NEW-TPI thermoplastic polyimide: Structure and relaxation using SAXS and TSDC

The thermoplastic polyimide Regulus^TM NEW-TPI has been studied using small-angle X-ray scattering (SAXS) and thermally stimulated depolarization current (TSDC). SAXS was used to study the development of lamellar structure during isothermal or nonisothermal crystallization. The one-dimensional electron-density correlation function was used to determine structural parameters. The long period, lamellar thickness, and amorphous layer thickness increase as crystallization temperature increases from 300 to 360°C. By combining melting-point data with SAXS results, we report the side and fold surface free energies of NEW-TPI crystals, which are 29 ± 3 and 41 ± 3 erg/cm², respectively. Real-time SAXS was carried during nonisothermal cold-crystallization at 5°C/min. The long period decreases, while lamellar thickness, linear crystallinity, and interphase thickness increase, with increasing temperature. These changes are explained by a crystal-insertion model. TSDC was used as a more sensitive probe of the amorphous phase structure below 300°C. Both semicrystalline and amorphous NEW-TPI exhibit complex TSDC behavior. Above the glass transition, amorphous NEW-TPI has a strong TSDC peak attributed to short-range-ordered structures, which may serve as nucleation sites for subsequent crystallization. This peak was not seen in semicrystalline material. At the glass transition, both amorphous and semicrystalline NEW-TPI have a strong TSDC peak. In the semicrystalline polymer, relaxation of the amorphous dipoles is slightly restricted by the crystals, which results in a smaller relaxation peak and a shift to higher temperature. Below T_g, another TSDC peak occurs which is not due to dipolar relaxation. This peak is attributed to the combined effects of space charge, electrode type, ionizable species, and interfacial charges. © 1995 John Wiley & Sons, Inc.     

Zone drawn NEW-TPI thermoplastic polyimide and its blends with Xydar liquid crystalline polymer

In this work we report the effects of single stage zone drawing on the properties of NEW-TPI thermoplastic polyimide homopolymer, and its blends with Amoco's Xydar liquid crystalline polymer. Zone drawing was performed first on homopolymer NEW-TPI films to determine the effect of load weight, heater speed, and drawing temperature on the attainable draw ratio. Degree of crystallinity and chain orientation increase as the draw ratio increases for NEW-TPI. Blends of NEW-TPI/Xydar compositions 90/10 and 70/30 were studied next. In blends, the Xydar component is not molecularly dispersed, and is initially preferentially oriented along the machine direction during the film processing stage. Xydar acts as a nucleation site and lowers the temperature for crystallization of the NEW-TPI from the rubbery amorphous state. Zone drawing was performed either parallel or perpendicular to Xydar's initial preferred orientation direction. Blends with lower Xydar fraction could be zone-drawn to higher ratios. Zone drawing perpendicular to Xydar's initial orientation direction also resulted in increased draw ratio. Dynamic mechanical properties of the zone drawn materials were studied. In homopolymer NEW-TPI, dynamic modulus increased by a factor of two to 4.0 GPa in zone drawn films, largely as a result of the formation of oriented crystallites. In the blends, the modulus parallel to Xydar's initial orientation direction was greater than that in the transverse direction. Depending upon composition and test direction, zone drawing increased the dynamic moduli of the blends from 1.5 up to 2.7 times, in the temperature range from 150°C to 300°C.     

聚酰亚胺微粒的研发及应用

聚酰亚胺（polyimide,PI）在已商品化的塑料中耐热性是最好的,其产品以超级工程塑料为代表。PI由美国杜邦公司于1960年开发成功并投入市场,先用于宇宙飞船的外保护膜及宇航员服装等特殊领域,随后应用范围逐步扩大到运输、电气电子、     

热塑性聚酰亚胺增韧环氧树脂胶粘剂的研制

利用热塑性聚酰亚胺粉末增韧改性环氧树脂,得到了综合性能优异的胶粘剂体系,并对其凝胶化时间、接触角、表面能、疏水性、耐热性等各项性能进行了研究。     

Adhesion of polyimide to silicon and polyimide

The characteristics of the adhesions of polyimide to silicon and to polyimide and the autohesion of a polyimide blend have been investigated. As found, the peel strength of pyromellitic dianhydride–4,4′-oxydianiline (PMDA–ODA) on silicon can be greatly improved by blending with 20 or 40% benzophenone tetracarboxylic dianhydride–p-phenylene diamine (BPDA–PDA). Exposing in air for a 2 day period resulted in a serious deterioration in adhesion for the pure PMDA–ODA system, while in no deterioration for the blend systems. Regardless of adhesion or autohesion, the resulting peel strength decreased markedly with the increase of the curing temperature. It was also found that based on the same curing temperature the diffusion of NMP is much faster in the film of PMDA–ODA than in the blend containing 20% BPDA–PDA. Beside curing temperature, imide-to-imide compatibility seems to play an important role in affecting the adhesion characteristics. © 1993 John Wiley & Sons, Inc.     

Networks and crystallinity

Three different aspects of the relation between networks and crystals are presented and discussed. (1) Crystallization of networks; (2) network formation through crvstallization; (3) influence of crystallinity on network formation as induced by radiation.     

Low dielectric constant polyimide mixtures fabricated by polyimide matrix and polyimide microsphere fillers

Polyimide microspheres were prepared via non‐aqueous emulsion polymerization by using pyromellitic dianhydride (PMDA) as anhydride monomer and 2,2‐bis(4‐(4‐aminophenoxy)phenyl)propane as amine monomer. The polyimide microspheres were well characterized by Fourier transform infrared spectroscopy, SEM and laser particle size analyzer. They were spherical in shape and monodisperse and their size was 31–33 μm. Polyimide mixtures formed by polyimide microspheres as fillers and polyimide composed of pyromellitic and dianhydride 4,4′‐oxydianiline (ODA) as matrix were investigated with regard to thermal properties, dielectric properties and mechanical properties. With 10%–50% polyimide microspheres in the polyimide mixtures, the dielectric constants were 2.26–2.48 (1 MHz) and the loss tangents were 0.00663–0.00857 (1 MHz), which were both significantly lower than the values for ODA‐PMDA polyimide. The decomposition temperature and glass transition temperature were above 440 and 290 °C. The polyimide mixtures possessed excellent thermal resistance. When the percentage of polyimide microsphere addition was 30%, the polyimide mixtures had the largest tensile strength (128.50 MPa) and elongation at break (9.01%). These results indicate that the polyimide microspheres were used as both low dielectric fillers and reinforcing fillers. © 2020 Society of Chemical Industry     

Concerning voids in polyimide

Small angle X-ray scattering (SAXS) has been used to evaluate the size and concentration of voids in poly(N,N′-bis-(phenoxyphenyl)pyromellitimide), PMDA-ODA. Analysis of the angular dependence of the scattering indicates the presence of voids ranging from 50 to 150 Å in radius. Integrated SAXS demonstrated that the volume fraction of voids was 7 × 10^?4. These results were supported by measurements of the attenuation factor as a function of the sample thickness.     

Crystals and crystallinity in polymeric materials

A new view of the concepts of crystallinity and crystals in synthetic macromolecules is discussed. In polymeric materials, crystallinity may be present with the concomitant occurrence of large amounts of structural disorder and in the absence of true three-dimensional long-range order. The structures of semicrystalline polymeric materials are discussed in terms of idealized limit models of crystals, where long-range order may be achieved for structural features that are not necessarily coincident with single atoms and are not necessarily point-centered. Typical examples of non-point-centered structural features are the straight lines corresponding to the chain axes of polymer molecules. This view explains the unusual ability of polymers to crystallize even in the presence of a high degree of structural disorder.     

聚酰亚胺的改性研究新进展

综述了近几年聚酰亚胺的改性方法的研究状况。     

Molecular probe studies of crystallinity in polyethylene

The molecular probe technique uses a standard gas chromatograph modified to obtain a printed digital record of retention time vs. column temperature to be obtained automatically. From this the observed specific retention time, V_g, can be calculated. If V_g is the theoretical value it can be deduced that: % Crystallinity = [1 ? V_g/V_g′ ] × 100. Experimental results using Tenite 800 and Tenite 3310 polyethylene produced and sold by Eastman Chemical Products Inc., Kingsport, Tennessee, U.S.A. justify this equation.     

Orientation and crystallinity in film casting of polypropylene

In the cast film process a polymer melt is extruded through a slit die, stretched in air, and cooled on a chill roll. During the path in air the melt cools while being stretched. Film casting experiments were carried out with an isotactic polypropylene resin. The temperature and width distributions were measured along the draw direction. Further, the crystallinity and Hermans orientation factor were measured on the final film. The process was described by a simple thermomechanical model derived elsewhere. The evolution of the molecular orientation parameters was calculated on the basis of a dumbbell model coupled with velocity and temperature distributions provided by the thermomechanical model. The experimental crystalline orientations of the final films collapsed into a single step‐shaped curve (from low to high orientation) if plotted versus the stress calculated by the model at the frozen line. The experimental values of the crystallinity and Hermans orientation factors are discussed on the basis of predictions of the dumbbell model for melt orientation at the frozen line and the crystallinity data obtained in quiescent conditions under the same cooling rate. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 1981–1992, 2002; DOI 10.1002/app.10422     

Development of polyimide membranes for the separation of water vapor from organic compounds

Attempts were made to develop solvent‐resistant polyimide capillary membranes with integrally skinned asymmetric structure to be used for the treatment of wood dryer emissions or vacuum pyrolysis aqueous effluents. Model mixtures of 1‐propanol (1‐PrOH)/H₂O and acetic acid (AA)/ H₂O, with concentrations of 10–90 wt % of organic components, were used as vaporous feeds. Solvent‐resistant membranes with good mechanical and excellent vapor separation properties were prepared from polyimides based on PMDA and BPDA by the dry/wet phase‐inversion technique. Molecular structure largely influences membrane properties. For the asymmetric polyimide membranes studied, a tendency similar to that of homogeneous dense membrane was found. Membranes prepared from polyimides with diamine and dianhydride moieties, both containing rigid backbone and aromatic rings, displayed higher permeability and selectivity. Test conditions exhibited influences on membrane separation performance. Membranes prepared from copolyimide BPDA–50DDS/50ODA and PMDA–50DDS/50ODA exhibited the best mechanical and chemical properties as well as water vapor separation properties, which are considered to be of practical usefulness for applications of these membranes in the removal of water from water/organic mixtures. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 139–152, 2002     

氯化聚乙烯残余结晶度的测定

试验研究氯化聚乙烯（CPE）残余结晶度的测定.结果表明,用差示扫描量热（DSC）法直接对CPE样品进行残余结晶度测定,灵敏度较低,通用型CPE残余结晶度测定结果偏低;采用溶剩物-DSC法测定,可大幅提高检测灵敏度和准确性.     

Thermostable foam organoplastics made from polyimide binders and polyimide felt

A series of composite materials of a new type — foam organoplastics — was obtained from foamed polyimide binders reinforced with Arimid T polyimide felt, and commercially available aromatic monomers were used. Use ofDPO (3,3′,4,4′-diphenyloxidetetracarboxyic acid) dianhydride in the H-complex allows obtaining a melt of lower viscosity (300 Pa-sec), and the viscosity almost does not change at 95°C for 20 min. The viscosity of melts of the H-complexes based on BZP (3,3′, 4,4′-benzophenonetetracarboxylic acid) tends to increase rapidly to the level of 10⁵ Pa·sec, probably due to further “crosslinking” of the H-complex in the conditions of the melt. Replacing the carcinogenic 4,4′-diaminodiphenylmethane (DADPM) diamine by commercially available 4,4′-diaminodiphenyl ether (DADPE) does not significantly alter the rheological behavior of the H-complex melt at 95°C and does not decrease the mechanical characteristics of the foam composites. The mechanical characteristics (bending strength, compressive and shear moduli) of the foam composites based on H-complexes with DPO dianhydride are 1.5 times higher than for the same foam composites using BZP dianhydride. The foam composites based on DPO do not undergo brittle failure but simply bend in bending tests, which can be used to obtain new elastic foam materials. The effect ofnanoparticles on the properties of the foam composites was established. It is expedient to use montmorillonite nanoparticles, which increases the modulus of elasticity and rigidity of the material. __________ Translated from Khimicheskie Volokna, No. 5, pp. 66–70, September–October, 2006.     

Autophotosensitive negative polyimide

A novel autophotosensitive polyimide (APSPI) was synthesized through introducing benzophenone (BP) moiety into the backbone chain and acrylate group into side chain of PI. The BP moiety can generate active radicals, which can initiate acrylate group to form crosslinked network. The study of photosensitive properties revealed its good photolithographic properties, with a resolution about 12 μm and a sensitivity of 330 mJ/cm². © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Sequence length and crystallinity in alpha-olefin terpolymers

The minimum sequence length for crystallisation in a polymer was determined by a novel kinetic approach using sequence analysis of a series of blocky terpolymers. Copolymers and terpolymers of ethylene, propylene, and but-l-ene were prepared with a Ziegler–Natta catalyst system. Compositions of feeds and polymers were analysed, and kinetic reactivity parameters were calculated using both the Fineman–Ross and Alfrey–Goldfinger approaches. The parameters were then applied to determine the sequence length distribution of each component in the terpolymers. Also, deliberate control of sequence lengths enabled synthesis of heptane-soluble, rubbery polymers even using a catalyst system which normally produced blocky materials. Crystalline contents of the terpolymers were determined experimentally by nitric acid digestion. A critical comparison of the measured crystallinities with the calculated sequence length distributions was thereby made possible. From this comparison a minimum sequence length of monomer below which crystallisation did not occur was estimated; this length was approximately 20 backbone carbon atoms.