Caracterização estrutural e monitoramento ótico da cristalização de nanocompósitos de polietileno de alta densidade com partículas de diferentes geometrias durante a moldagem por injeção
Visualizar/ Abrir
Data
2014-03-06Autor
Beatrice, Cesar Augusto Gonçalves
Metadata
Mostrar registro completoResumo
The main objectives of this project were to study the morphology, the crystallization
kinetics and to monitor on-line the crystallization during the injection
molding process using an optical system of nanocomposites of high density
polyethylene (HDPE) with three different inorganic particles: montmorillonite
nanoclay, halloysite nanotubes and faujasite type zeolite. The optical system
allowed analyzing the crystallization process by the changes of the optical
properties during the solidification of the materials. The nanocomposites were
prepared by melt intercalation in a twin-screw extruder. The resultant structures
were characterized by transmission electron microscopy (TEM) and rheological
properties. The extruded nanocomposites developed intercalated and well distributed
structures. Crystallization kinetics studies were done by differential
scanning calorimetry (DSC) and rheological measurements. It was concluded
that the nanoparticles in quiescent conditions accelerated the overall crystallization
of HDPE, acting as nucleating agents. The nucleating effect of these particles
was predominant over the HDPE crystallization and they also modified the
nucleation mechanism and the crystal morphology in some conditions. From the
studies of flow induced crystallization, it was observed again that the nanoparticles
accelerated the crystal growth rate. In this case it was attributed to the
weak forces between the polymer chains and the surface of the nanoparticles.
Finally, the nanocomposites’ crystallization was monitored during the injection
molding process. The optical system showed that the nanoparticles accelerated
the crystallization of HDPE; the optical results were correlated with the morphology
of the injection molded samples.