I am not a very good driver when it comes to freeway. I usually drive a certain patch of freeway on my way to work. Majority of the time I believe there is a cop waiting for me holding a radar gun that points to the traffic. I guess most of us know that there is a high chance that the cop is there on his post every time we drive past. Still my fellow drivers just keep on slamming on their breaks when they spot the cops. But in line with this, we all push the different limits of what we know what’s right or what should we do or what we should not. But still we get away with the things that we should not be doing. When something like this happens, we quickly learn not to repeat the same mistakes again right?
With this in mind, I would like to prevent you from learning this lesson in the hard way. Plastic boxes also have limitations too – in terms of temperature. Some of the enclosure plastic materials tends to have a higher temperature rating compared to others. Regardless of what the rating is. Once the temperature already reached the required temperature, the engineer is already risking deformation and loss of shape.
What is RTI or Relative Thermal Index?
Let us define what RTI is. It is formerly known as CUTR – or Continuous Use Temperature Rating. This is the highest limit of service temperature, where the critical properties of the material should remain inside the acceptable limits. There are about 50% after 10 cycles, and this is according to the UL testing.
With this in mind, RTI is the external indicator of the material’s innate properties. However, there is a limitation to this. RTI does not consider some of the specific application factors such as the stresses that are inherently molded and mixed into a part before the external load is going to be applied. Including in this is chemical exposure, part thickness, etc. The only most reliable method in predicting part performance is to have the prototype part be subjected into a test under some actual conditions.
There are three independent RTI ratings that can help us with this:
- The electrical measures effectively measure dielectric strength
- The mechanical part has an impact with measurement of tensile impact strength
- The mechanical part that exists without impact measures the tensile strength
For other enclosure manufacturing companies, the standard flame-retardant ABS or the RTI temperature is up to 80 degrees. However, just like my fellow drivers on the freeway, they can only drive up to 10 miles over the limit. It is then most possibly safer in driving at a slower rate than that.