Quantificação da influencia da composição de terpolimeros de polietilenotereftalato nas propriedades termicas, na morfologia e no comportamento de deformação, durante o sopro

AUTOR(ES)
DATA DE PUBLICAÇÃO

2002

RESUMO

PET terpolymers properties were never determined in a complete way. quantification of the relationship between the molecular weight and the comonomers content is practically inexistent. The objective of that study is, starting from 14 different PET terpolymer types, to quantify the thermal properties of stretching and the morphologic structure formed during the blowing of bottles through the stretching-blow process. For the thermal characterization of the polymers, differential scanning calorimetry (DSC) was used, in isothermic analyses of dynamics the processing of polymers was made through blow in laboratory (blow without mold) and blow in industrial machine. For the characterization of the produced bottles, a density gradient column (apparent density), helium picnometry and mercury porosimetry (absolute density), infrared spectroscopy (cristalinity and orientation), thickness and oxygen permeation ratio through the overall packaging. In a general way, one can say that the molecular weight (Mn) I di-ethylene glycol ratio, governs great part of the thermal properties of stretching and of porosity, in the studied samples. The activation energy for crystallization during cooling was determined, DEG is an exact opposite to the molecular weight (Mn), for the properties of stretching of PET. A morphological model to represent the wall of a bottle PET was proposed. This model makes an analogy between the wall of the bottle and an asymmetrical membrane, In both cases, exists a structural variation along the thickness, In the bottle, on one side of the wall there is a compact and homogeneous structure on the other side a porous structure and with structural defects. The size of the structures formed inside the wall is function of the processing temperature and is apparently independent on the polymer formulation. The formation of pores and structural voids in the wall of a bottle due to the tests carried out, were not function only of the processing conditions or of how much above the glass transition temperature the material was. Apparently, the composition of the polymer itself has influence in its tendency to form pores. In this sense, there is a strong interaction between molecular weight (Mn) and tenor of DEG. Two special analysis types were developed. One of them allows the visualization of the permeability to the oxygen in certain areas of a bottle with no need to destroy the bottle. In the second technique it was developed a composition of colors that allows to reveal structural differences. 80th techniques can be valuable in research and control of production of bottles. For this study includes several aspects related to the properties of PET terpolimers, it is of significant importance in the whole processing chain, from the preforms injection, to the blow of bottles and the properties of the final product

ASSUNTO(S)

containers polimeros - propriedades termicas morfologia plasticos na embalagem garrafas plasticas - industria

ACESSO AO ARTIGO

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