Polyester films are made of the petroleum substances which are key constituents of polyesters. They find a multitude of uses across various industries owing to their innate properties and advantages. The industries that majorly utilize them are Aluminum Brazing Foil as well as the packaging industry. Packaging industry is actually the major user of these films. Because of their multiple properties of, attractive appearance, strong oxygen barrier, brilliant printing and sealing capabilities and machinability, they are preferred films for food products packaging.
Before referring to metallized version let us understand what is meant by metallized films generally. Metallized films refer to films which are metallized using one end sealable on the other. Metallized films could be manufactured from many different metals like aluminium, chromium and a mixture of nickel and chromium. Their main uses are packaging in food, pharmaceuticals and also the beauty industry. It really is used to produce a various forms of wraps like foils, sheets and scarps. The two types of metallized films are metallized polypropylene films and metallized polyester films.
Metallized polyester films are metallized under high vacuum condition to experience certain desired properties such as a metallic look, making it immune to gases, and less diffusive with respect to aroma and flavor. Another advantageous properties are that they can be shrunk with heat application, may be molded into various forms according to the requirement, are printable, sealable and capable of lamination and extrusion also.
All of these properties of polyester metallized films make them the ideal choice for making aluminium foils used for packaging food items as they need to be resistant to outer gases, but simultaneously need to support the aroma as well as the flavor of the food.
The filler metal (FM) alloys that may be produced as amorphous brazing foils (ABF) are eutectic compositions formed by transition metals such as nickel, iron, copper, etc., in conjunction with metalloids, including silicon, boron and phosphorus. In conventional crystalline state, each one of these materials are inherently brittle and can not be produced in continuous forms like foil, wire, etc. Therefore, these people were available only as powders, pastes, or their derivates. On the other hand, the particular presence of Lamination Foil at or near the eutectic concentration promotes the rapid solidification (RS) conversion of the alloys in to a ductile amorphous foil.
The production of amorphous alloys needs a manufacturing technology that operates on the basis from the necessary cooling rates, which is called rapid solidification, or melt spinning technology. Amorphous structures are seen as a the absence of a crystal lattice or even a long range order. Using this random, spatially uniform arrangement from the gywlyo atoms, their structure is similar to that relating to liquids. The character with this production process is the reason amorphous alloys are given only in the form of thin, ductile metal foils. Subsequently, tapes, parts and preforms can be made by e.g. slitting, cutting, stamping and etching.
Amorphous brazing foils are compositionally a lot more uniform despite crystallization, they melt spanning a narrow temperature range under transient heating. This is a consequence of the shorter distances over which atoms of different elements need to diffuse so that you can form a uniform liquid phase. The resulting instant melting and their superior flow characteristic is just one from the important attributes of ABFs. The lack of the residual organic solvent bases evident in powder paste/tapes correspondingly eliminates soot formation and furnace fouling. The low degree of gaseous impurities in ABFs, due to the specific characteristics of the production technology, is an attractive feature for vacuum furnace brazing.
UABFs can be purchased as strip with a width from .5 mm to 125 mm and a thickness from 20 µm to 50 µm. Preforms can easily be created by using punch and die, cutting/slitting, photochemical etching, and other methods. It is user friendly foils and preforms at automatic production and assembling steps. Using foils and preforms reduces waste and enhances manufacturing efficiency. Drying and evaporation operations, which are required with powder/paste and tape forms, are not necessary. The optimal amount of Color Painted Aluminum can easily be put on the component and, within one heating cycle, ABFs create uniform braze joints of outstanding quality.