Whether branched or unbranched polyolefins run better depends on the processing method, equipment, and desired product properties. Here’s a breakdown of how each type behaves in different processing conditions:
Comparison of Branched vs. Unbranched Polyolefins in Processing
| Property | Branched Polyolefins (LDPE, LLDPE) | Unbranched Polyolefins (HDPE, PP) |
| Melt Flow (Viscosity in Processing) | Higher viscosity, requires higher shear for flow | Lower viscosity, flows more easily |
| Extrusion (e.g. Films, Pipes, Sheets) | Runs better in blown film extrusion (LDPE films) | Runs better in profile extrusion (HDPE) |
| Injection Moulding | Can be harder to mould due to elasticity | Flows well into moulds, better for rigid parts |
| Stretchability | More flexible, better for stretch films | Stiffer, harder to stretch |
| Cooling & Crystallization | Slower cooling due to lower crystallinity | Faster cooling, better for high – speed modelling |
| Die Swell (Expansion after Extrusion) | More swelling (caused by long – chain branching) | Less swelling, better for precision parts |
Which Runs Better?
- For film extrusion: Branched polyolefins (LDPE, LLDPE) perform better due to their flexibility and melt strength.
- For rigid part moulding (e.g., pipes, containers, structural parts): Unbranched polyolefins (HDPE, PP) perform better due to better flow and dimensional stability.
- For high-speed injection moulding: HDPE and PP flow better into moulds, making them more efficient for mass production.
- For applications needing stretchability and toughness: LLDPE runs better than LDPE due to its controlled short-chain branching.