【作者】 周麒麟；

【导师】 吴驰飞；

【作者基本信息】 华东理工大学 ， 材料科学与工程， 2011， 博士

【摘要】 聚对苯二甲酸乙二醇酯(PET)具有良好的耐候性与光学透明性。可以应用于包装、薄膜、工程塑料等领域。聚对苯二甲酸乙二醇酯-1,4-环己烷二甲醇酯(PETG)作为共聚型PET的一个重要种类与均聚PET相比更不易结晶,因而具有更好的透明性,更适合于制备透明塑料制品。因此研究就PETG的结晶行为不仅在理论方面,对生产应用也是十分有意义的。并且PET对波长在280nm以上的紫外线与可见光几乎透明,因此为了提高PET薄膜的抗紫外能力,需要添加紫外线吸收剂。炭黑(CB)是一种重要的工业填料,最常用作橡胶的补强、涂料着色剂及导电填料。而对于炭黑作为光稳定剂的研究较少,因此本文主要研究了炭黑作为光稳定剂对聚合物透明性及光稳定性的作用。在聚合物的应用中,通过炭黑的改性来提高其分散性,使其粒径更小而不易发生团聚,从而使聚合物获得更好的性能。本实验中利用原位固相接枝的方法把有机紫外线吸收剂对炭黑进行接枝改性,制备得到了有机无机光稳定剂协同体系的接枝改性炭黑(m-CB),并将其应用到PET薄膜及板材中,考察了PET/m-CB复合材料的透明性、结晶行为及耐紫外老化性能。首先研究了普通均聚型PET与共聚型PETG的结晶性对PET薄膜的透明性的影响。结果表明,PET薄膜的结晶对薄膜雾度的影响非常大,结晶能力较弱的PETG更有利于制备透明的PET薄膜。同时,对不同类型的炭黑与苯并三唑类紫外线吸收剂(UV-P和UV327)对PET薄膜的透明性影响的研究发现,粒径小的色素炭黑Mogul-L对增强PET薄膜的紫外线吸收能力更有效,而且发现苯并三唑类紫外线吸收剂对保持PET薄膜的透明性与增强紫外线吸收能力有显著作用。对炭黑与有机紫外线吸收剂协同效应的研究发现,两者都能比较好地吻合朗伯比尔定律,并且两者的协同效应表现于两者吸光系数的相加。为了提高炭黑在PET基体中的分散性,以及增强炭黑与有机紫外线吸收剂的协同效应,使用UV-P和UV327对炭黑直接进行原位固相接枝改性。Haake流变仪与热失重(TGA)的研究结果发现,UV-P比UV327更易与炭黑进行原位接枝反应。通过红外光谱(FTIR)及能谱(EDS)对制备产物的分析表明,UV-P与炭黑的反应主要发生在UV-P的羟基和炭黑表面的含氧基团之间,UV327则因为分子结构较复杂,有一定的空间位阻效应使得其与炭黑的反应能力较弱。对制备得到的UV-PCB的粒径及分散性的研究发现,UV-PCB在PET基体中的分散性优于未改性的UV-P/CB体系,并且UV-PCB的分散粒径可以达到100 nm以下,即纳米材料所定义的范围。对PET/UV-PCB薄膜进行的透光率的研究发现,UV-PCB对紫外线的吸收能力远远高于炭黑与UV-P单独使用的情况,并且效果比普通共混体系的UV-P/CB效果更好。通过朗伯比尔定律的研究发现,UV-PCB的吸光系数要高于UV-P/CB,表明炭黑在经过改性之后具备了一定的纳米效应,其吸光系数不仅仅是两种光稳定剂吸光系数的普通相加而要更高。证明了UV-P接枝改性炭黑是一种有效的制备具有优异性能的紫外线吸收剂的方法。在研究了接枝改性体系的UV-PCB与普通共混体系的UV-P/CB对PETG的非等温结晶动力学的研究后发现,PETG在较高的降温速率下不易结晶,可以用Jeziorny方程与Ozawa方程对其非等温结晶动力学行为进行很好的描述。PETG的结晶生长属于异相成核的二维三维混合生长。而添加入炭黑之后,PETG的结晶速率加快,炭黑促进了PETG的异相成核的三维生长,并且在结晶后期有很明显的二次结晶行为。与普通体系的UV-P/CB相比,接枝改性体系的UV-PCB的成核能力更强,加快了PETG的结晶速率。对两者加入PETG之后的雾度的研究发现,PETG的雾度上升较纯PETG的变化并不显著,说明炭黑的加入使PETG的晶粒的减小在一定程度上也防止了其对光线的散射。对共聚型PET及添加不同光稳定剂之后进行了光降解动力学的研究发现,PET的弱链段受到的光降解的影响要远大于普通链段。UV-PCB对PET的保护主要表现在降低光降解常数与减少分子的弱连接数量,而且其效果要好于两者单独使用的情况。对PET的光降解产生的热学性能和力学性能的研究发现,PET的光降解对熔融温度、玻璃化温度及热变形温度的影响较小,而模量、冲击强度和拉升强度等力学性能有较明显的下降。添加了光稳定剂之后PET的力学性能的下降得到有效的抑制,尤其UV-PCB的表现更突出。证明了UV-PCB对紫外线的强烈吸收对PET的光稳定性有非常显著的提高。并且其对紫外线的吸收所产生的分子内部结构的互相转变长期有效,因此可以有效延长PET的使用寿命。更多还原

【Abstract】 Poly(ethylene terephthalate) (PET) is a material with good weatherability and optical transparency can be applied in packaging, film and engineering plastics. Compared with PET, Poly(ethylene terephthalate) glycol (PETG) is a copolymer of PET performing less crystallization and better optical transparency to be applied in transparent plastic products. Thus the research of the crystallization behavior of PETG is meaningful for not only theory study but also practical production. PET is transparency for UV light which wavelength is over 280 nm. Therefore UV absorber has to be added into PET to improver its UV resistance.Carbon black (CB) is an important additive acted as reinforcing agent, colorant and conductive filler. But there are few studies about its UV stabilization property. In this paper, UV stabilization property of polymer/CB composite is investigated. CB is usually modified to improve its dispersibility in polymers. This helps to decrease the aggregate size of CB and improve certain properties of polymers.CB was modified with a commercial UV absorber to prepare an organic and inorganic compound UV stabilizer through in-situ reaction in solid phase. Modified CB (m-CB) was added into PET films or plates and the crystallization behavior, transparency and UV resistance of PET/CB composites were discussed.Firstly, transparency influenced by the crystallization of homopolymerized PET (homo-PET) and PETG was investigated. It is proved that the haze of PET films is strongly influenced by the crystallizing ability. PETG whose crystallizating ability is lower performs better transparency than homo-PET. Different type of CB or benzotriazol UV absorbers (UV-P and UV327) was added into PET to improve its UV resistance. The results showed that pigment CB Mogul-L with small aggregate size is more efficient in enhancing UV resistance and bezotrazol UV absorbers can increase UV absorbance and keep high transparency of PET film. The research on the synergistic effect for the combination of organic UV absorber and in organic UV stabilizer CB showed that Beer-Lambert law is suitable to both organic UV absorber and CB in PET. The synergistic effect for bezotrazol UV absorber and CB behaves as the addition of their absorbence index.CB was modified with UV-P and UV327 to improves its dispersibility and the synergistic effect between them. Haake rheometer and thermogravimetric analysis (TGA) characterization showed the reaction between UV-P and CB was more obvious than between UV327 and CB. Fourier transform infrared (FTIR) and Energy Dispersive Spectrometry (EDS) characterizations showed that the chemical reaction happened between the oxygen-containing groups on the surface of UV-P and CB. But the strong steric hindrance of UV327 weakened the reaction between UV327 and CB. After the modification, the aggregate size of UV-PCB decreased to below 100 nm and the specific surface area increased.PET/UV-PCB composite films were prepared and exhibited higher UV absorbing ability than PET/CB, PET/UV-P systems and PET/UV-P/CB systems. The absorbance index of UV-PCB is larger than UV-P/CB indicated that UV-PCB obtained nano-effect.Both UV-PCB and UV-P/CB acted as good nuclear agent in PET. The non-isothermal kinetics of PETG/UV-P/CB and PETG/UV-PCB were investigated. The results showed that pure PETG can hardly crystallization under a relative high cooling rate and can be described by Jeziorny and Ozawa methods. The spherulite growth of PETG is between two dimension and three dimension through heterogeneous nucleation. After the addition of UV-P/CB or UV-PCB, the spherulite growth of PETG changed to three dimension and contained second step crystallization. The nucleating ability of UV-PCB is better than UV-P/CB because of the aggregate size decreasing and the surface area increasing of UV-PCB. The increase crystallizing ability of UV-PCB and UV-P/CB did not increase the haze of PETG very much.UV degradation kinetics of PET/CB composites were investigated. The results showed that the weak links in PET brake much more easily than normal links. The protection of UV-PCB for PET exhibited on the decreasing of the UV degradation rate constants and the fraction of weak links. The melt temperature, glass transition temperature and heat-deformation temperature were slightly influenced by UV radiation. But UV radiation caused the decreasing of storage modulus, impact strength and tensile strength for PET. PET with UV-PCB performs more stabilized than with CB or UV-P individually. UV-PCB in proved as an efficient UV stabilizer to improve the UV absorbing ability and stability of PET.更多还原