Crystallization of oligomeric systems based on polytetramethylene oxide

2176

L. I. MAKLAKOVand I. N. DEMENT'EVA

15. V. P. PU'KH, Prochnost i razTushenie stekla (Strength and Fracture of Glass). Leingrad, 1973

16. G. P. CHEREPANOV, Mekhanika khrupkogo razrusheniya (Mechanics of Brittle Fracture). Moscow, 1974 17. G. M. BARTENEV, Izv. Akad. Nauk SSSR, Otd. Khlm. Nauk, 9, 53, 1955 18. M. I. BESSONOV and Ye. V. KUVSHINSKrl, Fiz. tverd, tela 3: 1315, 1961 19. Y. IMAI and N. BROWN, J. Polymer Sci. Polymer Phys. Ed. 14: 723, 1976 20. M. F. MILAGIN and N. I. SHISHKIN, Mekhamka pohmerov, 1, 8, 1976 21. M. F. MILAGIN and N. L SHISHKIN, Problemy prochnosti, 1, 106, 1981

Polymer Scmnce U.S.S.R. Vnl. 29. No. 9. pp. 2i76-2182, 1987 Printed in Poland

0032-3950/87 $I0 00+.00 1988 Pergamon Preu pie

CRYSTALLIZATION OF OLIGOMERIC SYSTEMS BASED O N POLYTETRAMETHYLENEOXIDE* L. I. MAKLAKOVand I. N. DEMENT'EVA Kazan Institute of Construction Engineering

(Received 18 April 1986) Crystallization of reactive and model urethane oligomerie systems based on polytetramethyleneoxide, and the character of hydrogen bonds formed in this process, were studmd by vibrational spectroscopy, X-ray diffraction and DTA. Crystallization kinetms was described by the Avrarnl equation, and conclusions concerning nucleation and growth of crystalline structures could be reached. RECENTLY a number of reactive ohgomers have been studied, containing urethane groups in their end fragments [1, 2]. The urethane containing polymers prepared from these oligomers exhibtt better physico-mechanical properties than the corresponding polymers without urethane fragments. In the present work, urethane containing oligomers were studied, prepared on the basis of polytetramethyleneoxide [(CHz)40]~-(PTMO), of the following geneial structul e: R--OCONH--~

i--H NOCO--(PTM O)--OCONH--'~ ~ , --HNOCO--R CHa

In cases where R = - C H 2 - C H - C H 2 ,

CH3 the oligomer is reactive (PTMOE); when

O R = - C H a , we have an umeactive model oligomer (PTMOM), suitable for high tern* Vysokomol. soyed A29: No. 9, 1981-1985, 1987.

Crystalhzation of oligomen¢ systems based on polytetramethyleneox~de

2177

perature experiments, as chemical crosslinking cannot occur. Besides the pure oligomers, also their mixtures with the corresponding dmrethanes were studmd (the radical R was the same m the mixture) R--O CO NH---~"~--H NOCO--R, CHa where R = - C H 3 (TMU) or an epoxlde radical (TGU); these can be formed spontaneously during ohgomer synthesis, or they can be prepared on purpose for regulating the properties of cured systems. The propemes of the pure dmrethanes were studmd m

[3, 4]. We have studied oligomer mixtures wroth ohgomer : diurethane mole ratzos 1 : 1, 2 and I : 3. A reactsve mixtures will be designated as PTMOE-n, and a model mixture as PTMOM-n, where n indicates the number of diurethane molecules per one molecule of ohgomer. The method of synthesis of the studied" PTMO ohgomers with hydroxyl end groups and M = 1038 was analogous to the method of preparing urethane liquid rubbers [4]; the chemical purity and characterssttcs of the initial compounds are g~ven in the same refezence. It is well known that under normal conditions PTMO is a crystalline compound whose structure has been studied in detail [5]. Therefore it is interesting to mvemgate how the crystalhzing abd~ty of the oligomers, the generated structure and the process kinetics are affected by the attachment of the urethane and fragments Also the behavlour of oligomer mixtures with the corresponding dlurethanes is nonmwal, as the latter themselves crystallize well when in the pure state. Moreover, in the study of liquid urethane rubbers [4] it was shown that m s~milar m~xed systems, cocrystalhzation of diurethane molecules with the urethane end fragments of the oligomer may occur. DTA and X-ray &ffraction studies of ohgomeric systems have shown that under certain conditions they can occur in the crystalline state. The ohgorners and their m~xtures were crystallized to 0 °, after heating for 30 rain to a temperature I0 ° above their melting point. DTA curves exhiNt well pronounced endothermlc melting peaks. The following melting temperatures were found for the studied objects: PTMO 29; P T M O M 22; P T M O E 21; PTMOM-1 18 and 130; PTMOM-3 17 and 132; PTMOE-1 19; PTMOE-3 18; T M U 168 and T G U 83 °, It can be seen that the melting temperature of the PTMO block is lowered by the attachment of urethane end fragments. Beyond that, a second peak appears m model oligomenc systems, atmbuted to the melting of crystalline domains including the diurethane molecules of the mixture. The melting temperature of these domains is lower than that of pure diurethane. The crystalline structure of the studied systems is also confirmed by X-ray diffraction data. The X-ray dmgrams exhibit clearly pronounced peaks at 0=9048 ' and 12°Y, characteristic of crystalline PTMO. The mixed model systems PTMOM-n are characterized by peaks connected with the structure of crystalline diurethane. However, the diagrams are not a more superpomion of PTMO and diurethane patterns. This is demon1 :

2178

L.I. MAKLAKOVand I. N DE~mrrr'Ev^

strated in Fig. 1, showing the X-ray diagrams of PTMO, dmrethane and of the mixture P T M O M - 3 prepared by crystallization from the melt, and also mixed at r o o m temperature without altering the phase structure of the components. It can be seen that the relative intensities differ considerably in these mixtures; the X-ray diagram of the m~xture prepared without any thermal treatment corresponds to a superposition of P T M O and diurethane patterns.

74

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,

FIG 1 Fro. 2 FIG. 1. X-ray diffraction diagrams of PTMO (1), PTMOM-3 (2), thermally untreated PTMOM-3 (3) and TMU (4). FIG. 2. X-ray diffraction diagrams of PTMO (1), PTMOE (2), PTMOE-I (3), PTMOE-3 (4) and TGU (5). The situation is dtfferent with the reactive oligomeric systems PTMOE-n; theft diagrams clearly exhibit (Fig, 2) reflections of the P T M O block, plus an additional peak at 0 = 10°15', while diure thane reflections are absent at all studied mixture compositions. Thus in PTMOE-n systems, crystalline domains containing diurethane molecules do not exist; this Is also confirmed by the absence of the corresponding melting peaks on D T A curves. The appearance of the additional peak at 10°15 ' indicates that the crystalline structure of the urethane containing ohgomer and of the mixtures ~s not fully

Crystalhzatlon of oligomeric systems based on polytetramethyleneoxlde

2179

1

35

33

18

16

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FIG 3 IR spectra of P T M O (1), PTMOM-1 (2), P T M O M - 3 (3) crystalhzed at 0 ° for 10 days, and of crystalhne T M U (4)

tdentlcal x~lth the P T M O structure, even while it preserves its basic features as indicated by I R data IR spectra of amorphous and crystalline P T M O have been well studied [5]. The bands at 566, 745. 1000 and 1490 c m - t were found to be characteristic of crystalline P T M O The presence of these bands in the spectrum is indicative of the presence of the crystalhne phase in the sample. The I R spectra of P T M O M and PTMOE, and of their mixtures with the corresponding diurethanes, crystallized at 0 ° from the melt, exhibit these bands It can therefore be concluded that under these conditions the P T M O block ~s m a crystalhne state whose structure is identical with that of the pure ohgomer_ Thus the attactunent of urethane fragments to P T M O ohgomeric molecules does not interfere with the developing crystalline structure of the latter. A study of the N H and C = O group stretching vibrations can provtde information on the behavlour of the urethane part (urethane ends of ohgomerlc molecules and dlurethane molecules) of the oligomeric systems. At first let us discuss the model oligometic systems PTMOM-n. In [4] it was shown that the band at 3265 c m - 1 is characteristic of the crystalline state of T M U , and the band at 3340 c m - t is attributed to the melt. The I R spectrum of the P T M O M oligomer (Fig. 3) only exhibits a band at 3315 c m - 1, and a very weak one at 3450 c m - t assigned to free N H group wbrations. The mixtures exhibit bands at 3270 and 3315 cm -~ The occurrence of the band at 3270 c m - ~ comcidmg with the band of crystalhne T M U , indicates the presence of crystalline structures wtth hydrogen bonded urethane groups. Evidently such structures are formed both by low-molecular weight dlmethane molecules, and by the urethane end fragments of ohgomenc molecules. The melting of these structures is also observed on D T A curves about 130 °. The ',econd band, at 3315 c m - ~ , m the I R spectrum of mixtures differs by its position from the band observed in T M U

2180

L. I. M A K L A K O V and I. N. DESm~rr'EVA

melt, and it is connected with hydrogen bonding of N H groups to the ether oxygen of the P T M O block. This is supported by an inspection of the range of the C = O stretching vibrations. The spectra (Fig. 3) exhibit a pronounced band at 1740 c m - 1 assigned to free (not hydrogen bonded) C = O groups. As there are only very few free N H groups in the system (the band at 3450 c m - 1 is very weak), it is evident that they must be bound with the ether oxygens of the P T M O block. It should be noted that the doublet at 1690, 1720 cm -~ characteristic of crystalline T M U , together with the band at 3270 cm -1, confirm the presence of crystalline urethane domains m the studied mixed systems. VALUES OF THE I N D U C T I O N PERIODS T, OF CRYSTALLIZATION HALF-TIMES t~r, OF THE OVERALL C R Y S T A L L I Z A T I O N RATE k A N D OF THE A V R A M I PARAMETER g FOR OLIGOMERIC

SYSTEMSPTMOM-n AND PTMOE-n Systems PTMOM PTMOM-1 PTMOM-3 PTMOE PTMOE-I PTMOE-3

z x 10 -4, sec t~ x 10 -5, sec m 0 43 0"86 0'86 2- 60 1'6 0"86 1'70 1"40 3'20 26 0

3-4x 9.4x 1.7x 9.4x 3.6x 6-3x

k " 10 -1° 10-11 10-ae 10-xl 10-aL 10-23

z 2 2 3 2 2 4

In the case of the reactive oligomer and of its mixtures, bands connected with the crystalline domains of the urethane component are absent. The spectra only exhibit the band at 3315 cm -1 ( N H . . . O ~ ) and a very weak band of free N H groups. Thus in this case crystalline domains containing the urethane component of the system are not formed; this is also indicated by the absence of the corresponding melting peaks on D T A curves and by X-ray diffraction data. Let us now discuss the crystallization kinetics of the basic P T M O block with attached dimethylurethane or epoxyurethane end fragments, and also with the addition of low molecular weight diurethanes of the same kind as the end fragments. Crystallization kinetics was studied by the measurement of the optical density of the band at 745 c m - 1 ; this band was considered proportional to the content of crystalline phase. To account for the thicknes of the sample, the intensity of this band was referred to that of the band at 770 c m - 1 serving as internal standard. The results for the reactive systems PTMOE-n are shown in Fig. 4. The curves for the model systems are similar. The initial P T M O is crystallized within several minutes, i.e. so quickly that a reliable kinetic curve could not be recorded by I R spectroscopy in our conditions. As seen f r o m the Table, the attachment of urethane fragments considerably prolongs the crystallization time; crystallization is completed within 2-3 days. The introduction of a lowmolecular weight diurethane increases the crystallization time of the P T M O block in the system, as well as the induction period of crystallization. The reason of this is seen in the generation of considerable intermolecular interactions in the studied oligomeric systems, between the end fragments, diurethane molecules and the oligomer basic chain.

Crystallization of oligomenc systems based on polytetramethyleneoxide

2181

The measured time dependences of the relative intensity of the band at 745 c m - t were recalculated in Avramt coordinates and are presented in F]g. 5. It can be seen that within certain limits these dependences are hnear. At long times, however, deviations from hnearity are observed; this is caused by the comphcated character of the systems and evidently also by the effect of the urethane component. The values of the Avrami parameter z, shown m the Table, were calculated from the slope of the linear portions

D re[

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FIG. 5 FIG 4 Time dependence of relative optical density of the band at 745 cm- ~ for PTMOE (1),

PTMOE-1 (2) and PTMOE-3 (3) crystalhzed at 0° FIG 5 Plots of l n [ - I n ( l - x ) ] vs. In t for PTMOM (1), PTMOM-1 (2), PTMOM-3 (3), PTMOE (4), PTMOE-1 (5) and PTMOE-3 (6) of the dependences. For pure PTMO, z = 3 was found [6]. For the oligomers P T M O M and PTMOE, i.e. by attachment of urethane end fragments, the Avrami parameter decreases to z = 2. If in the case of PTMO three-dimensional crystal growth is assumed [6], then in our case growth is probably two-dimensional; this can be explained by the blocking of growth in the third dimension by the urethane end fragments, unable to cocrystalhze with the main block into a single crystalline system, Addition of a small amount of diurethane of the oligomer leaves the Avrami p.arameter z unchanged, equal to two; with larger additions the parameter changes, but in view of the complexluy of the resulting system, and also because of the formation of a second crystalhne phase m PTMOM-n, an interpretation of this effect can hardly be presented. The authors wish to thank A. G. Smaiskll and T. S. Teteruk for kindly making avadable the samples studied m this work. Translated by D. DOSKO{~ILOV/~

REFERENCES

I A.A. BERLIN and N. G. MATVEYEVA, Uspekhi khimil nfizlkn pollmerov (Advances in Polymer Chemistry and Physics). p. 252, Moscow 1970 2. G. N. PETROV, A. Ye. KALAUS and I. B. BELOV, Smteticheskti kauchuk (Synthetic Rubber) (edited by I. V. Garmonova) p. 377, Lemngrad 1983 3. S. V. VLADIMIROV, L. I. MAKLAKOV, A. G, SINAISKII and S. B. GRASINSKAYA, Zhurn. prikl, spektroskopni 25; 461, 1976

2182

V.M.

LANTSOV et aL

4. S. V. VLADIMIROV, F. R. ARIFULLIN, S. B. GRASINSKAYA, L. I. MAKLAKOV and A. G. SINAISKII, Vysokomol soyed A19: 1713, 1977 (Translated in Polymer Scl U S.S.R 19: 8, 1957, 1977) 5 K. IMADA, H. TADOKORO, A. U M E H A R A and S. M I R A H A S H I , J Chem. Phys 42: 2807, 1965 6. G. S. TRICK and J. M. RYAN, Polymer Preprints 7: 92, 1966

Polymer Science U.S S R- Vol. 29, No 9, pp 2182-2188, 1987 Printed in Poland

0032-3950/87 $10 00+_00 © 1988 Pergamon Press pie

A STUDY OF CROSSLINKING IN EPOXIDEAMINE SYSTEMS BY PULSED NMR SPECTROSCOPY* V. M. LANTSOV,V. F. STROGANOV,L. A. ABDRAKHMANOVA,V. M. MIKHAL'CHUK, G. N. VASIL'EV,Yu. S. ZAITSEVand YE. V. SIDORENKO Ukrainian Plastics Research Institute

(Received 19 April 1986) The process of crosshnk~ng in a polymer prepared from dJphenylolpropane dlglycldyl ether and 1,3-bls-(amlnomethyl)-adamantane was studied by the methods of N M R transversal relaxation, differential mlcrocalorlmetry and 1R spectroscopy. In native samples a group of slowly relaxing protons was observed, wzth a glass temperature higher by 20 K than T~ of the polymer cured to the limit. The temperature of mobility melting in structural elements in native and post-cured polymer samples falls with an increase in the temperature of isothermle curing.

IT has been known [1, 2] that the curing of epoxide-amme systems at temperatures below the glass temperature of the respective polymer cured to the limtt, Ts~o, the reaction proceeds to a given degree, and can be resumed when the curmg temperature is increased. The incompleteness of the curing process is connected with hindered diffusion in the glassy matrix [I-4] and therefore information about relaxation processes in the course of curing is of great importance for our understanding of the specificittes of polyfunctional polyaddition [1]. In this work, crosslinklng was studied in the system dlglyctdyl ether of diphenylolpropane ( D G E G F P ) - l , 3 - b l s - ( a m i n o m e t h y l ) a d a m a n t a n e ( D A M A D ) . The relaxation properties of the reaction products were studied by pulsed N M R spectroscopy which IS sensitive to structural and kinetic mhomogenelties at the topological level [5-7]. Relaxation properties were studied with the coherent N M R relaxometer for protons at 17 MHz. The curves of transversal magnetization decay were recorded by the C a r r - P u r c e l l - M e i b o o m - G i l l method or by free induction decay. The measurements were performed under isothermal conditions at 296, 303, 313, 333 + 2 K, and with stepwise temperature increase in the range 296--493 K, with * Vysokomol soyed. A29: No. 9, 1986-1991, 1987,