Styrenation of triglyceride oil through controlled / living free radical polymerization

Bu çalışmada, kontrollü/yaşayan radikal polimerizasyon tekniklerinden biri olan tersinir katılma –bölüşme zincir transfer polimerizasyon (reversible addition – fragmentation chain transfer polymerization - RAFT) tekniği kullanılarak hava üflenmiş keten yağının stirenlenmesi gerçekleştirilmiştir. RAFT ajanı (Zincir transfer ajanı) olarak Fenasil Morfolin Ditiokarbamat (PMDC) kullanılmıştır ve polimerizasyonda uygun miktarı belirlenmiştir. RAFT ajanı miktarı, peroksit gruplarının oluşturacağı serbest radikaller esas alınarak hesaplanmıştır. Polimerizasyonda, değişen miktarlarda PMDC kullanılarak, miktarın ürün özellikleri üzerine etkisi incelenmiştir. Elde edilen sonuçlara göre, ortamda oluşan serbest radikallere ekivalent miktarda PMDC kullanıldığında polimerizasyonun kontrol edilebildiği ve dar molekül ağırlığı dağılımının sağlandığı görülmüştür. Ekivalent miktardan daha fazla PMDC kullanıldığında ise polidispersitenin daha da düştüğü gözlenmiştir. Elde edilen stirenlenmiş yağ örnekleri GPC ve FT-IR analizleri ile karakterize edilmiştir. Sonuç olarak RAFT polimerizasyon tekniği kullanılarak, polidispersitesi düşük (<1.5) ürünler elde edilmiştir. Bu yöntem ile elde edilen ürünlerin, klasik yöntemin tersine, homopolimer içermedikleri çapraz bağlı filmler üzerinden yapılan test ile anlaşılmıştır. Ayrıca elde edilen ürünlerin film özellikleri, ilgili standartlara göre incelenmiş ve klasik yöntem ile elde edilen ürünün film özellikleri ile karşılaştırılmıştır. Karşılaştırma sonucunda, RAFT tekniği kullanılarak elde edilen ürünlerin, klasik yöntem ile üretilene göre suya ve baza karşı daha dayanıklı oldukları ve kuruma süresinin daha kısa olduğu görülmüştür. Filmin daha kısa sürede kuruması yüzey kaplama endüstrisinde istenilen bir özelliktir. Ayrıca bu ürünlerin yapışma özelliği de klasik yöntem örneğine göre daha iyi çıkmıştır.  Anahtar Kelimeler: Stirenlenmiş yağ, kontrollü/yaşayan polimerizasyon, RAFT.Triglyceride oils owe their value as raw materials for decorative and protective coatings to their ability to polymerize and cross-link or dry after they have been applied to a surface, to form tough, adherent films. In order to obtain coating material having better performance in industry, oils are modified with various methods. Among these modified methods, copolymerization of oils with vinyl monomers such as styrene occupies an important place. In the classical styrenation process, homopolystyrene formation is likely to occur. The formation of homopolystyrene is not favor in product since the presence of homopolymer leads to weak film properties. By taking this fact into account, the methods by which homopolymerization was minimized and polymer structure was controlled, were previously developed in our laboratory. As a continuation of these studies, in this study, in order to obtain styrenated oil, air blowing linseed oil was copolymerized with styrene by the controlled / living radical polymerization technique (CLRP). CLRP is particularly appealing as it not only delivers polymers having a narrow molecular weight distribution with predetermined average molecular weight but also can be performed using normal radical procedures without the stringent experimental conditions required in living ionic polymerization. The most widely used controlled radical polymerization techniques are reversible addition fragmentation chain transfer polymerization (RAFT), nitroxide mediated polymerization (NMRP) and atom transfer radical polymerization (ATRP). Among of these techniques,  the RAFT polymerization has been considered a the most versatile and robust method, since it can be compatible with almost all monomers and reactions conditions that are applicable to conventional free radical polymerization. The RAFT process and its benefits are achieved simply by the addition of a suitable RAFT agent to the reaction medium. In this work, styrenated oil was obtained in three step. In the first step, the air was passed out through preheated linseed oil for 18 hours at 80 0C, thus, the peroxide groups on the oil triglyceride molecules created. Polymerization of oils is provided due to free radicals resulting in their decomposition. Peroxide value of oil was determined as 485 meq peroxide - oxygen/kg oil. In the second step, phenacyl morpholine dithiocarbamate (PMDC) was prepared in laboratory and used as RAFT agent, R and Z being phenacyl and morpholine, respectively. The structures of R and Z of the RAFT agent would exist in the chain ends of the final polymers. Thus, the end group of the polymer can be predesigned by choosing the RAFT agent with the desired structures. In the third step, air blown linseed oil was styrenated in the presence of PMDC under nitrogen atmosphere at 90 0 C. Temperature was kept constant with controlled heating. In order to investigate the effect of the RAFT agent amount on the copolymer, different amounts of the RAFT agent were used in the reaction. The characteristic properties of the samples such as molecular weight, polydispersity and molecular structure were determined by Gel Permeation Chromatography (GPC). The results show that, in the RAFT polymerization technique, when RAFT agent was used in the equivalent amount to the free radicals, products with low polydispersity were obtained while without homopolystyrene formation. Also when the amount of RAFT agent was excess than that of the equivalent to the free radicals, polydispersity became lower. In addition to these, polymer with higher molecular weight and higher conversion were obtained with increasing reaction time and polydispersity was still at low level.  For all that, three peaks were observed in GPC chromatograms. This is the expected result since the hydroperoxides decompose to give free radicals under blowing conditions. As a result this fact, chain propagation by coupling and abstraction reactions cause different molecular weight and ultimately leads to deviation from the unimodel shape. Besides, the oil-styrene copolymer structure was assigned by means of FT - IR measurements. The FT - IR spectrum of styrenated oil showed the characteristic bands of both styrene and initial oil segment. The film properties of the resulting sample was determined according to related standards as well. Copolymer of the oil with styrene was also prepared by conventional method and this sample were used as a comparative sample. The sample obtained with RAFT polymerization technique showed better alkali and water resistance and better adhesion and the shorter drying time than the classical sample which obtained in the absence of the RAFT agent..  Keywords: Styrenated oil, controlled/living polymerization, RAFT

Simplified Earthquake Analysis of Suspensi

This paper presents the finite element analysis of a suspension bridge subjected to earthquake ground motion using simplified models. For this purpose, two simplified models are considered. It is assumed that each element compose of the deck, cable and hangers in the first model. As second model, the elastic foundation analogy method is used. Also, actual bridge model is selected. Finite element earthquake analyses of the simplified and real bridge models are performed. One of the world's longest modern type suspension bridges, Fatih Sultan Mehmet Bridge, is selected as a numerical example. As ground motions, Kocaeli earthquake occurred on August 17, 1999 in Kocaeli, Turkey is chosen since it took place at the vicinity of the bridge. The response values obtained from simplified and actual bridge models are compared with each other

Preparation of cellulose nanofibers with hydrophobic surface characteristics.

The aim of this study was to develop cellulose nanofibers with hydrophobic surface characteristics using chemical modification. Kenaf fibers were modified using acetic anhydride and cellulose nanofibers were isolated from the acetylated kenaf using mechanical isolation methods. Fourier transform infrared spectroscopy (FTIR) indicated acetylation of the hydroxyl groups of cellulose. The study of the dispersion demonstrated that acetylated cellulose nanofibers formed stable, well-dispersed suspensions in both acetone and ethanol. The contact angle measurements showed that the surface characteristics of nanofibers were changed from hydrophilic to more hydrophobic when acetylated. The microscopy study showed that the acetylation caused a swelling of the kenaf fiber cell wall and that the diameters of isolated nanofibers were between 5 and 50 nm. X-ray analysis showed that the acetylation process reduced the crystallinity of the fibers, whereas mechanical isolation increased it. The method used provides a novel processing route for producing cellulose nanofibers with hydrophobic surfaces

Anomaly detection in elderly daily behavior in ambient sensing environments

Current ubiquitous computing applications for smart homes aim to enhance people’s daily living respecting age span. Among the target groups of people, elderly are a population eager for “choices for living arrangements”, which would allow them to continue living in their homes but at the same time provide the health care they need. Given the growing elderly population, there is a need for statistical models able to capture the recurring patterns of daily activity life and reason based on this information. We present an analysis of real-life sensor data collected from 40 different households of elderly people, using motion, door and pressure sensors. Our objective is to automatically observe and model the daily behavior of the elderly and detect anomalies that could occur in the sensor data. For this purpose, we first introduce an abstraction layer to create a common ground for home sensor configurations. Next, we build a probabilistic spatio-temporal model to summarize daily behavior. Anomalies are then defined as significant changes from the learned behavioral model and detected using a cross-entropy measure. We have compared the detected anomalies with manually collected annotations and the results show that the presented approach is able to detect significant behavioral changes of the elderly

Brain function assessment in different conscious states

Background: The study of brain functioning is a major challenge in neuroscience fields as human brain has a dynamic and ever changing information processing. Case is worsened with conditions where brain undergoes major changes in so-called different conscious states. Even though the exact definition of consciousness is a hard one, there are certain conditions where the descriptions have reached a consensus. The sleep and the anesthesia are different conditions which are separable from each other and also from wakefulness. The aim of our group has been to tackle the issue of brain functioning with setting up similar research conditions for these three conscious states.Methods: In order to achieve this goal we have designed an auditory stimulation battery with changing conditions to be recorded during a 40 channel EEG polygraph (Nuamps) session. The stimuli (modified mismatch, auditory evoked etc.) have been administered both in the operation room and the sleep lab via Embedded Interactive Stimulus Unit which was developed in our lab. The overall study has provided some results for three domains of consciousness. In order to be able to monitor the changes we have incorporated Bispectral Index Monitoring to both sleep and anesthesia conditions.Results: The first stage results have provided a basic understanding in these altered states such that auditory stimuli have been successfully processed in both light and deep sleep stages. The anesthesia provides a sudden change in brain responsiveness; therefore a dosage dependent anesthetic administration has proved to be useful. The auditory processing was exemplified targeting N1 wave, with a thorough analysis from spectrogram to sLORETA. The frequency components were observed to be shifting throughout the stages. The propofol administration and the deeper sleep stages both resulted in the decreasing of N1 component. The sLORETA revealed similar activity at BA7 in sleep (BIS 70) and target propofol concentration of 1.2 μg/mL.Conclusions: The current study utilized similar stimulation and recording system and incorporated BIS dependent values to validate a common approach to sleep and anesthesia. Accordingly the brain has a complex behavior pattern, dynamically changing its responsiveness in accordance with stimulations and states. © 2010 Ozgoren et al; licensee BioMed Central Ltd