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Silikon esaslı endüstriyel çözümler

Silicon based industrial solutions

  1. Tez No: 895158
  2. Yazar: DENİZ GÜNEŞ
  3. Danışmanlar: DOÇ. DR. BÜNYAMİN KARAGÖZ
  4. Tez Türü: Doktora
  5. Konular: Kimya, Mühendislik Bilimleri, Polimer Bilim ve Teknolojisi, Chemistry, Engineering Sciences, Polymer Science and Technology
  6. Anahtar Kelimeler: Belirtilmemiş.
  7. Yıl: 2023
  8. Dil: Türkçe
  9. Üniversite: İstanbul Teknik Üniversitesi
  10. Enstitü: Lisansüstü Eğitim Enstitüsü
  11. Ana Bilim Dalı: Kimya Ana Bilim Dalı
  12. Bilim Dalı: Kimya Bilim Dalı
  13. Sayfa Sayısı: 98

Özet

Çoğumuz silikonu duymuş ve hakkında fikir sahibi olsak da hayatımıza ne kadar sirayet ettiğinin farkında değiliz. Silikon öylesine hayatımızın içindedir ki bugün duvar boyasından tarıma, göz damlasından yatak süngerine, şampuanlardan rujlara, cep telefonlarından biberonlara kadar birçok alanda kullanılmaktadır. Silikon kimyasında uzmanlaşmış firmaların global büyüklükte olduğunu dikkate aldığımızda bu butik kimyanın özel bir alan olduğunu görebiliriz. Yüksek termal dayanım, kimyasal olarak inert olma, düşük yüzey enerjisi, hidrofobik karakter, kayganlaştırıcı etkisi, düşük refraktif indeksi ve yeni molekül tasarımlarına imkân vermesi sayesinde silikonların hayatımızda yaygınlaştığını ifade edebiliriz. Lineer polisiloksanlar endüstriyel olarak siklik moleküllerin anyonik veya katyonik halka açılma polimerizasyonu veya dialkoksi/asetoksi silanların kondenzasyonu ile elde edilmektedir. Süper ıslatıcı trisiloksanlar, polieter modifiye polisiloksanlar, ABn blok kopolimerler ve sıvı silikon kauçuk kürlenmesi ortogonal bir reaksiyon olan silisyum hidrür ve allilik bir çift bağ arasındaki hidrosilasyon reaksiyonu üzerinden gerçekleştirilmektedir. Silikon kimyasının bir diğer renkli yönü de silanların alkil, aril, merkapto, izosiyanat, epoksi, amin vb. birçok fonksiyoneliteye sahip olmasıdır. Silanlar ortamdaki hidroksi kaynakları varlığında kolayca reaksiyona giren yapılardır. Bu yapıların kondenzasyonu ile üç boyutlu polihedral oligomerik silseskuioksanlar (POSS) elde edilmektedir. POSS molekülleri üstün mekanik ve termal özellikleri sayesinde son yıllarda kozmetik, köpük kesici, kompozit gibi birçok alanda hem endüstriyel hem de akademik çalışmalara konu edilmektedir. Bu tezde silikon kimyasının daha geniş alanlara yayılması için akademik etkisi yüksek ve endüstriyel olarak ticarileştirilebilecek yeni çözümler geliştirilmesine odaklanılmıştır. Tez kapsamında ilk olarak polipropilen oksit (PPO) modifiye POSS sentezlenmiş ve kimyasal yapısı FTIR, TGA, 1H-NMR, 29Si-NMR, GPC ve DLS ile aydınlatılmıştır. PPO-POSS oranı %1-10 olacak şekilde su bazlı bir köpük kesici emülsiyonu hazırlanarak orta PVC bir dekoratif boyaya sadece %0,2 oranında eklenerek boyadaki yoğunluk artışı takip edilerek mikro köpük giderme performansı incelenmiştir. Buna göre, %3 ve üzerinde makro köpükler giderilirken, mikro köpükleri gidermek için %10 oranının yeterli olduğu kanıtlanmıştır. İlave olarak PPO-POSS yapısının yüzey gerilimini düşürücü etki gösterdiği tespit edilmiştir. İkinci konu kapsamında literatürde ilk kez core-shell poliborosiloksan (PBS) sentezlenmiş ve kendiliğinden alev geciktirici etkili ilk ısıya dayanıklı boya geliştirilmiştir. PBS yapısı FTIR, TGA, 11B-NMR, TEM ve XPS analizi ile aydınlatılmıştır. TGA analizleri bize yeni oluşan Si-O-B bağının 120-200 °C arasında termal olarak kırıldığını gösterirken, TEM ölçümleri çekirdek-kabuk (core-shell) yapı oluşumunu gözler önüne sermiştir. Alüminyum pigment pasta ve PBS ile hazırlanan ısıya dayanıklı boya yaş film kalınlığı 100 mikron olacak şekilde metal plakaya uygulanmış ve metal plaka önce oda sıcaklığında kendiliğinden kurutulup sırasıyla önce 200 °C'de 30 dk kül fırınında kürlenip 600 °C'de 2 saat bekletilerek kendiliğinden oda sıcaklığına soğutulmuştur. Akabinde yapılan yapışma mukavemeti (cross-cut) testine göre core-shell yapıdaki PBS reçineleri ısıya dayanıklı boya geliştirilmesi için mükemmel bir platform olduğu gösterilmiştir. Kıyaslama yapabilmek için tek aşamada ekleme (one-pot) metodu ile de PBS reçineler sentezlenmiş ve core-shell yapının performans farkı net bir şekilde ortaya konmuştur. Ayrıca, bor içeriğinin yüksek olmasının da yapışmayı pozitif yönde etkilediği tespit edilmiştir. Üçüncü ve son konuda ana zincirde trisiloksan ve uzun alkil (C13) grupları taşıyan alifatik bir poliüretan (PU) sentezi yapılmıştır. Sentezlenen polimerin yapısı FTIR, 1H-NMR, GPC ile karakterize edilmiş ve pamuk/poliester kumaşlara aplike edilerek kumaş yüzeyini ne kadar hidrofobikleştirdiği temas açısı ölçümleri ile takip edilmiştir. Buna göre, işlemsiz kumaşlar su damlacıklarını emerken PU aplike edilmiş kumaşların temas açısı 89°-96° olarak belirlenmiştir. Kumaş yüzeyleri hidrofobik karakterde olmasına karşın yağmur suyunu simüle eden sprey testine göre PU aplike edilmiş kumaşların dahi ıslandığı tespit edilmiştir. Tez savunması öncesinde alifatik poliüretan yerine aromatik poliüretan sentezi yapılarak temas açıları 96°-116° olarak elde edilmişse de sprey testinde kumaşlar yine ıslanmıştır.

Özet (Çeviri)

Although most of us have heard of silicon and have an idea about it, we are not aware of how much it has spread to our lives. Silicone is so in our lives that it is used in many areas from wall paint to agriculture, from eye drops to bed sponges, from shampoos to lipsticks, from mobile phones to baby bottles. Considering that companies specializing in silicon chemistry are of global size, we can see that this boutique chemistry is a special field. We can state that silicones have become widespread in our lives thanks to their high thermal resistance, chemically inert structure, low surface energy, hydrophobic character, lubricating effect, low refractive index and enabling new molecular designs. According to the import and export data obtained from Turkish Statistical Institute silicon based products increase the current account deficit of our country. For instance, Turkey import and export values are 273 M$ and 36 M$, respectively in 2022. Import is almost doubled in 2022 compared to the 2019. Briefly, silicon based products are also an important source for Turkey. Linear polysiloxanes are the basic form of siloxanes where we use them in the laboratory as an oil bath, color deepening agent in textile production, as mold release agent in metal working fluids or shoe production and in cosmetics mainly as emollient. Linear polysiloxanes are obtained industrially from the anionic or cationic ring-opening polymerization of cyclic molecules or the condensation of dialkoxy/acetoxy silanes. Polyether modified polysiloxanes produced via“grafting to”method are comb-like structures and mainly used as additive in the formulation like surface modifier in paint sector, stabilizer in PU foam production and emulsifier in cosmetics. Synthesis of polyether pendant polysiloxanes, ABA or AB block copolymers and curing of liquid silicone rubber is carried out through the hydrosilylation reaction between silicon hydride and an allylic double bond, which is an orthogonal reaction. Another colorful aspect of silicone chemistry is silanes that have many functionalities such as alkyl, aryl, thiol, isocyanate, epoxy, amine. Silanes easily react in the presence of the hydroxy sources. Therefore, silanes are mainly used for surface treatments such as glass, concrete, ceramic or composites to enhance the adhesion or water repellency. Three-dimensional polyhedral oligomeric silsesquioxanes (POSS) are obtained by condensation of various silane structures. POSS molecules, thanks to their superior mechanical and thermal properties, have been the subject of both industrial and academic studies in many fields such as cosmetics, defoamer and composite in recent years. In this thesis, we focused on the development of new solutions with high academic impact and industrial commercialization to spread silicon chemistry to wider areas. Within the scope of the thesis first chapter is dedicated to the novel POSS derivatives namely polypropylene oxide (PPO) modified POSS and its performance as defoamer in a decorative paint. Foam is physically stabilized air bubbles in the matrix that result in undesired surface defects on the paint film. Defoamers are foam destroying additives which increase the paint density. They are mainly composed of water incompatible carriers such as silicon oils or mineral oils as main component, hydrophobic particles as foam destabilizer, surface active agents as emulsifier or to lower the surface tension, thickener, and others. In this thesis, PPO-POSS was prepared via hydrolysis and condensation of tetrasilane and PPO functional dimethyldisiloxane as active ingredient of defoamer. Chemical structure of PPO-POSS was characterized via FTIR, TGA, 1H-NMR, 29Si-NMR, GPC and DLS analysis. TGA thermogram showed 4.82% residue at 895 °C that indicates the formation of Si-O-Si network. As expected 29Si-NMR spectrum of PPO-POSS reveals the D and Q units at 12 ppm and -108 ppm, respectively. Molecular weight of PPO-POSS found to be 15500 Da and multi-curved according to the GPC analysis run with toluen as solvent. Particle size distribution for PPO-POSS were obtained as 1 micron which is attributed to the coagulation. In order to test the performance of PPO-POSS, water-born medium pigment volume concentration (PVC) paint and PPO-POSS containing water based defoamer emulsion were prepared. It has been found that 60 ppm PPO-POSS is effective against macro foam while 200 ppm PPO-POSS is required for micro foam removal. In addition, surface tension of the PPO-POSS (% 0,1 in water) was measured as 35,3 dyn/cm while PPO is 42,5 dyn/cm (0,1% in water) which is a fair indication of surface tension reduction that explains the results. As a second subject, core-shell polyborosiloxanes were synthesized for the first time in the literature. It is a unique example of silicon resins as it is heat-resistant and flame-retardant without using external flame retardant. Boron and silicon containing polymers, namely, polyborosiloxanes (PBSs) have been extensively studied in the literature due to their heat resistant, flame retardant, ceramic forming, and self-healing properties. The latter is due to the nature of the -B-O-Si- bond in the network structure, which splits and combines reversibly due to moisture susceptibility. In addition, the high bonding energies of B-O and Si-O, 537.6 kJ/mol and 460.5 kJ/mol, respectively, boost the thermal properties in combination with the glassy film formation of boron compounds. Another factor affecting the thermal stability is the organic substituent of the Si-R bond, where R is usually selected from the methyl or phenyl groups due to their long half-life time at 250 °C, which are approximately 14 months and 11 years, respectively. Therefore, we aimed to prepare phenyl-containing PBS resin due to its unique properties. Core-shell formation was allowed by sequential addition of ingredients with fixed conversions. Subsequent addition of boric acid into the pre-condensate and a further condensation reaction resulted in the formation of the shell layer through the introduction of the -Si-O-B- bonds to the network of the PBS. The PBS structures were elucidated by FTIR, TGA, 11B-NMR, TEM and XPS analysis. TGA analyzes showed that Si-O-B bond was thermally broken at 120-200 °C after solvent evaporation. PBS, on the other hand, is stable up to 500-600 °C and is in the maximum deterioration phase at 620 °C. PBS gives an almost 50% charry residue at 900 °C, which is compatible with the theoretical calculation. Furthermore, improvement of thermal properties of the boron-incorporated polyphenylsiloxane matrix has been proved by TGA, where the residual content was doubled at 900 °C. 11B-NMR was performed to observe the boron linkage characteristic in PBS-2. There appeared one broad peak at 18.7 ppm, which indicated the formation of both B(OSi)3 and B(OSi)2OH structures. SEM-energy-dispersive X-ray spectroscopy (EDX) and SEM images of the PBS-1 and PBS-2 resins were obtained for observing the core-shell structure of the boron-based resins. No meaningful results were obtained. The morphology and core-shell structure of the resulting PBS-1 and PBS-2 were investigated via TEM images which revealed the formation of the core-shell structure via color contrast between the polysiloxane core and PBS shell. The core-shell structures were irregular, as expected. The PBS resins were used in heat resistant paint as a binder in combination with aluminum pigment. The PBS paint was applied to the metal plate with a wet film thickness of 100 microns, and the metal plate was dried at room temperature, then cured in a muffle furnace at 200 °C for 30 minutes, and kept at 400 or 600 °C for 2 hours, then cooled to room temperature. Cross-cut tests revealed that core-shell PBS resins have been shown to be an excellent heat resistant platform. One-pot PBS resins were also synthesized and compared with core-shell PBS. Here, the difference of core-shell structure is clearly revealed. It was also demonstrated that the incorporation of boron in the core-shell structure showed better adhesion strength than the one-pot preparation of PBS. Using this method, not only the heat resistance requirement of the industrial coating was achieved but also the flame-retardant ability was introduced. As the third and last subject, it was aimed to address fluorine-free water repellent coating using silicon and alkyl containing polymers. Perfluoroalkyl substances are used in textile coatings, kitchenware applications, paints to provide water repellent surfaces that resist to weathering, corrosion, abrasion etc. Due to the environmental and health concerns fluorine containing materials restricted and alternatives to this structure is highly demanded. For this purpose, an aliphatic polyurethane synthesis has been carried out with trisiloxane and long alkyl (C13) groups in the main chain. Therefore, reactive double bond functional dialkyl itaconate prepared via itaconic acid and alkyl epoxide in the presence of tertiary amin as catalyst. This precursor reacted with heptamethyltrisiloxane to give a silicon containing diol to react further with diisocyanate. All reactions were monitored with FTIR analysis. Trisiloxane and alkyl containing polyurethane was characterized by FTIR, NMR and GPC. It was demonstrated via contact angle measurements that PU impregnated fabric increases the contact angle that shows hydrophobic character. Accordingly, while untreated fabrics absorb water droplets, the contact angle of PU-applied fabrics was determined as 89-96°. Although the fabric surfaces became hydrophobic it has been determined that even PU-applied fabrics get wet according to the spray test simulating raining effect. Studies after submission of this thesis where aliphatic diisocyanate replaced by aromatic diisocyanate showed higher contact angle up to 116 yet failed from spray test.

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