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MINISTRY OF EDUCATION AND TRAINING MINISTRY OF NATIONAL DEFENSE ACADEMY OF MILITARY SCIENCE AND TECHNOLOGY DANG TRAN THIEM RESEARCHING TO MANUFACTURE CARBOXYL TERMINATED BUTADIENE ACRYLONITRILE RUBBER IN THE APPLICATION OF MAKING BINDERS AND ADHESIVES Specialization: Organic Chemistry Code: 44 01 14 SUMMARY OF PhD THESIS IN CHEMISTRY Hanoi - 2019 The work has been completed at: Academy of Military Science and Technology Scientific Supervisors: Associate Prof PhD Chu Chien Huu Prof PhD Do Quang Khang Reviewer 1: Prof Dr Nguyen Dinh Thanh University of Science, Vietnam National University, Hanoi Reviewer 2: Assoc Prof Dr Dang Viet Hung Ha Noi University of Science and Technology Reviewer 3: Assoc Prof Dr Ninh Duc Ha Academy of Military Science and Technology The thesis was defended in front of the Doctoral Evaluating Council at Academy level held at Academy of Military Science and Technology at 8:30 AM, date … mon … , 2019 The thesis can be found at: - Academy of Military Science and Technology Library - National Library of Vietnam INTRODUCTION Necessity of the thesis Carboxyl‐terminated butadiene acrylonitrile (CTBN) liquid rubber is researched and developed to serve military sectors as materials for making adhesives for mixed propellant of various types of rocket engines Carboxyl‐terminated butadiene acrylonitrile (CTBN) liquid rubber is also used to manufacture advanced composite materials, make binder, fillings, environmentally resistant paint systems … Carboxyl‐terminated butadiene acrylonitrile (CTBN) liquid rubber has many precious properties but not exist in other polymers, especially in the application of making binder and adhesives for mixed rocket fuel The import of Carboxyl‐terminated butadiene acrylonitrile (CTBN) liquid rubber meeting technical requirements to make binder and adhesives is very difficult Currently, there are not any unit investing in researching and producing this type of rubber Therefore, the research to synthetize Carboxyl ‐ acrylonitrile (CTBN) liquid rubber is considered to be a scientific and practical research to satisfy urgent requirements of national defense and people’s life Objective of the thesis The topic: “Researching to manufacture Carboxyl‐terminated butadiene acrylonitrile in the application of making binder and adhesives” is execute for the objective of: Building up general conditions and processes and manufacturing Carboxyl‐terminated butadiene acrylonitrile, capable of applying to make binder and adhesives Research content of the thesis - Researching to select suitable materials and methods to synthesize Carboxyl‐terminated butadiene acrylonitrile - Researching to determine conditions to synthesize nitrile-butadiene rubber with carboxyl head terminal group - Determining conditions for refining and preserving liquid rubber products - Applying nitrile-butadiene rubber with carboxyl head terminal group to make binder and adhesives Scientific and practical significance and new contribution to the thesis: Research results of the thesis has opened a new research direction in the field of synthesizing polymer materials, making binder and adhesives with practical applications to proactively manufacture high-quality materials for assuring of technical equipment weapons in the army and people’s life * The research method In order to implement aforementioned contents, the thesis has used the method of polymers compound processing, the method of synthesizing polymers compound (original copolymer) and modern chemical and physical analysis methods (FTIR, NMR, GPC), methods of analysis and measurement of appropriate technical features to survey the technical specifications of the product * The layout of the thesis In addition to the introduction and conclusion, the thesis consists of three chapters, references and appendices Chapter I: Overview: Analyzing and evaluating domestic and overseas research situation Chapter II: Research method and experiment: Presenting synthetic process, methods of surveying and measuring features and quality indicators of the product Chapter III: Research results and discussion: This chapter focuses on presenting research results as obtained during the implementation of thesis CONTENT OF THE THESIS Chapter I: OVERVIEW The domestic and foreign research situation, related issues as well as contents to be addressed in the thesis have been analyzed and evaluated Chapter II: RESEARCH METHOD AND EXPERIMENT 2.1 Materials and chemicals Chemicals of Merck-Germany: acrylonitril, ≥ 98%, the initiator 4,4’-Azobis(4-cyanovaleric axit), ≥ 98%, reactive solvent tert-butanol, PbO, 99,2% Russian chemicals: nitrile-butadiene rubber containing carboxyl group in the head CKH-10 KTP, epoxy resin ЭД -20 Korean chemicals: epoxy resin YD-128, polyetheramine Chinese chemicals: toluen AR, etanol AR, metanol AR, axeton AR, terahydrofuran AR, metyletylketon AR, acid HCl 35,5%, KOH AR, H2O2 30%, NaNO2 98% Other chemicals: rubber CKH-18, Lanxess, 1,3-butadien, 99%, BHD England, the chemicals for analysis, N-phenyl-2-naphhtylamin 2.2 Equipment and devices - High pressure equipment system to synthetize Carboxyl‐terminated butadiene acrylonitrile (CTBN) liquid rubber by monomer copolymer method - Reactive cutout system by agent including: 3-neck glass flask 1000 ml; drip funnel 200 ml; stirrer 1200 revolutions/minute generating reflux; water stove - Other experimental devices: electronic scale, argon gas tank 99.9%, oil-ring vacuum machine, acrylonitril distillation equipment, planetary crushing and mixing equipment with the scale of 200g/batch Experimental method 2.3.1 Method of making liquid rubber using cutout agent Dissolving 25 g rubber NBR and 0,25g surfactant in 250ml Toluen in 3-neck glass flask with capacity of 1000ml Synchronous installation with stirrer, water stove Raising the reactive system to 60 ºC, dropping solution NaNO2 40% in the reactive system, then dropping solution H2O2 30% at a rate of 30 drops/minute Maintain reaction time for 72 hours, cool down and disassemble the product Precipitate and wash the product in large quantities of distilled water Dry the product for 24 hours in a vacuum cabinet to a constant volume 2.3.2 Method of synthetizing Carboxyl‐terminated butadiene acrylonitrile (CTBN) liquid rubber by copolymer method Step 1: Cooling system: Initially lower the flask temperature and chemicals included 1,3 butadien, acrylonitril, tert-butanol to -5 ºC Step 2: Removing oxygen in the flask by vacuum aspiration Step 3: Saturating the system with argon, loading argon inert gas into the flask to pressure 1,2atm Step 4: Feeding Loading liquid butadiene, acrylonitril, initiator solution into the quantitative bottle and then put it into the reactor with the connecting funnel in valve 3, the process of filling argon gas to prevent air from diffusing into the bottle Step 5: Executing the reaction Checking the valves of the reactor system, stir and raise the heat, maintain the temperature of the reaction system at the required temperature with the EG circulating pump as heated in flask When the reaction reaches the temperature as observed at the thermometer, gradually add amount of mixed catalyst above so that the speed of adding the size of 10ml catalyst solution/hour The catalytic supplementation process is conducted as follows: For the catalyst into the flash 3, open valve 3, valve and valve to adjust the opening of the valve so that the drip speed as calculated During the initial reaction the pressure will increase then stabilize due to polymerization, the determination time of molecular mass reaches 3,000-5,000 dvc as the required time to stop the reaction Step 6: Stop the reaction: Removing non-reaction monomer, cooling the reaction and disassemble the product 2.3.3 Refining method: The copolymer product is precipitated in pure methanol The product part of obtained polymer insoluble in methanol will separate the layer, the tert-butanol and the initiator azobis solvent shall dissolve in methanol and separate the upper layer The product is separated by repeated washing and continue to wash methanol The solvent mixed in the product is chased by vacuum deposition method and the product is finally put into a vacuum drying cabinet incorporating heating at 50ºC with a pressure of -1 atm from 24 hours to 48 hours Obtained product is a colorless, moderate viscosity liquid 2.3.4 Application of CTBN rubber to use as binder and adhesives 2.3.4.1 Application of CTBN rubber to be the binder a) Method of making binder b) Processing metal rubber paste 2.3.4.2 Application of CTBN rubber to be the adhesives for the mixed solid propellant fuel a) Method to determine the solidification ability of materials b) Method to research rubber application as adhesives 2.4 Research Methodology - Survey method: Including modern analytical methods such as: Infrared spectrum, TGA thermal analysis, nuclear magnetic resonance method H NMR, 13C NMR, photography of Scanning Electron Microscope (SEM) - Evaluation method: Determining kinematic viscosity according to TCVN 3171-1995; determining molecular mass by Gel permeation chromatography (GPC); determining iodine index by titration method; method of “determining total nitrogen by method Kjeldahl”; content of total carboxyl group of of rubber sample as determined according to TCVN 61272010; tensile strength, elongation to break and residual extension determined by TCVN 4509:2006; sliding tensile strength determined according to US federal standards: ASTM-D-816-55 or GOST: 14759 – 69; balance pull force determined according to TCVN - 1596 - 74; gel content is determined using the soxhlet kit; Chapter III: RESULTS AND DISCUSSION 3.1 Results of inspection and refining of raw materials 3.1.1 Results of raw material research and inspection 1,3 - butadien The butadiene gas tanks are tested for purity by mass spectrometry before conducting liquid rubber synthesis reaction According to the chromatographic results analyzing material sample containing only one component at retention time of 1,759 minutes, but no other pic were detected on the gas chromatography spectrum Combining with the mass spectrometry results to receive signal M+ by 55 and molecular fragments different from m/z = 36; 37; 38; 39; 40; 50; 51;52; 53; 54;55 to enably confirm to be 1,3-butadien 3.1.2 Research and inspection resuls of initiator 4,4’-Azobis (4cyanovaleric axit) Results of analyzing proton nucleus magnetic resonance spectroscopy H NMR, 13C-NMR samples of 4,4’-Azobis (4-cyanovaleric acid) are shown in Figure 3.2 and Figure 3.3 1H NMR spectrum with peak 1,645 (3H of CH3); 2.33 ÷ 2.19 (2H, H-2); 2,39 ÷ 2,359 (2H, H-3); 12,378 (H, COOH) 13C-NMR spectrum has pic 22.86 of CH3; 28.69 of C-2; 32.47 of C-3; 71.73 of C-4; 118.05 of C-5; 172,61 of C-1 Attributing resonance signals with protons and carbon allows us to confirm that the sample is 4,4’-Azobis (4-cyanovaleric acid) has the molecular structure as follows: 3.1.3 Results of acrylonitril purification research After refining acrylonitrile, testing some specific characteristics of the materials Results are presented in Table 3.1: Table 3.1: Physical and chemical properties of acrylonitrile after refining No Name Level Appearance: Colorless liquid, no mechanical impurities Density, 20 ºC 0,800-0,806 Extract, 25 ºC 1,3910-1,3920 Acrylonitrile obtained after distillation in pure form, not containing preservatives quinone to easily participate in polymerization 3.2 Research to determine the structure and properties of CTBN rubber produced by Federal Republic of Russia 3.2.1 Determining molecular mass of CKH-10KTP The result determining molecular weight showed that: analytical polymers have the number average molecular mass Mn = 2948 and the weight average molecular mass Mw = 3436, the multi-dispersion Mw/Mn = 1,165 is quite small, showing that the rubber distributed molecular mass relatively equal This means that solid polymerization shall give good mechanical strength 3.2.2 Determining molecular structure of CKH-10KTP rubber In the IR spectrum (Figure 3.5), the results of analyzing characteristic vibrations are observed that CKH-10KTP rubber has the structural characteristics of nitrile-butadiene rubbere with cacboxyl group such as: acrylonitril group with characteristic vibration frequency at 2238 cm-1, double bond C=C of butadien with characteristic vibration frequency at 1639 cm-1 Bond of C=O of cacboxyl group with characteristic vibration frequency at 1713 cm-1, -OH group with characteristic vibration frequency at 3431 cm-1 Characteristic vibration frequency at 913-968 cm-1, of cis, tran butadien Figure 3.5: Infrared spectrum CKH-10KTP rubber Results of spectrum analysis 1H NMR, 13C-NMR: The results showed that the chemical shift proton H on the spectrum 1H NMR, 13C-NMR of CKH-10KTP rubber has characteristics of molecular chain copolyme butadien acrylonitril: acrylonitril group, olefin group, vinyl Thus, through the research determing molecular mass, 1H NMR, 13 C-NMR spectrum possibly affirm that, CKH-10KTP liquid rubber is oligomer with the number average molecular mass Mn=2948; the weight average molecular mass Mw= 3436 and has the main molecular structure as follows: 3.3 Results of research generalizing CTBN rubber by cutout chain in solution using agent H2O2/NaNO2 The thesis has conducted cutting rubber chain NBR-18 by the agent H2O2/NaNO2 toluene solvent medium, using an assay solvent of tetrahydrofuran, reaction temperature 60 ºC, time of 72 hours Results determining molecular weight showed that: Polymer analysis has the number average molecular mass Mn = 9804, the weight average molecular mass Mw = 13.858 Infrared absorption spectrum of cutout product with redox agent H2O2/NaNO2 (Figure 3.10), with characteristic vibration of new groups at 3440 cm-1, 1721 cm-1 showing the appearance of new groups –OH, C-O-C, C=O Increasing in absorption intensity in the zone 3440 cm-1 showed that, hydroxyl groups are newly formed Spectral lines in the zone 1590-1609 cm-1 appears with very weak strength, proving that the circularisation process occurs lower than when cutting with pyrolysis Figure 3.10: Sample infrared spectrum NBR cutout chain by H2O2/NaNO2 Results of analyzing proton nucleus magnetic resonance spectroscopy (Table 3.6) showed that the proton-specific signals of chain oxidized NBR rubber molecule showed olefin and acrylonitril chains Table 3.6: Signal matching 1H NMR and Combined signal 13C-NMR and bonding characteristics of oxidized rubber No Proton characteristics of the bond δH (ppm) -CH=CH- 5,40-5,63 (-CH2-) 1,98-2,07 (-CH2-) (-CH-) 1,66 2,56 Spectrum analysis results 13C-NMR (Table 3.7) showed that vascularized rubber has functional groups and specific bonds as nitrile group (127-129 ppm), group olefin (131 ppm) No Table 3.7: Signal matching 13C NMR and Combined and bonding characteristics of oxidized rubber Carbon characteristics of the bond δc (ppm) -CH=CH131,6 (-CH2-) 24,2 (-CH2-) 32,2- 43,4 (-CH-) 27,4- 28,2 (C-N) nitril 119,2- 120,2 The thesis used H2O2/NaNO2 agent to oxidize for rubber cutout NBR 18 with molecular mass average several hundred thousand, elastic solid state The obtained product has a mass molecular average Mn = 9804; Mw = 13.858, viscous liquid state The cutout process by H2O2/NaNO2 agent does not change the main chain of the original NBR 18 rubber The appearance of a new hydroxyl functional group at the two ends of the chain, a relatively small average molecular mass is an important result to expand the metabolism and subsequent application 3.4 Research generalizing CTBN rubber according to copolymer method The process of synthetizing butadien rubber with carboxyl head terminal group is executed with the original copolymer monome butadien and acrylonitril in tert-butanol solvent, the initiator is 4,4’-azobis(4cyanovaleric axit) 3.4.1 Effect of the initiator content The molar ratio of initial materials is agreed with 1,3butadien:acrylonitril: tert-butanol = 5,56:0,57:4,58, change of mol 4,4’azobis(4-cyanovaleric axit) reacting as in Table 3.8 Table 3.8: Reaction to content 4,4’-bis azo valeric axit different Sam ple Butadien Mol M1 Weight (g) 300 M2 Acrylonitril Mol 5,56 Weight (g) 30 300 5,56 M3 300 M4 300 4,4-azobis(4cyanovaleric axit) Mol Terbutanol 0,57 Weight (g) 3,3 0,012 Weight (g) 330 30 0,57 6,6 0,024 330 5,56 30 0,57 9,9 0,036 330 5,56 30 0,57 13,12 0,144 330 11 Table 3.13: Specifications of synthetic copolymer product Sample name Content acrylonitril, % Kinematic viscosity at 50oC, Pa.s M5 6,15 7,96 M6 8,95 9,17 M7 13,54 13,56 M8 19,46 18,23 M9 25,27 24,91 Observation Reaction performance, % Bright yellow viscous liquid Bright yellow viscous liquid Bright yellow viscous liquid Bright yellow viscous liquid Bright yellow viscous liquid 17,6 19,5 22,7 23,6 23,9 3.4.5 The research determines the structure and properties of synthetic CTBN rubber 3.4.5.1 Results of infrared spectrum analysis: The results showed that most of the characteristic spectral lines in synthetic acrylonitrile butadiene rubber product is coincided with specific spectral line in Russian product (Figure 3.21) Figure 3.21: Infrared spectrum of sample CTBN synthetized, Federal Republic of Russia 12 13 3.4.5.2 Analysis results of H NMR, C NMR CDCl3 Figure 3.22: Nuclear magnetic resonance spectrum 1H NMR of sample CBTN Figure 3.22 showed that the chemical shift of protons H in polyme is copolymerization with butadien acryloniril Spectrum 1H NMR showed that during the copolymer process, two products react with the formula: Polymerization product Polymerization product Similar to the 1H NMR spectrum, on the spectrum 13C-NMR (Figure 3.23), possibly observing the signal of carbon atom of olefin, alkyl, and resonant signals as well as confirming the synthetic product to be composed of two main form as mentioned above b c a d e Figure 3.23: Nuclear magnetic resonance spectrum 13C-NMR of sample CTBN 13 3.4.5.3 Thermal analysis results The results showed that the thermal analysis line of two samples are nearly identical with the following variation (Figure 3.24) : In a temperature range of 30-380 ºC, the mass of two samples is stable, varying by as little as 5%, possibly due to part of polymer to be degraded or low molecular matter (residual monomer, solvent, moisture .) evaporated from 380-500ºC two samples strongly change the mass with two pic losing the characteristic mass at 462.1ºC (CKH-10KTP) and 461,3ºC (CTBN) because at this temperature the thermallydegraded polymer turns into combustion products, the similarity in the maximum decomposition pic contributes to the equivalent structure of the two tested polymers TG /% DTG /(%/min) TG /% DTG /(%/min) [1] 100.00 [3] 0.00 -2.00 80.00 100.00 0.00 90.00 -2.00 80.00 -4.00 -4.00 70.00 -6.00 -6.00 60.00 60.00 Mass Change: -98.08 % -8.00 Mass Change: -94.92 % -8.00 40.00 -10.00 -12.00 20.00 50.00 -10.00 40.00 -12.00 30.00 -14.00 20.00 100.0 200.0 300.0 400.0 Temperature /°C Main 2015-10-02 07:51 User: TUAN_ANH Instrument : NETZSCH STA 409 PC/PG File : C:\Users\TUAN_ANH\Desktop\chu Huu\CKH-10.dsv 500.0 10.00 [1] Peak: 462.1 °C, -15.03 %/min -16.00 [3] M10.dsv -14.00 [1] CKH-10.dsv TG DTG TG DTG Peak: 461.3 °C, -15.01 %/min [3] -18.00 -16.00 600.0 100.0 200.0 300.0 400.0 Temperature /°C 500.0 600.0 Main 2015-10-02 07:50 User: TUAN_ANH Instrument : NETZSCH STA 409 PC/PG File : C:\Users\TUAN_ANH\Desktop\chu Huu\M10.dsv Figure 3.24: Thermal analysis diagram for samples CKH-10KTP and CTBN 3.3.6 Inspecting and evaluating property stability of CTBN rubber The product Carboxyl‐terminated butadiene acrylonitrile (CTBN) liquid rubber after synthesizing, refining is supplemented with protective agent (kept separately for each batch of reaction) and preserved in accordance with technical requirements at the storage condition of 20ºC, humidity is less than 70% After months, the thesis has examined and compared the quality of product Carboxyl‐terminated butadiene acrylonitrile (CTBN) liquid rubber, specific results are as follows: 3.4.6.1 Researching the preservation of CTBN rubber The thesis has evaluated the stability of CTBN rubber product using N-phenyl -2- nathylamin (1% mass of rubber) to preserve Carboxyl‐terminated butadiene acrylonitrile (CTBN) liquid rubber It has also compared for samples without preservatives and samples using preservatives Results of observation presented at Table 3.17 14 Table 3.17: Preliminary assessment results on effectiveness of the preservatives Time (day) 5÷7 Appearance of sample without preservatives Appearing a thin film, color of the rubber gradually darkens 12 ÷ 14 Appearing lumps, layering in liquid rubber 19 ÷ 21 Crack, spliting on the film surface, amount of lumping increases Appearance of sample with preservatives Homogeneous liquid has no phenomenon of film formation, clumping, layering Homogeneous liquid has no phenomenon of film formation, clumping, layering Homogeneous liquid has no phenomenon of film formation, clumping, layering Table 3.7 results showed that samples without preservatives have a very rapid change in appearance characteristics Initial assessment is to use N-phenyl-2-nathylamine to stabilize CTBN rubber to be clearly effective From above results, the thesis used N-phenyl -2- nathylamin to preserve liquid rubber during 6-month storage period The product Carboxyl‐terminated butadiene acrylonitrile (CTBN) liquid rubber after synthesis, refining is added to preservative agent (kept separately for each reaction batch) and stored at condition of 20ºC, humidity less than 70% After months, conducting examination, comparing and re-evaluating the quality and physical and chemical properties of Carboxyl‐terminated butadiene acrylonitrile (CTBN) liquid rubber 3.4.6.2 Observation inspection All products of Carboxyl‐terminated butadiene acrylonitrile (CTBN) liquid rubber are in a viscous liquid state, with a bright yellow color, no phenomenon of film formation, clumping, layering or appearance of abnormal phenomena compared to when being synthesized 3.4.6.3 Checking structure and properties of CTBN rubber after months Table 18 Technical specifications of Carboxyl‐terminated butadiene acrylonitrile (CTBN) liquid rubber No Quality criteria Kinematic viscosity at 500C Total carboxyl content Acrylonitrile content Mass loss when dry Unit CKH10KTP Starting (CTBN) After months (CTBN) Pa.s 8,90 10,23 10,35 % % % 2,98 9,92 0,38 2,87 11,0 0,43 2,85 10,95 0,35 15 Acid indicator iod indicator Extract Viscosity according osvan viscometer mg KOH/ 100 g gam iod/ 100 gam second 37,11 35,71 35,45 260 261 261 1,511 1,509 1,509 56,3 56,7 56,9 After months of preservation, entire technical specifications of the product remains unchanged when initially synthesized and within the scope of the standard TY 2294-099-00151963-05 (Federal Republic of Russia) Basing on infrared absorption spectrum, nuclear magnetic resonance spectrum 1H NMR (Figure 3.25; 3.26; 3.27; 3.28), technical specifications of CTBN rubber showed that the rubber sample as manufactured after months of preservation are still stable, maintaining the quality and structure of the standard without any change compared to the starting time Figure 3.25: Infrared spectrum CKH-10KTP rubber (Russia) after months of preservation Figure 3.26: Infrared spectrum CTBN rubber after months of preservation 16 Spectrum results H NMR as stated in Figure 3.27 and 3.28 Figure 3.27: H NMR – Sample CTBN rubber after months of preservation Figure 3.28: H NMR – Sample CKH-10 Russia after months of preservation 3.5 Some application research results of CTBN rubber to make binder and adhesives 3.5.1 Application of CTBN rubber to make binder In this application research of the thesis, the research focused on effect of the content Carboxyl‐terminated butadiene acrylonitrile (CTBN) liquid rubber to the mechanical strength of the bond between synthetic rubber CKH-40 (vulcanized, obtaining tensile strength 145 kG/cm2; stretch to breaking greater than 250% ) with steel base CT3 and aluminum D16 when using binder on the basis of epoxy resin YD-128, curing agent D-230 polyeteramin The bond is solidified at room temperature (25- 30ºC) Results in Table 3.19 showed that as changing rubber ratio to epoxy resin, it showed that the rubber-metal bond strength is quite wide The highest durability value is achieved with types of balancing and sliding bonds with weight ratio of CTBN rubber and epoxy resin ED-20 by 30/100 17 Table 3.19: Results of rubber-steel bond strength CT3 % CTBN Balanced tensile strength, kG/cm2 Slide tensile strength, kG/cm2 Bond destruction characteristics 17,7 22,3 Cohesive 10 24,6 34,2 Bond 20 31,2 46,5 Bond 30 42,9* 69,7* Bond 40 37,9 63,7 Bond 50 27,3 38,5 Bond With the binder sample on the aluminum substrate (as stated in Table 3.20) there is a change in bond strength similar to that of steel, other than the ratio CTBN/ED-20 with a shift ratio of 20/100 This can be explained by the different polarity between aluminum and steel bases When degenerating epoxy resin with CTBN rubber, the bond strength has increased in comparison with non-degeneration epoxy of rubber with steel and aluminum bases With 30 pkl/100pkl epoxy, the bond strength has increased between rubber and steel, particularly: balanced tensile strength increased 242%; sliding resistance increased 312% When gluing rubber with aluminum base D16, with 20 pkl/100 pkl epoxy, the balanced tensile strength increased by 231%; sliding tensile strength by 282% Table 3.20: Results of measuring strength of binder on aluminum base Tensile strength Sliding tensile Bond destruction % CTBN on aluminum base strength characteristics 10,5 12,2 Cohesive 10 19,3 28,0 Cohesive 20 24,3 34,5 Bond 30 17,7 31,5 Cohesive 40 16,8 27,3 Cohesive 40 13,8 24,3 Cohesive Observing the destruction surface of rubber-metal binder system by Carboxyl‐terminated butadiene acrylonitrile (CTBN) liquid rubber, it showed that the destructive surface in the form of bond (deep destruction into the base materials) so the bond strength has greater value With nondenatured epoxy binder, the surface destroys the cohesion form (demolition 18 at the boundary between binder and base), so the bond strength is smaller The joint destruction has a concave surface, evenly distributed over two surfaces than the cohesive surface (Figure 3.30) Bond destruction Cohesive destruction Figure 3.29: Destructive characteristics of the bond By surveying the bond strength with different CTBN/YD-128 ratios, the effect of denaturing epoxy resin with CTBN rubber increased the adhesion of binder on rubber base and increased rubber – metal bond strength 3.5.2 Application of Carboxyl‐terminated butadiene acrylonitrile (CTBN) liquid rubber to make adhesives 3.5.2.1 Research on the solidification of CTBN rubber a) Research on mechanical strength of CTBN rubber The thesis shall use Carboxyl‐terminated butadiene acrylonitrile (CTBN) liquid rubber in combination with epoxy resin ED-20, PbO according to the proper ratio and shall solidify according to the regime (90 ºC/168 giờ) However, due to references not specifying the rate of CTBN rubber and epoxy resin, the thesis has conducted surveys with different ratios Results are shown in Table 3.21 Table 21: Effect of epoxy ED-20 content on mechanical strength Sample M1 M2 M3 M4 M5 M6 M5* Mass ratio CTBN /ED-20/PbO (gam) Tensile strength, (Mpa) 10 / 0,5 / 0,25 10 / 1,0 / 0,25 10/ 1,5 / 0,25 10/ 2,0 / 0,25 10 / 2,5 / 0,25 0,35 0,470 0,849 1,563 Long elongation as breaking, (%) 245,35 457,16 621,37 570,21 2,356 323,490 6,72 10 / 3,0 / 0,25 10 / 2,5 / 0,25 1,856 572,87 10,80 2,485 342,293 5,24 Residual extension (%) 42,09 36,87 20,80 19.00 19 When increasing the amount of epoxy from the sample M1 to M5, the tensile strength increases because the sample progresses to the optimal ratio of the reactants Sample M5 with epoxy content reaches 25 PKL compared to 100 PKL rubber with the best curing ability with a tensile strength of 2,356 MPa, elongation when breaking is 323.490%, residual extension is 6.12% Thus, with CKH - 10KTP rubber when solidified with the ratio in sample M5 shall achieve the highest mechanical strength Taking photos of the destroyed sample surface after breaking the sample on the electron microscope device for samples (M4; M5; M6) M4 M5 M6 Figure 3.30: Image of Destructive surface SEM of the samples The destructive surface of the materials under impact of traction for M4 sample is relatively flat, smooth, the development lines of the cracks are almost absent Meanwhile with sample M5; M6, the most typical is sample M5 with a rough, long and folded surface (Figure 3.31) This showed that there had a close bond in the material base, which means that the solidification of the material is relatively thorough b) Researching the modification of infrared spectrum of the sample in solidification process The selected sample is fabricated according to M5 in part a, fabricated and solidified in a dry way according to the method stated in Chapter After 24 hours of sampling, conducting analysis of infrared spectrum, remarking on the change of functional groups and evaluating the solid reactivity of materials Infrared spectrum in Figure 3.31 of the sample of adhesive material at the beginning of the solidification process showed the characteristics of liquid rubber containing carboxyl group Infrared spectrum on Figure 3.32; 20 3.33 of the material sample after 24 hours of solidification showed the difference with the upper spectrum on Figure 3.32, that is: Figure 3.31: Infrared spectrum of the sample at starting time characteristic appearance of the C=O bond of the ester group at the wave 1740 cm-1 instead of the link C=O of carboxyl group with frequency of 1713 cm-1 The vibration replacement at position 1740 cm-1 compared to 1713 cm-1 indicates that the carboxyl groups of rubber have joined the epoxy ring opening reaction to form este group Figure 3.32: Infrared spectrum of material sample after 24 hours (no catalysis) Figure 3.33: Infrared spectrum of material sample after 24 hours (with catalysis) 21 c) Researching the infrared change in the solidification process of materials Figure 3.34: Change of acid indicators in solidification process Acid indicator value in the first 10-hour period of material solidification is greatly reduced (Figure 3.34) The variation of acid indicators corresponds to the epoxy ring opening reaction (epoxy resin ED-20) d) Research on the change in gel content Determining variation in gel content of materials when conducting solidification to Model M5 (part a) Figure 3.35: Variation of gel content in solidification process Gel content increased rapidly at the first 60 hours of solidification (Figure 3.35) When the gel content increases corresponding to the polymer net bonds increases and viscosity of the object reaches the threshold, the materials moved from liquid to solid and the material mass loses the properties of the viscous liquid system From this time, the viscosity of the system is very large, the space factor, concentration in the reduction system of the functional groups makes the solidification process slow and stabilized at the time of 150 to 168 hours with the gel content in the system reaching the largest value by 87%, which is also the end of solidification process 22 3.5.2.2 Researching the mixing ability of adhesives in manufacturing technology of mixed solid propellant fuel a) Evaluating ability of mixing and durability of mixed solid propellant fuel Results measuring the breaking tensile strength of manufactured fuel samples on the basis of CTBN rubber of the thesis is presented at Table 3.22 Table 3.22: Technical specifications of mixed solid propellant fuel Results No Sample Measurement method NL-CTBN-M1 TCVN 4509:2013 kG/cm2 12,0 14,37 NL-CTBN-M2 TCVN 4509:2013 kG/cm2 12,0 15,57 TCVN 4509:2013 12,0 19,52 NL-CTBN-M3 Unit Required to obtain Product (thesis) kG/cm The tensile strength of propellant basing on CTBN rubber has the durability according to technical standards of the propellant A72 to be manufactured on the basis of CKH-10KTP rubber (technical condition of mixture fuel A72 built by Institute of Propellants and Explosives / General Department of Military Industries and Manufacture b) Evaluation of fire heat of mixed solid propellant fuel From results in Table 3.23, it showed that propellant is made on the basis of CTBN rubber of the thesis with the required fire temperature for adhesives used for mixed propellant (according to industry standards issued by Institute of Propellants and Explosives to be used for A72) Table 3.23: Results of burning energy measurement of mixed solid propellant fuel Results No Sample name Unit The world Product of he thesis Measurement method NL-CTBN-M1 Cal/g ≥1450 1535,3 06 TCN 889:2001 NL-CTBN-M2 Cal/g ≥1450 1522,9 06 TCN 889:2001 NL-CTBN-M3 Cal/g ≥1450 1541,5 06 TCN 889:2001 The above results may confirm that the chemical structure of CTBN rubber-VN in the thesis has similarity with Russian-made CKH-10KTP rubber This is consistent with judgment through spectroscopic methods and analysis of rubber properties in parts of CTBN structural research 23 CONCLUSION With the research contents, the thesis has achieved major results and contributions as follows: Major results - The thesis has conducted general research on Carboxyl‐terminated butadiene acrylonitrile (CTBN) liquid rubber into two main directions and achieved the following results: In the first direction, the thesis has used the method of cutting original rubber NBR-18 with the agent H2O2/NaNO2 in toluen, used tetra hydrofuran assimilation solvent Experimental results have created liquid rubber product with the average mass molecular of 10,000g/mol, on the chain frame of coplyme appearing new functional groups -OH, a state with a viscous liquid In the second direction, synthesis of Carboxyl‐terminated butadiene acrylonitrile (CTBN) liquid rubber according to original copolymer method of two monomers: 1,3- butadien, acrynitril and initiator in solvent As a result, the process of synthesizing Carboxyl‐terminated butadiene acrylonitrile (CTBN) liquid rubber has been developed, with a scale of 300 gam/batch, suitable for domestic chemical equipment conditions Specifically, Carboxyl‐terminated butadiene acrylonitrile (CTBN) liquid rubber is synthesized when the molar ratio of 1,3-butadien : acrylonitrile : ACVA = 5,65 : 0,38 : 0,023 The reaction is performed at 80ºC, from to hours CTBN rubber products have main technical specifications: total carboxyl content=2.87; acrylonitril group content=11.0; Kinematic viscosity 10.23 Pa.s CTBN rubber specifications are equivalent to those of liquid rubber made by Russia according to TY TY 2294-099-00151963-05 CTBN rubber storage condition has been built, using N-phenyl -2nathylamine (1% by weight) The product during storage is similar in quality to Russia's CKH-10TP product - The thesis has manufactured binder system and processing as used to paste vulcanized rubber and metal (aluminum D18 and steel CT3) from Carboxyl‐terminated butadiene acrylonitrile (CTBN) liquid rubber to be synthetized with epoxy resin YD-128 Endurance of bonding on CT3 steel base: balanced tensile strength = 42.9 kG/cm2, sliding tensile by 69,7 kG/cm2; he bond durability on aluminum base D18: balanced tensile strength = 24,3 kG/cm2, sliding tensile by 34,5 kG/cm2 - The adhesive system on the basis of CTBN rubber synthetized with epoxy resin ED-20 and solid material conditions have been manufactured Durability of adhesives on the basis of CTBN rubber after solidification achieved physical targets: tensile strength = 2,356 kG/cm2; breaking stretchability =323%; residual extension: 6,72% reaching the standard TY 24 2294-099-00151963-05 When mixing and preparing mixed solid propellant fuel The strength of mixed solid propellant fuel achieved tensile strength greater than 15 kG/cm2; the burning heat is greater than 1450 Cal/g (reaching the standard 06 TCN 889:2001) New contributions of the thesis - Initially establishing a system of synchronous conditions in the actual laboratory situation in Vietnam to control the copolymer reaction of monomers: 1,3-butadiene, acrylonitril using the initiator 4,4’-Azobis (4cyanovaleric acid) including: input material standards, molar ratio of reactants, heat mode, time and reaction environment, feeding order, CTBN rubber general equipment system - Establishing the refining process, selecting preservatives and the process of putting preservatives into Carboxyl‐terminated butadiene acrylonitrile (CTBN) liquid rubber - Results of the thesis have helped to clarify the nature of curing reaction between functional groups of CTBN rubber and epoxy resin in the presence of PbO catalyst - The thesis has successfully synthesized liquid rubber with oxidation method of NBR-18 synthetic rubber The molecular mass synthetic product is about 10,000g/mol, with OH groups on the main frame Further research direction of the thesis: - Research to complete the synthesis process of CTBN rubber with properties similar to those produced in countries such as: USA, Russia, China - Further survey of other researchs to make binder and adhesives, expand the application directions of CTBN rubber LIST OF SCIENTIFIC WORK PUBLISHED Dang Tran Thiem, Chu Chien Huu, Do Quang Khang, Nguyen Viet Bac, Ho Ngoc Minh, Pham Minh Tuan, Trinh Dac Hoanh (2015), “Studying to determine chemical nature of adhesives used to manufacture engine fuel ingots of IGLA missile journey”, Journal of Military Science and Technology, Special Issue in October 2015, 161166 Dang Tran Thiem, Chu Chien Huu, Do Quang Khang, Nguyen Viet Bac, Ho Ngoc Minh, Pham Minh Tuan, Trinh Dac Hoanh (2016) “Studying on possibility of synthesis of carboxyl terminated liquid butadiene acrylonitrile rubber according to original copolymer method in solution” Journal of Military Science and Technology, 43, 142-148 Chu Chien Huu, Nguyen Viet Bac, Dang Tran Thiem, Pham Minh Tuan, Ho Ngoc Minh, Trinh Dac Hoanh (2016), “Research on the curing process of carboxyl terminated liquid butadiene acrylonitrile rubber (CKH-10KTP) with epoxy resin ED-20” Việt Nam Journal of Chemistry, 54, 6e1, 115-118 Dang Tran Thiem, Chu Chien Huu (2018), “Synthetizing carboxyl terminated liquid butadiene acrylonitrile rubber in pilot scale” Journal of Military Science and Technology Research, Special Issue in August 2018, 276-281 ... kit; Chapter III: RESULTS AND DISCUSSION 3.1 Results of inspection and refining of raw materials 3.1.1 Results of raw material research and inspection 1,3 - butadien The butadiene gas tanks are... 3.5), the results of analyzing characteristic vibrations are observed that CKH-10KTP rubber has the structural characteristics of nitrile-butadiene rubbere with cacboxyl group such as: acrylonitril. .. Carboxyl‐terminated butadiene acrylonitrile (CTBN) liquid rubber by copolymer method Step 1: Cooling system: Initially lower the flask temperature and chemicals included 1,3 butadien, acrylonitril,
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