Rheological Analysis
Experimental testing techniques that measure the deformation and flow behavior of a viscous polymer between two parallel plates under load determine prepreg processability. Squeeze flow plastometry assesses the rheological properties of uncured resin systems during the laminate pressing stage. This test is executed to evaluate how a prepreg’s viscosity changes under compressive stress and temperature.
It establishes the limits of laminate thickness control.
Measurement Protocol
A sample of prepreg material is placed between two heated metal plates of a plastometer, and a constant compressive force is applied to deform the sample. As the temperature rises, the resin melts and flows outward, and the sensor tracks the rate of plate closure over time. The resulting displacement curve reveals the resin’s gel time, minimum viscosity and flow rate under load.
These parameters are critical for predicting how the prepreg will behave in the multi-layer lamination press. If the flow rate is too high, the resin will squeeze out of the laminate, leaving dry spots.
Press Optimization
Data from this testing are used to calibrate the temperature and pressure profiles of the manufacturing press. Adjusting the press cycle to match the measured resin behavior ensures that the multi-layer boards are produced with consistent thickness and high internal bond strength. This calibration reduces defects in multi-layer production.
