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İSTANBUL TECHNICAL UNIVERSITY INSTITUTE OF SCIENCE AND TECHNOLOGY SYNTHESIS OF MODIFIED EPOXY ACRYLATE RESIN M.Sc.Thesis by Ömer Faruk VURUR Department: Polymer Science and Technology Programme: Polymer Science and Technology JANUARY 2011 İSTANBUL TECHNICAL UNIVERSITY INSTITUTE OF SCIENCE AND TECHNOLOGY SYNTHESIS OF MODIFIED EPOXY ACRYLATE RESIN M.Sc. Thesis by Ömer Faruk VURUR ( ) Date of submission : 20 December 2010 Date of defence examination: 26 January 2011 Supervisor (Chairman) : Prof. Dr. İ. Ersin SERHATLI (ITU) Members of the Examining Committee : Prof. Dr. Ahmet AKAR (ITU) Prof. Dr. Atilla GÜNGÖR (MU) JANUARY 2011 İSTANBUL TEKNİK ÜNİVERSİTESİ FEN BİLİMLERİ ENSTİTÜSÜ MODİFİYELİ EPOKSİ AKRİLAT SENTEZİ YÜKSEK LİSANS TEZİ Ömer Faruk VURUR ( ) Tezin Enstitüye Verildiği Tarih : 20 Aralık 2010 Tezin Savunulduğu Tarih : 26 Ocak 2011 Tez Danışmanı : Prof. Dr. İ. Ersin SERHATLI (İTÜ) Diğer Jüri Üyeleri : Prof. Dr. Ahmet AKAR (İTÜ) Prof. Dr. Atilla GÜNGÖR (MÜ) OCAK 2011 FOREWORD This study has been carried out in POLMAG Laboratory (Polymeric Materials Research Group), Faculty of Science and Letters, Istanbul Technical University. First of all, I would like to thank to my advisor, Prof. Dr. İ. Ersin SERHATLI, for sharing his knowledge and experience with me generously, for his guidance, and motivation throughout this study. I also would like to thank to Prof. Dr. H. Ayşen ÖNEN for her guidance and invaluable technical support, Prof. Dr. Atilla GÜNGÖR for his invaluable technical support, and Assoc. Prof. Dr. Mehmet Vezir KAHRAMAN for his technical support. In addition, I am thankful to all my colleagues in this research especially to Sümeyye DEMİRHAN, Betül TÜREL, Tuba Çakır ÇANAK, Bahadır GÜLER and Miray GÖKTAŞ for their assistance, encouragement and friendship. Finally, I would like to offer the most gratitude to my parents and my sister; Hatice and Mehmet VURUR and Müşerref VURUR for their great love, patience, moral support and encouragement during all stages of my life. December, 2010 Ömer Faruk VURUR Polymer Science & Technology Department v vi TABLE OF CONTENTS TABLE OF CONTENTS... vii ABBREVIATIONS... xi LIST OF TABLES... xiii LIST OF FIGURES... xv SUMMARY... xvii ÖZET... xix 1. INTRODUCTION THEORETICAL PART Epoxy Resins Introduction The Chemistry of The Epoxy Group The Synthesis of Epoxy Resins Direct Methods Indirect Methods Oxidation of Unsaturated Compounds Types of Application for Epoxy Resins Curing at Room Temperature Curing at Elevated Temperature Radiation Curing Epoxy Acrylate Hybrid Materials Urethane Acrylates Types of Urethane Acrylates Polyether Urethane Acrylates Multicomponent Urethane Acrylates Polyester Urethane Acrylates Polyol Urethane Acrylates UV Coatings Inroduction to Coatings Technology UV Technology and Applications Advantages and Drawbacks of UV Coatings The UV Curing Process The Photochemical Process Photoinduced Curing Chemistry EXPERIMENTAL PART Materials Equipments Infrared analysis (IR) Nuclear magnetic resonance (NMR) UV Spectroscopy analysis (UV) Thermogravimetric analysis (TGA) Page vii 3.2.5 Contact angle meter Gloss meter Pendulum hardness tester Tensile loading machine Synthesis Synthesis of Terephthalic acid modified Epoxy Acrylate Synthesis of Urethane Acrylate Preparation of Film Formulations Preparation of test samples Analyses Infrared analysis (IR) Nuclear magnetic resonance analysis (NMR) Thermogravimetric analysis Gel content measurement Solvent resistance Contact angle measurement Gloss test Pendulum hardness test Pencil hardness test Tensile test RESULTS AND DISCUSSION Synthesis of Terephthalic acid Modified Epoxy Acrylate Synthesis of Urethane Acrylate Film Formation Thermogravimetric analysis Gel content measurement Solvent resistance test Contact angle measurement Gloss test Pendulum hardness tests Pencil hardness Tensile test CONCLUSIONS REFERENCES CURRICULUM VITAE viii ABBREVIATIONS T Si-T UA-T UA VTS IPDI HEMA UV NMR TGA FT-IR DPGDA DBTL HDDA : Terephthalic acid modified epoxy acrylate : Terephthalic acid modified epoxy acrylate with VTS : Terephthalic acid modified epoxy acrylate with urethane acrylate : Urethane acrylate : Vinyl trimethoxysilane : Isophorone diisocyanate : 2-Hydroxy ethyl methacrylate : Ultra Violet : Nuclear Magnetic Resonance : Thermal Gravimetrical Analysis : Fourier Transform Infrared : Dipropyleneglycoldiacrylate : Dibutyl Tinlaurate : 1,6-hexanedioldiacrylate ix x LIST OF TABLES Table 2.1: General composition and function of an UV lacquer Table 3.1: The compositions of synthesized resins Table 3.2: UV curing formulations Table 3.3: UV curing formulations with VTS Table 3.4: UV curing formulations with UA Table 4.1: TGA analysis values of epoxy acrylate films Table 4.2: TGA analysis values of epoxy acrylate films with VTS Table 4.3: TGA analysis values of epoxy acrylate films with UA Table 4.4: Gel content of cured films Table 4.5: Solvent resistance of T Table 4.6: Solvent resistance of T Table 4.7: Solvent resistance of T Table 4.8: Solvent resistance of T Table 4.9: Solvent resistance of Si-T Table 4.10: Solvent resistance of Si-T Table 4.11: Solvent resistance of Si-T Table 4.12: Solvent resistance of Si-T Table 4.13: Solvent resistance of UA-T Table 4.14: Solvent resistance of UA-T Table 4.15: Solvent resistance of UA-T Table 4.16: Solvent resistance of UA-T Table 4.17: Contact angle results Table 4.18: Gloss test values of coated films Table 4.19: Pendulum hardness results (oscillation) Table 4.20: Pencil hardness results Table 4.21: Stress-Strain Analysis of Epoxy Acrylates Table 4.22: Stress-Strain Analysis of Epoxy Acrylates with VTS Table 4.23: Stress-Strain Analysis of Epoxy Acrylates with UA Page xi xii LIST OF FIGURES Figure 2.1 : Reaction of bisphenol A and epichlorohydrins... 4 Figure 2.2 : Ethylene chlorohydrins reaction... 8 Figure 2.3 : Method for synthesis of epoxy rings... 8 Figure 2.4 : Oxidation reaction with peracid... 9 Figure 2.5 : Ring opening of epoxy Figure 2.6 : Ring opening of epoxy Figure 2.7 : The synthesis of epoxy via hydrogen peroxide Figure 2.8 : The epoxidation with hypohalogenous acid Figure 2.9 : The synthesis of low molecular,liquid bisphenol A diglycidylether.. 13 Figure 2.10 : The general formula of bisphenol A diglycidylether Figure 2.11 : The epoxy synthesis with glycidylation Figure 2.12 : The glycidylation reactions of H-active compounds Figure 2.13 : Addition of Hydrogen to Epoxy Groups Figure 2.14 : The epoxide compounds structures Figure 2.15 : Synthesis of bisphenol F Figure 2.16 : Novolac resin Figure 2.17 : Epoxy-novolac Figure 2.18 : Epoxy reactions Figure 2.19 : Epoxy acrylate Figure 2.20 : Selection of representative organofunctional silanes available for the preparation of inorganic organic hybrid materials...35 Figure 2.21 : Isocyanate-Hyrdoxyl Acrylate Reaction.36 Figure 2.22 : Formation of a Polyether Urethane Acrylate Figure 2.23 : Polyester Structure for Acrylation Figure 2.24 : Structures of some non-polyether, non-polyester polyols Figure 2.25 : Electromagnetic energy spectrum Figure 2.26 : Energies as a function of wavelenght in comparison to bond energies...41 Figure 2.27 : Scheme of the UV curing process and UV induced cross-linking Figure 2.28 : Interaction of UV process design parameters Figure 2.29 : Possibilities of photoinduced curing Figure 2.30 : Jablonsky-type diagram for photoinduced radical photoinitiation Figure 2.31 : Photoinitiator types Figure 2.32 : Propagation and transfer Figure 2.33 : Termination reaction Figure 3.1 : Bisphenol A diglycidyl ether resin Figure 3.2 : Hydroquinone Figure 3.3 : Acrylic acid Figure 3.4 : Terephthalic acid Figure 3.5 : Vinyltrimethoxysilane Figure 3.6 : Urethane Acrylate Page xiii Figure 3.7 : Dipropylene glycol diacrylate Figure 3.8 : HDDA Figure 3.9 : Irgacure Figure 3.10 : Scheme of a sessile-drop contact angle system Figure 3.11 : Scheme of a measurement device for gloss at different angles Figure 3.12 : Pencil hardness and properties Figure 4.1 : Synthesis of terephthalic acid modified epoxy Figure 4.2 : IR spectrum of polikem epoxy resin Figure 4.3 : IR spectrum of terephthalic acid modified epoxy Figure 4.4 : Synthesis of terephthalic acid modified epoxy acrylate Figure 4.5 : IR spectrum of terephthalic acid modified epoxy acrylate Figure 4.6 : Synthesis of Urethane Acrylate Figure 4.7 : IR spectrum of urethane acrylate Figure 4.8 : TGA thermogram of epoxy acrylate films Figure 4.9 : TGA thermogram of epoxy acrylate films with VTS Figure 4.10 : TGA thermogram of epoxy acrylate films with UA xiv SYNTHESIS OF MODIFIED EPOXY ACRYLATES SUMMARY In recent years, UV curable coating techniques have attracted great attention due to its advantages over thermal curing techniques. The UV curing system is a high-speed process where UV light induces the polymeric film formation leading to a fast transformation of the wet film into the solid film. UV-curing formulations provide some benefits such as fast cure response,excellent chemical resistance, good weathering characteristics, and broad formulating latitude. In the field of UV curing industries, epoxy and epoxy acrylate derivatives have been widely used as coatings, structural adhesives and advanced composite matrices. Epoxy resins are a major class of commercial resins and they are characterized by the possession of more than one 1,2-epoxy groups per molecule, which are the active centers of the resin. What distinguishes epoxy resins from the other polymers is their excellent chemical and solvent resistance, good thermal and adhesion properties, versatility in cross-linking. Besides organic inorganic hybrid materials have gained considerable attention recently because of its superior mechanical properties, thermal stability, and optical properties. Of particular interest is the acrylic silica hybrid which has found great use in the optical membrane application. While acrylics provide easy processibility and optical transparency, silica particles provide hardness and scratch resistance. However, the incompatibility between the acrylics and the silica causes poor dispersion of silica particles in the acrylics matrix and makes a direct blending of acrylics and silica particles impossible. Therefore, significant efforts have been devoted to forming chemical bonding between the acrylics and silica particles. Because the sol-gel processes, which involve an in situ formation of bonded silica particles via the reaction of tetraethylorthosilane with preformed acrylic polymers containing alkoxysilane functional groups, often require a significant amount of effort to eliminate the byproducts (water or alcohol) and a prolonged time to reach the desired extent of reaction, attempts on using acrylic monomers with preformed silica particles which have been functionalized with compatible and copolymerizable organic species have been made. In this study, diglycidyl ether of bisphenol A (DGEBA) epoxy resin was reacted with various amounts of terephthalic acid and acrylic acid. The formed resin was used for preparing three different formulations, coated and cured by UV light. The characterizations of coatings were performed by spectroscopic tools and the thermal and mechanical properties of the formulations were investigated. xv xvi MODİFİYELİ EPOKSİ AKRİLAT SENTEZİ ÖZET Son yıllarda UV kürlenebilir kaplama teknikleri avantajlarından dolayı termal kürlenebilir tekniklerine göre daha büyük bir ilgi çekmektedir. UV kürlenebilir sistemi; UV ışının ıslak filmden katı filme hızlı bir dönüşüme yol açan polimerik film oluşumuna neden olduğu hızlı bir işlemdir. UV kürlenebilir formülasyonlar hızlı kürlenme, mükemmel kimyasal direnç, iyi şartlanma özellikleri ve geniş formule edilebilir kapsamı gibi bazı faydalar sağlarlar. UV ile kürleme endüstrisinde epoksi ve epoksi akrilat türevleri kaplamalar, yapı yapıştırıcıları, ileri komposit materyalleri olarak geniş bir çerçevede kullanılmaktadır. Epoksi reçineler ticari reçinelerin büyük bir sınıfıdır ve reçinenin aktif merkezi olan her moleküldeki birden fazla epoksi grubuna sahip olma özelliği ile tanımlanır. Epoksi reçineleri diğerlerinden ayıran şey mükemmel kimyasal ve solvent direncidir, iyi ısısal ve yapışma özellikleri, çapraz bağlanmada çeşitliliğidir. Bunun yanı sıra organik-inorganik hibrid materyaller süper mekanik özellikler, ısısal kararlılık ve optiksel özelliklerinden dolayı büyük bir ilgi kazanmaktadır. Asıl ilgi de optiksel membran uygulamasında büyük bir kullanım barındıran akrilik-silika hibrid materyalidir. Akrilikler kolay işlenebilirlik ve optiksel geçirgenlik sağlıyorken, silika partikülleri sertlik ve çizilme direnci sağlar. Ama silika ve akrilikler arasındaki uyumsuzluk akrilik malzemesindeki silika partiküllerinin kötü dispersiyonuna neden olur ve silika ve akriliklerin direkt bir karşımını imkansız kılar. Bu yüzden akrikler ve silikalar arasındaki kimyasal bağların oluşumuna önemli eforlar harcanılmaktadır. Alkoksisilan grubu taşıyan öncül akrilik polimerlerle tetraetilortosilanın reaksiyonu vasıtasıyla bağlı silikanın yerinde oluşumunu gerektiren solgel işlemleri, istenilen reaksiyon derecesine ulaşmak için uzatılmış zaman ve alkol su gibi ürünleri yok edebilecek önemli eforları gerektirdiğinden dolayı uygun ve kopolimerize edilebilir organik türlerle fonsiyonlaştırılmış öncül silika partiküllerle akrilik monomerlerini kullanma girişimleri yapılmaktadır. Bu çalışmada digilisidileter bisfenol A epoksi reçine tereftalik asit ve akrilik asitin değişen oranlarıyla reaksiyona sokuldu. Oluşan reçine üç farklı formülasyon hazırlamada kullanıldı, kaplandı ve UV ışığıyla kürlendi. Kaplamanın özellikleri spektroskopik aletlerle ölçüldü ve formülasyonların ısısal ve mekanik özellikleri incelendi. xvii xviii 1. INTRODUCTION Early surface coatings were limited mainly to air drying systems which film formed by either evaporation of solvent, to leave a dried film of the natural resin or oxidative crosslinking of any unsaturation present in vegetable oil based binders. French polish, based upon shellac is an example of the first type of coating, whilst alkyds or oleoresinious based systems are example of the latter. Today coatings can be divided into thermoplastic and thermoset. Thermoplastic systems primarily film form by the evaporation of solvent. As a general rule, thermoplastic coatings are based on high molecular weight polymers. Solutions of high molecular weight thermoplastic resins are normally too high in viscosity for the desired applications solids, hence dispersions of thermoplastic resins are frequently used. The natural resins were used in the protective surface coatings industry in the past but the use of natural resins has decreased in the USA since about 1930, when they were replaced by synthetic resins.the one type of synthetic resin is epoxy resin. Epoxy resins only became commercially avaliable in about 1947 [1]. Epoxy resins are commercially used in coating and various applications. The largest single use in coatings, where high chemical and corrosion resistance and adhesion are important. The presence of unsaturation at the end of the polymer backbone as a result of the reaction with acid functional acrylic monomers hs shaped epoxy resins for the radiation curing industry. Terminal unsaturated double bonds are the reactive sites for coatings and paints [2-6]. Unsaturated monofunctional and multifunctional acrylated monomer and acrylated oligomers having epoxy backbone are capable of a rational designed formulation that provides good coating properties after curing. In general, the cure process is radical and results in three dimensional network formation. The curing process is the faster and depends on the radiation dose and the time of radiation. UV curing, i.e., the process of photoinitiated conversion of polymeric materials from a liquid to a solid is a popular alternative to conventional thermal curing. UV curing process has attractive advantages over thermal curing. 1 Their major advantages are high speed process, low energy consumption due to the operation at room temparature, and enviromental friendliness by avoiding solvent exposure [7-9]. This thesis will concern the preparation of bifuctional resin formed by reaction between epoxy acrylate oligomer and terephthalic acid at different modification ratio. The modified resin is crosslinked by photo polymerization and characterized by thermal and mechanic analaysis. The coating performance is also examined. 2 2. THEORETICAL PART 2.1 Epoxy Resins Introduction Epoxy resins are organic compounds with more than one epoxide (IUPAC: oxirane) group per molecule which are used to obtain prepolymers. The term resins is now generally accepted although misleading since the compounds refferred to are low molecular mass or oligomeric compounds. Polymerization by polyaddition is based on the characteristic behaviour of epoxide groups to react with suitable reaction partners by addition. The reactivity and functionality of the di-, tri- and tetra-epoxide compounds (epoxy resins) and crosslinking compounds (curing agents) must however correspond to each other.epoxy resins can also be crosslinked directly by polymerization of the epoxide groups. The designations resin and curing agent or hardener are historical in origin but are totally irrelevant from a scientific viewpoint. Epoxy resins systems (resin/hardener combinations) are used primarily to obtain crosslinked polymers which are also usually termed epoxy resins but, correctly, should be described by detailing the crosslinking components. The use of diepoxide compounds with bifunctional addition components results in linear, soluble strcture. Adding small amounts of trifunctional components leads to branched soluble structure. Because of the numerous possibilities of combining resin and curing agent structures (known technically as formulation), the properties of epoxy resin systems are particularly easy to adjust, firstly as far as viscosity and rheological characteristics during processing, and secondly, as far as properties of the end product are concerned (tailor-made plastics). The range of applications can be considerably expanded by judicious addition or incorporation of additives such as fillers, reinforcements, flame retardants, flexibilizers and pigments. In contrast to the soluble melt-processable thermoplastics, crosslinked epoxy resins can not be shaped by heat. Their industrial application must therefore be performed in the non- 3 crosslinked state (in sollution if necessary) and the crosslinked state achieved by heat treatment or suitably extended curing times at ambient temperature [10]. Although the first products that would now be called epoxy resins were synthesized as early as 1891 it was not until the independent work of Pierre Castan in Switzerland and Sylvan Greenlee in the United States that commercial epoxy resins were marketed in the 1940s, although similar resins had been patented in the 1930s. The earliest epoxy resins marketed were the reaction products of bisphenol A and epichlorohydrin (Figure 2.1.) and this is still the major route for the manufacture of most of the resins marketed today, although there are many other types of resin available [11]. Figure 2.1: Reaction of bisphenol A and epichlorohydrin Epoxy resins are synthetic and are not the lowest cost resins potentially avaliable for most applications. Thus they most confer a property or properties to the final product which justifies their additional cost. In almost all cases they impart outstanding chemical /corrosion resistance to the cured film. If this is not required then the formulator can consider other lower cost options. Protective coatings are an area in whic
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