共查询到20条相似文献,搜索用时 31 毫秒
1.
采用聚磷酸铵(APP)与不同比例三聚氰胺(MA)和三嗪成炭剂(CFA)复配对环氧树脂进行阻燃改性。系统研究了不同配比阻燃剂(总量保持40wt%)的加入对环氧树脂流变特性、固化行为、热机械性能、力学性能及阻燃性能的影响。将优化后的阻燃改性环氧树脂用于制备玻璃纤维增强环氧树脂复合材料(GFRC),对并其力学和阻燃性能进行了研究。结果表明,APP单独与MA或CFA复配改性环氧树脂并未表现出明显的协同阻燃效应,但它们组成的三元复配阻燃体系(30wt%APP-5wt%MA-5wt%CFA)具有良好的协同阻燃效应。相比未改性环氧树脂,APP-MA-CFA改性环氧树脂的极限氧指数(LOI)由18.0%提高到了50.2%,热释放峰值速率(PHRR)下降了84%,总热释放量(THR)下降了78%。树脂基体中加入阻燃剂后,GFRC的力学性能有所下降,尤其是层间剪切强度。同样地,基于APP-MA-CFA复配改性环氧树脂的GFRC表现出最佳阻燃性能,相比未改性的GFRC,其LOI值由22.8%提高到了66.0%,PHRR由354 kW/m2下降到93 kW/m2,THR由49.3 MJ/m2下降到22.8 MJ/m2。 相似文献
2.
Novel intercrosslinked networks of polyethersulfone modified epoxy-3,3′-bis(maleimidophenyl) phenylphosphine oxide matrix systems are developed. The polyethersulfone modification of epoxy resin is
carried out by using tetramethyl ammonium hydroxide (TMAH) as a catalyst. The polyethersulfone modified epoxy systems are
further modified with 4–12% 3,3′-bis(maleimidophenyl) phenylphosphine oxide and cured by using diaminodiphenylmethane. Tensile, flexural, impact properties and
dynamic mechanical analysis (DMA) are carried out to assess the mechanical behaviour of the prepared neat resin castings.
Mechanical studies indicate that the introduction of polyethersulfone into these epoxy resins improves the toughness without
any reduction in the stress-strain values. But, the incorporation of bismaleimide (BMI) into the epoxy resin improves the
stress-strain properties with a lowering of the toughness. The introduction of both polyethersulfone and bismaleimide into
the epoxy resin influences the mechanical properties according to their content percentages. 相似文献
3.
O. V. Suberlyak V. V. Krasins’kyi I. M. Shapoval O. M. Hrytsenko 《Materials Science》2011,46(5):669-678
We study the influence of concentrations of the components of reactive compositions and the conditions of production and hardening
of phenol-formaldehyde resins with the help of epoxy resins in the presence of polyvinylpyrrolidone on the physicomechanical,
thermal, adhesion, insulation, and anticorrosion properties of the composites. The positive effect of modifications with polyvinylpyrrolidone
and epoxy resin manifests itself within the following ranges of concentrations: 0.5–1 wt.% of polyvinylpyrrolidone and 25–30
wt.% of ED-20 in the presence of 1 wt.% of N, N-dimethylaniline. Thus, the adhesion strength of a glue based on the developed
composition becomes four times higher and constitutes 5–6 MPa; the impact strength, static strength in bending, surface hardness,
and the specific bulk electric resistance of the specimens hardened at 150–160°C for 25–30 min become 1.5–2.5 times higher
and are equal to 5–6J/m2, 15–17 MPa, 350–420 MPa, and (5.5–6.5)⋅1010 Ω⋅m, respectively. The behavior of these characteristics strongly depends on the conditions of hardening. We optimized the
composition of modified phenol-formaldehyde resins, which made it possible to produce materials with predicted properties. 相似文献
4.
Evaluation of a.c. conductivity behaviour of graphite filled polysulphide modified epoxy composites 总被引:1,自引:0,他引:1
Composites of epoxy resin having different amounts of graphite particles have been prepared by solution casting method. Temperature
dependence of dielectric constant, tan δ and a.c. conductivity was measured in the frequency range, 1–20 kHz, temperature
range, 40–180°C for 0.99, 1.96 and 2.91 wt% graphite filled and unfilled epoxy composites. It was observed that the dielectric
constant, tanδ and a.c. conductivity increase with increasing temperature. Near the transition temperature the materials show anomalous
behaviour for the observed properties. Peaks of dielectric constant, tan δ and a.c. conductivity were observed to shift towards
lower temperature with increasing frequency. Clear relaxation (tan δ) peaks around 169°C were observed in epoxy resin, which
shifted to lower temperature side on increasing the frequency. Addition of 2.91 wt% graphite shifted the tan δ peaks towards
higher temperature side by creating hindrances to the rotation of polymer dipoles. Addition of 2–91 wt% graphite leads to
an increased relaxation time τ of dipoles in polysulphide epoxy from 1.44 × 10−5− 3.92 × 10−5 (s) at 90°C by creating the hindrance to the rotation of dipoles. 相似文献
5.
Blend samples were prepared by physical mixing of resole–epoxy blend with carboxyl-terminated polybutadiene (CTPB) liquid
rubber ranging between 0 and 25 wt% in the interval of 5 wt%. Resoles were synthesized with phenol and various alkyl phenols.
The blends were cured with 40 wt% polyamide. The structural changes during the curing were investigated by infra-red spectroscopic
analysis. The presence of CTPB in resole-epoxy blends did not affected the values of cure times and ΔH whereas the gel time decreased up to 15 wt% addition of CTPB in the blends. The blend systems containing p-cresolic resole, epoxy and CTPB showed minimum gel time amongst all other blend samples. A clear-cut two-step mass loss in
thermogravimetric (TG) trace of unmodified and CTPB-modified systems was observed. The mechanical properties of the blend
samples were found to be affected by the CTPB addition. The plane strain fracture toughness (K
IC) values of CTPB-modified matrix resins were greater that that for the unmodified resole/epoxy blends. This was further verified
by scanning electron microscopic (SEM) analysis. 相似文献
6.
A Gupta P Esquinazi H F Braun W Sadowsky E Walker D Shaltiel 《Bulletin of Materials Science》1991,14(3):877-882
We present vibrating reed (VR) measurements on single crystal and ceramic “1-2-3” and melt-processed polycrystalline Bi-based
compounds in a wide range of temperature (4·2–100 K) and magnetic field (B=0–4 T). The “depinning line” (DL) determined by the VR technique is equivalent to the “irreversibility line” determined by
magnetization and susceptibility measurements. A comparison of the results on single crystal and polycrystalline 1-2-3 compounds
indicates that the VR technique is sensitive to the intragranular properties of the polycrystalline reed. It is found that
the DL for 1-2-3 compounds is much steeper than that for Bi-based compounds, reflecting an intrinsically different pinning
in both the materials, in agreement with the measured elastic coupling (Labusch constant α(B, T)). 相似文献
7.
《Composites Part A》2004,35(1):95-101
Two primary cost driving factors for the composites industry are raw materials and labor. Inexpensive alternative epoxy resin systems based on epoxidized soyate resins are developed for fiber reinforced composite applications. This research investigated on the manufacturing and mechanical characterization of fiber/epoxy composites using chemically modified soy-based epoxy resins. Co-resin systems with up to 30 wt% soyate resins were used to manufacture composites through pultrusion. Mechanical tests show that the pultruded composites with soy based co-resin systems possess comparable or improved structural performance characteristics such as flexural strength, modulus, and impact resistance. Maximum mechanical properties enhancement is demonstrated by the enhanced epoxidized allyl soyate (EAS) formulation. Further property improvement is obtained through using a two-step prepolymer process. The EAS holds great potential as partial supplement for polymer and composites applications from renewable resources. 相似文献
8.
Yuanxin Zhou Mahesh Hosur Shaik Jeelani P. K. Mallick 《Journal of Materials Science》2012,47(12):5002-5012
In this study, dynamic mechanical analysis (DMA), thermogravimetric analysis (TGA), and flexural tests were performed on unfilled,
1, 2, 3, and 4 wt% clay filled SC-15 epoxy to identify the effect of clay weight fraction on thermal and mechanical properties
of the epoxy matrix. The flexural results indicate that 2.0 wt% clay filled epoxy showed the highest improvement in flexural
strength. DMA studies also revealed that 2.0 wt% system exhibit the highest storage modulus and T
g as compared to neat and other weight fraction. However, TGA results show that thermal stability of composite is insensitive
to the clay content. Based on these results, the nanophased epoxy with 2 wt% clay was then utilized in a vacuum assisted resin
transfer molding set up with carbon fabric to fabricate laminated composites. The effectiveness of clay addition on thermal
and mechanical properties of composites has been evaluated by TGA, DMA, tensile, flexural, and fatigue test. 5 °C increase
in glass transition temperature was found in nanocomposite, and the tensile and flexural strengths improved by 5.7 and 13.5 %,
respectively as compared to the neat composite. The fatigue strength was also improved significantly. Based on the experimental
result, a linear damage model combined with the Weibull distribution function has been established to describe static failure
processing of neat and nanophased carbon/epoxy. The simulated stress–strain curves from the model are in good agreement with
the test data. Simulated results show that damage processing of neat and nanophased carbon/epoxy described by bimodal Weibull
distribution function. 相似文献
9.
In the present work, we investigated the thermo-viscoelasticity and fracture toughness of various cured blends of two epoxy
monomers with different molecular weights: 380 (Epikote 828) and 900 (Epikote 1001). The blended resins were easily prepared,
and miscibility (no phase separation) in the blended resins was expected. The composition of the blended epoxy resins ranged
from 0 to 100% by weight of the Epikote 1001. The measured damping factor and dynamic loss modulus in the glass-transition
confirmed that each blended resin had a single phase, i.e., they were miscible. The fracture toughness at room temperature
increased modestly with the Epikote 1001 content over the whole range (0–100 wt%). We found that below the glass-transition
temperature, the macromolecular modifications enabled tailoring of the fracture toughness while maintaining the glassy bending
modulus and with little change in the glass-transition temperature. 相似文献
10.
合成了一种含磷酚醛型环氧树脂固化剂DCPD-DOPO,通过红外光谱和核磁共振谱对其化学结构进行了表征,采用凝胶渗透色谱测量了其相对分子质量。以DCPD-DOPO、苯酚型酚醛树脂(PF8020)或其复合物为固化剂,双酚A环氧树脂(DGEBA)为基料,制备了不同磷含量的阻燃环氧树脂。通过热重分析、差示扫描量热分析研究了环氧树脂固化物的热性能和阻燃性能;通过极限氧指数(LOI),垂直燃烧实验和锥形量热法研究了固化后环氧树脂固化物的燃烧特性。结果表明,DCPD-DOPO固化的环氧树脂的LOI可达31.6%,垂直燃烧性能达到UL94 V-0级,玻璃化转变温度(T_g)为133℃。采用DCPD-DOPO与PF8020复合物固化的环氧树脂的T_g提高到138℃以上,LOI值略有降低,但仍能通过UL 94V-0测试。DCPD-DOPO与PF8020添加DCPD-DOPO后,复合固化的环氧树脂的热释放速率峰值及总释热量较PF8020固化的环氧树脂大幅度降低。此外,还用Kissinger法对环氧树脂固化反应动力学进行了研究。 相似文献
11.
The structure and mechanical properties of Cu10 wt% Al base alloys with 0–2.5 wt% Ti additions were investigated using transmission
electron microscopy, optical microscopy and tensile tests. Addition of titanium has a decreasing effect on the grain size
after quenching fromα + β region and causes significant strengthening of alloys. Alloy containing 1 wt%Ti quenched from 900° C shows mixture ofα, retainedβ (DO3), disorderedβ′ (3R) and orderedβ′
1 (18R) martensites. Alloy with 2.5 wt% Ti addition after quenching containsα, retainedβ (DO3), ordered T1 phase of L21 superlattice and orderedβ′
1 martensite with either R18 or L10 structure indicating different stacking of ordered planes as the effect of titanium addition. 相似文献
12.
An investigation of the blending, rheological and tensile properties of poly(vinyl alcohol) (PVA) and nylon 6 clay (NYC) nanocomposite
blends was conducted. The characteristics of melting endotherm, X-ray diffraction patterns of α form PVA crystals and hydrogen-bonded
hydroxyl groups originally associated with the PVA resin almost disappear after blending less than 16.7 wt% of PVA in NYC
resins. However, the characteristics of melting endotherm, X-ray diffraction of α form PVA crystals and hydrogen-bonded hydroxyl
groups originally associated with the PVA resins appear gradually as the PVA contents of NYC/PVA specimens are more than 16.7 wt%.
The torques vs. time measurements and tensile properties of NYC/PVA specimens support the ideas that PVA molecules are miscible
with PA molecules to some extents in the molecular level as the PVA contents of NYC/PVA specimens are less than 16.7 wt%.
Moreover, the additional demarcated humps and significantly increased torques and “stabilized” time values support the presence
of separated PVA phases in NYC/PVA specimens as their PVA contents are more than 50 wt%. On the other hand, the α form PA
crystals continue to grow at the expense of γ form PA crystals as the PVA contents of NYC/PVA specimens increase, and the
characteristics of the γ form PA crystals originally shown on the melting endotherm and X-ray diffraction patterns of the
NYC resin can barely be seen as the PVA contents of NYC/PVA specimens are equal to or more than 50 wt%. Possible reasons accounting
for these interesting blending properties are proposed. 相似文献
13.
A effective flame retardant for epoxy resins based on poly(DOPO substituted dihydroxyl phenyl pentaerythritol diphosphonate) 总被引:2,自引:0,他引:2
Poly(DOPO substituted dihydroxyl phenyl pentaerythritol diphosphonate) (PFR) was synthesized via the reaction between 10-(2,5-dihydroxyl-phenyl)-9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO-BQ) and pentaerythritol diphosphonate dichloride (SPDPC). The structures of PFR were characterized by Fourier transformed infrared (FTIR) spectroscopy and 1H nuclear magnetic resonance (1H NMR). Thermal degradation behaviors and flame retardant properties of the epoxy resin (ER)/PFR systems were investigated from the thermogravimetric analysis (TGA), UL-94 test and the limiting oxygen index (LOI) test. Moreover, the surface morphology of the char residue was studied by scanning electron microscopy (SEM). When the PFR content reached 10 wt%, the epoxy resin system met the UL-94 V0 classification and the LOI value of 30.2. The microscale combustion calorimetry (MCC) was used to evaluate the combustion behaviors of the ER/PFR. It was found that the addition of PFR obviously decreased the value of peak heat release rate and total heat release of the hybrids. The TGA results showed that the epoxy resin with 10 wt% PFR exhibited high char yields. The high char yields and the high limiting oxygen index values were found to certify the excellent flame retardancy of this phosphorus-containing epoxy resin. 相似文献
14.
Wen Xue Chen Song Bai Xue Hui Wang Jian Xin Wang Zong Jie Han Li Li Gao 《Journal of Materials Science: Materials in Electronics》2010,21(5):461-467
The microstructures, wettabilities and mechanical properties of Sn–9Zn–xAg (x = 0, 0.1, 0.3, 0.5, 1 wt%) lead-free solders were investigated, respectively in this paper. Results show that, when the quantity
of Ag added to the solder is 0.3 wt%, the microstructure of the solder becomes finer and more uniform than Sn–9Zn, and when
the quantity of Ag is exceeded 0.3 wt% (upto 0.5–1 wt%), the AgZn3 intermetallic compounds appear in the solder. In particular, adding 0.3 wt% Ag improves the wettability due to the better
oxidation resistance of the Sn–9Zn–0.3Ag solder. Results also indicate that adding 0.3 wt% Ag to the solder enhances mechanical
property of soldered joint, at which the fracture micrographs show that plenty of small and uniform dimples could be observed
on the Sn–9Zn–0.3Ag soldered joints fractures. When the content of Ag is upto 1 wt%, some Cu–Zn and Ag–Zn intermetallic compounds
appear on the bottom of dimples, and the mechanical property of the soldered joint decreases. 相似文献
15.
The effect of nanosilica on compressive properties of an Epikote 828 epoxy at room temperature was studied. A 40 wt% nanosilica/epoxy
masterbatch (nanopox F400) was used to prepare a series of epoxy based nanocomposites with 5–25 wt% nanosilica content. Static
uniaxial compression tests were conducted on cubic and cylindrical specimens to study the compressive stress–strain response,
failure mechanisms and damage characteristics of the pure and nanomodified epoxy. It was found that the compressive stiffness
and strength were improved with increasing nanosilica content without significant reduction in failure strain. The presence
of nanosilica improved ductility and promoted higher plastic hardening behaviour after yielding in comparison with the unmodified
resin system. This result suggested that nanoparticles introduced additional mechanisms of energy absorption to enhance the
compressive properties without reducing the deformation to failure. 相似文献
16.
Leandro Alfredo Ramajo Maria Marta Reboredo Miriam Susana Castro 《Journal of Materials Science》2007,42(10):3685-3691
Polymer composites of epoxy resin and Nb2O5 doped BaTiO3 were prepared in the form of film (thickness 30–300 μm) using a dipping technique. Samples containing various amounts of
ceramic filler were examined by thermal analysis and SEM analysis. Dielectric measurements were performed from 20 Hz to 1 MHz
and 20 °C to 120 °C. It was found that the final materials had high permittivities increasing with the filler concentration.
Electrical relaxations were assigned to interfacial phenomena due to the particles and α-relaxation because of the resin. 相似文献
17.
John J. La Scala Matthew S. Logan James M. Sands Giuseppe R. Palmese 《Composites Science and Technology》2008,68(7-8):1869-1876
Vinyl ester (VE) resins with a bimodal distribution of molecular weights were prepared via methacrylation of epoxy monomers. Bimodal VE resins and neat polymers had viscosities and mechanical properties similar to that of commercial resins. E-glass composites were prepared and also found to have similar mechanical and thermo-mechanical properties relative to composites fabricated using commercial resins. However, the fracture toughness of the bimodal resins was superior to that of the commercial resins partially as a result of increased molecular relaxations that were manifested in a broader glass transition. Overall, bimodal resins allow for the use of low styrene content (33 wt%), while maintaining excellent thermal, mechanical, and fracture properties for the neat resins and composites. 相似文献
18.
Bejoy Francis V. Lakshmana Rao Seno Jose Bina K. Catherine R. Ramaswamy Jesmy Jose Sabu Thomas 《Journal of Materials Science》2006,41(17):5467-5479
A diglycidyl ether of bisphenol-A (DGEBA) epoxy resin was modified with poly(ether ether ketone) with pendent methyl groups (PEEKM). PEEKM was synthesised from methyl hydroquinone and 4,4′-difluorobenzophenone and characterised. Blends of epoxy resin and PEEKM were prepared by melt blending. The blends were transparent in the uncured state and gave single composition dependent T
g. The T
g-composition behaviour of the uncured blends has been studied using Gordon–Taylor, Kelley–Bueche and Fox equations. The scanning electron micrographs of extracted fracture surfaces revealed that reaction induced phase separation occurred in the blends. Cocontinuous morphology was obtained in blends containing 15 phr PEEKM. Two glass transition peaks corresponding to epoxy rich and thermoplastic rich phases were observed in the dynamic mechanical spectrum of the blends. The crosslink density of the blends calculated from dynamic mechanical analysis was less than that of unmodified epoxy resin. The tensile strength, flexural strength and modulus were comparable to that of the unmodified epoxy resin. It was found from fracture toughness measurements that PEEKM is an effective toughener for DDS cured epoxy resin. Fifteen phr PEEKM having cocontinuous morphology exhibited maximum increase in fracture toughness. The increase in fracture toughness was due to crack path deflection, crack pinning, crack bridging by dispersed PEEKM and local plastic deformation of the matrix. The exceptional increase in fracture toughness of 15 phr blend was attributed to the cocontinuous morphology of the blend. Finally it was observed that the thermal stability of epoxy resin was not affected by the addition of PEEKM. 相似文献
19.
The mechanical and failure behaviour of basalt fiber (BF) mat-reinforced (30 wt%) composites with vinylester (VE) and vinylester/epoxy
(VE/EP) hybrid resins were studied as a function of resin hybridization (VE/EP = 3/1, 1/1 and 1/3) and BF surface treatment.
BF was treated either with vinyl or epoxy functionalized organosilanes (VS and ES, respectively). The VE/EP hybrids exhibited
an interpenetrating network (IPN) structure in the studied composition range. Specimens, cut of plaques produced by resin
transfer molding (RTM), were subjected to static (tensile, flexural) and dynamic (instrumented Charpy and falling weight impact)
loading. The fracture toughness was determined under both static and dynamic conditions. The development of the damage zone
and its propagation were followed by location of the acoustic emission (AE). It was found that the mechanical properties of
the composites were strongly improved when mats with treated BF surface were incorporated. This was mostly traced to the good
interfacial adhesion between the BF and matrix according to fractographic inspection. The formation of the interphase (ca.
2 μm thick) was influenced by the BF treatment: VS coating of the BF resulted in VE-, whereas ES-treatment in EP-enrichment
in the interphase due to which the IPN structure also changed locally. This was demonstrated by nanoindentation measurements
performed with an atomic force microscopy (AFM) on ion-ablated polished surface specimens. 相似文献
20.
This study examines the shear strength behavior of the high-temperature Zn–20 wt% Sn, Zn–30 wt% Sn, and Zn–40 wt% Sn solders
in the temperature range of 298–425 K. The results showed that increasing the Sn content of the alloys decreases both shear
yield stress (SYS) and ultimate shear strength (USS) at all test temperatures. This can be attributed to the higher volume
fraction of the softer β-Sn matrix and the eutectic α-Zn + β-Sn structure, which replaces the colonies of the harder α-Zn
phase in the microstructure. The high shear strength of these high temperature solder alloys makes them suitable for application
in harsh environments. 相似文献