Determination of gel time of prepreg in copper clad laminate industry by near infrared spectroscopy

Abstract

Gel time of prepreg is an important quality determinant in the manufacturing process of Copper Clad Laminate (CCL). Prepreg consists of a glass fiber reinforcement impregnated to a predetermined level with a resin matrix. In this work, near infrared spectroscopy associated with partial least squares (PLS) regression has been applied to analyse the gel time of prepreg samples in the manufacturing process. A total of 250 prepreg samples were randomly divided into a calibration set and a validation prediction set with a ratio of 4:1. The values of Root Mean Square Error of leave-one-out Cross-Validation (RMSECV) and the coefficient of determination (R2) of the calibration model was 2.95 s and 0.92 respectively, with eight PLS factors used. The results of the paired t-test revealed that there was no significant difference between the NIR method and the reference method. The analytical result showed that, NIR spectroscopy was a rapid, nondestructive, and accurate method for real-time prediction of prepreg quality in the CCL manufacturing process.

Near Infrared-spectroscopy in resin transfer molding – determination of the degree of cure

“…It ranges from 1430 to 1500 nm and appears more as a shoulder than a clear peak. Literature assigns this peak, resulting from the conversion of the oxirane ring to a hydroxy group, between 1428 and 1438 nm [15,24,31,32]. The peak at 1540 nm results from amine groups and decreases during the curing of the resin [33,34].…”

“…Today, the suitability of NIR spectroscopy for inline process monitoring is mainly investigated for prepreg production via the solvent route. Starting before impregnation, the sizing content on the bers[16] and later in the process matrix-related parameters such as the resin content [16][17][18][19][20][21][22][23], volatile content [16][17][18][19][20][21][22][23], soluble resin content [16][17][18]21], the gel time [24], initiator content [25] and the ash content [26] have been determined for various textile and resin combinations. The quality of prepregs can also be determined during storage by NIR spectroscopy [27] in order to avoid the use of expired material.…”