Chemically neutral and easy to manufacture, engineering plastics are suitable for all manner of applications. Packaging immediately comes to mind because this inert nature is highly desirable, especially when containment of a reactive substance is an issue. Versatility in form and function is the second factor that propels plastic to the top, presenting molded efficiency alongside design flexibility. Paper and board can be shaped but the material lacks the capacity to soften. Wood is inherently strong but useless for cushioning purposes. Only plastics cushion and mold to any shape with tailored ease as dictated by engineering specs. Chemical processes and heat-treated machining affects the shape and consistency of the substance. One example is the extrusion of polyethylene terephthalate (PET) into shapes that offer impact resistance and superior chemical resistance. Of course, the chemical resistance part of this statement can be matched by glass, a popular storage medium, but glass breaks.
Other forms of rigid plastics include high-density polyethylene and polvinyl chloride (PVC). Each one has its own set of characteristics regarding strength and ability to absorb impact. Again, glass comes out on top in several categories, in holding contamination-free medications in care facilities and medical research laboratories, but rigid plastic is still the dominant substance due to a resistance to breakage. Also, looking at unavoidable practical concerns as we must, glass is heavy and comes from a more expensive manufacturing process. That’s a double-blow when considering the logistics of transportation. The rigid plastic will arrive safe-and-sound, adding little weight to the overall package, but a corresponding package consisting of glass will require extra care due to its fragile nature, and there’s that annoying extra weight to deal with during shipping.
The rigid category has to come down firmly on the side of rigid plastic. The only flexibility offered by paper is the addition of lamination and corrugation, a big step backward from the versatility of plastic foam or intricately molded storage compartments. Plastic may lose out slightly at the high-end of the medical field due to a slight reactance or absorption property, but class one glass, also known as borosilicate is an expensive material, one used exclusively in pharmaceutical applications.
Soft engineering plastics are every bit as versatile as their hard-set brethren, but one extra property, elasticity, bespeaks a greater need for pliability and malleability. Plastic bags and blister packs are made from this class of plastic. Polystyrene molded packing holds fragile components stably while absorbing remarkable impact. For an example of elasticity, look to everyday food storage. Sheets of low-density polyethylene conform to every contour of a slice of meat, helping to preserve flavour and hygiene. The same benefit is seen in the home, with leftovers sealed in soft containers and wrapped in plastic film to gift the food with added freshness for several days. The electronics industry adds special anti-static linings to the form, protecting sensitive electronic components from damage. The applications are literally endless, all due to the versatility of polymer engineering and the evolution of packaging.