained prominence in recent years because it combines low cost and high performance. It has a large surface area, strong absorption capacity superior to any other natural mineral, good mechanical resistance and thermal stability. These properties make ATP an ideal candidate for reinforcing polymeric materials. Different approaches and emerging technologies have been applied to improve the thermal and mechanical properties of polymer/ATP nanocomposites which can extend the different chemical treatments used in ATP. Therefore, this review article presents the latest advances related to the use of ATP in the development of polymeric nanocomposites, showing future perspectives for new trends in ATP applications. In general, ATP modifies the mechanical properties of polymers, either in the natural or modified state. And is a good alternative for the replacement of lamellar clays such as montmorillonites with the advantage of having a lower cost and a wide world market to be explored, that which drive new trends in applications for ATP, such as flame retardant of cotton fabrics, dye adsorption, hydrogel membranes for wound dressing, sustainable packaging and fuel cell applications.
The use of structural polymeric composites constitutes an interesting option in the area of wind turbine blade manufacturing. Nevertheless, thick composite components may present out-of-plane waviness in their fibers, compromising the service life of the wind blades. In this context, the present study aims to study the influence of out-of-plane waviness in the fibers with different degrees of severity as well as to verify the effect of fiber glass/epoxy resin composites immersion in distilled water and saline solution in their tensile strength (σmax), modulus of elasticity (E), and deformation at break (єrup), analyzing the reinforcement/matrix interface changes. The results showed that the increase in severity promoted, in general, a statistically significant deterioration in σmax of the samples exposed to the same environmental conditioning. The conditioning led to a decrease in E and an increase in єrup, attributed to the deterioration of the interface and the plasticization of the polymeric matrix, respectively, as evidenced by fractographic analysis. The effect of severity on the єrup and σmax properties was only noticed in laminates exposed to environmental conditioning, due to water sorption favoring the deterioration of the matrix/reinforcement interface, intensifying the deleterious effect of out-of-plane waviness of fibers.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.