Thursday, May 08, 2008

Vinyls vs. PVC, What is What?

I just found this when I researched buying these reusuable sandwich bags I use for the kids. One side is cloth and the other side is wipeable/cleanable plastic that's PEVA. They are about $6 a piece. I spend that on a couple boxes of plastic bags not to mention how much they add to my list of environmental infractions. I decided to be a jerk and buy them as teacher gifts. This isn't California, it's stodgy old New England where we are a bit behind on "green " stuff like that. Boy will I be unpopular, but I don't care. This year's theme is "It's All About ME." I'll go ahead an force my values on my well meaning AWESOME teachers that we've had this year. Of course, I'm too lazy to give credit where credit is due regarding the plastic info...that's my mood for today and I'm too tired to fight it. ResusableBags.com also has water bottles (other than Nalgene) and other pricey greeny thingys. Fun fun fun!



Sorting out the Vinyls – When is "Vinyl" not PVC?

Vinyl is commonly used as a shorthand name for polyvinyl chloride (PVC) plastic as used in a range of products from flooring to siding to wall covering. Most commonly, when a product is referred to as "vinyl," it is comprised primarily of PVC. Occasionally it also may refer to polyvinylidene chloride (PVDC) a closely related compound, used in food wraps ('Saran') and other films, that shares most of the same environmental health problems.

In chemistry, however, the term "vinyl' actually has a broader meaning, encompassing a range of different thermoplastic chemical compounds derived from ethylene. In addition to PVC, "vinyls" in building materials also include:
- ethylene vinyl acetate (EVA), used in films, wire coating and adhesives
- polyethylene vinyl acetate (PEVA) a copolymer of polyethylene and EVA used in shower curtains, body bags
- polyvinyl acetate (PVA), used in paints and adhesives, such as white glue, and
- polyvinyl butyral (PVB), used in safety glass films.

What differentiates PVC from the other vinyls is the addition of a chlorine molecule (the chloride "C" in PVC and PVDC). Chlorine is the source of many of the environmental health concerns with PVC, such as the generation of dioxin, a highly carcinogenic chemical produced in both the manufacture and disposal of PVC. Due to its persistent and bioaccumulative nature (it travels long distances without breaking down and concentrates as it moves up the food chain to humans) dioxin has become a global problem and an international treaty – the Stockholm Convention on persistent organic pollutants (POPs) - now prioritizes the elimination of processes that produce dioxin.

Some of the non chlorinated vinyls (EVA, PEVA, PVA and PVB) are now beginning to be used as direct substitutes for PVC. EVA has been in use for several years as a chlorine free substitute for PVC – primarily in non building materials like toys and athletic shoes, but occasionally as a protective film or binder. In the building industry, post-consumer recycled PVB is now beginning to be used to replace PVC in carpet backing. Absence of chlorine alone does not make these other vinyls the final answer in the search for green polymers. There are still plenty of toxic challenges and untested chemicals in the life cycle of any petrochemical product. As is the case with most other polymers competing with PVC, however, the weight of available evidence indicates that the absence of chlorine in the formula will generally render the lifecycle environmental health impacts of PVB and the other vinyls less harmful than PVC and initial study is bearing this out. Like the polyolefin plastics, the use of PVB and the other non chlorinated vinyls represents a step forward in the search for alternatives to PVC.

In summary, with the exception of paints, glues and certain films, "vinyl" as a product description almost always means made of PVC. The term vinyl in ethylene vinyl acetate (EVA), polyethylene vinyl acetate (PEVA), polyvinyl acetate (PVA), and polyvinyl butyral (PVB), however, does not refer to PVC and does not raise the same concerns associated with chlorinated molecules like PVC.

When in doubt about the use of the term "vinyl", ask if it is PVC.

1 comment:

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