13 research outputs found
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
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 Îł-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′-bisÂ(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
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><sub>c</sub>) 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><sub>c</sub> 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<sup>–3</sup> 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. PolyÂ(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 polyÂ(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<sup>–5</sup> 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
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 polyÂ(esterimide)Âs (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><sub>m</sub> = 200 °C),
low melting viscosity, and good solubility in solvent, but their cured
samples also have high glass transition temperature (<i>T</i><sub>g</sub> = 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><sub>g</sub> among polyesters
with low <i>T</i><sub>m</sub> values (<250 °C) reported.
The mechanism behind outstanding performances of LCPEIs is discussed
Water-Phase Synthesis of a Biobased Allyl Compound for Building UV-Curable Flexible Thiol–Ene Polymer Networks with High Mechanical Strength and Transparency
Using
water as a reaction medium to synthesize biobased monomers
with high renewable carbon content for preparing biobased polymers
is of great importance for environmental protection and sustainable
development. Herein, a trifunctional allyl compound, trisÂ(4-allyl-2-methoxyphenyl)
phosphate (TAMPP) with 100% renewable carbon content was synthesized
from renewable eugenol through one-step method using water as the
solvent. TAMPP was then used to prepare flexible and transparent thiol–ene
polymer networks TAMPP-SH via solvent-free thiol–ene “click”
photopolymerization with various multifunctional thiols. The influences
of the thiol functionality from 2 to 4 on structure and integrated
performances were systematically researched. Among them, TAMPP-SH4
shows the best thermal and mechanical properties. Specifically, its
glass transition temperature (<i>T</i><sub>g</sub>) is as
high as 35 °C, while its tensile strength and modulus are as
high as 19.8 ± 0.6 MPa and 601.6 ± 22.4 MPa, respectively.
At the same time, it still maintains high flexibility. The nature
behind these outstanding integrated performances is attributed to
the unique structure of TAMPP, which is rich in aromatic structure,
and the very high cross-linking density of TAMPP-SH4 network. The
especially high renewable carbon content and outstanding thermal and
mechanical performances clearly show that the TAMPP-SH4 network has
great potential in fabricating flexible products