Polypropylene film-casting

Lamberti, G. and V. Brucato. (2003). Real-Time Orientation and Crystallinity Measurements during the Isotactic Polypropylene Film-Casting Process, Journal of Polymer Science Part B Polymer Physics, 41 998-1008. 

Some cast (unoriented) polypropylene film is produced. Its clarity and heat sealabiUty make it ideal for textile packaging and overwrap. The use of copolymers with ethylene improves low temperature impact, which is the primary problem with unoriented PP film. Orientation improves the clarity and stiffness of polypropylene film, and dramatically increases low temperature impact strength. BOPP film, however, is not readily heat-sealed and so is coextmded or coated with resins with lower melting points than the polypropylene shrinkage temperature. These layers may also provide improved barrier properties. 

Cast films provide a high clarity, heat sealable film and are primarily used as an overwrap for boxes and other packaging. These films have a lower density than cellophane and provide a longer product shelf life. Properties of polypropylene films are given in Table 12. 

Table 11.5 Comparison of cast, monoaxially oriented and biaxially oriented polypropylene film ...

An important application for polypropylene is film tape. This is made by slitting unoriented film (cast or blown) into tapes 2 or 3.5 mm wide and stretching under heat about seven-fold. With cast film the orientation is more completely monoaxial and there is a tendency for the film to split along its length (fibrillate). Tubular film does not self-split so easily and also has a somewhat softer feel. Such tapes may be woven into sacks and these have... 

Polypropylene film is found in a variety of applications. Films are thin plastic sheets with thicknesses less than 250 pm. Applications for these films include candy mappers, plastic label material, electrical capacitors (which requires very pure polymer), and fiber glass insulation backing. There are two general categories of polypropylene films unoriented and oriented. Films are manufactured through either a cast or a blown film extrusion process. Oriented films exhibit improved strength relative to unoriented films. This means that they can be... 

Rank the following polypropylene conversion processes in terms of their relative sensitivity to particulate contamination, film casting, injection molding or fiber spinning. 

The Treofan Group is a manufacturer of biaxial oriented polypropylene film (BOPP) and cast polypropylene film under the brand name Treofan. The company also manufactures PLA film under the brand name Biophan. 

Film Processing Method Polypropylene film can be cast or blown.i ... 

The objective of this chapter is to study the absorption and reflection of infrared light by the uncoated and A1 coated surfaces of polymier films using transmission and reflection techniques. For this purpose two commercial biaxially oriented polypropylene film, a cast polypropylene film, a milk cover and a chocolate coating material with their one surface coated with a thin aluminum layer were examined by irrfrared spectroscopy. One surface of the each film was coated with a thin aluminum layer. 

FIGURE 1.3 SEM pictures of (a) fractured A1 coating on the cast polypropylene film (b) A1 coated surface of the polypropylene film. 

Left property changes in cast polypropylene films as a function of annealing time [593]... 

Another example is that of polypropylene film produced on a cast film line. Its optical properties can change considerably by changing line conditions such as die temperature and chill roll temperature. Line speed affects cooling time and is therefore important too in affecting optical properties. All those conditions affect the development of the crystalline structure of the film, which in turn is related to its optical properties. Random copolymers of PP will have better optical properties than homopol3miers, because of their inherently lower crystallinity. 

Cast film extrusion is used in manufacturing polypropylene films and requires greater surface pretreatment power density (possibly 2-3 times) compared to other polyolefin films. With blown film extrusion processes, polyethylene films are typically used and require pretreatment on both sides. Considerable amounts of slip additives, used to lubricate the surface of these films for processing ease, can be prevalent within the resin and migrate to the surface of the film within a few days after extrusion. Although there is potential for the additive to mask-over treatment, it is far more important to surface treat immediately after extrusion, since it will be practically impossible to do so after additive migration to improve surface properties sufficiently for ink, coating, or lamination adhesion. 

If more traditional spectra are required, the usual approach is to press a thin film of the samples using a temperature which is above the Tg or T j and to record a transmission spectrum. A transmission infrared spectrum of polypropylene produced from a film pressed at 170 °C is shown in Figure 7. Another technique that can be used to obtain transmission spectra is to dissolve the sample up using a suitable solvent and to cast a film. Care has to be taken to remove all of the solvent by drying in an oven otherwise it can influence the data obtained. A transmission infrared spectrum of PVC produced from a film cast from a solution in THF is shown in Figure 8. 

C.4 Film Casting of LDPE. It is desired to use the same film casting equipment as is used for polypropylene (see Design Problem IV). Using the same conditions as given in Design Problem IV, except the initial temperature for LDPE is 175 °C, determine whether can be maintained below 3.0%. 

EVALUATION OF ORIENTED POLYPROPYLENE/CAST POLYPROPYLENE FILM AT THE HEAT-SEALING PART AND THE EDGE... 

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