IBN AL- HAITHAM J. FOR PURE & APPL. SCI. VOL.24 (1) 2011 An FTIR Study of Characterization of Neat and UV Stabilized Nylon 6,6 Polymer Films H. A. Mahdi Department of Physics , College of Education Ibn Al-Haitham, University of Baghdad Received in August 22 2010 Accepted in Nev. 9 2010 Abstract The work is concerned with the characterization of as cast films of neat and UV-stabilized nylon 6,6 by employing FTIR measurements. Band assignment is made for neat and UV- stabilized nylon 6,6 using FTIR spectra confirm their molecular structure. UV-stabilizer added to nylon 6,6 has caused reduction in the absorbance of the vibrational bands and thus stabilizes the behavior of the polymer in the end and uses specially in harsh environment. Keywords: Nylon 6,6, UV-stabilizer, FTIR spectra. Introduction Polymer characterization is an essential step in working with polymers. The main characterization techniques involve the use of Fourier transform infrared and x-ray diffraction methods. As a rule, such efforts are directed toward a specific purpose. The structure and molecular conformation of the macromolecules ultimately determine the mechanical, physical and chemical properties of polymers [1]. Thus precise characterization of molecular order is a primary prerequist to understandand macroscopic properties of polymeric materials [2,3]. Nylon is a generic designation for a family of synthetic polymers known as polyamides (PA), and nylon 6,6 is one of the most important engineering thermoplastics often used in adverse environment. The nature of the chemical repeat unit (presented in figure 1) pose the polymer in many industrial applications such as nylon fibers for carpeting, clothing, tire cord and solid nylon for bearings and gears due to its good abrasion resistance and self-lubricating properties and nylon ribbons for tying cables due to its good creep modulus [4]. The polymer is synthesized by condensation polymerization of hexamethylenediamine and adipic acid. It is semi-crystalline and the crystals melt at high temperature. In spite of its superior properties, nylon 6,6 is very sensitive to moisture absorption and moisture content must be controlled during melt processing of nylon 6,6 [5]. The aim of the present work is directed in the key points of characterization of polymers employing FTIR technique. Experimental Ribbons of nylon 6,6 were obtained from local market. The ribbons were dissolved in a mixture of 1:1 weight ratio of formic acid and phenol at ambient temperature. The mixture was cast into a glass mold and left to dry at ambient temperature. The cast nylon films were peeled from the mold and the FTIR spectra have been recorded in the range 400-4000 cm -1 using shimadzu 8400 series at Ibn-Sina chemical industrial center. The standard samples were IBN AL- HAITHAM J. FOR PURE & APPL. SCI. VOL.24 (1) 2011 made by mixing finely chopped polymer with KBr and compressing the mixture in a pellet- making press. The KBr discs with polymer were placed in the FTIR cell and the spectra were recorded. The FTIR spectrum is a useful tool to identify the chemical nature of the polymer and to determine its composition. Results and Discussion FTIR spectroscopy has been applied in the identification of the basic structural units of nylon 6,6 and UV stabilized nylon 6,6. The FTIR spectra of the two types of polymers are presented in figures 2 and 3. Band positions in the spectra are utilized in confirming the molecular structure of the polymer [6,7]. Absorbance was calculated as: Abs = log T = log (I/Io) where T is the transmittance and I/Io is the relative intensities of sample and standard respectively. The vibrational frequencies of all the fundamental bands along with their relative intensities and probable assignments are given in tables 1 and 2 for both the neat and UV stabilized nylon 6,6. Comparison of the frequency bands of nylon 6,6 with the reference nylon 6,6 [8] confirm that the cast neat films are those for nylon 6,6 with band shifts not exceeding ± 5 cm -1 . This is characterized by the major band: the amide bands at 1639 and 1539 cm -1 and N-H, CH2 (a symmetric stretching) and CH2 (symmetric stretching) at 3306, 2932 and 2862 cm-1 respectively. These bands are indicative of their high absorbance (see table 1). For the UV stabilized cast nylon 6,6 films however, the amide bands have shifted from those of the neat nylon 6,6 sample by about 20 cm -1 due to the effect of UV stabilizer. It is also noted from the absorbance results in table 2 that the UV stabilized materials tend to reduce the absorbance of all the bands assigned a consequence that characterization is useful in identifying the chemical nature of the polymer. Conclusion The characterization study on neat and UV-stabilized nylon 6,6 has been carried out using important experimental technique. Their molecular structures were confirmed by FTIR spectra from assignment of absorbance bands. Once the molecular structure is understood, it becomes easy for a polymer scientist to relate the polymer structure to its performance properties in end use. References 1.Sandler, S; Karo, W; Bonesteel, J and Pearce, E.M. (1998) ,Polymer synthesis and characterization: A laboratory manual, Academic press, Finland. 2. Carraher, C. (2003), polymer chemistry 6th ed. Dekker, New York. 3.Bicerano, J. (2002) ,Prediction of polymer properties”, Dekker, New York. 4. Modern Plastic Encyclopedia Handbook, (1994) McGraw hill, New York. 5. Melvin, I. Kohan, (1973) ,Nylon plastics” John Wily and Sons, USA. IBN AL- HAITHAM J. FOR PURE & APPL. SCI. VOL.24 (1) 2011 6.Nakamoto, K. (1997) ,Infra red and Rawan spectra of inorganic and coordination compound, 5th ed., John Wiley and Sons, New York. 7. Charles, J.; Ramkumar, G.R.; Azhagiri, S. and Gunase Karan (2009) ,FTIR and thermal studies on nylon 6,6 and 30% glass fiber reinforced nylon 6,6, E-Journal of chemistry, 6(1): 23-33. 8.Dongwood ,Jung (2004) ,New methods for producing nylon 6,6 fibers with enhanced mechanical properties, Ph.D thesis, North Carolina state University, USA. Table (1): Assignment of FTIR spectrum of neat nylon 6,6 Wave number (cm-1) Absorbance Assignment 3410 3306 3082 2932 2862 1639 1539 1469 1269 1200 934 691 579 0.34 0.38 0.18 0.28 0.25 0.53 0.46 0.31 0.34 0.29 0.17 0.20 0.18 N-H stretching I N-H stretching II C-H stretching (asym) CH2 stretching (asym) CH2 stretching (sym) Amide I stretching Amide II stretching/ CH2 (asy)(mdef) N-H deformation/ CH2 scissoring Amide III stretching CCH bending (sym)/ CH2 twisting C-C stretching C-C bending C-C deformation Table (2) :Assignment of FTIR spectrum of UV stabilized nylon 6,6 Wave number (cm-1) Absorbance Assignment 3414 3240 2928 2855 1686 1612 1516 1431 1304 1261 1173 1122 1018 922 667 575 0.28 0.14 0.09 0.08 0.19 0.22 0.14 0.15 0.17 0.19 0.16 0.15 0.15 0.05 0.08 0.06 N-H stretching I N-H stretching II CH2 stretching (asym) CH2 stretching (sym) Amide I stretching CH2 deformation (asym) Amide II stretching N-H deformation CH2 wagging Amide III stretching CH2 twisting C-C stretching (sym) C-C stretching C-C stretching C-C bending C-C deformation IBN AL- HAITHAM J. FOR PURE & APPL. SCI. VOL.24 (1) 2011 Fig.( 1): Chemical structure of nylon 6,6 Fig.( 2): FTIR spectrum of neat nylon 6,6 Fig. (3): FTIR spectrum of UV-stabilized nylon 6,6 2011) 1( 24المجلد مجلة ابن الهیثم للعلوم الصرفة والتطبیقیة النظیفة والمستقرة لالشعة فوق 6,6لتشخیص افالم بولیمر نایلون FTIRدراسة البنفسجیة مهدي هند عبدالمجید ابن الهیثم ، جامعة بغداد- قسم الفیزیاء ، كلیة التربیة 2010 اب 22 في استلم البحث 2010 تشرین الثاني 9 في قبل البحث الخالصة ت 6,6 للنایلون یعني العمل بتشخیص افالم مصبوبة النظیفة والمستقرة لالشعة فوق البنفسجیة باستخدام قیاسا النظیف والمستقر لالشعة فوق 6,6تم عمل تعین الحزم لكال من النایلون . FTIRر لالشعة تحت الحمراء فوریتحویل تبین ان اضافة المواد المستقرة لالشعة فوق . التي ثبتت التركیب الجزیئي للبولیمر FTIRالبنفسجیة باستعمال اطیاف د 6,6البنفسجیة إلى النایلون یؤدي إلى نقصان في امتصاصیة حزم االهتزاز وبذلك تؤدي إلى استقرار سلوك البولیمر عن .في البیئات القاسیة یماالساالستخدام