HDPE vs LDPE Plastic Bags

Polyethene is one of the most common thermoplastics used to manufacture innumerable daily items, including plastic bags, soft drink bottles and reusable water bottles. Two of the most common types of polyethene are HDPE Plastic and LDPE Plastic.

There are seven general types of plastic, each comprising a unique combination of resins. A mark of triangular arrows with a number in the middle can identify each plastic.

HDPE, or High-Density Polyethylene, is the number 2 plastic, while LDPE, or Low-Density Polyethylene, is the number 4 plastic. HDPE Plastic and LDPE Plastic share many properties but also possess unique characteristics that set them apart.

High-Density  Polyethylene  (HDPE Plastic)

HDPE plastic is an affordable thermoplastic polymer with a linear structure and little branching. It is manufactured at low temperatures ranging from 70°C to 300°C and pressures ranging from 10 to 80 bar.

HDPE is generally created by utilising two different techniques:

• Slurry Polymerisation – Polymerisation of monomers in the structure of dispersed monomer particles
• Gas-Phase Polymerisation – Polymerisation of monomers in the structure of a vaporised monomer, fluidised catalyst and polymer particles in a fluidised bed reactor

HDPE plastic bags are strong and resistant to tearing. They are the preferred choice for packaging solutions in garbage disposal, laundry and grocery containers where material strength is essential.

Some key features of HDPE plastic bags are:

• Low-cost, lightweight and durable
• Resistant against alcohols, diluted acids, alkalis, grease & liquids such as water
• Highly flexible; malleable enough to be easily moulded into various shapes and sizes
• Industrial-grade, FDA, NSF and USDA-approved
• Recyclable

HDPE plastic is also widely used to produce products such as plastic wrap and film, flexible packaging material, grocery bags and injection moulded parts.

Low-Density Polyethylene (LDPE Plastic)

LDPE plastic is a soft and flexible polymer. The packaging has a lower density, strength and temperature resistance than HDPE plastic. LDPE plastic is produced at high pressure of 1,000 to 3,000 bar and a low temperature of 80°C to 300°C.

This manufacturing process is known as free radical polymerisation. This process involves chain-growth polymerisation, where the polymer takes shape due to the continuous addition of unsaturated monomer molecules to an active, free radical centre.

The molecular structure of LDPE plastic features a higher degree of short and long-side-chain branching than HDPE plastic.

LDPE plastic is a material with excellent processability. It has high impact strength at low temperatures, good chemical and weather resistance, and is an excellent electrical insulator. Other desirable properties include low water absorption and transparency in thin foil film. LDPE plastic bags may be used in food packaging as it meets FDA regulations. [1]

Some key features of LDPE plastic are:

• Low-cost, lightweight and weatherproof
• Flexible; malleable enough to be easily moulded into various shapes & sizes
• Resistant against chemicals such as alcohols, dilute acids and alkalis
• Resistant to moisture, dust, dirt, oil and grease
• Excellent electrical insulation
• FDA-approved
• Recyclable

LDPE plastic is used in many everyday products, including food plastic bags, shrink wrap, and stretch film. LDPE material is also used in containers, dispensing and squeeze bottles, tubing, plastic parts of computer components, moulded laboratory equipment, and many caps and closures.

Plastic is also used for food packaging together with desiccants, oxygen absorbers, and ethylene absorbers. These packaging solutions can extend the shelf life of food products while preserving their freshness and quality.

HDPE vs LDPE – Pros and Cons

Conclusion

HDPE and LDPE Plastic Bags share several characteristics, including high chemical resistance, affordability and poor UV resistance. With biodegradable packaging solutions that break down naturally, find out more about saving the environment using biodegradable plastic bags.

Watch the video below to learn more about HPDE vs LDPE bags.