如何减少 UV 胶水的收缩率？有哪些方法？
Quick answer: In most UV systems, photoinitiators are selected by balancing wavelength fit, through-cure, color control, and line speed. Buyers usually compare a blended package instead of one isolated product.
在紫外线胶粘剂的固化过程中存在一个凝胶化过程。在凝胶化之前，尽管有收缩，但系统仍然是流动的，而在凝胶化之后，分子运动受到阻碍，进一步的固化反应是产生收缩应力的主要原因。因此，收缩应力与整个固化过程中的体积收缩不成比例。相反，它取决于凝胶化后的体积收缩。反应物的官能度越高，凝胶化时官能团的反应程度就越低。因此，官能度高的反应体系在固化后会产生较高的收缩应力。
减少 UV 胶收缩的方法
1.使用低收缩单体和低聚物配制紫外线胶水
In the UV glue formula, the use of low viscosity acrylate oligomer and less dilution monomer is also an effective way to reduce the shrinkage rate. Formulators often compare IBOA 单体 for lower stress with TMPTA 单体 for higher reactivity and crosslink density.
2.紫外线胶水添加聚合物或无机填料
在添加聚合物的方法中，新生成的体系与预先添加的聚合物之间有时会在固化过程中发生相分离，也可以抵消部分体积收缩。但这种相分离的缺点是会降低固化产品的透明度。据报道，在自由基聚合体系中加入聚醋酸乙烯酯、聚乙烯缩醛、聚酯和其他热塑性聚合物可显著减少体积收缩。
3.使用阳离子或混合固化方法
阳离子紫外线胶水使用环氧树脂和乙烯基醚的单体，并以铟盐作为光引发剂。环氧树脂阳离子固化反应的收缩率远低于自由基反应，因此使用阳离子配方可以降低固化收缩率。
混合型紫外线胶水是自由基型和阳离子型的混合体系，通常以丙烯酸酯和环氧化合物的混合形式存在。这种混合紫外线固化体系可以提高光引发时的引发效率，充分发挥两者的优势，减少体积收缩，并在其他性能方面具有良好的协同效应。
此外，根据工艺要求，还可采用紫外线等其他固化方法进行复合，如紫外线与热固化或厌氧固化的复合方法，也可减少固化收缩。
4.添加膨胀单体
从环氧树脂阳离子聚合反应中已经知道，开环聚合反应比加成聚合反应体积收缩率要小。对于单环单体来说，每转换一个范德华距离为共价键距离，就有一个共价距离转换为范德华距离。由此产生的收缩和膨胀可以部分抵消。进一步研究发现，开环聚合反应的体积收缩大小与环的大小有关。随着环的尺寸增大，打开共价键的碳原子和氧原子之间的距离越来越接近范德华距离，体积收缩因此减小。目前，螺环型单体的成本很高，所以实际应用还很少，但它是一种很有前途的消除 UV 胶收缩的方法。
How formulators usually evaluate this photoinitiator topic
When technical buyers or formulators screen photoinitiators, the most useful decision frame is usually cure quality plus application fit: which package cures reliably, keeps appearance acceptable, and still works under the lamp, film thickness, and substrate conditions of the actual process.
- Match the package to the lamp first: mercury lamps, UV LEDs, and visible-light systems can rank the same photoinitiators very differently.
- Check depth cure and surface cure separately: a film that feels dry on top can still be weak underneath.
- Balance yellowing with reactivity: the strongest deep-cure route is not always the best commercial choice if color or migration risk becomes unacceptable.
- Use the final formula as the benchmark: pigment load, monomer package, and film thickness can all change the apparent ranking of the same initiator.
Recommended product references
- CHLUMINIT TPO-L: A strong low-yellowing reference for LED-oriented UV systems.
- CHLUMINIT 819: Useful when a formulation needs stronger absorption and deeper cure support.
- CHLUMICRYL IBOA: A strong low-viscosity monomer reference when hardness and good flow both matter.
- CHLUMICRYL TMPTA: A standard reactive monomer benchmark when stronger crosslink density is required.
FAQ for buyers and formulators
Why are blended photoinitiator packages so common?
Because one product may control yellowing or lamp fit well while another improves cure depth or line-speed performance, so the full package is often stronger than any single grade.
Should incomplete cure always be solved by adding more initiator?
Not automatically. The real limitation may be the lamp, film thickness, pigment shading, or the rest of the reactive system rather than simple under-dosage.