Novel Interecting Blends Based on Amino Terminited Oligoimides by Using Michael Addition Reaction-II

New amino terminated oligoimides (AOIs) were prepared by the Michael addition reaction of various bismaleimide (1), namely, 1-(4-((4-((2, 5-dioxocyclopent-3 enylamino) methyl) cyclohexyl) methyl) cyclohexyl)-1, 6-dihydropyridine-2, 5-dione with excess of various diamines (2a-c). These AOIs were characterized by elemental analysis, FT-IR spectral studies and number average molecular weight estimated by non-aqueous conductometric titrations. AOIs were then treated with acrylol chloride and resultant acryl terminated oligoimides (AcOIs) samples were also characterized thermogravimetrically. Each of these AcOI was then combined with the N-phenyl maleimide (PM) in THF solvent. The resultant suspensions were then heated in the presence of azobisisobutyronitrile (AIBN) as an initiator. The AcOI and PM polymerized through double bond simultaneously and form interacting blends, which were analyzed thermogravimetrically. The glass fiber reinforced composites were fabricated by using the suspensions of the AcOI and PM. The composites of Interacting blends were analyzed for their mechanical, chemical and electrical properties.


Introduction
The polyimides as high performance polymers are well established 1 .Applications ranging from aerospace to microelectronics have utilized the outstanding thermo-oxidative stability of these polymers.Recently, the interest has accelerated in tailoring chemistry of polyimide So as to approach the optimum balance of properties required for ease of processing.Many aspects of research pertinent to various polyimides have been well documented [2][3][4][5][6][7][8] .
Such approach can be received by interacting of thermoplasts i.e. acryl terminated oligoimides (AOIs) with thermosets i.e. poly N-phenyl maleimide.Such type of study has not been reported so far.Though the styrene-N-phenyl maleimide (SPM) copolymers are reported for many applications [9][10][11][12][13][14] .So, the initial work has been carried out by present authors 15 .Thus in continuation of this work the present paper comprises the initial work about such interacting blends, scanned in Scheme 1.

Materials and Methods
N-Phenyl maleimide, 1, 4-xylylene bismaleimide and diamines (2a-c) were used of A.R.grade.The diamine used for the synthesis of bismaleimides.Plain weave fibers, in the form of E-glass woven fabric (polyimide compatible) 0.25 mm thick (Unnati Chemicals, India) of a real weight 270 g/m 2 were used for composite fabrication.All the other chemicals used were of the laboratory grade.

Synthesis of Amino Terminated Oligoimides
The amino terminated oligoimides (AOIs) were prepared by the Michael addition reaction between the bismaleimide and diamine (2a-c) at the molar ratio of 1:2.They were prepared according to the method reported 18 .All the three AOIs were designated as (3a-c).

Synthesis of Acryl End Capped Oligoimides
To a suspension of AOIs (3a-c) (0.05 mol) in THF (100 mL), acrylol chloride (0.05 mol) was added drop wise at room temperature.Then equivalent amount of K 2 CO 3 was added to neutralize the resulting HCI.The resultant acryl end capped oligoimides (AcOIs) were obtained in the form of yellow amorphous powder.All the three AcOIs were designated as (4a-c).

Synthesis of Interacting Blends of AOI-N-phenyl maleimide (PM)
Each of the AcOIs (4a-c) sample and N-phenyl maleimide (PM) with various weight percentages were prepared and shown in Table 1.To one of these mixture, AIBN was added as an initiator and then the mixture was heated at 80°C for 2 h and then at 200°C for 1 h.The resulted cross linked of polyimide and was in the form of solid hard material.They were designated as (5a-c).Thus the nine systems of interacting blends of polyimides of were prepared.

Composite Fabrication
The composites were prepared from a typical method of composite fabrication is given below.Three ratios of AcOI to N-phenylmaleimide solution as shown in the below Table 1.A suspension of acryl end capped oligoimide (AcOI Scheme 1) and thermoset Nphenylmaleimide solution was prepared in tetrahydrofuran was prepared and stirred for 5 min.To this, AIBN was added as an initiator and was stirred well for few minutes.The suspension was then applied with a brush on a 150 mm x 150 mm glass cloth.The 10 dried prepreges prepared by these way were then stacked one on top of another and pressed between the steel plates coated with a Teflon film release sheet and compressed in a flat platen under 70 psi (0.4 MPa) pressure the prepreges stacks were cured by heating at 150°C for 10 h.In an air circulated oven.The composite so obtained was cooled to 50°C before the pressure was released.The specimens were made by cutting the composites and machining them to final dimensions.The C, H, N contents of all the amino terminated oligoimides (AOIs) (3a-c) and acryl end capped oligoimides (AcOIs) (4a-c) were estimated.Their results are furnished respectively, in Tables 2 and 3. IR spectra of AOIs and AcOIs were taken in KBr pellets using KBr as a reference on a Nicolet Impact 7600 D spectrophotometer.
The number average molecular weights of the AOIs (3a-c) were determined by the nonaqueous conductometric titration following the method reported in the literature 19,20 .Formic acid-acetic acid mixture was used as the solvent and standard perchloric acid in acetic acid was used as a titration.A digital conductivity meter (Tosaniwal, India) was used for the titration.Their results are furnished in Table 2. AcOIs (3a-c) were also analyzed for their number of double bonds per repeating unit employing mercury catalyzed bromate-bromide titration method 21 .The AOIs (3a-c) and AcOIs (4a-c) were also characterized thermo gravimetrically on a Du Pont 990 Thermal analyzer MK-III.Their results are furnished in Tables 2 and 3, respectively.Interacting blend Polyimide samples were subjected to thermo gravimetric analysis (TGA) on a Du Pont 990-thermal analyzer MK-III in air at a heating rate of 10°C min-I.The TGA data are furnished in Table 5.They were also subjected to the Differential thermal analysis to get their glass transition temperature.Their results are furnished in Table 4.

Composite Characterization Chemical Resistance Test
The chemical resistant test for the entire composite sample was performed according to ASTM D 543Y67.The composite sample dimensions were 25 x 25 x 3 mm.The samples were immersed in 25% v/v H 2 SO 4 , 25% v/v HCl 25% w/v NaOH, Ethanol, Acetone, DMF and THF for seven days at room temperature.After seven days the samples were taken out from the reagents and were analyzed for their percentage change in their thickness and weight.Their results are summarized in Table 5.

Mechanical Test
All the mechanical and electrical tests were performed using three specimens and their average results are summarized in Table 6.The measurement of dielectric strength was carried out on a high voltage tester machine oil test set.
The compressive strength was measured on a Universal Instron testing machine model no.A-74-37, at the room temperature according to ASTM D 695.The notched izod impact strength of the composites was measured on a Zwick Model no.8900 Impact machine at the room temperature according to ASTM D256.Rockwell Hardness was measured on a Rockwell hardness tester model no.RAS/Saro Engg.Pvt. Ltd.India according to ASTM D 785 at room temperature.The measurement of Flexural strength was carried out with Universal Instron Testing Machine model no.A-74-37, at room temperature according to method of ASTM D790.

Results and Discussion
The syntheses of (AOIs) (3a-c) were performed by the reported method 18 .The oligoimides produced are in the form of orange powder.They were insoluble in organic solvents.The C, H and N contents Table 2 of all the oligoimides (3a-c) are consistent with their predicted structures (Scheme 1).Their results are furnished in Table 3.All the three oligoimides react to the red azo dye test, thereby confirming, and the presence of the terminal primary amino group.Examination of the IR Spectra (not shown) of the AOIs (3a-c) reveals that each spectrum comprises the strong bands around 1,700, 1,650, 1,050 and 730 cm -1 due to the presence of imide group 22 .The broad band around 3,300 cm -1 is attributed to -NH bonds.The inflections at 3,500 and 3,400 cm -1 may arise from terminal NH 2 groups.The medium bands at 2,950 and 2,840 cm are attributed to the C-H of the CO-CH 2 -CH 2 group present in the polymer chain.The band of around 1500-1600 cm -1 shows the presence of azo group in 3c, 4c and 5c compound.The absence of the band at 3,040 cm -1 (attributed to the double bond present in AOIs) indicated that the Michael addition polymerization of the bismaleimides and DDM.The number average molecular weights (Mn) of the AOIs (3a-c) are furnished in Table 2.
TGA data (not shown) of the AOIs (3a-c) are given in Table 3. Examination of the TGA data of AOIs reveals that the oligoimides begin to decompose at around 170 °C and loss almost 95% at around 700°C.The amino terminated oligoimides AOIs (3a-c) were then reacted with acrylol chloride to give acryl end-capped oligoimides (AcOIs) (4a-c).The C, Hand N contents of all the AcOIs (4a-c) are consistent with their predicted structures (Scheme 1) (Table 3).The presence of double bonds in AcOIs (4a-c) are confirmed by the bromated bromide titration method 21 (Table 3).
The examination of the IR spectra of all AcOIs samples reveals that all the spectra are almost resemble to the spectra of corresponding AOIs samples only discern ible difference is that the spectra of AcOIs contain the new band at 1,550 cm -1 of amide group instead of bands at 3,500 and 3,400 cm -1 to primary NH 2 group appeared in the spectra of AOIs.This confirms the acrylation reaction of amino terminated oligoemide.Examination of the TGA (Figure not shown) data (Table 3) reveals that the AcOIs (4a-c) starts their degradation around 180°C and loss 90% around 750°C.The AcOIs (4a-c) were mixed with a thermoplastic pyromellatic N-phenylmeleimide (PM) solution in different proportions.To this mixture AIBN was added as an initiator and then the mixture was heated at an elevated temperature.This create cross-linking reaction of AcOI as well as polyimide formation of N-phenylmeleimide, thus interacting blends were produced.The IR spectrum of IB is not obtained in well resolved form.While the spectrum comprises the bands due to imide group.The schematic diagram of such a system is shown in Scheme 1.
The Glass fibre reinforced composites were fabricated of this interacting blend of the polyimides of various proportions as in Table 1.These composites were analyzed for their chemical, mechanical and electrical properties.Examination of the data (Table 5) reveals that they have good resistance to common organic solvents like acetone, ethanol etc.They also have good mechanical strength.The electrical strength of these composites is between 15 to 16.5 kV/mm.Their results are furnished in Table 6.Because many factors such as processing, testing, reinforcement, environment, and quality are known to significantly affect composite performance, it is very difficult if not impossible, to make a valid comparison of properties on the same material evaluated in different laboratories.In order to make a meaningful comparison of the properties between produced interacting blend those prepared by us these are shown in Table 7.It is evidenced that produced IBs have better mechanical properties and maintaining relatively easy processability.All of the raw materials necessary for the preparation of interacting blend are commercially available.Table 7. Composite properties of Intrecting blend (5a-c) compared with Interacting blend of Thermid 600 and NR150B2 constituent material 18 .

Conclusion
The produced work indicates that synthesis of thermoset amino terminated oligoimide is easy.The synthesis of acryl end capped oligoimides and their polymerization are easy.The formation of new interecting blend polyimides system via acryl end capped oligoimide and poly N-phenylmeleimide is feasible.The resultant interecting blend product has comparable properties with other of commercial polymer.The processing temperature is not much more than conventional polyimide composites.The glass reinforced composites could be prepared with good mechanical.

Table 1
Various weight percentages.

Table 5 .
Chemical resistance tests of Interacting blends.

Table 6 .
Mechanical and electrical properties of interacting blend of polymides Electrical test.