Bi-axial orientation

CONTINUOUS PROCESS FOR THE MANUFACTURE OF BI AXIALLY ORIENTED PEN FILM... 

A newer development is the manufacture of bi-axially oriented bottles, in particular for PETP. The pre-form is injection- moulded and rapidly cooled in the mould it remains amorphous (PETP crystallises very slowly) by heating above its Tg (65°) it passes into the rubbery state, and can then be blown-up and, simultaneously, longitudinally stretched. The biaxial orientation thus obtained, accelerates the crystallisation, and, at the same time, results in a very fine crystalline texture, so that a thin-walled, strong, transparent and heat-resistant bottle is obtained. 

Orientation may be obtained deliberately by stretching the melt just before it is frozen mono-axial orientation is important for the production of fibres and filaments, and bi-axial orientation (that is, stretching both lengthwise and transversely to an equal extent) is essential for the qualities required of some... 

Substituents in 2,4-position generaly prefer equatorial orientations in a chair confonnation of the six-membered ring. Bis-axial orientation of these substituents would lead to strong repulsion, but in some examples an axial-equatorial confonnation is observed, as will be disscussed below. The X-ray analysis of the 2,4-diaryl-3,7-dimethyl-l,5-dimethoxycarbonylbispidin-9-one (3) reveals a flattened chair-chair conformation with the aryl substituents, as expected, in the equatorial position. From comparison of the IR-, H-, and NMR spectra with those of the analoguous p-methoxyphenyl- and p-chlorophenyl-substituted derivatives, it follows that these all adopt a double-chair conformation (56). The same behavior was also found for the bispidones 14 and 35 (70) 46-48 and 104 (see Chart 16) (160). The PM3 calculations for various bispidones with aromatic substituents have shown that the cc confonnation is slightly more stable than the cb form, and this is much more stable than the bb conformation in all cases (161). 

Ipelene. [IPEL Ltd.] Polypropylene bi-axially oriented film. 

A common multilayer PP product is bi-axially oriented polypropylene (BOPP), produced on a line including a machine direction orientation unit, and a tenter frame for transverse orientation. This process commonly uses a three-manifold die that allows thin skin layers of copolymer to be applied on either side of a homopolymer base layer. The copolymer is used in this product so the film can be sealed, which is a requirement in packaging applications. Typically, the skin layer thickness is 5% of the total film thickness. The adhesive property of the copol3mier makes it difficult for the film to be processed through a tenter frame, because the film would stick to the tenter frame clips. The multimanifold die can be designed with narrower width flow channels for the skin layers, to keep the adhesive out of contact with the tenter clips, allowing the product to be extruded successfully. 

Figure 13.21 Schematic X-ray diffraction pattern of bi-axially oriented sample, showing only the (00/) direction.

The properties of a BoSPS film are sununarized and compared with bi-axially oriented films of other engineering plastics in Table 13.6. BoSPS has comparable mechanical properties with other engineering plastic films. Outstanding features of BoSPS are the dimensional stability against humidity, electrical properties, and transparency. 

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