Effects of molecular weight of polysulfone on phase separation behavior for cyanate ester/polysulfone blends

Effect of Amino-Functionalized Polyhedral Oligomeric Silsesquioxanes on Structure-Property Relationships of Thermostable Hybrid Cyanate Ester Resin Based Nanocomposites

Nanocomposites of cyanate ester resin (CER) filled with three different reactive amino-functionalized polyhedral oligomeric silsesquioxane (POSS) were synthesized and characterized. The addition of a small quantity (0.1 wt.%) of amino-POSS chemically grafted to the CER network led to the increasing thermal stability of the CER matrix by 12-15 °C, depending on the type of amino-POSS. A significant increase of the glass transition temperature, Tg (DSC data), and the temperature of α relaxation, Tα (DMTA data), by 45-55 °C of the CER matrix with loading of nanofillers was evidenced. CER/POSS films exhibited a higher storage modulus than that of neat CER in the temperature range investigated. It was evidenced that CER/aminopropylisobutyl (APIB)-POSS, CER/N-phenylaminopropyl (NPAP)-POSS, and CER/aminoethyl aminopropylisobutyl (AEAPIB)-POSS nanocomposites induced a more homogenous α relaxation phenomenon with higher Tα values and an enhanced nanocomposite elastic behavior. The value of the storage modulus, E', at 25 °C increased from 2.72 GPa for the pure CER matrix to 2.99-3.24 GPa for the nanocomposites with amino-functionalized POSS nanoparticles. Furthermore, CER/amino-POSS nanocomposites possessed a higher specific surface area, gas permeability (CO2, He), and diffusion coefficients (CO2) values than those for neat CER, due to an increasing free volume of the nanocomposites studied that is very important for their gas transport properties. Permeability grew by about 2 (He) and 3.5-4 times (CO2), respectively, and the diffusion coefficient of CO2 increased approximately twice for CER/amino-POSS nanocomposites in comparison with the neat CER network. The efficiency of amino-functionalized POSS in improving the thermal and transport properties of the CER/amino-POSS nanocomposites increased in a raw of reactive POSS containing one primary (APIB-POSS) < eight secondary (NPAP-POSS) < one secondary and one primary (AEAPIB-POSS) amino groups. APIB-POSS had the least strongly pronounced effect, since it could form covalent bonds with the CER network only by a reaction of one -NH2 group, while AEAPIB-POSS displayed the most highly marked effect, since it could easily be incorporated into the CER network via a reaction of -NH2 and -NH- groups with -O-C≡N groups from CER.

Design and Evaluation of a Cyanate Ester Containing Oxaspirocyclic Structure for Electronic Packaging

A type of pentaerythritol cinnamaldehyde bisphenol dicyanate ester (PCBDCy) containing oxaspirocyclic structure is well designed and synthesized in three steps from cinnamaldehyde, pentaerythritol, phenol, and cyanogen bromide. The products in each step are characterized by elemental analysis, Fourier transform infrared (FT-IR) spectroscopy, and 1H NMR spectroscopy. The mechanical properties, dielectric properties, thermostability, and water absorption of PCBDCy are investigated in detail. The results show that compared with bisphenol A dicyanate (BADCy), the PCBDCy possesses more excellent comprehensive properties. The bending strength and flexural strength are increased by 10.71% and 47.62%, respectively. The fracture toughness $K_{\text{IC}}$ and $G_{\text{IC}}$ are 1.5 times and 2 times of BADCy, respectively, indicating that its mechanical properties have been considerably improved. The dynamic mechanical curves indicates that the degree of phase separation is significantly reduced, the tan (δ) value representing the flexible phase is obviously shifted to the high temperature region, and the initial decomposition temperature was 12°C higher than that of BADCy, indicating that the material has excellent thermal stability. In addition, the dielectric constant and loss tangent are almost as same as those of BADCy, maintaining good dielectric properties. The water absorption rate has increased to $1.03\pm 0.03\%$ . Compared with BADCy, its comprehensive performance is more suitable for the field of microelectronic packaging.

Properties and structure of high temperature resistant cyanate ester/polyethersulfone blends using solvent-free toughening approach

A high temperature resistant novolac cyanate ester was blended with polyethersulfone (PES) with different molecular weights using the solvent-free approach. The phase separation, curing behavior and thermal properties were studied using hot stage microscopy, differential scanning calorimetry and dynamic mechanical analysis. Results showed the difference in the morphology for blends with different molecular weight PES explained by possible network formation. The influence of PES content on the glass transition temperature and mechanical properties was investigated. The most significant toughening effect (increase of 132% in fracture toughness) was achieved on a functionalized low molecular weight PES (20 parts per hundred of resin, phr). Rheology investigation allowed to estimate the optimal content of PES (15 phr) for further prepreg manufacturing.

Cyanate ester resin based composites with high toughness and thermal conductivity

A new cyanate ester resin-based composite with higher toughness and thermal conductivity was developed. First, a poly(n-butyl acrylate)/poly(methyl methacrylate-co-acrylamide) (PBMAM) core-shell structured latex was prepared by seeded emulsion polymerization. Second, hexagonal boron nitride (h-BN) particles were modified by a surface coupling agent, 3-(2-amino ethyl amino)propyl trioxysilane, to improve the dispersion in cyanate ester resin (BADCy). Third, PBMAM and the modified boron nitride were mixed with BADCy resin to increase mechanical properties and thermal conductivity. The monomer conversion in the emulsion polymerization process of the PBMAM was monitored by determining the solid content. Its particle size was characterized by dynamic laser scattering, and the morphology of the particles was characterized using scanning and transmission electron microscopes. The modified boron nitride (ABN) was verified by FTIR and TGA measurements. The mechanical properties and thermal conductivity of the BADCy/PBMAM/ABN composites were determined at various BN contents. Results showed that the unnotched impact strength of the composite increased by 151% and the thermal conductivity increased by 85% at a PBMAM content of 5 wt% and ABN content of 6 wt%. With the enhanced properties and ease of fabrication, the developed composites have good potential for application in high-end industries such as microelectronic packaging.

Dual effects of mesoscopic fillers on the polyethersulfone modified cyanate ester: enhanced viscoelastic effect and mechanical properties

Enlarging the filler content and decreasing the filler size contribute to enhancing both viscoelastic effect and mechanical property of polyethersulfone modified cyanate system.