This is the holiday of light, the darkest time of the year (OK, just in the northern hemisphere, but they do Christmas in Australia, New Zealand and South Africa, too). And light today means electricity, and electric wiring means insulation, and that means plastic extruded onto the conductors. Here we have some of the greatest die resistances and back pressures and line speeds of all extrusiondom. The flexibility and fire-retardant qualities of PVC make it a material of choice in this area, but formulation remains critical. Plasticizers vary widely in their flammability, so even if PVC is safe, the wire might not be. Buyers at the retail level won’t test flammability, so we have to trust the sellers to control what they are selling. Because the products now are mostly made at unknown locations overseas, this isn’t always easy.
Some makers used to use lead stabilizers, and our fear of this metal has generated rules that make it unwelcome and sometimes illegal. Before we get too worried, though, remember that the lead has to get into us in amounts that do us harm, which is unlikely because of the amounts used, and the need to chew and swallow the insulation. Also, the stabilizers are lead compounds, not metallic lead, and that makes a difference, too.
Another Christmas-related use of plastics is for artificial trees. PVC is the material of choice here, too, because it is flame retardant, and not much, if any, plasticizer is needed for the tree needles. I was involved in this product back in the 1960s, designing tooling to extrude tubular PVC film and X-section filaments, which were slit/cut and assembled into “branches” using brush-making machinery. The PVC film was a special challenge, as the melt path had to be very streamlined and the die easily purged and cleaned.
The impact of artificial trees has been strong enough to drive the growers of real trees into a defensive position, telling us to keep our trees in water to make them less flammable, and, sometimes, unfortunately pointing out that a “natural” tree is more virtuous than a synthetic plastic one. (The natural place for a tree is outside in the ground, not in a living room.) I would expect the preference for plastic to be safety-based, but a recent study said that buyers were mostly concerned with loose needles gathering on the floor, as well as the savings from re-using the same tree.
And my Christmas and New Year wish for you all:
May you live and work and give and love honestly and peacefully. The currency of love is time. And may the light of law-abiding science illuminate your life; may you ask the question “why” and not run from the answers; may you be proud of your work and materials; waste little; and use your time wisely, half to the future, half to the present and half to the past.
Allan Griff is a veteran extrusion engineer, starting out in tech service for a major resin supplier, and working on his own now for many years as a consultant, expert witness in law cases and especially as an educator via webinars and seminars, both public and in-house. He wrote the first practical extrusion book back in the 1960s as well as the Plastics Extrusion Operating Manual, updated almost every year, and available in Spanish and French as well as English. Find out more on his website, www.griffex.com, or e-mail him at [email protected].
Griff conducts live seminars across the country. The next ones are scheduled for Los Angeles in February and Baltimore in March. Seminars in your plant are also available. If you can’t attend his live events, he offers a Virtual Seminar, which can be seen at anytime, anywhere. E-mail Griff at the address listed above for more information.
Image courtesy 3desc/Abode Stock.