高溫正溫度係數(PTC)奈米高分子複合材料之製備與研究

The Preparation and Investigation of High Temperature Positive Temperature Coefficient (PTC) Nano-Polymeric Composites

曹耕毓(Keng-Yu Tsao)

指導教授 ： 黃繼遠

大同大學/工程學院/材料工程學系所/博士(2011年)

摘要

本研究將碳黑添加至聚醯胺-12 (Nylon-12，N12)基材，以製備正溫度係數(PTC) 高分子基材元件。探討碳黑添加量、氬氣電漿處理時間、氬氣電漿處理瓦數、起始劑(DCP)化學交聯、聚醯胺-12 (Nylon-12，N12) 經接枝乙烯基三甲氧基矽烷(vinyltrimethoxysilane) (VTMS-g-N12)等因素之影響。本研究主要目標在提升PTC強度，及抑制負溫度係數(negative temperature coefficient, NTC)效應之影響。並以掃描式電子顯微鏡(SEM)、膠體含量(Gel fraction)、X光繞射儀(XRD)、示差熱分析儀(DSC)、熱重熱差分析儀(TGA)、動態機械(DMA)、熱機械分析儀(TMA)等，對複材之交聯結構進行分析與討論，再藉由再現性測試對複材之結構穩定性進行探討，並利用電阻溫度係數(αT )來探討導電複材對環境溫度變化之應答靈敏度，及其與PTC強度之相關性。而本研究結論如下。
第一部份顯示聚醯胺-12/碳黑(N12/CB)組成系列，發現碳黑含量(45.0 wt.%)為最適添加條件，其滲濾效應理論可由電阻驟降現象而被合理解釋。使用氬氣電漿處理之聚醯胺-12 (plasma treated nylon-12, PN12)可使複材之PTC強度增加，利用1,1-diphenyl-2-picryhydrazyl (DPPH) 自由基檢測方法，檢測經氬氣電漿處理之聚醯胺-12 (PN12)之自由基含量，發現氬氣電漿處理條件為 20W, 3min時，可保有最大自由基含量(8.1 × 10-6 mol / g )。
第二部份探討聚醯胺-12 (N12) 與不同劑量起始劑(DCP)，產生化學交聯反應，再與碳黑(N12/DCP/CB)組成之複合材料。發現聚醯胺-12/碳黑(45.0wt.%)/DCP(2.0phr) (N12C45D2.0)複合材料，具有較佳的PTC強度(4.38數量級)，且NTC效應可完全被抑制。當DCP添加含量從0.0phr至2.0phr時，其複材的交聯度提升至70.25%；複材之結晶度從19.3%提升至20.9%；其複材之熱氧化裂解溫度(T-10%)可從409.8 0C 提升至430.8 0C，大大提升整體複材之熱穩定性；其複材tanδ值之玻璃轉移溫度(Tg)從48.4 0C提升至49.5 0C。當複材組成為聚醯胺-12/碳黑(45.0 wt.%)/DCP(2.0phr) (N12C45D2.0)，也成功通過 200 0C 熱處理，並循環測試10次，發現有良好之回覆性，使PTC元件具高度可靠性，且具極佳結構穩定性。另外，對於複材的電阻-溫度曲線特性來探討，當DCP含量添加至0.5phr時，其複材的開關溫度(Ts)可從114.8 0C提升至158.3 0C；其複材之電阻溫度係數(αT)值可從0.051提升至0.691。代表複材的電阻-溫度曲線特性的好壞，其重要參數是電阻溫度係數(αT)，此數值可反映出複材的電阻-溫度曲線的陡峭程度(斜率)。當此數值(αT)越大時，其導電複材對溫度變化的應答就越靈敏，即代表PTC強度越顯著，其相應的導電複材的性能也就越好。
第三部份探討矽烷(vinyltrimethoxysilane, VTMS)接枝含量對聚醯胺-12與碳黑組成複材(VTMS-g-N12/CB)之交聯影響。發現在矽烷接枝含量為(0.3wt.%)之聚醯胺-12/碳黑(45.0wt.%)(VTMS-g-N12(0.3)C45)複材，其PTC強度即可明顯地提升至5.11個數量級，且NTC效應即可完全被改善且抑制。隨VTMS-g-N12含量從0.0 wt.%至2.0wt.%時，其複材之交聯度提升至65.12%；複材之結晶度從19.3 %提升 20.5 % 。另一方面，其複材之熱氧化裂解溫度(T-10%)可從 409.8 0C 提升至440.6 0C，大大提升整體複材之熱穩定性；其複材tanδ值之玻璃轉移溫度(Tg) 從48.4 0C 提升至 57.8 0C。當複材組成為矽烷接枝含量為(0.3wt.%)聚醯胺-12/碳黑(45.0 wt.%)(VTMS-g-N12(0.3)C45)，也成功通過 200 0C 熱處理，並循環測試10次，仍有良好之回覆性，使PTC元件具高度可靠性，且具極佳結構穩定性。另一方面，對於複材的電阻-溫度曲線特性來探討，當VTMS-g-N12含量從0.0 wt.%至0.3 wt.%時，其複材的開關溫度(Ts) 可從114.8 0C提升至145.9 0C；其複材之電阻溫度係數(αT)值可從0.051提升至0.783。代表複材的電阻-溫度曲線特性的好壞，其重要參數是電阻溫度係數(αT)，此數值可反映出複材的電阻-溫度曲線的陡峭程度(斜率)。當此數值(αT)越大時，其導電複材對溫度變化的應答就越靈敏，即代表PTC強度越顯著，其相應的導電複材的性能也就越好。
另一方面，利用熱機械分析儀(TMA)來探討矽烷接枝反應與水交聯之聚醯胺-12與碳黑(VTMS-g-N12/CB)複合材料的熱膨脹係數(CTE)性質之影響。結果得知，該導電複合材料的應答溫度之R-T曲線(PTC效應)與熱膨脹係數(CTE)之間非常密切。

關鍵字

再現性 ； 接枝反應 ； 起始劑 ； 矽烷 ； 電漿處理 ； 交聯 ； 碳黑 ； 聚醯胺-12 ； 負溫度係數(NTC) ； 正溫度係數(PTC) ； 高溫 ； 轉變溫度係數

並列摘要

In this investigation, carbon black was added into polyamide-12 (Nylon-12, N12) to produce a high temperature positive temperature coefficient (PTC) composite. The effect of carbon black content, plasma treatment time, power of plasma treatment, initiator (dicumyl peroxide, DCP) concentration, and vinyltrimethoxysilane (VTMS) content on the PTC intensity of water-crosslinked VTMS/N12 (VTMS-g-N12) composites. The main goal of enhancing PTC intensity, and the suppression of negative temperature coefficient (negative temperature coefficient, NTC) effect were investigated.
The cross-linking structure of composite was analyzed by using scanning electron microscopy (SEM), gel content, x-ray diffractometer (XRD), differential scanning calorimetry (DSC), thermogravimetric analyzer (TGA), dynamic mechanical analysis (DMA), and thermal mechanical analysis (TMA). The structural stability of composite was analyzed by reproducibility. The conclusions were listed as follows.
In the frist part, the 45.0 wt.% of carbon black was added into N12 to from N12/CB composites. The PTC intensity of composites was increased by using Ar-plasma to treat N12 (PN12). The 1,1-diphenyl-2-picryhydrazyl (DPPH) method was used to evaluate the free radicals content on the surface of PN12. In this investigation, the maximum free radicals content of PN12 was 8.1 × 10-6 mol g-1 as the N12 was treated by plasma at 20 W for 3 min.
In the second part, the N12 was chemically cross-linked with various amounts of initiator, DCP, in the N12/DCP/CB composites. In this part, the nylon-12/CB(45.0 wt.%)/DCP(2.0phr) (N12C45D2.0) composite possessed the best PTC intensity (4.38 orders of magnitude) of all composites and the NTC effect of composite was eliminated completely. The gel content of composite up to 70.25 %, the crystallinity (Xc) of composites increased from 19.3 % to 20.9 %, and the thermal stability (T-10%) increased from 409.8 0C to 430.8 0C, and the glass transition temperature (Tg) of tan δ of composites increased from 48.4 0C to 49.5 0C as the DCP contents up from 0.0phr to 2.0 phr. The N12C45D2.0 composite also possessed good reproducibility and good structural stability. In addition, the resistivity-temperature (R-T) curve characteristics of the N12/DCP/CB composite are further explored. As DCP content up from 0.0phr to 0.5phr, the switch temperature (Ts) of composites increased from 114.8 0C to 158.1 0C and the transitional temperature coefficient (αT) value increased from 0.051 to 0.691. It indicated that the transfer function of composite was good or bad as the composites proceed R-T measurement. In the R-T measurement, important parameter is temperature coefficient of resistivity (αT), and it is reflected the R-T curve steepness (slope). When this value (αT) larger, the conductive composite response to temperature change the more sensitive, the PTC intensity is more significant strong, the corresponding performance of the PTC thermistor is better.
In the third part, the 45.0 wt.% of carbon black was added into VTMS-g-N12 to from conductive composite. The PTC intensity of this composite was obviously and the PTC intensity was 5.11 orders of magnitude of composites. The NTC effect of composite also eliminated completely as 0.3 wt.% of VTMS was added. The gel content of composite up to 65.12 %, and the crystallinity (Xc) of composites increased from 19.3 % upto 20.5 %. On the other hand, the thermal stability (T-10%) of composite up to 440.6℃, and the glass transition temperature (Tg) of tan δ of composites increased from 48.4 0C to 57.8 0C by increasing the VTMS contents from 0.0 wt.% to 2.0 wt.%. The nylon-12 grafted with vinyltrimethoxysilane (0.3wt.%)/CB(45.0wt.%) (VTMS-g-N12(0.3)C45) composite possessed good reproducibility and good structural stability. Furthermore, the R-T curve characteristics of VTMS-g-N12(0.3)C45 was also explored. As the VTMS (0.0 ~ 0.3 wt.%) was added into the composites, the switch temperature (Ts) of composites could be raised from 114.8 0C to 145.90C; the transitional temperature coefficient (αT) value could be increased from 0.051 to 0.783.
In this investigation, the coefficient of thermal expansion (CTE) was studied by thermal mechanical analysis (TMA) measurement. It was found that the response temperature of thermal mechanical analysis (TMA) matched well with the PTC responsive temperature.

並列關鍵字

Transition Temperature Coefficient. ； Initiator ； Plasma treatment ； Cross-linking ； Carbon black (CB) ； Polyamide-12 (Nylon-12) ； Negative Temperature Coefficient (NTC) ； Positive Temperature Coefficient (PTC) ； High Temperature ； Silane ； Grafting Reaction

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