Axial stretching

Among the basic mechanical properties of fibers are their deformability and tenacity. When an axial stretching force is applied to the fiber, the principal quantitative indices of deformability are the axial elastic modulus (E)... 

The authors of a very recent work [259] simulated the filler effect by applying an effective tensile stress crz in the direction perpendicular to the direction of the tensile stress aT. To determine erz they relied on the condition of equality of the work of external forces which cause deformation of a unit volume of the composite and matrix subjected to the above-mentioned stresses (asymmetric tri-axial stretching). They came up with a formula of the form ... 

The cylindrical flames should be distinguished from the so-called tubular flames generated by the tangential supply of mixture into a cylinder [2], as the latter are subjected to strong axial stretch controlling their behavior and do not interact with the walls. 

The inflation of the thermoplastic melt causes an orientation of the polymer chains by multi-axial stretching, whereby several mechanically characteristic values, especially the tenacity of the polymer foam, are positively affected. 

Extruded films are sometimes bi-axially stretched, in particular PE and PP films, which gain in strength and transparency by biaxial orientation. The stretching takes place at elevated temperatures, but below the melting point. The edges of the film are gripped by a series of clips, which diverge in the transverse direction and simultaneously accelerate in the machine direction. 

Transmission Electron Microscopy (TEM) has been used to characterize aluminum thin films thermally evaporated (vacuum around 10 4 Torr) on Polyethyleneterephtalate (Mylar) and to correlate the crystallographic structure of the system Al/Mylar and the adhesion of the aluminum films. The adhesion of these films has been measured by a Peel test technique. For the polymer, an amorphous layer (t=12 nm) followed by a crystalline film have been observed on a Corona treated film and the opposite configuration has been found on a bi-axially stretched film. Some spherical precipitation ana interdiffusion zones have also be observed in the Mylar for the films which have the lower coefficient of adhesion (100 g/inch). The main conclusion is the augmentation of the adhesion of the aluminum film as the size of the grains decreases and/or as the microroughness of the Al/Mylar interface increases. 

Metal thin films deposited on polymers are widely used in various industrial domains such as microelectronics (capacitors), magnetic recording, packaging, etc. Despite much attention that has been paid in the recent literature on the adhesive properties of metals films on polyimide (PI)( 1 - 5 ) and polyethyleneterephtalate (PET)((L) it appears that a better knowledge of the metal/polymer interface is needed. In this paper we focus ourself on the relationship between the adhesion and the structural properties of the aluminum films evaporated (or sputtered) on commercial bi-axially stretched PET (Du Pont de Nemours (Luxembourg) S.A.). A variety of treatment (corona, fluorine,etc.) have been applied in order to improve the adhesion of the metallic layer to the polymer. The crystallographic... 

ALUMINUM FILM ONTO NON TREATED BI-AXIALLY STRETCHED POLYMER... 

Figure 1 Morphology and structure of a low adhesion (100 g/inch) aluminum film evaporated on non treated bi-axially stretched PET.(marked is 100 nm)...

Figure 3 "Semi crystalline" skin for the bi-axially stretched film and "Amorphous skin for the corona treated film.(marked is 12.5 nm)...

The main results obtained for the growth kinetics, the adhesion, and the structure and morpholy of aluminum thin films deposited on bi-axially stretched PET films are the following. (l)For a set of experimental conditions (flux, temperature, and polymer surface), the aluminum film is discontinuous up to 10 nm (island formation) and then become continue. The grain size always increases with the thickness of the aluminum Elm as opposeted to the adhesion which remains rather constant. (2)When the aluminum film is continuous and for one thickness of deposition, the adhesion coefficient increases when the grain size decreases. (3)We found an increase of the adhesion coefficient when the skin of the polymer is "semi-crystalline and when the polymer is pretreated with a corona discharge. (4)The best results (for the adhesion of Al/PET) are found for a polymer treated in a fluorine atmosphere and when the deposition of the aluminum on polymer is done by sputtering. 

For the 2 molecules CIF3 (3.10) or BrF3, there are six normal modes of vibration, approximately described as equatorial stretch, S5Tnmetric axial stretch, asymmetric axial stretch and three deformation modes. All six modes are IR active. 

FIGURE 39.3 Schematic illustration of three types of film response (a)elastic half-space behavior, dominated by bulk compression of the film, (b) plate behavior, dominated by bending deformation of the film, and (c) membrane behavior, dominated by axial stretching of the film. 

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