資源目錄里展示的全都有，所見即所得。下載后全都有,請(qǐng)放心下載。原稿可自行編輯修改=【QQ：401339828 或11970985 有疑問可加】 The Solid State Shear Extrusion process optimization for cross-linked polymers 固態(tài)剪切擠出交聯(lián)聚合物的工藝優(yōu)化 The Solid State Shear Extrusion process optimization for cross-linked polymers Mahnaz Eskandari, Hamid Arastoopour and Jay D. Schieber September 30, 2005 Reducing the size of the solid material specially polymeric material is an important process in industry. Using small particle size provides a homo-geneous feed, near fluid-like handling characteristic, a desired temperature distribution among material during processing or molding, enhanced effective surface area and good mixing. In order to obtain polymer powders basically there are three technologies: ? Suspension or emulsion polymerization, ? Precipitation of powder from dilute polymer solutions, ? Mechanical grinding of solid polymers. . The first and the second technologies are used to obtain virgin powder polymers, although removing emulsifier and organic solvents from pro- duced polymers are costly and usually cannot entirely be removed (such as emulsifier). Mechanical grinding can be used for both virgin and waste poly-mers although the produced particles may not have exactly the same quality. Beside the flexibility of the mechanical grinding for pulverization of different polymeric material, the other advantage of the mechanical grinding is its high capacity and large scale operation capability. The fundamental idea in the mechanical size reduction technique is to subject the solid ma-terial to sufficient stresses such that material breaks into small pieces. In general, mechanical pulverization falls into these categories: crushing, im-pacting, cutting, and pulverizing at high compression and shear force. Based on our experimental data obtained by using screws with different CR, we may conclude that the degree of compression of the granulates in Zones 2 and 3 could be the most critical parameter of our process. There are two major effects of compression: one is the storage of large strain energy in the rubber granulates, and the other is the prohibition of slip at the rubber–metal interfaces and, in turn, the allowance of shear straining of the granulates as a result of the relative rotation of the screw with respect to the barrel wall. The combined high compressive shear results in more strain energy storage in the granulate. At a critical energy level, the granulate cannot be held together by any cohesive forces, and new surfaces form through the crack propagation and dissipation of the stored energy. Our previous study on the breakage of single rubber discs under high compression and tangential shear in a Bridgman Anvil apparatus supported such effects of the compression on the pulverization phenomenon. The idea of using high compression and shear force at the same time has been proposed by Bridgman, who established an apparatus with two disks that could apply hydrostatic pressure on metal sample between them and pulverize material. Enikolopian extended the idea of the high pressure and shear force to pulverize polymers by using extrusion process[8]. This process is a non-cryogenic pulverization process and it works in room temperature. Further a Bridgman anvil was used in Center of Excel-lence in Polymer Science and Engineering (CEPSE) at Illinois Institute of Technology (IIT) [6] to study the pulverization mechanism of the polymers. The search for finding the mechanism of the pulverization in the extrusion process for both linear and cross-linked polymers in CEPSE has been pursued till present. In this work, we applied Solid State Shear Extrusion (SSSE) process as a mechanical size reduction technique to waste low-cross-link-density natural rubber. The objective was to optimize the SSSE process and to determine the mechanism of the pulverization during the SSSE process, particularly for low-cross-link-density natural rubber. The Particle Size Distribution (PSD) of the produced particles, which was obtained from the process, was analyzed. The first goal of this analysis was to optimize the process condition to obtain a desirable output PSD (desired average particle size, or a narrow PSD); and the second goal was to find a relation between the process conditions and the output PSD. We showed that the produced particles in this pulverization process was reproducible and the variation coefficient of such powders was less than 3 percent. In order to satisfy the second goal, the produced PSD and torque were measured at different combinations of the temperature in heating zone along the screw length and rotating speed. Our results showed a non-monotonic behavior of both PSD and required torque with rotation speed (rpm) at different operating temperatures. Based on these results and the previous works on the SSSE process using polyethylene and polystyrene,it can be concluded that the pulverization mechanism depends on the mole-cular structure of the material, the distribution of the dispersed phase in matrix (in case of the filled polymer or blend polymers) and the nature of the interactions between the dispersed phase and the matrix. Since rubber was the matrix material that was subjected to the SSSE process, we focused on the structure of rubber, and its filler, Carbon Black (CB). We used two rubber samples with the same recipe but one with CB and the other one without CB. The difference between the average particle size of the sample with CB and without CB (around 30 percent) is an evidence for the effectof the second component on the produced particle size by the SSSE process. There are evidences that adding second polymer to the first polymer in the SSSE process changes the produced particle size same as adding filler. The magnitude of the change in the produced particle average size depends on the mechanical properties of the filler, the interaction between filler and polymer and the size distribution of the filler in polymer matrix. Pulverization also causes change in cross-link density of the polymer. Based on theses results it can be concluded that the smallest length scale, which undergoes through the breakage in the SSSE process is smaller than the size of the average distributed filler in the polymer matrix and it may be in molecular length scale, but because of high shear and compression forces and poor temperature control, the broken polymer chains react with each other rather than creating new surface and further they agglomerate. In order to examine this hypothesis, we have designed a new extended extruder, which provides high temperature control and shear force. The produced particle average size of our new extended extruder design supports our hypothesis. In principal, the SSSE process is a multi-length-scale process and capable of producing very fine particles. In order to achieve this capability, it is required to improve the process and one of the ways is modelling this process. A material model as a function of the temperature and deformation rate may be used to practice the process condition (the screw geometry, temperature change due to heating the barrel, bond breakage, and energy dissipation [5,8, 1], rotation rate, and particulate flow) and further to improve the process. Developing a material model based on the molecular approach can provide sufficient information for such a multi-length-scale model. Our parallel work has been establishing a Gaussian slip-link model for cross-linked polymers to satisfy this requirement. The pulverization of rubber granulates under high compressive shear was achieved using a single screw extruder without using a cryogenic fluid for cooling in the SSSE process. A higher degree of compression of the granulate and significant cooling of the pulverization zone were the most significant factors in the successful pulverization of the granulates. Agglomeration of the produced particles, especially the fine particles, was found to be competing with the pulverization process. The extent of agglomeration was observed to increase with a higher fraction of the fine particles, a greater degree of compaction, and a higher temperature of the pulverization zone. The rubber granulates that experience high compressive shear strain can develop tensile stresses and store significant strain energy leading to the formation of new surfaces through the crack opening mechanism （Mode I）.The granulates can fragment repeatedly until their size becomes so small that a high compressive strain and consequent high stresses can no longer be applied. Therefore, we conclude that there is a minimum size of the particles produced by the SSSE process, which is determined by the processing conditions and the design of the extruder. References [1] National materials advisory board publication, nmab-364, washington, d.c., national academy press. 1981. [2] Particle size analysis-evaluating laser differential diffraction systems in the light of iso 13320-1 - part 1. 2000. [3] K.K. Khait A.H. Lebovitz and J.M. Torkelson. Sub-micron dispersed- phase particle size in polymer blends: overcoming the taylor limit via solid-state shear pulverization. Polymer, 44(1):199–206, November 2003. [4] P.W. Bridgman. Effects of high shearing stress combined with high hydrostatic pressure. Physical review, 48:825–847, November 1935. [5] K. Khait D. Ahn and M.A. Petrich. Microstructure changes in ho- mopolymers and polymer blends induced by elastic strain pulverization. Journal of Applied Polymer Science”, 55:1431–1440, 1995. [6] H. Arastoopour D. Schocke and B. Bernstein. Pulverization of rubber under high compression and shear. Powder Technology, 102:207–214, 1999. [7] H. Arastoopour E. Bilgili and B. Bernstein. Pulverization of rubber granulates using the solid-state shear extrusion (ssse) process: Part i. process concepts and characteristics. Powder Technology, 115(3):265– 276, April 2001. [8] N.S. Enikolopian. Some aspects of chemistry and physics of plastic flow. Pure and Applied chemistry, 57(11):1707–1711, 1985. [9] K. Khait and S.H. Carr. Solid-State Shear Pulverization, A New Poly- mer Processing and Powder Technology. SPE, 2001. [10] K. Khait N. Furgiuele, A.H. Lebovitz and J.M. Torkelson. Efficient mixing of polymer blends of extreme viscosity ratio: elimination of phase inversion via solid state shear pulverization. Polymer Engineering and Science, 40(6):1447–1457, June 2000. [11] F. Teymour N. Shahidi and H. Arastoopour. Amphiphilic particulate phase semi-interpenetrating polymer networks based on recycled rubber matrix. Polymer, 45(15):5183–5190, Jul 2004. [12] S.A. Wolfson and V.G. Nikolskii. Powder extrusion: fundamentals and different applications. Polymer Engineering and Science, 37(8):1294– 1300, August 1997. 4 固態(tài)剪切擠出交聯(lián)聚合物的工藝優(yōu)化 Mahnaz Eskandari，哈米德Arastoopour和Jay D. Schie 二零零五年九月三十日 降低固體物料的大小是一個(gè)特別高分子材料的重要過程工業(yè)。利用小粒徑提供一個(gè)均勻擠出,接近流體態(tài)的特點(diǎn), 在所需材料的加工過程中或成型工藝，提高有效表面積和良好的混合 為了獲得聚合物粉末基本上有三種技術(shù): 懸浮液或乳液聚合; 從聚合物溶液稀釋沉淀粉末， 機(jī)械磨固態(tài)聚合物， 第一個(gè)和第二個(gè)技術(shù)是用于獲得原始粉末聚合物, 盡管從親和聚合物中消除乳化劑和有機(jī)溶劑是昂貴的,通常所無(wú)法完全被清除(例如乳化劑)。機(jī)械研磨是可用于新料和廢物產(chǎn)生粒子聚合物的研磨，雖然可能沒有完全相同的質(zhì)量。另外靈活的機(jī)械磨可粉化不同的高分子材料, 他的另一優(yōu)點(diǎn)是它的機(jī)械研磨，高容量的、大規(guī)模的操作能力。機(jī)械尺寸還原工藝的基本理念是給固體材料足夠的壓力把這種材料斷裂成小塊。一般來(lái)說,機(jī)械粉碎陷入這些類別：破碎,擠壓,切割,和高壓縮和剪切力的粉碎。 我們用不同CR螺桿所做實(shí)驗(yàn)得到的數(shù)據(jù)，我們可以讀出結(jié)論：區(qū)域2和3的擠出機(jī)的壓縮程度是固相剪切粉碎過程最重要的影響因素。壓縮有兩個(gè)重要的影響：第一：大量的剪切能的貯存；第二：阻止膠料在橡膠－金屬接觸面的滑動(dòng)。循環(huán)的，螺桿的旋轉(zhuǎn)和機(jī)筒相互作用產(chǎn)生了對(duì)膠料的剪切應(yīng)力。綜合作用產(chǎn)生的高壓縮剪切使更多的應(yīng)變能貯存于膠料中。當(dāng)它達(dá)到臨界狀態(tài)，膠料不能承受時(shí)。通過能量的是放和裂紋的延伸而產(chǎn)生新的表面。用布里奇曼壓砧對(duì)我們以前關(guān)于單個(gè)橡膠磁盤進(jìn)行的高壓縮、線性剪切破碎的研究證實(shí)了粉碎現(xiàn)象中的這種作用。這種利用高壓縮和剪切力在同一時(shí)間被布里奇曼提出，他用兩個(gè)磁盤建立了一種儀器，可以應(yīng)用金屬樣品之間的靜水壓力粉碎物料。Enikolopian拓展了利用高壓力和剪切力對(duì)聚合物擠出過程中利用粉碎的方法。這個(gè)過程是在室溫下工作，一個(gè)非低溫粉化的過程。在伊利諾理工學(xué)院(公歷)，比 Bridgman更早把鐵砧用在中心卓越的高分子科學(xué)與工程中研究聚合物粉碎機(jī)理。搜索尋找粉碎機(jī)理的基礎(chǔ)上，在注射成型工藝為線性和交聯(lián)聚合物在CEPSE被追趕直到現(xiàn)在。這種設(shè)備，采用固態(tài)剪切擠壓過程，機(jī)械尺寸還原工藝?yán)速M(fèi)交聯(lián)密度低的自然橡膠。目的是優(yōu)化固態(tài)剪切擠壓的過程,并在固態(tài)剪切擠壓過程確定粉碎作用,尤其是對(duì)交聯(lián)密度低的天然膠。通過對(duì)固態(tài)剪切擠壓過程獲取粒徑分布所產(chǎn)生粒子的進(jìn)行了分析。這個(gè)分析的首要目標(biāo)是優(yōu)化工藝條件來(lái)獲得一個(gè)理想的輸出功率譜(所需的平均粒徑,或一條狹窄的粒徑分布)， 第二個(gè)目標(biāo)是尋找一種工藝條件和粒徑分布輸出之間的關(guān)系。 我們發(fā)現(xiàn)，在這個(gè)粉碎產(chǎn)生的粒子過程是重復(fù)性好，這種粉末的變異系數(shù)為不到3％。為了滿足第二個(gè)目標(biāo)，所生產(chǎn)的粒徑分布和扭矩分別測(cè)定在不同組合中的溫度加熱區(qū)沿螺旋長(zhǎng)度和旋轉(zhuǎn)速度。我們的研究結(jié)果表明兩者的粒徑分布，所需的轉(zhuǎn)矩轉(zhuǎn)速（RPM）在不同的操作溫度。根據(jù)這些結(jié)果和在以往的作品固態(tài)剪切擠壓過程中使用聚乙烯和聚苯乙烯，可以得出結(jié)論，粉碎機(jī)制上取決于材料的分子結(jié)構(gòu)，在矩陣分布的分散相（在填充聚合物或聚合物混合的情況下）和的分散相與基體之間的相互作用的性質(zhì)。由于橡膠是基質(zhì)材料，在SSSE過程中，我們集中在橡膠結(jié)構(gòu)，其填料，炭黑（CB）我們使用相同的配方，但一個(gè)有炭黑，另外一個(gè)沒有炭黑兩個(gè)橡膠樣品。同CB樣本的平均粒徑和無(wú)CB（約30％）之間的區(qū)別，是為第二個(gè)組件上產(chǎn)生的粒子尺寸效應(yīng)的固態(tài)剪切擠壓過程的證據(jù)。證據(jù)是，添加第二個(gè)聚合物在固態(tài)剪切擠壓過程的變化，增加填料的聚合物，是為第二個(gè)組件上產(chǎn)生的粒子尺寸效應(yīng)的固態(tài)剪切擠壓過程中產(chǎn)生的證據(jù)粒徑相同。而在生產(chǎn)顆粒平均尺寸的變化幅度取決于填料的力學(xué)性能，填料和聚合物之間的相互作用并在聚合物基體的填料粒度分布。粉碎還導(dǎo)致交聯(lián)的聚合物密度的變化。根據(jù)論文的結(jié)果可以得出結(jié)論說，最小的尺度，它通過在固態(tài)剪切擠壓過程中破損經(jīng)過比平均分布在聚合物基體的大小和填充物小，也可能是在分子尺度，但由于高剪切和壓縮力差溫度控制，破碎聚合物鏈相互反應(yīng)，而不是創(chuàng)造新的表面和他們進(jìn)一步凝聚。為了檢驗(yàn)這一假設(shè)，我們?cè)O(shè)計(jì)了新的擴(kuò)展擠出機(jī)，可提供高的溫度控制和剪切力。我們所生產(chǎn)的顆粒擠出機(jī)設(shè)計(jì)新的擴(kuò)展支持我們的假設(shè)平均規(guī)模。原則上，固態(tài)剪切擠壓過程是一個(gè)多長(zhǎng)的規(guī)模和能力的過程生產(chǎn)極細(xì)的粒子。為了實(shí)現(xiàn)這種能力，這是需要改進(jìn)的過程和途徑之一是模擬這個(gè)過程。一個(gè)作為溫度和變形速率功能材料模型可能用來(lái)練習(xí)過程中條件（螺桿的幾何形狀，溫度 由于改變加熱桶，鍵斷裂，能源消耗[5，8，1]，旋轉(zhuǎn)速度和顆粒流），并進(jìn)一步提高的過程。開發(fā)材料模型為基礎(chǔ)的分子方法可以提供足夠的信息對(duì)于這樣的多長(zhǎng)度比例模型。我們的并行工作已建立交聯(lián)聚合物，以滿足這一要求高斯滑鏈路模型。 在在固態(tài)剪切擠壓過程中橡膠在高壓剪切下進(jìn)行粉碎可以通過單螺桿擠出機(jī)在無(wú)冷卻液冷卻的情況下實(shí)現(xiàn)。對(duì)橡膠顆粒的較高壓縮和對(duì)剪切區(qū)域的重點(diǎn)冷卻是橡膠粉碎能夠成功的最重要的因素。所生產(chǎn)橡膠顆粒的凝塊，特別是精細(xì)橡膠顆粒，與橡膠的粉碎過程是同步存在的。粉碎區(qū)域的較高溫度、較高程度的壓縮，精細(xì)顆粒的較高摩擦力都會(huì)使凝結(jié)現(xiàn)象明顯。 橡膠顆粒在高剪切應(yīng)力作用下會(huì)產(chǎn)生拉應(yīng)力并貯存應(yīng)變能，并通過“雪崩”使機(jī)理釋放能量產(chǎn)生新的表面。橡膠顆?？梢员谎h(huán)的破碎直到小到高的壓縮應(yīng)力和隨之發(fā)生的高應(yīng)變不能夠?qū)崿F(xiàn)。因此，我們得出結(jié)論：通過SSSE粉碎橡膠得到的顆粒有一個(gè)最小尺寸，這個(gè)尺寸由加工條件和擠出機(jī)的設(shè)計(jì)來(lái)決定。 參考文獻(xiàn) [1] National materials advisory board publication, nmab-364, washington, d.c., national academy press. 1981. [2] Particle size analysis-evaluating laser differential diffraction systems in the light of iso 13320-1 - part 1. 2000. [3] K.K. Khait A.H. Lebovitz and J.M. Torkelson. Sub-micron dispersed- phase particle size in polymer blends: overcoming the taylor limit via solid-state shear pulverization. Polymer, 44(1):199–206, November 2003. [4] P.W. Bridgman. Effects of high shearing stress combined with high hydrostatic pressure. Physical review, 48:825–847, November 1935. [5] K. Khait D. Ahn and M.A. Petrich. Microstructure changes in ho- mopolymers and polymer blends induced by elastic strain pulverization. Journal of Applied Polymer Science”, 55:1431–1440, 1995. [6] H. Arastoopour D. Schocke and B. Bernstein. Pulverization of rubber under high compression and shear. Powder Technology, 102:207–214, 1999. [7] H. Arastoopour E. Bilgili and B. Bernstein. Pulverization of rubber granulates using the solid-state shear extrusion (ssse) process: Part i. process concepts and characteristics. Powder Technology, 115(3):265– 276, April 2001. [8] N.S. Enikolopian. Some aspects of chemistry and physics of plastic flow.Pure and Applied chemistry, 57(11):1707–1711, 1985. [9] K. Khait and S.H. Carr. Solid-State Shear Pulverization, A New Poly- mer Processing and Powder Technology. SPE, 2001. [10] K. Khait N. Furgiuele, A.H. Lebovitz and J.M. Torkelson. Efficient mixing of polymer blends of extreme viscosity ratio: elimination of phase inversion via solid state shear pulverization. Polymer Engineering and Science, 40(6):1447–1457, June 2000. [11] F. Teymour N. Shahidi and H. Arastoopour. Amphiphilic particulate phase semi-interpenetrating polymer networks based on recycled rubber matrix. Polymer, 45(15):5183–5190, Jul 2004. [12] S.A. Wolfson and V.G. Nikolskii. Powder extrusion: fundamentals and different applications. Polymer Engineering and Science, 37(8):1294– 1300, August 1997.