Sustainability has become and important issue in the world as the Green Movement continues to gain popularity. One area where research is being conducted to find a more sustainable production process is plastic films. Plastic films are defined as a packaging material, usually less than ten mils (a mil is 0.001 inch) in thickness, with an average of 0.7–1.5 mils, that can be used as a bag or wrapper. They are composed of a broad range of materials, which can be simple or complex depending on what a particular product or package demands (Osborn & Jenkins, 1992). There are two main categories of films used in packaging, conventional films and sustainable films.
Conventional plastic films are much more widely used and have a larger market than sustainable films. The film can be made with different resins, each of which have unique structures and are ideal for specific applications. The films can be clear or colored, printed or plain, single- or multilayered and are often combined with other materials such as aluminum and paper. Examples of plastic films usages include Ziploc bags, trash bags, grocery sacks, drycleaner bags, and plastic wrap.
The only common characteristic of all plastic conventional film is that it is flexible in nature. The most common resin used to create these plastic film packages is low-density polyethylene (LDPE). As a film LDPE has decent clarity, is a good moisture and gas barrier, and it can be heat sealed while retaining its strength and flexibility. Polypropylene (PP) is also a common resin used to create plastic film. It has an excellent moisture barrier, good transparency, gloss, and tensile strength. The PP resin also has a high melting point, which makes it appropriate for packages that need to be sterilized at higher temperatures. Since PP has only average gas barrier properties, it often combined with coatings such as PVDC (polyvinylidene chloride), which provides added barrier properties. There are many other resins used for film including polyethylene terephthalate (PET), polyvinyl chloride (PVC), and polyamide or nylon (PA). Each of these resins has specific characteristics, which make it unique, and give it a certain for plastic film packaging.
The manufacturing process for conventional plastic films is complex and involves the use of fossil fuels and oil, making it unsustainable. Most plastic films produced are blown films. The process begins with the resin in a pellet form; it is then condensed and melted to form a thick liquid. This melted plastic is then extruded, through a ring shaped die. Air is introduced through a hole in the center of the die, and the pressure causes the extruded melt to inflate into a bubble with uniform thickness. The bubble of film is pulled constantly upwards from the die and a cooling mechanism blows air onto the film. After the film becomes solid it moves into a set of nip rollers. These rollers collapse the bubble and flatten it into two film layers. The film is then pulled...