Ageing
resistance

As defined by DIN 50035, ageing refers to all the chemical and physical processes that irreversibly occur to a material over time. Polymeric materials can age for a variety of reasons, such as heat, UV radiation and media, and ageing is highly dependent on operating and environmental conditions, e.g. the service temperature.

Representative products

WEVOPUR 1222

  • UV-resistant
  • Operating temperature range: -40 °C to +100 °C
  • Transparent/clear
  • Scratch-resistant in the upper Shore D range


WEVOPUR 7210 FL

  • Hydrolysis-resistant, 85/85 damp heat test
  • High heat-distortion resistance
  • Good flow properties, low mix viscosity
  • Low water absorption


WEVOPOX 6501 / WEVODUR HC 3001

  • High dielectric strength
  • Low shrinkage
  • Outdoor applications or weathering; UV-stable
  • Hot curing
The ageing of polymeric materials largely depends on the operating and ambient conditions.

Types of ageing

Chemical ageing (Post-polymerisation)

Degradation by molecular cleavage caused by:

  • High temperatures (thermal)
  • Radiation, e.g. UV
  • Oxygen and ozone (oxidation)
  • Agglomeration, e.g. exudation (plasticisers)
  • Water (hydrolysis)
  •  Microorganisms (microbial)

 

Physical ageing

  • Relaxation, stress relief
  • Post-crystallization
  • Separation (phase separation)
  • Plasticiser diffusion

 

Symptoms of ageing

  • Deformation of the object, cracking:
    • Stress cracking, e.g. migration of small molecules, corrosion
    • Cracks caused by oxygen or ozone, surface
    • Fatigue cracks due to structural changes
    • Fractures caused by embrittlement
  • Discolouration from oxidation or UV
  • Measurable changes – mechanical, optical or electrical
  • Changes in chemical behaviour, e.g. chemical resistance and diffusion behaviour
  • Deposition, e.g. exudation of the plasticiser

 

Suitable accelerated tests must be carried out to accurately predict the expected service life.

Determination of the temperature index TI according to IEC 60216:

  • Changes in material properties, such as tensile strength at different temperatures, until 50 % of the initial value is reached
  • Time and temperature transferred to a long-term Arrhenius diagram and extrapolated to 20,000 hours
Information
Contact

WEVO-CHEMIE GmbH
Schönbergstrasse 14
73760 Ostfildern-Kemnat
Germany
Phone +49 711 167 61-0
Fax +49 711 167 61-44
info@wevo-chemie.de