聚烯烴/氫氧化鎂奈米複合材料之合成與應用

Synthesis and Application of Polyolefin/Mg(OH)2 nanocomposites

張明仁(Ming-Jen Chang)

指導教授 ： 江彰吉 ； 鄭懷明

中原大學/理學院/化學系/博士(2007年)

https://doi.org/10.6840/cycu200700485

摘要

氫氧化鎂屬添加型無機阻燃劑，具有高熱穩定性，良好抑煙性及無毒性等優點，是一種環境友好的綠色阻燃劑，並於近年來受到廣泛的研究。氫氧化鎂的缺點為通常需要添加很大量(＞60％)才能到有效的難燃結果，加上氫氧化鎂本身與高分子的相容性極差，因此導致阻燃材料的機械性質及光學性質急驟下降，因此本論文將針對改善其界面相容性及分散性進行一系列研究。
本論文主要分成兩個部份，(一)分別利用原子轉移自由基聚合法，硼烷化學自由基聚合法以及觸媒架附的方法進行氫氧化鎂奈米微粒的表面接枝聚合反應，(二)進一步將所合成的聚烯烴/氫氧化鎂奈米複合材料，利用溶液混掺的方式添加入工業級的聚烯烴中，觀察其性質變化。
首先，利用原子轉移自由基聚合法合成出氫氧化鎂奈米微粒接枝聚苯乙烯，及氫氧化鎂奈米微粒接枝聚甲基丙烯酸甲酯。結果得知使用含氮數較多的ligand以及極性較高的溶劑，可獲得較好得聚合活性。另外其分子量亦與聚合時間呈線性關係，証明了其活性可控制自由基聚合法的特性。接著進一步利用其活性鏈末端製備出氫氧化鎂奈米微粒接枝聚(苯乙烯-b-丙烯酸甲酯)共聚物。所得之段式接枝共聚物可作為界面調合劑，於混掺時可有效改善兩高分子間因極性差異所導致的相分離現象。
在硼烷化學的部份，利用化學改質的方法，將9-BBN架接於氫氧化鎂奈米微粒上，並在氧氣與丙烯酸甲酯單體的環境下，製備出氫氧化鎂奈米微粒接枝聚丙烯酸甲酯奈米複合材料，此方法表現出相當好的接枝效率，於不同的反應條件下，可控制所得高分子的分子量，其分子量亦與反應時間呈現一線性成長。
利用氫氧化鎂表面裸露的氫氧基，在助觸媒(MAO)存在的條件下可將有機茂金屬觸媒成功架附上氫氧化鎂奈米微粒的表面。根據CpTiCl3觸媒的特性，我們可成功製備出具立體特異性的氫氧化鎂/對排聚苯乙烯奈米複合材料，然而受到中止反應時鏈轉移反應的影響，合成的高分子鏈與氫氧化鎂奈米微粒表面並不以共價鍵鍵結。
氫氧化鎂奈米微粒經過高分子接枝改質過後，可有效改善其與高分子材料間的界面相容性，並提升奈米微粒在材料中的分散性。當添加原子轉移自由基合成法及硼烷化學所製備的改質微粒時，其材料展現出良好的透光性及熱穩定性，並在某些比例下有良好的韌性。而在添加由觸媒架附所製得的改質微粒時，由於受到高分子結晶性的影響，雖然粒子仍能均勻分散，但其材料透光度明顯下降，並呈現出較硬脆之特性。

關鍵字

原子轉移自由基聚合法 ； 氫氧化鎂 ； 奈米複合材料 ； 觸媒架附 ； 硼烷化學

並列摘要

Recently, environmental halogen free flame retardant, magnesium hydroxide [Mg(OH)2] has attracted people’s attention because of its smoke suppression property, nontoxic and good thermal stability. However, Mg(OH)2 usually require addition level up to 60wt% in order to achieve acceptable combustion resistance. In addition, Mg(OH)2 tends to aggregate due to its nature chemical property and show poor compatibility with polymer materials. As a consequence, these disadvantages lead to significant reduction in the mechanical properties and penetrability of flame-retardant polymeric composites. Thus, this study will aim to improve the compatibility and dispersity of Mg(OH)2 nanoparticles.
This investigation contains two parts, (1) the graft polymerization from Mg(OH)2 nanoparticle surface by three specific methods: atom transfer radical polymerization (ATRP), borane radical polymerization and metallocene supported catalysts. (2) The synthesized polymer grafted-Mg(OH)2 hybrids will be added into commercial polymer materials by solution blending to prepare polymer/Mg(OH)2 nanocomposites and discuss its properties.
At the first, using ATRP to synthesize Mg(OH)2-g-PS and Mg(OH)2-g-PMMA core-shell structure hybrids. The results indicated that grafted efficiency can be obtained in the CuCl/PMDETA system and adding a small polar solvent. In the meanwhile, the molecular weight of polystyrene can be increased linearly with reaction time, it demonstrate the “living”/controlled character. Additionally, the living chain ends can be employed to further synthesize Mg(OH)2-g-PS-b-PMMA copolymer hybrids. The microscopy results reveal the effectiveness of Mg(OH)2-g-PS-b-PMMA hybrids in the polymer blends by reducing the phase-separated phenomenon and increasing interfacial interaction between domains.
In the part of borane chemistry, 9-BBN compounds react with allyl bromide attached-Mg(OH)2 nanoparticle by hydroboration, and the polymerization will be occurred by injecting oxygen to prepare Mg(OH)2-g-PMMA core-shell structure hybrid. High polymerization efficiency was observed in this procedure and the molecular weight can be controlled in different experimental conditions. The polymer chains also grow up linearly correspond with the reaction time.
The third method is using metallocene supported catalyst to prepare Mg(OH)2/syndiotactic polystyrene hybrids. In the existence of MAO, metallocene catalyst CpTiCl3 compounds were supported on the Mg(OH)2 nanoparticle surface via reacting with exposed hydroxyl groups, and the polymerization carried out in succession. Significantly, according to the basic mechanism of chain termination reaction of metallocene, the bonding between inorganic and organic will present nor covalent bonds in Mg(OH)2/syndiotactic polystyrene hybrids.
Polymeric modified Mg(OH)2 nanoparticle can get well dispersion and compatibility when blending with commercial polymers. These nanocomposites exhibit good penetrability, thermal stability and special mechanical properties (Higher elongation at break) when Mg(OH)2-g-polymer particles which prepared by ATRP and borane chemistry were added as the filler. In the other hand, although Mg(OH)2/s-PS hybrids also dispersed well in the polymer materials, the poor penetrability and brittle property of nanocomposites were affected by crystalline syndiotactic polystyrene.

並列關鍵字

metallocene supported catalyst ； borane chemistry ； Mg(OH)2 ； ATRP ； nanocomposites

參考文獻

(2) J. Green, M. Lewin, E. M. Pearce, Flame retardant polymeric materials, Plenum Press, 1982, 3, 1.

(4) H. R. Buser, Environ. Sci. Technol., 1986, 20, 404.

(6) S. H. Chiu, W. K. Wang, J. Appl. Polym. Sci., 1998, 67, 989-995.

(9) H. Gui, X. H. Zhang, W. F. Dong, J. L. Qiao, Polymer, 2007, 48, 2537-2541.

(10) X. L. Chen, J. Yu, S. Y. Guo, J. Appl. Polym. Sci., 2007, 103, 1978-1984.