In this study, composites based on poly(lactic acid) (PLA)/talc were prepared at different compositions by melt mixing in a twin screw extruder. The effect of a nucleating agent, talc, on the crystallization behavior, rheological and morphological properties of PLA was investigated. DSC results showed that the addition of the mineral filler in the range between 1 and 5 wt. % to the PLA matrix increases the degree of crystallinity. This finding shows that talc acted as a nucleating agent for PLA during the processing stage. The composites morphology was also studied using a scanning electron microscope (SEM). The micrographs showed that a good dispersion of talc was achieved in all compositions analyzed. The rheology of PLA/talc composites was evaluated with the dynamic mode and correlated with the aforementioned observed morphology. The results showed that the addition of the mineral filler to the PLA matrix decreased system viscosity, thus highlighting the filler's lubricant effect. As talc content increased, system's viscosity also increased, providing material with higher elastic behavior. Thermal analysis showed that the composition of 3 wt.% of talc added to polymer matrix seems to be interesting with regard to the need of articles possessing good dimension stability.

Atualmente, compósitos à base de polímero/carga mineral têm sido alvo de grande interesse, tanto em indústrias quanto em pesquisas acadêmicas, devido à melhora significativa nas propriedades dos materiais quando comparadas ao polímero virgem. O carbonato de cálcio (CaCO3) é um dos materiais mais abundantes do planeta e tem sido geralmente usado na obtenção de compósitos poliméricos. As propriedades de suas partículas (tamanho, forma e módulo) podem provocar um efeito significativo, especialmente no comportamento mecânico. As misturas PEAD/CaCO3 são amplamente usadas na indústria automotiva. No presente estudo, o efeito da incorporação de CaCO3 nas propriedades mecânicas e de escoamento destas misturas foi avaliado através de um planejamento fatorial simples de dois níveis, do tipo 2n, com n = 3 fatores: teor de carga; tamanho de partícula e velocidade de rotação da rosca. As variáveis de resposta analisadas foram: módulo de Young e resistência ao impacto e índice de fluidez (MFI). Os resultados mostraram que, dentro dos níveis estabelecidos, o fator que apresentou mais impacto nas variáveis de resposta foi o teor de carga mineral.

In recent years, polymer/mineral filler composites have attracted great interest, both in industries and academic researches, because they often show a remarkable improvement of materials properties when compared to virgin polymers. Calcium carbonate, CaCO3, is one of the most abundant materials on the planet and it has been often used to obtain polymer composites. The properties of its particles (size, shape and modulus) can provoke a significant effect, especially on mechanical behavior. HDPE/CaCO3 compounds are widely used in the automotive industry. In the present study, the effect of CaCO3 addition to the mechanical and flow properties of these compounds was evaluated using a simple 2n factorial design, with n = 3 factors: filler content; particle size and screw speed. The dependent variables analyzed were: Young modulus; impact strength and melt flow index (MFI). The results showed that the greatest impacts on the dependent variables were related to changes on mineral filler content.