Quantitative characterization of deformation in polypropylene fibers (original) (raw)

1968, Journal of Polymer Science Part A-2: Polymer Physics

The submicroscopic morphology of uniaxially deformed isotactic polypropylene films has been examined by small-angle light scattering (SALS), electron microscopy, optical microscopy, small-angle x-ray scattering (SAXS), wide-angle x-ray diffraction, birefringence, sonic modulus, and density methods. Several new interpretations and extensions of existing theories are developed and verified experimentally as follows. (I) The V , SALS pattern is shown to be a new tool for the identification of the sign of the birefringence of spherulites too small to be seen in the optical microscope. The theoretical dependence of the V , SALS pattern is developed and verified experimentally with patterns from isotactic polypropylene, polyethylene, Penton, nylon 6,6, poly(ethy1ene terephthalate), and nylon 6,lO. (2) Intraspherulitic lamellar behavior during deformation can be identified from the SAXS pattern. This includes quantitative evaluation of the long spacing between lamellae and their average orientation. (3) The two-phase sonic modulus theory is valid over the wide range of deformations, crystallinities, processing temperatures, and molecular weights used in this study. The deformation of isotactic polypropylene films drawn a t 110 and 135°C. has been characterized quantitatively in terms of an integrated picture of m&s movement on all morphological levels: the molecular, the interlamellar, and the spherulitic. At both temperatures, the spherulites deform affinely with extension, whereas the deformation mechanisms within the spherulite depend on the location of the radii with respect to the applied load. During spherulite deformation, lamellar orientation and sep@ration processes predominate, whereas a t high extensions, fibrillation occurs and crystal cleavage processes predominate. The noncrystalline region orients throughout the draw region. At 135'C. non-orienting relaxation processes appear in the noncrystalline region which retard the rate of molecular orientation with extension. QUANTITATIVE CHARACTERIZATION OF DEFORMATION 1103 nylon 6,6 (Du Pont Zytel 101) produced positive spherulitic film by a treatment similar to that applied to poly(ethy1ene terephthalate). Negative spherulitic nylon 6,G film wsls prepared from dried polymer by fusion in a press at 500°F. for 1 min. at atmospheric pressure, then 1 min. at 900 psi, slow cooling under pressure for 10 min. to 4G0°F., and subsequent cold water quenching. Positive spherulites of nylon 6,lO (Du Pont Zytel 31) were prepared in a press by fusion for 2 min. at 440°F. with subsequent slow cooling from the melt under 1000 psi pressure for 10 min. Negative spherulites of nylon G,10 were prepared by fusion for 2 min. at 440°F. and subsequent room-temperature quenching. Solution Grown Spherulites. Three-dimensional spherulites were grown from Pro-fax 6601 flake. Negative spherulites, 2-5 p in diameter, were obtained by heating a 1% solution of the Pro-fax in p-xylene for 10 min. at 130°C. and then quenching the solution in a bath of Dry Ice and methylene chloride. Positive spherulites, 12-15 p in diameter, were obtained by heating a 15% solution of Pro-fax in a 70:30 mixture (by volume) of xylene and butyl Cellosolve at 134°C. arid then allowing the solution to cool Density slowly. Densities were measured in a 3A alcohol-water density-gradient column at 23.2 I 0.1"C. Wide-Angle X-Ray Diffraction These measurements were made with a Phillips diff ractometer equipped with a copper target, nickel filter, and a scintillation counter detector system. The measured intensities were corrected for polarization, absorption, background, and incoherent scattering. Calculations were made on an SDS 920 computer. Small-Angle X-Ray Scattering (SAXS) Small-angle x-ray scattering patterns of films were obtained with a W. H. Warhus vacuum camera equipped with 0.025411. pinholes. Nickel-filtered copper radiation was used, and the diffraction pattern was obtained at a sample-to-film distance of 29 cm. Birefringence Film retardation was measured in a Zeiss polarizing microscope at a wavelength (A) of 546 mp. Both quartz and calcite Ehringhaus compensators were used to measure the retardation. Thickness measurements were made with a Pratt and Whitney Electro-Limit Gage. Sonic Modulus An H. M. Morgan Company, Inc., pulse propagation meter, PPM-5 was used to determine the sonic modulus from film strips 1 111111. wide and 15-25