Why resins and adhesives are difficult to pump
Resins and adhesives combine several problems in one fluid. They are viscous, sometimes very viscous; many are sensitive to air entrainment and shear; two-component systems must be dosed in an exact ratio or the product will not cure; and hot-melts and polyurethane glues set as soon as they cool, blocking any pump with a cold spot. Centrifugal pumps fail on all four counts.
A positive displacement external gear pump moves a fixed volume per revolution, so the flow is constant, proportional to speed and free of pulsation. The resin lubricates the gears and seals the internal clearances, which improves efficiency as viscosity rises. With an inverter on the motor the same pump becomes a volumetric dosing unit, and with a heating jacket it keeps thermoplastic adhesives fluid during stops. These are the same principles behind all our viscous fluid pumps.
Which series for resins, glue and hot-melt
- ZV series — dosing gear pumps born on the engine test bench: hardened and ground alloy steel gears with tolerances in hundredths of a millimetre, volumetric efficiency close to 100%, flanged directly to the motor. Ten models from 0.47 to 102 l/min for epoxy, polyester and vinyl ester resins, isocyanate and polyol, silicone and paint.
- NAV series — transfer pumps for high-density resins, isocyanates, solvents and molten polymers: nine models from 54 to 2,770 l/min, flanged ports DN 40 to DN 125, stainless steel versions for aggressive products.
- CR series — jacketed pumps for hot-melt, polyurethane glue, synthetic adhesives and polymers that solidify at room temperature; ten models from 30.7 to 2,812 l/min at 950 rpm, heated by thermal oil, steam, superheated water or electric cartridges.
Dosing isocyanate, polyol and two-component resins
In polyurethane foam, casting and adhesive lines the ratio between isocyanate and polyol decides the quality of the product. The ZV series doses each component with its own pump: flow is set by motor speed through an inverter, so the ratio is adjusted from the control panel without changing any mechanical part. The threaded ports and direct flange to the motor make the unit compact and vibration-free, with no baseplate to align.
The same approach applies to epoxy and hardener, polyester resin and catalyst, and to additives, pigments and fillers in solution. For isocyanate and other aggressive or moisture-sensitive products we supply stainless steel executions and dedicated seals; tell us the exact product name when you ask for a quotation, because the material of the pump is chosen on the chemical, not on the viscosity alone.
Transfer and heating of adhesives and hot-melt
- Hot-melt and thermoplastic adhesives: the CR jacket wraps the whole pumping chamber, so the product stays molten inside the pump during stops and the line restarts without blockage, as with bitumen.
- Polyurethane glue for panel bonding, sandwich panels and insulation boards: heated CR or ZV pumps feeding the applicator at a constant flow.
- Vinyl and water-based adhesives: NAV or ZV pumps in stainless steel, transferring from drums and IBCs to the glue spreader.
- Resin transfer in composite, coating and ink plants, from storage to mixers and from mixers to filling lines.
- Silicone sealants and polystyrene in solution, handled with the same gear pump principle.
Where no thermal plant exists, electric cartridges bring a standard pump to temperature in about two minutes under electronic control, or the hot-spot circuit heats the CR jacket with up to 900 W of electric elements.
What we need to size your resin and adhesive pump
Send us the exact product (resin type, adhesive, isocyanate or polyol grade), its viscosity at the working temperature, the temperature range, the flow in l/min, the discharge pressure, whether the duty is transfer or dosing and the accuracy you expect, the presence of fillers or solvents, and the drive you prefer. For hot-melt and polyurethane glue tell us the application temperature and the heating medium available.
Write on WhatsApp or use the quote form. Our Bologna factory, building self-priming external gear pumps since 1955 under ISO 9001:2015, replies with a technical proposal, the pump material suited to your chemical and ATEX documentation where required.
Frequently asked questions
Which pump is used to dose epoxy resin?
The ZV series: a small external gear pump flanged to the motor, with volumetric efficiency close to 100%. Flow is set by motor speed through an inverter, so resin and hardener are dosed in the required ratio.
Can resin and adhesive pumps handle hot-melt?
Yes. The CR series has a heating jacket that wraps the whole pumping chamber and keeps the hot-melt molten inside the pump, even during stops. It can be heated by thermal oil, steam or electric cartridges.
Do you have pumps for isocyanate and polyol?
Yes. Isocyanate and polyol are dosed with separate ZV pumps and transferred with the NAV series. Stainless steel executions and dedicated seals are available for the most aggressive products.
What viscosity can the pumps handle?
From medium viscosity, indicatively 50–100 cP, up to resins and adhesives that are solid at room temperature when heated. With thicker products the volumetric efficiency of a gear pump actually improves.
Is the flow affected by the pressure at the applicator?
No. The flow is constant and proportional to speed, independent of the back pressure downstream and almost free of pulsation, so the quantity of resin or adhesive delivered stays regular.