Microstructure and on-line shear viscosity of PP/nano-CaCO3 composites prepared by twin-screw extruder
Microstructure and on-line shear viscosity of PP/nano-CaCO3 composites prepared by twin-screw extruder
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DOI：
10.1007/s10853-006-0128-2
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发表时间：
2006-06
影响因子：
4.5
通讯作者：
Hanxiong Huang;G. Jiang;S. Mao
中科院分区：
文献类型：
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作者：
Hanxiong Huang;G. Jiang;S. Mao
接受日期：2006年2月6日/在线发布：2006年6月28日 Ó Springer Science+ Business Media, LLC 2006 纳米碳酸钙由内蒙古蒙西高新材料有限公司生产。该纳米碳酸钙由制造商预处理。使用硬脂酸作为偶联剂。 PP/纳米CaCO3复合材料采用模块化同向啮合双螺杆挤出机制备，螺杆直径为35 mm，长径比为40:1。螺杆元件的选择和排列可提供高剪切强度，有助于减少纳米CaCO3的聚集。更详细地，五个捏合块部分沿着螺杆与公共输送元件交替。第二捏合段内设有反向捏合块，以增加螺杆元件的填充度。两个中性捏合元件的加入延长了物料的停留时间，进一步提高了剪切强度。首先将纳米CaCO3在90℃的烘箱中干燥4小时，然后与偶联剂混合约10分钟，以促进纳米颗粒在PP基质中的分散。偶联剂的含量为纳米碳酸钙的1.5wt％。将PP和纳米CaCO3颗粒充分干混，然后送入双螺杆挤出机。从料斗到线料模头的配混在160-180-195-195-190-190-190-190-190℃的温度分布下进行。除非另有说明，螺杆速度设定为400rpm。 Haake ProFlow在线流变仪专为测量熔体粘度和流动指数而设计，安装在双螺杆挤出机的末端，在线测量纳米复合材料在混炼过程中的熔体剪切粘度。 ProFlow 系统不断地从双螺杆挤出机末端转移少量材料，并通过熔体泵将该材料推过毛细管。熔体泵前的压力由自动旁通阀控制，以避免测量过程中对过程的干扰。收集挤出的纳米复合材料（线），然后用于微观结构观察。在氮气环境中从纳米复合材料上切割出厚度约100 nm的超薄膜。然后通过在 100 kV 加速电压下操作的透射电子显微镜（TEM，Jeol JEM-100CX II）检查超薄膜，以观察纳米 CaCO3 颗粒的分散状态。通过使用Scion图像软件(Beta 4.02，Scion Corp.)分析TEM显微照片来定量确定纳米颗粒的尺寸分布。对每种纳米 CaCO3 含量至少分析了三张 TEM 显微照片。图 1 显示了分别含有 5、10 和 20 wt% 纳米 CaCO3 的纳米复合材料的 TEM 显微照片。可以看出，大多数纳米颗粒在 PP 基体中分散良好。结果表明，本工作中使用的螺杆设计有利于纳米颗粒的分散。随着纳米CaCO3含量的增加，颗粒尺寸变大，并且在CaCO3负载量为20wt%时出现一些大的聚集体。对TEM显微照片的定量分析表明，大多数纳米粒子的尺寸小于100 nm，最小的纳米粒子小于5 nm。随着纳米粒子的增加，粒子的尺寸变大。的比较
Accepted: 6 February 2006/Published online: 28 June 2006 Ó Springer Science+ Business Media, LLC 2006 nano-CaCO3 was manufactured by Inner Mongolia Mengxi High-Tech Materials Co. Ltd. This nano-CaCO3 was pretreated by the manufacturer. Stearic acid was used as coupling agent. The PP/nano-CaCO3 composites were prepared using a modular co-rotating, intermeshing twin-screw extruder with a screw diameter of 35 mm and a length-diameter-ratio of 40: 1. The screw elements were selected and arranged to provide high shear intensity and help decrease the aggregation of the nano-CaCO3. In more detail, five kneading block sections alternate with the common conveying elements along the screw. A reverse kneading block is set in the second kneading block section to increase the filled degree in the screw elements. The addition of two neutral kneading elements extends the residence time of materials and further increases the shear intensity. The nano-CaCO3 was first dried in an oven at 90 C for 4 h and then mixed with the coupling agent for about 10 min to facilitate the dispersion of the nanoparticles in the PP matrix. The content of the coupling agent was 1.5 wt% of the nano-CaCO3. The PP and the nano-CaCO3 particles were dry-mixed thoroughly before feeding into the twin-screw extruder. The compounding was carried out at temperature profiles of 160-180-195-195-190-190-190-190-190 C from the hopper to the strand die. The screw speed was set at 400 rpm unless otherwise noted. The Haake ProFlow on-line rheometer, which was designed for measuring the melt viscosity and flow index, was side-mounted at the end of the twin-screw extruder and the melt shear viscosity of nanocomposites was measured online during the compounding. The ProFlow system continuously diverted a small flow of material from the end of the twin-screw extruder and pushed that material through a capillary by means of a melt pump. The pressure before the melt pump was controlled by an automatic bypass valve to avoid the disturbance of the process during the measurement. The extruded nanocomposites (strands) were collected and then used for the microstructure observation. Ultra-thin films with about 100 nm in thickness were cut from the nanocomposites in a nitrogen environment. The ultra-thin films were then examined by transmission electron microscopy (TEM, Jeol JEM-100CX II) operated at an accelerating voltage of 100 kV to observe the dispersion state of nano-CaCO3 particles. The size distribution of nanoparticles was quantitatively determined by analyzing the TEM photomicrographs using Scion image software (Beta 4.02, Scion Corp.). At least three TEM photomicrographs were analyzed for each nano-CaCO3 content. Figure 1 shows the TEM photomicrographs of the nanocomposites containing 5, 10, and 20 wt% nano-CaCO3, respectively. As can be seen, most nanoparticles were dispersed well in the PP matrix. It is demonstrated that the screw design used in this work is good for the dispersion of the nanoparticles. With the increase of nano-CaCO3 content, the particle size becomes larger and some large aggregates occur at the CaCO3 loading of 20 wt%. The quantitative analysis on the TEM photomicrographs showed that the sizes of most nanoparticles are less than 100 nm and the smallest one is lower than 5 nm. With the increase of nanoparticles, the size of the particles becomes larger. The comparison of