Summary of Chemical doctoral thesis: Study on enhancement of technical characteristics for some composite rubbers with nano additive

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The objective of the research is to evaluate combination ability of nano additive with carbon black reinforced for rubber and rubber blend; create rubber nanocomposite materials with a high quality, solvent durability and sustainability in the naturally humid environment.

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MINISTRY OF EDUCATION VIETNAM ACADEMY OF AND TRAINING SCIENCE AND TECHNOLOGY GRADUATE UNIVERSITY SCIENCE AND TECHNOLOGY --------------------------- PHAM CONG NGUYEN STUDY ON ENHANCEMENT OF TECHNICAL CHARACTERISTICS FOR SOME COMPOSITE RUBBERS WITH NANO ADDITIVE Major: Organic chemistry Code: 9.44.01.14 SUMMARY OF CHEMICAL DOCTORAL THESIS Hanoi - 2019
The work was completed at: Academy of Science and Technology- Vietnamese Academy of Science and Technology Science instructor: Pro.Doc. Do Quang Khang Reviewer 1: … Reviewer 2: … Reviewer 3: …. The thesis will be protected before the doctoral dissertation thesis, meeting at the Academy of Science and Technology - Vietnam Academy of Science and Technology at ... hour ... ', date ... month ... 2018 The thesis can be found at: - Library of the Academy of Science and Technology - National Library of Vietnam
A: Overview of the thesis 1. Problem statement Polymer nanocomposite material in general and rubber nanocomposite in particular are particularly interested in research and development in the time to come because they have many superior properties superiority. In rubber applications, reinforcement mostly used in orrder to create better quality products and reduce costs (active fillers). Traditional reinforcement in the rubber industry such as black coal, silica, clay powder... These enforcements were predominantly micro-sized at lower costs, so they are often referred to as fillers (active or inert fillers). Rubbers are reinforced with these materials are called composite rubbers. Different from rubber composite, rubber nanocomposite was reinforced with nanometer-sized fillers (their size has one of three dimensions below 100nm), nanocomposite rubbers were created by different techniques, such as mixing in a melted state, mixing in solution, mixing in latex state followed by method of coagulation and polymerisation around filler particles. Compared to rubber reinforced with micro fillers, rubbber reinforced with nano fillers has better stiffness, modular, anti-ageing and airproof property. For each type of filler, besides advantages, there are always disadvantages. Therefore, in order to promote advantages and limit disadvantages of each type of filler, recently, some researches have combined two type of fillers together [1,3] but not much. Realizing that the research direction of combining nano-additives with black coal reinforced for rubber materials is a new direction today, because the number of published works is still small and it is unclear the influence when combining black coal with nano clay, nanosilica and carbon nanotubes. Stemming from that reason, the thesis is aimed at: “Study on enhancement of technical characteristics for some composite rubbers with nano additive” as the subject of research. 2. Objectives of research and its content The objective of the research is to evaluate combination ability of nano additive with carbon black reinforced for rubber and rubber blend. - Create rubber nanocomposite materials with a high quality, solvent durability and sustainability in the naturally humid environment. The content of the research: - Study on denaturing nanoclay, carbon nanotubes, nanosilica surface with different agents, - Study on manufaturing and evaluating the property of rubber nanocomposite based on the blend of natural rubber (NR)/rubber butadien acrylonitril (NBR); natural rubber (NR)/Rubber clopren (CR) reinforced with nano additive, - Study on combining nano reinforced material with carbon black using in four type of substrates: natural rubber, blend natural rubber (NR)/rubber 1
butadien acrylonitril (NBR); natural rubber (NR)/Rubber clopren (CR) and blend rubber butadiene acrylonitrile (NBR)/polyvinyl chlorite (PVC), - Study on combining nanosilica, nanoclay and carbon black materials with each other in the substrate of blend rubber NR/CR. 3. Contributions of research - Denatured, organized nanoclay with a mixture of surfactants (DTAB; BTAB; CTAB with molar ratio was 30:5:65). Obtained organic clay with properties: 21,3% organic content; distance d100 = 1,86nm; swells in organic solvent (axetone, xylene: 16; 23ml). - Optimal CB content for rubber blend NBR/PVC (70/30) was 40 pkl. At this content, the materials had tensile strength increased by 47,1% compare to sample that had no containing CB. With higher CB content (50 pkl), carbon black particles tend to agglomerate making the tight structure of the material is broken, resulting in reduced material mechanical properties. - Suitable CNT content in order to combine replacing CB was 1 pkl. With CB/CNT content (39/1), rubber blend materials had structure tighter. Mechanical, thermal durability and thermal conductivity properties of rubber blend materials NBR/PVC were incrseased. - Rubber blend nanocomposite materials NBR/PVC/39CB/1CNT had high mechanical-physical-technical properties can be satisfactory in order to create technical rubber products, especially abrasion resistance and great friction rubber products. - Suitable carbon black content in order to reinforce for natural rubber, blend NR/CR and NR/NBR was in the range of 25-30pkl. Combined nanosilica content for these blends were quite similar 5pkl. So, in order to reinforce for NR and blends with CR and NBR were 25pkl carbon black and 5pkl Nanosilica. At this content, breaked tensile strength increased about 11% (for NR), 18% for blend of NR/CR and 16% for blend of NR/NBR. - Suitable carbon black content in order to reinforce for rubber blend materials based on NBR/PVC were about 40pkl (compare to 100% rubber blend), significantly higher compare to material system from natural rubber and blend of NR with CR and NBR (only form 25-30pkl). At combining ratio of carbon black/CNT (39/1 pkl) giving tensile strength of material increase11%, increasing decomposition starting temperature as well as environmental durability. 4. The thesis structure The research includes 136 pages with 32 tables, 93 figures, 133 references. The thesis structure: Introduction 2 pages, Chapter 1: Overview 40 pages, Chapter 2: Materials and research methodology 10 pages, Chapter 3: Results and discussion 67 pages, Conclusion 2 pages, The publications relating to the thesis 1 page, References 12 pages. 2
B. Content of the thesis Introduction The introduction mentions the scientific and practical meaning. Then set targets and research content of the thesis. Chapter 1: Overview The overview synthesizes materials inside and outside the country relating to the topic of the thesis such as: - Rubber materials, rubber blend, nanocomposite rubber materials with its classification, its specific advantages and disadvantages. - Nano additives (carbon, silica, nanoclay) and methods of surface denaturation, which also indicate that the denaturation method by using mixture of surfactant created organic clay with high quality. - The application of nano additives and the combination of black coal in nanocomposite rubber technology. The combination of black coal with nanomaterials (mix 01 or 02 nanomaterials) is the target of the thesis. Chapter 2: Materials and research methods 2.1. Raw materials and chemicals - Carbon nanotubes multi wall: Baytubes - Bayer (Germany), 95% purity, - Bis- (3-trietoxysilylpropyl) tetrasunfide (Si 69.TESPT), China: the transparent yellow liquid, fat-soluble and aromatic as alcohol, ether, keton. Boiling point: 250°C, density: 1.08. - Polyetylenglicol: PEG 6000 (BDH Chemicals Ltd company Poole-UK), the melting temperature of 61°C. - Polyvinylclorua: 710 SG Vietnam, a white powder, size: 20-150 micrometers, specific mass: 0.46- 0.48g/cm3. - D01: refined tung-tree oil, yellow liquid, the proportion (at 20°C): 0.920- 0.945g/cm3. - Cetyl trimetylamoni bromua (CTAB): Merck (Germany), M = 364.46g/mol, purity: 97%. - Pure AlCl3: Merck (Germany). - Natural Rubber (NR): SVR- 3L, Viet Trung rubber company, Quang Binh. - Nitrile rubber (NBR): Kosyn- KNB35, Korea, containing acrylonitril 34%. - Clopren Rubber (CR): Baypren® 110 MV 49 ± 5, Lanxess - Vulcanizing additives include: + Sulfur, Sae Kwang Chemical Ind firm. Co. Ltd. (South Korea) + Zinc Oxide Zincollied; Stearic acid PT. Orindo Fine Chemical (Indonesia); Accelerators DM (Dibenzothiazolil disunfit), Accelerators D (N, N-diphenyl guanidine), Aging antioxidants D (Phenyl β-naphtylamin) of China - Other chemicals: Hydrochloric acid, toluene, KOH, iso-octane, ethanol 96%, acid acetic, DMF, petroleum ether, SOCl2, H2O2, NH3, tetrahydrofuran (THF), chloroform (CHCl3), CaCl2, acetone, petroleum ether of China. 3
2.2. Process of denaturing CNT surface and manufacturing rubber nanocomposite material reinforced-CNT 2.2.1. Denaturing CNT surface by Fischer esterification reaction The residual metal is removed from CNT by being soaked with special HCl and stirred for 2 hours at 50°C under a normal condition, washed several times with distilled water until pH = 7, dried for 12 hours, signed p-CNT. Disperse 0.3g p-CNT in 25ml mixture of NH4OH and H2O2 (1:1). Stir the mixture for 5 hours at 80°C under normal pressure. Mixed product is filtered by a PTFE membrane (capillary size: 0.2mic), washed with distilled water in neutral environment and cleaned by acetone several times. The denatured product (CNT-COOH) is dried for 48 hours at 80°C. - Chlorinated CNT Put 0.5gam CNT-COOH into a flask 100ml with 20ml SOCl2 and 10ml DMF available inside, and stir under a normal pressure for 24 hours at 70°C. By the end of the reaction will be a dark brown mixture CNT-COCl, filter and wash with THF and dry at normal temperature. - Synthesis of CNT-PEG Melt 1g PEG at 90°C, then put into a flask containing 0,1g CNT-COCl, stir for 10 minutes, then add the 40ml mixture of benzene/THF (3:1). Conduct the reaction at 80°C in 40 hours. When the reaction ends, put the mixed product in ultrasonic vibration for 30 minutes at 60°C, speed 3000rpm, then filter it through the PTFE membrane, the mixed black solid is washed with acetone and petroleum ether 3 times, dry at 90°C for 12 hours. 2.2.2. Alkylize CNT surface Put 0.2g CNT and 0.5g PVC into a 3-neck flask with 30ml anhydrous CHCl3 available inside, the flask is connected to a canister of anhydrous CaCl2 and another pipe embedded in NaOH liquid 10% to remove HCl released during the reaction. Add 0.5 g AlCl3, and mix in nitrogen environment at 60°C for 30 hours. After cooling the mixture down to the normal temperature, the CNT-PVC product is stirred in ultrasonic vibration in the tetrahydrofuran solvent (THF) for 10 minutes, filtered and washed several times with petroleum ether and acetone, dried at 60°C in 10 hours. 2.2.3. Denatured nanosilica by TESPT The denatured nanosilica process with bis-(3-trietoxysilylpropyl) tetrasulphite (TESPT) was carried out in 96% ethanol solution according to the procedure shown in figure 2.1. The reactions carried out in solution with pH = 4÷5 contain 0.5; 1; 2; 4% silane by weight. Reaction time is 1, 2, 4 and 8 hours respectively. The temperature of the reaction was surveyed at 200C, 250C 300C, 350C, 400C, 500C and 700C, respectively. Nanosilica/solvent ratio is 1/4. The mixture is stirred and remains constant throughout the reaction process. Mixture after the reaction is filtered and polymerized at 500C for 30 4
minutes, then maintained at 1000C for 1 hour. The product was obtained, dried at 1000C at atmospheric pressure for 2 hours. 2.2.4. Denatured clay The process of denatured clay such as the following: Clay has not yet been denatured in 50ml distilled water at a temperature usually obtained mixture (1). Take 100ml of distilled water into a 250ml glass of heat to 80 0C, stir with a speed of 700rpm. Then slowly pour (1) into. Obtain mixture (2), Keep mixture (2) stable at 800C for 2 hours. Take 50ml of distilled water to heat the cup to 800C. Add surfactant and stir to dissolve. Collect mixture (3) Pour slowly (3) into (2) and keep at 800C for 4 hours. Take clay that has denatured to pour into the order printing filter funnel to filter the precipitate. Wash with hot water 80-900C until Br- ends, titration with AgNO3 0.1N. Drying and grinding. 2.2.5. Method of creating a rubber nanocomposite 2.2.5.1. Natural rubber/nano additive 2.2.5.2. Rubber blend based on NR 2.2.5.3. Rubber blend sử dụng carbon black phối hợp with nano additive Table 2.3: Rubber compositing application, blended rubber with nano coal No Ingredients Content (volume section) 1 Rubber (Rubber blend) 100 2 D01 (TH1) 2(1) 3 Paraffin 2.0 4 Zinc oxide 4.5 5 Aging antioxidants A 0.6 6 Aging antioxidants D 0.6 7 Stearic acid 1 8 Accelerators D 0.2 9 Accelerators DM 0.4 10 Cumaron 1.0 11 Sulfur 2.5 12 Nano additive 0-10 13 Black coal 0-50 2.2.5.4. Vulcanization Samples are made by saving the rubber materials in the mold with a sample size of 200 x 200 mm and a thickness of 2 mm. Pressing pressure: 6kg/cm2; Vulcanization time: 20-25 minutes; Vulcanizing temperature: 145oC. Vulcanizing process is performed on hydraulic press (20T) TOYOSEIKI experiment (Japan). 2.2.6. Research methods (1) Infrared (IR) method on FTS-6000 P (Biorad, USA). (2) Raman spectrum method with HR LabRAM 800 (France). (3) UV-vis spectra on the SP3000 nano machine (Japan). 5
(4) Setaram machine's thermal weight analysis method (France), the heating speed is 10oC/min in the air environment, the study temperature range is from 25oC to 800oC. (5) X-ray diffraction spectroscopy on Siemens D5005 at the Department of Solid Physics - Faculty of Physics - University of Natural Sciences (Hanoi National University). The sample is crushed into a fine powder. The radiation source is CuK ( = 0.154 nm), the voltage of 40 KV, the intensity of 30 mA, the scanning speed of 0.020/2s from angle 2 is equal to 00 ÷ 100. (6) Research method using emission field scanning electron microscope (FESEM) implemented on S-4800 machine of Hitachi (Japan). (7) Method of studying morphological structure on transmission electron microscopy (TEM) on Jeol 1010 (Japan) machine. (8) Determination of particle size The size and distribution of nanoparticles before and after denaturation were determined by laser scattering method on Horiba Partica LA-950 device (USA) at Institute of Materials Chemistry, Military Science and Technology Institute. (9) Methods of determining the physical and mechanical properties of materials. Chapter 3: RESULTS AND DISCUSSION 3.1.1. Modified carbon nanotubes additive 3.1.1.1. CNT denaturation by polyvinylcloride Dispersion results in organic solvents: Figure 3.2: Dispersion of CNT (a) and CNT-g-PVC (b) in THF After alkylation, on the infrared spectrum (IR) of CNT-g-PVC (figure 3.3b) compare to the IR spectrum of CNT (figure 3.3a), the absorption peaks appear at 3048cm-1, 2914cm-1 corresponding to the valence oscillation of the - CH, -CH2 group and absorption peak at 1437cm-1 corresponding to the strain variation of the -CH2 group in the -CH-CH2- group. In addition, an absorption peak at 618cm-1 is found with the valence oscillation of the C-Cl bond. Figure morphological structure of materials: The morphological figure structure of CNT not denatured and CNT-g-PVC is studied by FE- SEM method, results are shown in figure 3.5 below: 6
Figure 3.5: FE-SEM image of the surface of CNT (a) and CNT-g-PVC (b) After oxidation, the structure is quite uniform with less shrinkage, diameter of CNT-g-PVC increase significantly up to 23.6 - 29.1nm (CNT diameter before joining PVC chain only 9.26 to 15.1nm). 3.1.1.2. Modifying CNT surface with PEG CNT surface modification diagram by PEG is described in Figure 3.9: Figure 3.9: Diagram of denatured CNT surface by Fischer esterification reaction On the spectrum of CNT-(CO)-PEG (Figure 3.10), there is a peak of 3264cm-1 characteristic for oscillation of OH group at the end of circuit CNT- COO-(CH2-CH2)n-OH, pic 3624cm-1 and 1668cm-1 denotes the signal of the NH group, the peak 1716cm-1 is the strong signal of the group (C = O) ester. The IR spectrum of CNT-(CO)-PEG also appears 1038cm-1 pic assigned to the CO group in PEG, the two peaks 2836 cm-1 and 3019cm-1 characterize the symmetric oscillation and antisymmetry of the joint C-H link in PEG. + Content group -(CO)-PEG and group -(CO)-TESPT paired on CNT: Content group -(CO)-PEG and group -(CO)-TESPT grafted onto CNT surface is also determined by the method of distribution Heat buildup (TGA). Results analysis is obtained, shown in Table 3.4. Table 3.4: Results of TGA analysis of CNT-(CO)-PEG and CNT-(CO)-TESPT Strong Strong Starting Mass loss decomposition decomposition Sample decomposition to 750oC, temperature temperature temperature (%) most 1, oC most 2, oC CNT 4900C 629.77 0C - 13.50% 0 0 0 CNT-(CO)-PEG 405 C 449.15 C 619.11 C 36.63% The thermal decomposition of CNT-(CO)-PEG starts at about 4050C and reaches a peak at 449.150C, extending until 619.110C, then the speed decreases until it reaches 7500C no longer losing weight, at this level of mass loss is about 36.63%, it is possible to roughly calculate the content of CO- PEG functional group attached to the surface of CNT corresponding to 7
23.13%. From the results of thermal analysis of the weight of CNT-(CO)- TESPT sample, this material began to decompose at about 399 0C and occurred strongly at 446.63oC lasting until 684.26oC. Starting decomposition temperature low as well as maximum first decomposition is low of organic groups attached to the surface of CNT as well as the poorly structured components of CNT begin to decay. The corresponding decomposition of the amino group and separation of sulfur atoms according to the reaction [8]: (CNT-COO)3Si(CH2)3S4(CH2)3Si(OH)3 t 0 C (CNT-COO)3Si(CH2)3S-H Next is the decomposition process of CNT and its heat-stable components. The process lasts until about 750oC, the volume does not change anymore, at this temperature the volume loss of the whole sample is 23.31%, so that can calculate the content of the preliminary group -(CO)- TESPT grafting on CNT surface is 9.81%. Comment: From the research results obtained shows that: - By alkyl reaction Fridel Craft has assembled PVC on the surface CNT with content PVC composite is about 23.0%. - By the surface reaction of Fischer esterification CNT (oxidized) by TESPT or PEG, 23.13% of group (-CO)-PEG and 9.81% -(CO)-TESPT on CNT surface. 3.1.2. Denatured nano additivesilica 3.1.2.1. Determine the optimal concentration of silane The infrared spectrum of Bis- (3-trietoxysilylpropyl) tetrasulphite (TESPT) is shown in figure 3.2. Figure 3.11: FT-IR of Bis-(3-trietoxysilylpropyl) tetrasulphite (TESPT) From figure 3.11, it was found that, in the range of 4000 - 400cm-1, TESPT has a number of characteristic absorption bands, namely: in the wave number of 3000 - 2800cm-1, there is a fluctuation of the etoxy group, the number of waves from 1200-1000cm-1 asymmetrical stretching oscillations of C-O-Si, 1000 - 600cm-1 with stretching oscillation of C - C and oscillating symmetry of C - O - Si, under 500cm-1 with knives Dynamic deformation of C - O - Si. The oscillations of TESPT at 2990cm-1 and 1395cm-1 are asymmetric and symmetrical strain fluctuations of the methyl group (-CH3) in ethoxy. Pic 2883cm-1 is the asymmetric oscillation of C-H in CH3. Pic 1445 and 1395cm-1 are respectively asymmetric deformations of C - H in methylene (CH2) and methyl groups. 8
Figure 3.12: FT-IR spectrum of Figure 3.13: FT-IR spectrum of nanosilica nanosilica denatured TESPT at different concentrations - In the survey concentration range, the optimal concentration of silane in order to denatured nanosilica is 2%. - Continuing to rely on infrared spectra, comparing the intensity of peaks at 2930cm-1 and 2860cm-1, specific for C-H, the reaction time is 4 hours; reaction temperature 300C; - Size of silica particles after denatured: Table 3.5: Particle size distribution of nanosilica has been denatured %< 5 25 50 75 95 Size (  m) 0,05 0,11 0,15 0,28 0,88 Figure 3.21: Particle size distribution of nanosilica after denatured The surface morphology of nanosilica particles before and after denatured is described in figure 3.22. a) Nanosilica b) Nanosilica denatured TESPT Figure 3.22: TEM images of nanosilica particles and denatured by TESPT 9
The TEM image in Figure 3.22 can be seen, after denaturing the nanosilica particles less agglomeration, leading to the reduction of particle aggregation size. The results are consistent with the results of particle size analysis in the above section. 3.1.3. Denatured nanoclay The Nanoclay modified with HH1 (DTAB:BTAB:CTAB molar ratio of 30:5:65) is the most effective. There are basic distance characteristics d=18.6nm, highest organic matter content (21.3%), high degree of solids in solvents. 3.2. Research and manufacture rubber nanocomposite materials based on rubber, reinforced rubber blend with nano additives 3.2.1. Effect of nano content on the mechanical properties of materials 3.2.1.1. Effect of unmodified nano content on the tensile strength of the material Nano (nanosilica (NS); carbon nanotubes (CNT); nanoclay (NC) are reinforced for the NR and rubber blend in different survey content from 1 to 10 pkl. Figure 3.24: Tensile strength of Figure 3.25: Length of elongation of materials using non-denatured nano nanomaterials not yet denatured From the results in the table and the figures above, the content of nano additives is suitable for each specific material background as follows: - For NR substrate, the suitable reinforcement nanosilica content (NS) is 3pkl, resulting in maximum tensile strength and elongation when breaking. - For rubber base blend NR/NBR nanosilica content reinforced at 7pkl, resulting in tensile strength and elongation at maximum breaking. - For rubber base blend NR/CR content of nanosilica with appropriate reinforcement at 5pkl, resulting in tensile strength and elongation at maximum breaking. - For rubber base blend NR/NBR content of CNT reinforced at 4pkl, resulting in tensile strength and elongation at maximum breaking. - For rubber base blending NR/CR with appropriate reinforcement nanoclay content at 5pkl, resulting in maximum tensile strength and elongation when breaking 3.2.1.2. The effect of nano additive denatured on the mechanical properties of materials Samples of materials are compared accordingly on the charts below: 10
Figure 3.26: Comparison of tensile Figure 3.27: Comparison of elongation strength of materials using denatured at breakage of materials using and non-denatured nano denatured and non-denatured nano From figure 3.26 and figure 3.27 charts, the drag properties of superior denatured nano-materials compare to when not denatured 3.2.2. The influence of content nano on the figure structure of material 3.2.2.1. Figure structure of Thai NR material using nanosilica denatured and not denatured: The NR of 3 pkl and 7 pkl nanosilica has not been and has been denatured by TESPT as shown in figure 3.30 and figure 3.31. a b a. NR/3pkl nanosilica b. NR/3pkl nanosilica modified TESPT Figure 3.30: Cutting surface FESEM image NR / NS 3pkl nanosilica a b a. NR/7pkl nanosilica b. NR/7pkl nanosilica modified TESPT Figure 3.31: Cutting surface FESEM image NR / 7 pkl nanosilica From figure 3.30 and figure 3.31, it was found that, in all samples, nanosilica particles dispersed in the NR substrate were mostly in sizes larger than 100nm. In materials reinforced with non-denatured nanosilica (Figure 3.30a) nanosilica particles are dispersed more steadily, even with particles up 11
to 1 m in diameter. Meanwhile, in reinforced materials 3pkl nanosilica denatured by TESPT, nanosilica particles are more evenly dispersed and have particles below 100nm (Figure 3.30b). In denatured material samples of 7pkl of non-denatured and denatured nanosilica, nanosilica particles are poorly dispersed and there appear to be quite a large set of particles in both cases (m-Figure 3.31). 3.2.2.5. Structure of figure thai model rubber blend materials NR/CR to strengthen organic nanoclay: On Figure 3.35 is a snapshot of the cut surface of some material samples from them. From the FESEM image, when the low content nanoclay (5pkl) dispersed nanoclay particles in rubber blend are quite uniform, the particle size is quite small only from a few hundred nanometers. a b Figure 3.35: FESEM photo cut surface of rubber materials NR/CR/nanoclay (a) 5 pkl nanoclay; (b) 10 pkl nanoclay The figures below are X-ray diffraction diagram of nanoclay and denatured HH1 nanoclay material HH1. Figure 3.37: X-ray diffraction scheme of Figure 3.38: Sample TEM image of NR / NR/CR containing 5pkl nanoclay HH1 CR containing 5pkl nanoclay From the X-ray diffraction scheme in Figure 3.37, the reflection peak (d001) of nanoclay after being dispersed into rubber blend NR/CR, the distance of nanoclay increased strongly, approximately 4.08 nm (initial base distance d001 = 1.86nm) with 2 angle = 2,2o. This result shows that the structure of nanoclay layers has been changed and transformed into an interlayer structure in rubber blends. This is also evidenced by TEM image in Figure 3.38. 12
3.2.3. Effect of nano additive on thermal properties of materials 3.2.3.1. Effect of nanosilica on the thermal properties of NR material TG/% DTG(%/phuùt) TG/% DTG/(%/phuùt) 100 0 100 0 -2 -2 80 80 -4 -4 60 Toån hao khoái löôïng: -92.84% 60 -6 -6 Toån hao khoái löôïng:93,80% 40 -8 40 -8 0 363.45 C , -11.23%/phuùt -10 -10 20 20 0 358.18 C, -11,15%/phuùt -12 -12 0 0 50 100 150 200 250 300 350 400 450 500 550 600 650 700 100 200 300 400 500 600 700 o o Nhieät ñoä ( C) Nhieät ñoä( C) Figure 3.40.a: TGA schema of Figure 3.40b: TGA schema of NR / 3 pkl NR/3pkl nanosilica samples nanosilica denatured sample by TESPT The mechanism of linking between nanosilica denatured by TESPT and rubber substrate can be described as follows (figure 3.42): Silica Silica Figure 3.41: Illustration of the reaction between NR and nanosilica denatured TESPT This bonding makes the material structure more rigid than the temperature and the highest decomposition temperature is higher than the larger compare model using non-denatured nanosilica (up to 2,850C and 5,270C respectively). This is also the reason for the mechanical properties of materials increasecao. 3.2.3.2. Effect of nanosilica on the thermal properties of rubber blend materials * Thermal properties of rubber blend NR/NBR reinforced nanosilica * Thermal properties of rubber blend NR/CR system to strengthen nanosilica * Thermal properties of rubber blend NR/CR system for nanoclay reinforcement: * Thermal properties of rubber blend NR/NBR reinforced CNT. In general, when using nano additive denatured for natural rubber and rubber blend substrates, the thermal properties of the fabric are positively affected. When there is a nano additive surface in the rubber base material that shields the impact of heat for rubber elements, it has increased the stability and thermal durability for materials. 3.3 Research, manufacturing nanocomposite rubber materials based on rubber blend carbon black reinforcement combined with nano additive 13
3.3.1. Combine nano silica and carbon black to reinforce natural rubber 3.3.1.1. The effect of content on black carbon on the mechanical properties of materials When the carbon black content increases: tensile strength of the material increase fast, the abrasion resistance resistance increases such as only a certain limit of 25pkl and then begins to decrease again. The choice of content carbon black is 25pkl used in order to conduct further surveys. 3.3.1.2. Effect of nanosilica on the physical properties of materials The results of examining the effect of content nanosilica on the mechanical properties of 25pkl carbon black NR materials are presented in Table 3.16 below: Table 3.16: Effect of content nanosilica on the mechanical properties of NR material containing 25pkl carbon black Property Tensile Elongation Content Abrasion level Stiffness strength tensile at break 3 (cm /1,61 km) (Shore A) nanosilica (pkl) (MPa) (%) 0 21.40 643 0.985 56.0 3 22.94 663 0.948 57.1 5 23.72 655 0.944 58.3 7 19.81 632 0.973 58.8 Notice that the tensile strength, abrasion resistance, elongation and elongation of the material peaked at optimal nanosilica content when combined with carbon black for NR material is 5pkl. 3.3.1.3. Figure structure of the material In order to evaluate the morphological structure of materials, we use scanning electron microscopy (SEM) in order to capture fracture surfaces of some typical material samples. Results are presented in figures 3.44, and figure 3.45 below: Figure 3.44: Surface SEM image Figure 3.45: Surface SEM image of fracturing NR/25pkl carbon black fractured material NR/25pkl carbon material sample black/5pkl nanosilica Realizing that, in the natural rubber model, there are 25pkl carbon black, carbon black filler is distributed relatively evenly on the surface of the NR platform, but there is a convex surface. When 5pkl nanosilica is added to the sample, the sample surface retains the regular distribution of such NR 14
fillers as 25pkl carbon black reinforcement, but the surface is less convex. This proves that with small content nanosilica still maintains the uniform distribution of the components in the material block, the components in the combination are better connected. Thus, the fractured surface of the material is less convex, concave, indicating the figure structure of the tight material. 3.3.1.4. Effect of denatured process on thermal stability of materials Table 3.17: Starting decomposition temperature and mass loss of quantitative materials Starting The strongest Weight loss Sample decomposition decomposition o o to 440 0C [%] temperature [ C] temperature 1 [ C] NR/25pkl carbon black 302.2 374.05 66,359 NR/25pkl carbon 303.6 374.07 65.829 black/5pkl nanosilica NR/25pkl carbon 299.0 375.06 62.625 black/10pkl nanosilica Realizing that the material's durability is a little bit higher when the content of nanosilica denatured is 5pkl (starting decomposition temperature increase of 1.4oC). When the nanosilica content is too high (10pkl) starting decomposition temperature of the material falls sharply (4oC reduction). This can be explained by the fact that the nanosilica content in the rubber component is too large, which leads to the formation of separate phases (such as the figure state structure indicated), reducing the tight structure of the material leading to The thermal stability of the material decreases. 3.3.1.5. Environmental stability of materials The aging coefficient of the material is determined according to TCVN 2229-77 after testing in the air and salt water 10% at 70oC after 96h is shown in Table 3.18. Table 3.18: Aging coefficient of the material after testing at 70oC after 96 hours of testing in air and 10% saline Aging factor In the air 10% salt water Samples (%) (%) NR/25pkl carbon black 0.80 0.80 NR/25pkl carbon black/5pkl nanosilica 0.86 0.85 Realizing that, when denatured with the NR reinforcement of 25pkl carbon black with content nanosilica is appropriate (5pkl compare to NR) has made the increase of environment for materials (aging coefficient in air and salt water 10% both increases significantly). This can be explained by the presence of nanosilica which makes the material more structured, preventing the effect of oxygen in the air as well as other aggressive elements, making the increase environmental durability for the material. 3.3.2. Combine nano additive silica, nanoclay and carbon black to enhance the blend of natural rubber and rubber cloropren 15
In rubber processing technology, people use many types of reinforcing fillers such as black carbon, silica, clay, dolomite, ... However, in each specific rubber and additive system, the fillers have influence and content Different optimizations. In this study, the nano additive used includes: nanosilica (NS), carbon black (CB) and nanoclay (NC) as reinforcement for the rubber blend system NR/CR (70/30). 3.3.2.1. The effect of content on black carbon on the mechanical properties of materials Results of the survey are presented in figures 3.47 and 3.48 below. Figure 3.47: Effect of CB content on Figure 3.48: Effect of content of CB breaking strength and elongation at on hardness and abrasion of breaking of materials materials Notice that, when content carbon black (CB) increasen, tensile strength of increaseand material reaches maximum value at content carbon black is 30pkl. Own stiffness of increasing material gradually with the increasecontent carbon black The change of these values is because when the CB content is within the optimal limit of CB particles forming its network, it also separates the large rubber molecules in all directions to form a hydrocarbon network. Two interwoven networks, hooked together to form a rubber structure - the filler continuously enhances the mechanical properties of the material. From the above results, the combined carbon black content is 30pkl selected to order in order to continue research. 3.3.2.2. The effect of nanoclay content replaces nanosilica to the mechanical properties of the material Table 3.19: The effect of nanoclay content replaces nanosilica to the mechanical properties of the material Sample Tensile strength Elongation tensile Stiffness Residual (silica/clay) (MPa) at break (%) (Shore A) extension (%) SC0 (5/0) 22.79 608 61.4 14.0 SC1 (4/1) 23.14 632 61.8 13.8 SC2 (3/2) 24.56 653 62.0 13.2 SC5 (0/5) 22.85 607 63.2 12.0 Symbols of samples: SC0: NR/CR/5NS-30CB; SC1: NR/CR/4NS-30CB-1NC; SC2: NR/CR/3NS-30CB-2NC; SC5: NR/CR/30CB-5NC 16
Results on table 3.19 show that tensile strength and elongation when the material's breakage reaches the maximum value when nanosilica content is replaced with 2% nanoclay. Then, further increasecontent nanoclay replacement, these properties of the material again reduced. Particularly stiffness of materials increases and the residual extension is slow when the replacement content nanoclay increases. This change in properties can be explained: on the one hand, nanoclay has better reinforcement effect than compare to nanosilica. On the other hand, with content 2% nanoclay in the material block can create nano additive resonance effects and thus, tensile strength and elongation when breaking of the material is improved. 3.3.2.3. Effect of denatured process on thermal stability of materials Thermal durability of materials is evaluated by thermal thermal analysis (TGA) method. Results thermal analysis of models based on rubber blend NR/CR are shown in figures and tables below: Figure 3.50: TGA chart of material Figure 3.51: TGA sample material chart sample NR/CR/5NS-30CB NR/CR/3NS-30CB-2NC Realizing that the thermal stability of rubber blend material was significantly improved when there was 30pkl of black coal through the decomposition start temperature of the material increased sharply, from 280oC to 300oC. When combining 2% nanosilica replacement with nanoclay, the thermal stability of the material is also improved (the decomposition start temperature increases by 6oC, the highest decomposition temperature increases by more than 3oC, percentage of mass loss to 600oC of materials also decreased from 92.34% to 90.41%) Table 3.20. Table 3.20: Analysis results of TGA sample rubber blend NR/CR with nano additives Starting The strongest The strongest Weight Samples decomposition decomposition decomposition loss to temperature [oC] o 6000C [%] temperature 1 [oC] temperature 2 [ C] NR/CR/5NS 280.0 347.3 443.1 91.92 NR/CR/5NS-30CB 300.0 347.4 447.8 92.34 NR/CR/3NS-30CB-2NC 306.0 350.7 446.5 90.41 3.3.2.5. Research Morphological structure of materials Morphological structure of rubber blend material NR/CR/3NS-CB-2NC nanocomposite is determined by methods such as emission field scanning 17
electron microscope (FESEM) and X-ray diffraction. Figure 3.53 below is a cut surface FESEM image of the material sample. Figure 3.52 Material cut surface FESEM image NR/CR/3NS-30CB-2NC nanocompozit From FESEM images, nano-additives were dispersed in the rubber substrate quite evenly with a relatively small particle size below 100nm. VNU-HN-SIEMENS D5005 - Mau ClayNa+ 38 Results of X-ray diffraction analysis of modified nanoclay samples 5000 by mixture and sample NR/CR/3NS-30CB-2NC: 4000 d=18. 631 3000 Lin (Cps) 2000 1000 0 0.5 1 2 3 4 5 6 7 8 9 10 Figure 3.53: X-ray diffraction 2-Theta - Scale diagram of Figure 3.54: X-ray diffraction diagram of File: Huynh-Toan-Giap-DHBK-Clay Na+ 38.raw - Type: 2Th/Th locked - Start: 0.400 ° - End: 10.000 ° - Step: 0.020 ° - Step time: 1.5 s - Temp.: 25.0 °C (Room) - Anode: Cu - Creation: 04/22/08 20:32:28 nanoclay HH1 NR / CR / 3NS-30CB-2NC From the X-ray diffraction diagrams, the reflection peak (001) of nanoclay appears at angle 2 = 5.2o with the base distance d = 1.86 nm (Figure 3.53). With this base distance, the layers of the original nanoclay remain in order. After being dispersed into rubber blend NR/CR, the base distance of nanoclay increased to approximately 4.14 nm with the angle of 2 = 2.1o (Figure 3.54). This result shows that the structure the layers of nanoclay have been changed and changed into interlayer structures in the rubber base. Therefore, the physical and mechanical properties of the material improved markedly. 3.3.3. Combined study of enhanced nano silica and black coal for blends of natural rubber and nitrile butadiene rubber (NR/NBR) 3.3.3.1. Effect of black coal content on the mechanical properties of materials The used black coal content surveyed in the range of 20pkl-35pkl according to the result of the rubber content at 25pkl ratio is more advantageous in terms of elongation when breaking and abrasion resistance. 18