Quality Control Of Adhesive Products Using Raman Spectroscopy

INTRODUCTION

Adhesive products play a vital role in various industries, including automotive, aerospace, electronics, and healthcare. The quality of adhesives directly impacts the performance and durability of assembled components and products. Traditional QC methods often involve time-consuming sample preparation and destructive testing, which can be inefficient and costly. The objective of this application note is to demonstrate the application of Raman spectroscopy in the quality control (QC) of adhesive products. Raman spectroscopy offers a non-destructive and rapid analytical technique that can provide valuable information about the chemical composition and structure of adhesive materials. This information is crucial for ensuring the consistency, reliability, and performance of adhesive products in various industrial applications.

Chemical analysis is often used to ensure both the purity and quality of cosmetics. Spectroscopic techniques provide powerful tools for cosmetic ingredient analysis, contaminant detection, and product formulation verification. Spectroscopy does not require complicated sample preparation steps, does not destroy the analysis sample, and gives accurate analysis results in a fast time to help improve efficiency. This application note explores the application of spectroscopy in toxicology and quality testing in the cosmetics industry.

METHODS

Raman spectroscopy is based on the inelastic scattering of photons when a sample is irradiated with monochromatic light, typically from a laser source. The scattered light undergoes frequency shifts that correspond to vibrational modes within the molecular structure of the sample. By analyzing these frequency shifts (Raman shifts), detailed information about the chemical composition, molecular structure, and crystallinity of the adhesive sample can be obtained.

In addition, when monitoring Raman spectra continuously in real-time, it is possible to monitor the curing process of adhesives. This is also a common application in the industry. In addition, with the combination of advanced algorithms and data processing methods today, it is completely possible from Raman spectra to detect contaminants and impurities in adhesives, helping to improve the performance of products and their shelf life. Moreover, this combination can help analyze the interface of the adhesive with the substrate to ensure the most optimal bonding properties.

Many practical applications in various industries have applied Raman spectroscopy to evaluate the quality of their adhesives. Here, we present some of the specific applications:

Figure 1: Raman spectra of the measurement time series

The Raman spectra in Figure 1 were measured during the curing of an adhesive used in the automotive industry. The changes in the spectra are very obvious as the curing process proceeds. Most of the signals decrease or disappear completely with time. However, at two positions, 813 cm-1 and 967 cm-1, there is a gradual increase in the signal. Most of the changed spectral features decay during the curing process, while only a few new features appear. This is mainly because the polymerization process reduces the functionality of the chemical components by using up all the functional groups (unsaturated acrylic bonds, initiators, accelerators), which are replaced by mostly single bonds. They have less inherent Raman activity and their signals are also significantly broadened due to the heterogeneous network structure of the resulting polymer, making them much less noticeable. Based on this, the user can identify the time required for the application.

SYSTEM

The Raman spectroscopy system utilized for evaluating dentin adhesives included the HDX  spectrometer, a 785 nm laser for Raman excitation. This setup allowed for precise and detailed analysis of the chemical composition and molecular structure of the adhesives, facilitating the assessment of resin infiltration, degree of polymerization, and hybrid layer formation.

The Ocean HDX spectrometer from Ocean Insight is a scientific-grade instrument known for its high sensitivity and stability. This miniature modular spectrometer operates over a wavelength range of 200-1100 nm, making it suitable for various applications. The Ocean HDX model specifically for Raman spectroscopy uses an excitation wavelength of 785 nm, providing excellent performance for detecting Raman shifts from 150 to 3400 cm⁻¹. It optimized components and precision engineering to maximize optical resolution, increase throughput, reduce stray light, and maintain thermal stability for integrated, industrial and research applications. Moreover, HDX has a back-thinned CCD array and “High Definition Optics” design to deliver an exceptional level of spectral performance for a compact, UV-Visible spectrometer.

Figure 5 HDX Spectrometer

The Ocean Insight 785 nm laser Raman spectrometer is a highly precise instrument designed for Raman spectroscopy applications. This spectrometer features an excitation wavelength of 785 nm, which is ideal for minimizing fluorescence interference while maximizing the Raman signal. The device operates over a spectral range that allows it to detect Raman shifts from 150 to 3400 cm⁻¹, making it suitable for a wide array of materials analysis.

Figure 6 Ocean Insight 785 nm Raman Lasers

CONCLUSION

Quality control of adhesive products using Raman spectroscopy with the HDX spectrometer from Ocean Insight offers significant advantages in precision and reliability. The HDX spectrometer, with its 785 nm excitation wavelength, provides high sensitivity, minimizes fluorescence interference and it’s crucial for accurate chemical analysis of adhesives. Raman spectroscopy with the HDX enables detailed characterization of adhesive composition, degree of polymerization, essential for ensuring the performance and durability of adhesives, making the HDX an effective tool for maintaining high standards in adhesive product quality control.