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52 DESIGN007 MAGAZINE I AUGUST 2018 Earlier this year, I began my new series of col- umns on resins. I selected five frequently asked questions that I hear from customers on such subjects as resin chemistries and properties and typical resin applications and their limitations. I followed this up in a later column by compiling what I believe are the five top tips for those circuit designers and manufacturers who are frequent spec - ifiers and users of resins and want to get the best out of them. This month, my column has a bit of a testing theme running through it, and I include my responses to more technically probing questions. In no particular order, here are five ques- tions from customers that raise sev- eral technical issues related to resin applications, together with my responses. Hopefully, it will pro- vide useful background informa- tion to help you with your own problem-solving activities. Q. What weathering resistance tests can be performed on resin products, and how are the results of these tests translated into meaningful data that users can apply with confidence to real- world applications? A. Let's address the easy ques- tion first. How closely weathering test data relates to the real world has been exer- cising the minds of both the suppliers and users of resins since weathering tests were first devel- oped. The main problem here is that a weather- ing (environmental and mechanical exposure) test rigs/regime will, at best, only cover two or three condi- tions, whereas in the real world, things are far more complex and difficult to predict. Te s t i n g i s a fundamental pro- cess. Electrolube carries out a range of ther- m a l cyc l i n g (checking ther- mal shock resis- t a n c e ) , w a t e r immersion (fresh a n d s a l t ) , a n d chemical resistance, covering both atmo- spheric pollution as well as direct contact with corrosive or otherwise reactive substances. In addition, thermal stability checks are run at continuous operating temperatures and exposure to artifi - cial daylight to determine the ultravi- olet (UV) resistance/stability of the resin under test. By combining the information gleaned from these tests, design engineers can select a resin that best fits their requirements. In many cases it is possible to input the results obtained into a model and undertake a FEMA study, Testing Time for Resins Sensible Design by Alistair Little, ELECTROLUBE