Comparison of the Properties of Epoxy Resins Containing Various Trifluoromethyl Groups with Low Dielectric Constant

A series of epoxy resins containing various trifluoromethyl groups were synthesized and thermally cured with diaminodiphenylmethane (DDM) and aminophenyl sulfone (DDS). All epoxy resins exhibited excellent thermal stability with the glass transition temperatures of above 128 °C and 5% weight loss temperatures of above 300 °C. DDS-cured epoxy resins possessed higher thermal stability than that of DDM-cured epoxy resins, while DDM-cured epoxy resins showed better mechanical, dielectric, and hydrophobic properties. Additionally, DDM-cured epoxy resins with different locations and numbers of trifluoromethyl groups showed flexural strength in the range of 95.55~152.36 MPa, flexural modulus in the range of 1.71~2.65 GPa, dielectric constant in the range of 2.55~3.05, and water absorption in the range of 0.49~0.95%. These results indicate that the incorporation of trifluoromethyl pendant groups into epoxy resins can be a valid strategy to improve the dielectric and hydrophobic performance.

Effects of graphene oxide size on curing kinetics of epoxy resin

To study the effects of graphene oxide (GO) size on the curing kinetics of epoxy resin (EP), two kinds of GO were selected and characterized by Fourier transform infrared spectrometry (FT-IR), FT-Raman spectrometry (FTIR-Raman), thermo gravimetric analysis (TGA), dynamic light scattering (DLS), transmission electron microscopy (TEM), X-ray diffractometry (XRD) and X-ray photoelectron spectroscopy (XPS). The results showed that the two kinds of GO had similar chemical structures but different sizes-the average particle size of GO-A was 190.1 nm and that of GO-B was 1510 nm, and GO-A has more oxidizing groups on its surface. The two kinds of GO were separately added to EP, and the curing kinetics of GO/EP composites and neat EP were investigated through differential scanning calorimetry (DSC). It can be seen that the addition of GO promoted the curing process of the EP system, and GO-A had a more significant catalytic effect. Furthermore, the curing activation energy (E a) was calculated by Kissinger model, and the change of E a in the whole curing reaction process was studied by Ozawa method to further understand the curing mechanism. It showed that the apparent E a of EP system increases with the increase of the conversion rate, and E a of EP-A is obviously lower in the early curing stage. However, as the curing reaction proceeds, E a of EP-B is a little lower than that of EP-A in the later curing stage. But EP-A has the lowest E a combined with the whole process from Kissinger method. To sum up, it can be concluded that the curing process of EP can be promoted by adding GO and the smaller size (190.1 nm) of GO had a greater effect and lower E a than the GO with particle size of 1510 nm. And the related mechanisms were discussed and analyzed.

α-Aminophosphonate Derivatives for Enhanced Flame Retardant Properties in Epoxy Resin

This work demonstrates the introduction of various α-aminophosphonate compounds to an epoxy resin system, thereby improving flame retardance properties. The α-aminophosphonate scaffold allows for covalent incorporation (via the secondary amine) of the compounds into the polymer network. This work explores the synergistic effect of phosphorus and halogens (such as fluorine) to improve flame retardancy. The compounds were all prepared and isolated in analytical purity and in good yield (95%). Epoxy samples were prepared, individually incorporating each compound. Thermogravimetric analysis showed an increased char yield, indicating an improved thermal resistance (with respect to the control sample). Limiting oxygen index for the control polymer was 28.0% ± 0.31% and it increased to 34.6% ± 0.33% for the fluorinated derivative.

A Fluorinated Thermocrosslinkable Organosiloxane: A New Low-k Material at High Frequency with Low Water Uptake

In order to obtain low-k material with good comprehensive properties, a trifluoromethyl-containing organosiloxane with thermocrosslinkable vinyl and benzocyclobutene groups is designed and synthesized through the Piers-Rubinsztajn reaction. After treating at high temperature, the organosiloxane changed to form a cross-linked polysiloxane (called as c-FSi-BCB). c-FSi-BCB exhibits good dielectric properties with dielectric constant (D_k ) of 2.60 and dielectric loss (D_f ) of 1.49 × 10^-3 at a high frequency of 5 GHz. Importantly, c-FSi-BCB maintains such good dielectric properties and exhibits low water uptake of below 0.076%, even after immersing it in boiling water for 96 h. c-FSi-BCB also displays good thermostability with a 5% weight loss temperature (T_5d ) of 453 °C. These data indicate that this fluorinated organosiloxane is suitable as the matrix resin for the fabrication of devices used in 5G communication.

Synthesis of a Flame Retardant and Hydrophobic Epoxy Resin with Multiple Elements Synergistic Effect for Tunnel Seepage Prevention Application

Epoxy resin (EP) mortar usually used to repair the cracking of concrete structure under damp environment, but EP is extremely flammable, thus it’s extremely imperative to design a novel multifunction EP grouting materials with flame retardancy and waterproofness for the practical application. Targeting ingenious decoration of EP grouting materials, multiple flame retardant elements (phosphorus, nitrogen and fluorine) are concurrently introduced into a fire retardant and the fire retardant defined as DDM-FNP. The obtained DDM-FNP/EP grouting composite possess high thermal stability, flame retardancy and hydrophobicity. The limiting oxygen index (LOI) value of DDM-FNP/EP composites has a significant improve, which is increased from 26.7 (EP-0) to 35.8 (EP-4). Composites with more than 10 wt% of DDM-FNP could pass UL-94 V-0 rating without dripping. Compared with EP-0, the PHRR and THR of EP-4 are decreased by 31.1% and 21.6%, respectively. In addition, due to the introduction of the F element, the water contact angle of EP composites is changed from 75.2° (hydrophilicity) to 98.6° (hydrophobicity) after the introduction of a certain amount of DDM-FNP flame retardant. Therefore, this work provide a new perspective to design a multifunction EP grouting composite and improve the value of practical application on seepage prevention of tunnel.

Preparation and properties of a novel fluorinated epoxy resin/DGEBA blend for application in electronic materials

A novel epoxy monomer 4-trifluoromethyl phenylhydroquinone epoxy resin (4-TFMEP) was synthesized via a multistep procedure including the Meerwein arylation reaction and followed by nucleophilic reaction. The chemical structure of 4-TFMEP was confirmed by proton nuclear magnetic resonance and Fourier-transform infrared spectrum. Then a mixed system (DGEBA/4-TFMEP x%) composed of diglycidyl ether of bisphenol A (DGEBA) and 4-TFMEP was prepared by a melting method without any solvent. After curing, the properties of this series of mixed epoxy resins were measured and compared with the neat DGEBA. As a result, the blend resins exhibited good thermal stability, excellent hydrophobic and low dielectric properties with 4-TFMEP content increasing. Furthermore, the material of DGEBA/4-TFMEP 40% achieves higher glass transition temperature of 104°C and char yield 33% than DGEBA (char yield = 22%) possessed. In the contact angle testing, DGEBA/4-TFMEP 40% shows 127.2° satisfied the standard of hydrophobic material. In addition, by the test of dielectric properties, DGEBA/4-TFMEP x% materials show lower than DGEBA/boron trifluoride ethylamine (BF3MEA) material, because of the introduced side group of fluorine content into the material improves the electronegativity of epoxy material and reduced the polarizability of molecules efficient. Herein, we believe the novel mixed epoxy system (DGEBA/4-TFMEP x%) has a potential application in electronic industries.

Research on the thermal conductivity and dielectric properties of AlN and BN co-filled addition-cure liquid silicone rubber composites

The present work aims at studying the thermal and dielectric properties of addition-cure liquid silicone rubber (ALSR) matrix composites using boron nitride (BN) and aluminum nitride (AlN) as a hybrid thermal conductive filler. Composite samples with different filler contents were fabricated, and the density, thermal conductivity, thermal stability, dielectric properties, and volume resistivity of the samples were measured. According to the experimental results, the density, thermal conductivity, dielectric constant and dielectric loss tangent values all increased with the increasing addition of filler. When the weight fraction of hBN filler was 50 wt%, the thermal conductivity of composites was 0.554 W (m-1 K-1), which is 3.4 times higher than that of pure ALSR. The corresponding relative permittivity and dielectric loss were 3.98 and 0.0085 at 1 MHz, respectively. Furthermore, TGA results revealed that the AlN/BN hybrid filler could also improve the thermal stability of ALSR. The volume resistivity of ALSR composites was higher than that of pure ALSR. The addition of fillers improved the thermal properties of ALSR and had little effect on its insulation properties. This characteristic makes ALSR composites attractive in the field of insulating materials.

Investigation on cure kinetics of epoxy resin containing carbon nanotubes modified with hyper-branched polyester

The cure kinetics of epoxy resin cured by diethyltoluene diamine (D-EP), D-EP/multi-walled carbon nanotube (D-EP/CNT) composites and D-EP/hyper branched polyester functionalized CNTs (D-EP/CNTs-H20) were investigated by non-isothermal differential scanning calorimetry (DSC). Results revealed that the presence of CNTs shifted the cure temperature to a lower temperature and accelerated the curing of D-EP, and the addition of CNTs-H20 exhibited a stronger effect in accelerating the cure of D-EP. Activation energies were calculated based on the Kissinger approach and Ozawa approach respectively. Lowered activation energy was observed after the addition of CNTs or CNTs-H20 at low degrees of cure, indicating that the CNTs had a large effect on the curing reaction. The presence of CNTs facilitated the curing reaction, especially the initial epoxyamine reaction. Moreover, CNTs-H20 exhibited better performance. The autocatalytic model was used to describe the cure kinetics phenomena of the studied systems. When CNTs or CNTs-H20 were added, the Sesták–Berggren model still can describe the cure kinetics of the D-EP composites because the results, calculated by the model, agreed with the experimental data well. Moreover, the kinetics parameters as well as the equation describing the cure process were proposed.

The cure kinetics of epoxy resin cured by D-EP, D-EP/CNT composites and D-EP/CNTs-H20 were investigated by non-isothermal differential scanning calorimetry (DSC).