Abstract
A kind of hyperbranched silicone containing macrophotoinitiators (HBSMIs) were synthesized from 2-hydroxy-2-methyl-1-phenyl propanone (HMPP) and the UV-curing behaviors of HBSMIs were investigated in UV-cured transparent polyurethane-acrylate (PUA) coatings. HBSMIs show higher UV-initiating efficiency than HMPP. The migration of HBSMIs from the UV-cured coatings can be as low as 1.7–6.0 wt%, which is obviously lower than the migration of HMPP. There is a remarkable improvement of the tensile strength of the UV-cured materials initiated by HBSMI in comparison to that of the materials prepared with the same PUA initiated by HMPP. Especially for the UV-cured materials prepared from PUA with 20 wt% 1,1,1-tris(hydroxymethyl)propane (TMP), the tensile strength and the strain at break increased from 6.81 MPa to 12.14 MPa and from 43.0% to 71.9%, respectively. The fraction of improvement for the tensile strength and the strain at break is as high as 78.9% and 67.2%, respectively. The coatings prepared with HBSMI also have better UV resistance ability than those coatings prepared with HMPP because they turn slightly yellow when they are aged by UV for about 15 min while the coating prepared with 4 wt% of HMPP will turn yellow only aged by UV for 2 min. These results suggest that preparation hyperbranched silicone containing macrophotoinitiators will be one of the good strategies to improve the curing efficiency of the UV-curing system, reduce the migration of UV initiator from cured material, improve the mechanical and UV resistance performance of UV-cured materials.
Highlights
UV-curing technology has drawn more and more attention in many fields such as coatings [1,2,3,4,5], 3D printing [6,7], biomaterials [8] because of its environmentally friendly and high efficiency advantages.A conventional UV-curing system usually is a composition of UV-curable polymers, reactive monomers, additives, and a photoinitiator or photoinitiator system [9]
hyperbranched silicone containing macrophotoinitiators (HBSMIs) for the same time are higher than those coatings cured by hydroxy-2-methyl-1-phenyl propanone (HMPP) respectively
Therefor is the UV-cured materials prepared from PUA with 20 wt% TMP, the tensile strength and the strain at a remarkable improvement of the tensile strength of the UV-cured materials initiated by HBSMI in comparison to that of the coatings prepared with the same PUA initiated by HMPP
Summary
UV-curing technology has drawn more and more attention in many fields such as coatings [1,2,3,4,5], 3D printing [6,7], biomaterials [8] because of its environmentally friendly and high efficiency advantages. A novel hydrosoluble photocleavage polysiloxane photoinitiator based on HMPP and aminopolysiloxane for preparing a gradient polymer shows relatively good solubility in water and excellent photoinitiating efficiency [23] and a photocleavage polymerizable organosilicon macromolecular photoinitiator based on HMPP exhibits the migration of photolysis fragments toward the cured material surface was mitigated significantly [24]. A kind of water-borne polysiloxane-modified photoinitiator based on HMPP can mitigate the oxygen inhibition and the cured materials have better mechanical properties and thermostability compared with that by HMPP [25] These good works promote the research and application of HMPP-based silicone macrophotoinitiators. These silicone macromolecular photoinitiators usually have poor compatibility with the UV-curable polymers, which will result in a lower transparency and relative poor mechanical of UV-cured products [4].
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