The composites plant lights go out as the last finger scan goes in the time clock and the worker crosses the portal, headed for home. The production supervisor slowly walks out to the middle of the shop and stands. It feels silent as the man responsible for the daylong cacophony of production surveys the scene. The relative lack of noise enables a deep breath to relax from the furious pace of the day. Slowly, he turns to take in the panorama of composites, of the molds, parts, and equipment, now dimly lit with window light. Gradually, quiet background sounds begins to filter into his awareness. There is the hiss of the air system bleeding down through all the little leaks in the fittings. There is the sound of a damper in the ductwork rotating close because of the east wind. Little creaks and groans emanate from unidentifiable places, and suddenly a loud pop ricochets off the wall as a curing part tries to shrink its way out of the mold. The sounds of a resting composites shop.
Below the threshold of hearing, resin and gel coat slowly slip back down the spray gun lines into their fifty-five gallon drums. O-rings relax as the pressure in catalyst lines bleeds off one drop at a time, back into the catalyst jug. Molecules draw closer together as the bonds of polymerization increase the density of laminates working their way to Barcol hardness. Imperceptibly, the buoyancy of styrene begins to gather a thin film of liquid at the top of gel coat residing in a drum. At the same time, fillers coated with pigment begin a long slow plummet into the abyss at the bottom. Left undisturbed, the gel coat will become distributed with heavy pigments at the bottom, giving way to lighter hydrocarbons floating at the surface.
In the silence, violence is taking place in a drum of resin. The causes of a molecular war are fought in an ongoing struggle. Maverick free radicals slip into the structure and attempt to open the bonding sites on long chain polymers. Their goal is to react, to cause polymerization – to cure the resin. The opposing force is known by the name “inhibitor”. In a balanced system, the inhibitor intercepts the free radical and reacts before the polymer can be attacked. A molecule of inhibitor dies in the struggle, but the order is preserved. The shelf life is maintained. At some point, the violence will become purposeful. A peroxide catalyst will be added to the resin and overwhelm the inhibitor with free radicals. Cascading polymerization will result – millions of molecules per second reacting in a race to convert from liquid to solid. Most of the molecules will take the shape of a molded part.
As the compressor and air lines cool, water vapor condenses and droplets form on the surrounding walls of the tank and piping. As droplets of compressor oil are surrounded, some separate with the natural dislike between water and oil. Others emulsify into an unattractive tan film that drips down the piping ending with the line filters. During the day minor waves of the nasty tan substance will be pushed through the air lines, seeking an escape into air powered motors, or to be blown on a mold surface if not trapped in a filter.
A container of acetone sits with the lid slightly askew. Vapor forms on the surface, and if it could be seen, it gracefully wafts over the edge of the bucket and flows to the floor. Individual molecules escape and become part of the surrounding atmosphere. An ambient level of hydrocarbons could be measured with very sensitive instruments, but for now these minute quantities just add to characteristic odor of the production floor.
In a spray booth, a droplet of catalyst sits on the floor paper. It slowly reacts, oxidizing the organic substrate. Again, with hypersensitive equipment a miniscule temperature rise could be detected. However, today it is of no consequence. If the catalyst was available in a suitable mass, the reaction could become self-sustaining. The reaction could cause the temperature to rise enough to increase the rate of oxidation, which increases the temperature, which increases the oxidation rate... Today, though, the floor is clean enough to prevent any significant reaction. Tomorrow will require new attention to the matter.
A shaft of evening sunlight pokes through a window ending in a geometric pattern on the floor. Within the shaft, sparkling particles of dust swirl, dancing in thermal currents. A mold, having just shed a cured part at the end of the work-shift, sits waiting like a Venus flytrap for a victim. The mold is charged. Static electricity measured at 8,000 volts courses across the surface acting like a dust magnet. If the air is still and the light just right, you can witness the capture of airborne dust in the molds magnetic field. The particles lazily float into range and suddenly stream toward the mold, like a comet plunging toward the sun. The dust forms a galaxy of starburst patterns on the mold surface. The dust stars are a distraction to those who have to wipe them off to wax the mold. Nevertheless, when the light is right, there is a beauty in the gray on red of this natural art.
The supervisor basks in the silence for the last scan of the work area, then turns for the door. And there are sounds of resting composites.