UV- ışınları ile sertleştirilen çeşitli akrilik filmler

Abstract

Çeşitli uygulamalarda malzemelerin yüzey kimyası ve fiziksel özellikleri önemli rol oynamaktadır. Malzemelere istenen, mekanik, optik, elektrik yada yapışma özelliklerinin kazandırılmasında kullanılan metodlara örnek olarak; yüzeye fiziksel işlem uygulanması veya yüzey içine molekül, iyon ve atomların implantasyonu verilebilir. Malzeme yüzeylerinin değişik yöntemler kullanılarak kaplanması ile; Malzeme yüzeyinin sertlik ve dayanıklılığın arttırılması, Nem ve UV-ışınlarının bozucu etkilerinin minimuma indirilmesi, CO2 ve O2 gibi gaz geçirgenliğinin azalması, Kimyasal dayanıklılığın arttırılması gibi malzeme özelliklerinde iyileştirmeler yapılabilmektedir. Bu çaiışmanin ilk aşamasında, hidroksil fonksiyonlu polidimetil siloksan ile izosiyanatoetil metakrilat (IEM) reaksiyona sokulmuş, sentezlenen akrillenmiş siloksan esaslı poliüretan oligomer İR Spektroskopisi metodu ile karakterize edilmiştir. İzoforon diizosiyanat (IPDI) ile Arcol 11 33 reaksiyona sokulmuş, molekül uçlarındaki izosiyanat grupları içeren oligomerler hazırlanmıştır. Bir sonraki aşamada ise söz konusu izosiyanat grupları hidroksietil metakrilat (HEMA) ile örtülerek oligomerlerin uçlarına akriiat fonksiyonlu gruplar takılmıştır. Daha sonra sentezlenen IPDI/ARCOL1133/HEMA oligomerlerine çeşitli oranlarda akrillenmiş siloksan oligomeri ilave edilip bu karışımlar %20 oranında dietilenglikol diakıilat (DEGDA) ve tiyodietilenglikol diakrilat (TDGDA) gio; reaktif çözücüler ile seyreltilerek, viskozitesi düşürülmüş ve fotobaşlatıcı olarak %2 oranında izobutilbenzoin eter ilavesi ile hazırlanan formülasyon daha sonra UV-ışınları ile sertleştirilerek çeşitli serbest polimerik filmler hazırlanmıştır. Söz konusu filmlerin %50, %75 ve %95 bağıl nemli ortamlarda şartlandırılmasından sonra, tensilonda çekme deneyleri ile kopma mukavemetleri ve % uzama değerleri hesaplanmıştır. Bu çalışmaların sonucunda, hazırlanan polimerik filmlerin mekanik özelliklerinin ilave edilen akrillenmiş siloksan oligomer konsantrasyonuna, reaktif çözücü tipine ve ortamın bağıl nem oranına göre değiştiği gözlenmiştir.

Coating industry is an important segment of the chemical industry and coatings are produced from a wide variety of organic resins, metals and inorganic materials using techniques of increasing technological sophistication. Energy related and ecological events have significantly influenced research and development activities in the coating industry. The industry reacted to these problems by introducing new coating technologies, such as high solids water-borne, powder and radiation curable coatings. Radiation curable coatings.which was designed for use under ultraviolet (UV) or ?? electron beam (EB) radiation have made important penetration into various sectors of the coating industry. UV-curable coatings was first commercialised in West Germany in the 1960's for furniture finishing. The major markets for UV- curable coating in the world are for: * Wood (fillers, sealears, top coats) * Metal (base coats, clearcoats, coatings for can, bottle caps, metal furniture) * Paper and paperboard (clear, overprint varnishes) * Flexible and rigid plastics * Miscellaneous (magnet wire, magnetic tape, adhesive, dental applications, optical fibber and others) The main advantages of UV-curing include ; * Elimination of solvents or thinners for application * Great minimisation of the pollution and health hazards * Very rapid cure at ambient temperature, requires very low energy * Ability to coat heat sensitive substrates such as polyethylene, propylene without detrimental effects due to heat * Low capital investment * Less plant floor space requirements * Excellent film properties and performance VI A UV-curable coating formulation include at least the following components; unsaturated oligomers, reactive diluents, photoinitiators, non reactive speciality additives. The unsaturated oligomer is the most important component in determining mechanical properties. For this reason, most of the desired coating properties must be built in the oligomer. Most of the oligomers contain an acrylate functionality. This type of unsaturation provides the highest response to actinic light compared to methacrylate, vinyl or allyl functionality. Acrylated urelhanes exhibit the well known properties of conventional urethane coatings such as high abrasion resistance, thoughness, tear strength and good low temperature properties with the superior optical properties and weatherability of polyacrylates. The unsaturated oligomer is the most important component in determining the ultimate properties of the coatings, it usually can not be used alone. Most of the oligomers have high viscosity's, low curing speeds, low cross-link densities or deficiencies in their performance. Therefore various reactive diluent systems are used to overcome above shortcomings. For this purpose generally two types of reactive diluents are used ; monofunctional and multifunctional. In general, they improve substrate wetting and for this reason, may improve adhesion. Relatively non-volatile multifunctional monomers, are used to influence curing rate, cross-link density and viscosity. These monomers arş types of acrylate and methacrylates. The following multifunctional acrylateş are used in many formulations : 1,4 butanediol diacrylate (BDODA), tetraethyleneglyco! diacrylate (TTEGDA), trimethylolpropane triacrylate (TMPTA), 1,6 hexanediol diacrylate (HDDA), thiodiethyleneglycol diacrylate (TDGDA), pentaerythritol triacrylate (PETA), glycerolpropoxy triacrylate (GPTA). The principal function of monofunctional monomers are to reduce viscosity, but it is not their only function, they may modify the final properties of the cured film. Some commonly used monofunctional monomers are ; phenoxyethyl acrylate (PEA), isobornyl acrylate (IBA), N-vinyl pyrrolidone (NVP), tetrahydrofurfuryl acrylate (THFA). The photoinitiator, as is apparent from their name, start the whole curing reaction, on exposure to UV-light. The major classes of photochemical reactions used to prepare polymers are polycondensation VII and active center polymerization. In radical polymerization, the photoinitiator initiate the curing reaction by forming free radicals after absorbing the UV energy. Other components which often appear in radiation curable-systems are nonreactive specialty chemicals such as pigments, dyes, extender pigments, defoamers, wetting agents, flatting agents, adhesion promoters, slip aids. Commercial acrylated urethane oligomers are normally prepared by a two step procedure. Polyether or polyester based macroglycols are seguencially tipped by an aromatic diisocyanate such as toluene diisocyanate (TDI), xylidine diisocyanate (XDI), cycloaliphatic isophorone diisocyanate (IPDI) and then by a hydroxyalkyl ethyl metacrylate (HEMA), etc. Isocyanatoethyl metacrylate (IEM) combines the acrylate and isocyanate functionality into one molecule, thereby eliminating one step in the oligomer synthesis. In this work, UV-cured acrylic films were prepared by using polyether glycol and polydimethylsiloxane based acrylated polyurethanes. Polysiloxanes are getting excellent properties and usefulness to this type of coating because, in the silicone containing polymers, silicone atoms contribute the inorganic character and are present either alone in the baekbone^sUafles) or with atoms of oxygen (siloxanes), carbon (silalkylenes and silarylenes), or nitrogen (silazanes). Of these, the siloxane or silicone polymers have been studied the most and are also of the greatest commercial importance. Poly siloxane can be prepared by four major types of polymer forming reactions, including : (1) hydrolysis of chlorosilanes; (2) egulibration of lower siloxanes; (3) ring opening polymerization reactions and (4) special condensation polymerization reactions. Of these four major types of reactions, the first and the last are step growth polymerization processes, equilibration is a step growth redistribution process and the ring opening polymerization is a chain growth polymerization reaction. In principle, equilibration reactions are perhaps the most characteristic reactions in the polysiloxane forming processes because, with the notable exception of certain types of anionic ring opening polymerizations. The most important siloxane polymer is poly dimetylsiloxane (POMS), CH3. Si - 0- CH3 n VIII PDMS is also one of the most flexible chain molecules known, both in the dynamic sense and in the equilibrium sense. Dynamic flexibility refers to a molecule's ability to change spatial arrangements by rotations around its skeletal bonds. One of the most exceptional properties of siloxane polymers is their excellent elasticity at unusual low temperatures. The structural features of poly siloxane which are responsible for their highly pronounced elasticity are generally as follows : (1) the unusual flexibility of the Si-O-Si bond angles; (2) the large difference in sizes of the alternating silicon and oxygen atoms; (3) the relatively free rotation of the organic substitutents around the C-Si bond and the shielding of the main chain back bone by these pendant groups (4) the regularly coiled helical structures of polymer segments at lower temperatures and (5) the relatively large free volume between neigh bouring chain segments. The unusually high thermal and thermo-oxidative stability of the polysiloxanes is another important property of this family of polymers. While most polymers containing carbon-carbon single bond main chain units begin to degrade at temperatures above 250°C, rigorously purified polysiloxanes are stable under high vacuum or in an inert atmosphere to at least 350- 400 °C Siloxane polymers have much higher gas permeability than most other elastomeric materials. Therefore, these polymers have long been of interest for gas separation membranes, the goal being to vary the basic siloxane structure to improve selectivity without decreasing permeability. Soft contact lenses prepared from PDMS provide a final example. The oxygen required by the eye for its metabolic process must be obtained by inward diffusion from the air rather than through blood vessels. PDMS is ideal for.such lenses because of its high oxygen permeability ; but it is too hydrophobic to be adequately wetted by the tears covering the eye. This hydrophobicity prevents the lens from feeling right and can also cause very serious adhesion of the lens to the eye itself. One way to remedy this problem is to graft a thin layer of a hydrophilic polymer to the thinness of the coatings, the high permeability of the coating, the high permeability of the PDMS is essentially unaffected. Regardless of their molecular weight and because of their very low glass transition temperatures, all linear polysiloxanes are essentially viscous fluids, varying in viscosity from easily flowing oils to either a very thick consistency or a hard paste. As result, their vulcanizates are generally soft and highly extendible with a breaking stress at ambient temperature usually in the range of 50 to 80 psi (345- 550 kpa). Therefore, in order to impart more useful mechanical properties to polysiloxane rubbers, they must be IX compounded with appropriate fillers, which increase tear strength and abrasion resistance as well as tensile strength 1.100 to about 1.500 psi (7 to about 10 Mpa), an elongation at break about 250 to 600-800 %, a tear strength in the range of 100 to 200 psi (0.7 to 1.7 Mpa), a resilience of about 50%, a hardness of between 40 to 80 shore A units. There is no other polymeric material which serves as a better flexible, electrical insulation than silicon rubber. Indeed, the early development of the siloxane polymers resulted from their highly favourable electrical properties, particularly their high insulation resistance and low dielectric loss. Polysiloxane exhibit very useful characteristic surface properties. They show high water repellence and surface tension (from about 20 to 25 dynes/cm for molecular weights above 150.000). Although water repellence is very prominent for a polysiloxane surface, these polymers are nevertheless, highly permeable to water vapour and are used for protecting textiles or leather, while still allowing substrate " breathing " ( the passage of air and water vapour through the coating). Polysiloxanes are also permeable to other gases, particularly to_%oxygen, for which the permeability is about 6x10 cm, compared to 2.8x10 cm (RTP) cm/cm.sec.cm Hg for a nitrogen. Polidimetilsiloxane has the highest value in this respect of all polymeric materials and is therefore, used for semipermeable membranes for oxygen enrichment. Artificial organs and implants to replace diseased, defective or destroyed components of the body are used. by essentially every medical speciality medical grade silicone elastomers is the only elastomer generally recognised as safe and effective as a material of construction for soft, flexible, elastomeric implants. The formulation contain no materials with potential for bioclagradation or adverse biocompatibility. At the first stage of the our work, acrylated urethane oligomers have been prepared based on polyol oligomers namely, polyether poliol (ARCOU 1133), cycloaliphatic isophorone diisocynate (IPDI) and hydroxyethyl metacrylate (HEMA) and hydroxyl functional grup containing polydimethylsiloxane and isocyanatoethyl methacrylate (IEM). IPDI based acrylated urethane oligomers were synthesised by slowly adding, two moles of IPDI into a nitrogen-purged dried reaction flask containing one mole of ARCOL 1133. After IPDI addition was cpmpleted, about 0.08 % (by weight) dibutyltin dilaurat (T-12) was added and eight hours were allowed to complete the reaction. Then HEMA was added into the reaction mixture. The temperature was kept at 30 ± 2 °Ç to avoid thermal polymerization of unsaturated acrylate groups. The structures of the synthesised acrylated polyurethanes were characterised by investigation of IR spectra. In IR spectra, the complete disappearance of asymmetric stretching vibration bands at 2275 cm which is characteristic for -NCO group and disappearance of hydroxyl bands at 3600 cm and finally appearance of stretching vibration band of N-H at 3350 cm which is characteristic for urethanes, were all used to monitor the extend of reaction in prepolimer. Acrylated polydimethylsiloxane oligomers were synthesised by slowly adding two moles of IEM into a nitrogen-purged dried reaction flask, containing one mole of hydroxyl functional polydimethylsiloxane. The temperature was kept at 30 T 2 °C to avoid thermal polymerization of unsaturated acrylate groups after IEM addition was completed, about 0.08% (by weight) dibutyltin dilaurat (T-12) was added and eight hours were allowed to complete the reaction. The structures of the synthesised acrylated polydimethylsiloxane were characterised by investigation of IR spectra. At the second stage of our work, the effects of acrylated polydimethyl siloxane oligomer content, reactive diluents type and relative humidity on physical properties of the UV-cured acrylated polyurethane films were investigated. > For this purpose eight different formulations were prepared and systematically investigated. In these formulations, polyglycol ether based acrylated polyurethane oligomer content was kept between 78-48 % (by weight) and acrylated polydimethylsiloxane was added between 10-30 %. Photoinitiator concentration was kept (2%) constant and two different reactive diluents content were kept 20% ( by weight). Homogeneously mixed liquid samples were poured into teflon coated molds to obtain free films for tensile tests. These samples were irradiated for 75 seconds from onş side, using a 300 W Osrartruitravitalux lamp as the UV source. Polymeric; u-ms were conditioned at 50 %, 75 % and 95 % relative humidity and stress-strain measurements were obtained at room temperature by using table were obtained at room temperature by using floor models instron tensile testing machines. In this work, it has been shown that mechanical properties of all the polymeric films prepared were depend on the concentration and type of reactive diluents, acrylated polydimethylsiloxane content used and relative humidity of media. XI Stress- strain values of the polymeric films showed that these films were suitable as coating materials. Mechanical test results are given in the tables: Table-1 Mechanical Test Results of IPDI/ ARCOL 1 1 33/HEMA/ 20 DEGDA/ 2 BE Polymeric Films (50% Relative Humidity) Table-2 Mechanical Test Results of IPDI/ARCOL 1 1 33/ HEMA/ 20 TDGDA/ 2 BE Polymeric Films (50% Relative Humidity) XII Table-3 The Mechanical Test Results of IPDI/ARCOL 1 1 33/HEMA/ 20 DEGDA/ 2 BE Polymeric Films ( 75 % Relative Humidity ) Table-4 The Mechanical Test Results of IPDI/ARCOL 1 1 33/HEMA/ 20 TDGDA/ 2 BE Polymeric Films ( 75 % Relative Humidity ) XIII Table-5 Mechanical Test Results of IPDI/ARCOL 1 1 33/ HEMA/ 20 DEGDA/ 2 BE Polymeric Films ( 95 % Relative Humidity ) Table-6 Mechanical Test Results of IPDI/ARCOL 1 1 33/ HEMA/ 20 TDGDA7 2 BE Polymeric Films ( 95 % Relative Humidity ) XIV Table-7 Water Absorption Test Results of IPDI/ARCOL 1133/ HEMA/20 DEGDA/2BE Polymeric Films Table-8 Water Absorption Test Results of IPDI/ARCOL 1 133/ HEMA/20 TDGDA/2BE Polymeric Films XV Table-9 Mechanical Test Resuts of IPDI/ ARCOL1133/HEMA/2BE Polymeric Films