Uniaxial drawings

This stretching, similar to the drawing of fibres, which promotes orientation and crystallite formation, is called biaxial orientation. It gives the film added strength and gas-barrier properties. In some processes, monoaxial (uniaxial) drawing is employed, e.g., polypropylene, which is then slit into thin strips and fabricated into heavy duty sacks, carpet backing, etc. The stenter process is used to make biaxial oriented poly(vinylidene dichloride) ("ding" film), polyester, polyamide and polypropylene films. 

Uniaxial drawing in low VF2 content samples causes not only a molecular orientation of the material, but also a transformation of the Fnf phase into an... 

A fibrous specimen was obtained by stretching the swollen film uniaxially (draw ratio 3.5 1). The center of the fiber diagram of the wet, fibrous specimen (Fig. 6A) has a cross-like appearance that suggests a simple helical structure for the molecule. 

Figure 7. A. Schematic of an elliptic flaw initially at right angles to the draw direction. For a uniaxial draw, the draw ratio D = at. At a critical draw ratio D = I/R the ellipse becomes circular. For higher draw ratios (D > I/R), the ellipse forms with a 90° change in its orientation. B. Schematic of the effect of increasing draw ratio on an ellipse initially at some angle other than 90° to the draw direction. C. A general biaxial draw (al9 a2) acting on an ellipse at initial orientation pto the, major drawm direction (a. > as).

Porter, R.S. Kanamoto, T. Zachariades, A.E. Property opportunities with polyolefins a review. Preparations and applications of high stiffness and strength by uniaxial draw. Polymer 1994, 35, 4979. 

Uniaxial drawing of polymer samples introduces a uniaxial distribution of molecular orientations which often can be approximated by a Gaussian. The NMR spectrum then depends on the angle between the drawing direction and the magnetic field. For example, the spectrum of unoriented FIFE is well approximated by a symmetric powder pattern (Fig. 10.3.1(a), cf. Fig. 3.1.3), while the spectrum of a uniaxially oriented sample exhibits two peaks when the direction of molecular order is parallel to the magnetic field (Fig. 10.3.1(b)) [Hepl]. 

Fig. 14.10. C CP NMR spectra of carbonyl carbon-labeled uniaxially draw (x3 at 45°C) PET film as a function of /3u, the angle between the draw direction and the magnetic field. Solid and dotted lines show observed and calculated spectra, resp>ectively. The fractions of the two components, amorphous (35%) and oriented (65%) were determined computer simulations of the observed NMR lineshapes. The structural parameters ap = 90°, /3p = 18 6° with the distribution of the fiber axis p = 22° were found to be characteristic of the oriented component.

The most significant changes in extended trans-content occur with samples in this uniaxial draw ratio range. In addition, the conjugated system... 

Fig. 14.12. CP NMR spectra of carbonyl carbon-labeled uniaxially draw (x5 at 80°C) PET film after heat treatment at 170°C. 8l is set as 0 and 90°. Full and dotted curves show observed and calculated spectra, respective y. The fractions of the three components, amorphous (30%) and two oriented ones (35 and 35%), was determined by simulation. The structural parameters were ap = 90°, ySp = 20 10° and p = 8° (low oriented component) and ap = 90°, )3f = 11 5° and p = 2° (high oriented component), respectively.

Figure 6. Failure time under UV exposure vs. uniaxial draw ratio of LDPE.

Draw a sketch showing the effect of increasing uniaxial drawing upon the X-ray diffraction pattern produced by the (200) plane in polyethylene. 

PET Real-time T and WAXS Uniaxial drawing following by taut annealing 1076... 

Uniaxial drawing At 2°C for PHB-rich blends (close to PHB s T ) or 60°C for PLLA-rich blends ... 

Film preparation by different techniques, such as extrusion, uniaxial draw-down and mandrel processing, has been explored by Aoki et al. [208] and Bodaghi et al. [209]. The uniaxially oriented Pp A films obtained by the drawing-process exhibit highly anisotropic mechanical properties, whereas the mandrel-produced films show balanced properties. However, they found that the values for modulus and strength of these films are much lower than those obtained for fibers. 

The use of Small-Angle Neutron Scattering (SANS) has been exponentially increasing for the study of polymers, largely of elastomers and nanopolymers, for the last 40 years [198]. Matsuba et al. [199] worked on an isotropic blend of deuterated PE and hydrogenated polyethylene (HPE 3 wt%) during uniaxial drawing at 125°C to understand the formation mechanism of the shish kebab from the isotropic film. In the early... 

G. Matsuba, C. Ito, Y. Zhao, R. Inoue, K. Nishida, T. Kanaya, In situ small-angle X-ray and neutron scattering measurements on a blend of deuterated and hydrogenated polyeth-ylenes during uniaxial drawing. Polymer Journal 45 (3) (2013) 293-299. 

MAXIMUM PROPERTIES ACHIEVED BY UNIAXIAL DRAWING OF HIGH MOLECULAR WEIGHT POLYOLEFINS... 

Heimenz PC, Lodge TP (2007) Polymer chemistry, 2nd edn. CRC, Boca Raton Hiss R, Hobeika S, Lyrm C, Strobl G (1999) Network stretching, slip processes, and fragmentation of crystallites during uniaxial drawing of polyethylene and related copolymers. A comparative study. Macromolecules 32 4390 1403... 

The situation changes in the case of solid-phase (semicrystalline) polymer uniaxial drawing. As the experimental estimations shown [5], the Poisson s ratio value for initial pol5aneric materials (componors UHMPE-Al and UHMPE-bauxite) v 0.36 and for these materials extmdates with draw ratio X > 3-v 0.43. From the Eq. (14.3) it follows that A 0.857. This means componors volume obligatory increase, expressed in cracks formation on interfacial boundaries pol5nner matrix-filler [3] ... 

As it was noted above, the value A is always larger or equal to zero. This means, according to the Eq. (14.6), solid-phase polymeric material structure fractal dimension increase at uniaxial drawing, which is confirmed experimentally [5, 7]. 

Kurose, T., Urman, K., Otaigbe, J.U., Lochhead, R.Y.,and Thames, S.F. Effect of uniaxial drawing of soy protein isolate biopolymer films on structure and meehanical properties. Polym. Eng. Sci., 47, 374-380 (2007). 

Solid-solid transitions from a modification to others have been observed. In fact, P4MP1 is found [102] to exhibit changes in crystal modification on uniaxial draw. In particular He and Porter [103] report that the crystal structure at lower planar zigzag (2/1) draw ratio is a common tetragonal form and that at higher draw it is orthorhombic. 

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