Stretching machine

Re and Rty of films at 589 nm were measured using film stretch by 10% at 230-280°C using an automatic biaxial stretching machine. Film thickness was assayed at any three points by means of a digital micrometer and an average value reported. Testing results are provided in Table 2. 

The strain dependence of electrical resistivity was carried out on strips (size 40 mm x 6 mm x 0.3 mm) stretched with a manual stretching machine. The film under study is clamped between the jaws of the stretching machine and two copper plates attached to the jaws of the machine are connected to the high-resistance meter (Figure 12.8). 

The stretching mechanism of an equal biaxial stretching machine was modified. Tests with plasticised PVC showed that the machine could produce oriented sheets under different stretching modes - uniaxial (constant width), simultaneous (equal and unequal) biaxial and sequential. If plasticised PVC was biaxially oriented to the same draw ratios by different stretching modes, similar enhancements of mechanical properties occurred. 12 refs. 

A great number of devices have been constructed in order to perform certain treatments on the sample, while simultaneously the X-ray scattering is registered. Examples are furnaces, stretching machines, cells for chemical reactions, cryostats... 

Draw ratio of two-step drawing at room temperature by a stretching machine... 

Fig. 1. Film stretching machine (1) FTIR detector, (2) pneumatically rotatable pt rizer unit, (3) clamp, (4) polymer film sample, stress transducer, (6) displaconent transducer, (7) driving motor, (8) heating accessory, (9) cartridge heater, (10) temperature control, (11) KBr window, (12) specimen preparation and transfer device...

The majority of results so far available in this Held have been derived from spectra recorded on dispersive instruments. In order to test tl validity of Eq. (1) several independent experiments have been performed in which a highly oriented polyethylene terephthalate film is subjected stepwise to increasingly higher stresses in the stretching machine illustrated in Fig. 1 and FTIR spectra are taken at the relaxed stress levels with unpolarized radiation. In Fig. 4 the wavenumber shifts of the v(0—CH2) absorption band are plotted as a fimctimi of the applied stress for different experiments. From these systematic investigations, however, no linear relationship between the wavenumber shift Av and the plied stress good index of determination (0.98) was obtained for the power function ... 

Figure 2-44. (a) Principle of rheo-optical FTIR spectroscopy of polymer films, (b) Variable-temperature stretching machine for rheo-optical FTIR and FT-Raman spectroscopy. (A) stretching machine (B) sample transfer mechanism (1) stress transducer (2) strain transducer (3) film sample (4) sample clamps [17, 18]. 

In a classic work of Rivlin and Saunders [10] on vulcanised rubber, a strain energy function of the form U h, h) was introduced. Experiments were performed on sheets of material in plane stress with the in direction normal to the plane. Homogeneous deformations were applied using a biaxial stretching machine so that the principal extension ratios 7-1 and kii were under experimental control. Incompressibility applies and Equations (3.55) give the principal stresses... 

The extraordinarily informative value of images derived from polarization spectra was demonstrated with a PHB/PLA 50/50 wt% blend film that had an original thickness of 27 p.m and had been elongated at room temperature to 50% strain in a miniaturized, computer-controlled stretching machine (Figure 22.11a). 

P(3HB-co-8%-3HV) fiber was prepared by one-step-drawing procedure of amorphous fiber with small crystal nuclei at room temperature. Amorphous fibers were obtained by quenching of the melt-spun fibers of P(3HB-co-8%-3HV) into ice water. Isothermal crystallization of amorphous P(3HB-co-8%-3HV) fibers was held in ice water for a certain period to prevent rapid crystallization and to grow small crystal nuclei. One-step-drawing after isothermal crystallization was performed by the stretching machine at room temperature, and then annealed at 60 °C for 30 min in an autoclave for fixing the extended polymer chains. One-step-drawn fibers with isothermal crystallization for 24 h were opaque and maximum total draw ratio was ca. 10 times. 

A series of experiments on polystyrene has recently been performed in our laboratory. The fluorescence polarization measurements were carried out during the stretching using the optical equipment shown in Fig, 3, adapted to a stretching machine specifically designed (14) for this purpose and represented in Fig, 4, This machine operates at constant strain... 

Fig. 4 - Stretching machine and temperature controlled chamber P, double hydraulic plunger S, servovalve RS, resistance sensor ...

As described here above, fluorescence polarization can be applied to uniaxial mobile systems. Such measurements have been performed in our laboratory during stretching of polyisoprene networks (20), using the optical equipment shown in Fig. 3 adapted to a stretching machine operating at constant cross-head displacement. 

Tensile testing is done in a home-made [1] stretching-machine. The machine performs symmetric drawing in order to maintain the position of the beam on the sample. Signals from load cell and transducer are recorded during the experiment. The macroscopic deformation is determined close to the beam position to ensure accurate comparison of the mechanical data with the nanostructure evolution. For this reason a precise method has been developed [2]. In this method a pattern of fiducial marks is stamped on the sample. The sample is monitored by a TV-camera. Using the fiducial marks the local strain s = - o)/ o is computed automatically... 

Principle of rtieo-optical F-IR spectroscopy (a) and miniaturized stretching machine (b). A, stretching machine B, sample preparation/ transfer mechanism 1, stress transducer 2, strain transducer 3, polymer film sample 4, clamps. 

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