Preparation of nitrile rubber by emulsion polymerization method and checking its properties

Number of pages: 139 File Format: word File Code: 31883
Year: 2013 University Degree: Master's degree Category: Chemical - Petrochemical Engineering
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    Master's thesis in the field of polymerization engineering

    Abstract

    Using experimental design methods, the optimal feed recipe for the preparation of nitrile rubber was determined. Initially, to determine the factors affecting the rate of polymerization, screening tests were designed according to the Plate-Boormann method, which examines a large number of factors with a small number of tests. Based on this, 9 factors were planned in the form of 12 experiments at two levels in order to determine the effective factors on the reaction conversion percentage. The results indicated that potassium concentration has the most significant effect on the conversion percentage after 8 hours. Temperature, iron (II) sulfate concentration were the factors that increased the conversion percentage in 8 hours, but their effects were not significant. In order to know the interactions between the components of the initiator system and with the help of the results obtained from the Plate-Boorman screening method, another group of experiments was designed based on the all-factor statistical method. In the all-factor method, 4 factors were designed in two levels and in the form of 16 experiments. The implementation of 16 experiments determined that the concentration of the reducing agent (sodium formaldehyde sulfoxylate) in the starting oxidation-reduction system significantly increases the conversion percentage after 4, 6 and 8 hours. Other factors and the interaction between them had no significant effect on the conversion percentage. In addition to the conversion percentage, the Mooney viscosity of the synthesized nitrile rubber was a parameter based on which the optimal feed recipe was determined. Examining the size of the latex particles of the optimal sample by DLS test showed that the particle size is in a smaller range than common emulsion polymerizations, which is a confirmation of the homogeneous nucleation mechanism due to the high resolution of acrylonitrile in the water phase. The DSC test for the optimal sample showed that the structure of the copolymer has almost good uniformity so that only one Tg was observed for the sample. Also, the 1H-NMR test on the optimal sample showed the proper distribution of comonomers in the chain structure. In addition, the elemental analysis test (CHNS) showed that the percentage of acrylonitrile in the copolymer increases from the beginning of the reaction to the conversion percentage of about 35%, and from then on, this value remains constant in the expected range of 33 to 34% of acrylonitrile. This event confirms the high resolution of acrylonitrile in the water phase. Examining the sequence of monomer triplets during polymerization using 1H-NMR showed that the percentage of AAB triplets gradually decreases during polymerization, while the percentage of BBB triplets increases. Also, experiments with a single variable factor were performed and the results indicated that the amount of emulsifier reduces the size of the particles, and it was observed that the temperature has no effect on the amount of gel. Also, Mooney's viscosity showed that the amount of chain transfer agent has a direct effect on reducing the molecular weight. In the end, the physical and mechanical properties, including tensile test, hardness, compressive strength and springiness, showed that the prepared nitrile rubber offers favorable physical and mechanical properties for general applications. Besides, by comparing the results of Mooney viscosity and tensile test, it was found that the molecular mass has a direct relationship with the tensile strength.

     

     

    1-      Chapter One: Introduction

    1-1-     History

    In 1926, seven years after the production of methyl rubber, which was stopped for economic reasons (1916-1919), the I.G. Farbenindustric industrial unit in Germany resumed extensive research on synthetic rubber. At the beginning of this effort, the shape of the raw materials and the polymerization method were more important. Because methyl rubber suffers from lack of elasticity. At that time, there was no economic whisper for the production of isoprene, which was the structural unit of natural rubber. Furthermore, comparative tests showed that isoprene did not provide a significantly better synthetic rubber than butadiene. So the main effort was focused on butadiene. Finally, in 1926, bulk polymerization by alkali metals was followed to produce various polybutadienes. Despite the rarity of this substance at that time, polybutadiene attracted a lot of attention.Therefore, other polymerization methods, especially emulsion polymerization, were investigated. All attempts to homopolymerize butadiene by emulsion method to produce a useful rubber failed. The obtained rubber had a very high molecular mass and showed excellent elasticity. But it performed poorly in other mechanical properties. In addition, its processability was facing a serious problem. Another problem of this rubber[1] was its short shelf life [1].

    Therefore, only the discovery of copolymerization of butadiene with monoolefins eliminated these polymerization problems. This polymerization was discovered in 1929 in an industrial unit in Leverkusen, Germany, which involved the copolymerization of a mixture of butadiene with other monomers. A large number of monomers were investigated and finally styrene was selected as the second monomer for copolymerization with butadiene. During this work, Konrad and Tschankur, as well as Kleiner, produced a synthetic rubber from butadiene and acrylonitrile in 1930 that showed excellent resistance to oils and fuels. This rubber was first called Buna N and then Perbunan. It was also found that in addition to better resistance to oils and fuels, this rubber has thermal stability and better abrasion resistance and less permeability to gases [1]. Therefore, all efforts at that time were focused on this promising product because it seemed that despite the low price of natural rubber in those days, it was considered a great opportunity economically. Thus, in 1934, the almost stagnant methyl rubber industrial unit in Leverkusen started producing nitrile rubber. This rubber was exported to the United States and Great Britain in 1937, and then in 1939, nitrile rubber was produced in the United States. After that, other countries, including Canada, joined the few countries producing nitrile rubber and gradually this rubber reached the production stage in other countries [1]. Butadiene moieties in the copolymer chain are responsible for low temperature elasticity and flexibility. Also, butadiene has an unsaturated double bond, which provides suitable places for cross-links during the vulcanization process. On the other hand, these unsaturated bonds are a place for chemical, thermal and oxidative attack.

    The second component of the copolymer chain, which is acrylonitrile, is responsible for resistance to fuels and oils. In addition to this hardness, wear resistance and tensile strength are related to this component. By increasing the amount of acrylonitrile, better heat resistance and impermeability to gases can be achieved. The amount of acrylonitrile in nitrile rubber ranges from 15% to 53%, and the amount of acrylonitrile in the general type of nitrile rubber is about 34%. By choosing an elastomer with the appropriate amount of acrylonitrile according to its other properties, nitrile rubber can be used in a wide range of applications depending on the type of need. style="direction: rtl;"> 

    1-3-     Applications of nitrile rubber

    The properties of nitrile rubber have introduced it as an excellent material for sealing applications. The popularity of nitrile rubber is due to its excellent resistance to petroleum products as well as its ability to service at temperatures above 120 °C. With this temperature resistance, nitrile rubber compounds can be resistant everywhere, but they have the most service in automotive applications. Taking advantage of the properties of nitrile rubber, it is possible to produce selected compounds and molded parts.

  • Contents & References of Preparation of nitrile rubber by emulsion polymerization method and checking its properties

    List:

    Table of Contents

     

    Title                                                                                                      Page number

    Abstract..1

    Chapter One: Introduction. 2

    1-1- History. 2

    1-2- Features of nitrile rubber. 3

    1-3- Applications of nitrile rubber. 4

    1-4- Chemical structure. 5

    1-5- The amount of acrylonitrile. 7

    1-6- Production process. 7

    1-6-1-     Polymerization. 7

    1-6-2- Completion. 9

    1-7- Comparing two hot and cold methods. 10

    1-8- Objectives. 10

    1-8-1- Investigating the microstructure and composition of nitrile rubber copolymer. 11

    1-8-2-     Investigating the physical properties of nitrile rubber. 12

    1-8-3-     Latex review. 12

    Chapter 2: Theory and an overview of the studies. 14

    2-1- Classical emulsion polymerization theory. 14

    2-2- Kinetics of emulsion polymerization. 17

    2-2-1- Harkins mechanism. 17

    2-2-2- Smith and Everett theory. 18

    2-2-3-     Investigating the kinetics of emulsion polymerization. 19

    2-2-4-     Speed ??changes with conversion percentage. 20

    2-3- Nucleation mechanisms. 21

    2-3-1-     Formation of particles. 22

    2-3-2- Contribution of different nucleation mechanisms to particle formation. 22

    2-3-3- The fate of radicals in emulsion polymerization. 23

    2-4- Colloidal stability in emulsion polymerization. 24

    2-4-1- stabilization mechanisms. 24

    2-4-2- The effect of different electrolytes on colloidal stability. 26

    2-4-3-     Clotting process. 26

    2-5- Components of emulsion polymerization and materials used. 27

    2-5-1-     Monomers and their ratio 27

    2-5-2-     Water. 28

    2-5-3-     Starter system. 28

    2-5-4- Surface active agents. 36

    2-5-5- chain transfer agents. 39

    2-5-6- Inhibitors 39

    2-6- Principles of copolymerization. 40

    2-6-1-     Investigation of emulsion copolymerization of butadiene and acrylonitrile monomers. 42

    2-6-2-     Copolymerization. 42

    2-6-3- Emulsion copolymerization processes. 47

    2-7- Process and product specifications. 50

    2-7-1-     Molecular mass and its distribution. 50

    2-7-2-     The chemical composition of the copolymer and its distribution. 51

    2-7-3-     Transverse connections. 54

    2-7-4-     Macroscopic characteristics. 55

    2-8- Summary. 56

    Chapter three: Materials used and methods of work 57

    3-1- Materials used. 57

    3-2- Method of preparing samples 58

    3-2-1- Reactor specifications 58

    3-2-2- Method of preparation. 59

    3-3- Designed experiments. 62

    3-3-1-     Statistical methods to determine the optimal feed recipe. 62

    3-3-2- Investigating the effect of various factors on molecular and macroscopic properties. 63

    3-4- Tests and devices used to identify nitrile rubber. 63

    3-4-1-     Measurement of latex solid percentage and conversion percentage. 63

    3-4-2-     Clotting method. 64

    3-4-3- Measuring the gel. 65

    3-4-4- Mooney viscosity test. 65

    3-4-5- Rheometer test. 66

    3-4-6- Tensile test. 66

    3-4-7- Compressive mana test. 67

    3-4-8- Leap test. 67

    3-4-9- Hardness test. 67

    3-4-10- Nuclear Magnetic Resonance Spectroscopy (NMR) test 67

    3-4-11- Dynamic Light Diffraction (DLS) test 68

    3-4-12- Differential Scanning Calorimetry (DSC) test 68

    3-4-13- Elemental Analysis (CHNO) test 68

    Chapter Four: Results and discussion. 69

    4-1- An introduction to test design (DOE) 69

    4-2- Platelet-Borman screening test design. 72

    4-2-1- Results related to determination of conversion percentage: 76

    4-2-2- Data analysis 76

    4-3-  Design of all-factor experiment. 82

    4-3-1- Results related to determination of conversion percentage. 84

    4-3-2- Data analysis 85

    4-4- Determining the optimal feed order. 92

    4-4-1- The results of the dynamic light diffraction test 93

    4-4-2- The results92

    4-4-1- The results of the dynamic light diffraction test 93

    4-4-2- The results of the differential scanning calorimetry test. 95

    4-4-3-     Investigating the microstructure of the copolymer using NMR. 96

    4-4-4- Measuring the gel. 103

    4-5- Investigating the microstructure changes of the copolymer during polymerization. 104

    4-5-1- Elemental analysis test. 104

    4-5-2- NMR test. 111

    4-6- Changing the factors separately on the optimal feed recipe. 118

    4-6-1- Investigating the effect of Rosini soap emulsifier on polymerization kinetics. 118

    4-6-2- Investigating the effect of temperature on the amount of gel. 122

    4-6-3- Investigating the effect of chain transfer agent on molecular mass. 123

    4-7- Physical and mechanical properties. 124

    4-7-1- Determining the mechanical properties of the mixture prepared from the optimal product (NBR-FF 6) 124

    4-7-2- Investigating the effect of molecular mass and the preparation temperature of the copolymer on tensile properties. 127

    Chapter five: conclusions and suggestions. 129

    References. 132

     

    Source:

    [1]      Hofmann W., “A Rubber Review for 1963 Nitrile Rubber,” Rubber Chem. Technol., 1–252, 1964.

    [2]      Othmer, R. E., Kirk D. F., “Encyclopedia of chemical technology (4thed.).” New York: Wiley-Interscience., 1998.

    [3]      “www.icis.com.” [4] Hoffman W., "Synthetic Rubber in Rubber Technology Handbook." Hanser Publisher, Munich, 1988. [5] El-Aasser P. A. L. and M. S., "Emulsion polymerization and emulsion polymer." John Wiley & Sons Ltd, 1997. [6] Anderson C. D., Daniels E. S., "Emulsion polymerization and latex applications." Smithers Rapra Publishing, 2003.

    [7] Chern C. S., "Emulsion polymerization mechanisms and kinetics," Prog. Polym. Sci., 5, 443–486, 2006.

    [8]      Harkins W. D., “A General Theory of the Mechanism of Emulsion Polymerization1,” J. Am. Chem. Soc., 6, 1428–1444, 1947.

    [9] Parts A. G., Moore D. E., Watterson J. G., “Some considerations concerning the theory of emulsion polymerization,” Die Makromol. Chemie, 1, 156–164, 1965.

    [10] Ugelstad J., M?rk P. C., Aasen J. O., “Kinetics of emulsion polymerization,” J. Polym. Sci. Part A-1 Polym. Chem., 9, 2281–2288, 1967.

    [11] Jingyu Shi, “Steric Stabilization,” Ohio State University, 2002.

    [12] Smith W. V, “The Partition of Acrylonitrile between Styrene and Water,” J. Am. Chem. Soc., 6, 2177–2179, 1948.

    [13] Mino G., "Copolymerization of styrene and acrylonitrile in aqueous dispersion," J. Polym. Sci., 102, 369–383, 1956.

    [14] Lu Q., Weng Z., Shan G., Lai G., Pan Z., “Effect of acrylonitrile water solubility on the suspension copolymerization of acrylonitrile and styrene,” J. Appl. Polym. Sci., 6, 4270–4274, 2006.

    [15] Madhuranthakam C. M. R., Penlidis A., “Modeling uses and analysis of production scenarios for acrylonitrile-butadiene (NBR) emulsions,” Polym. Eng. Sci., 10, 1909–1918, 2011.

    [16]    “www.engineeringtoolbox.com.” .

    [17] Bacon R. G. R., "The initiation of polymerization processes by redox catalysts," Q. Rev. Chem. Soc., 3, 287–310, 1955.

    [18] Blackley D. C., “Emulsion Polymerisation (Theory and Practice).” Applied Science Publishers LTD, 1975.

    [19] Sarac A. S., “Redox polymerization,” Prog. Polym. Sci., 8, 1149–1204, 1999.

    [20] Santana-Casiano J. M., Gonzalez-Davila M., Millero F. J., "The role of Fe (II) species on the oxidation of Fe (II) in natural waters in the presence of O2 and H2O2" Mar. Chem., 1, 70–82, 2006.

    [21] Andersen H. M., Proctor S. I., “Redox kinetics of the peroxydisulfate–iron–sulfoxylate system,” J. Polym. Sci. Part A Gen. Pap., 6, 2343–2366, 1965.

    [22] Wicklatz J. E., Kennedy T. J., Reynolds W. B., “Hydroperoxides as initiators of emulsion polymerizations at low temperatures,” J. Polym. Sci., 1, 45–58, 1951.

    [23] Fryling C. F., Follett A. E., “New oxidants for initiation of emulsion polymerization in antifreeze recipes at ? 10° C.,” J. Polym. Sci

Preparation of nitrile rubber by emulsion polymerization method and checking its properties