Oriented polypropylene metallized

Materials. Biaxially oriented polypropylene (PP) films of 50 um thickness were obtained from 3M and have been described (2). PMDA-ODA (PI) was Kapton H polyimide from Dupont. Copper-plated PTFE films were obtained from Spire Corporation (Bedford, MA). They were prepared using the Ion Beam Enhanced Deposition (IBED) process in which a 100 nm thick Cu film was vapor-deposited onto a PTFE substrate in the presence of a beam of 400 eV Ar+ ions of 25 uA/cm2 (IQ). Shortly before SIMS analysis, the Cu film was removed slowly by peeling at 90° in ambient conditions. Metal-coated PI films were prepared by sputtering 50 nm Cr and 1 um Cu onto a 50 um thick Kapton film on both sides. Thermal annealing was performed in a vacuum chamber at 2xl0 6 torr using a quartz lamp as the heating source. The samples were held for 15 min at the desired temperature and then cooled down to ambient temperature inside the chamber for about 2 hours. Just prior to SIMS analysis, the metal films were peeled slowly at 90° and then immediately introduced into the vacuum chamber of the instrument. 

Metallyte. [Mitsui Petrochemicals] One side coextruded oriented polypropylene film, one side metal, heat salable high opacity film for laminaticxis. 

Quantum Performance Films. [Quan-tumAJSI] Polypropylene film biaxi-ally oriented and metallized films. 

Bars and stick products are flow-wrapped. The printed wrapping, which may be coated paper, orientated polypropylene or metallized film, is supplied as a long roll. The wrapping is unwound from the roll and made into a continuous tubular sleeve (Figure 5.17a). Products are placed in the sleeve (Figure 5.17b), which is heat or pressure sealed along its seam. Finally, the tube is cut across to separate the products and the ends of the wrapping are sealed. 

Vacmet Packagings (India) Metallized polyester and BOPP, biaxially oriented polypropylene, films... 

Large volumes of polymer films are commercially vacuum metallized with aluminum every year and the metallization of roll substrates such as polyester, nylon and oriented polypropylene films for packaging applications are wide spread. In addition the metallization of paper is principally a decorative application where holographic or iridescent patterns are intensified by the reflective metal layer. The barrier properties of the aluminum layer are controlled by the base sheet onto which the aluminum is applied but also by the deposition process. In general the films are metallized to add a significant light barrier and to enhance the moisture and perhaps oxygen gas barrier properties of the film. Metal adhesion is also a primary concern. 

Polypropylene is used in battery cases and in the replacement of metal parts in automobiles. It is also widely used in consumer products, eg, kitchen wares, trays, toys, and packaging materials. Its future appHcations are expected to include an increased portion of the fibers and filaments markets, especially for continued growth in carpet backing and carpet face yams. Film, both oriented and unoriented, is also expected to be a significant growth market for polypropylene. 

It is in the stereospecific polymerization of propylene that metallocene complexes display their astonishing versatility. Commercial Ziegler-Natta catalysts for isotactic polypropylene - based on combinations of TiCU, MgCl2, Lewis bases and aluminum alkyls - depend on a metal-centered chirality which exists at specific edge and defect sites on the crystal lattice to direct the incoming monomer in a particular orientation. These catalysts produce small amounts of undesirable atactic material due to the presence of achiral active sites. 

Certain soluble catalysts polymerize propylene to highly syndiotactic polymers that are free of the isotactic form. Natta, Pasquon, and Zambelli (7 8) showed that VCl (or vanadium triacetylacetonate) in combination with AlRnX-type metal alkyls and anisole, polymerize propylene to highly syndiotactic polypropylene. These apparently homogeneous catalysts were used at low temperatures (-40 to -78 °C). Stereochemistry was initially explained by a mechanism involving repulsion between the methyl groups on the last added and new monomer unit to achieve orientation (83. 84). 

Polymers are not the only materials that can exhibit orientation. Any polycrystalline material, such as a metal, can exhibit orientation and this can confer desirable or undesirable properties on the material. The effects are, however, often much greater for polymers than they are for other materials. Table 10.1 compares the effects of the forging of steel and the extrusion of polypropylene. In addition to the other changes shown in table 10.1, the elongation that takes place before breaking occurs, often called the elongation to break, is substantially reduced for the polymer. 

Industrial applications of metallocene catalysts are a recent development AU of them possess in their reaction center two aromatic rings, between which a complex bond holds a metal atom, in most cases zirconium. This type of catalysis produces polymers with exceptionally uniform structures. The chain lengths of the individual molecules closely approximate one another. The spatial structure is therefore well-defined. Polypropylene, for instance, is completely isotactic. It is even possible to produce polypropylene in which the pendant group orientation alternates between right and left. The resulting substance is known as a syndiotactic polypropylene (see above) [3]. 

A key step in metal-induced olefin polymerization has the olefin tt face complexing to the metal center. The two faces of the propylene double bond are enantiotopic. Isotactic polypropylene forms when only one face of the propylene monomer consistently reacts to make polymer. Thus, a chiral catalyst is needed to distinguish enantiotopic faces of an olefin. But, how do we ensure that only one face reacts It is a complicated problem, because when an olefin like propylene complexes to a metal center in a typical chiral environment, not only will both faces complex to some extent, but many orientations are possible for each complex. This leads to many different reaction rates, and a mixture of Stereochemistries. A key to the solution, then, was to develop a catalyst that is chiral but not asymmetric. In particular, the C2-symmetric metallocene shown below was prepared. The metal is chirotopic but non-... 

For the growth of isotactic polypropylene chains and higher polyolefin chains at the chiral coordination sites of ansa-metallocene catalysts, the following explanation is now firmly established [11,12] Formation of the new C-C bond requires that the a-olefin substituent and the C(a)-C(P) bond of the metal-bound polymeryl chain are oriented anti to each other along the incipient C-C bond, while the C(a)-C(P) chain segment must reside in an open quadrant of the chiral metallocene coordination site. The latter is thus considered to control the enantiofacial orientation of the a-olefin in the insertion transition state TS (Fig. 4) by way of the C(a)-C(P) chain-segment lever . 

---