P84 NT2_ PI P84 NT2 赢创德固赛 Evonik Industries AG

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聚酰亚胺(有时缩写为PI)是一种含有酰亚胺基团的聚合物,属于高性能塑料类。聚酰亚胺具有高耐热性,在高温燃料电池、显示器和各种军事用途等需要坚固耐用的有机材料的用途中享有广泛的应用。经典的聚酰亚胺是Kapton,它由均苯四甲酸二酐和4,4'-氧二苯胺缩合而成。


历史
第一个聚酰亚胺是由Bogart和Renshaw于1908年发现的。 他们发现 4-氨基邻苯二甲酸酐在加热时不会熔化,但在形成高分子量聚酰亚胺时会释放水。第一个半脂肪族聚酰亚胺是由爱德华和罗宾逊通过二胺和四酸或二胺和二酸/二酯的熔融熔融制备的。

然而,第一个具有重要商业意义的聚酰亚胺 - Kapton - 是在 1950 年代由杜邦的工人开创的,他们开发了一种成功的合成路线,用于合成涉及可溶性聚合物前体的高分子量聚酰亚胺。直到今天,这条路线仍然是生产大多数聚酰亚胺的主要路线。聚酰亚胺自1955年开始批量生产。聚酰亚胺领域被各种广泛的书籍和评论文章所涵盖。

分类
根据其主链的组成,聚酰亚胺可以是:

脂肪族,
半芳香族(也称为脂肪族),
芳香族:这些聚酰亚胺是最常用的聚酰亚胺,因为它们具有热稳定性。
根据主链之间相互作用的类型,聚酰亚胺可以是:

热塑性塑料:通常称为假热塑性塑料。
热固性:以未固化树脂、聚酰亚胺溶液、型材、薄板、层压板和机加工零件的形式在市场上提供。
合成
制备聚酰亚胺的方法有几种,其中包括:

二酸酐和二胺之间的反应(最常用的方法)。
二酐与二异氰酸酯之间的反应。
二胺和二酐的聚合可以通过先制备聚酰胺羧酸的两步法进行,也可以直接通过一步法制备。两步法是聚酰亚胺合成中使用最广泛的方法。首先制备可溶性聚酰胺羧酸(2),在第二步中进一步加工成聚酰亚胺(3)后将其环化。两步法是必要的,因为最终的聚酰亚胺由于其芳香族结构,在大多数情况下是不可溶和不溶的。


用作这些材料前体的二酐包括均苯四甲酸二酐、苯醌四羧酸二酐和萘四羧酸二酐。常见的二胺结构单元包括4,4'-二氨基二苯醚(DAPE)、间苯二胺(MDA)和3,3'-二氨基二苯甲烷。[1] 已经研究了数百种二胺和二酐,以调整这些材料的物理性能,尤其是加工性能。这些材料往往是不溶的,并且具有很高的软化温度,这是由平面亚基之间的电荷转移相互作用引起的。[9]

分析

亚胺化反应可以通过红外光谱法进行跟踪。在反应过程中,聚酰胺酸在3400至2700 cm?1(OH拉伸)、~1720和1660(酰胺C=O)和~1535 cm?1(C-N拉伸)处的吸收带消失。同时,在~1780(C=O不对称)、~1720(C=O对称)、~1360(C-N拉伸)和~1160和745 cm?1(酰亚胺环形变)处,可以观察到特征酰亚胺带的出现。[10] 已经报道了聚酰亚胺[11]和碳化聚酰亚胺[12]和石墨化聚酰亚胺[13]的详细分析。

属性
热固性聚酰亚胺以热稳定性、良好的耐化学性、优异的机械性能和特有的橙色/黄色而闻名。聚酰亚胺与石墨或玻璃纤维增强材料复合,其弯曲强度高达 340 MPa (49,000 psi),弯曲模量为 21,000 MPa (3,000,000 psi)。热固性聚合物基体聚酰亚胺具有非常低的蠕变和高拉伸强度。在高达 232 °C (450 °F) 的温度和高达 704 °C (1,299 °F) 的短途偏移中,这些特性得以保持。[14] 模压聚酰亚胺零件和层压板具有非常好的耐热性。此类部件和层压板的正常工作温度范围从低温到超过 260 °C (500 °F)。聚酰亚胺还具有固有的阻燃性,通常不需要与阻燃剂混合。大多数具有 VTM-0 的 UL 等级。聚酰亚胺层压板在 249 °C (480 °F) 下的弯曲强度半衰期为 400 小时。

典型的聚酰亚胺部件不受常用溶剂和油的影响,包括碳氢化合物、酯类、醚类、醇类和氟利昂。它们还可以抵抗弱酸,但不建议在含有碱或无机酸的环境中使用。一些聚酰亚胺,如CP1和CORIN XLS,是溶剂可溶性的,并具有很高的光学透明度。溶解性使其适用于喷涂和低温固化应用。

应用
绝缘和钝化膜
聚酰亚胺材料重量轻、柔韧、耐热、耐化学腐蚀。因此,它们在电子工业中被用于柔性电缆和漆包线上的绝缘膜。例如,在笔记本电脑中,连接主逻辑板和显示器的电缆(每次打开或关闭笔记本电脑时都必须弯曲)通常是带有铜导体的聚酰亚胺底座。聚酰亚胺薄膜的例子包括 Apical、Kapton、UPILEX、VTEC PI、Norton TH 和 Kaptrex。

聚氧二苯甲酰亚胺的结构,“Kapton”。
聚酰亚胺用于涂覆用于医疗或高温应用的光纤。

聚酰亚胺树脂的另一个用途是作为绝缘和钝化层[16],用于制造集成电路和MEMS芯片。聚酰亚胺层具有良好的机械伸长率和拉伸强度,这也有助于聚酰亚胺层之间或聚酰亚胺层与沉积金属层之间的粘接。金膜和聚酰亚胺膜之间的相互作用最小,加上聚酰亚胺膜的高温稳定性,使得系统在承受各种类型的环境应力时都能提供可靠的绝缘。聚酰亚胺也被用作手机天线的基板。

航天器上使用的多层绝缘材料通常由涂有薄层铝、银、金或锗的聚酰亚胺制成。在航天器外部经常看到的金色材料实际上是单镀铝聚酰亚胺,单层铝朝内。黄褐色聚酰亚胺使表面呈现出类似金色的颜色。

机械零件
聚酰亚胺粉末可用于通过烧结技术(热压缩成型、直接成型和等静压)生产零件和形状。由于它们即使在高温下也具有很高的机械稳定性,因此在苛刻的应用中用作衬套、轴承、套筒或结构部件。为了改善摩擦学性能,通常使用石墨、PTFE 或硫化钼等固体润滑剂的化合物。聚酰亚胺零件和形状包括 P84 NT、VTEC PI、Meldin、Vespel 和 Plavis。

过滤器
在燃煤电厂、垃圾焚烧炉或水泥厂中,聚酰亚胺纤维用于过滤热气。在这种应用中,聚酰亚胺针刺毡将灰尘和颗粒物从废气中分离出来。

聚酰亚胺也是用于净化水的反渗透膜或浓缩水中稀释材料的最常见材料,例如枫糖浆生产。

柔性电路
主条目:柔性电子
聚酰亚胺用作柔性电路板和扁平柔性电缆的芯材。柔性电路板很薄,可以放置在异形电子产品中。

其他
聚酰亚胺用于医用管材,例如血管导管,因为它具有耐爆破压力性以及柔韧性和耐化学性。
半导体行业使用聚酰亚胺作为高温胶粘剂;它也用作机械应力缓冲器。
一些聚酰亚胺可以像光刻胶一样使用;市场上既有“正极”型,也有“负极”类型的光刻胶类聚酰亚胺。
IKAROS太阳能帆船航天器使用聚酰亚胺树脂帆,无需火箭发动机即可运行。




General chemical structure of a polyimide
Polyimide (sometimes abbreviated PI) is a polymer containing imide groups belonging to the class of high-performance plastics. With their high heat-resistance, polyimides enjoy diverse applications in roles demanding rugged organic materials, such as high temperature fuel cells, displays, and various military roles. A classic polyimide is Kapton, which is produced by condensation of pyromellitic dianhydride and 4,4'-oxydianiline.[1]

History
The first polyimide was discovered in 1908 by Bogart and Renshaw.[2] They found that 4-amino phthalic anhydride does not melt when heated but does release water upon the formation of a high molecular weight polyimide. The first semialiphatic polyimide was prepared by Edward and Robinson by melt fusion of diamines and tetra acids or diamines and diacids/diester.[3]

However, the first polyimide of significant commercial importance - Kapton - was pioneered in the 1950s by workers at Dupont who developed a successful route for synthesis of high molecular weight polyimide involving a soluble polymer precursor. Up to today this route continues being the primary route for the production of most polyimides. Polyimides have been in mass production since 1955. The field of polyimides is covered by various extensive books[4][5][6] and review articles.[7][8]

Classification
According to the composition of their main chain, polyimides can be:

Aliphatic,
Semi-aromatic (also referred to as alipharomatic),
Aromatic: these are the most used polyimides because of their thermostability.
According to the type of interactions between the main chains, polyimides can be:

Thermoplastic: very often called pseudothermoplastic.
Thermosetting: commercially available as uncured resins, polyimide solutions, stock shapes, thin sheets, laminates and machined parts.
Synthesis
Several methods are possible to prepare polyimides, among them:

The reaction between a dianhydride and a diamine (the most used method).
The reaction between a dianhydride and a diisocyanate.
The polymerization of a diamine and a dianhydride can be carried out by a two-step method in which a poly(amidocarboxylic acid) is prepared first, or directly by a one-step method. The two-step method is the most widely used procedure for polyimide synthesis. First a soluble poly(amidocarboxylic acid) (2) is prepared which is cyclized after further processing in a second step to the polyimide (3). A two-step process is necessary because the final polyimides are in most cases infusible and insoluble due to their aromatic structure.


Dianhydrides used as precursors to these materials include pyromellitic dianhydride, benzoquinonetetracarboxylic dianhydride and naphthalene tetracarboxylic dianhydride. Common diamine building blocks include 4,4'-diaminodiphenyl ether (DAPE), meta-phenylenediamine (MDA) and 3,3'-diaminodiphenylmethane.[1] Hundreds of diamines and dianhydrides have been examined to tune the physical and especially the processing properties of these materials. These materials tend to be insoluble and have high softening temperatures, arising from charge-transfer interactions between the planar subunits.[9]

Analysis
The imidization reaction can be followed via IR spectroscopy. The IR spectrum is characterized during the reaction by the disappearance of absorption bands of the poly(amic acid) at 3400 to 2700 cm?1 (OH stretch), ~1720 and 1660 (amide C=O) and ~1535 cm?1 (C-N stretch). At the same time, the appearance of the characteristic imide bands can be observed, at ~1780 (C=O asymm), ~1720 (C=O symm), ~1360 (C-N stretch) and ~1160 and 745 cm?1 (imide ring deformation).[10]? Detailed analyses of polyimide[11] and carbonized polyimide[12] and graphitized polyimide[13] have been reported.

Properties
Thermosetting polyimides are known for thermal stability, good chemical resistance, excellent mechanical properties, and characteristic orange/yellow color. Polyimides compounded with graphite or glass fiber reinforcements have flexural strengths of up to 340 MPa (49,000 psi) and flexural moduli of 21,000 MPa (3,000,000 psi). Thermoset polymer matrix polyimides exhibit very low creep and high tensile strength. These properties are maintained during continuous use to temperatures of up to 232 °C (450 °F) and for short excursions, as high as 704 °C (1,299 °F).[14] Molded polyimide parts and laminates have very good heat resistance. Normal operating temperatures for such parts and laminates range from cryogenic to those exceeding 260 °C (500 °F). Polyimides are also inherently resistant to flame combustion and do not usually need to be mixed with flame retardants. Most carry a UL rating of VTM-0. Polyimide laminates have a flexural strength half life at 249 °C (480 °F) of 400 hours.

Typical polyimide parts are not affected by commonly used solvents and oils – including hydrocarbons, esters, ethers, alcohols and freons. They also resist weak acids but are not recommended for use in environments that contain alkalis or inorganic acids. Some polyimides, such as CP1 and CORIN XLS, are solvent-soluble and exhibit high optical clarity. The solubility properties lend them towards spray and low temperature cure applications.

Applications

Thermally conductive pads made of Kapton foil, thickness approx. 0.05 mm

Roll of Kapton adhesive tape
Insulation and passivation films
Polyimide materials are lightweight, flexible, resistant to heat and chemicals. Therefore, they are used in the electronics industry for flexible cables and as an insulating film on magnet wire. For example, in a laptop computer, the cable that connects the main logic board to the display (which must flex every time the laptop is opened or closed) is often a polyimide base with copper conductors. Examples of polyimide films include Apical, Kapton, UPILEX, VTEC PI, Norton TH and Kaptrex.


Structure of poly-oxydiphenylene-pyromellitimide, "Kapton".
Polyimide is used to coat optical fibers for medical or high temperature applications.[15]

An additional use of polyimide resin is as an insulating and passivation[16] layer in the manufacture of Integrated circuits and MEMS chips. The polyimide layers have good mechanical elongation and tensile strength, which also helps the adhesion between the polyimide layers or between polyimide layer and deposited metal layer. The minimum interaction between the gold film and the polyimide film, coupled with high temperature stability of the polyimide film, results in a system that provides reliable insulation when subjected to various types of environmental stresses.[17][18] Polyimide is also used as a substrate for cellphone antennas.[19]

Multi-layer insulation used on spacecraft is usually made of polyimide coated with thin layers of aluminum, silver, gold, or germanium. The gold-colored material often seen on the outside of spacecraft is typically actually single aluminized polyimide, with the single layer of aluminum facing in.[20] The yellowish-brown polyimide gives the surface its gold-like color.

Mechanical parts
Polyimide powder can be used to produce parts and shapes by sintering technologies (hot compression molding, direct forming, and isostatic pressing). Because of their high mechanical stability even at elevated temperatures they are used as bushings, bearings, sockets or constructive parts in demanding applications. To improve tribological properties, compounds with solid lubricants like graphite, PTFE, or molybdenum sulfide are common. Polyimide parts and shapes include P84 NT, VTEC PI, Meldin, Vespel, and Plavis.

Filters
In coal-fired power plants, waste incinerators, or cement plants, polyimide fibres are used to filter hot gases. In this application, a polyimide needle felt separates dust and particulate matter from the exhaust gas.

Polyimide is also the most common material used for the reverse osmotic film in purification of water, or the concentration of dilute materials from water, such as maple syrup production.[21][22]

Flexible circuits
Main article: Flexible electronics
Polyimide is used used as the core of flexible circuit boards and flat-flex cables. Flexible circuit boards are thin and can be placed in odd-shaped electronics.[23]

Other
Polyimide is used for medical tubing, e.g. vascular catheters, for its burst pressure resistance combined with flexibility and chemical resistance.

The semiconductor industry uses polyimide as a high-temperature adhesive; it is also used as a mechanical stress buffer.

Some polyimide can be used like a photoresist; both "positive" and "negative" types of photoresist-like polyimide exist in the market.

The IKAROS solar sailing spacecraft uses polyimide resin sails to operate without rocket engines.[90]