Development of Novel Functionalized Aryl Cyanate Ester Oligomers. 1. Synthesis and Thermal Characterization of the Monomers

Fast pyrolysis bio-oil from lignocellulosic biomass for the development of bio-based cyanate esters and cross-linked networks

Fast pyrolysis of pine wood was carried out to yield a liquid bio-oil mixture that was separated into organic and aqueous phases. The organic phase (ORG-bio-oil) was characterized by gas chromatography–mass spectroscopy, 31P-nuclear magnetic resonance spectroscopy, and Fourier transform infrared (FTIR) spectroscopy. It was further used as a raw material for producing a mixture of biphenolic compounds (ORG-biphenol). ORG-bio-oil, ORG-biphenol, and bisphenol-A were reacted with cyanogen bromide to yield cyanate ester monomers. Cyanate esters were characterized using FTIR spectroscopy and were thermally cross-linked to develop thermoset materials. Thermomechanical properties of cross-linked cyanate esters were assessed using dynamic mechanical analysis and compared with those of cross-linked bisphenol-A-based cyanate ester. ORG-biphenol cyanate ester was observed to have a superior glass transition temperature (350–380°C) as compared to bisphenol-A cyanate ester (190–220°C). Cyanate esters derived from bio-oil have the potential to be a sustainable alternative to the bisphenol-A-derived analog.

High-Performance Thermoset–Thermoset Polymer Blends: A Review of the Chemistry of Cyanate Ester–Bismaleimide Blends

Various blends of a commercial bismaleimide (BMI) mixture, a cyanate ester (CE) and a co-monomer with allyl and cyanate pendant groups were formulated and cured. Differential scanning calorimetry (DSC) data were used to monitor the cure of neat resins, while dynamic mechanical thermal analysis (DMTA) was used to assess cure by the measurement of glass transition temperatures ( Tg). It is suggested that following cyclotrimerization of the CE component, the co-reaction between allyl CE and BMI occurs via an ‘ene’/Diels–Alder mechanism (to form linked interpenetrating networks, LIPNs) as evidenced by 13C nuclear magnetic resonance (NMR) spectroscopy. DMTA reveals that, unlike the commercial CE/BMI blends, the cured LIPNs may display a single Tg value which may exceed 350°C depending on the co-monomers used.

The effect of functionalized benzoxazine with allyl groups on the dielectric, mechanical and thermal properties of BMI/BADCy composites

The incorporation of functionalized benzoxazine with allyl groups into BMI/BADCy composites can induce an interpenetrating network (IPN) structure and the fracture surface will change from a riverlike shape to a ductile sunken shape.

Synthesis of a phosphinated tetracyanate ester and its miscible blend with 4,4′-oxydianiline/phenol-based benzoxazine

A phosphinated tetracyanate ester (4) was prepared and applied to copolymerize with a 4,4′-oxydianiline/phenol-based benzoxazine (P-oda) to enhance the properties of P-oda thermoset.

The effect of bis allyl benzoxazine on the thermal, mechanical and dielectric properties of bismaleimide–cyanate blend polymers

A high-performance polymer composite was fabricated using Bz-allyl/BMI/BADCy resin, in which the BMI/BADCy resin was modified with Bz-allyl to improve its dielectric, thermal and mechanical properties and the cross-linking degree after curing.

High-temperature matrix resins based on bispropargyl ethers (BPEs) – part 2

Structurally diverse bispropargyl ethers (BPEs) using resorcinol, quinol, 4,4′-dihydroxy biphenyl, bisphenol-A, 4,4′-dihydroxy diphenyl ketone, 4,4′-dihydroxy diphenylsulphone, trimethyl indane bisphenol and tetramethyl spirobiindane bisphenol were synthesized, and it was separately blended with 4,4′-bismaleimido diphenyl methane (BMIM) in mole ratios (0.5:0.5). The structural characterizations of the materials are carried out using Fourier transform infrared and nuclear magnetic resonance studies. Differential scanning calorimetric analysis shows that the difference in the melting characteristics and decrease in the curing window for different BPEs were caused by the incorporation BMIM. Addition of BMIM to BPEs reduces the heat liberated during the thermal curing. The curing kinetics is investigated using Flynn–Wall–Ozawa, Vyazovkin and Friedman methods. Amongst the various BPEs investigated, the activation energy ( Ea) values obtained from spirobiindane BPE (SPIPE) behaves entirely in a different manner compared to all other materials investigated. The apparent Ea values for SPIPE was observed to increase with increasing extent of reaction up to 0.2–0.5 and then the Ea values decrease with increasing extent of reaction up to 0.55–0.8. The Ea for the polymer blends obtained by the incorporation of BMIM with different BPEs shows nearly linear increase in the Ea value, and the rate of increase is influenced by the structure of the aromatic spacer present in between the propargyl groups.

Cyanate ester resins containing pentadecyl-substituted cyclohexyl moiety: Synthesis, curing and structure–property relationship

Cyanate ester (CE) monomers containing pentadecyl-substituted cyclohexyl moieties such as 1,1-bis(4-cyanatophenyl) 3-pentadecylcyclohexane and 1,1-bis(4-cyanatophenyl) cyclohexane were synthesized and characterized by Fourier transform infrared, proton-nuclear magnetic resonance (1H-NMR) and carbon-nuclear magnetic resonance (13C-NMR) spectroscopies as well as differential scanning calorimetry (DSC). Both 1,1-bis(4-cyanatophenyl) 3-pentadecylcyclohexane and 1,1-bis(4-cyanatophenyl) cyclohexane exhibited better processability coupled with lower melting points, lower cure onset with broad cure exotherm than the commercially available CE monomer, namely, 2,2-bis(4-cyanatophenyl) propane. Glass transition temperatures of cured 2,2-bis(4-cyanatophenyl) propane, 1,1-bis(4-cyanatophenyl) cyclohexane and 1,1-bis(4-cyanatophenyl) 3-pentadecylcyclohexane were observed to be 288°C, 302°C and 160°C, respectively. Cured 1,1-bis(4-cyanatophenyl) cyclohexane displayed higher storage modulus (1.59 × 10 9 Pa) than 1,1-bis(4-cyanatophenyl) 3-pentadecylcyclohexane (1.07 × 10 9 Pa) and 2,2-bis(4-cyanatophenyl) propane (1.39 × 10 9 Pa). The order of thermal stability of cured polycyanurates was found to be 2,2-bis(4-cyanatophenyl) propane > 1,1-bis(4-cyanatophenyl)cyclohexane > 1,1-bis(4-cyanato phenyl) 3-pentadecylcyclohexane. The moisture absorption of cured resins derived from 1,1-bis(4-cyanatophenyl) 3-pentadecyl cyclohexane and 1,1-bis(4-cynatophenyl)cyclohexane was found to be lower than that of 2,2-bis(4-cynatophenyl) propane implying the role of pentadecyl substituent and/or cyclohexyl moiety in imparting hydrophobicity to the polycyanurates.

Thermal, thermoechanical and morphological behavior of Octa (maleimido phenyl) silsesquioxane (OMPS)-cyanate ester nanocomposites

Polyhedral oligomeric silsesquioxane (POSS)-cyanate ester (CE) nanocomposites have been developed by the incorporation of octafunctional maleimide POSS (OMPS) into the bisphenol-A based CE network through in situ method by thermal curing with the use of diaminodiphenylmethane (DDM) as coupling agent. The formation of nanocomposite was confirmed by Fourier transform infrared analysis. X-ray diffraction, scanning electron microscopy and transmission electron microscopy images confirm the morphology of CE/OMPS nanocomposites. The thermal and morphological properties were studied by varying different weight percentages (1, 3, 5 and 10%) of OMPS. The 5 wt.% OMPS-incorporated nanocomposite possesses higher values of glass transition temperature than those of nanocomposites filled with a lower percentages of OMPS. Further thermal stability of nanocomposites increased with increase in percentage composition of OMPS.