Mixing process tolerance capability

The process consists of a thin, unreinforced outer coat called a gel coat. The reinforcement (normally glass fibers) mixed with resin (usually polyester) is then applied by hand (lay-up) or via a spray gun (spray-up). When the desired amount of resin and reinforcement is in the mold, the air bubbles are pressed out with a roller. The part is then left to set up which, depending on the size of the part and the amount of resin, can take more than an hour. Consequently, many molds are used when higher production volumes are required. The molds themselves are made of plastic cast from a pattern. As such, they have a very short life and must be replaced frequently. Fortunately, they are inexpensive imfortunately, they are not capable of producing fine detail or close tolerances. Since the mold has only one side, only that side of the part has a finished surface the other side is very rough. The... 

Some viscosity may be expected to develop during the solution polymer stage of the polymerization. While the extent and duration of the viscosity that can be tolerated is a fimction of the agitation efficiency and heat removal capability of the reactor, the salt concentration is the primary parameter to be adjusted in order to obtain the optimum in-process viscosity. If the salt concentration has been properly adjusted, then at the onset of the precipitation event the viscosity of the system ops markedly and the polymerization is finished as a dispersion. If the salt concentration is too low during the polymerization, the precipitation event and transition to a heterogeneous system never occurs, and effective mixing and heat transfer will eventually be lost. If, on the other hand, the salt concentration is too high, the dispersion will have little thermodynamic stability in the absence of mechanical shear. 

---