Differences Between Rigid & Nonrigid Containers

Flexible Plastics

• Flexible plastics usually consist of polyethylene, polypropylene, vinyl, polystyrene, polysulfone and polycarbonate. These materials are in the family of thermoplastic polymers and are resistant to heat as well as being relatively sturdy and effective for use in containers. Flexible plastics are usually formed with a barrier and have at least three layers of film type polymers, usually with different qualities. For example, in a flexible container intended to hold water, the plastics would be layered with a waterproof barrier, an insulating barrier, shock absorbing layer and finally a tough outer layer that has been subjected to antioxidants and impact modifiers. Antioxidants allow the flexible plastic to be slightly more resistant to breaking down under sunlight and UV lighting as well as an increased resistance towards heat and oxidation.

Rigid Plastics

• Rigid plastics normally consist of polyethylene terephthalate, polyethylene, vinyl, polyvinyl chloride (PVC), polypropylene and polystyrene. These plastics are usually subjected to being layered with a gas barrier or are molded into shape while liquidized under heat, or blown. This allows the rigid plastic to be used for a variety of different applications due to the difference in its construction. Additives such as simple fillers or chlorides can be used to add properties such as thickness or density to the plastic; however, these usually limit the recyclability of the plastic. Due to the thick nature of rigid plastics, they are more durable under UV lighting as well as sunlight and oxidation.

Gas Barrier

• The use of a gas barrier in plastics can add two properties to the plastics. The most redundant being that the plastic can then be used to store simple gasses for transport or storage, such as in a laboratory or school. The other being that the application of a gas barrier causes thicker plastics to appear crystallized or clear; flexible plastics appear to be clearer but can become more rigid as well.

Plasticization

• Plasticization is the process by which polymers are softened so that they their plasticity level is higher or they are more flexible. This process can range from including or removing plasticizing elements known as plasticizers or simple melting or soaking in water until the plastics are flexible enough to be formed into the proper shape.