Compound - specifically produced material mixture
What is a compound?
In plastics and rubber processing, a compound is a specifically produced material mixture in which a base polymer or polymer blend is combined with various additives to achieve defined properties. The polymer provides the basic properties in terms of mechanical, thermal and chemical behaviour - while the type and quantity of additives tailor these properties specifically to the respective application.
Depending on the requirements Molded Rubber, Molded Silicone and TPE Molded for elastic applications or Metal-, Plastic- and Fabric-Composite parts, if additional mechanical, chemical or structural requirements have to be met.
What are the components of a compound?
A compound typically consists of:
- Base polymer - e.g. natural rubber (NR), EPDM, NBR, HNBR, FKM
- Fillers such as carbon black, silica or chalk for reinforcement, cost optimisation or property modification
- Plasticiser to improve flexibility and workability
- Crosslinking chemicals such as sulphur, peroxides or metal oxides to increase mechanical stability
- Adhesion promoter for binding to substrates
- Anti-ageing agent against oxygen, ozone, UV radiation and thermal influences
- Colourants for visual design
- If necessary, special additives, e.g. flame retardants or lubricants
The composition of a compound is specified in phr (parts per hundred rubber), i.e. in relation to the mass of the base polymer used (100 phr). Fillers are typically 30-70 phr (in extreme cases up to 100 phr), while additives such as Crosslinker, Plasticiser, Anti-ageing agent etc. usually remain below 30phr.
What are the areas of application of a compound?
A compound can be specially formulated to meet the requirements of an application so that the properties of the base polymer are significantly exceeded. For example, special compounds can be explicitly optimised for use under high thermal, chemical or mechanical stress. In the Rubberindustry, compounds are usually produced in mixing mills or internal mixers, followed by homogenisation. Compounds can be found in almost all industrial sectors: in vehicle construction (tyres, hoses), in the construction industry (Profiles, Sealings), in medical technology (sterile Silicone parts) or in conveyor technology (abrasion-resistant conveyor belts). Specialised compounds also enable the production of Rubber-metal composite parts or Rubber-plastic composite parts with optimum adhesion between the materials.
