In-process monitoring of total organic volatiles during packaging film manufacturing using portable sensors

Abstract

Organic solvents are widely used to facilitate ink and coating applications during the lamination of packaging substrates using adhesives. These solvents may remain sequestered between the laminated layers due to their slow diffusion through the laminate structure. This diffusion increases the potential for subsequent migration into food. The residual solvents (also referred to as volatile organic compounds (VOCs)) in laminated films are a significant concern due to heightened regulatory, consumer, and environmental pressure in domestic and global markets. There is a need to develop in-process detection systems for packaging materials as conventional benchtop laboratory analyses are time-consuming, costly, and do not allow for 100% inspection. This work demonstrates an in-process detection system for monitoring VOCs on a commercial food grade film lamination line. This in-process detection system consists of portable sensors including photoionization detector, semiconducting metal oxide sensor, infrared sensor, and electrochemical sensor. Correlations were found between the sensor signals generated from VOC detection during the lamination process and post-conversion benchtop gas chromatography-flame ionization detector (GC-FID) analyses for several solventless and solvent based adhesives. The correlation coefficients between the readings of the electrochemical sensor and GC data were 0.75 and 0.91 for the solventless and Matte Lacquer Ethyl Acetate based adhesive, respectively. Strong positive correlations were also found among the response signals from most sensors for each type of adhesive. Linear regression modeling was completed to predict GC results from the sensor data measured in-process during the lamination process. Results showed that the sensor readings can predict the total amount of VOCs detected by GC-FID with high coefficients of determination (R 2 > 0.90) for the solventless adhesive, ethyl alcohol based adhesive and ethyl acetate based adhesive formulation two. This study is among the first that utilized portable sensors for the detection of VOCs during the film lamination process in the food packaging industry and compared the sensor readings with the results of laboratory GC-FID. Findings of this study demonstrate potential to decrease cost of laboratory analysis, improve solvent and adhesive application control, and increase traceability with nearly 100% inspection of packaging substrates utilizing in-process monitoring technologies. This study also demonstrated viability of in-process regulatory compliance for laminated packaging. • Use of portable sensors including PID and EC were used to monitor VOCs released during film lamination. • VOCs detected by the sensors correlated with GC-FID concentrations for different adhesive formulations. • Mathematical models built predicted GC values from sensor readings for several adhesives.