Today's KNOWLEDGE Share :: What is the glass transition in plastics, really not from a datasheet point of view, but from the polymer molecule and up?

Today's KNOWLEDGE Share

What is the glass transition in plastics, really not from a datasheet point of view, but from the polymer molecule and up?


Plastics soften, become rubbery or flow when used above their glass transition temperature (Tg). Below Tg, those same materials become stiff, brittle and glassy. Parts crack in cold environments. Impact resistance disappears. What worked fine yesterday suddenly fails today.


The glass transition is the temperature range where molecular mobility becomes mechanically relevant. It is not a chemical change or a melting event.


- The polymer does not melt.

- No chemical bonds are broken.

- The chemistry does not change.

- There is no phase change.


Tg arises from cooperative segmental motion: small segments of polymer chains start to move together, enabled by sufficient thermal energy and free volume.


Below Tg, polymer chains are effectively locked in place, like a tangled ball of yarn. Stress is stored elastically, leading to brittle fracture.


Above Tg, segmental motion allows chains to reorganize, absorbing mechanical energy and enabling ductile deformation.


Understanding Tg through molecular motion explains why different polymers have varying Tg values—factors like backbone stiffness and intermolecular forces influence chain flexibility and free volume.


This molecular boundary marks the shift between glassy and rubbery behavior. For practical principles connecting structure to Tg in real materials, read the full article. https://lnkd.in/g-GBAkx4


source : Plastics Technology

Comments

Post a Comment

Popular posts from this blog

Today's KNOWLEDGE Share : What Is Going Wrong in UK Plastics Recycling?

Image
Today's KNOWLEDGE Share What Is Going Wrong in UK Plastics Recycling? Biffa shut its Sunderland plant. Viridor walked away from Avonmouth and Rochester. Yes Recycling Fife collapsed within a year. All three were backed by major investments All three had buyers lined up for recyclate All three are now offline This is not bad luck It is bad structure Over the next four posts I will break down: 1. Why cheap virgin imports are undercutting UK recyclers 2. How weak policy enforcement is fuelling market failure 3. What volatile PRNs and cheap exports are doing to infrastructure 4. Why demand from brands is softer than their promises Let’s start with the first: **Cheap Virgin Resin = Broken Economics** Virgin PE, PP, and PET have been flooding the global market. New capacity in Asia and the US has driven prices down 30 to 40 percent. Meanwhile, recycled plastic costs more to produce in the UK than it can sell for. We are asking UK recyclers to compete with materials made in places with – ...
Read more

Today's KNOWLEDGE Share : Robotic 3D printing can compete with traditional boatbuilding

Image
Today's KNOWLEDGE Share “Robotic 3D printing can compete with traditional boatbuilding”, Simone Barbera and Mattia De Santis, Caracol V2 catamaran was printed in Italy at Caracol’s production center and headquarter in Barlassina, near Milan, with a Heron AM 400, Caracol’s robotic Large Format Additive Manufacturing (LFAM) platform. The lattest was specifically configured with a 7-axis robotic arm mounted on a rail, enabling the printing of parts up to 10 meters in length. How did the collaboration between V2 Group and Caracol come about? Simone Barbera : The collaboration between V2 Group and Caracol originated from a shared vision to revolutionize boat manufacturing through sustainable innovation. V2 Group, a Spanish-company specialized in nautical design and engineering, is seeking to develop electric vessels manufactured sustainably. On the other hand, Caracol, leader in robotic advanced manufacturing technology, had had years of experience working with Large Format Additive Ma...
Read more

Borealis’ new compounding line in Belgium offers premium recyclate-based polyolefins

Image
 Borealis is proud to announce that its new compounding line for recyclate-based polyolefins (rPO) is now fully operational in Beringen, Belgium. This milestone marks a significant step forward in helping customers meet their circularity and sustainability targets—without sacrificing performance and reliability. Using Borealis’ proprietary Borcycle M mechanical recycling technology, the line combines post-consumer and virgin polyolefins into rigid polypropylene (PP) and polyethylene (PE) compounds that meet the high standards required for demanding applications in mobility, consumer products, appliances, and energy. The Beringen facility is not only designed to process a wide range of recyclate flakes, offering exceptional versatility to meet diverse customer needs, but it also serves as a platform for collaboration—enabling customers to co-develop and test new solutions that bring recycled plastics into high-value applications. “This installation is more than just a technological ...
Read more