Delivered as part of the RAPRA technical session at the Plastics Design & Moulding (PDM) Tradeshow 2015

Justin Taylor Principal Consultant Ipolytech © 2015 Independent Polymer Technology Ltd

“With few exceptions we cannot blame an inanimate material or hold it responsible for our failures” – DC Wright- Failure of Plastics and Rubber Products © 2015 Independent Polymer Technology Ltd

Will my product fail? All products will fail at some point in time. The time to failure and mode of failure can, to a significant extent, be controlled / predicted Balance of cost of testing versus consequence of failure

Why bother? Understanding how plastic products fail allows us to reduce premature failures and enhance performance and profit. Reduce product warranty claims and recalls Avoid litigation Wasted time on failed designs and concepts Improve market confidence and sales Avoid over engineering

Assessing Failure of Plastic Products Rarely is there a single cause of failure Failure is often the result of a chain of events from product conception to the end user. We have control over many of the factors affecting product performance. Failure doesn’t just happen

Failure of Plastic Products Rarely is there a single cause of failure Control handle failing in a brittle manner.

Failure of Plastic Products Rarely is there a single cause of failure Poor design including sharp corners at regions of peak stress. Stress concentration

Failure of Plastic Products Rarely is there a single cause of failure Flow path from thick to thin back to thick sections. High moulded in stress and void formation

Failure of Plastic Products Rarely is there a single cause of failure Polycarbonate - mouldings exhibited silver streaking due to moisture from poor drying of granules. Hydrolytic degradation

Failure of Plastic Products Rarely is there a single cause of failure Control handle failing in a brittle manner.

Materials Materials selection Additive selection Material Supply Additive Supply Degradation in Compounding Storage of materials Contamination Processing Incorrect conditions Degradation Poor process control Contamination Dispersion of fillers Defects – voids etc. Moulded in stress Assembly processes

Storage UV Ageing Thermal Ageing /Cycling Humidity Microbial attack Chemical Attack/ ESC Interaction with Packaging etc Service Loads Mechanical Stress Electrical Stress Tolerance stack-up

Environment UV Radiation Thermal Chemical Gases and Vapours Migration Unplanned Chemicals Temperature spikes Load spikes “The perfect storm”

Human Factor Misuse Malicious damage Poor design Lack of knowledge of material /process limits Failure to follow manufacturing procedures Secondary intervention – after market mods Installation errors Use of internet published data Servicing of product (positive intervention)

Key Control Points Design Specification Testing Quality Control Product monitoring – verification of test

Control Points Design – Material selection – Avoid stress concentrations – Long term creep and fatigue data for long term performance – Awareness of the effect of working environment on physical performance – Design for manufacturing

Control Points Testing – Select test methods appropriate to the application. – Understand the test methods specified in industry guidelines and what they achieve. – Test to failure not to an acceptance level – Be careful of over accelerating tests

Control Points Specification – Define a detailed specification of requirements – Where possible set realistic quantified requirements – Where possible specify grade and quality of material. If you allow alternate grades, then verify their performance

Control Points Quality Control – in addition to a robust quality auditing system – Identify check points at design stage and review throughout prototyping and production – Ensure QC tests prevent failure – Retain samples at all stages of manufacture – If relying on supplier documentation read it /confirm it

Control Points Product monitoring – verification of test – Test products obtained from service to verify performance is as predicted – Subject product to long term testing with record of environment and corresponding performance to verify accelerated testing – Test failures against your retained samples – Determine all factors in failures do not just assign one cause e.g. impact and then stop. – Feedback lessons learnt into the design, test protocols, specification and quality systems

Control Points Design Testing Specification Quality Control Product monitoring – verification of test

Failure it doesn’t just happen Understand your materials Accept your power to control life expectancy of products Learn from failures in your industry and others Keep improving Suppliers Materials Testing ManufacturingTraining