Polypropylene/talc composites. Influence of surface activity and crystallinity of talc particles on mechanical properties

CASTILLO, LUCIANA E; CAPIATI, NUMA JOSÉ; BARBOSA, SILVIA ELENA

Sitges

Conferencia; Third International Symposium: Frontiers in Polymer Science; 2013

Editorial Elsevier

Nowadays, talc filled polypropylene (PP) is one of the most used composites in a wide range of applications, due to talc acts as a good nucleating agent, increasing PP crystallinity and improving the mechanical properties. During the last decades, many authors have studied the effect of different parameters, such as volume fraction, talc particle orientation, and particle surface treatment on the final properties. However, the influence of both talc morphology and surface treatment has not been yet considered simultaneously. In this work, the structure and mechanical properties of PP/talc composites were studied using two talc samples having different crystalline morphologies (macro and microcrystal) and different surface treatments which allows delamination, particle size reduction and surface activity variation (hydrophobic or hydrophilic character). In terms of the composite structure, both particles of micro and macrocrystalline talc are well distributed in the matrix. However, macrocrystalline talc induces higher crystallinity degree in PP than microcrystalline one, as a consequence of the higher crystalline character of the first. In addition, the dispersion degree is even better in composites with hydrophobic surfaceLs talc. Also, both treated samples (having hydrophobic or hydrophilic surfaces) induce a higher crystallinity degree than untreated ones, due to the increased number of PP nuclei favored by particle size reduction. Composites containing microcrystalline talc suppress the ƒÀ phase, detected for PP, while composites with macrocrystalline talc hold and increases this reflection, for untreated and treated samples. There are differences in the mechanical behavior of composites with micro and macrocrystalline talc, mainly in yield strength and elongation at break. Microcrystalline talc filled PP fail at lower elongations than PP/macrocrystalline, which can be partially attributed to the suppression of ƒÀ phase. However, in the case of treated microcrystalline composites, mechanical performance is improved, showing the treatment effect on the increment of PP/talc adhesion.