Is The Photoinitiator Tpo Facing A Ban? New Alternatives Have Emerged!

Recently, a notice from the European Chemicals Agency (ECHA) has attracted widespread attention both inside and outside the industry: diphenyl (2,4,6-trimethylbenzoyl) phosphine oxide, also known as the photoinitiator TPO, has been officially included in the 29th batch of highly concerned substances (SVHC) candidate lists, which means that TPO will face a complete ban in the European market.

Figure 1 TPO Chemical Structure

With the ban of TPO, various alternative products have emerged in the market, such as the currently popular TMO, TPO-L, 819, etc. However, these products have always struggled to achieve a balance in terms of market price, triggering efficiency, yellowing resistance, and other performance aspects.

Based on this situation, the Kastar technical team has launched the PI series of photoinitiators after multiple experimental tests. This series of products not only has competitive prices, but also performs well in terms of triggering efficiency, yellowing resistance, and other performance, providing downstream production enterprises with efficient, economical, and environmentally friendly alternatives to photoinitiators.

01. Photoinitiator

Photoinitiators play a crucial role in UV coatings, printing inks, wood coatings, adhesives, and other fields, with various advantages such as fast curing, enhanced adhesion, high efficiency, and no VOC content. Not only can it serve as a medium for energy transfer, but it also directly determines the curing speed, environmental friendliness, and overall performance of the coating.

Figure 2 Characteristics of UV curable coatings

In the photopolymerization system, photoinitiators can activate the polymerization ability of active intermediates, causing oligomers and active diluents to undergo polymerization and cross-linking reactions, thereby achieving rapid transformation of coatings or inks from liquid to solid.

Different photoinitiators are suitable for different systems and requirements, and can endow coatings with different characteristics such as hardness, flexibility, adhesion, gloss, and aging resistance. Therefore, it is crucial to choose the appropriate photoinitiator in the production and application of UV coatings.

02. Experimental interpretation

Experimental testing

The colors of the three liquid photoinitiators in the PI series are not significantly different from TPO, and there will be no noticeable difference during use. However, compared to solid photoinitiators, the addition of liquid photoinitiators is more convenient and simple, greatly shortening the production cycle and improving the efficiency of the production line.

In the same formula, PI 11, PI 12, and PI 13 are added separately; Test its triggering efficiency, yellowing resistance, and stability.

Figure 3 Color Comparison of Three Photoinitiators and TPO

Data analysis

1. Yellowing resistance performance

The yellowing value is an important indicator for measuring the weather resistance of photoinitiators (PS), and the lower the yellowing value, the better the weather resistance of the photoinitiator.

PI 12 exhibits particularly outstanding resistance to yellowing, even after undergoing a 60 ℃ * 7-day thermal storage test, the yellowing value of PI 12 remains at a low level, demonstrating excellent resistance to yellowing. For those with high requirements for yellowing, PI12 can be the first choice.

Figure 4 Comparison of yellowing data between PI series photoinitiators and TPO

2. Curing efficiency

Before thermal storage, the curing speed of PI series photoinitiators reached around 7 minutes, with PI 11, PI 12, and PI 13 having curing speeds close to excellent levels. After thermal storage, although the curing speed decreased, the curing speed of PI 11 did not change significantly and still showed good stability.

Figure 5 Comparison of Efficiency Data between PI Series Photoinitiators and TPO Fixed Telephone

3. Thermal storage stability

Under the thermal storage conditions of 60 ℃ * 7D, the liquid of PI series photoinitiators showed no precipitation and the color of the body did not change significantly, demonstrating their excellent thermal stability.

Figure 6 Comparison of Color Data between Series Photoinitiators and TPO

The photoinitiators PI 11, PI 12, and PI 13 launched by Kastar not only meet the market's demand for high-performance photoinitiators, but also better align with the current trend of environmentally friendly production.

The PI series photoinitiators have high stability, safety, and compatibility, and can ensure curing efficiency. While bringing substantial value to downstream production enterprises, it also injects new vitality into the development of the entire industry, helping enterprises to pursue economic benefits while taking responsibility for the environment.