Magnum Venus Plastech Impregnator Roll - Manual (Page 21)

CHAPTER 8
AIR INCLUSION IN LAMINATE
Contrary to first impressions, the Impregnator does not squeeze resin into the reinforcement. If
the nip of the resin rolls is set in such a manner that they actually squeeze the glass, any resin
in the material would be forced out just like the old washing machine clothes wringers, and the
laminate would be very dry and high in glass content. In actual practice, the nip of the resin rolls
is slightly wider than the reinforcement is thick. As the glass material passes through the resin
bath it is wet-out and as it goes through the nip of the rolls the proper amount of catalyzed resin
is allowed to pass through with it, governed by how wide the roll setting is.
It becomes apparent, when the Impregnator method is analyzed, that if a given laminate is
processed through the unit, a slow rate will allow more time for wet-out and better impregnation.
The same laminate run at a faster rate will have more air inclusion because the material does
not have time to wet-out completely before passing through the nip of the rolls. The thickness of
reinforcement and/or the tightness of the weave becomes the governing factor in the rate at
which it can be processed. The tighter the weave or thicker the laminate, the slower the rate will
have to be.
When processing woven roving, complete air removal is next to impossible if a reasonable
production rate, with minimum secondary work, is expected. This is because of the air
entrapment where the weave and the warp cross. Because of the double thickness of material
at these intersections and the small air pocket that is formed, a vacuum bag process would be
required to make the laminate 100% void free. Very few products require this type of quality
laminate and therefore a compromise is in order; allowing minimum number of small air voids
which in turn will allow a more rapid rate of impregnation.
The problem with woven roving is compounded by going to a heavier material and/or a tighter
weave. A tightly woven material sets up a fluid barrier that will not allow resin to pass through
the strands of glass and wet them out. Keeping this problem in mind when designing
reinforcement requirements for a particular product, will save much labor and allow a much
faster rate of production with the Impregnator unit.
Processing chopped strand mat, and like materials, also prevents some impregnating problems.
The heavier a mat material is, the slower it must be processed. Additional binder in the mat,
giving it added wet strength, (which is needed for processing mat without a carrier) will also
require a slower production rate. The heavy binder acts as a fluid barrier and a slow rate is
required to give the material time to wet-out as it passes through the resin bath.
A certain amount of air inclusion can be tolerated when high production rates are required if the
proper air removal method is employed on the secondary operation.
The unique design of the thin finned laminating roller allows air to escape up and through the
fins of the roller as the reinforcement is pushed down into the resin. When using other types of
laminating roller, the air is pushed forward, in front of the roller, and must be worked to the edge
of the laminate before it can escape.
To use of the squeegee: This method of air removal works well for woven materials. The
pressure action of the squeegee, as it passes over the laminate, pushes the trapped air up and
out of the laminate. This type of air removal does not work with reinforcement materials that do
not have the integrity to hold together after they are wet-out, such as chopped strand mat.
For top quality laminates, such as corrosion applications or laminates laid on a gel-coated
surface, air removal is a must. The impregnation rate must be slow enough to allow the glass to
be thoroughly wetted and the operator to trap a minimum amount of air between laminate and