Plasticisers – Facilitating processing

What are plasticisers?

External plasticisers are liquid or low-viscosity substances added to rubber and plastic compounds that position themselves between the polymer chains. In contrast, internal plasticisers are chemically bonded to the polymer structure, either as side groups or end groups. Plasticisers reduce intermolecular forces between polymer chains and lower the glass transition temperature of polymers, reducing hardness and making the material more supple. At the same time, they ensure lower viscosity, which facilitates processing – and therefore significantly influences the quality and dimensional stability of finished products. Molded Rubber and Molded Silicone influences. Especially with Plastic-rubber composite parts Does targeted plasticiser selection play a crucial role, as it directly influences interfacial adhesion and the mechanical interplay of the bonded materials.

Function of plasticisers

Internal plasticisers have a physical effect: they are deposited between the polymer chains and reduce their intermolecular forces. This leads to

Increased elasticity and bending capacity
Less brittle in the cold
Improved processing (e.g. for Extrusion or Moulding presses)
Adjustment of the Shore hardness in the desired area
Influencing density, Rebound behaviour and haptics
As external plasticisers are not chemically bound, they can be lost over time or washed out on contact with the media

The selection of the right plasticiser depends on the type of polymer, application temperature, media contact and regulatory requirements - especially in sensitive areas such as medical technology or food packaging.

Types of plasticisers

Mineral oil-based plasticisers: e.g. paraffin oil, aromatic oils
Phthalates: formerly standard, now partly restricted (e.g. DEHP, DOP)
Adipate, Sebacate, Citrate: for PVC and other thermoplastics
Vegetable oil-based / biocompatible plasticisers (e.g. for TPE or medical applications)
Special plasticiser for high temperature resistance or reduced migration

Plasticisers can also be specifically modified in order to LABS-freedom or to minimise migration.