Resins… Film thickness… Tensile strength… Impact resistance… What do all of these terms mean to you when purchasing your polyethylene bags?
Unless you are a poly salesman or have a degree in Plastics Engineering, the terminology used in the industry probably makes your head spin. To assist you, we’ve created Polyethylene Packaging 101.
Resins (Defined as: Any of numerous physically similar polymerized synthetics or chemically modified natural resins including thermoplastic materials such as polyvinyl, polystyrene, and polyethylene and thermosetting materials such as polyesters, epoxies, and silicones that are used with fillers, stabilizers, pigments, and other components to form plastics.)
You may find it overwhelming with all the different resins available these days. How does one choose when you have octene, metalocene, butene, hexene, etc… A knowledgeable sales representative will be able to help determine what grade to use. Each grade has different characteristics and choices should be based on applications. Understanding resin properties is critical in formulating the right product for your specific application.
Film Thickness (Gauge)
Polyethylene film thickness is measured by thousandths of an inch, or milli-inch. The thickness of the bag does not always correlate into strength. A heavy gauge bag is not always strong. Most often it is a combination of resin grade and gauge relative to the application. A 2 mil octene linear bag will have more strength than a 2 mil butene linear.
Tensile Strength vs. Impact Resistance
- Tensile strength is the maximum stress that a material can withstand while being stretched or pulled before breaking. Why is this important?
It’s important to have a plastic bag that is strong enough for your application. A plastic bag that holds 50 pounds of material must have adequate tensile strength, otherwise the bag will end up breaking.
- Impact resistance is a material’s ability to resist shock loading. What does this mean?
Basically it is the film’s ability to resist being punctured. A punctured bag may result in contaminated goods or product loss.
When choosing the correct gauge and resin formula it is important to consider how tensile strength and impact resistance are relevant to your packaging application. An example that everyone can relate to is a garbage bag. I’m sure most have had failure in a garbage bag whether it breaks when lifting out of the can (tensile strength) or waste material punctures holes in it (impact resistance). With all these variables in choosing the correct formula for your polyethylene package, having a knowledgeable salesman is vital.
Who knew there was so much to know about making Polyethylene “Film and Bags”!?!