Polymer Journal, Vol. 14, No. 8, pp 671-673 (1982)

SHORT COMMUNICATION

Rubber-Modified Isocyanurate-Oxazolidone Resins

Shun-ichi NUMATA and Noriyuki KINJO

Hitachi Research Laboratory, Hitachi Ltd., Kuji-cho, Hitachi-shi, Jbaraki 319-12, Japan

(Received February 16, 1982)

KEY WORDS Viscoelasticity 1 Rubber-Modified Plastics I Thermosetting Resin I Isocyanurate-Oxazolidone Resin I Isocyanate I Epoxide I Carboxyl­ Terminated Copolymers of Butadiene and Acrylonitrile I

It is well known that the dispersion of rubber physical structure in which particles are dispersed particles into matrix polymer phases improves the throughout a matrix phase. Epoxide and isocyanate toughness of a hard and brittle polymer matrix. additives will be considered in this paper. Much research1 - 4 has been carried out in this area Polyglycidyl ether of phenol-formaldehyde no­ and many ideas have been proposed to explain this volac (DEN431 from DOW Chemical Co.) and rubber-toughening phenomenon. Thermoplastic re­ diglycidyl ester of linoleic dimer acid (EP871 from sins, such as acrylonitrile-butadiene-styrene co­ Shell Chemical Co.) are immiscible with each other. polymer (ABS), styrene-butadiene-styrene co­ However, commercially available diphenylmethane- polymer (SBS), and high impact polystyrene 4,4'-diisocyanate (L-MDI, Desmodur CD from (HIPS), are outstanding examples of rubber­ Bayer AG) makes the binary systems of EP871 and modified plastics that have been found to have DEN431 miscible with each other/5 so that trans­ practical utility, because of their ability to im­ parent one-phase varnishes can be produced. When prove polymer toughness. such varnishes were heated after adding 0.1% by A similar method has also been used to produce weight of 2-ethyl-4-methylimidazole as a curing toughened thermosetting resins. Carboxyl­ agent, a visible micro-phase separation was ob­ terminated copolymers of butadiene and acryloni­ served during the cross-linking reaction under an trile (CTBN) are increasingly being used in many isothermal condition of 80°C, before gelation. The epoxy applications as a means of improving the final cured products were opaque hard resins. SEM fracture toughness of epoxy resins. 5 -s Recent analysis has shown that particle phases are ran­ studies9 •10 have shown that this improvement is domly scattered in continuous matrix phases. These brought about by the partially miscible nature of results will be reported elsewhere. components such as epoxides and CTBN. This The viscoelastic behavior of the cured resins of miscibility allows the morphology of a mixture to be DEN431 trinary systems are manipulated by controlling the composition and shown in Figure 1. The equivalent ratio of iso­ curing conditions. New rubber-modified thermo­ cyanate and epoxy groups was 2.5. As can be seen setting resins will be described in this study. from the figure, the relaxation behavior of these The authors have previously reported that var­ resins shows the typical pattern which is usually nishes composed of polyfunctional isocyanates and observed for rubber-modified plastics. Three disper­ epoxides can readily form isocyanurate and oxa­ sions, labeled IX5 , /3, and y, can be observed in the zolidone rings in the molecular structure of the temperature range from -196°C to 300°C. The cured resins. These resins are called "Isocyanurate­ peak height of the IX5 -dispersion increases with Oxazolidone Resins" or "ISOX Resins." 11 •12 The increasing EP871 content in the varnishes. This objective of this study is to show that ISOX resins suggests that the IX5 -dispersion is due to a glass can also be modified by additives to develop a transition in the rubber phase which is probably

671 S. NuMATA and N. KINJO

1010r------,

':'E z "108 l.LI

L-MDI 1/E ratio = 2.5

106L______Temperature / oc

Figure 1. Viscoelastic behavior of rubber-modified Isocyanurate-Oxazolidone resins. The following commercial materials were used: polyglycidyl ether of phenol-formaldehyde novolac (DEN431 from DOW Chemical Co.), diglycidyl ester oflinoleic dimer acid (EP871 from Shell Chemical Co.) and modified diphenylmethane-4,4'-diisocyanate (L-MDI, Desmodur CD from Bayer AG).

resulting from the reaction of L-MDI with EP871. with L-MDI and DEN 431 are transparent before The a-dispersion due to this glass transition in the curing. However, phase separation occurred during matrix phase was not observed below 300°C in this curing after the addition of a catalyst. The resultant study. The fi-dispersion was assigned to the local cured products were opaque hard plastics. The mode motion of the backbone chains of !SOX viscoelastic behavior of these resins is shown in resins. The y-dispersion was due to the molecular Figure 2, which also shows the typical behavior motions of long alkyl chains of EP871. pattern observed for rubber-modified plastics. In It is well-known that isocyanates easily react with this case, the o:, -dispersion and fi-dispersion can be carboxylic acids to produce amidesY CTBN readily observed, but the y-dispersion is not so undergoes a similar reaction with excess L-MDI to readily evident. The relaxation strength of the o:,­ produce CTBN capped with L-MDI. The reaction dispersion increases with increasing the CTBN con­ for this is as follows: tent. The o:,-dispersion is probably due to the glass transition in the rubber phase, which includes 20CN-R-NCO HOOC-R' -COOH + CTBN. (L-MDI) (CTBN) The o:,-dispersion in Figure I was observed at 200ac, 2 hr OCN-R-NHCO-R'-CONH-R-NCO -42°C, which is lower than the temperatures of (CTBN capped with L-MDI) l0°C and -25°C observed for cured EP871-L­ MDP2 and EP871/4 respectively. The o:,-dispersion The CTBN used in this study was Hycar CTBN in Figure 2 was observed at - 60°C, which is lower (1300 x 8), manufactured by B. F. Goodrich Co. than the temperature (-45°C) obtained for unre­ The acrylonitrile content of the CTBN is 17 wt% acted CTBN. That is, the glass transition of the and the Tg measured by TBA (

672 Polymer J., Vol. 14, No. 8, 1982 Rubber-Modified Isocyanurate-Oxazolidone Resins

10 lOr------,

::: . w

I /E ratio= 2.5 1as '-----_-.l.:..oo.------,jo.------.1"*'oo.------..-;2ob;-o----..3*'oo;;--' Temperature / °C Figure 2. Viscoelastic behavior of rubber-modified Isocyanurate-Oxazolidone resins cured from vanishes consisting of L-MDI, CTBN capped with L-MDI and DEN431.

temperatures is apparently caused by thermal 3. R. P. Kambour, J. Polym. Sci., Macromol. Rev., 7, I shrinkage stress produced by the difference in the (1973). thermal expansion coefficients of the rubber par­ 4. C. B. Bucknall and R. R. Smith, Polymer, 6, 437 ticles and glassy matrix. A similar phenomenon was (1965). 5. E. H. Rowe, A. R. Siebert, and R. S. Drake, Mod. observed in CTBN modified epoxides.9 Plast., 47, 110 (1970). The results of additional studies on other proper­ 6. J. N. Sultan and F. J. McGarry, Polym. Eng. Sci., 13, ties of rubber-modified ISOX resins now under way 29 (1973). will be published in the near future. 7. N. Kalfoglou and L. Williams, J. Appl. Palm. Sci., 17, 1377 (1973). Acknowledgements. The authors wish to thank 8. S. Kunz-Douglass, P. W. R. Beaumont, and M. F. Dr. J. Mukai, Mr. M. Sato and Mr. T. Narahara of Ashby, J. Mater. Sci., 15, 1109 (1980). 9. L. T. Manzione, J. K. Gillham, and C. A. Hitachi Research Laboratory for their helpful com­ Mcpherson, J. Appl. Polym. Sci., 26, 889,907 (1981). ments. The authors also wish to thank Mr. Y. 10. T. T. Wang and H. M. Zupko, J. Appl. Polym. Sci., Katsuya of Yamazaki Works in Hitachi Chemical 26, 2391 (1981). Co. Ltd. for his interest in our work and for 11. N. Kinjo, T. Koyama, T. Narahara, and J. Mukai, providing facilities for making the viscoelastic Proceedings of the 14th Electrical/Electronics In­ measurements. sulation Conference, 1979, p 129. 12. N. Kinjo, S. Numata, T. Koyama, and Y. Katsuya, submitted to Polym. J. REFERENCES 13. R. G. Arnold, J. A. Nelson, and J. J. Verbanc, Chern. Rev., 57, 47 (1957). I. E. H. Merz, G. C. Claver, and M. J. Baer, J. Polym. Sci., 22, 325 (1956). 14. S. Numata and N. Kinjo, unpublished data. 15. S. Akiyama, T. Inoue, and T. Nishi, "Polymer 2. S. Newman and S. Strella, J. Appl. Polym. Sci., 9, 2297 (1965). Blends," CMC Press, Tokyo 1981, chapter 4, p 281.

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