In-Line Monitoring of the Physical Blowing Agent Concentration by Transmission Near-Infrared Spectroscopy with High-Pressure Resistance Fiber Optic Probes for Foam Injection Molding Processes

Abstract

Control of the physical blowing agent (PBA) concentration in polymers is critical in achieving stable production of polymeric foams. However, there are very few in-line chemical monitoring techniques for foam injection molding (FIM) processes. The difficulty in sensor application with regard to FIM comes from nonsteady-state operations, where the temperature and pressure temporarily change dynamically. We invented an in-house fiber optic near-infrared (NIR) probe with high-pressure and high-temperature resistances and applied it to the transmission NIR spectroscopy of FIM processes to monitor the PBA, i.e., CO 2 , dissolved in the molten polymer. The CO 2 concentration was successfully monitored from the CO 2 absorption spectra at 4952 cm −1 and the polymer's absorption spectra even at a 120 MPa injection pressure and 200 °C processing temperature. Furthermore, the phase separation of CO 2 from the polymer before injection was detected from the decrease in transmittance of the NIR spectra.

In-Line Near-Infrared Spectral Monitoring of Dissolved Nitrogen in Molten Polymers during Foam Injection Molding

“…Pressure and heat-resistant NIR probes for transmission measurements were used for the in-line NIR spectral measurements. The details of the probe configuration are provided elsewhere . A pair of NIR probes was mounted between the shut-off nozzle and the screw head of a low-pressure FIM machine (RIC-FIM II: J35AD-30H, The Japan Steel Works Ltd., Japan).…”

“…We and S.T. Japan Inc. have developed an innovative pressure-resistant and heat-resistant NIR probe to enable NIR monitoring of injection molding processes . The NIR probe was installed at the barrel tip of a low-pressure FIM machine, enabling a real-time measurement of the CO 2 blowing agent concentration in the material just before injection into the mold.…”

Introducing the I&ECR Virtual Collection of Industrial and Industrially Relevant Research (2022–2023)

“…The Applied Chemistry topic area is represented with research articles across a diverse breadth of research and development topics including: foam injection molding, the preparation of mesoporous aluminosilicates, multinational studies of the catalytic pyrolysis of linear low-density polyethylene (LLDPE) in fluidized-bed reactors, and poly­(ether- b -amide) (PEBA) elastomer fatigue, an interesting longitudinal study of the optimal storage conditions for cannabis crops from New Zealand, and studies of lactate based plasticizers for polyvinyl chloride (PVC) and polylactic acid (PLA) polymers, and methyl ethyl ketone (MEK) peroxide synthesis in a continuous flow regime …”