论文标题:高密度聚乙烯/炭黑复合导电PTC材料及制品的研制
Study on HDPE/CB PTC Conductive Composite and Appliance
论文作者 殷茜
论文导师 黄锐,论文学位 硕士,论文专业 材料加工工程
论文单位 四川大学,点击次数 34,论文页数 65页File Size2124k
2004-05-01论文免费下载 http://paper.dic123.com/lunwen_245072837/ 高密度聚乙烯;炭黑;导电复合材料;PTC效应;稳定性;电子束辐照;交联;加工工艺
high density polyethylene; carbon black; conductivity material;PTC efficient stability; electron beam irradiation; cross-linking;processing; condition
本工作研究开发了一种新型高分子PTC导电复合材料及其80℃发热等级自控温伴热带，目前已在北京协昌电缆厂和巩义强力塑料厂得到应用，并创效10万元。借助DSC、TEM、WAXS等多种试验手段对炭黑填充高密度聚乙烯复合体系的导电逾渗转变、PTC效应、发热特性、长期通电稳定性、加工性能进行了较为详细的研究，并对试验结果作了全面分析和较为深入的探讨。 1 研究了不同结晶度高聚物／炭黑复合导电PTC材料PTC特性，探讨了PTC效应的形成机理，提出了PTC效应产生与基体聚合物结晶行为相关的观点。 2 首次系统研究高分子导电PTC材料热性能数据(热变形温度、维卡软化温度、熔点)与PTC材料特征温度之间的关系。认为材料的四川大学硕士学位论文:高密度聚乙烯/炭黑复合导电材料及制品的研究热变形温度与自控温伴热带的工作发热温度接近，维卡软化温度与制品开关温度相当，并由此确立了以HDPE为基体材料来开发80℃发热等级自控温伴热带。 3研究了不同品种炭黑填充高密度聚乙烯复合体系的导电逾渗转变及PTC行为，考察了CB基本性质、含量对材料PTC效应、结晶行为的影响。首次发现炭黑粒子加入降低了HDPE的结晶度，并由此认为炭黑粒子在基体材料中的分散状况也是影响材料PTC特性的一个主要因素。 4研究了以接枝聚乙烯为基体，复合导电体系的PTC特性及稳定性。G一HDPE/CB复合导电体系的结晶度较HDPE/CB体系略有降低，但PTC特性差别不大。由此制得的自控温伴热带经过7200小时通电运行，其PTC强度、电阻率、发热温度及功率变化率均小于15%，可以看出接枝聚乙烯的加入明显提高了材料的稳定性。 5通过对HDPE/PvDF/CB复合导电体系PTc特性及稳定性的研究发现:随着聚偏氟乙烯加入量的提高，材料的逾渗阀值由18%降低到12%，炭黑添加量可以适当减少，NTC效应也减弱，材料稳定性得到明显提高，由此制得的自控温伴热带经过6000小时通电运行，发热温度稳定在85℃~95℃范围内，这在国内尚属首次报道。 6系统研究了电子束辐照交联工艺对复合导电体系稳定性的影响，认为电子束辐照交联是最有效、最简单提高材料稳定性，减弱NTC效应的手段。随着辐照剂量的提高材料的NTC效应明显减弱，PTC曲线反演性也提高。以380kGy剂量辐照的复合物及制品也表现出优良的电致发热稳定性，通电7200小时功率下降小于10%，具有一定的商业用途。 7通过对高密度聚乙烯/炭黑复合体系的挤出工艺研究发现:挤出成型过程中，加工温度、挤出速度及冷却方式的变化，对自控温伴热带的性能有明显影响。因此，在生产自控温伴热带时必须严格控制工艺条件。 8以HDPE/CB高分子导电PTC材料制备的80℃发热等级自控温伴四川大学硕士学位论文:高密度聚乙烯/炭黑复合导电材料及制品的研究热带性能与国外产品相当，而价格仅为进口产品的三分之一，具有很好的应用前景。目前，已同北京协昌电缆厂合作生产自控温伴热带约5000米，应用于消防器材防冻保温。 关键词:高密度聚乙烯炭黑导电复合材料PTC效应稳定性电子束辐照交联加工工艺
A new kind of PTC conductive composite and its appliance, self-regulating heating cables , which has been used by Beijing Xiechang Cable Factory, Qiangli Plastics Factory and gain 100000yuan,was studied and developed in this paper. By means of DSC, TEM, WAXS, the percolation transition, PTC effect, stability, processability of HDPE/CB composites were studied systematically.1 The electrical conductive PTC composites of various crystallity were studied and the mechanism of PTC effect was discussed. It is supposed that the PTC effect is relation to the crystalline behavior of matrix.2 The relations between the data of thermal behavior and characteristic temperature of self-regulating heating cables were first studied systematically. It is showed that heat deformation temperature is same as working temperature of cable; Vicat softening point is close to the switch temperature. Based on the observations, HDPE was choose to be the matrix of self-regulating heating cable.3 The percolation transition and PTC effect of various types CB filled HDPE composites were studied. The influences of property and fraction of CB on the PTC behavior and crystallity were studied. It is first founded that CB can induce the crystallity of HDPE. It is supposed that the PTC effect is relation to the disperse of CB particles.4 The PTC effect and stability of g-HDPE/CB were studied. It showed that PTC behavior was similar with HDPE/CB, but the crystallity of g-HDPE was lower than HDPE/CB. The PTC intensive, resistivity, heating temperature and power of the cable made from g-HDPE were changed lower than 15% for 7200 hours. The results showed that g-HDPE could improve the heating stability.5 The PTC effect and stability of HDPE/PVDF/CB were studied. It showed that: percolation threshold reduced from 18% to 12%, with the fraction of PVDF improve and PVDF could improve the heating stability and reduce NTC characteristic of composites. It was first reported that the heating temperature of the cable made from HDPE/PVDF/CB were 85 C ~95 C for 7200 hours in our country.6 The effect of radiation cross-linking on stability of HDPE/CB was studied systematically. The result showed that with increasing of irradiation dose, the PTC reproducibility was improved and the NTC characteristic was reduced. The radiation cross-linking is the best way to improve the stability and reduce NTC characteristic. The cable irradiated with 380kGy display excellent thermo electrical character and can be used.7 The influence of extrusion processing factors of HDPE/CB composite was systematically studied. The results showed that the performances of PTC self-regulating heating cable depend on the die temperature, screw speed and cooling methods. So it is important to control the processing conditions.8 The characteristic of the self-regulating heating cable we producedare similar with the foreign cable, but the price of our cable is the 1/3 of them. So it has a bright outlook. Now, 5000metres self-regulating heating cable has been produced for antifreezing fire application by Beijing Xiechang Cable factory.
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