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1.
The paper discusses the test results of butadiene-acrylonitrile rubber, Perbunan NT 1845 and Perbunan NT 3945, flammability and properties that characterise these elastomers under fire conditions. The flammability was tested by means of oxygen index and thermovision methods. The thorough testing of flammability performed by means of a cone calorimeter made it possible to assess the behaviour of these polymers under fire conditions. The following properties of the tested copolymers were taken into account in this assessment: ignitability, heat release during combustion, smoke-forming capability and toxicity of the gaseous products of thermal decomposition and combustion. It has been found that the increase in the acrylonitrile unit content in the copolymer decreases its flammability and the relative toxic fire hazard, but clearly increases the smoke-forming capability and so the specific extinction area.The interpretation of test results of the elastomers under investigation takes into consideration their thermal stability assessed on the basis of differential thermal analysis, thermogravimetry and other complementary methods.This revised version was published online in November 2005 with corrections to the Cover Date.  相似文献   

2.
Incorporating elastic polysiloxane and/or an inorganic silica network in epoxy resin could result in the enhancement of physico-chemical properties due to the existence of Si-O bonds. To improve the compatibility between polysiloxane and epoxy matrices and intensively strengthen the properties of the modified system, here polysiloxane was introduced into epoxy resin through compatibilizing epoxy-immiscible polysiloxane with epoxy-miscible polycaprolactone segments via a sol-gel process. To fulfill the process, a blend containing alkoxysilane-functionalized polycaprolactone/polydimethylsiloxane (PCS-2Si) was firstly synthesized using direct nucleophilic addition between -OH groups of polydiol and -NCO of a silane. And then a series of modified epoxy resins were prepared in different epoxy/PCS-2Si weight ratios. All the modified composites were characterized by conventional methods, and their morphological, thermal degradation and surface properties were studied. The results showed that increasing the PCS-2Si content caused the changes of miscibility between epoxy and polysiloxane. Also, the thermal stability of the modified composites was greatly improved. As for the temperature value at 5% weight loss, it reached to 308.5 °C for the composite containing 50-60% (wt%) PCS-2Si, over 150 °C higher than that for neat amine-cured epoxy resin. Similarly, the modified composites showed good hydrophobicity. The improvement of these properties came from the improved interaction between PCS-2Si and epoxy, the forming of Si-O-Si network and the enrichment of siloxane chains on the surface of films. Therefore, it is believed that this modified epoxy appears promising as new high performance and highly functional materials.  相似文献   

3.
Polycyanurate from dicyanate of bisphenol A was modified with epoxy- and phenol-terminated butadiene-acrylonitrile rubbers. Rubber-resincopolymerisation was followed by multiple-detection gel-permeation chromatography (GPC). It was found that both the epoxy-terminated and phenol-terminated rubbers react with the cyanate and thus are covalently bound with the polycyanurate network. The influence of rubber content, acrylonitrile content and type of end group on phase structure was investigated using dynamic mechanical analysis. Fracture toughness was measured for these modifications.  相似文献   

4.
The rapid development of high-power devices has driven the requirement for high-temperature stable epoxy molding compounds. In this work, a designed polymer blend system consisting of cyanate ester/epoxy copolymers modified by polyimide (CE/EP-PI) has been studied. Polyimide used in this study has shown excellent dispersity in the cyanate ester and epoxy copolymer network (CE/EP), exhibiting homogeneous phase with a denser polymer network structure. With this polymer blend structure, CE/EP-PI system was proved to have a glass transition temperature as high as ~270 °C, increased modulus, and largely enhanced fracture toughness up to 2.06 MPa m1/2. CE/EP-PI resins showed outstanding long-term stability at high temperature with low mass loss and increased fracture toughness after aging at 200 °C. This work provides a novel insight into the development of molding compounds based on polymer blends system with excellent high-temperature properties. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2018 , 56, 2412–2421  相似文献   

5.
The paramagnetic probe method with the use of free radicals of different dimensions (2,2,6,6-tet-ramethyl-1-piperidinyloxy and 4-benzoate-2,2,6,6-tetramethyl-1-piperidinyloxy) has been employed to study the effect of the isomeric composition of butadiene units in polybutadienes and butadiene-acrylonitrile copolymers on the number and dimensions of ordered structures. The nature of density fluctuations and defective regions, that is, the regions in which the radicals are sorbed, has been ascertained. It has been shown that the ordered regions are composed of stereoregular chain fragments, while defective regions are enriched with butadiene isomers different from those present in prevailing amounts.  相似文献   

6.
The effect of co-condensation products of low molecular weight carboxylated butadiene and butadienenitrile rubbers with epoxy resin ED-20 on physico-mechanical properties of epoxy-rubber coatings and free films was studied.  相似文献   

7.
Cure reactions of a liquid aromatic dicyanate ester [1,1′‐bis(4‐cyanatophenyl) ethane, DiCy] associated with a liquid cycloaliphatic epoxy ester (3,4‐epoxycyclohexylmethyl‐3,4‐epoxycyclohexane‐carboxylate, EPC) and with liquid bisphenol A epoxide [2,2‐bis(4‐glycidyloxyphenyl)propane, EPA] were studied through a cross‐reference between in situ FTIR and DSC dynamic scanning. DiCy can act here as a latent catalyst to cure EPC and EPA resins. Reaction mechanisms were found to be different for both curing systems (EPC/DiCy and EPA/DiCy). Two significantly separated exotherms were observed in the DSC thermograms in each system. The reaction mechanism of the EPA/DiCy system was found to follow mainly Bauer pathways. We postulate a new sequence of the mechanism in this system due to the presence of an oxazoline structure during the progression of the curing process. In the curing system of EPC/DiCy, however, another five principle reaction paths, rather than Bauer pathways, are suggested: (1) polycyclotrimerization of DiCy, (2) formation of oxazoline, (3) insertion of EPC into cyanurate, (4) formation of tetrahydro–oxazolo–oxazole, and (5) ring cleavage and reformation of oxazoline to form the insertion structure of cyanurate. The lower temperature peak in the DSC thermogram is primarily contributed by the former three reaction paths, whereas the higher temperature peak can mainly be attributed to the reaction paths 4 and 5. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 2934–2944, 2000  相似文献   

8.
9.
A series of polycyanurate networks (PCN), based on the dicyanate of bisphenol A monomer (DCBA), was synthesized in the presence of different contents of polyoxypropylene glycol (PPG). The formation of very finely divided morphologies with highly interpenetrated phases, i.e. a PCN‐ rich phase, a mixed phase of PCN/PPG components and a PPG‐rich phase was determined. It is supposed that the lowering of the glass transition temperature of modified network matrix at increasing PPG content is due to a) PPG incorporation, b) decrease of the final DCBA conversion and c) the increase of percentage of non‐incorporated PPG, which acts as plasticizer.  相似文献   

10.
A novel kind of modified bismaleimide/cyanate ester (BCE) resins by copolymerizing with hyperbranched polysiloxane including high content of phenyl (HBPSi) was first reported. The effect of HBPSi on the curing mechanism, and that on the dielectric properties and flame retardancy of cured networks were systemically investigated. Results show that compared with BCE resin, HBPSi/BCE resin has obviously different cross-linked structure, and thus leading to simultaneously improved dielectric properties and flame retardancy. The reactions between HBPSi and the decomposition structure of BCE resin change the thermo-oxidative degradation mechanism of the first step in the thermo-oxidative degradation; in addition, the presence of HBPSi in BCE resin also significantly reduces the mass loss rate (MLR) and increases char yield at 800 °C under an air atmosphere. Therefore, the positive effect of HBPSi on improving the flame retardancy is attributed to the condensed phase mechanism. On the other hand, HBPSi/BCE resins exhibit improved dielectric properties (including decreased dielectric constant and loss) with increasing the content of HBPSi. More importantly, this investigation demonstrates that designing new polysiloxane with suitable chemical structure is important to develop high performance resins with attractive flame retardancy and dielectric properties.  相似文献   

11.
The isothermal cure of a dicyanate ester monomer by “in situ” Fourier transform infrared spectroscopy (FTIR) has been investigated. The degree of cyanate conversion and the kinetic parameters have been determined for cobalt catalyzed and uncatalyzed resin as well as for polysulfone (PSF) modified systems at different curing temperatures. The cyanate conversion increases with the increment of temperature and with the addition of a catalyst, but it does not vary with the addition of PSF. In all the systems studied, the rate of reaction showed a second-order dependence on the cyanate concentration in the kinetically controlled stage. Moreover, the addition of PSF generates a matrix with two-phases that changes in composition and morphology depending on the percent of added thermoplastic and curing temperature as observed by scanning electron microscopy.  相似文献   

12.
Silicone-based additives have been used as fire retardants for thermoplastics with the advantageous of improving the processing and the impact resistance of the polymers. In this work the influence of these additives on the curing kinetics of a vinyl ester resin was studied. Three silicone-based additives were used to modify the properties of the vinyl ester resin. The principal differences between them are the functional groups inserted in the polydimethylsiloxane chains. The additives were dispersed in the resin containing a commonly used mixture of initiator and catalyst methylethylKetone peroxide and cobalt-II octanoate, respectively. For some reactional mixtures N,N-dimethylaniline (DMA) was used as promoter. Differential scanning calorimetry (DSC) was used to perform the non-isothermal cure of the non-modified resin and of the resins modified with the additives. Ozawa´s, Kissinger´s and Ozawa´s isoconversional methods were used to determine the kinetic parameters. For resin cured in absence of DMA the silicone-based additives act as retardants for the curing reaction, a typical diluent effect, while in presence of this promoter the reaction enthalpy as well as the reaction rate were improved. This effect was attributed to specific interactions and reactions between DMA and the silicone-based additives that changed the curing mechanism as well as controlled the phase segregation.  相似文献   

13.
Curing characteristics of o-cresol novolac epoxy resin modified by 4,4-diaminodiphenylmethane bismaleimide (DDM-BMI) using FTIR were investigated and the glass transition temperature was measured. With the addition of DDM as hardener, the relative curing reaction conversion of DDM-BMI increased with equivalent weight ratio [R1 = (equiv wt summation of epoxy and DDM-BMI)/equiv wt of DDM] and weight ratio of epoxy and DDM-BMI (R2 = wt of epoxy resin/wt of DDM-BMI). Using phenol novolac resin (PN) as hardener, the curing reaction conversion of DDM-BMI was hardly changed, but the variation of that in the epoxy resin was observed with R2 change. © 1996 John Wiley & Sons, Inc.  相似文献   

14.
Two types of novel Polyhedral Oligomeric Silsesquioxanes respectively containing hydroxyl group and epoxy group (P-POSS and E-POSS) were achieved and evaluated. The structure had been characterized by IR spectra and NMR spectra. Dicyclopentadiene bisphenol dicyanate ester (DCPDCE) composites were then prepared using P-POSS and E-POSS respectively. Their effect on the curing kinetics, dielectric, mechanical, flame-retardant and thermal properties and water absorption of the resulting composites were investigated. The results suggested that the addition of modified POSS could facilitate the curing reaction of DCPDCE. Besides, the DCPDCE composites containing modified POSS exhibited excellent flame-retardant property over pure DCPDCE resin. Adding only a little amount as small as 1.5 wt% P-POSS or 2.5 wt% E-POSS could change the UL-94V of DCPDCE resin from V-2 to V-0. The composite with P-POSS exhibited better flame-retardant and thermal properties than the composite with E-POSS. However, composite filled with E-POSS presented better dielectric property and lower water absorption.  相似文献   

15.
A novel toughened cyanate ester (CE) resin with good dielectric properties and thermal stability was developed by copolymerizing 2,2′‐bis(4‐cyanatophenyl)iso‐propylidene (BCE) with a combined modifier (HBPSiEP) made up of hyperbranched polysiloxane (HBPSi) and epoxy (EP) resin. HBPSi was synthesized through the hydrolysis of 3‐(trimethoxysilyl)propyl methacrylate. The effect of differing stoichiometries of HBPSiEP on the curing characteristics and performance of BCE resin is discussed. Results show that the incorporation of HBPSiEP can not only effectively promote the curing reaction of BCE, but can also significantly improve the toughness of the cured BCE resin. In addition, the toughening effect of HBPSiEP is greater than single EP resin. For example, the impact strength of modified BCE resin with 30 wt% of HBPSiEP is 23.3 KJ/m2, which is more than 2.5 times of that of pure BCE resin, while the maximum impact strength of EP/BCE resin is about 2 times of pure BCE resin. It is worthy to note that HBPSiEP/BCE resins also exhibit improved thermal stability, dielectric properties, and flame retardancy, suggesting that the novel toughened CE resins have great potentiality to be used as a matrix for advanced functional composites or electronic packing resins. Copyright © 2009 John Wiley & Sons, Ltd.  相似文献   

16.
The early cure behavior of 4,4‐dicyanato 1,1‐diphenolethane resin with and without incorporating Cr(acac)3, Co(acac)3, and Cu(acac)2, respectively, as catalysts was investigated by gel permeation chromatography. The curing intermediates were separated by the column elution method and characterized by Fourier transform infrared, 1H, and 3C NMR spectroscopies. The results indicated that the formed dimer in the early cure stage is a straight chain containing a primary amino group. The formed triazine ring in the trimer has a strong catalytic effect on the remaining cyanate groups so that the reactivity of the trimers was significantly increased. The reactivities of the curing intermediates decreased with molecular size until 7‐mer was reached. The initial monomer consumption is described by second‐order‐rate kinetics. In the presence of metal acetylacetonates, the curing reactions may be accelerated, but they did not change the reaction path and preceding sequence of reactivities. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 3085–3092, 2001  相似文献   

17.
Graiver  D.  Decker  G.T.  Kim  Y.  Hamilton  F.J.  Harwood  H.J. 《Silicon Chemistry》2002,1(2):107-120
A convenient new process to make silicone/organic block and graft copolymers has been recently demonstrated. This dual copolymerization process combines conventional condensation polymerization of the siloxane segments with free radical polymerization of the organic vinyl polymer segments. The copolymerization process is relatively simple and economical compared with other copolymerization techniques as it uses commonly available starting materials and available process equipment. Silicone segments containing alkene side chains or end-groups are prepared in the usual way by polycondensation using an acid or base catalyst. The double bonds of the alkene groups are oxidized to carbonyls which are then used to initiate vinyl monomer polymerization and link the siloxane with the vinyl segments. This initiation step is based on a redox system of copper(II) salts which generates free radicals on the alpha carbons next to the carbonyl groups. This copolymerization process is relatively fast and proceeds at high yields.  相似文献   

18.
Bisphenol A dicyanate ester (BADCy) was modified with different amounts of an engineering thermoplastic, polysulfone (PS) to improve impact strength of the parent resin. Differential scanning calorimetry of the blends suggested that addition of PS widens the curing exotherm of the BADCy considerably. FTIR of cured neat resins indicated total conversion of cyanate functional groups into triazine rings by cyclotrimerization. The cured neat resins showed phase separated morphology with cyanate ester as the continuous phase. The modified resins were shown to have better thermal, hygrothermal and impact strength properties. However, when glass fiber reinforced composites were made using partially polymerized BADCy and PS, very little or no phase separation in the resin was noticed. Flexural and impact strength measurement of composites showed that PS modification has compromised the flexural properties and only retained the impact strength of the parent resin containing composite. This study thus suggests that improvements realized in thermoplastic modification of monomeric BADCy are not directly transferable to composites using a partially prepolymerized BADCy.  相似文献   

19.
In this work, we present the results of studying the effect of liquid carboxylated butadiene and polysulfide rubbers on the physicomechanical and adhesive properties of epoxy adhesive compositions with curing agents of different chemical nature—diethylene triamine and polyoxypropylene triamine. It is found that carboxylated butadiene rubbers are more effective modifiers than polysulfide rubbers because they yield a higher complex of properties. It is also shown that the change in the chemical nature of a curing agent has no significant effect on the properties of epoxy-rubber adhesive compositions, which allows one to control their key technological parameters without fear of losing strength characteristics.  相似文献   

20.
The paper presents the results of testing the thermal stability and flammability of butadiene-acrylonitrile rubber vulcanizates with different contents of combined acrylonitrile: Perbunan NT 1845 and Perbunan NT 3945 from Bayer, containing unmodified and bromine- or iodine-modified silica. The test results were obtained with the use of a derivatograph, measurements of flammability by the method of oxygen index, in air and also with the use of a cone calorimeter. The effect of the modification on the zeta potential was also examined. A considerable reduction in the flammability of nitrile rubber vulcanizates filled with silica can be obtained by the modification of filler with bromine or iodine. All the vulcanizates containing modified silica are self-extinguishing. An appropriate filling of NBR 39 vulcanizates with bromine-modified silica makes it possible to obtain non-flammable polymeric materials. They neither ignite nor glow under the action of a flame source for 30 s. The findings can be a rational basis for the synthesis of modified silica that can act as active filler and effective flame-retardant agent at the same time.  相似文献   

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