O. O. Santana

Influence of annealing on the microstructural, tensile and fracture properties of polypropylene films

Abstract The influence of annealing temperature on the fracture properties of iPP films (one homopolymer and two propylene–ethylene block copolymers) is presented. The fracture behaviour is studied by means of the Essential Work of Fracture (EWF) procedure, and is complemented by the study of the effect of thermal treatment on tensile properties and microstructure, using differential scanning calorimetry (DSC) and wide-angle X-ray scattering (WAXS). It is shown that the initial metastable phase of quenched iPP films, widely known as smectic, transforms gradually into the monoclinic form as the annealing temperature is increased, resulting in an important improvement of the tensile properties, whereas the fracture parameters have different evolutions depending on the ethylene content. The reasons for a decrease in the essential work term and an increase in the plastic term as the crystal perfection grows are discussed on the basis of the microstructural changes of the crystalline phase and the smectic–monoclinic strain-induced phase transformation.

Essential work of fracture on PET films: influence of the thickness and the orientation

Abstract This paper presents the fracture behaviour of films of a bioriented poly(ethylene terephthalate) (BOPET), that was studied by the Essential Work of Fracture (EWF) method. The influence of specimen thickness and molecular orientation was investigated. The results show that this method is a useful alternative for studying the plane-stress fracture of this material, finding that the specific essential work of fracture is strongly affected by the orientation [ w e was smaller in the direction of extrusion (MD) than in the perpendicular one (TD)], but independent of the specimen thickness in a range from 50 to 250 μm. On the other hand, the plastic work item is sensitive to variations of thickness but does not depend on orientation.

Using viscoelastic properties to quantitatively estimate the amount of modified poly(lactic acid) chains through reactive extrusion

In this study, the dynamic viscoelastic properties of three structurally modified poly(lactic acid) (PLA) samples processed through reactive extrusion (REX) were analyzed. While classical chromatographic and spectroscopic techniques exhibited limited sensitivity to the presence of topological changes, rheological measurements confirmed the presence of nonuniform branched macromolecules, holding sparsely long chain branches. According to the processing conditions used, the flow activation energy and the thermorheologically simple behavior remained roughly unaffected for PLA-REX containing an amount of modified chains up to 24%. Distinctly separated relaxation processes in a broader transition zone were observed in the complex viscosity function (|η*(ω)|) of all PLA-REX samples. The “extended Carreau–Yassuda” model and an extension of the Havriliak–Negami model, proposed in this work, were used to capture the main characteristics of |η*(ω)| experimental data. Both fitted models were inverted to molecular we...

Essential Work of Fracture of Injection Moulded Samples of Pet and PET/PC Blends

ABSTRACT The fracture behaviour at low strain rates of “amorphous” injection moulded Poly(Ethylene-Terephthalate) (PET) samples (