Silicone Detection in Manufacturing

Silicone-based materials are used in many industrial applications and products.

As an example, thin coatings of silicone are used as release agents in the manufacturing of molded parts. Silicones are frequently applied to surfaces such as labels and fixtures. They are used to waterproof fabric and paper. In their bulk form, silicones are used to make pliable seals, adhesives, and molded products.

Given their range of uses, manufacturers must have the ability to analyze silicones in order to detect contamination or confirm proper application.

Silicone contamination and unwanted residue can damage products. Small traces of silicone on a painted surface will affect the adhesion properties and ruin the finish. Further, silicone contaminants can cause mechanical failure in applications where two surfaces are meant to be bonded together. When used in sealing applications, silicone adhesives and elastomers must be applied uniformly to ensure proper function.

Detection and measurement of silicone is essential to ensure quality control in manufacturing processes.

LaserScan Technology

Block has recently developed a next-generation beta version of its surface detection system LaserScan™.

Block's original LaserScan was the winner of the Prism Award for Photonics Innovation, and this new innovation improves on the original's sensitivity of detection.

LaserScan provides rapid, non-contact imaging of silicones and other chemicals in a compact form factor. The LaserScan uses Block Engineering's proprietary Quantum Cascade Laser (QCL) technology to achieve a high quality mid-infrared spectroscopic image, enabling the user to detect and analyze the presence of silicone.

Detection levels of contaminants on rough surfaces can reach fractions of a microgram per cm2. Users can characterize silicone film thicknesses for quality control measures and analyses are accomplished within a few seconds without physically contacting the surface.

Because the LaserScan uses a low power, collimated QCL beam, it can safely measure contaminants on surfaces from distances ranging from six inches to several feet away depending on the application.

Detection Technology

Silicone, like almost all chemicals, has a unique absorption signature in the mid-infrared spectrum. When mid-IR light reflects from a surface, the reflection spectrum carries this chemical-specific information and enables the identification of the chemical composition. Because these absorption features are often very strong, detection of trace levels of contamination is possible.

Based on the recorded spectral data, Block's proprietary algorithms can provide real-time detection results in seconds.

Direct Analysis of Surfaces

In practical use, silicone can be detected on a wide variety of surfaces — including aluminum and steel plates, plastics, rubber, and painted surfaces.

In the spectrum below, the limit of detection of silicone on a metal surface was estimated to be more sensitive than 10 µg/cm2.

LaserScan QCL reflection spectra of ~10 µg/cm2 of silicone lubricant measured at one spot on a contaminated steel plate surface. The characteristic silicone peaks are indicated by asterisks (*).

Silicone on Plastic

The figure below shows calculations of specular reflectance spectra for silicone on plastic.

The simulations indicate that the characteristic silicone peaks will be produced at concentrations as low as 1 µg/cm2. This lower level of detection (compared to metal) is expected due to the differing dielectric properties of the metal and non-metal substrates.

Furthermore, these calculations demonstrate that the LaserScan data has a sound theoretical basis, which provides confidence for industrial users looking for new technologies to tackle increasingly difficult detection applications.

Simulations of reflection spectra of silicone on plastic. These calculations suggest silicone can be measured on such non-metal surfaces at concentrations down to 1 µg/cm2.

Mapping Silicone Deposits

A valuable feature of the next-generation LaserScan is the ability to provide a distinct image of a surface to map silicone deposits.

The figure below shows an image of a fingerprint on roughened aluminum, left from a finger that touched silicone oil.

This imaging capability enables the user to more rapidly and completely scan a surface to map the presence of silicone. Accordingly, it is faster and more effective than swab techniques, which may identify the presence of silicone in the swabbed area but cannot map exactly where it is.

Please contact us to discuss how LaserScan can help to detect and analyze silicone in your applications.