新型的飛機(jī)內(nèi)飾環(huán)氧樹脂預(yù) 畢業(yè)（設(shè)計）論文外文資料翻譯

1、 外文資料翻譯資料來源：資訊網(wǎng)文章名：Novel epoxy prepreg resins for aircraft interiors based on combinations of halogen-free flame retardants書刊名： From art to science作 者： Heth, J出版社：清華大學(xué)出版社，2002章 節(jié)：1.2 The Element of Digital Image Processing頁 碼：P2P7文 章 譯 名： 新型的飛機(jī)內(nèi)飾環(huán)氧樹脂預(yù) 浸樹脂 Novel epoxy prepreg resins for aircraft inte

2、riors basedon combinations of halogen-free flame retardantsThomas Neumeyer1 Anika Bauernfeind1 Verena Eigner1 Claudia Mueller1 Kerstin Pramberger1Volker Altstaedt1Received: 26 March 2016 / Revised: 29 October 2017 / Accepted: 12 December 2017Deutsches Zentrum fur Luft- und Raumfahrt e.V. 2018Abstrac

3、tHeat release and smoke emission are crucial characteristics regarding the burning behaviour of materials used inside thecabin of a commercial aircraft. In this work, an approach to enhance these properties of epoxy novolac-based resinformulations is presented. The phosphorus-based flame retardant D

4、OPO (9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide) is used in combination with inorganic flame retardants to merge different flame-retarding mechanisms. The effectsof the single flame-retarding components on the fire behaviour of the neat epoxy resin are investigated at first by conecalorimete

5、r measurements. Following, the interactions of combining (1) DOPO and ATH and (2) DOPO and boehmite arestudied systematically. It is shown that the sole DOPO modification effectively reduces the heat release by gas phasemechanisms, but at the same time increases the smoke production tremendously due

6、 to the flame inhibition and theresulting incomplete combustion. By adding inorganic flame retardants, this increase in smoke release can be compensatedfor. Furthermore, the aforementioned combination of DOPO and ATH leads to a synergistic effect on time to ignition. Firetesting on sandwich structur

7、es, consisting of prepreg face sheets based on the resin systems described before, reveals thatthe relevant characteristics to meet fire safety requirements for aircraft interiors can be fulfilled. Additionally, the influenceof the modifiers on the thermal and mechanical properties of the cured resi

8、ns are presented and discussed. The inorganicflame retardants significantly increase the fracture toughness of the originally rather brittle epoxy novolac resins fromaround 0.5 MPa m1/2up to approximately 0.8 MPa m1/2for the boehmite type used and up to 1.0 MPa m1/2for ATH at afiller loading of 33.3

9、 wt% in both cases.KeywordsPrepreg Epoxy Flame retardancy Halogen free Cone calorimetry1 IntroductionNowadays, aircraft interior parts such as sidewalls, ceilingsand hatracks are sandwich structures comprising a honeycomb core and prepreg face sheets on both sides. The termprepreg stands for pre-imp

10、regnated fibres whichdescribes a semi-finished, continuous sheet material consisting of fibres impregnated or saturated with a resinsystem, which can be stored prior to use 1.Today, thermosetting prepregs for aircraft interiors aremainly based on phenolic matrices because of theirexcellent FST behav

11、iour (FST=fire, smoke and toxicity)and their rather low price 2. But, indeed, there are disadvantages such as shrinking and elusion of volatiles during curing 3, which both lead to poor surface quality anddiminished mechanical properties of the cured parts. Incontrast to phenolic resins, epoxy novol

12、ac systems showminimal shrinkage during curing 4. Also, in comparisonto epoxy resins based on bisphenol A, they exhibit higherflame-retarding properties owing to their novolac backbone5, but nevertheless their intrinsic flame protection characteristics do not permit the use for the application infoc

13、us. Therefore, the epoxy novolac resins require modification using appropriate flame retardants.&Volker Altstaedtaltstaedtuni-bayreuth.de1Department of Polymer Engineering, University of Bayreuth,Universitaetsstrae 30, 95447 Bayreuth, Germany123CEAS Aeronautical Journal/10.1007/s13272-017-0279-7(012

14、3456789().,-volV)(0123456789().,-volV)2 State of the artIn the past, halogen-based flame retardants have beenwidely used in epoxy resins, especially in electronicapplications. Those substances mainly act in the gas phaseas their effect is based on the release of hydrogen halides6, 7. But halogen-bas

15、ed flame retardants cannot be usedinside an aircrafts cabin, as the resulting toxic combustionproducts would not allow for the necessary material certification. Flame retardants based on phosphorus representthe most important alternative 8, 9. Depending on thechemical nature of the modifier, phospho

16、rus-containingflame retardants can become active either in the solid or inthe gas phase, or else in both phases 2, 10, 11.An effective flame retardant for epoxy resin formulations is, in particular, the heterocyclic organic phosphoruscompound 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO)

17、 12, 13. Seibold investigated the influence of DOPO on the flammability of DGEBA- and epoxynovolac-based formulations with various hardeners by UL94 test and determination of the limiting oxygen index(LOI) 14. In all formulations, V0 as the highest levelwithin the UL classification can be achieved w

18、ith lowphosphorus contents of less than 3 wt%.Inorganic flame retardants represent another majorgroup of fire retardants. The most important substancesamong them are metal hydrates 15, such as aluminiumhydroxide (ATH) and magnesium hydroxide, with ATHbeing by far the most widespread due to its low c

19、osts 16.The physical action mechanism of these flame retardants isbased on the thermally induced decomposition (see alsoSect.3, Eqs. (1) and (2) and accompanying effects2, 6, 17. On the one hand, the decomposition reaction isendothermic and removes the heat of combustion and thusenergy. On the other

20、 hand, incombustible water vapour isproduced which dilutes in the gas phase and lowers theradical concentration. In addition, the alumina as a soliddecomposition product forms an inert barrier layer over thepolymer.So far, individual groups of flame retardants have beenmentioned. It is now obvious t

21、hat by combining differentflame retardant additives, more effective solutions may beachieved by the interaction of different mechanisms. Doring et al. already studied the effect of combinations ofDOPO and inorganic flame retardants on the flammabilityof epoxy novolac resins 18, 19. These studies sho

22、w thatthe phosphorus concentration required to achieve a UL94-V0 rating can be drastically reduced by the addition ofATH or boehmite. By adding 30% by weight of boehmiteto a DICY and fenuron-cured epoxy novolac resin, thenecessary phosphorus content for the classification V0 isreduced from 1.6 to 0.

23、4%. Using 30% by weight of ATHinstead of boehmite also requires only 0.4% by weight ofphosphorus in the formulation to achieve the classificationV0. But the work of Do ring et al. is limited to theassessment of flammability by means of the UL 94 test.Within the scope of the present work, the effects

24、 of suchflame retardant combinations should be evaluated for theheat and smoke release behaviour crucial for use in aircraftinterior components.3 MaterialsIn this study, a mixture of D.E.N. 438 and D.E.N. 431epoxy novolac resins, both obtained from DOW ChemicalCompany, was used. The mixing ratio was

25、 optimized withregard to the viscosity necessary for a hot melt prepreggingprocess. Table1presents the major characteristics of theresins used.The micronized dicyandiamide (DICY) grade AmicureCG-1200G, provided by Air Products and Chemicals, wasemployed as curing agent and used as received. DICY is

26、asolid latent hardener, which is often used in prepreg formulations 20. The imidazolium salt 1-ethyl-3-methylimidazolium dicyanamide (EMIMN(CN)2), availablefrom BASF SE as BasionicsTMVS 03, was used additionally as catalyst to enable a 140 C curing cycle 21.9,10-Dihydro-9-oxa-10-phosphaphenanthrene-

27、10-oxide(DOPO) was purchased from Krems Chemie ChemicalServices AG and used as reactive, phosphorus-based flameretardant compound for the epoxy resin. The product wasprovided in the form of white flakes. Thus, to improve themixing and miscibility of the material, the DOPO flakeswere crushed in a pla

28、netary ball mill. Triethanolaminesupplied by Sigma-Aldrich (98% purity) was applied ascatalyst for the fusion reaction (preformulation) of DOPOwith the epoxy resin (see Fig.1) according to 14, 22.Aluminium hydroxide (ATH) and boehmite were bothused as inorganic flame retardants in this study. Theadd

29、itives were kindly provided by Nabaltec AG in the formof white powders and were used as received. Table2summarizes the characteristics of the grades used in thiswork. The products were selected to be comparable interms of fire behaviour. Therefore, grades with identicalTable 1 Characteristics of the

30、 epoxy novolac resins used in this work(according to datasheets)Resin EEW (g/eq) FunctionalityD.E.N. 431 172179 2.7D.E.N. 438 176181 3.6EEWepoxy equivalent weightT. Neumeyer et al.123specific surface (BET) were chosen. The difference inparticle size distribution is a result of this primary selection

31、criterion.Both inorganic flame retardants decompose via anendothermic reaction at elevated temperature. The following equations describe the corresponding mechanismsfor ATH (Al(OH)3) (Eq. 1) and boehmite (AlOOH) (Eq. 2)15:2AlOH 3!Al2O33H2O DH1075 J=g; 12 AlOOH!Al2O3H2O DH700 J=g: 2The decomposition

32、of ATH starts at approximately200C, whereas boehmite begins to decompose at considerably higher temperatures of approximately 340C15.4 Experimental4.1 Preformulation of flame retardant epoxyresinsThe chemical incorporation of DOPO into the novolacepoxy resin was made through a preformulation process

33、 asdescribed by Seibold 14: at first, D.E.N. 438 and D.E.N.431 were mixed and degassed under vacuum (10 mbar) ina glass bulb at 100C for 1 h. Afterward, the resin systemwas heated to 120C and the appropriate amount of DOPOpowder was introduced and stirred continuously togetherwith the resin. Trietha

34、nolamine was added as a catalyst tothe mixture. Lastly, the temperature was elevated to 140 Cand maintained for 1.5 h. During the whole preformulationprocess, the resin system was continuously stirred. Afterthe preformulation process, the modified resin was cooleddown.4.2 Preparation of neat resin p

35、latesFor formulations without phosphorus modification, theepoxy novolac resins were blended in the appropriate ratioand heated to 80C. For preparation of plates containingDOPO, the applicable preformulation was selected insteadand heated to 80C. Then, for the formulations containingan inorganic flam

36、e retardant, the necessary amount of ATHor boehmite was added to the resin blend or the preformulation, respectively. The mixture was stirred for1520 min to ensure a homogeneous dispersion of theflame retardant. Afterward, the aminic hardener DICY wasintroduced under continuous stirring. Finally, th

37、e imidazolium salt was added and the mixture was stirred foranother 3 min.The whole formulation was degassed under vacuum(10 mbar) before it was poured into the preheated aluminium moulds (120C). The moulds were pretreated withan external release agent (Loctite Frekote 770-NC, HenkelAG). The neat re

38、sin plates were cured for 90 min at 140Cin a convection oven. Demoulding was carried out at roomtemperature.Fig. 1 Chemical reaction of DOPO with epoxy novolac resin (according to 18)Table 2 Characteristics of theinorganic flame retardants usedin this work (according todatasheets)Material Trade name

39、 D50(lm) D90(lm) BET (m2/g) Density (g/cm3)ATH APYRAL33 6 20 3 2.4Boehmite APYRALAOH 30 1.8 4.2 3 3.0Novel epoxy prepreg resins for aircraft interiors based on combinations of halogen-free1234.3 Cone calorimeter experimentsThe fire behaviour of the neat resin plates for flamingconditions was charact

40、erized using a cone calorimeter (FireTesting Technology, East Grinstead, UK) according to ISO5660. The samples with dimensions of100910093mm3were wrapped in aluminium foil andplaced horizontally under the cone heater using a retainerframe. The distance between the heating element and thespecimen was

41、 fixed at 25 mm. A heat flux of 35 kW/m2was employed for all tests. The measurements were done induplicate. Before fire testing, all samples were conditionedfor 48 h at 23C and 50% relative humidity in a climatecabinet.4.4 Thermal analysis of neat resinsDynamic mechanical analysis (DMA) in torsion m

42、ode wasperformed on cured rectangular specimens of5091092mm3. The specimens were measured from 25to 250 C with a heating rate of 3 K/min. The frequencywas set to 1 Hz and a deformation of 0.1% was utilized.The glass transition temperature (Tg) was taken as thetemperature at which the loss factor rea

43、ched its peak.Rubber elasticity theory was used to calculate theaverage molecular weight between cross-links (Mc) of theformulations by means of the following relationship 23:Mc /qRTGe; 3whereMcis the molecular weight between cross-links, Uafront factor, qthe density at the absolute temperature T,Rt

44、he gas constant, Tthe absolute temperature 50 K aboveTg andGe the equilibrium shear modulus. To apply thisequation, equilibrium shear modulusGeis determined fromDMA curves at the rubbery state, which is taken at 50 KaboveTg. The front factor is the ratio of the mean squareend-to-end distance of a ne

45、twork segment to that of arandomly coiled chain, and, following Katz and Tobolsky24, is taken to be approximately 1.88. The change indimension of the specimens from room temperature toTwas also obtained by DMA measurements. Assumingisotropic expansion, the volume of a specimen at Twascalculated by a

46、dding the appropriate percentage volumechange to the volume at room temperature. The hightemperature density was then calculated as the ratio ofmass to volume atT.4.5 Mechanical characterizationBased on linear elastic fracture mechanics (LEFM), thecritical stress intensity factor (KIc) was obtained

47、from theopening mode test according to ISO 13586, performed oncompact tension (CT) specimens. A sharp V-notch wasmachined into the specimen and then a sharp precrack wasgenerated by tapping a razor blade. Tests were carried outusing a universal testing machine model Zwick Z 2.5 kNunder controlled at

48、mosphere conditions (23C and 50%relative humidity) and a crosshead speed of 10 mm/min.A detailed analysis of the fracture surfaces was carriedout using a Zeiss 1530 scanning electron microscope(SEM) equipped with a field emission cathode.5 Results and discussion5.1 Fire behaviour5.1.1 Influence of D

49、OPO modification on the fire behaviourof cured neat resinsHeat release rate (HRR) and total heat release (THR)determined by cone calorimeter experiments for the formulation without phosphorus as well as for DOPO-modified resins with varying phosphorus contents are shown inFig.2, while the correspond

50、ing characteristics are summarized in Table3. It can be seen that the time to ignitiontigis not affected significantly by the DOPO modification.The HRR vs. time curves exhibit a small shoulder beforereaching the maximum of heat release and decrease at firstsharply and then rather slowly after exceed

51、ing the peakheat release rate (PHRR). This slow decrease indicates thata char layer has been formed 25. The char formation isproven by the residues obtained after the cone calorimeterexperiments. PHRR and total heat evolved (THE) diminishconsiderably with increasing phosphorus content. At aFig. 2 He

52、at release rate (HRR) and total heat release (THR) forformulations with varying phosphorus contentsT. Neumeyer et al.123phosphorus content of 1.9 wt%, the PHRR decreased by70% and the THE by 56% compared to the unmodifiedformulation.Still, at the same time the smoke production increasedsignificantly

53、 with rising amount of phosphorus within theformulation (see Fig. 3). As the rise in smoke production isa typical result of incomplete combustion, it indicates adominant gas phase mechanism of the phosphorus throughflame inhibition 25,26. The combustion efficiency, whichis the THE divided by the mas

54、s loss (THE/ML), representsthe gas phase activity. The lower the THE/ML in comparison to the non-flame-retarded material, the higher is theflame inhibition or dilution action of the flame retardant inthe gas phase 27. Table 3clearly shows a reduction of thecombustion efficiency with increasing phosp

55、horus content.In combination with the rise in smoke production, theseresults confirm the already mentioned dominant gas phaseaction of phosphorus.5.1.2 Influence of inorganic flame retardants on the firebehaviour of cured neat resins Influence of ATH The influence of the inorganicflame retardant ATH

56、 on the burning behaviour of the formulations without phosphorus is shown in Fig.4, whileTable4 contains the corresponding quantitative characteristics. It can be clearly observed that the time to ignitionis extended with increasing content of the inorganic modifier. A content of 33.3 wt% ATH increa

57、ses the time toignition by 35% compared to the resin system withoutflame retardant. As stated in Sect.3, ATH starts decomposing at temperatures around 200C15, which is beforeignition. During the decomposition (see Eq. 1), watervapour is released from the specimen and dilutes thecombustible gases, th

58、us leading to an extension of the timeto ignition.The shape of the heat release versus time curves changesdue to the addition of the inorganic flame retardant: Thepeak heat release rate decreases and is shifted to the rightwith increasing content of flame retardant. This changeunderlines the effecti

59、veness of ATH in the initial stage of afire. An ATH content of 33.3 wt% reduces the PHRR bymore than 75% compared to the unmodified resin system.The total heat release (THE) is lowered by approximately35% at the same time. On the one hand, the addition of theinorganic flame retardant reduces the pol

60、ymeric fractionwithin the formulation and therefore lowers the heatrelease. On the other hand, the release of water vapourduring the decomposition of ATH decreases the radicalconcentration within the gas phase and therefore leads to alower thermal feedback into the pyrolysis zone, too. Thereduction