Stretchability Of Films Research Articles

Synthesis and characterization of stretchable isoprene-acrylic acid copolymer thin films

Copolymer thin films of isoprene with acrylic acid were synthesized using PECVD. In that way, the stretchable functionality of polyisoprene (PI) was combined with the hydrophilic functionality of poly(acrylic acid) (PAA) to obtain stretchable thin films with adjustable wettabilities. Deposition rates were found to change between 9 and 5.5 nm/min depending on the monomer flowrates. The analysis of water contact angle (WCA) values indicated that films having more AA units in their structures were more wettable. The stretchability of the films was assessed on laboratory gloves through stretch-release test and on PET sheet through bend-release test. No significant changes in the WCA values with no observable cracks and failures after successive tests were indication of stretchability of the copolymer films.

BIAXIAL DEFORMATION OF SPHERULITE AND MULTI-LAYER STRUCTURE IN THE BIAXIALLY STRETCHED POLYPROPYLENE FILMS

In this report effects of spherulite size and of various stretching processes on the characteristics of the deformation and fracture of polypropylene spherulites were investigated at both the room and higher temperature in connection with the stretchability of films. The exfoliatical property of biaxially stretched film is discussed in terms of spherulite deformation.Film containing spherulite of various sizes were prepared by hot-press technique under the various cooling conditions. These films were stretched with the film-stretcher, in the open bath or the hot-air bath. The following stretching methods were adopted: uniaxial stretchings under the free or constant width, and two-way successive or simultaneous biaxial stretchings.The biaxial stretchability is higher in the films with small size spherulites than in the films with large size.The deformation and the fracture mechanisms of spherulite could be phenomelogically classified as follows: (1) brittle break-down, (2) fracture with the cleavage of interfacial boundary, (3) uniaxial plastic deformation, (4) deformation with necking, (5) deformation with pleating, (6) deformation into fibril structure, and (7) biaxial plastic deformation.The characteristis of the deformation and the fracture of spherulites are summarized in Table 1.We have deduced that the appearance of exfoliatical property as mica was owing to the multilayer structure of the spherulite and the planar orientation of molecular chains and crystalls in the film.