Santrifüj eğirme yöntemiyle nanolif yapılı dokusuz kumaş üretiminin optimizasyon çalışmaları ve filtrasyon özellikleri
Production and optimization of nanofibrous nonwoven webs via centrifugal spinning and their filtration properties
Yazar: MUSTAFA KURTULUŞ
Danışman: PROF. DR. ŞAFAK YILMAZ ; YRD. DOÇ. ALİ KILIÇ
İstanbul Teknik Üniversitesi / Fen Bilimleri Enstitüsü / Makine Mühendisliği Ana Bilim Dalı / Malzeme ve İmalat Bilim Dalı
Derece: Yüksek Lisans, 2015
Konu: Makine Mühendisliği = Mechanical Engineering

Özet:
Nanolifli yapılar çok küçük gözenekli yapıları, yüksek yüzey alanları gibi
özelliklerden dolayı tekstil, kompozit ve enerji uygulamalarında önemli bir yer
tutmaktadır [1–5]. Günümüzde nanolif üretiminde kullanılan ve üzerinde en çok
araştırma yapılan geleneksel yöntem elektroüretim yöntemidir [6]. Ancak yöntemin 
düşük üretim hızı ve yüksek voltaj gerektirmesi gibi gerekçeler yüzünden endüstride
kullanımı kısıtlıdır. Eriyikten üfleme yöntemi yüksek üretim hızına müsait olmasına
rağmen, nano seviyede lif üretimi konusunda sınırlı olduğundan ve yüksek
sıcaklıklarda hava kullanımı gerektirdiğinden dezavantajlıdır [7]. Çözeltiden üfleme
yöntemi sadece polimer derişiminin miktarına bağlı olarak çözeltilerle çalışabiliyor
oluşundan ötürü kısıtlıdır [8]. Diğer yöntemler olan çift bileşenli lif eğirme, faz
ayrıştırma, kalıba sentezleme ve kendinden bağlı yöntemlerin de malzeme ve
işleyişlerinden dolayı kısıtlamalar içermesi akademik ve endüstriyel çevreleri yeni
bir yöntem arayışına itmiştir.  Mevcut yöntemlerin kısıtlarını ortadan kaldıracak bir
yöntemin varlığı endüstri ve akademik çevreler için önemli bir gelişme olacaktır.
Santrifüj eğirme yöntemi kurulumu ve çalıştırılması basit, üretim hızının diğer
yöntemlere nazaran yüksek oluşu gibi özellikleriyle nanolif üretiminde önemli bir
alternatif üretim yöntemidir. 
Bu tez çalışmasında geleneksel lif üretim tekniklerine göre yüksek üretim hızı ve
nispeten düşük maliyetiyle öne çıkan santrifüj eğirme yönteminin optimizasyon
çalışmaları ve bu yöntemin kullanılmasıyla üretilen nanolif yapılı dokusuz
kumaşların filtrasyon özellikleri araştırılmıştır.  
İlk aşamada santrifüj eğirme sistemi için gerekli makina-teçhizat tasarımı ve imalatı
yapılmıştır. Sistemin tasarım aşamasında çeşitli CAD programları kullanılarak katı
modellemeler ve imalatı için uygun teknik resimler oluşturulmuştur. Deney düzeneği
kurularak nano ölçekli lifler ile dokusuz kumaş yapıları elde edilmiştir. Çeşitli sistem 
parametreleri uygulanarak, değişikliklerin lif yapısı üzerindeki etkisi incelenmiş,
optimum parametrelere ulaşılması hedeflenmiştir. Çalışmada dokusuz kumaş üretimi
için termoplastik poliüretan (TPU) içeren çözeltiler kullanılmıştır. 
İkinci aşamada optimum parametreler kullanılarak dokusuz kumaş numuneleri elde
edilmiş ve bunların hava ve su geçirgenlik özellikleri ile su filtrasyon performansları
incelenmiştir. Bu yenilikçi yöntem ile yapılan çalışmalar neticesinde hava ve su
filtreleri üretilebileceği görülmüştür.

Abstract:
Nanofibrous nonwovens are important enginering materials in textile, composite and
energy sectors because of their low fiber diameter, micro- nano porous structure and
high surface area to volume [1–5]. Electrospinning is the most widely used
traditional method for the production of nanofibers [6]. Low production rate and high
voltage requirement are drawbacks of electrospinning, limiting its industrial
scalability. Although meltblowing might be a productive alternative, it is not easy to
produce nano scale fibers. Also, it requires compressed hot air and applicable to
limited number of materials [7]. Solution blowing might be an alternative where the
disdvantage is related its dependency on solution concentration [8].  
As an alternative centrifugal spinning has many important advantages over the other
nanofiber production methods such as simple working principle, availability to
produce fibers from polymer melts and solutions, independency from high voltage,
high production rate, and low cost. Also, this method is suitable for processing
polymeric and ceramic nanofibers. The diameter and morphology of the fibers are
dependent on solution viscosity, surface tension, molecular structure, molecular
weight, concentration while rotational speed of and diameter of the rotor, nozzle
diameter and working distance between rotor and collector are process parameters.  
In this study, effective system, process and material parameters of centrifugal
spinning were investigated. Moreover filtration properties of centrifugally spun
nonwoven webs were analyzed. After a short review on recent literature, a proper
spinning system was designed  and manufactured using some CAD programmes to
make solid models and related technical drawings. An aluminum rotor with 50 ml
volume and 220 g weight was used, where a 2.2 kw (3 hp) spindle motor was
selected as driving force for the rotor. The spindle has 18000 rpm rotational capasity,
but maximum speed was kept 10000 rpm because of safety precautions. 
Nozzle diamater was seen to be critical on the morphology of fibers. Different type
of nozzles with 0.3, 0.5 and 1.0 μm diameter were designed and manufactured to be
used in this study.  
In the literature several types of collection systems were mentioned for centrifugal
spinning. In my study a steel mesh conveyor was used to collect the fibers. A
vacuum manifold was used just behind the conveyor to make the collection more
effective.  
Nanofibers and nanofibrous nonwoven webs were produced with experimental
centrifugal spinning setup in Mechanical Engineering Laboratories of ITU. Firstly,
effect of solution concentration was examined. A critical viscosity value must be
achieved to obtain fibers continuously.  The fiber production was not successful from
solutions at 5wt.% and 10wt.% concentration, while 15wt.% and 20wt.%
concentrations were suitable to produce fibers. Average fiber diameter also increased
slightly with the increasing concentration of polymer solution. Besides ethyl acetate
was added to solution to improve the vapor pressure of the solvent. The results
showed that additive addition reduces droplet concentration on webs. In addition, the
increase in the additive amount increased the average fiber diameter slightly. Effect
of rotational speed was also investigated to see how it changes the fiber production.
Between 3000 and 6000 rpm, the increase in rotational speed increased the fiber
diameter significantly, because polymer solution feeding amount also increased.
Comparing 6000 and 9000 rpm rotational speeds, it was seen that average fiber
diameter decreased within that values which is thought to be due the fact that 
centrifugal forces are more effective than polymer solution flow rate, which
attenuates the fibers effectively at high rotational speeds. 
3 types of nozzles were examined in this study. Generally, average fiber diameter of
produced nonwoven webs with 0.3 and 0.5 mm diameter nozzles were found to be
same. When 1 mm diameter nozzle was used, it was seen that fiber diameter was
increased notably. Finally, effect of the working distance between nozzle and
collector was investigated after spinning from 2 distances. It was seen that working
distance doesn‟t have a significant effect on fiber diameter.  
After optimization of various process, material and system parameters nanofibrous
nonwoven webs were produced according to investigated parameters. Air 
permeability, water flux, pressure and particle retention efficiency of produced
samples were investigated according to standards.  
To investigate filtration and barrier properties initially air permeability of
polypropylene (PP) spunbond nonwoven was measured which is the standart
substrate we used throughout the study. Same spunbond nonwovens was used as a
support material since nanofibers are not strong enough to resist huge pressures
during tests. Nanofiber production was optimized with following parameters: 9000
rpm rotational speed, 0.3 mm nozzle diameter, 30 cm nozzle-collector distance, 1
hour duration. It was seen that the air permeability decreased nearly 70% after
nanofiber coating. The average fiber diameter should be further minimized to reach
slip flow regime, where air molecules slip over the fibers due to low Knudsen
number. This will improve potential of those nonwovens to be used in air filtration
applications. 
Later on, water permeability tests were performed where water flux through
nanofiber coated samples and normal spunbond nonwovens were determined at
various pressure values. Water filtration tests were conducted under 0.9 psi pressure
for nanofiber coated and normal nonwoven webs. The standard PS latex particles
were added to distiled water. For 1, 5 and 10 µm particles containing water samples
it was seen that water flux values were decreased because of retention of particles
around fibers. It was seen that samples have similar water permeability with same
pressures. Water flux through nanofiber coated sample became easier, because of
hydrophilic property of TPU material and lower solidity of centrifugal spining
compared to electrospinning. Contaminated and filtered water were tested using 
particle counter device to see the effect of nanofibrous layer on water filtration.
According to results normal spunbond nonwoven has poor performance for 1 and 5
µm particles, while it has 60% filtration efficiency for 10 µm particles. Nanofibrous
coated web has 70% filtration efficiency for 1 µm particles. For 5 and 10 µm
particles, it has filtration efficiency more than 90%. These values shows that
nanofibrous webs can be alternative for  water filtration applications.  
It is clearly seen that centrifugal spinning method has a big potential to be a powerful
system for fiber production in nanoscale. In addition to this, the researches on this
method will increase to proof that these fibers can be used for many applications,
especially in filtration area.