Article and photos by Gregory Havel
Plasticsare part of a class of chemicals called “polymers”–giant molecules made up of thousands of smaller molecules of chemicals called “monomers,” which are unstable and have the ability to react with themselves to form the much larger polymer molecules.
Monomers and polymers are hydrocarbons, a type of organic chemical. Polymers can be either naturallyoccurring, like the cellulose that makes up wood, cotton, paper, and cardboard, or man-made synthetics, like vinyl, styrene, and acrylics. Most man-made polymers begin their life as petroleum-based chemicals called “monomers.”
During transportation of monomers, the polymerization reaction is prevented by controlling the temperature and pressure in the tank andadding chemical inhibitors. During a polymerization reaction, the reaction of the monomer with itself is carefully controlled by temperature, pressure, limiting the quantities in the reactor, and using chemical inhibitors to slow the chemical reaction. If a polymerization reaction becomes uncontrolled or “runaway,” it can cause the rapid release of an enormous amount of heat, a great increase in pressure, and the boiling-liquid, expanding-vapor explosion (BLEVE) of the container or chemical reactor.
Some of the synthetic monomers, their UN numbers fromthe Emergency Response
Guidebook, and their most common polymer formsfollow:
- Acrylonitrile (UN 1093) + Butadiene (UN 1010) + Styrene (UN 2055): Acrylonitrile butadiene styrene (ABS)
- Methyl methacrylate (UN 1247): acrylics
- Acrylonitrile (UN 1093)(vinyl cyanide): polyacrylonitrile (PAN)
- Bisphenol-a and Phosgene (UN 1076): polycarbonate
- Ethylene oxide (UN 1040): polyethylene (PE)
- Propylene oxide (UN 1280)(propene): polypropylene (PP)
- Styrene monomer (UN 2055): polystyrene (PS)
- (reaction of diisocyanates with polyalcohols and a catalyst): polyurethane (PU)
- Vinyl chloride (UN1086): polyvinylchloride (PVC)
- Perfluoroethylene: Polytetrafluroethylene (PTFE; (DuPont Teflon®))
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These polymers and plastics have many common uses in residential and commercial construction materials:
1.Insulation: foam board, foamed-in-place
2.Insulated sheathing: polystyrene, polyisocyanurate, polyethylene, other
3.House wrap
4.Vapor barriers
5.Fasteners for house wrap: Plastic washers on nails (photo 1)
6.Plastic anchors for concrete, masonry
7.Exterior cladding: vinyl siding, trim, and other materials
8.Porch and deck railing materials (photo 2)
9.Ductwork, including spiral-wire plastic duct with insulation and plastic facing
10.Heating, ventilating, and air-conditioning (HVAC) air supply (photo 3) and vent pipe
11.Electric conduit and conductor insulation
12.Plumbing fixtures: bathtubs, showers, laundry tubs, sinks, washer boxes (photo 4)
13.Drain tile, left-in-place concrete forms, waste and vent piping, water piping (photo 4), radiant heat tubing
14.Electrical wiring, boxes (photo 4), devices, and fixtures
15.Fire alarm system components: horn-strobes, pull stations, smoke detectors
16.Insulation vents in attic eaves
17.Soffit and fascia panels
18.Gutters and downspouts
19.Roofing materials and skylight panels
20.Central vacuum system pipes and ducts
21.Dryer vent pipe
22.Fuel gas piping
23.Exhaust and air-supply fans
24.Safety glazing: acrylic, polycarbonate, other
25.Flooring: vinyl composition tile, sheet goods, carpet, baseboard, fake ceramic tile
26.Door hardware
27.Vibration isolators and expansion joints (duct and pipe)
28.Fire sprinkler piping, residential: CPVC
29.Paint and wood finishes: acrylic, polycarbonate, polyurethane, latex
30.Millwork, trim, box beams, and cornices use a variety of extruded and foamed plastics
31.Countertops: plastic laminates and solid materials
32.Window sash: solid plastic, plastic-clad wood
33.Exterior insulating foam system (EIFS)
34.Exterior door/frame assemblies, including overhead doors
35.Supports and isolators for pipes and cables in steel stud construction
36.Electrical insulators
37.Caulk and sealant: polyurethane, acrylic, silicone, other
38.Adhesives
39.Expansion joints
40.Wall covering: vinyl, other plastic, synthetic, or natural fabrics
41.Suspended ceiling tiles: plastic film-faced fiberglass
42.Door and drawer bearings and rollers: nylon or other plastics
43.Sanitary cladding: fiberglass-reinforced plastic (FRP)
44.Concrete reinforcement: glass or plastic fiber; epoxy-coated rebar, plastic rebar
45.Imitation ceramic wall tile
46.Wood-frame construction (cellulose, a naturally occurring polymer)
47.More uses loom in the future.
Common features and hazards of polymers and plastics used in construction are the following:
- They can be manufactured to look like other materials, including wood and metal.
- They are often less expensive than the materials they imitate.
- They are available at any hardware or home-improvement store.
- They are all hydrocarbon-based, including cellulose, and all will burn, although some will self-extinguish when the ignition source is removed (thermosets).
- Synthetic polymers burn hotter and faster than cellulose-based materials and produce more types of toxic products of combustion.
- Some types of synthetic polymers can melt, drip and run, and burn like flammable liquids, in addition to burning in place like a combustible solid.
Most of these plastics have been in common use for more than 10 years, and many of them have been in common use for more than 50 years. Even if the use of plastics in all future constructionwere banned today, these features and hazards would still be present for firefighters
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