How to achieve high ductility?

Ductility plays a vital role in several aspects:

• Processing: Many polymers undergo shaping processes like blow molding or thermoforming. Ductility allows them to be stretched, molded, and formed into various shapes without cracking or tearing.
• Durability: Ductile polymers can absorb impact energy by deforming instead of breaking. This makes them more resistant to accidental drops, bumps, and scratches, extending their lifespan.
• Design flexibility: Ductility allows for the creation of intricate shapes and designs that wouldn't be possible with brittle materials. This opens doors for innovative product design in various industries.
• Safety: In applications like electrical wire insulation or tubing for fluids, ductility is essential. It ensures the material can withstand stress and strain without catastrophic failure, potentially preventing accidents.

Ductile-to-brittle transition temperature refers to the temperature at which a material's behavior shifts from ductile (flexible and able to deform) to brittle (rigid and prone to fracture). The puncture test method is the simplest way of measuring the ductile to brittle transition temperature¹.

Standards ISO 6603-2 (Puncture Impact Behavior of Plastics) and ASTM D3763 (High-Speed Puncture Properties of Plastics) provide guidance on how to perform a puncture test on plastics.

• At temperatures above the DBTT, the material exhibits ductility. It can bend, deform, and absorb some impact energy without breaking. This is desirable for many applications.
• Brittle Behavior: At temperatures below the DBTT, the material becomes brittle. It loses its flexibility and is more susceptible to cracking or shattering under stress or impact. This can be a safety concern.

Want to find out more about DBTT values of polymers? Find them here >>

Image credits: Illinois Tool Works¹

1. Molecular structure: Polymers with long, flexible chains tend to be more ductile. These chains can easily slide past each other under stress, allowing for deformation without breaking.
2. Crystallinity: Highly crystalline polymers, where chains are tightly packed, are generally less ductile. Crystalline regions act as rigid domains that hinder chain movement and make the material brittle.
3. Cross-linking: The presence of cross-links between polymer chains restricts their movement, reducing ductility. Cross-linking can be beneficial for other properties like strength but comes at the cost of flexibility.
4. Temperature: Generally, polymers become more ductile at higher temperatures. Increased thermal energy allows for easier chain movement and deformation.