Resin Flow and Injection

Irregular flow and pressure during the mold-filling sequence can cause waviness, dry patches and overloading. Since many advanced RTM resins are solid or highly viscous at room temperature (and therefore all machine hardware must be thoroughly heated), a compact injection machine needs to have custom-fitted heated mantles on the reservoirs, pumps, fittings and mixers to eliminate any cold spots. 

The heating capability is from ambient to 150C (300F) and insulation ensures that, even when operating at over lOOC (212F), the exterior is only warm to the touch. A modern machine is kept to 760 x 1000 mm (2.5 X 3.30 ft) floor space. One or two components can be injected, maintaining pre-programmed pressures of between 140 and 2050 MPa the ratios are from 1 1 to 150 1, flow rates up to 1500 cmV n and flow rate and injection pressure are both controlled. 

A low-pressure injection system, with 4 1 ratio pump at 9.5 liters/min output, is available, with a stainless steel catalyst delivery pump offering rates of 0.5 to 4.5%. The injection gun has a single moving valve, which shifts when the gun is activated. The system includes complete loop recirculation, air logic maintaining consistent static and dynamic pressure, and a stroke counter located at the injection gun. 

Low-cost injection systems have been developed for RTM systems. The Spartan and VR-2 units, respectively, inject TS polyester and vinyl ester systems with a catalyst content ranging from 0.5—4.5% and can handle closer ratio mixes, as for epoxy or hybrid systems. The two can be combined in a single unit (VR-3). 

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