Structural Evolution of Two-Phase Blends of Polycarbonate and PMMA by Simultaneous Biaxial Stretching

We investigated the structural evolution of the two-phase blends of polycarbonate (PC) and poly(methyl methacrylate) (PMMA) at various blend compositions by simultaneous biaxial stretching, using optical microscopy and SEM observation. The spherical PMMA domains and PC matrix of 30/70 PC/PMMA were enlarged uniformly at the all in-plane direction, while the anisotropic-shaped co-continuous structure in 50/50 PC/PMMA was deformed to a crosshatched structure by the in-plane bimodal orientation. In 70/30 PC/PMMA, the phase inversion was found to occur by simultaneous biaxial stretching; that is, the spherical PMMA domains were changed to a crosshatched matrix by the in-plane bimodal orientation due to coalescence of the PMMA domains during the stretching. Owing to the phase inversion, the surface hardness estimated by the pencil hardness test became harder, from 2B to 2H, increasing the strain from 1.0 to 2.0.

A simple constrained uniaxial tensile apparatus for in situ investigation of film stretching processing

A simple constrained uniaxial tensile apparatus was designed and constructed to obtain stress-strain curve during stretching and subsequent structural evolution of polymeric films. Stretch is carried out through two motor driven clamps in the machine direction and scissor-like clamps in the transverse direction keeping the sample width constant. The force information during film stretching process is recorded by a tension sensor and structural evolution can be obtained by in situ X-ray scattering technique. All parameters related to film stretching manufacturing, such as temperature, draw ratio, and stretching speed can be set independently, making the apparatus an effective method to explore the relationship between processing parameters and structure.

The Prediction of Bowing Distortion of Film after Transverse Stretching with Consideration of Heated Air Flow in a Tenter

The bowing distortion of polypropylene (PP) film during transverse direction (TD) stretching with a tenter was newly predicted with consideration for heated air flow. The distribution of the heat transfer coefficient on film was calculated by the results of air flow analysis in the tenter in order to obtain a more realistic heat transfer condition than in previous works based on an impinging jet model and a wall jet model. Bowing distortion after stretching was calculated by applying the distribution of heat transfer coefficient obtained from air flow analysis under the assumption that the deformation of film obeys an elastic-plastic rule. Another bowing distortion was also calculated by applying an impinging jet model and a wall jet model in order to evaluate the applicability of the distribution of heat transfer coefficient obtained from air flow analysis. The authors experimentally measured the bowing distortion and the film thickness after stretching using a pilot plant. It has been shown that the calculated results based on the distribution of heat transfer coefficient obtained from air flow analysis are closer to the experimental results than previous works based on an impinging jet model and a wall jet model, particularly at faster line speed. It is revealed that the distribution of heat transfer coefficient has a strong influence on the temperature of film, and the difference of the predicted temperature causes a difference in the thickness change in film and longitudinal stress. The authors concluded that the difference in thickness change in film and longitudinal stress brought about the difference in bowing distortion.