The right surface can make all the difference. This is especially true when affixing a polymer to another material during manufacturing.
Using corona or plasma treatment modifies the surface of materials such as polymers, metalized surfaces, foils, and paperboard stocks, allowing better adhesion between materials. Determining the ideal settings for the plasma treatment can take some finesse. Too little surface modification and a polymer won’t affix to it. Too much, and the surface burns, ruining the material’s integrity.
It’s a good thing there’s a way to verify that corona treatment achieves the optimal result. Using Electron Spectroscopy for Chemical Analysis (ESCA, also called X-ray Photoelectron Spectroscopy or XPS), we can evaluate the surface composition and chemistry of a material for its ability to bond and its wettability.
The following example illustrates how we characterize the impact of the corona treatment using ESCA.
Corona Treatment to Prepare Surfaces in Polymer Manufacturing
Corona treatment involves creating a plasma between a grounded polymer surface and a high voltage, high-frequency electrode. The frequency is between 25 Hz to 40 kHz, and electrode voltage is about 10 kV.
The plasma can be atmosphere or a mixture of other chemicals, depending on the material and its intended use. The gap between high voltage electrodes and the polymer is usually 2-3 mm. The combination of small gap and large voltage results in a plasma discharge to the material which reduces its surface energy and surface tension.
ESCA to Characterize Corona Treatment
The goal is to find the settings for the corona treatment that deliver the optimal surface for bonding. Materials analysis can provide the answer.
ESCA supplies quantitative and chemical state information about a sample material’s surface, making it an ideal choice for characterizing the corona treatment.
The ESCA technique uses an X-ray beam to irradiate the material’s surface, leading to the release of inner-shell electrons. These photoelectrons have low energy levels — 1500 eV or less — and only travel short distances in a solid. The information stored in the photoelectrons allows us to characterize the surface of a material after corona treatment and determine its bonding potential.
This example characterizes corona treatment of polysulfone. The figures below compare a control sample of polysulfone with one treated with a corona discharge:
This high-resolution scan provides chemical state information of untreated polysulfone.
In the treated product, the oxygen content is nearly two times that found in the untreated polysulfone. Why does this matter? The increased molecular oxygen should promote covalent bonding.
Is ESCA a Fit for Your Materials Analysis Needs?
Characterizing corona treatments is one application for ESCA testing. When surface chemistry or thickness is critical to a product’s function and safety, ESCA is a top choice to identify the organic and inorganic materials on the surface, affecting product performance.
In polymers and plastics manufacturing, ESCA is used to identify thin layers of contaminants or stains present on the surface, helping manufacturers determine the cause of manufacturing issues.
For manufacturers who employ stainless steel or other metals — either as part of the manufactured product or within production equipment — ESCA can certify the oxide-rich passivation layer is adequate for rust prevention.
Do you think ESCA might be a fit for your next project? Contact us to discuss your needs. Since 1990, Innovatech Labs has provided fast and reliable materials testing to manufacturers of plastics, medical devices, electronics, and other products.
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