PEN/PET blends

Figure 20.3 Polarized micrographs of the PHB/PEN/PET blends for various compositions (mol %)...

Figure 20.4 The melting temperature ( ) and melting enthalpy ( ) as a function of PEN content for the PEN/PET blends...

Figure 20.7 The effect of pre-heating temperatures and blend composition on the melting temperatures of the PHB/PEN/PET blends , 260°C O, 280 °C A, 300 °C...

Figure 20.9 The 1H-NMR spectrum at 300 MHz, showing the assignments of the absorptions for the PHB/PEN/PET blends dissolved in cf-trifluoroacetic acid [21]. From Kim, S. H., Kang, S. W., Park, J. K. and Park, Y. H., J. Appl. Polym. Sci., 70, 1065-1073 (1998), Copyright (1998, John Wiley Sons, Inc.). This material is used by permission of John Wiley Sons, Inc...

The log G versus log G" plots of the various PHB/PEN/PET blends are presented in Figure 20.16, where and the slopes of the plots are measures of the homogeneity of the system [35], If the slope is zero, then the blend system is heterogeneous, and if it approaches 2, it means that the blend system is tending to a homogeneous system. The slopes of the plots in Figure 20.16 increase with the addition of excess PHB to the blend system. 

The EDA approved PEN for food contact appiications in Aprii, 1996. PEN and PET can be blended together to make useful materials, and also PEN/PET copolymers can be produced. When PEN/PET blends are used, one is really making copolymers in the extruder. Analysis of the material that is extruded shows that transesterification reactions occur in the extruder, forming molecular bonds between PET and PEN molecules. Therefore, processing conditions are important to the quality of product one makes when using blends. Blends, as well as copolymers manufactured by polymer suppliers, can open up markets for this polyester that are not accessible to PEN alone because of its high price. While these materials have not yet been approved for food contact applications in the U.S., there appear to be no technical barriers to their approval. 

S. L. Schmidt, B. Lynch, and A. S. Agrawal. Process for making PEN/PET blends and transparent articles therefrom. US Patent 6 586 558, assigned to Continental PET Technologies, Inc. (Florence, KY), July 1,2003. 

The effects of the interchange reactions on the viscoelastic behavior of binary blends based on PET, PEN, and their nanocomposites have been studied [80]. With an increase in the number of extrusion runs and mixing temperature, the extent of reaction and the degree of randomness both increased, whereas the average sequence block length values decrease. The addition of nanoclay inhibits the transreactions in the PET/PEN blends. The addition of PEN into the PEN/PET blends enhances the storage modulus, loss modulus, and complex viscosity. A significant increment in the viscoelastic properties was observed in the presence of nanoclay. 

Other food packages include polyethylene naphthalate (PEN) and PEN-PET blends as high-barrier films or rigid containers. 

The principal applications of PEN and PEN/PET blends and copolymers are as films (see Polyester Films). 

---