Application of factorial design to SMC viscosity build-up

Summary The thickening behavior of SMC varies with formulation and operating conditions. During the SMC compounding process, alkaline oxides such as MgO, Mg(OH)₂, CaO, Ca(OH)₂ are added to the formulation to yield the viscosity build-up from a flowable paste to a semi-solid sheet. The thickening curve of SMC can be divided into three stages: 1. The initial thickening period for the wetting process, 2. The middle thickening rate period for viscosity increasing, 3. The final viscosity period for the molding process. By means of factorial design with an appropriate objective set-up, one is able to define the influence of each factor on thickening curves. Combined with the experimental work on some individual factors, the maturation control system can be further understood and the proper thickening rates can be obtained.