Synthesis Of UV Curable Hyperbranched Polymers, And Preparation And Properties Of Their Silica Hybrid Coatings

Hyperbranched polymers are a kind of highly branched/dendritic macromolecules withthree-dimensional architecture. Hyperbranched polymers have many attractive features, suchas low viscosity, high solubility and good compatibility. Because of their large number ofsurface functional group, they are also facile for chemical modification. Due to theseadvantages, hyperbranched polymers have attractive application in UV curing fields, but itsstill at the starting stage of the research of UV curable hyperbranched polymer. On the basisof the previous works, different terminal acrylation of hyperbranched polymer weresynthesized by modifying the ending hydroxyl of hyperbranched polyester (Boltorn H20),and applied in UV curing systems. Their sturctures and properties were also comprehensivelystudied. Furthermore, a series of UV curable hyperbranched polymers/SiO₂hybrid coatingswith excellent performance were syntheiszed by adding modified silicane sol into UV curablehyperbranched polymers. The main research contents and achievements are listed asfollowing:Firstly, two kinds of UV curable hyperbranched urethane acrylates (HBUCA andHBUPA) were synthesized by by modifying hydroxyl-terminated of hyperbranched polyester(Boltorn H20), with semiadduct urethane monoacrylate prepared from polycaprolactonemodified hydroxyethyl acrylate (PCLA2), polyethylene glycol monoacrylate (PEA6) andisophorone diisocyanate (IPDI). The structure and properties of HBUCA and HBUPA werecharacterized by FT-IR,¹H-NMR, GPC, DSC, DMA, TG and rheometer before and after UVcuring. The effect of ending structure and degree of acrylation on molecular weight andpolydispersity, viscosity and T_gof hyperbranched urethane acrylates were stuedied. UVcuring reaction kinetics of hyperbranched urethane acrylates and properties of their UV curedfilms were also studied. The results showed that the rules of increasing of degree of acrylationon properties of HBUCA and HBUPA are similarly. The polydispersity indexes and viscosityof HBUCA and HBUPA oligomers increased gradually, and T_gdecreased with the increasingof degree of acrylation. HBUCA and HBUPA exhibited the characteristics of non-Newtonianbehaviour. Their viscosities were dependent of frequency, which indicates the existence of chain entanglements. The R_P^maxof HBUCA and HBUPA oligomers increased with theincreasing of degree of acrylation and HBUCA oligomers possessed higher R_P^maxand R^fthanHBUPA. The thermal decomposition of HBUCA and HBUPA films included two stages, andtheir thermal stability were better than that of line polymers. The E' and T_gof UV curedHBUCA and HBUPA films increased gradually, while tan δmaxand Ts/T_gdecreased with theincreasing of degree of acrylation. Mechanical properties of HBUCA and HBUPA, includingpencil hardness, pendulum hardness, adhesion, flexibility, impact strength increase first anddecrease afterwards with the increasing of degree of acrylation. HBUCA-80and HBUPA-80had optimal mechanical and corrosion resistance properties.Secondly, a kind of UV curable hyperbranched polyester acrylates (HBIPA) weresynthesized by modifying hydroxyl-terminated of Boltorn H20with isononanoic acid,phthalic anhydride (PA) and glycidyl methacrylate (GMA) through stepwise reaction. Thestructure and properties of HBIPA were characterized by FT-IR,1H-NMR,GPC,Rheometer,DSC,DMA and TG before and after UV curing. The effect of ending structure and degree ofacrylation on molecular weight and polydispersity, viscosity and T_gof hyperbranchedurethane acrylates were stuedied. UV curing reaction kinetics of hyperbranched urethaneacrylates and properties of their UV cured films were also studied. The results showed that thepolydispersity indexes, viscosity and T_gof HBIPA oligomers increased gradually with theincreasing of degree of acrylation. HBIPA exhibited the characteristics of Newtonianbehaviour. Their viscosities were independent of frequency, which indicates a lack of chainentanglements. When the degree of acrylation increase from25%to50%, R^fof HBIPAincrease from79.8%to85.9%, R_P^maxincrease from0.0155s-1to0.0202s-1. The thermaldecomposition of HBIPA included two stages, and their thermal stability increased with theincreasing of of degree of acrylation. The E', T_gand Ts/T_gof UV cured HBIPA filmsincreased gradually, while tan δmaxdecreased with the increasing of degree of acrylation,indicating the increase of hardness and homogeneous. Furthermore, mechanical properties ofHBIPA films including pencil hardness, pendulum hardness, adhesion, fimpact strengthincreasing with the increasing of degree of acrylation, and HBIPA-50had optimal mechanicaland corrosion resistance properties. Thirdly, UV curable MPTMS/SiO₂sols were prepared by acid catalytic sol-gel processfrom tetraethylorthosilicate (TEOS) and methacrylate propyl trimethoxysilicate (MPTMS).The stability of sols were studied. The structure and properties of MPTMS/SiO₂sols werecharacterized by FT-IR,DLS and TG-DTA before and after UV curing. The conversion ofC=C bond and the polycondensation degree of silicone were determined, and the properties ofMPTMS/SiO₂hybrid films were also studied. The results showed that the gelation timeexceeded180days and particle diameter were30nm when the mole ratio of components werenMPTMS/nTEOS=1/2¹/1,nH2O/nSi-O=0.75¹,nEtOH/nSi-O=1¹.25,nHCl/nSi-O=0.006. The curedfilm had high hardness and good flexibility because linear Si-O-Si segmers were introducedinto high-density crosslinked SiO₂network. The conversion of double bonds of MPTMS/SiO₂sols was difficult to reach completely. The use of MPTMS can enhanced the thermal stabilityand mechanical properties of MPTMS/SiO₂cured films.Finally, different UV curable hyperbranched polymer (HBUCA,HBUPA and HBIPA)were used as organic components, and MPTMS/SiO₂sols were used as inorganic componentsfor preparing a series of UV curable hyperbranched polymer/SiO₂hybrid coatings. Thestructures and properties of cured fims of hybrid coatings were characterized by FT-IR,SEM,DMA and TG. The effects of the ingredient on structure, interfacial compatibility andproperties of hybrid films were studied. The results showed that UV curable hyperbranchedpolymer/SiO₂hybrid coatings had good storage stability. When the mole ratio of TEOS andMPTMS was1:1, the viscosity of UV curable hyperbranched polymer/SiO₂hybrid coatingshave no change after90days. UV curable hyperbranched polymer/SiO₂hybrid coatings hadgood interfacial compatibility and MPTMS/SiO₂were well distributed in organic matrix. Thethermal stability of hybrid coatings were higher than that of pure polymers. E′and T_gincreased with the increasing of MPTMS/SiO₂. UV curable hyperbranched polymer/SiO₂hybrid coatings have good felxibility, high hardness and excellent abrasion resistance.