Liquid crystalline epoxy resin based on biphenyl mesogen: Thermal characterization

Synthesis of SiO2 Nanoparticle Epoxy Resin Composite and Silicone-Containing Epoxy Resin for Coatings

Due to its unique properties, including strong adhesion force, high heat resistivity, high insulation properties, and strong mechanical properties, epoxy resin is the most commonly used material for a variety of applications, including adhesives, electronic devices for coatings, and somewhere as a matrix for reinforcement of composites as a fiber network. To boost their properties, different other materials are also inserted in their structure and made its composites; silicon is one of them. Corrosion is serious for marine equipment and causes economic loss. To overcome such issues, different types of coating materials are developed. In this review, current methods for coatings of different materials using a silicon dioxide epoxy nanocomposite are discussed in diversity with the currently followed synthetic routes for the preparation of nanosilica epoxy composites and enhanced properties.

Advances in Liquid Crystalline Epoxy Resins for High Thermal Conductivity

Epoxy resin (EP) is one of the most famous thermoset materials. In general, because EP has a three-dimensional random network, it possesses thermal properties similar to those of a typical heat insulator. Recently, there has been substantial interest in controlling the network structure of EP to create new functionalities. Indeed, the modified EP, represented as liquid crystalline epoxy (LCE), is considered promising for producing novel functionalities, which cannot be obtained from conventional EPs, by replacing the random network structure with an oriented one. In this paper, we review the current progress in the field of LCEs and their application to highly thermally conductive composite materials.

Tetrafunctional Epoxy Resin-Based Buoyancy Materials: Curing Kinetics and Properties

In order to synthesize a new kind of buoyancy material with high-strength, low-density and low-water-absorption and to study the curing reaction of tetraglycidylamine epoxy resin with an aromatic amine curing agent, the non-isothermal differential scanning calorimeter (DSC) method is used to calculate the curing kinetics parameters of N,N,N′,N′-tetraepoxypropyl-4,4′-diaminodiphenylmethane epoxy resin (AG-80) and the m-xylylenediamine (m-XDA) curing process. Further, buoyancy materials with different volume fractions of hollow glass microsphere (HGM) compounded with a AG-80 epoxy resin matrix were prepared and characterized. The curing kinetics calculation results show that, for the curing reaction of the AG-80/m-XDA system, the apparent activation energy increases with the conversion rates increasing and the reaction model is the Jander equation (three-dimensional diffusion, 3D, n = 1/2). The experimental results show that the density, compressive strength, saturated water absorption and water absorption rate of the composite with 55 v % HGM are 0.668 g·cm⁻³, 107.07 MPa, 0.17% and 0.025 h^−1/2, respectively. This kind of composite can probably be used as a deep-sea buoyancy material.

Liquid crystalline networks based on photo-initiated thiol-ene click chemistry

Photo-initiated thiol-ene click chemistry is used to develop shape memory liquid crystalline networks (LCNs). A biphenyl-based di-vinyl monomer is synthesized and cured with a di-thiol chain extender and a tetra-thiol crosslinker using UV light. The effects of photo-initiator concentration and UV light intensity on the curing behavior and liquid crystalline (LC) properties of the LCNs are investigated. The chemical composition is found to significantly influence the microstructure and the related thermomechanical properties of the LCNs. The structure-property relationship is further explored using molecular dynamics simulations, revealing that the introduction of the chain extender promotes the formation of an ordered smectic LC phase instead of agglomerated structures. The concentration of the chain extender affects the liquid crystallinity of the LCNs, resulting in distinct thermomechanical and shape memory properties. This class of LCNs exhibits fast curing rates, high conversion levels, and tailorable liquid crystallinity, making it a promising material system for advanced manufacturing, where complex and highly ordered structures can be produced with fast reaction kinetics and low energy consumption.

Curing and Characteristics of N,N,N',N'-Tetraepoxypropyl-4,4'-Diaminodiphenylmethane Epoxy Resin-Based Buoyancy Material

Buoyancy material is a type of low-density and high-strength composite material which can provide sufficient buoyancy with deep submersibles. A new buoyancy material with N,N,N',N'-tetraepoxypropyl-4,4'-diaminodiphenylmethane epoxy resin (AG-80) and m-xylylenediamine (m-XDA) curing agent as matrix and hollow glass microsphere (HGM) as the filler is prepared. The temperature and time of the curing process were determined by the calculations of thermal analysis kinetics (TAK) through differential scanning calorimetry (DSC) analysis. The results show that the better mass ratio of AG-80 with m-XDA is 100/26. Combined TAK calculations and experimental results lead to the following curing process: pre-curing at 75 °C for 2 h, curing at 90 °C for 2 h, and post-curing at 100 °C for 2 h. The bulk density, compressive strength, and saturated water absorption of AG-80 epoxy resin-based buoyancy material were 0.729 g/cm³, 108.78 MPa, and 1.23%, respectively. Moreover, this type of buoyancy material can resist the temperature of 250 °C.

Enhanced Thermal Conductivity of Liquid Crystalline Epoxy Resin using Controlled Linear Polymerization

A powerful strategy to enhance the thermal conductivity of liquid crystalline epoxy resin (LCER) by simply replacing the conventional amine cross-linker with a cationic initiator was developed. The cationic initiator linearly wove the epoxy groups tethered on the microscopically aligned liquid crystal mesogens, resulting in freezing of the ordered LC microstructures even after curing. Owing to the reduced phonon scattering during heat transport through the ordered LC structure, a dramatic improvement in the thermal conductivity of neat cation-cured LCER was achieved to give a value ∼141% (i.e., 0.48 W/mK) higher than that of the amorphous amine-cured LCER. In addition, at the same composite volume fraction in the presence of a 2-D boron nitride filler, an approximately 130% higher thermal conductivity (maximum ∼23 W/mK at 60 vol %) was observed. The nanoarchitecture effect of the ordered LCER on the thermal conductivity was then examined by a systematic investigation using differential scanning calorimetry, polarized optical microscopy, X-ray diffraction, and thermal conductivity measurements. The linear polymerization of LCER can therefore be considered a practical strategy to enable the cost-efficient mass production of heat-dissipating materials, due to its high efficiency and simple process without the requirement for complex equipment.

Highly thermal conductive resins formed from wide-temperature-range eutectic mixtures of liquid crystalline epoxies bearing diglycidyl moieties at the side positions

Liquid crystalline epoxy resins with a wide temperature range exhibit a high thermal conductivity of 0.4 W m⁻¹ K⁻¹.

Star-epoxy mesogen with 1,3,5-triazine core: a model of A4B3fractal polymerization in a liquid crystalline thermoset media

Synthesis of a star-epoxy monomer and design of a hierarchically organized thermoset involving both fractal and discotic mesogen self-assembly.

Preparation of a P(THF-co-PO)-b-PB-b-P(THF-co-PO) triblock copolymer via cationic ring-opening polymerization and its use as a thermoset polymer

Triblock copolymer P(THF-co-PO)-b-PB-b-P(THF-co-PO) with gradient copolyether segments was synthesized, and its elastomer exhibited excellent dynamic mechanical properties.

Relationship between crosslinking structure and low dielectric constant of hydrophobic epoxies based on substituted biphenyl mesogenic units

In this work, a series of low dielectric constant hydrophobic epoxies based on substituted biphenyl mesogenic were prepared and characterized.

Modification of Urushiol Derivatives by Liquid Crystal Epoxy Resin

Urushiol derivatives have vast potentials for using as coating materials. However, the cured coatings are quite brittle, limiting their applications. In this study, urushiol-furfural (UFUR) was chosen as an example of urushiol derivatives and a liquid crystal (LC) epoxy resin, tetramethylbiphenyl diglycidyl ether (TMBPDE), was for the first time utilized to modify UFUR. Fourier transform infrared spectroscopy and solid-state13C nuclear magnetic resonance showed the reactions between TMBPDE and UFUR after the UFUR/TMBPDE composite resin was cured. Differential scanning calorimetry analysis showed that theTgsignificantly increased after the addition of TMBPDE. Thermogravimetry analysis indicated that the cured UFUR/TMBPDE composite resin exhibited increasing thermodecomposition temperature as the TMBPDE concentration increased, indicating its great potential for high temperature applications. Moreover, the presence of TMBPDE enhanced the toughness of UFUR as observed by impact test and reflected in the morphologies observed from SEM images of fracture surfaces. It would also be novel and effective to modify urushiol derivatives by the LC polymer.

High thermo-responsive shape memory epoxies based on substituted biphenyl mesogenic with good water resistance

In this work, a novel epoxy monomer denoted as 3,5′-di-t-butyl-5,3′-dimethyl biphenyl diglycidyl ether was synthesized and applied intoin situcomposites with 3,3′,5,5′-tetramethyl-4,4′-biphenyl diglycidyl ether, accompanied with curing agent aromatic amines.

Thermomagnetic processing of liquid-crystalline epoxy resins and their mechanical characterization using nanoindentation

A thermomagnetic processing method was used to produce a biphenyl-based liquid-crystalline epoxy resin (LCER) with oriented liquid-crystalline (LC) domains. The orientation of the LCER was confirmed and quantified using two-dimensional X-ray diffraction. The effect of molecular alignment on the mechanical and thermomechanical properties of the LCER was investigated using nanoindentation and thermomechanical analysis, respectively. The effect of the orientation on the fracture behavior was also examined. The results showed that macroscopic orientation of the LC domains was achieved, resulting in an epoxy network with an anisotropic modulus, hardness, creep behavior, and thermal expansion.