Effect of formulation variables on polymer properties: I. Deepdraw of the epoxy based coatings. II. Oxygen barrier of poly(ethylene terephthalate)

Deformation of the metal substrate in the deep drawing process was characterized by macroscopic appearance and strain distribution. The results of the analysis were correlated with coating failure. Stopping the forming process at intermediate positions before the cup was completely formed revealed different stages during drawing. Two failure modes were observed on the deep drawn cups. Mode I coating failure, coating delamination at the cup edge, correlated with residual compressive stresses in the deep drawn coatings. Residual stresses were strongly affected by the amount of wax in the coating formulation. Some of the coatings that exhibited mode I failure also exhibited mode II failure. Loss of adhesion on the cup wall, mode II failure correlated with adhesive strength of the coating to the metal substrate, which in the present study was most strongly affected by crosslinker concentration.; The oxygen barrier properties of amorphous poly(ethylene terephthalate) [PET] based copolymers with various acid comonomers were examined. The diffusion and solubility coefficients depended on copolymer composition in accordance with static and dynamic free volume concepts of gas permeability in glassy polymers. The solubility coefficient S correlated with the amount of free volume as determined by Tg. Correlation of the diffusion coefficient D with the magnitude of γ-relaxation identified dynamic free volume with thermally activated segmental motions. Correspondence in activation energy confirmed the relationship. The effect of comonomer on D correlated with the intensity of the gauche component of the sub-ambient γ-relaxation. Changes in the fraction of gauche glycol conformations resulting from copolymerization were confirmed by FTIR.; The effect of crystallization on the oxygen barrier properties of PET based copolymers with up to 10 mol% isophthalate, phthalate or naphthalate was examined. Systematic changes in crystallinity made it possible to test free volume concepts in which permeation of a small gas molecule through a semicrystalline polymer is viewed as proceeding through the amorphous regions with an increased tortuosity imposed by crystallites. Increasing the isophthalate, or phthalate content reduced the dedensification effect and 10 mol% of these comonomers was sufficient to eliminate the effect altogether.