UV curable adhesive, as the name suggests, refers to adhesive that solidifies through exposure to ultraviolet light. The UV curing technology used has no VOC volatiles and is considered an environmentally friendly green technology. The principle is that the photoinitiator (or photosensitizer) in UV cured materials absorbs ultraviolet light and produces active free radicals or cations, triggering monomer polymerization, cross-linking, and grafting chemical reactions, causing the adhesive to transform from liquid to solid within seconds.

UV cured adhesive is widely used due to its fast curing, controllable reaction, wide range of adhesive materials, high bonding strength, and high light transmittance after curing

1. Glass industry:Used for bonding between glass, plastic and glass, and metal and glass, such as glass cabinets, electronic scales, glass coffee tables, etc;

2. Electronic industry:Used for bonding and packaging electronic components, such as bonding mobile phone screens and borders, circuit board protection, LED packaging, etc;

3. Jewelry industry:Can be used for setting and positioning gemstones, crystals, etc;

4. Automotive industry:Can be used for bonding automotive imaging equipment, such as fixing the lens of a dash cam to the body. It can also be used for bonding automotive lighting fixtures, such as sealing and bonding the lampshade and lamp body of front headlights;

5. Medical industry:Can be used for bonding disposable medical needles and syringes, assembling medical devices such as catheters, reservoirs, sensors, etc.

The UV curing process of UV cured adhesive is a polymerization reaction of active acrylic groups, and the degree of curing will affect the bonding effect. Therefore, it is very important to test the curing rate of UV cured adhesive. The use of Fourier transform infrared spectrometer can quickly test the changes in the characteristic absorption peaks of active groups before and after the reaction to calculate the degree of curing. The instrument is easy to operate and the test results are fast and reliable. ATR attachment testing is generally used for testing, which requires a small amount of samples and causes minimal damage to the samples.

Test the infrared spectra before and after the UV curing adhesive reaction separately, and calculate the curing rate based on the proportion of specific absorption peaks. The following figure shows that during the UV curing process of a certain brand of adhesive, the characteristic absorption peak of the prepolymer propylene group (absorption at 1407cm-1) changes, while the absorption peak of the filler (absorption at 608cm-1) does not change significantly. Therefore, based on the absorption peak of the filler (absorption at 608cm-1), the photocuring rate of the prepolymer propylene group can be calculated according to the changes in its characteristic absorption peak (absorption at 1407cm-1).

UV cured adhesive spectra before and after light curing

Calculate peak position

calculation formula

Pre polymer propylene based curing: C0=A0/B0

Pre polymer propylene based cured: C1=A1/B1

Curing rate=(1-C1/C0) * 100%

It is recommended to test multiple times at different locations of the same sample to determine the consistency of the curing rate at different points.

Summary:

benefitThe use of Fourier transform infrared spectrometer combined with ATR attachment to test the curing rate of UV cured adhesive is a simple, fast, efficient, and reliable method. It requires a small sample size, has low destructiveness, and is easy to operate, making it suitable for rapid batch testing. Welcome to follow IR Infrared Cloud Academy and learn infrared knowledge together.