Seçilmiş polimerik otomotiv dış malzemeleri bazında hızlı yaşlandırmalar ve Türkiye'de doğal yaşlandırma arasındaki korelasyonun araştırılması
Yükleniyor...
Dosyalar
Tarih
2022
Yazarlar
Dergi Başlığı
Dergi ISSN
Cilt Başlığı
Yayıncı
Bursa Teknik Üniversitesi, Lisansüstü Eğitim Enstitüsü
Erişim Hakkı
info:eu-repo/semantics/openAccess
Özet
Bu tez çalışmasında otomotiv dış malzemesi olarak seçilen PMMA, ABS+ASA ve ABS yüzeyli malzemelerin Türkiye'de Bursa ilinde ilk kez doğal ortamda yaşlandırılması ve hızlandırılmış yaşlandırma metotları olarak seçilen ksenon ark lambalı ve ultraviyole lambalı metotlar ile yaşlandırılması sonucunda elde edilen numunelerin moleküler ve makromoleküler analizleri ile kopma mukavemeti ve uzama değerlerinin, renk ve parlaklık özelliklerinin tespiti ile yaşlandırma metotları arasındaki korelasyonun araştırılması amaçlanmıştır. Doğal ortamda yaşlandırma test düzeneği Türkiye'de ilk kez EN ISO 877-1 standardına uygun olarak bu tez çalışması kapsamındanda Türkiye Bilimsel ve Teknolojik Araştırma Kurumu Bursa Test ve Analiz Laboratuvarı (TÜBİTAK BUTAL)'nda kurulmuştur. 11 Kasım 2019 - 11 Kasım 2020 tarihleri arasında bir yıl süreyle doğal yaşlandırma testi gerçekleştirilmiştir. Yaklaşık olarak iki aylık periyotlarda numuneler alınmış olup toplamda altı seri numune elde edilmiştir. Ksenon ark lambalı hızlandırılmış yaşlandırma, EN ISO 4892-2 (Metot A, çevrim no: 4) standardı koşullarında toplamda 1920 saat olarak gerçekleştirilmiştir. 330 saatlik periyotlarda altı seri numune elde edilmiştir. Ultraviyole lambalı hızlandırılmış yaşlandırma, EN ISO 4892-3 (Metot A, çevrim no: 4) standardı koşullarında toplamda 1512 saat olarak gerçekleştirilmiştir. 252 saatlik periyotlarda altı seri numune elde edilmiştir. Yaşlandırma metodunun moleküler yapıdaki değişiklik üzerine etkileri FTIR analizleri ile, ısıl bozunma farlılıkları üzerine etkileri TGA analizleri ile belirlenmiştir. Polimer yüzey özelliği olan renk ve parlaklık özelliklerindeki değişim bazında polimerlerin yaşlanma dayanımları tespit edilmiştir. Yaşlandırmanın polimerlerin performans parametresi üzerine etkisi kopma mukavemeti testi ile tespit edilmiştir. Tüm değerlendirme parametreleri bazında ve tüm yaşlandırma metotlarında PMMA istatiksel olarak kayda değer bir değişime uğramazken ABS+ASA ve ABS numunelerinde önemli sayılabilecek değişimlerin olduğu gözlemlenmiştir. PMMA polimerindeki en büyük değişim kopma uzamasında olmuş olup bu değişimin katmanlı yapıdaki PMMA harici tabakadan kaynaklandığı belirlenmiştir. PMMA numunelerinin yüzey görünümlerinde, moleküler yapı ve bozunma davranışında fark edilir bir değişim tespit edilmemiştir. ABS+ASA ve ABS malzemelerinin her üç yaşlandırma ortamından da etkilendiği ve tüm değerlendirme parametreleri bazında özellik değişimine uğradığı görülmüştür. Her iki polimerin de benzer yaşlanma davranışı gösterdiği tespit edilmiştir. FTIR ile yapılan moleküler yapıdaki değişim analizinde fotooksidatif bozunma sonucunda 1600 – 1800 cm-1'deki karbonil ve 3000 – 3400 cm-1'deki hidroksil titreşimlerine ait yeni absorpsiyon bantlarının oluştuğu ve vinil yapıdaki pik şiddetlerinin azaldığı görülmüştür. FTIR spektrumundaki bu farklılık her iki polimer malzemenin de moleküler bazda benzer bozunmaya maruz kaldığı bilgisini vermektedir. Moleküler yapıdaki bu bozunma durumu TGA analizi ile de termal bozunmadaki davranış farklılığı olarak ölçülmüştür. Moleküler bazdaki bozunmayı oluşturan yaşlanma süresinin artması (maruz kalınan ışıma miktarının da artması) numunelerin ısı altındaki bozunmasının hızlanmasını sağlamıştır. Renk ölçümünde yüzey özelliklerinin önemli olduğu ve yüzey dokusundaki değişimlerin spektrofotometre ile tespit edilemediği bu nedenle, renk farkı değerlendirmesinin görsel renk değerlendirme ile yapılmasının uygun olduğu bulunmuştur. Her iki numunenin de yüzeylerinde renk değişimi ve parlaklık azalması görülmüştür. Tüm veriler birlikte değerlendirildiğinde PMMA'nın her üç yaşlandırma metodundan da etkilenmediği ancak ABS+ASA ve ABS numunelerinin büyük ölçüde etkilendiği, en fazla etkilenen polimerin ABS+ASA olduğu, en yıkıcı yaşlandırma metodunun ise ultraviyole lamba ile hızlandırılmış yaşlandırma olduğu ve doğal yaşlandırmanın diğer iki metoda nazaran daha hafif az hasar veren bir metot olduğu tespit edilmiştir. Yaşlandırma metotları arasında kopma mukavemeti, parlaklık ve gri skala ile renk farkı değerlendirmesi parametreleri bazında korelasyonun olduğu ve regresyon bazlı yapılan eğri tahminlemesindeki R2 katsayısının yüksek olduğu bulunmuştur. En yüksek R2 değeri, parlaklık parametresinde oluşmuştur. Tüm verilerin birlikte değerlendirildiği korelasyon analizinde, tek tek parametreler bazında yapılan korelasyon analizlerindekinden daha yüksek bir korelasyon katsayısı elde edilmiştir. Bu çalışma sonucunda bazı parametreler bazında yaşlandırma metotları arasında korelasyon yapılabileceği ve bir metoda göre yapılan yaşlandırma sonuçlarının diğer metotlara dönüştürülebileceği anlaşılmıştır. Bu tespit doğrultusunda, malzemelerin doğal ortamda yaşlanma sürelerinin tahminlemesinin, laboratuvar koşullarında yapılan yaşlandırma test sonuçlarının çalışma kapsamında elde edilen denklemleri kullanılarak yapılabileceği sonucuna varılmıştır.
In this study, PMMA, ABS+ASA and ABS surfaced materials, selected as automotive exterior materials were exposed to natural weathering for the first time in Bursa city in Turkey and accelerated weathering methods by xenon arc lamp and ultraviolet lamps to investigate the correlation between natural and accelerated weathering methods by analysis of molecular and macromolecular, determining of tensile strength and elongation, color difference and gloss properties on obtained samples from weatherings. As the first time in Turkey natural weathering test fixture was prepared according to EN ISO 877-1 in TÜBİTAK BUTAL. All samples were exposed to natural weathering conditions directly during one year (between November 11, 2019 and November 11, 2020). Six series of test samples were obtained by removing from the test fixture approximately in every two months. Accelerated weathering method by xenon arc lamp was carried out according to EN ISO 4892-2 (Method A, cycle no: 4) as totally 1920 hours. Six series of samples were obtained for periods of every 330 hours. Accelerated weathering method by ultraviolet lamps was carried out according to EN ISO 4892-3 (Method A, cycle no: 4) as totally 1512 hours. Six series of samples were obtained for periods every 252 hours. The effects of the weathering method on the changes in the molecular structure were determined by FTIR analysis, and the effects on the thermal degradation differences were determined by TGA analysis. The weathering resistance of the polymers was determined by changing properties of color and gloss, which are polymer surface properties. The performance parameter of polymers was determined by tensile strength test. Statistically PMMA did not undergo any change considerably, while significant changes were observed in ABS+ASA and ABS samples for all weathering methods. The noticeable change in PMMA polymer was in elongation at break and it was determined that this change was caused by the layer other than PMMA in layered structure. No noticeable change was detected in surface appearance, molecular structure and degradation behavior of PMMA samples. It was observed that ABS+ASA and ABS materials were affected by all three weathering methods and their properties changed and also both polymers showed similar weathering resistance. In the analysis of change in molecular structure by FTIR, it was observed that as a result of photooxidative degradation, new absorption bands belonging to carbonyl vibrations at 1600-1800 cm-1 and hydroxyl vibrations at 3000-3400 cm-1 were formed and the peak intensities in the vinyl structure decreased. This degradation state in molecular structure was also measured as the behavioral difference in thermal degradation by TGA analysis. Increasing of exposure time, which causes the degradation on molecular structure, resulted an acceleration of degradation of samples under heat. It has been found that surface properties are important in color measurement and the changes in surface texture cannot be detected by spectrophotometer, therefore it is appropriate to determine the color difference by visual color evaluation. Color change and decrease in gloss were observed on the surfaces of both polymer samples. As a result, PMMA was not affected by all three weathering methods, but ABS+ASA and ABS samples are significantly affected, the most affected polymer is ABS+ASA, and the most destructive weathering method is accelerated weathering by ultraviolet lamps and natural weathering has more mild effects. It was found that there was a correlation between the weathering methods on the basis of evaluation parameters as breaking strength, gloss and gray scale and color difference, and also the R2 coefficient in the regression-based curve estimation was high. The highest R2 value occurred in the gloss parameter. In correlation study for all data it was observed that correlation coefficient was higher than the correlation coefficients of each parameter. This study showed that correlation can be done between weathering methods for some parameters and the results of a weathering method can be converted to other methods. As a result of this determination, the time estimation for the natural weathering became possible when test results of the accelerated weatherings obtained by the laboratory by using transformation equations created by curve estimation.
In this study, PMMA, ABS+ASA and ABS surfaced materials, selected as automotive exterior materials were exposed to natural weathering for the first time in Bursa city in Turkey and accelerated weathering methods by xenon arc lamp and ultraviolet lamps to investigate the correlation between natural and accelerated weathering methods by analysis of molecular and macromolecular, determining of tensile strength and elongation, color difference and gloss properties on obtained samples from weatherings. As the first time in Turkey natural weathering test fixture was prepared according to EN ISO 877-1 in TÜBİTAK BUTAL. All samples were exposed to natural weathering conditions directly during one year (between November 11, 2019 and November 11, 2020). Six series of test samples were obtained by removing from the test fixture approximately in every two months. Accelerated weathering method by xenon arc lamp was carried out according to EN ISO 4892-2 (Method A, cycle no: 4) as totally 1920 hours. Six series of samples were obtained for periods of every 330 hours. Accelerated weathering method by ultraviolet lamps was carried out according to EN ISO 4892-3 (Method A, cycle no: 4) as totally 1512 hours. Six series of samples were obtained for periods every 252 hours. The effects of the weathering method on the changes in the molecular structure were determined by FTIR analysis, and the effects on the thermal degradation differences were determined by TGA analysis. The weathering resistance of the polymers was determined by changing properties of color and gloss, which are polymer surface properties. The performance parameter of polymers was determined by tensile strength test. Statistically PMMA did not undergo any change considerably, while significant changes were observed in ABS+ASA and ABS samples for all weathering methods. The noticeable change in PMMA polymer was in elongation at break and it was determined that this change was caused by the layer other than PMMA in layered structure. No noticeable change was detected in surface appearance, molecular structure and degradation behavior of PMMA samples. It was observed that ABS+ASA and ABS materials were affected by all three weathering methods and their properties changed and also both polymers showed similar weathering resistance. In the analysis of change in molecular structure by FTIR, it was observed that as a result of photooxidative degradation, new absorption bands belonging to carbonyl vibrations at 1600-1800 cm-1 and hydroxyl vibrations at 3000-3400 cm-1 were formed and the peak intensities in the vinyl structure decreased. This degradation state in molecular structure was also measured as the behavioral difference in thermal degradation by TGA analysis. Increasing of exposure time, which causes the degradation on molecular structure, resulted an acceleration of degradation of samples under heat. It has been found that surface properties are important in color measurement and the changes in surface texture cannot be detected by spectrophotometer, therefore it is appropriate to determine the color difference by visual color evaluation. Color change and decrease in gloss were observed on the surfaces of both polymer samples. As a result, PMMA was not affected by all three weathering methods, but ABS+ASA and ABS samples are significantly affected, the most affected polymer is ABS+ASA, and the most destructive weathering method is accelerated weathering by ultraviolet lamps and natural weathering has more mild effects. It was found that there was a correlation between the weathering methods on the basis of evaluation parameters as breaking strength, gloss and gray scale and color difference, and also the R2 coefficient in the regression-based curve estimation was high. The highest R2 value occurred in the gloss parameter. In correlation study for all data it was observed that correlation coefficient was higher than the correlation coefficients of each parameter. This study showed that correlation can be done between weathering methods for some parameters and the results of a weathering method can be converted to other methods. As a result of this determination, the time estimation for the natural weathering became possible when test results of the accelerated weatherings obtained by the laboratory by using transformation equations created by curve estimation.
Açıklama
Anahtar Kelimeler
Otomotiv Mühendisliği, Automotive Engineering, Polimer Bilim ve Teknolojisi, Polymer Science and Technology, ABS, PMMA
