PVC Jacket Ratings, what's the deal?
Dave Watson, Director of Engineering, also known as Alpha Wire's resident wire and cable expert was prompted with the question below regarding PVC Jacket ratings. Check out Professor Watson's explanation!
Q: I’ve noticed a great deal of inconsistency in the ratings of your PVC jackets. Some have Oil Resistance, some do not. Some have UV resistance, some do not. Additionally there is a pretty big difference in temperature ratings. How do you explain all this?
A: Oh Boy! Have I ever mentioned that my degree is in electronics and I’ve not had a chemistry class since my sophomore year in High School? Actually, all kidding aside, the basic concepts are pretty easy to explain. The PVC’s we use are technically called PVC compounds. They start with a polymer substance called PVC (Poly Vinyl Chloride). To this we add plasticizers, fillers, flame retardants, stabilizers, etc. etc. to arrive at a PVC compound. In each of the categories I just listed, there are many different choices for what we use. The Chemist designing a particular PVC compound will look at the specifications they are try to achieve in the PVC Compound (these are the things you mentioned plus hardness and the amount of flame retardants) and select the specific ingredients to use and the relative amounts of each. Some things are easy to explain. You want a softer compound? Use more plasticizer. You want more UV resistance? Add a UV Stabilizer. The hard part, and where our chemists earn their keep is that as with most things in life, there are tradeoffs. For example, using more plasticizer, will generally be adverse to flammability. And just keeping on the subject of plasticizers, there are many to choose from that each also have their pluses and minuses. As it turns out, the exact plasticizer we use is what primarily determines Oil resistance. There are also things that tend to be mutually exclusive like a PVC Compound with excellent cold temperature properties and excellent Oil resistance (since you specifically mentioned Oil)
So really what we do is try to look at the applications are cables are designed for and select the PVC compound that is the most cost effective cost for the required performance. I did not mention this above, but cost is certainly also something that needs to be carefully considered in the formulation. So PVC compounds fit in the old adage “you get what you pay for.” The higher performance in terms of temperature and chemical/environmental resistance will result in a more costly compound. The cost per pound of PVC can range from about $1.00 to $3.00 just for non-plenum rated grades! Our factories would doubtless rather use just one or two different grades, but we have a manageable number of grades in our tool box which allow us to meet a wide range of requirements. The bottom line is that if you don’t see the performance you want in one of our cables, let us know what your requirements are and we’ll see if we can engineer you a solution.