книги / Структурно-механические свойства эластомерных композитных материалов

Для решения обратной задачи использовались те же компоненты. В таблице приведены технические требования к механическим характеристикам наполненного эластомера, разрабатываемого применительно

кпокрытиям спортивных сооружений.

Врезультате обработки данных компьютерной программы был спроектирован состав композиции со следующими параметрами:

температура стеклования полимерного связующего – 185 К; объёмная доля полимера в связующем – 0,60; объёмная доля пластификатора в связующем – 0,40;

объёмная доля наполнителя – 0,83 при значении m , равном 0,96;

концентрация поперечных химических связей в полимере – 2·10-5 моль/см3;

объёмные доли фракций наполнителя – (1200-1500 мкм) : (150180 мкм) : (0,5-1,5 мкм) = 0,591 : 0,279 : 0,130 соответственно;

параметр отслоения связующего от крупной фракции – tcr ( 1,25) / 0,7.

Рис. 6. Зависимость условного напряжения σ от удлинения α: линия – расчет; точки – эксперимент

На рис. 7 представлены проектные зависимости ( ) для трёх тем-

ператур технического задания. Там же обозначены символы требований к механическим характеристикам наполненного эластомера.

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Требуемые значения механических характеристик наполненного эластомера

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ВЫВОДЫ

1.Разработано физико-математическое описание зависимости механических характеристик наполненного эластомера от основных параметров состава композиции.

2.Даны примеры инженерного решения прямой и обратной задач при разработке новых полимерных композиционных материалов с требуемыми свойствам.

СПИСОК ЛИТЕРАТУРЫ

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2.Rutgers J.R. // Rheological Acta. – 1962. – Vol. 2. No. 4. – P. 305–348.

3.Chong J.S., Christiansen E.B., Boer A.D. // J. Appl. Polum. Sci. – 1971. – Vol. 15. – P. 2007–2024.

4.Нильсен Л.Е. Механические свойства полимеров и полимерных композиций. – М., Химия, 1978. – 310 с.

5.Bueche F. Physical Properties of Polymers. – N.-Y.: Wiley Interscience, 1962. – 368 p.

6.Saunders J.H., Frish K.C. Polyurethanes. Part I. Chemistry. – N.-Y.: – London: Interscience Publishers, 1962. – 470 p.

7.Fedors R. Effect of Filler on the mechanical Behaviour of Elastomers. Relationships between the small strain Modulus and the Type and Concentration of Filler. // Polymer. – 1979. – Vol. 20. – № 3. – P. 324–328.

8.Lewis T.B., Nielsen L.E. Viscosity of Dispersions and Agrigates of Suspensions Spheres // Trans. Soc. Rheology. – 1968. – Vol. 12. – № 3. – P. 421–443.

9.Sato Y., Furukawa J. A Molecular Theory of filler Reinforcement Based upon the conception of internal Deformation // Rub. Chem. Techn. – 1963. – Vol. 36. – No. 4. – P. 1081–1106.

10.Fedors R., Landel R. Mechanical Behavior of SBR-glass bead Composites // J. Pol. Sce. – 1975. – Vol. – № 3. – P. 579–601.

11.Farris R.J. The Character of the Stress-Strain Function for Highly Filled Elastomers // Trans. Soc. Rheology. – 1968. – Vol. 12. – №2. – P. 303–314.

12.Farris R.J. The Influence of Vacuole Formation on the Response and Failure of Filled Elastomers // Trans. Soc. Rheology. – 1968. – Vol. 12. – № 2. – P. 315–334.

13.Smith T.L., Chy W.H. Ultimate Tensile Properties of Elastomers // J. Polymer Sci. – 1972. – Part A – 2, Vol. 10, – № 1. – P. 133–150.

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14.Забродин В.Б., Зыков В.И., Чуй Г.Н. Молекулярная структура сшитых полимеров // Высокомолекулярные соединения. – 1975. –

Том XVII А. – № 1. – С. 163–169

15.Ван Кревелен Д.В. Свойства и химическое строение полимеров. (Пер. с англ.) – М.: Химия, 1976. – 414 с.

16.Мэнсон Дж, Сперлинг Л. Полимерные смеси и композиты. (Пер.

сангл.) – М.: Химия, 1979. – 439 с.

17.Кристенсен Р. Введение в механику композитов. (Пер. с англ.)

М.: Мир, 1982. – 334 с.

18.Фудзии Т., Дзако М. Механика разрушения композиционных материалов. (Пер с англ.) – М.: Мир, 1982. – 232 с.

19.Ермилов А.С., Зырянов К.А. Концентрационная зависимость усиления каучуков и резин дисперсными наполнителями // Заводская лаборатория. Диагностика материалов. – 2001. – Т. 67. – № 9. – С. 62–64.

20.Ермилов А. С., Федосеев А. М. Комбинаторно-мультипликатив- ный метод расчёта предельного наполнения композиционных материалов твёрдыми дисперсными компонентами // Журнал прикладной химии. – 2004. – Т. 77, Вып. 7. – С. 1218–1220.

Russian Journal of Applied Chemistry, 2012, Vol. 85, No. 7

INFL UENCE OF FORMULATION PARAMETERS

ON THE MECHANICAL FAILURE ENERGY OF FILLED ELASTOMERS

A. S. Ermilov and E. M. Nurullaev

Perm National Research Polytechnic University, Perm, Russia

Abstract–Ways to increase, by optimizing the formulation, the energy of mechanical failure of fi lled 3D-crosslinked elastomers intended for application of a frost-resistant and waterproof layer onto road asphalt were examined.

Filled elastomers based on a 3D-cross-linked polymeric binder, possibly plasticized, are widely used in various branches of industry, including construction of buildings. For these applications, the long-term strength of the materials is of particular importance. For example, application of a frost-resistant

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waterproof layer onto road asphalt requires a polymeric formulation with increased level of deformation and strength characteristics in a wide temperature interval of operation. In this study we examined the ways to improve, by optimizing the formulation, the energy of mechanical failure of a material applied onto road asphalt under the conditions of uniaxial extension with the aim to prolong the service life of a road by an order of magnitude. The work of failure was estimated in the form of an “envelope” of the dependence of the nominal breaking tensile stress σb (stress related to the initial specimen cross section) on the breaking elongation εb, related to the degree of relative breaking elongation as αb = 1 + εb/100%. It is known [1] that the failure envelope (logσb–logαb) corresponds to the work of failure in the form of the area of the extension where σ is the nominal stress; α = (1 + ε/100) is the specimen elon-

gation related to strain ε (%); ch Ms , concentration of chemical cross-links

in the polymeric base of the binder (ρ is the polymer concentration and Ms is

the statistical average molecular weight of segments diagram in Cartesian coordinates:

b

Ab d .

1

If an elastomer does not crystallize prior to failure, usually the break characteristics determined at various temperatures and extension velocities, when superimposed, are fitted by a common curve in log(σbT0/T) vs. log(αb – 1) coordinates, where Т and Т0 are the testing temperature and an arbitrarily chosen reference temperature, respectively. The curve obtained is termed failure envelope [2–4].

The expression for σ(α) used previously for solving the direct and inverse problems [5] with the aid of the specially developed software [6] took into account the possible peel-off of filler particles from the polyme ric binder. Considering the requirements to the material applied onto road asphalt, we used the mathematical description for the case when the material preserves itsintegrity up to failure:

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between cross-linking points); φr, volume fraction of the polymer in the binder containing a plasticizer; R, universal gas constant; T∞, equilibrium temperature (concentration of “physical” cross-links is negligibly low); Т, testing temperature; Tg, structural glass transition point of the polymeric binder; a , ve-

locity shift coeffi cient; φ, volume fraction of solid particles of the grained fi ller; φm, maximal volume fraction of the fi ller; and φ/φm, effective degree of volume filling.

It follows from formula (1) that, in particular, σ(α) depends on φ/φm. The effect of this parameter on the failure energy of the fi lled elastomer was studied experimentally. The quantity φm depending on the shape and fractional composition of filler particles and on the physicochemicalinteraction at the polymeric binder–filler boundary can be determined viscometrically [7] or calculated, e.g., by a combinatorial multiplicative method [8].

In addition, we examined the effect of directional catalysis on the formation of the chemical cross-link network of the polymeric base of the binder of the filled elastomer and on its limiting characteristics σb and εb under the conditions of uniaxial extension. This formulation factor is associated with suppression of side reaction in the formation of the 3D polymer network, ensuring more uniform molecular weight of segments between cross-links,

Ms / ch .

EXPERIMENTAL

As frost-resistant polymeric base of a waterproof layer to be applied onto road asphalt, we used 3D-cross-linked noncrystallizing copolymer of two low-molecular-weight rubbers with terminal functional groups: epoxy [–CH(O) CH2 PDI-3B] , grade rubber] and carboxy (–COOH, SKD – KTR grade rubber), in 1 : 2 molar ratio. The cross-linking agent was EET-1 trifunctional epoxy resin taken in stoichiometric ratio. In contrast to bitumen binder of asphalt concrete, this elastomer in the highly fi lled state remained rubbery down to 223 K. On introducing a plasticizer, e.g., dioctyl sebacate, the structural glass transition point of the formulation decreased to 213 K.

To ensure the required deformation and strength characteristics of the layer applied onto asphalt, taking into account economical factors, we included into the formulation a filler, natural silicon dioxide (SiO2) in the form of river quartz sand. We used fractions with weight-average particle sizes of 250, 5, and 1 μm, obtained by mechanical pulverization. The filler volume fraction

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was 0.712. The components were mixed in a Verner–Pfl eiderer batch apparatus. The 3D polymerization temperature was 343 K.

Figure 1 shows the failure envelopes σb (MPa) = f [εb (%)] (on the logarithmic scale) of specimens of the elastomer filled with two-fraction (curve а) and three-fraction (curve b) SiO2. The test temperature was 223–323 K, and the relative extension velocity, 1.4 × 10–3 s–1. The filler was formulated as follows: two-fraction, (250 : 5) μm = (20 : 80)%; three-fraction, (250 : 5 : 1) μm = = (40 : 40 : 20)%. In so doing, the specifi c surface areas of the contact of the filler particles with the binder interlayer were approximately equal.

10

σb, MPaМПа

1

0,1

Fig. 1. Failure envelopes σb = f (ε) for specimens of the elastomer filled with (a) two-fraction (reference) and (b) three-fraction SiO2. T, K: (1) 323,

(2) 223, and (3) 293

The maximal degree of the volume fi lling φm, calculated from the viscometric data, was 0.752 and 0.816, respectively. Figure 1 shows (at normal transition from lower to upper straight line) that, at a constant volume fraction of SiO2 (φ = 0.712), a change in the effective volume filling φ/φm from 0.712/0.752 = 0.946 to 0.712/0.816 = 0.872 leads to an increase in the energy of the mechanical failure of the material by a factor of 1.5–1.6.

Analysis of microstrains of the elastic polymericbinder between solid fi ller particles [9] shows that an increase in the statistical size of the binder in-

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terlayer at φ = const leads to an increase in the breaking elongation of the fi lled elastomer in accordance with the expression

where α0 = (1 + ε0/100) is the breaking elongation of the free polymeric binder. In our case, the effective degree of volume fi lling decreased from 0.946 to 0.872, which favored an increasein the “emission” of the polymeric binder

energy, leading to an increase in the failure energy of the composite material due to strong effect of the formulation parameter φ/φm both on the nominal stress as a function of the relative elongation [σ = f (α)] and on the initial viscoelastic modulus (E = dσ/dα at α = 1) [5].

Polydiene–urethane–epoxy rubber PDI-3B, in contrast to polybutadiene– carboxylate rubber SKD-KTR, when subjected to prolonged heating, tends to homopolymerization, including cyclization of macromolecules. These side reactions occurring via opening of epoxy rings can also occur in the course of 3D copolymerization of these rubbers with EET-1 epoxy resin. Naturally, these phenomena lead to a decrease in the molecular homogeneity of the chemical network as polymeric base of the fi lled elastomer. The molecular-weight dis-

tribution of segments between cross-links Ms becomes wider, which is un-

favorable at stressed and strained state of the layer applied onto road asphalt. To suppress side reactions by catalytic acceleration of the main reaction

between the epoxy and carboxy groups, we used π complex compounds, acetylacetonates of variable-valence metals (ААМ, M = Zn2+, Al3+, Zr3+, Mn2+, Fe3+, Co2+), including a Co2+ adduct. The general formula of the chelates is

СН3

О С МеСН

ОС

Figure 2 shows the failure envelopes for the corresponding filled elastomers cured (3D-cross-linked) using various chelate catalysts (AAM), compared to the initial specimen. The catalyst content in the polymeric binder was 0.03 wt %. As fi ller (φ = 0.712) we used three-fraction SiO2, (600 : 250 : 15) μm = (50 : 30 : 20)%. The test temperature interval was 278–308 K, and the relative extension velocity, 1.4 × 10–3 s–1.

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As seen from the above data, catalytically directed curing allows the mechanical failure energy of the compounds tested to be increased by a factor of 1.5–2.0 relative to the initial formulation. In so doing, the curing time decreased by a factor of approximately 2, with the required rheological properties of the compound preserved.

Fig. 2. Failure envelopes σb = f (ε) for fi lled elastomers cured using chelate catalysts in comparison with the initial specimens with different degrees of cross-linking. Uniaxial extension. Catalyst used: (1) none, (2) AAZn, (3) AACo, (4) AAFe, and(5) AAMn

Thus, a combination of the formulation factor (φ/φm) and catalytically directed 3D polymerization of the polymeric base of the fi lled elastomer can ensure a threefold increase in the mechanical failure energy.

CONCLUSIONS

(1)At a constant volume fraction of solid particles, the energy of the mechanical failure of the fi lled elastomer increases by a factor of 1.5 with a decrease in the effective degree of volume fi lling depending on the shape and fractional composition of the particles and on their physicochemical interaction with the polymeric binder.

(2)Catalytically directed 3D copolymerization of epoxidized and car-

boxylate rubbers increases the mechanical failure energy of the material based on the fi lled elastomer by a factor of 2.

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(3) A combination of the above-indicated formulation factors allows the mechanical failure energy of the material to be increased by a factor of 3, which should prolong the service life of automobile roads.

REFERENCES

1.Smith T.L. Am. Soc. Test. Mater. Spec. Publ., 1962, no. 325, pp. 60–89.

2.Smith T.L. J. Polym. Sci., Part A, 1963, vol. l, pp. 3597– 3607.

3.Smith T.L. J. Appl. Phys., 1964, vol. 35, pp. 27–34.

4.Nielsen L.E. Mechanical Properties of Polymers and Composites, New York: Dekker, 1974.

5.Ermilov A.S. and Nurullaev E.M. Zh. Prikl. Khim., 2011, vol. 84, no. 9, pp. 1558–1561.

6.Ermilov A.S., Nurullaev E.M., Subbotina T.E., and Duregin K.A. Certifi cate of Offi cial Registration of Computer Program no. 2011615640.

7.Ermilov A.S. and Zuryanov K.A. Zav. Lab. Diagn. Mater., 2001, vol. 67, no. 9, pp. 62–64.

8.Ermilov A.S. and Fedoseev A.M. Zh. Prikl. Khim., 2004, vol. 77, no. 7, pp. 1218–1220.

9.Val’tsifer V.A., Alikin V.N., and Ermilov A.S. Mekh. Kompoz. Mater., 1987, no. 5, pp. 934–935.

Журнал прикладной химии, 2012, Т. 85, №. 7.

ВЛИЯНИЕ РЕЦЕПТУРЫХ ПАРАМЕТРОВ НА ЭНЕРГИЮ МЕХАНИЧЕСКОГО РАЗРУШЕНИЯ НАПОЛНЕННЫХ ЭЛАСТОМЕРОВ

А.С.Ермилов, Э. М. Нуруллаев

Пермский национальный исследовательский политехнический университет, Пермь, Россия

Показано, что, используя направленный катализ формирования полимерного связующего и варьируя эффективной степенью объемного наполнения, можно увеличить энергию механического разрушения эластомеров, наполненных дисперсными частицами в 2–3 раза. Материалы

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