聚丙烯改性及其发泡行为的研究
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摘要
聚丙烯发泡材料具有优异的机械性能、突出的耐高温稳定性及耐环境应力开裂性、良好的降解性能,因此其正逐渐取代其他发泡材料而被广泛应用。但是由于聚丙烯自身结构特点,使其发泡过程很难控制,从而影响了工业化的进程。本文诣在确定可行的聚丙烯发泡材料制备工艺并对聚丙烯进行共混改性以提高其发泡性能,为工业化生产聚丙烯发泡材料作理论上和实验上的研究探索,全文分为三部分。
首先,对市售产品EPP珠粒进行表征分析。采用反光显微镜、扫描电子显微镜(SEM)、浸渍法、红外光谱仪(FT-IR)以及二甲苯抽提等方法对其泡孔形貌、密度、成分以及交联度等进行测定。结果表明,EPP珠粒为非交联闭孔泡沫材料,密度0.01~0.04g/cm3,发泡剂为惰性气体CO2。
其次,探索发泡工艺。三种发泡方法:直接挤出化学发泡法、两步化学发泡法、scCO2釜压法。利用扫描电子显微镜(SEM)、浸渍法对产品泡孔形貌、泡孔尺寸、泡孔密度以及材料密度、发泡倍率进行测定。结果表明,只有scCO2釜压法实现了普通PP的发泡,不添加任何添加剂,且材料外观规整,力学性能优异,泡孔密度高,发泡后材料最低密度达到0.1g/cm3以下,可控发泡倍率稳定在1~10倍,最高发泡倍率12~16倍,使用该方法对HMSPP进行发泡,最高发泡倍率可达31倍。并探讨了处理时间、温度、压力、卸压速度、冷却方式等因素对发泡倍率和泡孔结构的影响。确定了最佳发泡温度及其对应的压力为187~195℃、18.3~19.0MPa。
最后,对聚丙烯进行共混改性并探讨其改性后的发泡性能。采用单螺杆挤出机、开炼机、造粒机使用LDPE、HDPE对PP进行共混改性,改性后粒料通过RLS型熔体流动速率测定仪、DSC测试其熔体流动速率(MFR)、熔点;采用scCO2釜压法进行发泡实验,通过扫描电子显微镜(SEM)、浸渍法对产品泡孔形貌、泡孔尺寸、泡孔密度以及材料密度、发泡倍率进行测定。结果表明,随着LDPE、HDPE的加入,PP的MFR先降低后升高,熔点先升高后降低,在含量为30%时,MFR出现极小值、熔点出现极大值;泡孔密度更高,未出现泡孔合并、坍塌现象,说明加入PE树脂对PP进行共混改性可实现其发泡能力的优化。
Foamed polypropylene will be used widely in many fields such as packing and heat insulation material and so on, because of its outstanding mechanical properties, excellent thermal stability, well enduring environmental stress crack and good degradation performance. But the structural characteristic of polypropylene makes its foaming course hard to be controlled and this has affected the process of its large-scale industrialisation. This research is a preparative for the project of "Preparation of Expandable Polypropylene Particles " of XIN DA Co. Lit. of Heilongjiang province. The paper is divided into three parts.
(1) Characterization of EPP purchased from some foreign-funded enterprises. Reflective microscope, scanning electron microscopy (SEM), dipping method, FT-IR and extraction by dimethylbenzene were used for characterizing the cell morphologies、density、component and crosslinking degree. The results showed that the bubbles was closed, the density was between 0.01g/cm3 to 0.04g/cm3, and the particles were non-crosslinked which may be expanded by CO2. Basesed on the information we summed up the preparative methods of EPP: extrusion foaming processes and batch foaming process.
(2) The preparation technology of foamed polypropylene. Three methods were used for foaming: direct extrusion foaming processes with chemical foaming agent, two steps foaming processes with chemical foaming agent and batch foaming process with super critical carbon dioxide (scCO2). The cell morphologies were scanned by SEM, and densities were measured by dipping method. As a result, the batch foaming process with scCO2 was the only technology for foaming common PP successfully. And in this way foaming PP product was obtained with active surface, high bubble density, outstanding mechanical properties and low density of under 0.1g/cm3. Then the effect of saturation time, foaming temperature, saturation pressure and depressurization rate on the foam structure and volume expansion ratio were investigated. The likely best condition of saturation time, foaming temperature and saturation pressure was determined.
(3) Blending modification of PP and its foamability. The foamabilities of common PP and HMSPP were investigated firstly. The result showed that the likely foaming zone of HMSPP was wider than that of common PP. And the expansion ratio of HMSPP was also higher than that of common PP. So LDPE, HDPE were used to modified the property of PP. Then LDPE/PP, HDPE/PP blends were foamed and their MFR and melting point were investigated. Experimental results showed that the LDPE/PP,HDPE/PP blends had similar variation patterns in respect of MFR and melting point and cellular structure. For all blends, the MFR initially lowered and then heightened, the PP melting point initially heightened and then lowered. And all had better cellular structure then pure PP. At the PE content of 30%, the bubble density was the highest.
首先,对市售产品EPP珠粒进行表征分析。采用反光显微镜、扫描电子显微镜(SEM)、浸渍法、红外光谱仪(FT-IR)以及二甲苯抽提等方法对其泡孔形貌、密度、成分以及交联度等进行测定。结果表明,EPP珠粒为非交联闭孔泡沫材料,密度0.01~0.04g/cm3,发泡剂为惰性气体CO2。
其次,探索发泡工艺。三种发泡方法:直接挤出化学发泡法、两步化学发泡法、scCO2釜压法。利用扫描电子显微镜(SEM)、浸渍法对产品泡孔形貌、泡孔尺寸、泡孔密度以及材料密度、发泡倍率进行测定。结果表明,只有scCO2釜压法实现了普通PP的发泡,不添加任何添加剂,且材料外观规整,力学性能优异,泡孔密度高,发泡后材料最低密度达到0.1g/cm3以下,可控发泡倍率稳定在1~10倍,最高发泡倍率12~16倍,使用该方法对HMSPP进行发泡,最高发泡倍率可达31倍。并探讨了处理时间、温度、压力、卸压速度、冷却方式等因素对发泡倍率和泡孔结构的影响。确定了最佳发泡温度及其对应的压力为187~195℃、18.3~19.0MPa。
最后,对聚丙烯进行共混改性并探讨其改性后的发泡性能。采用单螺杆挤出机、开炼机、造粒机使用LDPE、HDPE对PP进行共混改性,改性后粒料通过RLS型熔体流动速率测定仪、DSC测试其熔体流动速率(MFR)、熔点;采用scCO2釜压法进行发泡实验,通过扫描电子显微镜(SEM)、浸渍法对产品泡孔形貌、泡孔尺寸、泡孔密度以及材料密度、发泡倍率进行测定。结果表明,随着LDPE、HDPE的加入,PP的MFR先降低后升高,熔点先升高后降低,在含量为30%时,MFR出现极小值、熔点出现极大值;泡孔密度更高,未出现泡孔合并、坍塌现象,说明加入PE树脂对PP进行共混改性可实现其发泡能力的优化。
Foamed polypropylene will be used widely in many fields such as packing and heat insulation material and so on, because of its outstanding mechanical properties, excellent thermal stability, well enduring environmental stress crack and good degradation performance. But the structural characteristic of polypropylene makes its foaming course hard to be controlled and this has affected the process of its large-scale industrialisation. This research is a preparative for the project of "Preparation of Expandable Polypropylene Particles " of XIN DA Co. Lit. of Heilongjiang province. The paper is divided into three parts.
(1) Characterization of EPP purchased from some foreign-funded enterprises. Reflective microscope, scanning electron microscopy (SEM), dipping method, FT-IR and extraction by dimethylbenzene were used for characterizing the cell morphologies、density、component and crosslinking degree. The results showed that the bubbles was closed, the density was between 0.01g/cm3 to 0.04g/cm3, and the particles were non-crosslinked which may be expanded by CO2. Basesed on the information we summed up the preparative methods of EPP: extrusion foaming processes and batch foaming process.
(2) The preparation technology of foamed polypropylene. Three methods were used for foaming: direct extrusion foaming processes with chemical foaming agent, two steps foaming processes with chemical foaming agent and batch foaming process with super critical carbon dioxide (scCO2). The cell morphologies were scanned by SEM, and densities were measured by dipping method. As a result, the batch foaming process with scCO2 was the only technology for foaming common PP successfully. And in this way foaming PP product was obtained with active surface, high bubble density, outstanding mechanical properties and low density of under 0.1g/cm3. Then the effect of saturation time, foaming temperature, saturation pressure and depressurization rate on the foam structure and volume expansion ratio were investigated. The likely best condition of saturation time, foaming temperature and saturation pressure was determined.
(3) Blending modification of PP and its foamability. The foamabilities of common PP and HMSPP were investigated firstly. The result showed that the likely foaming zone of HMSPP was wider than that of common PP. And the expansion ratio of HMSPP was also higher than that of common PP. So LDPE, HDPE were used to modified the property of PP. Then LDPE/PP, HDPE/PP blends were foamed and their MFR and melting point were investigated. Experimental results showed that the LDPE/PP,HDPE/PP blends had similar variation patterns in respect of MFR and melting point and cellular structure. For all blends, the MFR initially lowered and then heightened, the PP melting point initially heightened and then lowered. And all had better cellular structure then pure PP. At the PE content of 30%, the bubble density was the highest.
引文
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2陈佰全,戴文利,汤红霞.聚丙烯发泡材料的研究进展.塑料制造. 2006, 12:55~58
3刘本刚,张玉霞,王向东等.聚丙烯发泡材料的应用及研究进展.塑料制造. 2006, 8:82~86
4何继敏.交联挤出发泡聚丙烯的开发.塑料科技. 1999, 5:11~13
5李春艳,何继敏.提高发泡聚丙烯熔体强度的研究进展.工程塑料应用. 2008, 36(2):76~78
6张京珍.泡沫塑料成型加工.化学工业出版社. 2005.6:5~252
7王向东.不同聚丙烯发泡体系的挤出发泡行为研究.北京化工大学博士研究生论文. 2008:1~2
8 P. Nello. Polypropylene Handbook. 2nd Edition.胡友良等译.化学工业出版社. 2008.4:398~436
9何继敏.聚丙烯发泡材料的应用现状.工程塑料应用. 2002, 30(6):54~58
10 X. Zhe, G. Z. Wu and S. R. Huang. Preparation of Microcellular Cross-linked Polyethylene Foams by A Radiation and Supercritical Carbon Dioxide Approach. J. of Supercritical Fluids. 2008, 47(2):281~289
11 A. B. Lugaoa, H. Otaguroa and D. F. Parra. Review on the Production Process and Uses of Controlled Rheology Polypropylene—Gamma Radiation Versus Electron Beam Processing. Radiation Physics and Chemistry. 2007, 76(11-12):1688~1690
12 D. Graebling. Synthesis of Branched Polypropylene by A Reactive Extrusion Process. Macromolecules. 2002, 35(12):602~610
13 D. Auhl, J Stange and H. Munstedt. Long-chain-branched Polypropylenes by Electron Beam Irradiation and Their Rheological Properties. Macromolecules, 2004, 37(25):94652~9472
14 D. Saeed, B. Chul and P. M. Kortschot. Processing and Characterization of Microcellular Foamed High-Density Polyethylene/lsotactic Polypropylene Blends. Polymer Engineering and Science. 1998, 38(7):1205~1214
15 P. Rachtanapun, S. E. Selke and L. M. Matuana. Microcellular Foam of Polymer Blends of HDPE/PP and Their Composites with Wood Fiber. Journalof Applied Polymer Science. 2003, 88(12):2842~2850
16 P. Rachtanapun, S. E. Selke, L. M. Matuana. Effect of the High-Density Polyethylene Melt Index on the Microcellular Foaming of High-Density Polyethylene/Polypropylene Blends. Journal of Applied Polymer Science. 2004, 93(1):364~371
17张平,周南桥,黄目张等.不同聚丙烯材料共混的微孔发泡成型研究.塑料. 2007, 36(5):1~7
18 M. S. Susane, M. M. Laurent. Relationship Between Cell Morphology and Impact Strength of Microcellular Foamed High-density Polyethylene/Polypropylene Blends. Polymer Engineering and Science. 2004, 44(8):1551~1559
19 O. Rikuo, F. Takenori, T. Ryoichi, et al. A New Method for Producing High Melt Strength Poly(propylene) with a Reactive Extrusion. Macromol Mater Eng. 2005, 290(12):1227~1234
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