A Vacuum and/or Pressure Forming System Using a Prepreg Sheet of FRP with a Gel Coat Layer

Abstract

This paper introduces a new vacuum and/or pressure forming system using a prepreg sheet which consists of two thickened layers of unsaturated polyester, i.e., FRP (Fiber Reinforced Plastic) and gel coat layers, sandwiched by two stretchable films. The efforts were focused on the development of sheet construction, material properties and processing conditions. The difficulties in the development of this system are found in;

1. uneven thickness distribution in a molding

2. vaporization of vinyl monomer

3. gel coat cracks

These difficulties were solved by the chemical modifications of resin such as;

1. unifying the apparent tensile modulus of each layer by controlling the viscosity

2. reducing the maximum exothermal temperature

3. shortening the gel time

and by the physical modifications of processing conditions such as selection of an appropriate forming rate.

The expected application area of this new system is also mentioned briefly.