Abstract
An UPLC-Q-TOF-MS method is developed for cure degree measurement and cure behavior analysis on a novel photocurable adhesive material which is composed of specially designed acrylate oligomers, acrylate monomers, photo-initiators and additives such as ultra-violet absorbent, antioxidant stabilizer, optical stabilizer, etc. The photocurable adhesive material, in both cured and uncured state, were separated by Ultra-Performance Liquid Chromatography (UPLC) and the low molecular weight components were detected and determined quantitatively by high resolution Quadrupole Time-Of-Flight mass spectrometry (Q-TOF-MS) under Atmosphere Pressure Chemical Ionization (APCI) mode. Cure behaviors of all photo-reactive components in the photocurable adhesive material such as acrylate monomers and photo-initiators were studied by quantitatively measuring the amount of each reactive components in different stages of curing. Both the conversion of each acrylate monomers and photo-initiators at different curing energy conditions were calculated and discussed. Nearly full cure was obtained at cure energy of 200 mJ/cm2 for 4-hydroxybutyl acrylate and acryloyl morphine, as well as the two bifunctional monomers, 1,6-hexandiol diacrylate and dimethylol tricyclodecane diacrylate. Only 42.7% and 85.0% conversion were achieved for benzyl acrylate and isobornyl acrylate, respectively while consumption of TPO, a photo-initiator, was 38.0% at this cure energy. The results showed that a minimum 2000 mJ/cm2 energy condition is needed to achieve full cure of all acrylate monomers and enough decomposition of photo-initiator. This study indicated that UPLC-Q-TOF-MS is an effective and precise analytical method for cure degree measurement and cure behavior analysis on the photocurable materials.
Highlights
Photocurable materials have been widely used in various applications as adhesives] [1,2,3], coatings] [4,5,6], photoresists] [7,8,9] and inkjet printings] [10,11,12] because of their handling and fast curability
The photocurable adhesive material was seperated by reverse phase Ultra-Performance Liquid Chromatography (UPLC) under a grandient program in an aqueous and solvent system as described above
The characteristic mass spectrometric peak for each targeted analyte was determined using reference standard as either the molecular ion or the most abundant fragment ion. These ions were extracted from the total ion chromatogram (TIC) to pull out the Extracted Ion Chromatogram (EIC) of each compound for further quantificatioin, as shown in Figure 1 for benzyl acrylate, dimethylol tricyclodecane diacrylate and TPO as example
Summary
Photocurable materials have been widely used in various applications as adhesives] [1,2,3], coatings] [4,5,6], photoresists] [7,8,9] and inkjet printings] [10,11,12] because of their handling and fast curability. Cure degree measurements and cure behavior study on photocurable materials are very important for the determination of suitable cure condition and photocurable material designation as well as failure case root cause study in actual use. Several methods such as FT-IR] [19,20], UV-DSC] [21], adhesion strength testing] [22] have been used for cure degree measurements. The purpose of this study is to investigate and develop a precise analytical method that can be used for cure degree determination on individual reactive components for photocurable materials
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