Chế tạo, khảo sát tính chất và hình thái cấu trúc compozit trên cơ sở nhựa epoxy gia cường sợi thủy tinh e và nanosilica tt tiếng anh

MINISTRY OF EDUCATION AND TRAINING VIETNAM ACADEMY OF SCIENCE AND TECHNOLOGY GRADUATE UNIVERSITY SCIENCE AND TECHNOLOGY -Ho Ngoc Minh PROJECT NAME: MANUFACTURE, INVESTIGATE THE PROPERTIES AND MORPHOLOGY OF COMPOSITE MATERIAL BASED ON GLASS FIBER E AND NANOSILICA-REINFORCED EPOXYRESIN Major: Theoretical Chemistry and Physical Chemistry Code: 44 01 19 SUMMARY OF CHEMISTRY DOCTORAL THESIS Ha Noi - 2019 The thesis was completed in : Graduate University Science and Technology/ Vietnam Academy of Science and Technology Supervisors: 1) Assist Prof PhD Tran Thi Thanh Van 2) Prof PhD Thai Hoang Reviewer 1: ………………………… Reviewer 2: ………………………… Reviewer 3: ………………………… The thesis will be defended at the doctoral thesis committee at the Academy level, meeting at the Graduate University of Science and Technology - Vietnam Academy of Science and Technology on ’, date … month … year The thesis can be found at: - Library of Graduate University of Science and Technology - Vietnam National Library LIST OF PUBLICATIONS Ngoc Minh Ho, Thi Thanh Van Tran, Thuy Chinh Nguyen, Hoang Thai "Characteristics and morphology of nanosilica modified with isopropyl tri (dioctyl phosphate) titanate coupling agent", Journal of Nanoscience and Nanotechnology Vol18, No 5, 2018, pp 36243630(7) (ISI) Ngoc Minh Ho, Thi Thanh Van Tran, Thuy Chinh Nguyen, Hoang Thai, Effect of surface-modified nanosilica on the characteristics, poroperties and morphology of silica/epoxy nanocomposites, The 6th Asian Symposium on Advanced Materials: Chemistry, Physics & Biomedicine of Functional and Novel Materials (ASAM6), pp 343348, 2017 Ngoc Minh Ho, Thi Thanh Van Tran, Thuy Chinh Nguyen, Hoang Thai, Epoxy/titanate modified nanosilica composites: morphology, mechanical properties and fracture toughness Tạp chí Khoa học Công nghệ, 56 (2A),133-140, 2018 Hồ Ngọc Minh, Trần Thị Thanh Vân, Nguyễn Thúy Chinh, Thái Hoàng, Chế tạo, nghiên cứu đặc trưng, tính chất nhựa epoxy đóng rắn hợp chất titan số hợp chất amin, Tạp chí Hóa học, 56(3), 401-406 (2018) Ngoc Minh Ho, Thi Thanh Van Tran, Thuy Chinh Nguyen, Hoang Thai, Epoxy-silica nanocomposite: Creep resitance and toughening mechanisms, Emerging Polymer Technologies Summit (EPTS) and Emerging Material Technologies Summit 2018 (EPTS/EMTS'18) / 2018 Ngoc Minh Ho, Thi Thanh Van Tran, Thuy Chinh Nguyen, Hoang Thai, Ternary nanocomposites based on epoxy, modified silica, and tetrabutyl titanate: Morphology, characteristics, and kinetics of the curing process, Inc J Appl Polym Sci 2019, 136, 47412 (ISI) INTRODUCTION Necessity of the thesis Polymer composite based on glass fiber E-reinforced epoxy resin were commonly used in transportation, electronics, mechanical engineering, machine, building, and chemicals … However, the disadvantages and limitations affecting the application of this composite material are their brittleness and poor impact resistance Therefore, improving toughness / toughening for epoxy resins is very important Some nanoscale additives have been applied to manufacture epoxy-based composites as products for industries Among nano additives, surface modification of nanosilica with organic coupling agent is one of the most commonly used for polymers, rubbers, and plastics because it is easy to find, easy to use, relatively cheap Titanium-based hardened epoxy resin can work long time at high temperature Research on composite materials based on epoxy / glass fiber combined with surface modification of nanosilica by titanate coupling and titanium curing agent is very new, promising to create material system with high mechanical, physical, thermal properties And good electrical Therefore, the PhD student chooses the thesis topic "Manufacture, investigate the properties and morphology of composite material based on glass fiber E and nanosilica-reinforced epoxy resin” Purpose of the thesis Manufacture composite based on epoxy reinforced by glass fiber with organ – modified nanosilica using organotitanate curing agent that have good mechanical strength, thermal stability, flame restraint ability Improve the toughness of epoxy resin by incorporating reinforcing agent such as organ – modified nanosilica and glass fiber with appropriate manufacturing condition and ratio The main research content of the thesis Study on grafting nanosilica surface with KR-12 titanate coupling agent to enhance their dispersion ability in epoxy resin Study on curing reaction of epoxy resin YD-128 by tetrabutyl titanate and properties of post-hardening products Manufacture, investigate the properties and morphology of nanocomposite material based on epoxy, nanosilica and tetrabutyl titanate Manufacture, investigate the properties and morphology of composite material based on glass fiber E and nanosilica-reinforced epoxy resin New contributions of the thesis Successfully grafted K200 nanosilica particle surface with KR12 titanate coupling agent Nanosilica nanoparticles after modified have good dispersion ability in epoxy resin We studied the curing reaction of YD-128 epoxy resin with tetrabutyl titannate and clarified the advantages of this curing agent compared to conventional amine compounds Explained the positive effect of KR-12/nanosilica to mechanical properties, dynamic mechanical properties, toughness, toughness, toughening mechanism of composite material based on epoxy/mnanosilica/ tetrabutyltitanate and glass fiber CHAPTER OVERVIEW OF EPOXY RESIN, NANOCOMPOZIT AND COMPOZIT MATERIALS BASED ON EPOXY/ NANOSILICA / GLASS FIBER This chapter present the following: Epoxy resin: Classification, physical and chemical properties Curing agents, curing mechanisms and applications of epoxy in various fields Nanosilica: introduction about composition, properties, structure, applications of nanosilica in industry and surface modification methods to increase their dispersion ability in plastic matrix Introduction about polymer composites, epoxy resin, reinforcements and some parameters affected on the durability of materials Domestic and foreign research situation and application of composite materials based on epoxy / nanosilica / fiberglass CHAPTER EXPERIMENTAL 2.2 Methods 2.2.1 Determine coupling efficiency of KR-12 on nanosilica K200 Was determined by thermogravimetry: H = (mbt.750 – mbd.750)/ mo where: mbt.750 is the mass of SiO2 after modifying at 750 oC mbd.750 is the mass of unmodified SiO2 at 750 oC mo is the mass of initial SiO2 2.2.2 Determine particle size and Zeta potential Particle size distribution and zeta potential of nanosilica before and after modifying was determined by Zetasizer Nano ZS (Malvern-UK) using laser scattering method 2.2.3 Determine gel content Gel content of the samples after curing was determined by Soxhlet extraction and calculated using the following formulation: GC = 100 (m1/m0) where: m0 is the mass of initial sample (g); m1 is the mass of the sample after extracting (g); GC: gel content (%) 2.2.4 Viscometry The viscosity was determined on the viscometer Brookfield Model RVT- Series 93412 (American), at 25 oC following the standard DIN 53018 2.2.5 Transmitted Electronic Microscopy (TEM) TEM image was recorded on JEM1010 of JEOL (Japan) The sample was cut into ultrathin layers having the size of 50÷60 nm by specialized knife Leica Ultracut S microtome, then take TEM image at acceleration voltage of 80 kV 2.2.6 Field Emission Scanning Electronic Microscopy Was done on high resolution Model HITACHI S-4800, Japan, acceleration voltage of kV 2.2.7 Energy Dispersive X-rays Was determined on Model HORIBA 7593H (England) 2.2.8 Infrared Spectroscopy FT-IR spectrum was recorded by TENSOR II (Brucker) with wave number from 4000 cm-1 to 400 cm-1 at atmospheric temperature 2.2.9 Thermal Analysis * Thermogravimetry analysis (TGA): Use NETSZSCH STA 409 PC/PG (Germany), in nitrogen and atmosphere, heating rate of 10 o C/min * Differential Scanning Colorimetry (DSC): Was done on Netsch DSC 204F1, in nitrogen, temperature range 30–300 oC with the heating rate of 5, 10, 15, and 20 oC/min 2.2.10 Dynamic Mechanical Analysis Was done on DMA-8000 (Perkin Elmer, America) by single bending method, with heating rate of oC/min, temperature range 30-200 oC, vibration frequency Hz 2.2.11 Determine toughness and destroying energy Fracture toughness of the sample was determined following the standard ASTM D 5045-99 on LLoyd 500 N (England), the stress applied rate of 10 mm/min at room temperature 2.2.12 Determine bending strength Was determined following ISO 178:2010 on Instron 5582-100 kN (England), bending rate of mm/min 2.2.13 Determine tensile strength Was determined on Zwick (Germany) following ISO 527-1:2012 with the dragging rate of mm 2.2.14 Determine impact resistance Was determined following ASTM D6110 on Ray Ran (America) Each sample was measured six times and take the average 2.2.15 Determine Interlaminar Fracture Toughness Was determined following ASTM D 5528-01 [85], on Lloyd 500 N (England) with the interlaminar pull off rate of mm/min 2.2.16 Preparation of the samples 2.2.16.1 Modify nanosilica Weigh nanosilica in the beaker, adding toluen and stir thoroughly at the speed 21.000 round/min for minutes, then sonicate the mixture for 10 minutes Adding slowly KR-12 with different contents (5; 10; 15; 30; 45 % compared to nanosilica) into the system, repeat the process of stirring and sonicating times Then, the mixture was separated from the solvent by centrifuging with the speed of 7000 round/min, obtaining the gel then using toluen to wash KR-12 that does not react, the process was repeated times then dry to remove toluen at 90 oC for 24 hours 2.2.16.2 Prepare nanocomposite based on epoxy and m-nanosilica Mix thoroughly epoxy YD-128 and m-nanosilica with different contents by mechanical stirrer, adding curing agent TBuT with the studying ratio, then pour into the mold that has been cleaned and anti-stick Curing process was done at different temperatures and times then machined to determine mechanical properties (tensile strength, bending strength, impact resistance) 2.2.16.3 Prepare epoxy with different curing agents Weigh epoxy resin and curing agents into beakers, with the composition given in Table 2.1, stir the mixture for minutes then vacated to remove bubble The mixture was poured into the mold (clean, antistick) curing and determining mechanical stability Table 2.1 Composition of epoxy resin and curing agents Resin – curing Epoxy Curing Curing condition agent YD128, g agent, g EP-TBuT 100 5-20 hours 150 oC hours (25 oC); 10 EP-PEPA 100 20 hours (70 oC) hours (25 oC); 10 EP-TETA 100 10 hours (70 oC) hours (25oC); 10 EP-mPDA 100 10 hours (70 oC) 2.2.16.4 Manufacture composite epoxy/m-nanosilica/TBuT/glass fiber m-nanosilica was dispersed in epoxy resin YD128 with the ratio 0÷7 % by weight, then add 15 fraction per weight (pkl) of curing agent TBuT Glass fiber was dried 100 oC for hours to remove moisture Epoxy resin or epoxy-nanosilica were prepared as in 2.3.2 Glass fiber was cut into rectangle sheet having the size (150 x 200) mm then put layer by layer in the mold and pour the resin with the different ratios of glass fiber/resin Distribute the resin to permeate into the fiber by roller and brushes The samples of composite was then cured at 120 for hours in vacuum dryer CHAPTER RESULTS AND DISCUSSION 2.1 Determination of coupling efficiency of KR-12 onto nanosilica nanosilica The reaction of KR-12 with the surface of nanosilica is described in Figure 3.1 Carried out in Toluen Fig Functionalization of silica nanoparticles with tiatanate agent The result reveals that easy methodology for functionalization of SiO2 nanoparticles with titanate agent KR-12 in toluene solvent The surface reaction was found to be rapid, less energetic demanded thus less depends on reaction temperature and completes in a short reaction period The loading amount of titanate was found to be strongly depending in relative concentration of titanate agent Grafting efficiency was determined via thermal analysis, the appropriate content of KR-12 to modify nanosilica is 15 % in weight After the period of 45 minutes , the efficiency of 13,16% 3.1.1 Size Distribution Size distribution of nanosilica and modified nanosilica was expressed in Figure 3.2, in which nanosilica modified by 0–15 wt.% of KR-12 correspoding to U-SiO2, SiO2-KR.12 (5), SiO2-KR.12 (10) and SiO2-KR.12 (15), respectively Before being modified, the size distribution of silica (U-SiO2) was not homogeneous with large particles (the average particle size was found at 656.7 nm (72.7%) and5078 nm (27.3%)) due to the aggregation of nanosilicaparticles during storage When using titanate coupling agent to modify nanosilica, the size distribution after stirring and sonicating indicated the much smaller size than in the case of unmodified nanosilica The particle size of nanosilica has a tendency of reduction symmetrical arcording to the amount of titanate coupling agent KR-12 grafted onto nanosilica surface For nanosilica modified by wt.% of KR-12 (SiO2-KR.12 (5)), the average particle size was 408.8 nm(99.7%) and 4962 nm (0.3%), nanosilica-KR-12 (10), the particle size was decreased to 149.5 nm, and for nanosilica modified by 15 wt.% of KR-12 (SiO2-KR.12 (15)), there was only peak corresponding to size distribution by intensity peaks at 84.58 nm This demonstrated that the use of titanate coupling agent KR-12 plays important role in increasing the dispersiveness of nanosilica by reacting with hydroxyl groups on the surface to form a polymer layer preventing aggregation of nanosilica Surface modification followed by stirring and sonicating helps to decrease the size of the particles to the nano scale Flexural strength, MPa Flexural strength, MPa Tg, oC Temperature, oC Tg, oC Flexural strength, MPa Time, TBuT content, % TBuT content, % Figure 3.4 Influence of temperature (a), time (b), content of curing agent (c) on mechanical strength and glass transition temperature of epoxy-TBuT system 11 3.4 The effect of nanosilica on the kinetics and properties of the epoxy resin system cured by TBuT 3.4.1 Effect of m-nanosilica on the curing temperature of epoxyTBuT system The gel content (GC) of the cured epoxy–5 wt % m-silica–TBuT (EP–N5) nanocomposite was used to evaluate the effect of mnanosilica on the curing of epoxy chains by TBuT in the temperature range 80–180 oC It was obvious that the GC of the neat epoxy increased rapidly with increasing reaction temperature from 80 to 150 C This could have been caused by the energy supplied to the curing reaction of the neat epoxy, which was smaller than that at lower temperatures; thus, it was not sufficient for the curing reaction to take place completely This led to a lower network density and a lower GC of the cured neat epoxy The GC reached a highest value of 98.9% (near completely) at 150 oC and increased insignificantly at curing temperatures above 150 oC When wt % m-nanosilica was added into the epoxy resin (EP–N5), the GC of the cured EP–N5 nanocomposite increased rapidly with increasing reactiontemperature from 80 to 120 oC and reached a value of 98.4% Then, it was nearly constant at a reaction temperature of more than 150 oC 3.4.2 Active energy and kinetic of curing epoxy and epoxy/m-silica by TBuT The active energy (E) of the curing process of epoxy / TBuT, unmodified nanosilica/epoxy/ TBuT and epoxy/m-silica/TBuT were determined according to Flynn-Wall-Ozawa (3.1) and Kissinger (3.2) equation, from differential scanning calorimetry data The results are presented in Table 3.2 [ ( p ) p )   ) ] ( p 12 )=  p ) (3.1) ( ) (3.2)  Table 3.2 The active energy (E) of the curing process of epoxy/TBuT, unmodified nanosilica/epoxy/ TBuT and epoxy/msilica/TBuT Samples EFlynn-Wall-Ozawa EKissinger Eave Epoxy/TBuT Epoxy/5% unmodified nanosilica/TBuT Epoxy/5% mnanosilica/TBuT 69,614 66,171 67,893 63,3 59,75 61,53 52,87 48,94 50,91 When nanocomposite system using m-nanosilica, the activation energy of the system is significantly reduced This may be due to the catalytic effect of nanosilica for the epoxy curing reaction With unmodified nanosilica, the activation energy of the curing reaction decreased by 4.59 (kJ/mol), on the other hand, m-nanosilica nanosilica showing a significant decrease of the activation energy to 15.02 (kJ/mol) The reason due to the unmodified nanosilica particles have the phenomenon of coherence, so only a part exists in nano size with catalytic effect In case of m-nanosilica particles, they exist commonly in nano form with an average particle size of about 30 nm, so they have a larger catalytic effect, significantly reducing the activation energy of the curing reaction 3.4.3 Morphology of nanocomposite materials TEM images show that, when not modified, nanosilica particles are distributed in the aggregate state, with micron size m-nanosilicas are well dispersed in epoxy resins, the particles exist in the nanoscale with sizes in the range of 30 ÷ 60 nm When the content of mnanosilica is greater than 5%, (EP-N7 sample) shows the aggregation of some nanoparticles forming large clusters with the size of about 600 nm, corresponding to the state transition of the sample when not solidified from liquid to gel form This phenomenon is due to the high concentration of m-nanosilica, the gap between the nanoparticles is narrowed, which increases the interaction between them, resulting in agglomeration and gelatinization 13 Epoxy-unSiO2 Epoxy EP-N5 EP-N7 Figure 3.5 TEM image of epoxy/ m-nanoslica nanocomposite with different content of m-nanosilica 3.4.3 Effect of m-nanosilica content on tensile and flexural strength of epoxy / m-silica / TBuT nanocomposite materials: Mechanical strength was evaluate by impact strength and flexural strength, these factors can reflect the toughness of a material indirectly The result was shown in fig 3.6 As can be seen in fig (a) the impact strength of epoxy/silica nanocomposite was significantly increased with the addition of nanosilica particles As an increase in the nanosilica content to 5.0 wt%, the impact strength reached a maximum value 36.95 kJ.m-2 Similarrly, in fig (b) the flexural strength reached 116.6 MPa when the mass content of nanosilica was 5.0 wt%, which represented increase of 87.47% and 31.45% compared with that of pure epoxy resin The improved mechanical strength could be attributed to nanosilica particles were dispersed well into epoxy resin and the composite exhibited good interfacial bonding, during the fracture process of nanocomposite, the extener force dissipated to interfacial debonding between the nanosilica and 14 epoxy matrix, otherwise nanosilica particles promoted the generation of shear yielding Interfacial debonding combine with shear yielding consumed a large amount of energy during deformation then the nanocomposite displayed higher strength Flexural strength (MPa) 140 Impact strength (MPa) 40 30 20 10 120 100 80 60 40 20 0 Nanosilica content (wt%) 10 10 Nanosilica content (wt%) Figure 3.6 Impact strength (a) and flexural strength (b) of epoxy/silica nanocomposite 3.4.4 Fracture toughness and fracture energy of nanocompozit epoxy/m-nanosilica/TBuT Fracture toughness is a measure for the ability of a material to resist the growth of pre-existing cracks or flaws Figure 3.7 and the fracture toughness (KIC), fracture energy (GIC), modulus of elasticity (E), and Poisson’s ratio (µ) of neat epoxy and epoxy/m-nanosilica composites loading different m-nanosilica content 700 600 1,5 GIC (J/m2 ) KIC (MPa.m1/2 ) 2,5 0,5 500 400 300 200 100 0 10 Nanosilica content (wt%) 10 Nanosilica loading (wt%) Figure 3.7 Fracture toughness (KIC), fracture energy (GIC) of neat epoxy (a) and epoxy/m-nanosilica composites 15 In case of neat epoxy, the determined fracture toughness value was 1.06 MPa.m1/2, which correlates well with published literature for epoxy materials [2] The addition of m-silica nanoparticles into the epoxy matrix causes an increase in fracture toughness (KIC) of the composites and a maximum value of 1.73 MPa.m1/2 at 5.0 wt.% mnanosilica, which corresponds to a 91.51% increase in fracture toughness, compared with that of neat epoxy At higher nanosilica content, the enhancement in KIC epoxy/m-nanosilica was diminished and at wt % m-nanosilica, the KIC of composite was reduced to 1.45 MPa.m1/2 This can be also explained by agglomeration of msilica nanoparticles, the appearance of agglomerates in epoxy matrix reduced the effective volume fraction of m-silica nanoparticles and net surface area Therefore, the KIC of epoxy/m-nanosilica composite was reduced The relationship between elastic modulus (E) and fracture toughness (KIC) of the composites is reflected in the equation: GIC = [(1 - µ2)]/E, where µ is the Poison’s ratio, E value is obtained from the tensile test The fracture energy (GIC) quantifies the energy required to propagate the crack in the material Figure 4b indicated the GIC of neat epoxy was 243 J/m2, which typically shows relatively low values of the GIC for brittle polymers The incorporation of m-silica nanoparticles into the epoxy caused a significant increase in the composite’s GIC up to 660 J/m2 at 5.0 wt.% m-nanosilica, corresponding to 171.6% increase in fracture energy This improved critical energy release rate for the epoxy/m-nanosilica composites is comparable to that of tough polymers These results expressed the potency of m-silica nanoparticles in toughening of the epoxy resin 3.4.5 Effect of nanosilica on fire resistance and fire resistance mechanism of nanocomposite epoxy / m-nanosilica / TBuT The LOI of nanocomposite epoxy / m-nanosilica / TBuT materials depends on nanosilica content as shown in Figure 3.8 The results showed that the LOI value of the material increased 16 gradually with the increase of nanosilica content, the EP-N7 sample had the highest LOI value of 27.4, increasing by 1.21 times compared to the neat epoxy resin In the presence of m-nanosilica, the material's ability to inhibit combustion has increased significantly The cause of the increase in LOI is explained by the formation of a nanosilica layer on the combustion surface that prevents the penetration of oxygen into the material Figure 3.8 LOI of epoxy resin and nanocompozit epoxy/mnanosilica/TBuT SEM image of the nanocomposite and epoxy resin surface in Figure 3.9 shows that there is a tight layer of nanosilica on the surface of the sample after decomposition, the distribution of nanosilica particles is quite even with a size of about 30-80 nm, this layer of material prevents the subsequent permeability of oxygen and heat to decompose the polymers, so that nanocomposite has a LOI value higher than the neat epoxy resin The aggregation of particles creates a micron-sized structure EP-N1 EP-N5 17 EP-N7 EP-N0 Figure 3.9 SEM image of epoxy resin and nanocomposite surface after thermal decomposition 3.5 Fabrication and study of properties of epoxy/m-nanosilia/ TBuT/glass fiber composites 3.5.1 The effect of nanosilica on the mechanical properties of composite materials The effects of nanosilica on the mechanical strength of composites are shown in Table 3.3 The results showed that when adding m-nanosilica, the mechanical strength of epoxy/ TBuT glass fiber composites increased significantly The appropriate content of m-nanosilica is 5%, corresponding to an increase in tensile strength of 35.38%, a flexural strength of 15.68%, and an impact strength of 31.78% when compared to composite without m-nanosilica The reason is explained by the presence of nanosilica bond which will increase the bonding capacity of the resin and fiberglass to improve the mechanical strength of composites Table 3.3 Effect of m-nanosilica on mechanical strength of composites based on epoxy/nanosilica/glass fiber compozit Epoxy-nanosilica-glass fiber Fiber Tensile Flexural Impact glass Nanosilica strength, strength, strength, /resin content, % MPa MPa kJ/m2 60/40 281,3±9 315,7 141,0 60/40 332,8±6 348,0 157,41 60/40 357,5±7 353,1 165,13 60/40 380.9±7 365,2 185,81 60/40 313,9±5 289,4 153,11 18 3.5.2 Effect of reinforced fiber content on mechanical strength of composite materials Tensile strength, flexural strength and impact strength of composite materials are presented in Table 3.4 The results showed that these values of strength of composite increased when increasing the content of reinforced glass cloth and reached a maximum at 60% of mass, corresponding to increased tensile strength of 399.21% of flexural strength increased by 227, 24%, impact resistance increased by 402.87% when compared to epoxy resin The reason is explained by the fact that fiberglass has great strength and stiffness, so gradually replacing epoxy in composite will improve the tensile and bending strength of composite However, when exceeding 60% of the fabric, the amount of plastic is not sufficient to wet the fiber so the durability of the composite is reduced When compared with composites without reinforced nanoparticles, the presence of mnanosilica increased to 35.38% of the tensile strength value, 31.78% of flexural strength, impact strength increased by 31.78 This is due to the presence of nanosilica improves the adhesion interaction between the resin and the fiber until subjected to external forces, destructive stress will be evenly distributed in composites, base and reinforcement phases to maximize efficiency to increase mechanical Table 3.4 Mechanical strength of epoxy/m-nanosilica/TBuT composites/glass cloth depend on glass cloth content Mechanical properties of composite epoxy/mnanosilica/TBuT/glass fiber Conten Tensile Flexural Impact t fiber strength, strength, GIC, kJ/m2 strength, J/m (%) MPa MPa 76,3 ±4 111,6 ± 5,1 36,95±5,21 645 ± 11 30 164,6±5 189,1±4,3 161,62±4,13 664±10 40 246,7±9 212,5±9,2 167,34±5,26 729±9 50 341,5±8 303,4±6,4 173,78±3,35 965±15 60 380,9±7 365,2±9,3 185,81±5,16 1144±12 70 297,3±9 288,0±8,2 139,59 ±3,28 505±15 Compozit epoxy/glass fiber 60 281,35±1 315,7±12 141,03±5,43 845±11 19 3.5.3 Interlaminar fracture toughness of composite The result of interlaminar fracture toughness shows that at low fabric content 30 ÷ 40%, the GIP value of composite does not change much as compared to the original resin When increasing the fabric content to 50 ÷ 60% of the GIP value increases and reaches a maximum at 60% of the fabric, corresponding to the 1144 kJ/m2 tensile strength increased by 77.36% compared to the modified epoxy resin However, when increasing to 70% glass cloth, GIP decreased rapidly to 505 kJ/m2 The reason is explained by at the content of 50-60% of fiber, energy destroying epoxy resin, it also needs to destroy the adhesion interaction between epoxy-nanosilica resin and glass fiber, this process requires a lot of energy far more than the original epoxy resin, which increases layer separation strength When increasing to 70% of fibers, the small amount of plastic is not sufficiently wet to absorb the fiber surface, reducing the resin/fiber adhesion interaction, facilitating the propagation of cracks leading to the reduction of GIP value Figure 3.10 Influence of glass cloth content on the interlaminar fracture toughness of composites When compared with unmodified resins with the same fiber content, the GIP value of nanosilica composites significantly increased to 35.38%, K Thunhorst and Kinloh studies have shown 20 that in the presence of m-nanosilica increases the mechanical strength, destructive toughness of the nanocomposite system, and enhances the adhesion interaction with the glass fiber surface, leading to increased tensile destruction of nanosilica-containing samples, this allows to expand the application areas of epoxy resins 3.5.4 Influence of m-nanosilica on the dynamic mechanical properties of epoxy/ m-nanosilica/ TBuT / glass fiber composites The change of the storage modulus of the composite material with different fiber content is shown in Figure 3.11 The storage modulus of the material increases significantly and reaches its maximum at the V/N of 60/40 corresponding to the module E value increasesing of 588.59% compared to the base resin The increasing in module E 'value is due to the presence of reinforced glass with greater strength and stiffness than many polymers, and shows the uniform distribution of stress acting on the clear phases material, which means that there is a good adhesion interaction between the resin and reinforced fibers Figure 3.11 Dependence of storage module of composite with different glass fiber content on temperature The variation of the loss module depends on the temperature of the composite material shown in Figure 3.12 The results show that 21 the E value of the composite is much larger when compared to the original epoxy resin, this may be because when combined with the glass fiber, it restricts the recovery process of the material The maximum loss modulus of composites occurs at the glass transition temperature of the material Figure 3.12 Dependence on the loss modulus of composite on temperature Effect of m-nanosilica on tanδ of composite materials Figure 3.13 shows the change in tanδ depending on the temperature of composite with different reinforced fiber content The results showed that the tan of the composite material increased with the increase of temperature and reached the maximum value in the glass transition temperature zone, continued to raise the value of tanδ moved to the rubber state The tan tan of the composite is small when the content of fiberglass is much larger and bigger than the epoxy resin because in the composite, the glass fiber will be affected by most stresses, only a small area on the fiber at the dividing surface mixed with deformed plastic background Therefore the energy dispersion will occur mainly on the polymer substrate and at the plastic-fiber phase separation surface and is characterized by low energy dispersion 22 Nhiệt độ, oC Figure 3.13 Dependent dependence of composite samples with different glass fiber content on temperature CONCLUSION 1- Successfully couple KR-12 on nanosilica surface Have determined appropriate content of KR-12 was 15 %, with the coupling efficiency of 13,16 % After coupling KR-12, particle size of m-nanosilica substantially decrease 2- Nanosilica after being coupled with KR-12 (m-nanosilica) has good capability of dispersion in epoxy resin YD-128, with the content of 5%, the system remains liquid with dynamic viscosity at 25 oC of 803,823 cP m-nanosilica act to lower glass transition and phase transition heat of epoxy resin, when the content of mnanosilica is greater than 5%, Tg of epoxy resin increases 3- Appropriate conditions for curing reaction of epoxy YD-128 with tetrabutyltitanate are: temperature 150 oC; time: 180 mins; curing agent content: 15% Obtained product has tensile strength of 57,6 MPa; flexibility strength of 88,7 MPa; impact resistance of 19,71 kJ/m2, glass transition temperature of 121,1 oC Activation energy of curing reaction by TBuT Ea= 67,893 (kJ/mol) 4- m- nanosilica helps improve mechanical strength, durability, and thermal stability for epoxy resin, the resin after curing tends to change from brittle state into tough state Appropriate content of m23 nanosilica was %, obtained nano composite has tensile strength of 76,3 MPa (increases 33,5 % compared to epoxy resin); bending strength of 116,6 MPa (increases 31,2 %); impact resistance of 36,95 kJ/m2 (increases 87,47 %); critical stress intensity of 1,73 (increases 91,51 %); destroying energy GIC 660 kJ/m2 (increases 171,6 %) Using m-nanosilica makes thermal stability and flame restraint ability increase Using 5% m-nanosilica lower the activation energy of curing reaction an amount of 15,02 kJ/mol 5Successfully manufacture composite epoxy/mnanosilica/TBuT/glass fiber, with appropriate content of the fiber of 60%, using m-nanosilica helps improve mechanical strength Tensile strength of the composite epoxy/m-nanosilica/TBuT/60 % glass fiber increases 35,38 %, bending strength increases 31,78 % compared to the composite without m-nanosilica Fracture toughness GIP of the composite is maximum at 60% glass fiber (GIP is 1144 kJ/m2 increasing 77,36 % compared to modified epoxy, increasing 35,38 % compared to the composite without nanosilica) 24 25 ... Reviewer 1: ………………………… Reviewer 2: ………………………… Reviewer 3: ………………………… The thesis will be defended at the doctoral thesis committee at the Academy level, meeting at the Graduate University of Science... depending on the temperature of composite with different reinforced fiber content The results showed that the tan of the composite material increased with the increase of temperature and reached... means that there is a good adhesion interaction between the resin and reinforced fibers Figure 3.11 Dependence of storage module of composite with different glass fiber content on temperature