Traditional plastic bags are normally manufactured with polyethelene (PE). There are different types of PE. HDPE, LDPE and LLDPE are used to make plastic shopping grocery bags and trash bags, etc.
In practice the very thin bags are normally made with HDPE and thick or shiny bags are made with LDPE. LLDPE is usually mixed with other material.
Difference between Plastic Bag Material: HDPE, LDPE, LLDPE Resins
1.Plastic Bag Material of LDPE
LDPE (Low Density Polyethylene) has the most excessive branching. This causes the low density to have a less compact molecular structure which is what makes it less dense. It has a density of 0.910-0.925 g/cm3. The LDPE bags are more flexible but with less tensile strength.
2.Plastic Bag Material of HDPE
HDPE (High Density Polyethylene) has minimal branching of its’ polymer chains. Because it is denser it is more rigid and less permeable then the LDPE. It has a density of 0.941-0.965 g/cm3. The HDPE bags has better tensile strength but is not as flexible as LDPE bags.
3.Plastic Bag Material of LLDPE
LLDPE (Linear Low Density Polyethylene) has a significant number of short branches. Because it has shorter and more branches its chains are able slide against each other upon elongation without becoming entangled like LDPE which has long branching chains that would get caught on each other. This gives LLDPE higher tensile strength and higher impact and puncture resistance than the LDPE. It has a density of 0.91-0.94 g/cm3. It is somewhere between HDPE and LDPE.