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The Various Manufacturing Processes of Polyethylene

May 08, 2020

 Polyethylene foam is useful in applications across a diverse number of industries. Most commonly used in packaging applications, there is no doubting the utility of this material. But where exactly do polyethylene-based foams come from? 

As its name probably suggests, polyethylene foam comes from polyethylene plastic. Polyethylene is what is referred to as a thermoplastic, a plastic material that becomes pliable in warmer temperatures and stiffens in cooler temperatures. There are two overarching categories in which polyethylene plastics fall into: low density and high density. 


In today’s blog we’ll briefly outline what occurs in the manufacturing processes of both low density and high density polyethylene plastics. 


Low Density Polyethylene (LDPE)


LDPE is the most common type of polyethylene used. LDPE properties enable them to be highly flexible for use across a larger range of applications in comparison to HDPE. LDPE resins offer increased durability and strength, printability, and elasticity - making LDPE optimal for use in packaging manufacturing applications.


There exist two common processes that are used to manufacture LDPE: the tubular and autoclave processes. The tubular manufacture process involves the polymerization of polyethylene in a tubular reactor. The interior of the reactor where the polymerization occurs must sustain extremely high temperatures for the chemical change to happen effectively. 


The autoclave process involves a series of stirred reactors for polymerization to take place. Once the material leaves the reactor, it passes through low and medium pressure separators that remove the ethylene from the initial LDPE polymer. Once this occurs, the polymers undergo a pelletization process for further processing. 


High Density Polyethylene


HDPE is manufactured using a process called “cracking”. Cracking involves the application of intense heat to petroleum under controlled conditions to create ethylene gas. Through the production process, the ethylene gas molecules will begin to attach and form polymers that can then be used to produce polyethylene. 


Polyethylene Foam


Polyethylene-based foams are manufactured by heating polymer compounds with varying additives that can affect its final properties once the material is heated and extruded into its solid foam state. Depending on the application the foam is manufactured for, the formula will vary to achieve different property outcomes.