Meaning
Liquid polymer proportioning apparatus designates industrial machinery that volumetric dosing and continuous agitation apply to reactive two part resins before potting electronic subassemblies. Thermosetting compounds such as epoxies and polyurethanes require exact stoichiometric ratios to achieve complete crosslinking inside housing cavities. Deviations from the specified mix ratio leave unreacted monomer trapped near printed circuit boards, which later softens under thermal shock and allows moisture ingress along terminal pins.
Production lines employ positive displacement piston pumps or gear pumps coupled to static mixing nozzles to combine resin and hardener streams immediately prior to deposition.
Resin Viscosity
Fluid resistance to flow dictates pump selection and pressure feed requirements across ambient temperature ranges. Unfilled urethanes flow readily under gravity feed, whereas mineral filled epoxies demand pressurized reservoirs and heated supply lines to maintain uniform volumetric output. Viscosity mismatch between the base resin and the curing agent causes uneven displacement rates within the metering cylinders.
Operators measure dynamic viscosity values using rotational viscometers before loading raw materials into the delivery hoppers. High viscosity formulations necessitate recirculating loops to prevent filler settlement during extended standby periods.
Mechanical Seal
Rotating shaft boundaries and reciprocating plunger packings prevent atmospheric moisture contamination of moisture sensitive polyisocyanates. Elastomeric lip seals wear rapidly when abrasive aluminum oxide or silica fillers pass through the metering chamber. Mechanical face seals constructed from silicon carbide provide adequate wear resistance under continuous operating pressures exceeding seventy bar.
Flush fluid systems introduce dry nitrogen gas or compatible plasticizer solvents behind the barrier interface to arrest crystallization on exposed rod surfaces. Seal failure admits ambient humidity, which reacts prematurely with the resin component and clogs the internal fluid channels.
Static Mixer
Stationary helical elements inside disposable plastic tubes divide and recombine fluid streams without moving parts. Fluid velocity forces the separated layers repeatedly against internal baffles until molecular homogenization occurs across the cross sectional area. Pressure drop across the mixing element increases exponentially as the fluid viscosity rises or the internal diameter decreases.
Excessive back pressure overheats exothermic resins, causing premature gelling inside the nozzle body before dispensing finishes. Mixing efficiency depends entirely upon maintaining correct volumetric input ratios from the primary dosing pumps rather than relying on the turbulence generated within the nozzle itself.
