發(fā)布時間：2018-06-24 17:29

  本文選題：TiB_2 + 成分設(shè)計��； 參考：《合肥工業(yè)大學》2015年碩士論文

【摘要】：聚合物基PTC復合材料是當今國內(nèi)外研究最為熱門的功能高分子材料之一,目前已廣泛應用于自控溫加熱系統(tǒng)、過流保護元件等領(lǐng)域。對于該類PTC材料的廣泛應用,除了應具有優(yōu)異的PTC特性外,還需解決PTC特性的不穩(wěn)定和高溫NTC效應等缺陷。本文采用熔融共混法制備具有明顯PTC效應的PE/TiB2-CB復合材料。對復合體系進行SEM形貌觀察、升溫電阻特性測試、多次熱循環(huán)電學穩(wěn)定性測試、熱分析等,研究組織成分、制備工藝等對復合材料PTC特性的影響,并對其PTC機理進行初步探索。實驗結(jié)果表明：TiB2顆粒與聚乙烯基體之間無化學鍵連接,所以兩者之間有明顯的界面層存在。選擇以7：3的HDPE、LDPE配比作為基體,加入24%TiB2和6%CB作為導電填料,且在其混合過程中經(jīng)多次攪拌、研磨和干燥處理。在壓力6MPa,溫度為160℃下壓制后于空氣中冷卻制得的復合材料結(jié)晶度為48.4%,室溫電阻率為0.65Ω·m, PTC強度高達5.1；影響試樣PTC特性的各因素的主次關(guān)系是：熱壓成型后冷卻方式熱壓溫度熱壓壓力。隨著熱壓壓力和溫度的升高,復合材料PTC特性呈現(xiàn)先上升再下將趨勢；合適的熱壓溫度和成型后冷卻方式可以提升復合材料的結(jié)晶度,且結(jié)晶度越高,PTC效應越明顯；120℃退火處理后復合材料峰值電阻率和PTC轉(zhuǎn)變溫度(Ts)都有所提高,lo σ-T曲線也變得更為陡峭,紅外光譜分析顯示體系結(jié)晶結(jié)構(gòu)也沒有被破壞；與未交聯(lián)試樣較差阻-溫穩(wěn)定性相比,交聯(lián)試樣多次熱循環(huán)的穩(wěn)定性較好,且高溫時NTC效應不明顯。復合材料的熔融溫度范圍和熔融峰溫度僅僅依賴于HDPE、LDPE基體的特性。導電填料在聚乙烯基體中是主要分布在基體結(jié)晶區(qū)與無定形區(qū)的界面處以及無定形區(qū)中,只有少量填料因熱工藝等因素而滯留在基體結(jié)晶區(qū)。復合材料的PTC效應的產(chǎn)生主要是由聚合物結(jié)晶區(qū)受熱膨脹、熔融破壞導電網(wǎng)絡所致,且基體結(jié)晶區(qū)熔融對復合材料PTC特性的貢獻要高于結(jié)晶區(qū)熱膨脹。
[Abstract]:Polymer-based PTC composite is one of the most popular functional polymer materials at home and abroad, and has been widely used in the field of self-controlled heating system, over-current protection elements and so on. For the wide application of this kind of PTC materials, it is necessary to solve the instability of PTC properties and the high temperature NTC effect in addition to the excellent PTC properties. In this paper, PE- / TiB2-CB composites with obvious PTC effect were prepared by melt blending method. The effects of microstructure and preparation technology on the PTC properties of composites were studied by SEM observation, temperature resistance test, multiple thermal cycle electrical stability test, thermal analysis and so on, and the PTC mechanism of the composites was preliminarily explored. The experimental results show that there is no chemical bond connection between TIB _ 2 particles and PE matrix, so there is an obvious interfacial layer between them. In this paper, 7:3 HDPE LDPE was used as matrix, and 24TiB2 and 6 were added as conductive fillers. During the mixing process, they were stirred, ground and dried many times. The crystallinity of the composite is 48.4%, the resistivity is 0.65 惟 m at room temperature, and the PTC strength is as high as 5.1, at 6MPa pressure, 160 鈩，

本文編號：2062378