Often when people talk about plastic films互换式旅游,后入式动态图—which technically are defined as plastic sold in thicknesses of up to 10 mils—they treat them as one type of material, grouping all flexible plastic packaging into a single category. What they do not realize is that plastic films compose a broad category of materials that can be relatively simple or complex depending on the demands of a particular product or package. They can be sourced from petroleum or from plants including wood. They can be biodegradable or home compostable or be reused for energy.
Like plastic bottles and containers, film can be made with different resins, each of which has a unique combination of properties that makes it ideal for certain applications. For example, low density polyethylene (LDPE) film acts as a gas barrier, which is necessary for packaging such things as chicken, which would quickly spoil if exposed to oxygen. Polyvinyl chloride (PVC) film, on the other hand, is gas permeable and necessary for packaging such things as red meat, which require a small amount of oxygen inside the package in order to keep it fresh.
Plastic film also can be clear or colored, printed or plain, single- or multilayered and combined with other materials such as aluminum and paper. It can come in a variety of thicknesses and degrees of opacity. Thus, the only thing that all plastic film really has in common is that it is flexible in nature, as used in grocery bags, as opposed to rigid, as used in soft drink bottles and butter tubs.