二甲醚作為泡沫聚氨酯發(fā)泡劑的可行性研究

1、二甲醚作為泡沫聚氨酯發(fā)泡劑的可行性研究賈潤(rùn)禮 梁麗華（華北工學(xué)院塑料研究所，工程塑料國(guó)家工程研究中心華北工學(xué)院聯(lián)合研發(fā)中心 山西太原030051）摘 要：分析了二甲醚(DME)作為發(fā)泡劑替代CFC-11用于聚氨酯（PU）泡沫的可行性。DME毒性極低，化學(xué)性質(zhì)穩(wěn)定，可長(zhǎng)期儲(chǔ)存而不分解或轉(zhuǎn)化。DME在大氣層中的壽命很短，約10天左右，在大氣層中被降解為二氧化碳和水，ODP值為零，因而不會(huì)造成環(huán)境污染和影響臭氧層。DME沸點(diǎn)低，可燃；對(duì)極性和非極性有機(jī)物質(zhì)均有高度溶解性，易溶于水，與大多數(shù)溶劑都能混勻，與一種非燃性溶劑（如HFC或水）混合就能得到非燃性混合物，它與少量高沸點(diǎn)HFC及高沸點(diǎn)溶劑混合能得

2、到常溫為液態(tài)、不燃的混合物。DME的上述特性既可保證PU泡沫的生產(chǎn)安全又具有對(duì)現(xiàn)行PU泡沫生產(chǎn)設(shè)備的廣泛適應(yīng)性，同時(shí)DME與聚醚多元醇的互溶性有利于提高PU泡沫的發(fā)泡效率和尺寸穩(wěn)定性，此外，DME還具有價(jià)格低、來(lái)源廣的優(yōu)點(diǎn)。DME可以作為發(fā)泡劑用于各種PU泡沫的生產(chǎn)，并且可能是一種理想的CFC-11替代品。關(guān)鍵詞：聚氨酯泡沫；二甲醚；發(fā)泡劑；CFC-11；替代品隨著泡沫聚氨酯(PU)行業(yè)CFC-11發(fā)泡劑替代行動(dòng)的實(shí)施，一批CFC-11替代品及其相關(guān)技術(shù)得到推廣應(yīng)用，一些新型發(fā)泡劑在研究中，但有關(guān)二甲醚作為發(fā)泡劑用于PU泡沫尚未見報(bào)道。筆者認(rèn)為，二甲醚（DME）是一種具有特殊性能的物質(zhì)，非常適

3、合作為PU發(fā)泡劑。本文分析了DME作為PU發(fā)泡劑的可行性。1 DME的性能1.1 化學(xué)性能DME（CH3OCH3，相對(duì)分子質(zhì)量46.10）是乙醇的同分異構(gòu)體，化學(xué)性質(zhì)穩(wěn)定，只與鹵素或鹵化氫在低溫下反應(yīng)生成加成化合物，與發(fā)煙硫酸或三氧化硫進(jìn)行氣相反應(yīng)生成硫酸二甲酯，與苯胺蒸汽反應(yīng)生成N,N-二甲基苯胺；熾熱時(shí)分解；可長(zhǎng)期儲(chǔ)存而不分解或轉(zhuǎn)化，長(zhǎng)期儲(chǔ)存不易形成過(guò)氧化物，不會(huì)因氯代物溶劑而引起氯化。在大氣層中的壽命約10天左右，在大氣層中被降解為二氧化碳和水，臭氧消耗潛值（ODP）為零，因而不會(huì)造成環(huán)境污染和影響臭氧層。1.2 物理性能DME熔點(diǎn)138.5，沸點(diǎn)（0.1MPa）24，密度（液態(tài)20）0

4、.666 g/cm3，20蒸氣壓 (表壓) 0.4 MPa，可燃，比密度（DME氣體/空氣之密度比值）1.6，蒸發(fā)熱484 kJ/kg，比熱容2.37 kJ/kg·K，閃點(diǎn)5.6，空氣中爆炸極限3.4%18.6%（體積），著火點(diǎn)235，自動(dòng)著火溫度350。DME無(wú)色、無(wú)味、無(wú)臭，粘度和表面張力較低，對(duì)極性和非極性有機(jī)物質(zhì)均有高度溶解性，易溶于水，1個(gè)大氣壓(0.1 MPa)下在水中的溶解度為34%（質(zhì)量分?jǐn)?shù)）。DME與大多數(shù)溶劑如碳?xì)浠衔?、鹵代烷、醇、醚、酰、胺、酯、醛類等都能混勻，它與一種非燃性溶劑混合就能得到非可燃性混合物。1.3 毒性DME的急性、亞急性、慢性吸入毒性極低。大

5、白鼠暴露4h半數(shù)致死濃度（LC50）為16.4%，暴露30 min的LC50為39%。大白鼠10天亞急性試驗(yàn)，暴露濃度為5(5×104 ppm)時(shí)體重增加較少，濃度為1時(shí)無(wú)變化。慢性吸入毒性試驗(yàn)，大白鼠吸入30天，在濃度0.1、1時(shí)未見毒性；吸入90天，濃度為0.2、1、2時(shí)未見毒性。當(dāng)DME在空氣中的濃度在20或以上時(shí)，才有可能形成對(duì)人的心臟有作用的濃度。DME在毒性試驗(yàn)中沒有發(fā)生過(guò)致突變作用，也沒有在動(dòng)物試驗(yàn)中發(fā)生過(guò)致畸現(xiàn)象。2 用于水發(fā)泡體系DME雖可燃，但具有與不燃性物質(zhì)混合獲得不燃性物質(zhì)的特性，因此可與水、HFC等混合而降低或消除其可燃特性。DME/水溶液還能產(chǎn)生一種零火焰

6、延伸性能，對(duì)含水14%、乙醇6%和DME80%的混合液所作的火焰延伸測(cè)定結(jié)果為零，這一特性大大減少了DME在存儲(chǔ)和使用期間燃燒、爆炸的危險(xiǎn)性。DME可與水互溶的特性使其很容易應(yīng)用于全水發(fā)泡路線，DME與少量水混合作為發(fā)泡劑，由于減少用水量而導(dǎo)致CO2 發(fā)氣量減少，從而有利于改善全水發(fā)泡PU泡沫性脆、強(qiáng)度低、穩(wěn)定性差、絕熱性差的缺陷，并可減少多異氰酸酯的用量。DME/水混合發(fā)泡劑使用效果相當(dāng)于在CFC-11替代技術(shù)發(fā)展初期為減少CFC-11的用量而采用的CFC-11/水混合發(fā)泡劑，其發(fā)泡工藝與設(shè)備與CFC-11、HCFC-141b體系相同，泡沫性能包括絕熱性能得到各領(lǐng)域認(rèn)可。在這里，由于DME的

7、強(qiáng)溶劑特性以及與水的互溶性，泡沫性能可能比CFC-11/水混合發(fā)泡劑體系要好。由于DME的低粘度與低表面張力及強(qiáng)溶劑特性，用于全水發(fā)泡體系中可顯著降低體系粘度，因而降低了對(duì)多元醇粘度的要求，即允許使用較高粘度的多元醇，并可提高體系中各組分的混勻性。雖然DME沸點(diǎn)較低，但與水互溶后DME/水的共沸點(diǎn)可顯著提高，因此在水發(fā)泡體系中的各種發(fā)泡工藝中應(yīng)用時(shí)仍可使用現(xiàn)行設(shè)備。3 與烷烴發(fā)泡劑的比較烷烴類發(fā)泡劑有環(huán)戊烷、正戊烷、異戊烷（統(tǒng)稱為戊烷類發(fā)泡劑）、正丁烷、異丁烷等，其中戊烷類發(fā)泡劑因沸點(diǎn)較高而得到較廣泛的應(yīng)用。戊烷類發(fā)泡劑受到重視的原因是由于其零ODP值、溫室效應(yīng)很小、無(wú)毒、對(duì)環(huán)境影響極小、常溫

8、下為液態(tài)、資源豐富、價(jià)格低。與CFC-11相比，戊烷類發(fā)泡劑有三個(gè)缺點(diǎn)：易燃、易揮發(fā)，爆炸極限1.3%8%，為保證生產(chǎn)安全， 必須對(duì)現(xiàn)有計(jì)量、儲(chǔ)存、發(fā)泡設(shè)備進(jìn)行較大改造；戊烷在聚醚多元醇中的溶解性較差，必須使用經(jīng)改性的多元醇和特殊助劑；戊烷的氣相熱導(dǎo)率較高，制得的PU硬泡絕熱性能略差。DME同樣具有零ODP值、溫室效應(yīng)很小、無(wú)毒、對(duì)環(huán)境影響極小、資源豐富、價(jià)格低的優(yōu)點(diǎn)。DME本身在常溫下呈氣態(tài)，但如果與少量高沸點(diǎn)烷烴（如庚烷、辛烷）混合可得到常溫下液態(tài)的混合物。DME爆炸極限比戊烷高一倍，因而安全性相對(duì)較高。與少量HFC或HCFC混合就可以達(dá)到不燃效果，如以DME、少量辛烷和HFC混合成復(fù)合發(fā)

9、泡劑則可以達(dá)到常溫下液態(tài)及不燃效果，因而完全可以適應(yīng)現(xiàn)行設(shè)備。此外，DME與多元醇的互溶性有利于提高PU泡沫的發(fā)泡效率和尺寸穩(wěn)定性。由于DME表面張力小、粘度低，泡沫易出現(xiàn)泡孔直徑大而不勻現(xiàn)象，這一點(diǎn)在使用成核劑（如氣相二氧化硅）后可完全解決。4 與氟系發(fā)泡劑的比較含氟發(fā)泡劑有HCFC、HFC、全氟烷烴（PFA）、氟代醚（HFE）四類。HCFC發(fā)泡劑在CFC-11替代技術(shù)發(fā)展過(guò)程中作為過(guò)渡性發(fā)泡劑發(fā)揮了重要作用，發(fā)泡工藝性與泡沫性能較好，但由于其ODP值不為零，故被列為限期禁用的發(fā)泡劑。HFC發(fā)泡劑的ODP值為零，大多數(shù)HFC不燃、低毒，被認(rèn)為是有前途的發(fā)泡劑，其中低沸點(diǎn)發(fā)泡劑以HFC-134

10、a、HFC-152a為代表，高沸點(diǎn)發(fā)泡劑以HFC-356、HFC-365mfc、HFC-245fa為代表。低沸點(diǎn)HFC也稱氣態(tài)HFC，零ODP 值，在大氣層中壽命較短，性能穩(wěn)定，用量比CFC-11少，缺點(diǎn)是常溫為氣態(tài)工藝操作不便、在多元醇中溶解度低、熱導(dǎo)率較高。高沸點(diǎn)HFC目前被認(rèn)為是綜合性能最好、較理想的CFC替代品，其中只有HFC-365mfc一種可燃，發(fā)泡工藝性好，對(duì)現(xiàn)行設(shè)備的適應(yīng)性強(qiáng)，高沸點(diǎn)HFC目前使用尚不普及，原因是產(chǎn)量少價(jià)格高。PFA中可用的發(fā)泡劑有全氟戊烷、全氟己烷等，具有零ODP值、沸點(diǎn)適宜、不燃、無(wú)毒、熱導(dǎo)率低等優(yōu)點(diǎn)，同時(shí)也有在多元醇中溶解度低、價(jià)格高、發(fā)泡效率低、溫室效應(yīng)

11、嚴(yán)重等缺點(diǎn)，現(xiàn)處于小范圍試用階段。氟代醚有HFE-245mf、HFE-347mcf、HFE-347pcf，綜合性能比HFC-245fa好，特別是在聚醚多元醇中的溶解性較好，但目前處于研究階段。DME在大氣層中的壽命比上述任何一種含氟發(fā)泡劑都短，并且成本最低。如單獨(dú)使用則發(fā)泡工藝性相當(dāng)于氣態(tài)HFC，但由于DME在多元醇中的高溶解性，泡沫性能將好于HFC發(fā)泡體系的泡沫；如與少量高沸點(diǎn)溶劑及高沸點(diǎn)HFC混合完全可達(dá)到不燃和常溫為液體的狀態(tài)，能夠適應(yīng)高沸點(diǎn)HFC發(fā)泡體系現(xiàn)行設(shè)備工藝。5 結(jié)語(yǔ)DME的特性符合對(duì)CFC-11替代品的要求，并且是一種低成本的CFC-11替代品，目前DME國(guó)際市場(chǎng)價(jià)格400美

12、元/噸，國(guó)內(nèi)產(chǎn)品價(jià)格3500元/噸。我國(guó)目前DME年產(chǎn)量為20000噸，在建項(xiàng)目和已批準(zhǔn)立項(xiàng)的待建項(xiàng)目設(shè)計(jì)生產(chǎn)能力共計(jì)140萬(wàn)噸/年，完全可滿足未來(lái)需求。DME可與HFC或水混合而實(shí)現(xiàn)不燃，從而保證生產(chǎn)安全；還可與高沸點(diǎn)溶劑混合調(diào)整其沸點(diǎn)以滿足生產(chǎn)需要。DME可單獨(dú)或作為混配型發(fā)泡劑用于各種PU硬泡發(fā)泡工藝，并且基本能適應(yīng)現(xiàn)行設(shè)備。DME的廣譜強(qiáng)溶劑特性優(yōu)于現(xiàn)有的其它任何一種CFC-11替代品發(fā)泡劑，不僅能使PU泡沫更加均勻細(xì)膩，同時(shí)兼有分散劑作用而有利于發(fā)泡體系中各助劑的均勻分散。參考文獻(xiàn)1 賈潤(rùn)禮.新型氣霧制品拋射劑二甲醚.企業(yè)技術(shù)開發(fā),1996,(1):13142 Jiarunli. P

13、roperties and Application of Dimethyl Ether. In: The International Autumn Seminer or Propellant, Explosives and Pyrotechnies. Beijing of China.19963 國(guó)家環(huán)?？偩謱?duì)外經(jīng)濟(jì)合作領(lǐng)導(dǎo)小組辦公室等.聚氨酯硬泡CFC-11替代技術(shù)手冊(cè).2002.2739The Feasibility Study of Dimetyl Ether as a Blowing Agent Used for Polyurethane FoamJia Runli Liang Lih

14、ua(Plastics Institute, North China Institute of Technology, Shanxi Taiyuan 030051)(Union R&D Center , National Engineering Research Center of Engineering Plastics & North China Institute of Technology)Abstract: The feasibility of dimethyl ether (DME) used for polyurethane foam as a blowing a

15、gent instead of CFC-11 is discussed. DME has very low toxicity and steady chemical properties, it can be stored for a long time without decomposition or inversion. But it has very short lifetime (about 10 days) in atmosphere and then degrade s into water and CO2, and has zero value of ODP. So it is

16、considered to be no influence on environment and ozonosphere. DME has low boiling point and is ignitable. An important property of DME is its high solubility on polarity and non-polarity organic substance, such as hydrocarbon, alkyl halide, alcohol, ether, acyl, amine, ester, aldehyde and so on. Whe

17、n mixed with a kind of non-inflammable solvent such as HFC, the mixture is non-inflammable. Above properties of DME, can not only insure production safety but also adapt to all production equipment of PU foam, and profit to increase expanding efficiency and dimensional stability. Besides, it is chea

18、p and rich. DME can be used for PU foam as a new blowing agent to substitute CFC-11.Keywords: polyurethane foam; dimethyl ether; blowing agent; CFC-11; substitute作者簡(jiǎn)介：賈潤(rùn)禮 華北工學(xué)院塑料研究所所長(zhǎng)，聯(lián)合研發(fā)中心主任。主要從事塑料改性及加工工藝研究，發(fā)表論文30余篇，專著8部（其中主編5部）。社會(huì)兼職：山西省塑料行業(yè)協(xié)會(huì)副理事長(zhǎng)及專家委員會(huì)副主任，工程塑料應(yīng)用編委等。電子信箱：。The Feasibility Study of

19、Dimetyl Ether as a Blowing Agent Used for Polyurethane FoamJia Runli Liang Lihua(Plastics Institute, North China Institute of Technology)(Union R&D Center, National Engineering Research Center of Engineering Plastics & North China Institute of Technology) ABSTRACT: Purpose: To studying the f

20、easibility of dimethyl ether (DME) used for polyurethane foam as a blowing agent instead of CFC-11. Methods:Acording to the properties of DME, the study discusses whether DME can meet the demands of the substitution of CFC-11. DME is the isomer of ethanol , which can react with only few matters such

21、 as halogen or halogen hydride, fuming sulfuric acid or sulfuric trioxide, and aniline vapor due to its steady chemical properties. DME can be stored for a long time without decomposition or inversion. But it has very short lifetime (about 10 days) in atmosphere and then degrades into water and CO2

22、, and has zero value of ODP. So it is considered to be no influence on environment and ozonosphere. It has very low acute, subacute and chronic inhalation toxicities, and might influence to peoples heart only with very high concentration in air. DME has low boiling point and is ignitable. An importa

23、nt property of DME is its high solubility on polarity and non-polarity: soluble easily in water and many other solvents such as hydrocarbon, alkyl halide, alcohol, ether, acyl, amine, ester, aldehyde and so on. When mixed with a kind of non-inflammable solvent, the solution becomes non-inflammable,

24、and if, mixed with high boiling point HFC and high boiling point solvent, the mixture becomes liquid and non-inflammable at room temperature. Results: Above properties of DME, can not only insure production safety but also adapt to all production equipments of PU foam, and profit to increase expandi

25、ng efficiency and dimensional stability. Besides, it is cheap and rich. Conclusion: DME can be used for PU foam as a new blowing agent to substitute CFC-11. KEYWORDS: polyurethane foam, dimethyl ether, blowing agent, CFC-11, substitute.With the substitution action of CFC-11 blowing agent in the fiel

26、d of polyurethane(PU) foam, a number of substitutes of CFC-11 have been used, and some new blowing agents are exploring. But there are not reportages about DME being blowing agent used for PU foam. It is considered that dimethyl ether is a kind of matter which has special properties, and is very sui

27、t to be a blowing agent of PU. The study discusses the feasibility of DME as blowing agent of PU.1 Properties of DME1.1 Chemical properties DME(CH3OCH3, relative molecular weight 46.10) is the isomer of ethanol. It has stable chemical properties and only few reactions can take place: reacting with h

28、alogen or halogen hydride at low temperature to form addition compound, with fuming sulfuric acid or sulfuric trioxide in gas phase to form dimethyl sulfate, with aniline vapor to form N,N-dimethyl aniline, and disintegrating when red heated. DME can be stored for a long time without decomposition a

29、nd inversion and peroxide formation. DME can not be chloridized by chlorination solvent. It can just exist ten days in atmosphere and then will degrade into CO2 and water. Its ODP value is zero, so can not endanger to environment and ozonosphere.1.2 Physical propertiesDME has melt point -138.5,boili

30、ng point(0.1MPa)-24,density(liquid state 20)666kg/m3 , manometer pressure (20)0.4MPa, specific density（gas/air）1.6，heat of evaporation 484kJ/kg，specific heat capacity 2.37kJ/kgK. It is ignitable, with flash point is -5.6, explosion limit in air 3.4%18.6%(V)，fire point 235，spontaneous ignition temper

31、ature 350. DME is colorlessness, flavorness and odorless. It has very low viscosity and surface tension, and is highly soluble in polarity and non-polarity. It is easily soluble in water and the solubility is 34%(W) at 1 atm. DME can also be homogeneously mixed with most solvents such as hydrocarbon

32、, alkyl halide, alcohol, ether, acyl, amine, ester and aldehyde etc. If mixed with a kind of non-inflammable solvent, the mixture becomes non-inflammable.1.3 ToxitiesThe acute, subacute and chronic inhalation toxicity tests on rats showed that DME is very low toxic: the rats exposed, for four hours

33、half the pieces lethal concentration (LC50) was 16.4%, for 30min LC50 was 39%; ten days subacute tests on rats, rats gained a few weight at exposed concentration 5×104ppm, and gained zero weight at 1×104ppm; chronic inhalation tests, rats had not been found toxity for 30days at 1×103p

34、pm,1×104ppm, and for 90days at 2×103ppm,1×104ppm,2×104ppm. Only when the concentration of DME in air up to 2×105ppm or above, it might influence peoples' hearts.During the toxity tests, mutation and teratogenicity phenomenon about DME were not find.2 Application in water

35、 expanding systemsAlthough DME is inflammable, it may become non-inflammable matter by mixing with non-inflammable matter. That is to say its inflammable performance can be eliminated or reduced by mixed with water or HFC. The mixture of DME/water has a important property of “zero fire elongation”,

36、and test result of fire elongation for a mixture which contents 14% water, 6% alcohol and 80% DME showed zero value. Above property decreases greatly flammable or explosive danger of DME during storage and usage period.The mutual solution property of DME with water makes it easy to be used for water

37、 expanding system of PU foam. Using the mixture of DME and a few water as blowing agent. because of water reduction, can improve shortcomings of water expanded PU foam of brittleness, low strength, low stability and low thermal insulation due to water reduction, so as to reduce quantities of polyiso

38、cyanate. In the first development stage of CFC-11 substitute technique, CFC-11/water mixture was used as blowing agent in PU foam for reducing CFC-11, the expanding process and used equipments were same as that of CFC-11 or HCFGC-141b, and the foam properties of PU including thermal insulation were

39、accepted. Herein, the usage effectiveness of mixing blowing agent of DME/water corresponds with that of CFC-11/water, and the foam may be better than CFC-11/water system because DME has strong solvent property and compatibility with water.Because of the low viscosity, low surface tension and strong

40、solvent property, DME can remarkably decrease the viscosity of water expanding system, and decreases request to viscosity of polyol, in other words, allows to use higher viscosity polyol, and raises mixing homogenization of components.Although DME has lower boiling point, the azeotropic point of DME

41、/water will be higher than DME. So the current equipments of any kind of expanding process in water blowing system can still be used without reformation when DME is used.3 Comparing with paraffin blowing agentsParaffin blowing agents contain cyclopentane, n-pentane and isopentane (generally called p

42、entane blowing agents), n-butane, isobutene etc., within which, pentane has found more applications. The reason of pentane attached importance to be blowing agents are zero value of ODP, very little greenhouse effect, non-toxic, very small influence on environment, liquid state at normal temperature

43、, rich resources and lower price. Comparing with CFC-11, there are three disadvantages over pentane: first, it is ignitable and volatile, its explosion limit is 1.3%8%. To insure production safety, all meterage, storage and expanding equipments must be modified large scale; second, pentane has lower

44、 solubility in polyether polyol, so it is must to use modified polyether polyol and special assistants. Third, gaseous pentane has higher heat conductivity, so thermal insulation property of PU foam expanded by it is not so good.Similarly, DME has zero ODP, very little greenhouse effect, non-toxic,

45、very small influence to environment, rich resources and lower price. Though DME is gaseous at normal temperature, if mixed with some higher boiling point paraffin (such as hexane or octane) the mixture can change into liquid state at normal temperature. Its explosion limit is double times as pentane

46、, so the safety is relative higher than pentane. Non-inflammability can be reached by mixing with some HFC or HCFC, and if mixed with some octane and HFC, the mixture will be liquid at normal temperature and non-inflammable. So DME can completely suit to current equipments. Besides, the compatibilit

47、y of DME and polyol profits to increase expanding efficiency and dimension stability of PU foam.Because of lower surface tension and viscosity, DME is easy causative of large hollows and not homogenization within PU foam, but these problems can be easily solved with nucleating agent such as gaseous

48、silica.4 Comparing with fluorine series blowing agentsFluoro blowing agents include HCFC, HFC, perfluoroparaffin (PFA) and fluoroether (HFE) four races. As transitivity blowing agents, HCFC played important roles in the developing process of CFC alternative technique, which have good expanding proce

49、ss and foam properties. But because of its non zero ODP, it will be forced to wash out in limited time. HFC have zero ODP value, most of them are non-inflammable and low poisonous, are considered to be bright future. Among HFC, HFC-134a and HFC-152a are representatives of low boiling point blowing a

50、gents, and HFC-356, HFC-365mfc and HFC-245fa are representatives of high boiling point blowing agents. Low boiling point HFC can also be called gas phase HFC, have zero ODP, short lifetime in atmosphere, stable properties. HFC also have some disadvantages: gas state at normal temperature inconvenien

51、t to process operation, low solubility in polyol and higher thermal conductivity. High boiling point HFC are considered to be best synthesis properties and relative ideal substitute because they have good expanding process and very suit to current expanding equipments, and only HFC-365mfc is inflamm

52、able. High boiling point HFC have not been widely used by now because of few output and high price. Perfluoropentane and perfluorohexane are useable blowing agents among PFA, which have many advantages such as zero ODP, suitable boiling point, non-inflammable, nonpoisonous and low heat conductivity,

53、 at same time which have many disadvantages such as low solubility in polybasic alcohol, high price, low expanding efficiency and serious greenhouse effect. Now PFA are used at practice stage. HFE include HFE-245mf, HFE-347pcf and HFE-347pcf. Their synthesis properties are better than HFC-245fa, especially, higher solubility in polyether polyol. But they are under development at present.DME has shortest lifetime in atmosphere and lowest price than above any other fluoro blowing agents. The expanding process using DME is identify to that of HFC, but the properties will be better