Polymers

Question 1

What are the main causes if polymer failure?

Answer 1

1. Incorrect material selection
    The use of an incorrect material for an application is a common cause of polymer failure; lack of understanding of
    the interaction of polymers with chemicals and environments
   and
    long term response - commonly leads to premature failure, e.g.
   many brittle & ductile plastics
2. Chemical & environmental interactions
    For many polymers specific interactions with common
   household products can lead to rapid crazing, cracking,
   fracture and product failure,
    e.g. HDPE used for underground water pipes (environmental
   stress cracking (ESC))
3. Response to long term loads
    Plastic and rubber components are sensitive to long term loads.
   These can be either static or dynamic loads through creep or
   fatigue mechanisms.
    These aspects mean that the strength and stiffness of polymer
   components in service conditions are significantly lower than quoted on a data sheet.
4. Processing errors
    incorrect processing of polymer material causes failure through
    degradation and embrittlement process,
    high residual stresses,
    material inhomogeneity,
    introduction of product faults, defects or contaminants
5. Inappropriate design
    product design is fundamental to ensuring polymer component’s long-term durability.
    incorrect design will highlight polymer’s weakness to
    long term loads,
    chemical environments,
    high speed loading,
    fatigue loads resulting in failure of the product within a short service life.
6. Effect of additives:
   Even though every additives is intended to enhance or assure satisfactory performance, they can contribute to or even cause failure due to:
    Incorrect amount – too much or too little
    Incorrect additives or combination thereof – low
   compatibility in plastics (plasticisers, colourants), too high
   volatility in a certain plastic