Paul M. Hergenrother

The Use, Design, Synthesis, and Properties of High Performance/High Temperature Polymers: An Overview

An overview of the definition and development of, factors that contribute to, applications and markets for and the design of high performance/high temperature polymers is presented. Of the many families of high performance/high temperature polymers known, the most popular families consisting of polyimides, polyarylene ethers and phenylethynyl-terninated oligomers are used to demonstrate the basic principles in polymer development. Chemical structure/property relationships are used to show how polymers can be designed with a unique combination of properties. The estimated worldwide market for high temperature polymers in 2000 was 206,700,000 kgs constituting

Poly(arylene ethers)

4.36B with polyimides comprising 3,982,000 kgs or

Polyimides from 2,3,3',4'-biphenyltetracarboxylic dianhydride and aromatic diamines

1 .07B (24% of the dollar value). With an improvement in the world economy, this market is predicted to grow substantially

Chemistry and properties of imide oligomers end-capped with phenylethynylphthalic anhydrides

Abstract Several new arylene ether homopolymers and copolymers have been prepared by the nucleophilic displacement of aromatic dihalides with aromatic potassium bisphenates. Polymer glass transition temperatures ranged from 114 to 310°C and a few of the polymers were semicrystalline. Two ethynylterminated poly(arylene ethers) were synthesized by reacting hydroxy-terminated oligomers with 4-ethynylbenzoyl chloride. Heat induced reaction of the acetylenic groups provided materials with good solvent resistance. The chemistry, physical and mechanical properties of the polymers are discussed.

Oligomers and Polymers Containing Phenylethynyl Groups

The present invention relates generally to polyimides. It relates particularly to novel polyimides prepared from 2,3,3′,4′-biphenyltetracarboxylic dianhydride and aromatic diamines. These novel polyimides have low color, good solubility, high thermal emissivity, low solar absorptivity and high tensile strength.

High Temperature Transfer Molding Resins: Laminate Properties of PETI-298 and PETI-330

Abstract A series of phenylethynyl-terminated imide oligomers were prepared by the reaction of aromatic dianhydride(s) with a stoichiometric excess of aromatic diamine(s) at calculated number average molecular weights of 1500–9000 g mol −1 and end-capped with phenylethynylphthalic anhydrides in N -methyl-2-pyrrolidinone. Unoriented thin films cured in flowing air to 350°C exhibited tensile strengths and moduli of 105.5–139.3 MPa and 2.8–3.2 GPa at 23°C, respectively, with good retention of properties at 177°C. Stressed film specimens exhibited excellent resistance to a variety of solvents after a 2 week exposure period at ambient temperature. One phenylethynyl-terminated imide oligomer was selected for more extensive evaluation and gave high fracture toughness, adhesive and composite properties. The chemistry, physical and mechanical properties of these materials are discussed.

Oxygen plasma-resistant phenylphosphine oxide-containing polyimides and poly(arylene ether heterocycle)s: 2

2. DISCUSSION....................................................................................................... 209 2.1. Polymers Containing Pendant Phenylethynyl Groups............................... 209 2.2. Oligomers Terminated with Phenylethynyl Groups .................................. 214 2.3. Oligomers Terminated with Multiple Phenylethynyl Groups ................... 223 2.4. Oligomers Containing Pendant Phenylethynyl Groups ............................. 224 2.5. Curing of Phenylethynyl Groups ............................................................... 226

Isomeric Biphenyl Polyimides. (II) Glass Transitions and Secondary Relaxation Processes

Two phenylethynyl terminated oligomers designated PETI-298 and PETI-330 were developed at the NASA Langley Research Center and have emerged as leading candidates for composite applications requiring high temperature performance (i.e. ≥ 288 °C for 1000 hours) combined with the ability to be readily processed into composites without the use of an autoclave or complex or lengthy cure or postcure cycles. These high performance/high temperature composites are potentially useful on advanced aerospace vehicles in structural applications and as aircraft engine components such as inlet frames and compressor vanes. The number designation (i.e. 298, 330) refers to the glass transition temperature in degrees Centigrade as determined on neat resin cured for 1 hour at 371 °C. The resins are processable by non-autoclave techniques such as resin transfer molding (RTM), vacuum assisted RTM (VARTM) and resin infusion (RI). Both resins exhibit low complex melt viscosities (0.1-10 poise) at 280 °C and are stable for ≥ 2 hours at this temperature. Typically, the resins are melted, de-gassed and infused or injected at 280 °C and subsequently cured at 371 °C for 1-2 hours. Virtually no volatiles are evolved during the cure process. The resin synthesis is straightforward and has been scaled-up to 25 kg batches. The chemistry of PETI-298 and PETI-330 and the RTM AS-4 and T-650 carbon fabric laminate properties, and those of BMI-5270 for comparison, are presented.

The effect of phenylethynyl terminated imide oligomer molecular weight on the properties of composites

Phenylphosphine oxide-containing poly(arylene ether imide)s, poly(arylene ether quinoxaline)s, poly(arylene ether benzoxazole)s and poly(arylene ether benzothiazole)s were prepared by reacting the appropriate difluoro heterocyclic compound with bis(4-hydroxyphenoxy-4′-phenyl)phenylphosphine oxide. The polymers exhibited glass transition temperatures from 209 to 255°C and inherent viscosities from 0.35 to 1.34 dl g−1. Thin-film tensile properties measured at room temperature and 177°C exhibited tensile strengths of 10.2–15.8 and 6.0–9.0 ksi (∼ 70.3–108.9 and ∼ 41.4–62.1 MPa), respectively, and tensile moduli of 340–381 and 204–365 ksi (∼ 2.34–2.63 and ∼ 1.41–2.52 GPa), respectively. Unoriented thin films of these phenylphosphine oxide-containing polymers were subsequently exposed to a radiofrequency-generated oxygen plasma under vacuum along with Kapton® HN. To assess the resistance of the materials to the oxygen plasma, the weight losses of the films were monitored as a function of exposure time. Phenylphosphine oxide-containing poly(arylene ether benzoxazole)s and poly(arylene ether benzothiazole)s exhibited weight-loss rates that were 38–190 (1–2 orders of magnitude) times slower than that of Kapton® HN. Phenylphosphine oxide-containing poly(arylene ether quinoxaline)s exhibited weight-loss rates only slightly slower (1–7 times) than those of Kapton® HN. The changes in surface chemistry of the exposed films were subsequently examined using X-ray photoelectron spectroscopy. In most cases, the phosphorus and oxygen near the surface exhibited increases in relative concentration and the photopeaks shifted towards higher binding energies. These changes are indicative of the formation of phosphate-type species. In addition, their limiting oxygen indices were calculated from char yields at 850°C in nitrogen utilizing a reported method. For the most part, the incorporation of phenylphosphine oxide groups did not substantially increase the limiting oxygen indices.

Imide oligomers containing pendent and terminal phenylethynyl groups

Dynamic mechanical analysis was performed on a series of the isomeric polyimides (PIs) made from the reaction of s-, a-, and i-BPDA each with 4,4′-ODA, 3,3′-ODA, 1,3,3-APB and 1,4,4-APB. The glass transitions (T g s) moved towards higher temperatures in the order of s-, a-, and i-BPDA for the para diamine-based PIs whereas the T g values showed little change for meta diamine-based PI regardless of the BPDA isomer. Conversely, the temperature of the β relaxation process increased in the order of i-, a-, and s-BPDA with any diamine. These behaviors can be interpreted in terms of the steric hindrance effects due to the configuration of BPDA isomers and diamines.