Why Plastic Products Fail

The development of plastics and their associated processing techniques has been a phenomenal episode in the history of materials science. With large scale development taking place only within the last 60 years, the use of plastics in product design and manufacture has spiraled at a rate unrivaled by conventional materials. Due to the wide spectrum of properties available, plastics have become one of the most sought after materials in the world today.

More plastics are now available to the designer and engineer than at any previous stage in the history of industry. Today there are over 90 generic plastics and around 1000 sub-generic modifications with 50 thousand commercial grades available from over 500 manufacturers.

The short history of plastic development and proven usage has meant for the designer and engineer that for critical engineering applications there has never been enough time to fully explore service life and problems that might occur during the use of plastics. There has always been the question of vulnerability to failure and the ramifications of potential 레플리카쇼핑몰 litigation. To some degree this situation has improved, as the portfolio of successful plastic designs has grown in demanding engineering applications. However, for new innovative applications pushing the boundaries of material performance the problem remains.

Designing to ensure plastic product reliability is critical due to the increasing importance of:
Product liability can be the most damaging with settlements and penalties in the order of thousands or even millions of pounds, particularly when failure has resulted in personal injury or death. In addition to litigation financial costs, there is the distraction of key employees from normal duties, loss in product perception, brand credibility and manufacturer reputation.

Considering that approximately 70% of plastic products fail prematurely, failures have been poorly reported since the owners of failed products are naturally generally reluctant to publicise the fact. Failure investigations of such cases tend not to be disseminated due to client confidentiality agreements and for this reason the activity is predominately covert. As a consequence the potential benefits such as learning from the mistakes and misfortunes of others, and identifying priorities for research and critical issues in product development are far from being fully exploited.

It is clear from the extent of plastic and rubber failure investigations conducted by Smithers Rapra that limited dissemination of plastic and rubber failure knowledge within the public domain has resulted in a continual cycle of plastic and rubber failure incidents from all industrial sectors. The lessons of good plastic and rubber product design are not being learnt even in light of the enormous growth in product liability cases that have imposed an entirely new dimension on the consumer product environment. It is now well established in law that manufacturers are liable for injuries resulting from defective product; for injuries from a hazard associated with a product against which the user should have been warned; or for damages caused by misapplication of a product which could have been foreseen by the manufacturer.

It is a practical necessity to understand why plastics fail in order to minimise the failure scenario. Smithers Rapra has acquired this knowledge due to 50 years dealing with a diverse clientele providing technical services aimed at problem solving and in particular failure diagnosis.

Failure is a practical problem with a product and implies that the component no longer fulfils its function. Frequently, the ability to withstand mechanical stress or strain (and thereby store or absorb mechanical energy) is the most important criterion in service and consequently mechanical failure is usually a primary concern. However failure may also be attributed to loss of attractive appearance or shrinkage.

In order to avert product failure it is critical that at all stages of the design process there must be a concurrent engineering approach to product development. This system ensures that from inception of the project until final high volume manufacture all parties involved (marketing, industrial design, product engineers, plastic expert, tooling designers/engineers and processors) continually communicate in order to take advantage of the valuable knowledge and experience of all. Key to successful design is that all aspects of the performance, production, assembly and ultimate use of the part are considered. Furthermore all parties promote building reliability and safety into the product.

In order to reduce the likelihood of product failure all parties within the design process must have the ability to imagine how their designed plastic part could fail. This can only be achieved if the product design team has a good appreciation of plastics material selection, product design, processing and specific material weaknesses and fault/ failure modes and avoidance.

Plastic product failure is commonly associated with human error or weakness and is typically associated with the factors shown in figure

In an attempt to reduce the incidence of plastic product failure we must react to the fact that they are typically due to human error, misunderstanding and ignorance of plastic materials and associated processes and that the material or process is usually not at fault.

It is hoped that the following information will provide some insight into complexity of plastics design and plastic failure modes.

Poor Material Selection / Substitution
Failures arising from incorrect material selection and grade selection are perennial problems in the plastics industry. In order to perform plastic material selection successfully a complete understanding of plastic material characteristics, specific material limitations and failure modes is required. Good material selection requires a judicious approach and careful consideration of application requirements in terms of mechanical, thermal, environmental, chemical, electrical and optical properties. Production factors such as feasible and efficient method of manufacture in relation part size and geometry need to be assessed. In terms of economics the material cost, cycle times and part price need to be considered.

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