These properties include good water resistance, heat resistance up to 300°F and exceptional tensile strength, as well as good chemical resistance. Moisture resistance: the ability of a material to resist absorbing moisture from the air or when submerged in water. Teresa Calafut, in Plastic Films in Food Packaging, 1998.Metallized film is developed by vaporizing molten metal, depositing it on a polymer band and then applying it to the film. Aluminum is the most used because of its cost-effectiveness.
The entire process is carried out in a vacuum chamber; the amount of metal applied is carefully controlled by instruments, and the vacuum temperature of the metal and the feed rate of the belt must also be closely monitored. Metallization improves the moisture and gas barrier properties of the film and prevents light from reaching the product. Heat sealing is difficult in BOPP films, but can be facilitated by coating the film after processing with a heat-sealable material (such as polyvinylidene chloride) or by co-extrusion with one or more copolymers before processing to produce film layers. Film structures combined with additives can be designed to be self-supporting and flexible, allowing them to be bent or folded without inducing structural weakness in the film.
One of the most important commercial polyolefin films is biaxially oriented polypropylene (BOPP) film. Lamination is preferred when a specific film composition cannot be effectively executed in co-extrusion systems due to equipment limitations, and also when the high temperatures required in co-extrusion would be detrimental to the films. This technology makes it possible to adjust stretch proportions, stretch curves, relaxation curves and process temperatures in the most flexible way in order to meet the film properties required in newly developed films (Fig. This type of composite film offers excellent stability and often incorporates the best properties of each individual film layer.
Second surface printing: inks are applied to the unexposed side of the film so that the film protects the inks from scratches or damage. Thermoforming: a forming method (normally used in medical packaging) in which a plastic film is deformed while being subjected to heat close to the softening temperature of the film. In the corona treatment part of this study, both the BOPLA film that had been treated with corona during manufacture and the BOPLA film that had not received any previous treatment were evaluated to determine the discharge energy compared to the surface energy obtained and the period of time (in days) that the film retained surface energy. In addition, samples of the BOPLA films were stored and tested over time to determine how long the film retains its high level of surface energy.
New advances in films for medical packaging were due to a better understanding and subsequent modification of molecular structures to improve desirable properties; to new techniques for manufacturing flexible films; and to the use of plasticizers, thermal stabilizers, lubricants and additives recently discovered for properties such as resistance to radiation. Over the past two decades, the healthcare industry has replaced many of the traditional components of metal and glass packaging with high-barrier plastic films comprised of individual polymers, new lamination combinations, metallized films and a variety of specialized coatings. The case (E) is designed as a complementary formulation in the conversion stage if insufficient stability of the organic substrate is found at the level of the film manufacturer. Other expected developments include water-soluble films with a controlled solubility rate, new films that can be sterilized with gamma rays or with an electron beam without degrading, small-caliber films that retain their initial tensile strength, films that do not degrade with ultraviolet light, films that tolerate high processing temperatures, films that are biodegradable or photodegradable, and silica-coated films that confer barrier properties and clarity.
Biaxially oriented PP films are widespread, not only in transparent applications, but also in the types of opaque white films that are mainly applied for packaging and labeling. .