Estudo da dispersão de pigmentos orgânicos em resina de polipropileno para aplicação em fibras e filamentos

Abstract

Polypropylene has become widely used in fiber and filament applications; most part of these applications use colorful pigments to satisfy aesthetic necessities, communication, identification and others. To achieve the effect of the needed color it is necessary that the pigment has been well dispersed and distribute in the polymer. The appropriate dispersion is usually achieve with the combination of several mechanisms, that can occur at the same time during the mixture operation, such as: initial wetting, size reduction of the pigments, amount of aggregates and agglomerates, intimate wetting, particle uniform distribution in the medium and stabilization of the particles to avoid re-agglomeration. In this work the dispersion of two different organic pigments based on cupper phthalocianine (Pigment Blue 15) and betaoxynaphthoic acid (Pigment Red 48) in polypropylene resin with different humectants systems was studied. The characteristics of each formulation component, the determination of maximum pigment loading in polymer melts based on the CPVC (Critical Pigment Volume Concentration) concept, the ideal conditions of processing in static mixer and co-rotating twin screw extruder and the dispersion were evaluated by tint strength, filter pressure value and scanning electron microscopy. The results showed that there is an optimum humectant for each kind of pigment. The best results were obtained with the red pigment and the oxidized polyethylene wax, in which the filter pressure value was below 2 bar/g. The results for the blue pigment were not satisfactory.