材料知识 | 氟材料的发明史(~1940)

新材料参考2019-01-15 15:43:43

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. 


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. 


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). 


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.



【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)】



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. 


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. 


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. 


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. 


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.


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. 




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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