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Synthesis, Curing and Mechanical Properties of a Liquid Crystalline Epoxy with Biphenol and Aromatic Ester Group

Author: LiuYinLing
Tutor: CaiZhiQi
School: South China University of Technology
Course: Applied Chemistry
Keywords: Liquid crystalline epoxy resins (LCER) Synthesis Curing reaction Mechanical properties Thermal properties
CLC: TQ323.5
Type: Master's thesis
Year: 2011
Downloads: 113
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Abstract


In recent years, liquid crystalline epoxy resin (LCER) has gained considerable interests. Many groups have studied the synthesis, curing behavior, optical properties, and mechanical properties of LCERs.This article describes a high efficient and economical method to synthesize a LCER containing biphenol and aromatic ester group, 3,3’,5,5’-tetramethylbiphenyl-4,4’-diyl bis(4-(oxiran-2-ylmethoxy) benzoate) (DGE-TMBPBHB). Firstly 3,3’,5,5’-tetramethylbiphenyl-4,4’-diylbis (4-hydroxybenzoate) was prepared by direct esterification of 3,3’,5,5’-tetramethylbiphenyl-4,4’-diol with p-hydroxybenzoic acid in the presence of a certain amount of p-toluene sulfonic acid (p-TSA) as catalyst. And then target monomer was synthesized by the reaction of precursor with epichlorohydrin. The chemical structure, melting range and liquid crystalline phase transition behavior of DGE-TMBPBHB were characterized by FT-IR, 1H-NMR, 13C-NMR, mass spectroscopy, differential scanning calorimetry (DSC) and polarized optical microscopy (POM).DGE-TMBPBHB was synthesized and its thermal properties were studied by differential scanning calorimetry (DSC) and polarized optical microscopy (POM). Thermal history markedly affected liquid crystalline (LC) phase behaviors. The peak values of the isotropized temperature (Ti), crystallized temperature (Tc) and enthalpy change (ΔHi) caused by the transition from the LC phase to the isotropic state of DGE-TMBPBHB decreased slightly during repetitive heat-cool cycles. Two Liquid crystalline thermosets were prepared based on the epoxy monomer with two different curing agents, 4,4’-diaminodiphenyl methane (DDM) and 4,4’-diaminodiphenyl sulfone (DDS), respectively. Cure kinetics of mixtures of DGE-TMBPBHB/DDM and DGE-TMBPBHB/DDS were investigated by DSC under nonisothermal processes.Liquid crystalline epoxy thermosets were prepared by adding DGE-TMBPBHB into diglycidylether of bisphenol A (DGEBA)/4,4’-diaminodiphenyl methane (DDM) blends. DGE-TMBP was added to DGEBA/DDM to produce thermosets for comparison. The influences of the concentration and chemical structure on the mechanical and thermal properties were investigated systematically. The DGE-TMBPBHB /DGEBA blends possessed increased rubbery plateau modulus, higher glass transition temperatures and lower tanδ. The use of small amounts of DGE-TMBPBHB may improve the mechanical properties greatly. Izod notched impact strength could be enhanced by 55% by addition of 2% DGE-TMBPBHB compared to unmodified DGEBA blends. Extremely rough and highly deformed fracture surface could be obtained in the DGE-TMBPBHB /DGEBA blends. DGE-TMBPBHB /DGEBA blends also exhibited excellent thermal properties.

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CLC: > Industrial Technology > Chemical Industry > Synthetic resins and plastics industry > Polycondensation resin and plastic > Epoxy resins and plastics
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