| Historic relics, as an important tourism and cultural resources, is carrier for human obtaining the knowledge and information of itself. China has a long and rich history in all aspects of heritage resources. However, the rapid development of China’s industry has caused the environmental pollutants in water, air, and soil, which can corrode and damage the relics. Though the existing protective materials are numerous, most existing materials still cannot be satisfactory for relics conservation, and many relics are disappearing without proper protection gradually. It is necessary to develop novel functional materials with excellent protective properties in repairing of relics.Polyurethanes (PU) synthesized by traditional methods are usually dispersed in organic solvents, but environmental regulations are increasingly restricting their production and use. Waterborne polyurethanes (WPU) are attracting significant attention owing to their exceptional properties, such as excellent wear resistance, low temperature resistant, strong adhesion, environmentally friendly, easy to storage and use, etc. Ultraviolet (UV) light curing technology, as one of the most environmentally friendly curing technology, have shown remarkable potential for the applications of PU materials due to environmentally friendly, effective and fast curing rates.In this thesis, we will integrate the WPU synthesis technology and UV light-curing technology to prepare the series of UV-curable waterborne polyurethane-acrylate materials for applications in the conservation of iron, copper, stone and brick relics. The main research work and contents are listed as follows:1. Preparation, characterization of UV-WPUA and their application in surface conservation of iron relics.Hydroxyethyl methyl acrylate (HEMA) capped waterborne polyurethane-acrylate (WPUA) oligomers with different R values were firstly prepared from isophorone diisocyanate (IPDI), polyether polyol (NJ-220), dimethylolbutanoic acid (DMBA), HEMA via in-situ and anionic self-emulsifying method. A series of UV curable WPUA (UV-WPUA) coatings were obtained by varying the HEMA-capped oligomer, butyl acrylate (BA) and multifunctional acrylates (TPGDA), and Darocur 1173 was used as photoinitiator. The physical and chemical properties of WPUA oligomers and UV-WPUA coatings such as particle size, apparent viscosity, and surface tension were investigated. The as-prepared UV-WPUA coatings were further applied for metal iron surface conservation. The results confirmed that the surface tension and particle size of the prepolymer were decreased with increased R values, and the best properties of prepolymer was obtained at R value of 2. With increasing the ratio of BA and TPGDA monomer, the hardness and tensile strength of UV-WPUA coatings were decreased, while the contact angles, surface free energy and elongation rates were increased. These coatings show the best properties at BA/TPGDA molar ratio of 5:5. Overall, these results suggest that the as-prepared UV-WPUA coatings are potentially useful in surface conservation of iron relics.2. Preparation, characterization of UV-curable waterborne PUA and their application in surface conservation of copper relics.The PUA oligomers with different R values were firstly prepared with N220, IPDI, DMBA and HEMA. Then, the UV-curable waterborne PUA emulsions were obtained by mixing the PUA oligomers, photoinitiator 1173 and reactive diluents (BA and TPGDA) with the mass ratios of 67: 3:30. Finally, a series of UV-curable waterborne PUA coatings were obtained by varying the mass ratio of BA and TPGDA under UV irradiation, and further applied for metal copper surface conservation. The properties and surface morphology of the PUA oligomers and coatings were characterized. The results indicated that the PUA oligomers display good stability and appropriate solids content, particle size and surface tension. The best performance of PUA coatings was obtained at the BA/TPGDA mass ratio of 1:1, at which the contact angle was 64.74° and water absorption rate is 4.08%. The as-prepared UV-curable waterborne PUA coatings can be used to cover the surface copper sheet and prevent the oxidation of copper surface, which have potential applications in surface conservation of copper relics.3. Effects of the ratio of prepolymers on the synthesis UV-Polymer and their application in surface conservation of stone relics.Considering the component of stone relics, the prepolymers of UV-Polymer were synthesized by IPDI. NJ-220, DMBA and HEMA at appropriate ratios. The physical and chemical properties of as-synthesized prepolymers was characterized. Fixing the BA/TPGDA mass ratio of 1:1, a series of UV-Polymer coatings were obtained by varying the mass ratio of prepolymers and reactive diluents under UV irradiation. The as-prepared UV-Polymer coatings were further applied for stone surface conservation. The results indicated that the prepolymers of UV-Polymer have good thermal stability, freeze-thaw stability, dispersion and appropriate viscosity, particle size and surface tension. The as-prepared prepolymers can be stored more than six months at room temperature. With increasing the content of prepolymers, the hardness and tensile strength of UV-Polymer coatings were decreased, while the elongation, water absorption and swelling properties were increased. The DSC curves results indicate that the UV-Polymer coatings display excellent thermal stability. When the mass ratio of prepolymer, reactive diluent and a photoinitiator was 67:30:3, the lowest surface energy was obtained to be 54.72 mJ/m2 and the maximum contact angle of UV-Polymer coatings was obtained to be 64.60°. The optimum UV curing time was 30 s, at which smooth and homogeneous surfaces could be obtained, and there are no cracks. The as-prepared UV-Polymer coatings can be used to cover the surface of stone and prevent the stone weathering, which have potential applications in surface conservation of stone relics.4. Effects of the ratio of monomer on the synthesis UV-PU and their application in surface conservation of brick and tile relics.Fixing the prepolymers/reactive monomers/photoinitiator mass ratio of 87:10:3, a series of UV-PU oligomers and corresponded UV-curable coatings with monomer contents of 0% and 10% were synthesized by BA and TPGDA as reactive diluents and 1173 as photoinitiator for applications in the conservation of brick and tile relics. The effects of the ratio of monomer on the water resistance, solvent resistance, mechanical properties and thermal properties were investigated based on the characterization. It is indicated that solvent resistance, mechanical properties and optical properties are improved significantly by increasing the ratio of monomers. The Tg was increased with increasing the contents of monomers, indicating the enhancement of the thermal stability of UV-curable coatings. The contact angle of UV-PU coatings were decreased, while the surface energy were slightly increased as the UV curing time increased from 20 s to 40 s. The lowest surface energy was obtained to be 45.43 mJ/m2 and the maximum contact angle of UV-PU coatings was obtained to be 81.44° at UV curing time of 30 s. The SEM results indicates the smooth and flat of the UV-PU coatings without phase separation and crack. The as-prepared UV-PU coatings can be used to cover the surface brick and tile and prevent the corrosion of brick and tile relics surface, which have potential applications in surface conservation of brick and tile relics.5. Preparation and properties of CaCO3 modified urethane-acrylate coatingsNano CaCO3 (MNCA) was modified by γ-MPS (KH-570) and Tween 80 to generate the activated surfaces. The prepolymers of PU were firstly synthesized by IPDI, NJ-330, DMBA and HEMA. Then, UV-curable nano CaCO3/waterborne polyurethane (UV-MNCA/WPUA) coatings were fabricated through photoreaction of prepolymers, MNCA and photoinitiator for applications in the conservation of iron relics. The properties of as-fabricated coatings were analyzed based on the R values and the ratio of WPUA:BA:photoinitiator. Effects of the content of MNCA on the physical properties, surface morphology, thermal stability and mechanical properties of UV-MNCA/WPUA coatings were investigated in detail. The results show surface modification can prevent MNCA-1 particle agglomeration. The surface modified MNCA with diameters of about 54.4 nm can be reacted WPUA. The best mechanical properties of UV-MNCA/WPUA coatings was obtained with WPUA/BA/photoinitiator mass ratio of 66:30:4, and the maximum tensile Strength of UV-MNCA/WPUA coatings was obtained to be 9.0 MPa at the MNCA content of 3.6%. The as-prepared UV-MNCA/WPUA coatings can be used to cover the surface iron and prevent the corrosion of iron relics surface without change the appearance, transparency and gloss of relics, which have potential applications in surface conservation of brick and tile relics.6. Preparation and properties of organic fluorine modified urethane-acrylate coatingsFour series of UV-curable organic fluorine modified aqueous urethane-acrylate (UV-WFPUA) coatings were synthesized by waterborne polyurethane prepolymer (R=2), hexafluoroisopropyl methacrylate, butyl (HFMA), TPGDA, photoinitiator 1173,184,651. Effects of the content of HFMA and TPGDA, the mass ratios of TPGDA and BA, and photoinitiator on the properties of as-synthesized coatings were investigated based on various modern instrumental analysis techniques and characterization methods. The as-prepared UV-WPUA coatings were further applied for metal iron surface conservation. The results confirmed that the hardness, tensile strength, water resistance, mechanical properties of UV-WFPUA coatings were enhanced by increasing the content of HFMA, while the hardness, the gel content, water resistance and solvent resistance of UV-WFPUA coatings were increased by increasing the content of TPGDA. With increasing the mass ratios of TPGD A and BA, the hardness, gel content, tensile strength, contact angle, toughness and elongation of UV-WFPUA coatings were enhanced by the partial substitution of BA with TPGD A. The best properties of UV-WFPUA coatings was obtained by using the photoinitiator of 1173, mainly due to the low sensitivity of inhibitor.7. Preparation, properties and kinetics of urethane-acrylate coatingsA series of UV-WFPUA oligomers and corresponded UV-curable coatings were synthesized by polyether polyol (NJ-210, NJ-220, NJ-330), IPDI, HEMA, DMBA, BA and photoinitiator (1173,184,651). The physical and chemical properties of as-synthesized UV-WPUA coatings were characterized, and the effect of the content of polyether polyol and BA of as-synthesized coatings were investigated. The kinetics of photo-curing process were studied by FT-IR and Photo-DSC. With increasing the content of polyether polyol, the hardness, water absorption, swelling ratio, shrinkage and the gel content of UV-WPUA coatings were decreased, while the tensile strength and elongation of UV-WPUA coatings were increased, indicating that the degree of crosslinking and mechanical properties of UV-WPUA coatings were increased with increasing the content of polyether polyol. The hardness and tensile strength of UV-WPUA coatings were decreased with increasing the content of BA. The optimum BA content was 30%, at which excellent wear resistance and acid resistance could be obtained. The properties of UV-WFPUA coatings initiated by 1173 were higher than that of UV-WFPUA initiated by 184 and 651. The maximum conversion rate of double bonds could be reached 87% at BA content of 30% and photoinitiator content of 3%.The kinetics data, obtained from the DSC curves, were analyzed by Kissinger and Crane models. The corresponded kinetic equations were obtained by Photo-DSC system. |
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