Synthesis And UV Curing Properties Of Urethane Acrylates

Urethane Acrylates(UA)is considered as one of the most widely used UV curable resin which is commonly produced by the reaction of polyisocyanates,polyols and hydroxyl functionalized acrylates.Due to the toxicity of isocyanates and phosgene that is used to synthesize isocyanates,the traditional route could not satisfy the requirements of “Green Chemistry”.Environmental friendly route of non-isocyanates procedure for preparation of UA has gradually attracted more and more attentions.In this paper,the research progress of urethane acrylate in recent years was reviewed.Based on those studies,a new synthesis method of non-isocyanate urethane acrylatewas developed.In this paper,two kind of carbamate diol monomers were prepared by reaction of 1,6-hexanediamine and isophoronediamine with ethylene carbonate respectively,which were used to reacted with dimethyl malonate to obtain another four kinds of malonate ester modified carbamate mixed monomers.Fourteen different urethane acrylate mixtures were synthesized by the reaction of those carbamate monomers with 1,6-hexanediol diacrylate(HDDA),neopentyl glycol diacrylate(NPGDA)and trimethylolpropane triacrylate(TMPTA),respectively,through Michael addition and transesterification.Using the reaction of HDDA with carbamate diol(BHCH)as the model reaction,the optimum molar ratio of acrylate to carbamate monomer was investigated.NMR was used to confirm the structure of carbamate monomers.The structure of carbamate monomers were confirmed by NMR and FT-IR.The main components of synthetic urethane acrylate resins was characterized by high resolution mass spectrometry.The UV curing kinetics of the urethane acrylates was studied by FT-IR.The properties of UV cured film were evaluated.The curing kinetics,double bond conversion rate and basic properties of the UV cured film obtained by carbamate diol or malonate ester carbamate mixed monomers were compared.Effects of components such as mixed carbamate monomer of carbamate diol and malonate ester carbamate on the properties of the resin and its curing film were analyzed.The results showed that the best molar ratio of acrylate to carbamate monomers was 2.2:1 for higher conversion of carbamate monomers diol and better property of resin.The obtained urethane acrylate resin could be UV cured within 30 s under promotion of 3 wt%(total mass fraction)of photoinitiator 1173 under UV light,forming a smooth,transparent or translucent film with good flexibility(0.5～2.5 mm).The gelation rate of the film was 90～97%and the pencil hardness of the film was 4～5 H.The adhesion of film to the glass is level of 0～1.Resins synthesized by malonate ester carbamate mixed monomers containing more reaction sites reacting with acrylate have higher efficiency of double bond convension.The flexibility of curing film is maintained at 0.5～1.0 mm,and the pencil hardness increased from 5 H to 6 H.The result also presents that using mixed carbamate monomers of carbamate diol and malonate ester carbamate have little influence on the curing dynamics and the conversion of double bond as well as the flexibility of curing film(0.5～1.0 mm)and pencil hardness(4～6 H).However,the gelation rate fells slightly(90%～93%).