High Performance Miscible Polyetherimide/Bismaleimide Resins with Simultaneously Improved Integrated Properties Based on a Novel Hyperbranched Polysiloxane Having a High Degree of Branching

Amino-terminated hyperbranched polysiloxane (AHBSi) with high degree of branching (= 0.8) was synthesized by a control hydrolysis of γ-aminopropyl triethoxysilane (APTES) without using any catalyst. Besides, AHBSi was used as the compatibilizer of the miscible polyetherimide (PEI)/bismaleimide (BD) blend, and the influence of the content of AHBSi on the compatibility and integrated performance of the PEI/BD blend was systematically investigated. The corresponding investigation of the APTES/PEI/BD system was also carried out for comparison. Results show that although AHBSi and APTES have similar chemical segments, their different topological structures endow them with completely different effects. AHBSi can remarkably improve the compatibility between PEI and BD resin, and the AHBSi/PEI/BD system not only has obviously improved toughness and decreased brittleness while maintaining good stiffness. It also exhibits decreased dielectric constant and loss. Conversely, the APTES/PEI/BD system has greatly deteriorated compatibility and integrated performance. These interesting results demonstrate that AHBSi is a super multifunctional compatibilizer

Flame Retarding Cyanate Ester Resin with Low Curing Temperature, High Thermal Resistance, Outstanding Dielectric Property, and Low Water Absorption for High Frequency and High Speed Printed Circuit Broads

High-end electric products require high frequency and high speed printed circuit broads (HFS-PCBs), while high performance resin is the key for fabricating HFS-PCBs. A new resin system (DPDP/CE) was developed by copolymerizing 10-(2,5-dihydroxyphenyl)-9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DPDP) and 2,2′-bis­(4-cyanatophenyl) propane (CE). Compared with CE resin postcured at 250 °C for 4 h, the DPDP/CE system that was only postcured at 220 °C for 2 h has outstanding flame retardancy, greatly reduced water absorption, low dielectric loss, and high thermal resistance. For DPDP1.4/CE resin with 1.4 wt % phosphorus content, its dielectric constant and loss at 1 GHz are 2.71 and 0.005, respectively, and hardly change after staying in boiling water for 100 h. Different from UL-94 V-2 rating of CE resin, the flame retardancy of DPDP1.4/CE resin is desirable UL-94 V-0 rating, resulting from both gas-phase and condensed-phase mechanisms. These attractive features suggest that the DPDP/CE system is suitable to fabricate HFS-PCBs for high-performance electric products

Multifunctional Cyclotriphosphazene/Hexagonal Boron Nitride Hybrids and Their Flame Retarding Bismaleimide Resins with High Thermal Conductivity and Thermal Stability

A novel hybridized multifunctional filler (CPBN), cyclotriphosphazene/hexagonal boron nitride (hBN) hybrid, was synthesized by chemically coating hBN with hexachlorocyclotriphosphazene and p-phenylenediamine, its structure was systemically characterized. Besides, CPBN was used to develop new flame retarding bismaleimide/<i>o</i>,<i>o</i>′-diallylbisphenol A (BD) resins with simultaneously high thermal conductivity and thermal stability. The nature of CPBN has a strong influence on the flame behavior of the composites. With the addition of only 5 wt % CPBN to BD resin, the thermal conductivity increases 2 times; meanwhile the flame retardancy of BD resin is remarkably increased, reflected by the increased limited oxygen index, much longer time to ignition, significantly reduced heat release rate. The thermogravimetric kinetics, structures of chars and pyrolysis gases, and cone calorimeter tests were investigated to reveal the unique flame retarding mechanism of CPBN/BD composites. CPBN provides multieffects on improving the flame retardancy, especially in forming a protective char layer, which means a more thermally stable and condensed barrier for heat and mass transfer, and thus protecting the resin from further combustion

Preparation of End-Capped Hyperbranched Polyaniline@Carbon Nanotube Hybrids for High‑<i>k</i> Composites with Extremely Low Percolation Threshold and Dielectric Loss

How to greatly decrease the dielectric loss while maintaining extremely low percolation threshold (<i>f</i>_c) is the main target of developing high-<i>k</i> conductor/polymer composites. Here, novel hybridized multiwalled carbon nanotubes (MWCNTs) with coated end-capped hyperbranched polyaniline (EHSiPA), EHSiPA@MWCNT, were developed and embodied into epoxy (EP) resin to produce new high-<i>k</i> composites. Systematic investigations of the structure and dielectric properties showed that the <i>f</i>_c of EHSiPA@MWCNT/EP composites is as low as 0.41 wt %; in addition, EHSiPA@MWCNT/EP composites with suitable loadings of EHSiPA have much higher dielectric constants and lower dielectric losses than the MWCNT/EP composite. Specifically, the dielectric constant and loss at 100 Hz for [email protected]/EP are 1.4 and 6.8 × 10^–3 times the values for the MWCNT0.4/EP composite, respectively. To reveal the origin of this, the distributions of space charges of EHSiPA@MWCNT/EP composites are discussed. This investigation suggests that designing and preparing new conductors with unique structures may provide a way to fabricate high-<i>k</i> composites

New Bismaleimide Resin Toughened by In Situ Ring-Opening Polymer of Cyclic Butylene Terephthalate Oligomer with Unique Organotin Initiator

A new organotin initiator with amino-terminated hyperbranched polysiloxane (HSiSn) for the ring-opening polymerization of cyclic butylene terephthalate (CBT) oligomer was synthesized. Compared with a traditional initiator, butyltin chloride dihydroxide (BCD), HSiSn has a moderate initiate speed, lower toxicity, and good reactivity. Poly­(butylene terephthalate) (PBT) is the ring-opening polymer of CBT, of which the crystalline and molecular weight are almost independent of the initiator used, but the PBT initiated by HSiSn has better thermal stability than that by BCD. On this basis, a series of new toughened bismaleimide (BD) resins (HSiSn/CBT-BD) were prepared through the in situ formation of PBT during the prepolymerization of BD resin with HSiSn. Compared with BCD/CBT-BD and BD resins, HSiSn/CBT-BD resins with small loadings of CBT (≤5 wt %) have remarkably improved integrated performances, including higher impact strengths, improved flexural, and tensile properties, better dielectric properties, and excellent heat resistance. These attractive performances are attributed to the unique cross-linked structure induced by HSiSn

Facile Preparation and Origin of High‑<i>k</i> Carbon Nanotube/Poly(Ether Imide)/Bismaleimide Composites through Controlling the Location and Distribution of Carbon Nanotubes

The morphology (location and distribution) of conductive fillers in conductive filler/polymer nanocomposites has a decisive influence on dielectric properties of a composite, so with the same components, how to facilely control the morphology of nanofillers, build its relationship with dielectric properties of the composite, and clearly reveal the origin behind are still interesting challenges. Herein, a fixed loading (0.4 wt %) of multiwalled carbon nanotubes (MWCNTs) was embodied into an incompatible poly­(ether imide) (PEI)/bismaleimide (BD) system to prepare a series of composites (0.4MWCNT/PEI/BD). As the PEI content increases, the structure of composite successively changes from sea-island to cocontinuous phase and phase inversion. More interestingly, MWCNTs prefer to selectively distribute in the BD phase, tend to enrich around the PEI dense zone, and arrange normally to the radius of the PEI sphere zone, so the morphology of MWCNTs and thus dielectric properties of composites can be facilely controlled. The dielectric constant and loss of 0.4MWCNT/PEI/BD composite with 10 wt % PEI are about 4.5 and 0.1 times the values of 0.4MWCNT/BD composite, respectively, overcoming the critical problem of available conductive filler/polymer composites. Different equivalent circuits were built for these composites, revealing the origin behind the method developed herein for controlling unique dielectric properties of 0.4MWCNT/PEI/BD composites

Thermally Conductive Aluminum Nitride–Multiwalled Carbon Nanotube/Cyanate Ester Composites with High Flame Retardancy and Low Dielectric Loss

New high-performance composites with high thermal conductivity, good flame retardancy, and low dielectric loss using cyanate ester (CE) resin as the matrix and hybrid fillers consisting of aluminum nitride (AlN) and multiwalled carbon nanotubes (MCNTs) as the functional phase were developed. In addition to the original fillers, surface-treated AlN (kAlN) and MCNTs (eMCNTs) were prepared to develop four types of hybrid fillers and the corresponding composites. The structures and properties of the ternary composites can be adjusted by controlling the interaction between the nanotubes and the AlN. Both AlN and kAlN fillers can improve the dispersion of nanotubes in the CE resin, regardless of whether the nanotubes are modified, whereas only eMNCTs can improve the dispersion of AlN or kAlN in the matrix. The kAlN–eMCNT hybrid was found to have the highest synergistic effect, endowing CE resin with outstanding thermal conductivity, low dielectric loss, significantly improved processing characteristics, and flame retardancy

Flame Retarding High‑<i>k</i> Composites with Low Dielectric Loss Based on Unique Multifunctional Coated Multiwalled Carbon Nanotubes and Cyanate Ester

Development of high-<i>k</i> composites with low dielectric loss and good flame retardancy is still a big challenge. Herein, unique cyanate ester (CE) composites based on multifunctional carbon nanotubes (EPHSi-<i>g</i>-MWCNTs) coated with phosphaphenanthrene terminated hyperbranched polysiloxane (EPHSi) were prepared. The 2.5EPHSi-<i>g</i>-MWCNT/CE composite with 2.5 wt % EPHSi-<i>g</i>-MWCNTs has the highest dielectric constant. The value at 100 Hz is about 1.4 times that of the 0.7MWCNT/CE composite that has the biggest value among MWCNT/CE composites, while interestingly, the dielectric loss at 100 Hz of the 2.5EPHSi-<i>g</i>-MWCNT/CE composite is only 5.8 × 10^–5 times that of 0.7MWCNT/CE. Also, the 2.5EPHSi-<i>g</i>-MWCNT/CE composite shows outstanding flame retardancy, reflected by the longer time to ignition, much lower peak heat release rate, and total smoke production. The study on the origin behind this demonstrates that, different from a simple combination of EPHSi and MWCNTs, EPHSi-<i>g</i>-MWCNTs have a super synergistic feature in preparing high-<i>k</i> polymeric composites with low dielectric loss and outstanding flame retardancy

Thermally Conductive Aluminum Nitride–Multiwalled Carbon Nanotube/Cyanate Ester Composites with High Flame Retardancy and Low Dielectric Loss

New high-performance composites with high thermal conductivity, good flame retardancy, and low dielectric loss using cyanate ester (CE) resin as the matrix and hybrid fillers consisting of aluminum nitride (AlN) and multiwalled carbon nanotubes (MCNTs) as the functional phase were developed. In addition to the original fillers, surface-treated AlN (kAlN) and MCNTs (eMCNTs) were prepared to develop four types of hybrid fillers and the corresponding composites. The structures and properties of the ternary composites can be adjusted by controlling the interaction between the nanotubes and the AlN. Both AlN and kAlN fillers can improve the dispersion of nanotubes in the CE resin, regardless of whether the nanotubes are modified, whereas only eMNCTs can improve the dispersion of AlN or kAlN in the matrix. The kAlN–eMCNT hybrid was found to have the highest synergistic effect, endowing CE resin with outstanding thermal conductivity, low dielectric loss, significantly improved processing characteristics, and flame retardancy

Facilely Synthesizing Ethynyl Terminated All-Aromatic Liquid Crystalline Poly(esterimide)s with Good Processability and Thermal Resistance under Medium-Low Temperature via Direct Esterification

Developing a facile strategy to synthesize thermosetting all-aromatic liquid crystalline poly­(esterimide)­s (LCPEIs) at medium-low temperature and endowing LCPEIs with good processability and high thermal resistance are still two big challenges. Herein, a new solution polymerization based on direct esterification under 120 °C is developed, overcoming bottlenecks of traditional melt and solution polymerizations. Besides, two new reactive LCPEIs (LCPEI-1 and LCPEI-2) terminated with 3-ethynylaniline (3-EA) were synthesized, and their structures and properties were compared with two control samples without 3-EA end groups. LCPEI-1 and LCPEI-2 not only show good processing characteristics including low melting temperature (<i>T</i>_m = 200 °C), low melting viscosity, and good solubility in solvent, but their cured samples also have high glass transition temperature (<i>T</i>_g = 192 and 225 °C) and high storage modulus, whereas control samples, even treated with similar thermal history as curing procedure for LCPEI-1 and LCPEI-2, have poor performances. Cured-LCPEI-2 exhibits the highest <i>T</i>_g among polyesters with low <i>T</i>_m values (<250 °C) reported. The mechanism behind outstanding performances of LCPEIs is discussed