Preparation And Properties Of PMMA Transparent Blend Catalyzed By TFSI Organic Salt

Poly(methyl methacrylate)(PMMA)has a high surface hardness with low cost but low toughness and low refractive index.In contrast,PC exhibits exceptional toughness and high refractive index but lacks of surface hardness.PMMA and PC are compensable in physical properties.On the other hand,9,9-bis[4-(2-hydroxyethoxy)benzene]fluorene(BPEF)is a kind of"cardo"molecule in which benzene rings are in two perpendicular planes.The special molecular structure plays an important role in increasing the refractive index and reducing the birefringence of optical transparent materials.In this thesis,the structure and performance of PMMA/PC and PMMA/BPEF blend systems are systematically studied by using an organic salt with bis(trifloro-methanesulfonyl)imide(TFSI)as the transesterification catalyst by means of reactive processing.We focus on the transesterification catalysis of TFSI-based organic salts on the PMMA based transparent blends..The main research contents are as follows:(1)The effect of TFSI-based organic salts with different cations on PMMA/PC transesterification:The effects of TFSI organic salts with different cations on PMMA/PC(97/3)transesterification were investigated.The results show that different organic salts have different effects on PMMA/PC system.The effect of transparent modification in TFSI-based organic salts is Mg²⁺>Li⁺>TBOP⁺?Cs⁺.(2)The effect of Mg(TFSI)₂ on the structure and performance of PMMA/PC(50/50)blends:The effects of Mg(TFSI)₂ on the transparency and thermal properties of PMMA/PC(50/50)blends were studied by scanning electron microscopy(SEM),differential scanning calorimetry(DSC)and thermogravimetric analysis(TGA).The results show that after adding Mg(TFSI)₂,the island structure was transformed into homogeneous morphology,and the films changes into transparent material.The glass transition temperature and temperature at maximum thermal loss of PMMA/PC composite also change from two to one.The results of infrared spectroscopy(FTIR)and gel penetration chromatography(GPC)showed that a large number of PMMA-g-PC copolymers and the cross-linking networks were formed under the catalysis of Mg(TFSI)₂,and the blends became homogeneous blends.(3)The influence of PMMA/BPEF compatibility and performance:A series of PMMA/BPEF blends with different contents of BPEF were prepared by melting blending method.The compatibility between BPEF and PMMA and the physical properties of the blends were studied.The results show that the addition of BPEF has little effect on the light transmittance and haze of PMMA.PMMA and BPEF are thermodynamic compatible systems.Compared with pure PMMA,a small amount of BPEF can improve the Young's modulus and fracture strength of PMMA,and also improve the thermal stability of PMMA.(4)The effect of Mg(TFSI)₂ on the structure and properties of PMMA/BPEF:Mg(TFSI)₂ was added into PMMA/BPEF blend as transesterification catalyst,and the effects of Mg(TFSI)₂ on the transparency,mechanical properties and thermal properties of PMMA/BPEF were systematically studied.The results show that,for the thermodynamically compatible PMMA/BPEF blends,Mg(TFSI)₂ can promote the transesterification reaction between PMMA and BPEF,and increase the molecular weight and copolymer content of PMMA/BPEF.Compared with PMMA/BPEF binary blend without Mg(TFSI)₂,PMMA/BPEF/Mg(TFSI)₂ composite has higher glass transition temperature and maximum thermal weight loss temperature.