Introduction about film

Introduction

    Plastics are the most versatile materials ever invented, and have become a universal material, used for everything from water bottles to wings on combat aircraft. Plastic materials display properties that are unique when compared to other materials and have contributed greatly to quality of our everyday life. At this moment, you are almost certain to be touching plastic. Yet, while plastics play such an important role, we do not always understand the fundamental concepts of their production, compounding, end properties, and use. 

    If words such as polymer, thermoplastic, creep, amorphous, and modulus are outside your normal vocabulary, this presentation is for you. 

    The usefulness of plastics is attributed to the fact that they provide a wide range of properties and can be changed into and products by relatively simple and inexpensive fabrication means. In order to take full advantage of these materials, it is important to have a clear understanding of their composition and elementary properties.

Techniques in plastic industry

    There are at least 12 major processing techniques used to form plastic goods, but three of the most important are extrusion, blow molding, and injection molding. Others include calendering, film casting, rotational molding, laminating, and casting.

    Extrusion entails melting and compressing plastic granules in a tube. A screw conveyor inside the tube then forces the plastic through a nozzle at the end of the tube. The physical characteristics of the plastics can be altered by applying heat or cold to the barrel, adjusting the screw pressure, or using different types and sizes of screws. Extrusion is used to make pipe, sheeting, film, and other various forms.

Applications: Film, Sheet, Yarn, Pipe, Wrap electrical cables, empty products, Products with a width of up to 10m.

Blow molding takes the extrusion process one step further. In blow-molding, the extruded plastic is forced into a bottle-shaped mold, to which compressed air is applied to inflate the plastic and press it against the cold surface of the mold.

Applications: The majority of bottles, barrels and containers are manufactured by blow molding.

In a similar process, injection molding entails extruding plastic directly into a two-piece mold, where it hardens into a solid form. When the shape has cooled enough to hold its form, the mold can be opened and the shape removed. Depending on the product's specifications, the molds may be made of simple, low-cost soft alloys like aluminum or more expensive and durable materials for high-precision molding.

Applications: used to create many things such as wire spools, packagingbottle caps, automotive parts and components, toys, pocket combs, some musical instruments (and parts of them), one-piece chairs and small tables, storage containers, mechanical parts (including gears), and most other plastic products available today

 

    Another reason why it is somewhat difficult to get a grasp on plastic film is because it is used in such a wide range of products and packages. Typically, its usage is divided into two general categories—packaging and non-packaging—that can also be broken down into smaller components. For example, there are three types of packaging applications in which film is used: food, nonfood and other. It is important to keep in mind that within each of these categories, plastic film can vary by resin and color; it also may be made of one layer of plastic or as many as ten layers depending on the complexity of the package. In addition, other materials—such as aluminum or paper—may be used in combination with plastic film in order to impart special properties. Therefore, even the following categories of film are themselves made up of many diverse types of film.

Food Packaging

    Food packaging film is used in such things as in-store bags for produce (such as apples and potatoes); all non-frozen baked goods (such as rolls and breads); bakery bread and bun bags; tray covers for institutional deliveries of bakery products; bags-in-a-box (film used to contain fluid in a supportive box, such as boxed wine); boil-in-bags (film used to contain food prepared by keeping it in the package and placing it in boiling water); candy and confection bags and wrappers; carton liners (for such products as cake mixes); and meat, poultry and seafood wraps (such as hot dog and bacon film). As mentioned in the section on film generation, the only data available on the use of film in food packaging applications are restricted to the polyethylene family, despite the fact that other resins are used in food packaging as well.

Nonfood Packaging

    Nonfood packaging film refers to such things as industrial liners (film used to line supported structures such as gaylord boxes, frozen pork box liners and liners for shipments of nuts and bolts), shipping sacks (film used to protect and/or contain contents such as bark and mulch bags), bubble packing, envelopes, multiwall sack liners, overwrap, and rack and counter bags. Again, data on film used in nonfood packaging applications are confined to the polyethylene family.

Other Packaging

    The other types of packaging in which film is found are stretch and shrink wrap. Stretch wrap is a strong, highly flexible film that can be stretched to take the shape of a product or products. It is used in a variety of applications ranging from overwrapping fresh meats to securing shipping cartons to pallets. Stretch wrap usually is made of co-extruded LLDPE and LDPE, although it can be made from individual plastic resins, such as LLDPE, LDPE and PVC.

Characteristics of Film

Stretch Film

    Stretch wrapping is stretchable plastic film that is wrapped around a load of products allowing it to be stretched; this elasticity holds the load tightly together.           

    This type of wrapping is usually employed to hold loads and products together on a pallet for transportation or storage purposes. Stretch wrap can come in a variety of specialty films. Some examples are: UV stretch wrap, vented pallet wrap, anti-static stretch film, colored stretch film, pre-stretched stretch film, etc.       

    Advantages:

Protective- This wrapping is secure and protects products from dust and moisture.  It can also protect from sun with UV film options

Cost Effective- Stretch wrap is less expensive than other types of pallet wrapping. Additionally, the equipment needed for stretch wrapping is cheaper than other forms of wrapping.

Adaptable- Stretch wrap has a variety of films to suit each application; and it is even appropriate for different types of surfaces.

Shrink Film

    Shrink Wrapping is covered loosely around a product or load & it shrinks tightly when heat is applied. Most commonly made from polyolefin plastics.

    This type of wrapping is usually employed to protect a single product from dust or weather; or to tightly combine smaller items together. It can also wrap products together on a pallet; but is less common. This wrapping is widely used for covering foods; for example, cheese, meats and vegetables.

    Advantages:

Protective – Shrink wrap is great for protecting products from weather or moisture damage along with dust and dirt.

No surface damage – If shrink wrapping has been properly applied you should have no issues with chafing or damage during transportation or whilst being stored.

Breathability- Shrink wrap has the option of being ventilated; therefore, reducing any damage that can occur from moisture.

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