Impregnation of a glass fibre roving with a polypropylene melt in a pin assisted process

The impregnation of a glass fibre bundle with a polypropylene (PP) melt is studied with a pin assisted process. A fibre is pulled over a pin, which is positioned in a chamber filled with a melt. The melt is at atmospheric pressure. The impregnation rate is studied as a function of size of the pin, the line speed, the MFI of the PP, the forces on the fibre and the effect of multiple pins. Care is taken that the fibre forces on the are kept constant. Particular attention is given to possible dry contact between the fibre and the pin. The impregnation rate without a pin in the melt bath is very slow. The impregnation with a pin seems to have two regions: one with a melt film between the fibre and the pin, and the other is a region with ‘dry contact’. The initial rate increase with fibre tension as expected from the Darcy diffusion relationship. The amount of impregnation on a pin and the moment of ‘dry contact’ are for a particular fibre tension, dependent on the contact time of the fibre with thepin. In this process, the melt is dragged into the impregnation zone between the bundle and the pin by the running fibre. The melt layer taht is dragged into the impregnation zone is at least 20 μm thick. With more pins, the impregnation occurs from both sides and the amount of impregnation is, as expected, considerably higher.