Farklı polipropilen matris ve silisyum karbür katkı oranlarına sahip polimer kompozit fiberlerin üretimi ve karakterizasyonu
Production and characterization of polymer composite fibers with different polypropylene matrix and silicon carbide additive ratios
Yazar: ALİ YERLİYURT
Danışman: PROF. DR. BURAK ÖZKAL
İstanbul Teknik Üniversitesi / Lisansüstü Eğitim Enstitüsü / Malzeme Bilimi ve Mühendisliği Ana Bilim Dalı / Malzeme Bilimi ve Mühendisliği Bilim Dalı
Derece: Yüksek Lisans, 2022
Konu: Mühendislik Bilimleri = Engineering Sciences
Dizin: Karakterizasyon = Characterization ; Polimer kompozitler = Polymer composites ; Polipropilen = Polypropylene ; Silisyum karbür = Silicon carbide

Özet:
Bu çalışmada, başta toz metalurjisi olmak üzere farklı mühendislik uygulamalarda potansiyel kullanım alanları bulabilecek polipropilen matrisli ve silisyum karbür katkılı fiber formda kompozit numunelerin üretilmesi ve söz konusu numunelerin farklı polipropilen türleri, ağırlıkça çeşitli oranlarda SiC takviyesi ve fiber numune boyu gibi parametrelere göre preslenebilirlik özellikleri ele alınmış ve kıyaslanmıştır.
Numunelerin üretilebilmesi için erime akış hızı belirgin farklılık gösteren 3 farklı polipropilen malzeme kompozit matris malzemesi olarak seçilmiş, takviye malzemesi olarak ise siyah silisyum karbür tozu kullanılmış olup, her bir numune için ağırlıkça %0, %1, %3 ve %5 olmak üzere 4 farklı oranda takviye yapılarak 12 farklı karışım elde edilmiştir. Numuneler fiber formu kazandırılmak üzere laboratuvar tipi ekstrüderde işlenmiş ve optimum özelliklerin belirlenmesi için rotor sıcaklığı, ekstrüder çıkış sıcaklığı ve makara sarma hızı gibi parametreler, bu kapsamda çalışılmıştır. Elde edilen numunelerin fiziksel özelliklerinin tespiti için yoğunluk değerleri He gaz piknometresi ile ölçülmüş olup, XRD ve FTIR teknikleri kullanılarak nunumeler içindeki PP matrisin ve SiC toz partiküllerinin yapıları tespit edilerek karakterize edilmiştir.
Ekstrüderde işleme sonrası elde edilen 12 farklı fiber formunda polimer matrisli kompozit numunenin her biri, 0-3 mm ve 3-5 mm olmak üzere iki farklı boyda kesilmiş ve bu sayede kısa elyaf yapısı kazandırılarak 24 farklı numune elde edilmiştir.
Çalışmada, 24 farklı numunenin her biri, laboratuvar tipi pres cihazında 500 kg-f yük altında, 0,4 mm kare kesitli kalıp içerisinde preslenerek, anlık gerilme değerine karşılık gelen anlık rölatif yoğunluk değerlerinden presleme grafikleri elde edilmiştir. Rölatif yoğunluk değerleri; presleme esnasında anlık olarak hesaplanan yoğunluk değerlerinin, polipropilen matrisli kompozit numunelerin teorik yoğunluğuna oranlanması ile bulunmuştur.
Presleme grafiklerinin karşılaştırılması ve yoğunluk değerlerinin yorumlanması ile, fiber formda polipropilen matrisli kompozit malzemenin üretilmesi için, polimer erime akış hızı parametresinin ekstrüderde gerçekleştirilen işleme etkisi tartışılmıştır.
Çalışmada, artan takviye oranı ve numune elyaf boyu değişkenlerinin, presleme esnasında numunenin sıkıştırılabilirlik özelliğine etkisi yorumlanmıştır.

Abstract:
In this study, the production of composite samples in fiber form with polypropylene Composite materials are materials that consist of two or more different materials and gain new properties by taking advantage of the superior properties of the materials that make up them. In nature, materials such as coconut tree leaves and wood are examples of natural composites; Industrial use of composite materials has become widespread with the production of high-performance composites and their use in areas such as automotive, aviation, automotive, transportation, defense industry, construction, architecture, electrical-electronics, maritime, petroleum industry, health sector.
In this study, the extrusion of composite samples with polypropylene matrix and silicon carbide reinforced fiber in order to evaluate its potential in fields such as engineering applications and powder metallurgy, and the compressibility properties of these samples according to parameters such as different polypropylene types, SiC reinforcement at various weights and fiber sample size were discussed. and compared. The samples were subjected to characterization methods such as X-Ray Diffractometry (XRD), Fourier Transform Infrared Spectroscopy (FT-IR) before pressing, and density measurement was also made in a gas pycnometer and stereo microscope images were obtained for the determination of sample fiber lengths.
In order to produce the samples, first of all, 3 different types of polypropylene materials, EH102, EH251 and MH180, which have markedly different melt flow rates, were chosen as matrix materials. For the fibers to be produced by extrusion, the extruder parameters have been optimized considering the physical properties of polypropylene materials in the literature. For the optimization process, plain polypropylene material without reinforcement was used; parameters such as rotor temperature, melting pot temperature and reel winding speed were determined based on the physical properties of plain polypropylene. As a result of the optimization, the melting pot temperature for the extruder was chosen as 175°C and the rotor outlet temperature as 185°C. 12 Rpm value is optimized for the exit speed of the polypropylene coming out of the extruder from the rotor in molten state. The molten polypropylene coming out of the extruder rotor is simultaneously wound onto the extruder reel, which serves to continuously wrap the melt coming out of the extruder device, and fibers with optimized values are obtained.
In the study, samples were prepared to produce silicon carbide reinforced polypropylene fiber with the extruder device optimized by extrusion of plain polypropylene materials. For this reason, it is aimed to prepare four different mixtures for each polypropylene type: plain, containing 1% silicon carbide by weight, 3% silicon carbide by weight, and finally 5% silicon carbide by weight. The mixtures were prepared by adding silicon carbide to polypropylene materials and it was aimed to increase the homogeneity of the mixture by melting the polymer at 200°C in the oven and adding reinforcement silicon carbide and mixing it periodically.
In this study, 3 different types of polypropylene composite samples containing 4 different weight ratios of silicon carbide reinforcement were prepared to be fed into the extruder crucible. The 12 samples obtained were extruded to give fiber form, and optimized extruder parameters were used to perform the extrusion process properly. The values obtained from the pycnometric measurement made to find the density values of the composite samples, which were turned into fibers by extrusion, and the X-Ray Diffractometry graphics made to examine the sample crystallography were evaluated. The X-Ray Diffractometry graphs obtained for each of the 12 samples show the increasing weight of silicon carbide in the samples, with peaks increasing in intensity between 30-45 degrees, together with the increasing weight-by-weight ratio of silicon carbide in the samples. In addition, Fourier Transform Infrared Spectroscopy was applied to the samples in order to examine the composition of the samples and graphs characterized by polypropylene material were obtained.
Each of the 12 different composition fiber polymer matrix composite samples obtained after the extrusion process was cut in two different lengths, 0-3 mm and 3-5 mm, and thus 24 different samples were obtained by gaining short fiber structure. The images of the samples were obtained with a stereo microscope, and the difference in length of the samples was shown.
In the study, each of the composite samples in the form of 24 different short fibers were pressed in a square mold with a cross section of 0.4 mm under a load of 500 kg-f in a laboratory type press device. Pressing graphs were obtained by calculating the instantaneous relative density values corresponding to the instantaneous stress value until the press device reaches 500 kg-f. Relative density values; It was found by proportioning the instantaneous calculated density values during pressing to the theoretical density of the produced polypropylene matrix composite samples. The obtained pressing graphics were compared according to the criteria of polypropylene type, silicon carbide reinforcement ratio and sample fiber length. In addition, the reasons for the differences were evaluated by comparing the values measured with the gas pycnometer with the theoretical density and relative density.
The distances between the polymer chains of the produced fibers due to the production processes; There is a high difference between the calculated theoretical densities and the measured densities due to reasons such as microvoids that may exist between the reinforcement and the matrix. The deviations between the calculated theoretical densities of the composite fibers and the pycnometric density measurements are of the order of 5% at most for most samples. Considering the principles of the pycnometric density measurement technique, this indicates that the fibers are produced as desired. This does not apply to the composite sample containing MH180 – 5% by weight SiC reinforcement. This is due to the low melt flow rate of the MH180 composite. Comparing the pressing graphics and interpreting the density values, it is seen that as the melt flow rate of the polypropylene, which forms the matrix of the fiber-formed polypropylene matrix composite material, becomes more difficult to flow in the extrusion die, it affects the increasing density difference.
The highest differences (>4%) between the theoretical and pycnometric density values are seen in all 5% SiC reinforced composite fibers and MH180 – composite samples containing 3% SiC by weight. In 5% by weight SiC reinforced composites, it is difficult for the polymer matrix to flow around the solid reinforcements in the extrusion die, which may be the reason for this situation.
In the study, the effect of the sample fiber length variable on the compressibility of the sample during pressing was interpreted. Short fibers were found to have lower compressibility; this is as expected due to the stiffness property of short length fibers.