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材料知识 | 氟材料的发明史(~1940)

新材料参考2019-01-15 15:43:43
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The present review briefly describes the development of the fluoropolymer industry in the past 70 years. Discussed are industrial fluoropolymers including PTFE, PCTFE, PVDF,PVF, ETFE, ECTFE, FEP, PFA, THV, Teflon AF and Cytop. 

本文简要回顾了氟材料过去70年的发展,讨论了PTFE, PCTFE, PVDF,PVF, ETFE, ECTFE, FEP, PFA, THV, Teflon AF and Cytop(杜邦和旭硝子的无定型聚合物)这些氟材料的发明。

Nafion is included as a special functional fluoropolymer material. These industrial fluoropolymers are introduced in the order of their discovery or time of first production, included are their chemical structures, thermal properties, mechanical properties, electrical and electronic properties, optical properties, chemical resistance, oxidative stabilities, weather tabilities,processabilities and their general applications. The main manufacturing companies for the different types of fluoropolymer products are also mentioned. 

Nafion是一种含有很特种功能基团的氟聚合物材料。上述这些氟材料将按它们商业化的顺序来展开介绍。还包括他们的化学结构,热性能,机械性能,电子和电气性能,光学性能,耐化学性,氧化稳定性,耐候性,可加工性及他们的综合应用。也会提到生产这些氟材料的主要制造商。

1. Introduction (氟聚合物介绍)

Fluoropolymers are the polymer materials containing fluorine atoms in their chemical structures.From general organic polymer concepts, there are two types of fluoropolymer materials, i.e.perfluoropolymers and partially fluorinated polymers. In the former case, all the hydrogen atoms in the analogous hydrocarbon polymer structures were replaced by fluorine atoms. In the latter case, there are both hydrogen and fluorine atoms in the polymer structures. 

氟聚合物是指结构上含有氟原子的高分子材料。出于普通有机聚合物的概念,有两种氟聚合物,也就是全氟和含氟聚合物。类比碳氢聚合物,前者是指所有的H原子都被F原子取代,后者是指同时含有H和F原子。

The fluoropolymer industry discussed here is mainly concerned with the perfluoropolymers, although in some cases the partially fluorinated polymers are included. In the latter case, there are both hydrogen and fluorine atoms in the polymer structures, along with additional elements in selected cases, such as polyvinylidenefluoride (PVDF) and polychlorotrifluoroethylene (PCTFE). 

这里讨论的主要是全氟聚合物,也包括一些含氟聚合物的例子,有些例子还有其它元素,像PVDF就是含氟聚合物,PCTFE还含有氯原子。

2. The Development of the Fluoropolymer Industry from 1930s ~ 1990s 

2.  1930s ~ 1990s 氟聚合物的发展

1930s (1930年代)

The development of the fluoropolymer industry began with the discovery of the polytetrafluoroethylene (PTFE) by Dr. Plunkett at DuPont in 1938. The white powder found by accident opened the magic door to one of the most important applied chemistry areas—the fluoropolymer industry—which greatly influenced the whole world in the following 70 years.

氟聚合物工业的发展由杜邦Plunkett博士在1038年发现聚四氟乙烯(PTFE)开始。这种白色粉末是被偶然发现的,它的发展打开了一个最重要的应用领域的门-氟聚合物工业-影响了后面的70多年。

F叫兽特意找来Plunkett博士发现PTFE的照片和实验记录本


【F叫兽点评:1938年,RoyJ. Plunkett博士(图中打领带的老兄,博士地位很高呀,看来不用做实验光动动脑子就行,大热的天还半截袖子,头发锃亮,带手表的)在研究新型制冷剂的时候,在杜邦公司新泽西州的Jackson实验室中偶然发现了PTFE(此照片为多年后为纪念这一时刻而重新摆拍,还加了一个“回头哥”以示三人为证?)。他本来是把TFE当一种制冷剂来研究,弄在一个密封的罐子里,时间长了以后打开阀门发现没有气体出来而且重量不减,甚是好奇,于是锯开罐子发现了神秘“白粉”(老外的求实精神可嘉,要是F叫兽说不定直接扔了了事)】

博士变老了

这是当时的实验记录本

PTFE is a linear polymer of tetrafluoroethylene (TFE) . The preparation of PTFE is hazardous because of the chemical properties of TFE. Therefore, special production equipments and processing conditions are required. 

PTFE是四氟乙烯(TFE)的线性聚合物,由于TFE的化学特性造成制备PTFE是非常危险的。因此,需要特种的生产设备和处理条件。

The chemical structure of PTFE is similar to that of polyethylene (PE), except that the hydrogen atoms are completely replaced by fluorine. Unlike the planer zigzag chain confirmation of PE, PTFE has a helical chain confirmation due to the larger fluorine volume. The rigid helical polymer chains can crystallize very easily and result in a high crystallinity (up to 98%). Because of the compact crystalline structure and the dense fluorine atoms, PTFE is the heaviest polymer material with a density of 2.1 g/cm3. 

PTFE的化学结构类似PE,除了H原子完全被F原子取代掉。不像PE的之字形结构,由于F原子的体积大于H原子,PTFE聚合物分子是螺旋链状结构。其刚性的螺旋链结构很容易结晶化,导致PTFE拥有非常高的结晶度(达到98%)。由于紧密的螺旋结构和众多的F原子,PTFE是最重的聚合物材料,密度达到2.1 g/cm3. 

The rigid polymer chain structure also caused a high melting temperature (~320 °C) and a high melt viscosity for PTFE, which made it difficult to process PTFE with the traditional methods for polymer materials. For quite a long time after the discovery of PTFE, scientists kept working on the different approaches to process PTFE materials, and it can be processed into all kinds of shapes for almost every application area. 

刚性的PTFE分子结构还使得PTFE具有高熔点 (~320 °C)(状态不像可熔融塑料一样,应该是没有熔点)和高熔融粘度,这样造成PTFE不能用常规的方法加工。以至于发现PTFE很久以后,科学家们一直在研究PTFE不同的加工方法,现在它可以被加工成各种形状用于各种应用领域。

PTFE is available in granular, fine powder and water-based dispersion forms. The granular PTFE resin is produced by suspension polymerization in an aqueous medium with little or no dispersing agent. Granular PTFE resins are mainly used for molding (compression and isostatic) and ram extrusion. The fine PTFE powder is prepared by controlled emulsion polymerization, and the products are white, small sized particles. Fine PTFE powders can be processed into thin sections by paste extrusion or used as additives to increase wear resistance or frictional property of other materials.PTFE dispersions are prepared by the aqueous polymerization using more dispersing agent with agitation. Dispersions are used for coatings and film casting. 

PTFE可以是颗粒状、粉状和分散液的形式,PTFE粒料是悬浮法聚合聚合得到,由很少或不用分散剂,主要用于模压和挤出加工。PTFE分散料是通过乳液聚合得到,呈白色小颗粒状,主要通过糊状挤出制造薄片或者是用于其它塑料的添加剂以提高耐磨损和摩擦性。PTFE乳液(指浓缩液吧,估计作者没从事过氟化工,只是看看资料)是由乳液聚合得到,主要用于涂层和薄膜。

One of the most distinguishing properties of PTFE is its outstanding chemical resistance, except for some extreme conditions such as molten alkali metals or elemental fluorine. Basically, PTFE is not soluble in any organic solvents. PTFE exhibits high thermal stability without obvious degradation below 440 °C. PTFE materials can be continuously used below 260 °C. The combustion of PTFE can only continue in a nearly pure oxygen atmosphere, and it is widely used as an additive in other polymer materials as a flame suppressant. PTFE has an extremely low dielectric constant (2.0) due to the highly symmetric structure of the macromolecules. 

PTFE一个优异的性能就是其杰出的耐化学稳定性,除了极端条件下如融化的碱金属或元素氟,基本上PTFE是不被任何有机溶剂溶解。PTFE表现出极高的热稳定性,在440°C以上未见明显分解。PTFE可以在260°C以下连续使用,PTFE只有在纯氧中才会燃烧,可以用作一种塑料的阻燃剂添加剂(应该是指防滴剂)。PTFE由于其高对称分子结构具有极低的介电常数(2.0)。

The conventional PTFE has some limitations in its applications, such as poor weldability, low creep resistance, low radiation resistance, and high microvoid content. Therefore, research efforts were mainly trying to modify PTFE in different ways to overcome the shortcomings of the conventional PTFE. 

传统的PTFE由于其不可熔融性、低蠕性、低耐辐射性和高微孔率,使其应用受限。因此,人们努力开发了改性PTFE以克服传统PTFE这些缺点。

Modified PTFE significantly reduced melt viscosity by lowering the crystallinity through the incorporation of bulky comonomers into the polymer main chain. Modified PTFE has the advantages such as lower microvoid content and reduced permeation, better weldability and easier bonding treatment, better sealing properties, excellent electrical insulation properties, smoother surface finishes and higher gloss.

改性PTFE由于降低了结晶度,显著降低了熔融粘度,通过主链上共聚具有较大体积的侧基单体。拥有很多优点,如低微孔率,减少了渗透性。更好的熔融加工和粘接处理,更好的密封性,优异的电绝缘性和更高的表面光泽度。

Even after modification, PTFE materials still have low tensile strength, wear resistance and creep resistance compared to other engineering polymers. The properties of the PTFE products are strongly dependent on the processing procedure, such as polymer particle size, sintering temperature and processing pressure. Therefore, other fluoropolymers are still needed for some specific applications where PTFE is not completely suitable. 

即使改性后,PTFE相对其它工程塑料仍然有很低的表面张力,耐磨性和冷蠕性。PTFE产品的性能严重依赖加工过程,如聚合粒子的大小,烧结温度和加工压力等。因此,其它氟聚合物有更特殊的应用而PTFE可能不适合。

(待续)

===F叫兽点评===

F叫兽对作者把PTFE作为第一个发现的含氟材料持不同意见,其实PCTFE是第一个被发明的氟聚合物。在1934年,德国IG Farben公司的Fritz Schloffer and Otto Scherer发明。

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