| 2012th Postgraduates |
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Title: Preparation of Carbon Fiber Reinforced Epoxy Composite Modified by Polyamic Acid Writer: Yong Liu Supervisor: Wei Wu Abstract:In this paper, the epoxy E-51 and CYD-011 were blended as the matrix resin with the ratio of 1:1, and the polyamic acid which is the processor of polyimide was used as the modifier. The epoxy resin was modified by polyamic acid followed by the preparation of carbon fiber reinforced epoxy composites at the first time. The pre-reaction of the epoxy and polyamic acid was study by Fourier Transform Infrared Spectroscopy (FTIR), the curing behaviors including the curing temperature, curing rate and curing activation energy of epoxy resin systems were studied by Differential Scanning Caborimetry (DSC), the effects of polyamic acid on the mechanical properties including the impact strength, the tensile strength and modulus, the flexural strength and modulus were studied at the same time. The results show that, by adding polyamic acid into the epoxy and after the pre-reaction, the initial curing temperature of the epoxy/DDS systems was decreased about 55.7℃, the gel-time of the resin system shorten about 72% when compare with the resin without modifying, the activation energy of the resin was lowered about 15.6KJ/mol, and the ability of thermal resistance for the resin was increased to some extent. As for the mechanical properties for the modified resin system, the impact strength of the resin with 2wt% polyamic acid was increased about 190%, the plain strain fracture toughness was increased 56% and the flexural strength was increased about 15% comparing with the resin without polyamic acid. Then the modified resin was used to prepare the carbon fiber reinforced epoxy composite through the solution method. The mechanical properties of composite laminates were conducted by tensile test machine. The test results show that the flexural strength of the composites laminates made by the modified resin matrix was increased 47.5%, the inter-laminar shear strength was increased about 33.5%, and the initial inter-laminar delamination strength was increased about 250%. The mechanism of the modification of polyamic acid to epoxy resin matrix and composite were also analyzed and the formation of semi-IPN structure was proposed to be the main reason for the improvement.
Title: Preparation and Properties Research of Carbon Fiber Reinforced Epoxy Resin Prepreg and Composites Writer: Mingchang Liu Supervisor: Wei Wu Abstract:Based on solid and liquid epoxy resin system for resin matrix composite, liquid epoxy resin E-51, solid epoxy resin CYD-011 and curing agent 4, 4’-Diaminodiphenylsulfone (DDS) were chosen as the matrix resin component, and the carbon fiber reinforced epoxy resin pre prepreg preparation and properties of its composite were researched. According to the hot melt film preparing prepreg’s requirements, when each component mass ratio was: epoxy resin E-51: epoxy resin CYD-011: DDS = 50:50: 22.58 and could be obtained the resin film with certain strength and toughness, and could be bent without breaking. The results showed that resin quality content of prepreg being 40% was preferred, and when curing process was: curing temperature-time being 140℃/2h+160℃/2h+180℃/2h, pressure being 0.4~0.6MPa, pressure point being 140℃/1h, carbon fiber reinforced epoxy resin composite mechanical properties were optimal, and flexural strength was 1478Mpa and interlaminar shear strength was 82MPa. In this paper, the experimental data for characterizing and the curing kinetics for E-51/CYD-011 epoxy resins were determined using a DSC isothermal scan method and isothermal curing kinetics parameters were obtained through fitting between the experimental data and the curing models. The reaction process shows to be dominated by a different mechanism at different stages of the E-51/CYD-011 system curing process: when the cure degree was less than 0.5, the curing system was an autocatalytic reaction model; when the cure degree was more than 0.5, the curing system was an nth order reaction model, with an initial autocatalytic reaction shifting into an nth order reaction as the reaction proceeding. After the change, the reaction activation energy decreased.
Title: Preparation and Performance Research for Carbon Fiber Reinforced Polyethylene Terephthalate Composite Writer: Pinpin Shi Supervisor: Wei Wu Abstract:In this paper, PET and SCF with 2mm length were chosen to prepare for PET/SCF composites by melt extrusion processing. The optimum process conditions were obtained through experiments, and we studied SCF content and the surface treatment influence on the properties of composites. Research showed that tensile strength, flexural strength, flexural modulus was increased with increased SCF content expect impact strength and meltfludity which increased first and then decreased. Addition of SCF brought faster crystallization and better thermostability. Concentrated nitric acid, silane coupling agent, titanate coupling agent were used to treat carbon fiber surface. When carbon fiber was treated with concentrated nitric acid and silane coupling agent, the composite has the best mechanical properties. Results showed that when carbon fiber surface was treated, the tensile strength of the composite increased 15%, while the flexural strength increased 22%, the flexural modulus increased 15%, the impact strength increased 13%, and the hardness increased 10%. Carbon fiber surface treatment had no influence on the thermostability of the composite and brought faster crystallization. The meltfludity and the usability of the composite also improved after carbon fiber surface treatment. Abstract:
Title: Preparation and Performance Research of Long-shelf life and low temperature Carbon Fiber/ Epoxy Resin for Hot-melt Prepreg Writer: Xiang Wu Supervisor: Wei Wu Abstract:In this paper, with the combination system of the solid and liquid bisphenol A epoxy reisn for resin matrix, MNA as curing agent, BTEAC commonly used for phase transfer catalyst and cationic surfactants as accelerator, carbon fiber as strength material, the long shelf life and low temperature prepreg was prepared by the hol-melt route. The effect of the content of curing agent and accelerator on the film property, the viscosity-temperature characteristics, curing temperature and shelf life at RT was investigated by the DSC and rotational rheometer.The results show that the formula involves epoxy resin/curing agent/accelerator with mass proportion of 100/48～51/1.5～2.The epoxy resin film prepared by this system can be cured at 85℃, have excellent film forming properties and shelf life at RT for 8days. The carbon fiber/epoxy resin prepreg was prepared by the carbon fiber and epoxy resin film obtained by optimized epoxy resin formula. The effect of hot roller temperature, pressing times and line speed on the prepreg impregnation were investigated. The results show that the impregnation effect was the best , and the physical properties of prepreg is uniform and stable when the hot roller temperature was 65℃～70℃, line speed was 3m/min～4m/min, pressing times was 13times～17times. The unidirectional composites laminates were prepared by the moulding process. The mechanical properties, water absorption, hygroscopicity and fracture morphology were studied. The results show that the composites had excellent mechanical performance, such as flexural strength was 1025MPa, interlaminar shear strength was 70MPa. The composites had good interface bonding performance, low water absorption and low hygroscopicity.
Title: Research on Development and Industrialization of Environmentally friendly Flame Retardant ABS Resin Writer: Xiuling Zhang Supervisor: Wei Wu Abstract:The research on the development and industrialization of environmentally friendly flame retardant ABS resin is described in this thesis which gives solutions to the technical issues of the ABS flame retarding modification and the industrialized production of the modified ABS resin. This thesis mainly focuses on the following aspects: The process principle and flame retarding principle of the ABS production; the flame retarding modification technique of general ABS 0215A; the production technology and the industrialization of the modified product. Based on the ABS plant of Jilin Petrochemical Company, using pilot scale twin-screw extruder research and develop the flame retardant ABS by adjusting the ratio of ABS and SAN powder and adopting the bromide flame retardant complies with ROSH legislation formulated by antimony trioxide as flame retarding system. The result proves that the UL-94 can achieve V-0 class when Br content is higher than 8%; the increase of Sb2O3 content can enhance the flame retarding effect but drop the impact strength and by experiment the ratio between Sb2O3 and Br is set at 1:2; TBBPA flame retardant has excellent flow ability at ABS molding temperature and becomes lubricant between ABS molecules and by adopting it in the development of flame retardant ABS can not only reduce energy consumption but also improve production efficiency; High emulsion power is the preferred toughening agent of flame retardant ABS due to its excellent toughening property; It is proved by experiment that the flame retardant ABS has features of wide-range process capability, stable tensile and flexible strength under different processing conditions and the impact strength can be enhanced by adjusting the screw rotation speed to an appropriate value with the same feeding rate. The stability test result indicates that the process requirement for pilot scale production is as following: extruding temperature: 180℃；Screw rotation rate: 220-240rpm; Feeding rate: 90Kg/hr (Note: To avoid the melting product blocking the feed inlet, the extruder feed inlet temperature should be set at 170 ℃). The production process parameters are stable and ease to control, product owns high standard of quality and stability whose impact strength and distortion temperature etc. are markedly higher than the expected parameters. The industrialized production can be implemented.
Title: Preparation and Study of Thermoreversible Multiple Hydrogen-Bonding Supramolecular Polymer Writer: Yujie Chen Supervisor: Wei Wu Abstract:In this thesis, new thermorebersible multiple hydrogen-bonding supramolecualr polymers are designed and synthesized from the concept that multiple hydrogen- bonding supramolecular elastomers with physical network structure are assembled from small molecules or oligomers associated by hydrogen bonds. Hydrogen-bonding supramolecular polymers are successfully prepared by one-pot synthesis from a series of amide and end-capped amide oligomer assembled by multiple hydrogen bonds between chains. Molecular structure, molecular weight and distribution, as well as mechanical, crystallization and melting, thermal decomposition, thermoreversible and processing, rubber-like, dynamical rheological properties are well characterized. The mode for phase transition, chain dynamics, hydrogen-bonding thermodynamics and assembling mechanism of multiple hydrogen-bonding supramolecular polymers are proposed and discussed in this thesis. Amide oligomer BX-1-EAH and end-capped amide oligomers BX-1-EAH-PTSI and BX-4-EAH-PTSI are synthesized from the condensation polymerization of dimer fatty acid (DFA) and anhydrous ethylene diamine (EAH) and then end-capped reaction by adding to p-toluenesulfonyl isocyanate (PTSI) with variable kinds of dimer fatty acid (BX-1 and BX-4) and contents of isocyanate. At cooling of products, oligomer chains assemble to physical network hydrogen-bonding supramolecular polymer by multiple hydrogen-bonding connections between chains. 1H-NMR and FT-IR analyses conform that amidation reaction and isocyanate end-capped reaction are successful and multiple hydrogen bonds of CO······NH, S=O······NH between amide and sulfonyl urea groups exist in the hydrogen-bonding supramolecular assembly which indicates the hydrogen-bonding physical network structure of supramolecular polymer. GPC and ESI-TOF-MS characterization show that amide oligomers have low molecular weight and wide molecular weight distribution and polymerization degree of the three oligomers is below 10. Highest ensile strength 13.2 MPa and ball indentation hardness 20.3 N/mm2 indicate that hydrogen-bonding supramolecular polymers have excellent mechanical properties. When molar ratio of EAH and DFA is 1.2: 1, tensile strength and elongation reach the highest value. Hydrogen-bonding supramolecular polymer with BX-4 as starting materials has 3.2% indissoluble gel and more chemical crosslinking micro-region from branching, and has higher tensile strength modulus and hardness. Physical network and chemical crosslinking micro-region coexist in hydrogen- bonding supramolecular polymers. DMA results indicate that at low temperature (< -30°C) hydrogen-bonding supramolecular polymers behave like hard plastic at glass state and the glass transition is at around 10 °C. Products show high-elastic properties between Tg and room temperature and rubber-like behavior at room temperature. DSC and WXRD results indicate the low melt temperature (88-100°C) and degree of crystalline (ΔHm = 8.5-12.5J/g); TGA show the excellent thermal stability of supramolecular polymer and the 10% decomposition temperature (Td10) is > 340 °C. The materials have good thermoreversible behavior, hence the moulding process can be operated on general melting mouldling processing equipments. Force-free tensile test indicates that the hydrogen-bonding supramolecular polymers behave like soft rubber with delayed recovery and show rubber-like elasticity between Tg and Tm. Rotational rheological characterization indicates that the melt of hydrogen- bonding supramolecuar polymer behaves like non-linear Bingham flow with very high yield stress. Hydrogen-bonding supramolecular assembly has multi phases including dynamic lamellar ordered phase and 3D network disordered phase with heterogeneous chemical crosslinking micro-regions. Rubber-like solid-liquid transition is at Tc1≈ 90°C, and liquid-liquid transition of micro-phase separation is at Tc2. Associate-disassociate mechanism of physical interaction and reptation mechanism have cooperatively effect on the relaxation of hydrogen-bonding supramolecular polymer. The mean time of relaxation decreases and the zero shear viscosity with the increase of temperature. At high temperature, the density of hydrogen bonds between oligomer chains is very low, and the system behaves like liquid with low viscosity; at cooling, the hydrogen-bonding density increases, molecular chains assemble by multiple hydrogen-bonding and the order degree of chains increases; viscosity and storage modulus of the system suddenly increases at around 90°C, and the supramolecular polymer has liquid-solid transition; below 90°C, a few dynamic ordered lamellar structures form in the 3D hydrogen-bonding networks, and until room temperature, hydrogen-bonding supramolecular polymer behaves like viscoelastic solid with low crystalline and good mechanical properties. At the heating and cooling cycles, physical cross-linking networks are destroyed and reformed, therefore, the assembling process from hydrogen-bonding is reversible.
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