High Temperature Resistant Polymers Research Articles

Reactive extrusion for efficient preparation of high temperature resistant PA6T/66/BN composites with great thermal management and mechanical properties

High temperature resistant polymer-based composite with high thermal conductivity and great mechanical properties are highly demanded in the field of electronic devices for simultaneously meeting surface mounting process and high-power operation. The key to achieving this goal is to balance the contradiction between the high melt viscosity of high-temperature resistant polymers and the dispersibility of fillers. In this work, the high-performance polyamide 6T/66/hexagonal boron nitride (PA6T/66/BN) composites were fabricated successfully via the method combining prepolymerization and reactive extrusion. Results demonstrated that this method not only significantly improves the preparation efficiency of high temperature resistant polyamide and its composites, but also enables the prepared composites to reach 3.6 W/(m⋅K), over 299 °C and 67.8 MPa in thermal conductivity, melting point and tensile strength respectively. Furthermore, the prepared composite exhibits excellent thermal management effects on LED and CPU. Therefore, the results of this work are of great significance for the efficient preparation and wide application of high-temperature resistant polymer based thermally conductive composites.

Significantly improve capacitive properties of alicyclic polyimide dielectrics at high temperatures via hard/soft segment engineering

The demand for high energy storage density and efficiency of polymer film capacitors at high temperatures is urgently increasing in the electronics and electrical field. However, most traditional high temperature resistant polymers exhibit the low bandgap and high conductive loss because of the presence of conjugated aromatic structures, resulting in a significant decrease in the energy storage performance at high temperatures and high fields. In this paper, a series of alicyclic polyimide dielectric films containing hard segment of phenyl imide and soft segment of cyclohexyl imide are designed and prepared. On the one hand, the introduction of non-coplanar alicyclic ring into main-chain of polyimide can break long distance conjugation effect, weaken the intermolecular and intramolecular charge transfer interaction and improve the bandgap. On the other hand, the physical crossing point formed by the soft segments can sharply increase Young's modulus of the polyimide films. As a result, the terpolymer polyimide film (CPI90) with copolymerization ratio of phenyl/cyclohexyl dianhydride of 9:1 achieves a highest discharge energy density (Ud) of 5.59 J cm−3 at 150 °C. Importantly, the CPI90 film can obtain the Ud of 2.74 J cm−3 at 200 °C. In addition, the CPI90 film possesses a good self-healing ability attributing to a small ratio for the carbon to hydrogen and oxygen. This work offers a new strategy for synergistically promoting the bandgap and Young's modulus of polymer dielectrics via molecular and hard/soft segment engineering.

Graphite reinforced polymers for sealing geothermal wells

The objective of this study is to develop high-temperature resistant polymers for sealing geothermal wells by reinforcing inexpensive rubber with surface-treated graphite particles. We respectively treated two types of graphite particles, small-size lamellar graphite (SFG15) and graphite nanoplatelets (GNP), with a mixture of sulfuric and nitric acids. Through surface treatment, carboxylic groups are shown to be formed on graphite surfaces, and their oxygen contents are considerable. Polymer nanocomposites were made by compounding treated graphite particles with ethylene propylene diene monomer (EPDM). Uniform dispersion of treated graphite within developed polymer nanocomposites was achieved. Direct heating of prepared EPDM nanocomposites shows that treated SFG15 and GNP both enhance the temperature resistance of EPDM by over 80 °C. Also, the addition of treated graphite to EPDM remarkably enhances its storage modulus. Among all additive types and concentrations, 3.0 wt% of treated SFG15 performs the best in enhancing the storage modulus (by up to 215.83%) and reducing tan δ, namely the loss factor. Adding treated graphite significantly enhances the specific heat capacity of EPDM and remarkably increases the heat energy required to melt it. The onset degradation temperature of EPDM-SFG15 nanocomposites is 30 °C higher than that of plain EPDM. With these enhanced thermal and mechanical properties, the prepared nanocomposites are a promising candidate for the constituent polymer of seals applicable in geothermal wells.

Synthesis and Characterization of Pyrimidine‐Based Novel Phthalonitrile Resins with Excellent Processing Performance and High Glass Transition Temperature

AbstractThree phthalonitrile monomers containing pyrimidine ring and benzene ring side group were successfully synthesized with 4, 6‐dichloro‐2‐phenylpyrimidine, three kinds of phenols (resorcinol, bisphenol A and bisphenol AF) and 4‐nitrophthalonitrile via nucleophilic substitution reaction. All the phthalonitrile monomers exhibited excellent processing performance due to low melting points (Tm) (below 100 °C) and wide processing windows (difference between melting temperature and curing temperature) above 140 °C. By introducing pyrimidine ring and benzene ring side group, the lower melting point of monomers did not affect the thermal stability and thermal mechanical properties of the phthalonitrile resins based on different bisphenols. In particular, 5 % thermal decomposition temperature (T5%) and glass transition temperature (Tg) of phthalonitrile resin based on resorcinol surpassed 455 and 400 °C while storage modulus (E′) was 3209 MPa. Therefore, phthalonitrile resin containing pyrimidine ring and benzene ring side group have potential applications in the field of high temperature resistant polymers and composites.

Novel liquid phthalonitrile monomers towards high performance resin

Phthalonitrile resins are one of the high temperature resistant polymers which can be potentially used for harsh environments in both military and domestic fields. The high melting points of the monomers led to short processing windows and made processing procedure challenging and energy intensive. To solve this problem, liquid phthalonitrile monomers containing flexible siloxane segments were designed and synthesized. The long bond length and large bond angle of Si-O-Si chain segments introduced flexibility into the monomers and effectively reduced the melting point to −35.9 °C. Meanwhile, the high bond energy preserved the thermal stability of the resulting cured resin. The high fluidity (viscosity of ∼ 2 Pa·s at 30 °C) allows the monomers to be processed at room temperature without additional heating. In addition, the monomers can be dissolved in common organic solvents, such as ethyl acetate and ethanol. The resins cured at 250 °C demonstrated good thermal and thermal oxygen stability. The weight loss of 5 % in argon and air at temperatures of 428.6 °C and 434.9 °C, respectively. Furthermore, blending this liquid monomer blended with powdered monomers improved both the processibility of the high melting monomers and the overall temperature resistance of the cured resin. The resin showed a weight loss of 5 % in argon and air of 534.4 °C and 532.3 °C, respectively.

Preparation and Properties of Intrinsically Black Polyimide Films with CIE Lab Color Parameters Close to Zero and High Thermal Stability for Potential Applications in Flexible Printed Circuit Boards.

Black polymer films with high thermal stability are highly desired in flexible electrical and electronic fields. Conventional black polymer films based on high-temperature resistant polymers and black inorganic dyes are usually suffered from the poor electrical and tensile properties. In the current work, a series of intrinsically black polyimide (BPI) films with International Commission on Illumination (CIE) Lab optical parameters close to zero and high thermal stability have been designed and prepared. For this purpose, an electron-rich aromatic diamine, 4,4′-iminodianiline (NDA), was copolymerized with 1,4-phenylenediamine (PDA) and 3,3′,4,4′-biphenyltetracarboxylic dianhydride (sBPDA) to afford a series of poly(amic acid) (PAA) solutions, which were then thermally dehydrated to provide the final BPI films at elevated temperatures up to 400 °C in air. The molar fraction of NDA in the total diamine monomers was 0 for BPI-0 (sBPDA-PDA), 10% for BPI-1, 20% for BPI-2, 30% for BPI-3, 40% for BPI-4, 50% for BPI-5, and 100% for BPI-6. For comparison, two referenced polyimide (PI) films, including PI-ref1 and PI-ref2, were prepared according to a similar procedure. The former was derived from pyromellitic dianhydride (PMDA) and 4,4′-oxydianiline (ODA) and the latter was from PMDA and NDA. The BPI films exhibited an increasing degree of blackness with the increasing contents of NDA units in the polymer films. For example, the BPI-6 (sBPDA-NDA) film exhibited the optical transmittance of 1.4% at a wavelength of 650 nm (T650), which was obviously lower than those of PI-ref1 (T650 = 74.6%) and PI-ref2 (T650 = 3.6%). In addition, the BPI-6 film showed the CIE Lab parameters of 0.39 for L*, 2.65 for a*, 0.66 for b*, and haze of 1.83, which was very close to the criterion of “pure blackness” for polymer films (L* = a* = b* = 0). At last, incorporation of the NDA units in the rigid-rod BPI-0 (BPDA-PDA) film slightly deteriorated the high-temperature dimensional stability of the derived BPI films. BPI-6 film showed a linear coefficient of thermal expansion (CTE) value of 34.8 × 10−6/K in the temperature range of 50 to 250 °C, which was higher than those of the BPI-0 (CTE = 12.3 × 10−6/K), PI-ref1 (CTE = 29.5 × 10−6/K), and PI-ref2 (CTE = 18.8 × 10−6/K) films. Nevertheless, the BPI films maintained good thermal stability with the 5% weight loss temperatures (T5%) higher than 590 °C, and the glass transition temperatures (Tg) higher than 340 °C.

High Temperature Resistant Flexible Silicone Laminate for Thermal and Structural Applications in the Composite Structures of Launch Vehicles

High temperature resistant and flexible polymeric laminates are highly desirable as thermal and structural back-up to prevent through—delaminations from growing in to a burn—through in the composite structures of launch vehicles. Phenylated silicones are promising high temperature resistant polymers. However, limited work has been reported on the development of fibre-reinforced and room temperature curable silicone laminates that exhibit high temperature resistance characteristics based on silicone polymers. Hence, an attempt is made herein to develop flexible and high temperature resistant silicone laminates based on phenylated silicone polymer and E-glass fabric and to evaluate its high temperature properties. Herein, high molecular weight vinyl terminated poly (dimethyl-co-diphenyl)siloxane polymer (V-PDMPS) has been reinforced with mixed inorganic fillers, catalyst and the cross linker, trimethylsilyl terminated poly (dimethyl-co-methylhydrogen-co-diphenyl)siloxane, (TMS-PDMHS) and laminate has been prepared using two layers of E-glass fabrics as the reinforcement, followed by curing under ambient to form the silicone laminate. Isothermal TGA analysis of the laminate at 300 °C for 30 min shows negligible mass loss. Furthermore, the laminate exhibits good mechanical and adhesive strength over wide temperature range from RT to + 300 °C proving its high temperature resistant characteristics.

Epoxy resins for high temperature resistant polymer materials

The review of epoxy resins, produced by foreign companies and developed in foreign research institutions, which provide high temperature resistant polymers.

High-temperature resistant water-soluble polymers derived from exotic amino acids.

High-performance water-soluble polymers have a wide range of applications from engineering materials to biomedical plastics. However, existing materials are either natural polymers that lack high thermostability or rigid synthetic polymers. Therefore, we design an amino acid-derived building block, 4,4′-diamino-α-truxillate dianion (4ATA2−), that induces water solubility in high-performance polymers. Polyimides containing 4ATA2− units are intrinsically water-soluble and are processed into films cast from an aqueous solution. The resulting polyimide films exhibit exceptional transparency and extremely high thermal stability. In addition, the films can be made insoluble in water by simple post-treatment using weak acid or multivalent metal ions such as calcium. The synthesized polyimide's derived from bio-based resources are useful for yielding waterborne polymeric high-performance applications.

Enhanced thermal property via tunable bisphenol moieties in branched phthalonitrile thermoset

The development of high-temperature resistant polymers and their composites is of particular interest because of their ever-growing applications. Herein, a family of branched phthalonitrile resins based on different bisphenols (Hydroquinone, 4,4′-Biphenol, m-Dihydroxybenzene, 1,6-Dihydroxynaphthalene, 2,6-Dihydroxynaphthalene) and phenyl-s-triazine, endcapping with 4-nitrophthalonitrile were prepared via a convenient condensation polymerization procedure. The relationship among bisphenol structures, thermal properties and mechanical properties were investigated in details. By incorporating the thermally stable phenyl-s-triazine segment into the branched phthalonitrile's backbone, the overall Tg (glass transition temperature) and Td (5% thermal degradation temperature) of the derived polymers were significantly improved. The resins were thermally cured to networks with 4,4′-diaminodiphenyl sulfone (DDS) as curing agent. The resulting networks exhibited high thermal resistance, indicated by Tg surpassing 500 °C and Td as high as 575 °C. Additionally, the composites exhibited high mechanical properties and dielectric properties stability at 500 °C. The results suggested the merits of branched phthalonitrile polymers for applications in high-temperature resistant polymers and composites.

Investigations of Novel High-Temperature Resistant Polymers for Electro-Optical Applications in Signal Processing Systems

In this paper the novel high-temperature resistant polymers with nonlinear optical properties have been synthesized, characterized and tested for use in electro-optical components with high bit rate optical signal processing systems and for dynamic holography. The characterization that has been reported include the measurement of second-order nonlinear susceptibility by second harmonic generation, UV-VIS spectroscopy, XRD measurement dielectric relaxation, glass transition temperature and molecular weight distribution before and after artificial ageing. Also, we have done AFM investigations and profilometry measurements for stamp patterning layers. The application of the new polyimides for electro-optic devices has been evaluated by creation of thin oriented polymer films on various substrates and preparation of planar and strip waveguides.

Outgassing behavior of different high-temperature resistant polymers

In vacuum applications, polymers often need to be used in spite of their relatively high outgassing rates, e.g., as sealing or spacer material. For some polymers—like Viton®, which is used for O-rings—data on outgassing rates can be found in literature, while for others, in particular, the most relevant ones that can be used at higher temperatures, only few results are available. Therefore, different high-temperature resistant polymers were measured at the Outgassing Measurement Apparatus, which uses the difference method. These polymers were polyimides like Kapton®, Vespel®, and Meldin®, as well as a polyetheretherketone and a polybenzimidazole. In order to investigate the temperature behavior of the outgassing of the polymers, the measurements were performed at room temperature, 100 °C, and 200 °C. The outgassing species were determined by a mass spectrometer. In addition, the dependence of the outgassing on the material thickness was analyzed. The paper shows that the outgassing rates of the examined polymers are higher than 10−4 (Pa m3)/(s m2) after 10 h at room temperature, except for the thin Kapton samples. Thus, further treatment of the materials will be necessary depending on the application. It is shown that a vacuum bake-out at not less than 200 °C is favorable. The main outgassing species is water, as expected, but also different hydrocarbons with higher mass can be seen for the polyimides. Concerning different thicknesses, the outgassing rate of a thin sample generally decreases more steeply than the outgassing rate of the thicker sample. Nevertheless, the steepest decrease was found for the thickest Kapton sample, with a difference of nearly factor 500 between 10 and 100 h at room temperature.

Chemoenzymatic synthesis of poly(phenylene disulfides) with insulating properties and resistant to high temperatures

AbstractBACKGROUNDCyclic aromatic disulfides (CAD) can be used as cross‐linking agents or precursors for the synthesis of high temperature resistant polymers such as poly(phenylene disulfides) (PPD). Chemical synthesis of CAD relies on the use of corrosive agents, detrimental for the environment. This paper reports an environment friendly chemoenzymatic procedure to obtain PPD starting from simple aromatic dithiols.RESULTSThe enzymatic reaction was carried out in an aqueous mixture with acetonitrile as co‐solvent, using 1,4‐ and 1,3‐benzenedithiol as monomers and a fungal laccase (EC 1.10.3.2) as catalyst. The products obtained were identified as mainly cyclic aromatic disulfides. Thermal analysis suggested that the enzymatically‐synthesized CAD display thermal stability and are amenable precursors of high molecular weight sulfur‐containing polymers through solvent‐free, melt ring opening polymerization (mROP). After mROP, polymeric molecules around 12.8 kDa were obtained and identified as PPD. The resultant PPD shows uniform size, resistance to temperatures up to 400 °C and electrical insulating properties.CONCLUSIONLaccase‐catalyzed synthesis of CAD represents a novel reaction, not previously described elsewhere for oxidoreductases. A 100% substrate conversion was achieved under mild reaction conditions and no over‐oxidation of CAD was observed, representing an advantage over chemical synthesis. The CAD products precipitated completely from the reaction medium, thus simplifying the purification process. © 2017 Society of Chemical Industry

A Novel Fracturing Fluid System with Ultra-Low Concentration and High Temperature Resistant

According to the low permeability reservoir, fracturing transformation has some requirements on fracturing fluid system with low cost, low damage, and high temperature resistant. First of all, we are able to begin from the concentration of thickener and cross-linking system and then see Synthesis of high temperature resistant polymers as thickening agent. In addition, Non metal ion compounds are introduced as cross-linking agent. Moreover, we will have a performance evaluation on the fracturing fluid system which has been formed, obtaining the best receipe with ultra low concentration and high temperature resistance (calculate according to the mass concentration ):0.075% thickener agent +0.015%pH value regulator +0.25% cross-linking agent +0.01% coagulant +0.4% cleanup agent. This fracturing fluid system has a lot of excellent characteristics such as low density, low cost, low residue, low fluid loss, no metal ion and so on . It also cuts down the use-cost of fracturing fluid and reduces the damage to the Stratum towards which fracturing fluid has. The favorable Cross-linking system fill the gap that we use the non metal ion as cross-linking agent in our present fracturing fluid system at home and abroad.

Physicochemical Characterization of Two Polysulfon‐Amides in Dilute Solution

AbstractSummary: As one class of high temperature resistant aromatic polymers, polysulfonamides (PSA) are widely used in industry, physicochemical properties and conformation in solution have not been disclosed yet. In this work, the dilute solution behaviour of poly(m‐diphenylsulphone terephthal amide) (m‐PSA) was investigated by laser light scattering (LLS) and viscometry. The results showed that the m‐PSA exists as single chains both in dimethylsulfoxide (DMSO) and dimethylformamide (DMF). The value of radius of gyration to hydrodynamic radius (s/Rh) indicats that the m‐PSA has a random coil conformation in solution. Both the persistence length a and the characteristic ratio C∞ indicate that the m‐PSA chain is flexible in solution. The Mark‐Houwink equation of m‐PSA in DMSO was determined as [η] = 1.62 × 10−5M, and the exponent of 0.87 supports the assumption that m‐PSA forms random coils in DMSO‐solution at 25 °C. It was found that the flexibility of the PSA was affected when 4,4'‐diphenylsulphone terephthalamide monomer was incorporated in backbone. The PSA random copolymer (r‐PSA) with a comonomer ratio of 3:1 (4,4′‐diaminodiphenyl‐ sulfone to 3,3′‐diaminodiphenylsulfone) also had a random coil conformation in DMF; the rigidity increased, while the mobility of the chain was maintained.

Laser Sintering of High Temperature Resistant Polymers with Carbon Black Additives

Abstract Selective laser sintering (SLS) experiments with polyetherketone (PEK) and polyetheretherketone (PEEK) powders are described. The absorption behaviour of the polymer powders has been investigated with respect to the content of carbon black as an IR-absorber in the range from 0.03 to 0.1 wt.%. Laser sintering process studies have been carried out at room temperature using a Q-switched Nd:YAG laser system. The sintering depths of single layer substrates have been determined according to the process parameters, such as laser power, scanning speed and hatch distance. These process parameters have been optimised with the goal of achieving good structural integrity of the substrate. The influence of melt viscosity has been determined by comparing PEEK powders of low and standard melt viscosity. Scanning electron micrographs show the morphology of the original polymer powders and the laser sintered specimens. On the basis of the experimental results a qualitative SLS mechanism is proposed to describe the energy transfer from the carbon black particles to the surrounding polymer powder.

Recent advances in polymer composites' tribology

An overview is given on the friction and wear properties of high temperature resistant polymers, in particular polyetheretherketone (PEEK), under various testing conditions against smooth steel counterparts. The effects of internal lubricants, especially polytetrafluoroethylene (PTFE), and short fibre reinforcements (glass vs. carbon) are outlined. In addition, results of sliding wear experiments with continuous glass, carbon or aramid fibre-polymer matrix composites against steel were used to develop a hypothetical model composite with optimum wear resistance.

Lithographic applications of excimer laser exposures of polymeric films.

KrF excimer laser lithography is a major candidate for sub-half micron VLSI technology, although it has many problems. The main topics of the present paper is not the excimer laser lithography, but a lithographic application of excimer laser photoablation, and surface modifications of polymer films, including silylation and metallization induced by excimer laser irradiation. Because the main application of excimer laser ablation is contact hole fabrication, photoablation of Teflon or Teflon like materials is important. We carried out photoablation of Teflon AF (a copolymer of tetrafluoroethylene and 2, 2-bis(trifluoromethyl)-4, 5-difluoro-1, 3-dioxolene) using a dopant at 193 and 248nm. High temperature resistant polymers like polyimides and polyphenylquinoxaline show imagewise wetting after excimer laser exposure in air, giving rise to direct surface silylation of these materials. Although we have not carried out image transfer experiments yet, XPS data clearly showed silicon incorporation. Imagewise metallization of these polymer surfaces after ArF excimer laser exposure in air showed some interfacial compound formations between exposed polymer surfaces and metal deposited. The XPS data of gold on PPQ exposed in air will be discussed.Effects of excimer laser exposures on polymer surfaces are repoorted, which include photoablation of Teflon AF by ArF and KrF excimer laser pulses, and surface modifications of some unsolved questions of the nature of interactions between deposited metals and laser exposed polymer surfaces. The study on these problems are in progress.

High-temperature polymers for adhesive and composite applications

The aerospace industry is currently making extensive use of both structural adhesives and composite materials in aircraft and space vehicle construction. Within the past decade, there has been a growing requirement for adhesives and composites capable of withstanding temperatures in excess of 150°C for both short- and long-term applications. Although polymers offering such capabilities have been commercially available for many years, in numerous cases adverse processing characteristics have severely restricted their acceptance. As a result, substantial efforts have been made to develop high temperature resistant polymers having considerably improved processing characteristics. In this paper, a critical assessment is given of the use of high-temperature polymers in both adhesive and composite applications with particular emphasis on some of the newer, more easily processed types which are, or will probably be, commercially acceptable.MST/659

The characteristics of high-temperature resistant organic polymers and the feasibility of their use as glass coating materials

It is desirable to protect pristine glass surfaces from frictive damage by applied coatings and thereby maintain large proportions of the inherently high tensile strength of such glass surfaces. These protective coatings should ideally be applied to glass surfaces immediately after they are formed into their desired configuration. This ideal concept requires that lubricous coatings be able to withstand elevated temperatures with minimal degradation of their protective properties. The majority of aliphatic polymers thermally degrade at temperatures less than 250° C and thus are not useful in the present desired application. The factors which increase the thermal stability of organic polymers beyond this temperature are discussed. The thermal stabilities of two classes of high-temperature resistant polymers, namely polyimides and polybenzimidazoles (PBls), are reviewed. Finally, results are reported of laboratory experiments to determine the feasibility of using PBls as a coating material when applied to glass substrates heated to elevated temperatures.