Just before the 20th century began, polyethylene (PE) was discovered, and it quickly rose to the top of the industry. The manufacturing sector still relies heavily on polyethylene because of its low cost, machinability, and compatibility with other materials. PE is regularly utilized in consumer goods, medical technology, lab equipment and commercial products including tanks and pipelines.
Branching versions, linear versions, and cross-linked polyethylenes are the three basic chemical structures that divide the many types of polyethylene. The two most popular types of PE are high- and low-density polyethylene (HDPE and LDPE).
High-density polyethylene (HDPE)
A polyethylene with a linear structure is called HDPE. HDPE is a very strong polyethylene with excellent tensile strength, stiffness, and impact resistance because of how closely its molecules are packed together. In addition to being UV-resistant, HDPE is also chemically resistant. In addition to being strong, HDPE is also a very versatile material that is simple to work with.
HDPE is frequently used in outdoor furniture and equipment, including constructions like playgrounds, due to its malleability and dimensional stability. In addition to being utilized in consumer products like food and beverage bottles, cutting boards, and even toys, HDPE is also employed in industrial applications like pipe flanges and chemical tanks. HDPE's capacity to be reused and recycled is a huge advantage.
DISADVANTAGES: The vulnerability to stress cracking under high pressure and low to moderate heat resistance are some drawbacks of HDPE. HDPE is also susceptible to shrinkage when molded; as a result, CNC machining and additive manufacturing are the ideal uses for HDPE. Due to the fine tolerances that this manufacturing process can produce, processing HDPE with CNC machining is particularly well-liked.
Low-density polyethylene (LDPE)
As LDPE is a branching of polyethylene, its molecules are less tightly packed. LDPE is consequently less dense than other linear polyethylenes, such as HDPE. Yet that doesn't imply that LDPE isn't robust.
In addition to its impact resistance, LDPE also boasts stain resistance, electrical insulation, and waterproofness. LDPE naturally reflects light and is translucent.
Grocery bags, plastic film or wrap, flexible packaging material, and food and beverage containers are examples of typical LDPE consumer components. Moreover, the production of orthotics and prosthetics uses LDPE.
DISADVANTAGES: Compared to HDPE, LDPE is more susceptible to stress cracking, less heat resistant, and extremely permeable to gases like carbon dioxide. Due to its extreme flammability, LDPE's employment in high-temperature applications is severely constrained.
Differences between HDPE and LDPE
- Both materials are made of polymer chains, but the polymer chains in LDPE are more branched and the polymer chains in HDPE are more crystalline
- Compared to HDPE, LDPE is softer and more flexible. It is more translucent and has a lower melting point (115° C). It is more likely to crack under pressure when compared to HDPE. HDPE is more chemically resistant, stiff, and long-lasting. It can resist higher temperatures than LDPE since it has a higher melting point (135° C). Greater strength and opacity are further benefits of the material's more crystalline structure
- Due to its softness and propensity to tangle with recycling equipment, LDPE can also be trickier to recycle. HDPE can be processed using recycling machinery more easily and is more portable.
- In order to promote polymerization, ethylene monomer is compressed in an autoclave or tubular reactor to create LDPE whereas By heating petroleum at extremely high temperatures, HDPE is produced. The ethylene gas monomers are released as a result of this process, and they unite to create polymer chains.
Even though LDPE and HDPE have many beneficial traits in common, such as excellent chemical resistance and low solubility, they also have unique material features that affect their suitability for certain applications. HDPE is a far more dependable solution than LDPE for molding and shaping items that are stronger and more long-lasting.
