Cyanate ester/aryl ethynyl polyimide resins for composite materials

Abstract

A polymerizable thermoset composition including a polymerizable organic cyanate ester resin and a polymerizable aryl ethynyl-terminated polyimide, a polymerized thermoset, a process for the production of the polymerized thermoset as well as the use of the polymerizable thermoset composition for the production of lightweight construction components, preferably carbon fiber composite materials (CFC), and a lightweight construction component, preferably carbon fiber composite material (CFC), containing the polymerized thermoset are described.

Claims

1. A polymerizable thermoset composition comprising: a) a cross-linkable organic cyanate ester resin; b) a cross-linkable aryl ethynyl-terminated polyimide, and c) at least one allyl compatibilizer comprising at least two functional groups, wherein the functional groups are each independently selected from the group consisting of hydroxides, primary amines, secondary amines, anhydrides, cyanate esters, and epoxides.

2. The polymerizable thermoset composition as claimed in claim 1, wherein the cross-linkable organic cyanate ester resin is a compound of the formula (I): ##STR00027## wherein R represents an alkyl, alkenyl or aryl group.

3. The polymerizable thermoset composition as claimed in claim 1, wherein the cross-linkable organic cyanate ester resin is a compound of the formula (II): ##STR00028## wherein R.sup.1, R.sup.2 and R.sup.3, independently of each other, represent hydrogen or C.sub.1-C.sub.10 alkyl and n represents an integer from 0 to 20.

4. The polymerizable thermoset composition as claimed in claim 1, wherein the cross-linkable aryl ethynyl-terminated polyimide is a compound of the formula (III): ##STR00029## wherein Ar represents an intermediate segment which is selected from the group consisting of ##STR00030## R.sup.4 represents a group selected from the group consisting of ##STR00031## R.sup.5 represents a group selected from the group consisting of ##STR00032## wherein X represents a group selected from the group consisting of O, S, S(O.sub.2), C(O), C(CH.sub.3).sub.2, C(CF.sub.3).sub.2, CH.sub.2, 3-oxyphenoxy, 4-oxyphenoxy, 4-oxy-4-biphenoxy and 4-[1-(4-oxyphenyl)-1-methylethyl]-phenoxy, and m represents an integer from 1 to 40.

5. The polymerizable thermoset composition as claimed in claim 1, wherein the polymerizable thermoset composition contains the cross-linkable organic cyanate ester resin and the cross-linkable aryl ethynyl-terminated polyimide in a ratio by weight (wt/wt) of 200:10 to 20:10.

6. The polymerizable thermoset composition as claimed in claim 1, wherein the at least one allyl compatibilizer is a compound of the formula (IV): ##STR00033## wherein R.sup.6 represents a group selected from the group consisting of O, S, S(O).sub.2, C(O), C(CH.sub.3).sub.2, C(CF.sub.3).sub.2, CH.sub.2, 3-oxyphenoxy, 4-oxyphenoxy, 4-oxy-4-biphenoxy and 4-[1-(4-oxyphenyl)-1-methylethyl]-phenoxy; and Y each independently represents a functional group selected from the group consisting of hydroxides, primary amines, secondary amines, anhydrides, cyanate esters, and epoxides.

7. The polymerizable thermoset composition as claimed in claim 1, wherein the cross-linkable organic cyanate ester resin and the cross-linkable aryl ethynyl-terminated polyimide react through the at least one allyl compatibilizer with the formation of a covalently bonded interpenetrating polymeric system.

8. The polymerizable thermoset composition as claimed in claim 1, wherein the polymerizable thermoset composition contains the cross-linkable organic cyanate ester resin and the cross-linkable aryl ethynyl-terminated polyimide and the at least one allyl compatibilizer in a ratio by weight (wt/wt/wt) of 150:6:1 to 5:2:1.

9. A polymerized thermoset which is a reaction product of the polymerizable thermoset composition as claimed in claim 1.

10. A process for the production of a polymerized thermoset, comprising the following steps: i) providing the polymerizable thermoset composition as described in claim 1; and ii) polymerizing the polymerizable thermoset composition from step i) at a temperature in the range 100 C. to 330 C.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 shows a mDSC spectrum of the first heating cycle (curing) of an uncured thermoset blend consisting of Primaset PT15/PETI330 [ratio approximately 5:1].

(2) FIG. 2 shows a mDSC spectrum of the second heating cycle (post-curing) of a thermoset blend consisting of Primaset PT15/PETI330 [ratio approximately 5:1] cured at 240 C. for 2.5 h.

(3) FIG. 3 shows a DMTA spectrum of a thermoset blend consisting of Primaset PT15/PETI330 [ratio approximately 5:1] cured at 300 C. for 3.5 h. Heating rate: 3K/min, Frequency: 1 Hz, Deformation: 0.05%.

(4) FIG. 4 shows a mDSC spectrum of the first heating cycle (curing) of an uncured thermoset blend consisting of Primaset PT15/PETI330/DABPA [ratio approximately 100:20:5].

(5) FIG. 5 shows a mDSC spectrum of the second heating cycle (post-curing) of a blend consisting of Primaset PT15/PETI330/DABPA [ratio approximately 100:20:5] cured at 240 C. for 2.5 h.

(6) FIG. 6 shows a mDSC spectrum of the second heating cycle (post-curing) of a blend consisting of Primaset PT15/PETI330 (circle) and Primaset PT15/PETI330/DABPA (square) cured at 240 C. for 2.5 h.

(7) FIG. 7 shows a DMTA spectrum of a blend consisting of Primaset PT15/PETI330/DABPA [ratio approximately 100:20:5] cured at 300 C. for 3.5 h. Heating rate: 3K/min, Frequency: 1 Hz, Deformation: 0.05%.

(8) The invention will now be illustrated with the aid of the accompanying examples:

EXAMPLES

1. Methods

(9) a) DSC Measurements

(10) DSC measurements were prepared with the aid of the instrument known as the DSC Q2000 from TA Instruments in a nitrogen atmosphere. The spectra were recorded with the aid of the software Thermal Advantage Release 5.4.0 and analysed using the software Universal Analysis 2000, Version 4.5A from TA Instruments. The heating rate was 5 IC/min, with a temperature of 20 C. to 400 C.

(11) b) TGA Measurements

(12) TGA measurements were prepared with the aid of the instrument known as the TGA Q5000 from TA Instruments. The spectra were recorded with the aid of the software Thermal Advantage Release 5.4.0 and analysed with the software Universal Analysis 2000, Version 4.5A from TA Instruments. The heating rate was 10 IC/min, with a temperature of 20 C. to 1000 C. The measurements were carried out in an oxygen atmosphere (ambient air).

(13) c) DMTA Measurements

(14) Dynamic mechanical thermoanalyses (DMTA) were carried out with the aid of the Advanced Rheometric Expansion System (ARES) rheometer from Rheometric Scientific. The Software Rheometric Scientific, Version V 6.5.8 was used for the analysis. The heating rates were 3 K/min in all cases. The glass transition temperature T.sub.g corresponded to the maximum of the tan() function and the onset temperature corresponded to the loss of the storage modulus G by application of the tangent method.

(15) d) FT-IR Characterization

(16) The materials were characterized by means of FT-IR investigations. The spectra were recorded with the aid of the Nicolet iN10 FT-IR microscope from Thermo Scientific. The measurements were carried out with the aid of an ATR crystal in the frequency range of 500 cm.sup.1 to 4000 cm.sup.1, with 64 scans being recorded per measurement. The optical microscope had a resolution of 25 m25 m; the FT-IR spectrum was recorded with a resolution of 8 cm.sup.1. The program Omnic 8.1.0.10 from Thermo Scientific was used to analyse the spectra.

(17) e) Fracture Toughness K.sub.IC

(18) K.sub.IC measurements were made with the aid of theBT-FR2.5TH.D14 instrument from Zwick/Roell (DE). The tests were carried out at a test speed of 10 mm/min. Testing was carried out in accordance with DIN ISO 13586.

(19) The Software testXpert II V3.1 from Zwick/Roell (DE) was used to analyse the results.

(20) g) Water Absorption Capacity

(21) The water absorption capacity was determined in accordance with DIN EN ISO 62 by placing the test samples in distilled water at 70 C. for 2 weeks. The mass of the test specimens was determined before and after placement and the water absorption capacity was determined therefrom as a percentage.

2. Materials Used

(22) Primaset PT15 (available from Lonza) is a cyanate ester resin consisting of oligo (3-methylene-1,5-phenylcyanate).

(23) PETI330 (available from UBE Industries Ltd.) is a polymerizable aryl ethynyl-terminated polyimide with a glass transition temperature T.sub.g of 330 C., determined by DSC (pure resin powder after 1 hour at 371 C. in an aluminium cup at a heating rate of 20 C./min).

(24) DABPA (available from GP Chemicals, Inc.) is 2,2-diallylbisphenol A.

(25) Preparation of Materials

(26) a) Preparation of CE/PETI (Non-Covalent Full IPN)

(27) The cyanate ester resin Primaset PT15 was weighed into a 800 ml beaker and degassed for 1 hour in a vacuum oven at 80 C. Next, the phenyl ethynyl polyimide PETI330 was mixed with the hot cyanate ester in a Speedmixer rotating at a speed of 1350 min.sup.1 and at a pressure of 100 mbar and degassed in a vacuum oven at 80 C. for 2 hours and at 110 C. for 1.5 hours. Next, the hot reaction mixture was poured into a mould pre-heated to 150 C. and underwent the following curing cycle in a convection oven:

(28) 1. 150 C..fwdarw.200 C. Heating rate: 2K/min

(29) 2. 200 C. 4 h isothermal

(30) 3. 200 C..fwdarw.250 C. Heating rate: 2K/min

(31) 4. 250 C. 2.5 h isothermal

(32) 5. 250 C..fwdarw.300 C. Heating rate: 2K/min

(33) 6. 300 C. 3.5 h isothermal

(34) Cross-linking of the two separate thermosetting systems was recorded and characterized with the aid of modulated dynamic differential calorimetry (mDSC). FIGS. 1 and 2 show the mDSC measurement for a Primaset PT15/PETI330 blend (ratio of approximately 5:1). The homogeneous cross-linking of the cyanate ester began at a temperature of 178 C. and showed the maximum enthalpy at 186 C. After the pure resin panels had been cured at a temperature of 175 C., the material obtained was then examined again using MDSC. In the second heating cycle (FIG. 2), a signal was observed which started at a temperature of 295 C. with a maximum enthalpy at 342 C., which could be attributed to the homogeneous cross-linking of the PETI resin.

(35) The thermo-mechanical properties of the Primaset PT15/PETI330 blend were investigated with the aid of DMTA measurements and are summarized in Table 1.

(36) TABLE-US-00001 TABLE 1 Summary of the thermo-mechanical properties of the cured materials from the cyanate ester PrimasetPT15 and the polyimide PETI330. Proportion by weight of PETI330/ T.sub.g.sup.a/ T.sub.d.sup.b/ T.sub.5% weight loss.sup.b/ % by weight C. T.sub.onset.sup.a/ C. C. C. 23 282/334 257/315 423/616 429 17 286/330 256/311 424/612 428 9 283/327 283 424/609 429 5 282/322 278 424/620 430 .sup.aMeasured using DMTA .sup.bMeasured using TGA

(37) An example of a DMTA spectrum of the Primaset PT15/PETI330 blend is shown in FIG. 3. It can be seen here that the tan() function has two maxima. This and also the mDSC measurements lead to the conclusion that two independent matrix systems in the form of a non-covalent full IPN have been formed which are not interconnected, i.e. the cross-linkable organic cyanate ester resin and the cross-linkable aryl ethynyl-terminated polyimide are respectively in the form of non-covalently bonded interpenetrating polymeric systems.

(38) b) Preparation of CE/PETI/DABPA Sequential IPN

(39) The cyanate ester resin Primaset PT15 was weighed into a 800 ml beaker and degassed for 1 hour in a vacuum oven at 80 C. Next, the phenyl ethynyl-polyimide PETI330 and the compatibilizer DABPA were mixed with the hot cyanate ester resin in a Speedmixer rotating at a speed of 1350 min.sup.1 and at a pressure of 100 mbar. Mixing was carried out at 80 C. for 1.5 hours in a vacuum oven, poured into a mould preheated to 130 C. and the following curing cycle was carried out:

(40) 1. 130 C..fwdarw.165 C.

(41) 2. 165 C. 4 h isothermal

(42) 3. 165 C..fwdarw.240 C., heating rate: 2K/min

(43) 4. 240 C. 2.5 h isothermal

(44) 5. 240 C..fwdarw.300 C., heating rate: 2K/min

(45) 6. 300 C. 3.5 h isothermal

(46) Cross-linking of the two thermosetting systems with the aid of the compatibilizer DABPA was characterized with the aid of mDSC measurements. FIGS. 4 and 5 show the mDSC measurement of a Primaset PT15/PETI330/DABPA blend (ratio approximately 100:20:5) by way of example. Cross-linking of the cyanate ester, catalysed by the hydroxide function of the DABPA, started at a temperature of 130 C. and had a maximum enthalpy at a temperature of 235 C. (FIG. 4). Furthermore, a signal was observed in the mDSC spectrum which started at 325 C. with a maximum enthalpy at 367 C., indicating a second exothermic reaction. After the pure resin panels had been cured at a temperature of 165 C., the material obtained was examined again using mDSC (FIG. 5). In the second heating cycle, an exothermic reaction was observed beginning at a temperature of 260 C. with a maximum enthalpy at 290 C. which can be attributed to the reaction of the terminal phenyl ethynyl group of the PETI330 and the allyl function of the compatibilizer DABPA. This took place at a lower temperature in comparison to the homogeneous cross-linking of the PETI330 resin.

(47) FIG. 6 shows the mDSC spectra of the second heating cycle for the Primaset PT15/PETI330 blend with and without the addition of DABPA, for comparison. It can clearly be seen here that the cross-linking of PETI330 with the aid of the allyl DABPA begins at a temperature which is 30 C. lower than the homogeneous cross-linking of PETI330.

(48) The thermo-mechanical properties of the Primaset PT15/PETI330/DABPA blend were investigated with the aid of DMTA measurements and are summarized in Table 2.

(49) TABLE-US-00002 TABLE 2 Summary of the thermo-mechanical properties of cured materials from PrimasetPT15/PETI330/DABPA. Proportion Proportion by weight by weight of PETI330/ of DABPA/ T.sub.onset.sup.a/ T.sub.5% weight loss.sup.b/ % by weight % by weight T.sub.g.sup.a/ C. C. T.sub.d.sup.b/ C. C. 22 6 307 266 418/606 423 16 4 318 276 417/583 421 8 2 328 284 417/587 421 4 0.95 315 281 417/590 422 .sup.aMeasured using DMTA .sup.bMeasured using TGA

(50) FIG. 7 shows, by way of example, a DMTA spectrum of the material consisting of Primaset PT15/PETI330/DABPA (ratio of approximately 100:20:5). It can be seen here that after curing the material at 300 C., the material has only one T.sub.g and one T.sub.onset which is different from that of the T.sub.g and the T.sub.onset of the Primaset PT15/PETI330 non-covalent full IPN (see Table 1 and Table 2). All of the materials prepared (see Table 2) have only one T.sub.onset and one T.sub.g in the DMTA spectrum, which indicates the formation of a homogeneous network.

(51) This and the results of the mDSC measurements mean that the conclusion can be drawn that by adding the allyl compatibilizer DABPA, the triazine network, starting from the cyanate ester Primaset PT15 and the polyimide network starting from PETI330 can be covalently linked together to result in a sequential IPN; i.e. the cross-linkable organic cyanate ester resin and the cross-linkable aryl ethynyl-terminated polyimide react via the at least one allyl compatibilizer with the formation of a covalently bonded interpenetrating polymeric system.

(52) While at least one exemplary embodiment of the present invention(s) is disclosed herein, it should be understood that modifications, substitutions and alternatives may be apparent to one of ordinary skill in the art and can be made without departing from the scope of this disclosure. This disclosure is intended to cover any adaptations or variations of the exemplary embodiment(s). In addition, in this disclosure, the terms comprise or comprising do not exclude other elements or steps, the terms a or one do not exclude a plural number, and the term or means either or both. Furthermore, characteristics or steps which have been described may also be used in combination with other characteristics or steps and in any order unless the disclosure or context suggests otherwise. This disclosure hereby incorporates by reference the complete disclosure of any patent or application from which it claims benefit or priority.