Poly imide processibility

Mitsui Chemicals is launching a new grade of carbon nanotube reinforced thermoplastic poly-imide, Aurum CNT, with supplementary specific properties such as dust reduction and antistatic behaviour. Targeted applications are, for example, processing jigs for semiconductor or hard disk manufacturing, and parts for hard disk drives. 

Throughout this chapter the chemical concepts employed to synthesize and cure addition poly(imides) have been discussed and their use as matrix resins for fiber composites has frequently been mentioned. The most important property of the imide backbone structure is the inherent thermal stability. The target of achieving the temperature performance of linear poly(imide) has not been reached, because of the aliphatic nature of the reactive endgroups, and because of the low molecular weight of the imide backbone required for processing. Future developments of addition polyimides will, as in the past, focus on the requirement of high thermal and thermal oxidative stability of the crosslinked... 

The latter property is somewhat of a mixed blessing, however. Poly(imides) are only soluble, for the most part, in extreme solvents such as concentrated sulfuric acid, fuming nitric acid and m-cresol. This lack of solubility in common solvents and their high melt temperatures render poly(imides) virtually intractable. For this reason, processing of the poly(imides) directly is often avoided by utilizing the polyfamic acid) precursor (Scheme 54). The more processable poly(amic acid) can be cast from solution, for example, and the poly(imide) may be generated in the desired configuration by thermolysis at 300 °C. 

US 5,028,681 (American) 1991 Novel poly(imide siloxane) block copolymers and process for their preparation General Electric EN Peters Injection moldable block copolymers with high IV and excellent chemical/physical properties. Blends useful for impact modification Novel siloxane-imide block copolymers and a process for their preparation are covered. The method involves reacting a hydroxy-terminated polyimide oligomer with a siloxane oligomer with dimethylamino, acetyl or chlorine end-groups... 

Many poly(imide)s are insoluble in their processed form, either because of interchain charge-transfer interactions, or because of the presence of crosslinks in cured poly(imide) resins. The range of analytical techniques available to characterize processed poly(imide)s is therefore limited. NMR spectroscopy, and in particular solid-state NMR [1-3], has an important role to play in the determination of structure, conformation, morphology and molecular motion in poly(imide) materials. The aim of this chapter is first, to briefly summarize the various classes of poly(imide)s, second, to review the current literature on NMR of these materials and finally, to hopefully indicate where NMR spectroscopy will make further additions to the knowledge of the properties of poly(imide)s. 

There is much interest in the formation of blends of poly(imide)s with other polymers, so as to improve properties such as toughness and processability [14-19, 58, 59]. The subject of measurement of interactions and miscibility of blends by NMR spectroscopy has been discussed by Takagoshi and Asano in Chapter 10 of this book, and will not be referred to in detail here. The use of NMR to study miscibility in blends containing poly(imide)s is somewhat restricted because most poly(imide)s contain a high proportion of aromatic groups, and consequently form blends with other highly aromatic polymers. The CPMAS spectra, which as discussed above are broad and... 

A large number of linear aromatic poly(imide)s are highly intractable and cannot be processed due to the inherent stiffness of the chains and, more importantly, due to strong interactions between aromatic rings on adjacent polymer chains. An approach to improve the processability of such stiff macromolecules is to attach flexible alkoxy chains to the aromatic rings (see, for example. Refs. [63-65]). 

For passivation applications,the use of the ultrapure polyamic acid involves some changes in the routine processing. The poly-imide passivation process consisted of the following steps ... 

Blends of poly(aryl ether ketone)s and certain poly(amide imide)s and poly(imide)s (PI)s are highly compatible. They tend to form one phase in the amorphous state, and thus are miscible systems. As a result, such blends significantly improve the processability of the poly(amide imide) or the PI material. Further, by increasing its Tg, the ultimate use temperature of the poly(aryl ether ketone) is significantly increased. ... 

S. K. Ihm, C. G. Oh, J. H. Ahn, J. C. Kim, and D. C. Sherrington. Poly-imide-supported transition metal complex catalyst and process for preparing epoxy compounds using the same. US Patent 6063 943, assigned to Korea Advanced Institute of Science and Technology (KR), May 16,2000. 

The polymerization is carried out in two stages—initially the aromatic poly-imide is obtained and in the latter stage, etheric bonds are introduced. The polymer is thermoplastic. PEI represents an unique engineering polymer exhibiting a superb combination of mechanical and thermal performance, easy processibility together with a reasonable price. It also withstands UV radiation, fire and many chemicals, but may be sensitive to alkalinity. Mainly reinforced, it serves as a substitute for metals in first class electronic and engineering appliances. 

Water offers environmental and economic benefits. However, there emerges one disadvantage of this method, as the process is complete in one step. The aqueous poly(imide) synthesis route results in products that are not processable, if the resulting PI is insoluble and infusible [35]. Alternatively, fluorinated monomers can be used to get processable and high-temperature stable products. Or else, low-molecular-weight intermediate thermoset products could be produced. 

A poly(imide-siloxane)/titania hybrid film was fabricated by a sol-gel process by the in situ formation of titania within the poly(imide-siloxane) matrix [85]. The poly(amic acid siloxane) polymer was prepared from 4,4 -oxydiphthalic anhydride, 2, 2-bis [4-(4-aminophenoxy) phenyl] propane, and a,a>-bis(3-aminopropyl)polydimethylsiloxane. Acetylace-tone was used as chelating agent in order to reduce the rate of hydrolysis of titanium alkoxide in the polymer. The presence of titania on the surface of eventually produced films enhances the adhesive strength at the interface. 

Pinson DM, Yandek GR, Haddad TS, Horstman EM, Mabry JM. Thermosetting poly(imide silsesquioxane)s featuring reduced moisture affinity and improved processability. Macromolecules 2013 46(18) 7363-77. 

Poly(imide-co-amides) are easier to produce and to process than aromatic polyamides or polyimides. Like these, they are used in particular for electrical insulation coatings. As the ratio of imide/amide increases, the thermal stability of the copolymers increases, but the flexibility of the product deteriorates. 

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