The Influence of molecular structure on the properties of poly(ethylene terephthalate)/ poly(butylene terephthalate) blends Текст научной статьи по специальности «Химические науки»

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DOI: http://dx.doi.Org/10.15688/jvolsu10.2015.1.2

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THE INFLUENCE OF MOLECULAR STRUCTURE ON THE PROPERTIES OF POLYETHYLENE TEREPHTHALATE)/ POLY(BUTYLENE TEREPHTHALATE) BLENDS

Mikitaev Muslim Abdulahovich

Candidate of Chemical Sciences, Senior Researcher, Department of Organic Chemistry and Macromolecular Compounds, Kabardino-Balkarian State University named after H.M. Berbekov I_dolbin@mail.ru

Chernyshevskogo St., 175, 360004 Nalchik, Russian Federation

Kozlov Georgiy Vladimirovich

Senior Researcher,

Department of Organic Chemistry and Macromolecular Compounds, Kabardino-Balkarian State University named after H.M. Berbekov I_dolbin@mail.ru

Chernyshevskogo St., 175, 360004 Nalchik, Russian Federation

Pearce Eli M.

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i-i <

Sa Doctor of Sciences, Professor,

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Brooklyn Branch of New York University § EPearce@poly.edu

Jay St., 333, 12001 Brooklyn, United States of America

d

^ Zaikov Gennadiy Efremovich

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S Doctor of Chemical Sciences, Professor,

® Head of Department of Biological and Chemical Physics of Polymers, £ Institute of Biochemical Physics named after N.M. Emanuel, RAS

chembio@sky.chph.ras.ru > Kosygina St. 4, 119334 Moscow, Russian Federation

d §

8 Mikitaev Abdulah Kasbulatovich

Doctor of Chemical Sciences, Professor,

S

^ Department of Organic Chemistry and Macromolecular Compounds, ji Kabardino-Balkarian State University named after H.M. Berbekov I_dolbin@mail.ru

~ Chernyshevskogo St., 175, 360004 Nalchik, Russian Federation

Abstract. It has been confirmed that properties of polymer materials are encoded by the structure at the molecular level. The impact toughness of poly(ethylene terephthalate)/ poly(butylene terephthalate) blends is controlled by macromolecular coils interactions, which are reflected on the structure of their fractal dimension. It has been shown that the interaction parameter defines the fracture type of the indicated blends.

Key words: polymer blends, macromolecular coils, structure, interaction, properties.

Introduction

Results and Discussion

According to the known Academician Kargin postulate [5], polymer properties are encoded on molecular level and are realized on supramolecular (suprasegmental) one. For poly(ethylene terephthalate)/poly(butylene terephthalate) (PET/PBT) blends, processed by two different methods, the essential distinction of their properties was found [12]. So, the impact toughness of blends PET/PBT, processed by extrusion and subsequent injection molding, is on the average 3.5 times larger of this characteristic for the same blends, processed by injection molding only. The purpose of the present work is the study of this effect on both molecular and supramolecular levels.

Experimental

Commercial engineering grade polymers: PET (992 lW-Eastman Chemicals) and PBT (Vestodur X7085-Degusa Huls AG) were used in the research. Two types of blends were prepared: one by injection moulding using Engel machine ES 80/20HLS with the screw length/diameter ratio L/D =18 and D = 22 mm and the second mixed at first by extrusion moulding machine Fairex with L/D = 24 and D = 25 mm and then injected on Engel machine. The processing temperature has been in the range from 498 K to 528 K for injection molding and in the range from 453 K to 513 K for extrusion at pressure of 90 and 30 MPa, respectively. The following PET/PBT were prepared: 100/0; 95/5; 90/10; 80/20; 70/30; 50/ 50; 25/75; 0/100 wt [12].

Charpy's impact toughness has been measured on impact hammer INSTRON-PWS and Brinell microhardness on the hardness equipment HPK8206 and uniaxial tension tests have been performed on INSTRON-1115 testing machine [12].

As it is known [3], the mean-square distance between macromolecule ends (h2) is given by the following relationship:

(h2) ~ MM1

(1)

where MM is polymer molecular weight, e is interaction parameter.

Within the frameworks of fractal analysis the parameter e is defined with the aid of the equation [8]:

Df=

s +1'

(2)

where Df is fractal dimension of macromolecular coil, which in case of linear polymers can be estimated as follows [9]:

D ,= -

2df 3

(3)

where df is a polymer structure fractal dimension, which is determined with the aid of the equation [8]:

H

(

0.07 + 0.6 ln

3d,

3 - dt

(4)

where HB is Brinell microhardness, sY is yield stress.

The parameter e characterizes an interaction type of macromolecular coils in polymer blend: at e = 0 interaction of attraction and repulsion are balancing ones, at positive e repulsion interactions are dominant, at negative e are attraction ones [9].

The impact toughness Ap of polymer specimens without a notch is defined by two factors: the deformation energy release critical rate Gj, characterizing specimen plasticity, and the length of critical structural defect acr, initiating fracture process [9]. The value Gj is determined according to the equation [10]:

2

a

Y

с = 0.24 + 1.10(d -df ), kJ/m2,

(5)

where d is dimension of Euclidean space, in which a fractal is considered (it is obvious, that in our case d =3).

In Fig. 1 the dependence of interaction parameter e on the concentration of PBT CPBT for the considered blends PET/PBT is adduced. This plot has two features. Firstly, it is a mirror reflection of the dependence of the considered blends impact toughness on their composition, adduced in work [12], and secondly, all values e are positive, i.e. the repulsion interactions are dominant for all considered blends. The indicated mirror reflection of the parameters Ap and e supposes Ap growth at e reduction, i. e. repulsion interaction weakness.

0 50 100

CPBT, weigth %

Fig. 1. The dependences of interaction parameter e on PBT content CPBT for blends PET/PBT, prepared by extrusion and subsequent injection moulding (1) and injection moulding only (2)

In Fig. 2 the dependence of deformation energy release critical rate Gj, calculated according to the equation (5), on the parameter e value is adduced for the considered blends PET/ PBT, which demonstrates linear Gj growth at e increasing. Such look of the dependence Gj (e) was expected, since repulsion interactions intensification enhances molecular mobility, that always results in polymers plasticity enhancement [6]. The correlation Gj (e) can be described analytically by the following empirical equation:

G, - 1.56(e + 0.33), kJ/m2.

(6)

The equation (6) allows to determine limiting values Gh for the considered blends. At e = - 0.33 (the greatest attraction interaction) minimum value

Gj is equal to zero and at e = 1.0 (the greatest repulsion interaction) the maximum value G^ is equal to 2.07 kJ/m2 ^

The length of critical structural defect acr can be determined with the aid of the following equation [9]:

A - 'c Ap - 72a

(7)

where L is distance between impact hammer supports (span).

Fig. 2. The dependence of deformation energy release critical rate G^ on interaction parameter e for blends PET/PBT. Designations are the same, that in Fig. 1

In Fig. 3 the dependence of the length of critical structural defect a on interaction

cr

parameter e for blends PET/PBT is adduced. The linear acr growth at e increasing is observed, that can be described analytically as follows:

acr - 560(e - 0.20), mcm.

(8)

acr, mcm

300

200

100

0.2

0.4

0.6

0.8

Fig. 3. The dependence of critical structural defect

length acr on interaction parameter e for blends PET/PBT. Designations are the same, that in Fig. 1

s

8

Let us consider the limiting acr values. At e = 0.20 the value acr is equal to zero. The indicated condition e = 0.20 according to the equation (2) corresponds to Df = 1.667 and according to the equation (3) - df =2.5. As it is known [1], the criterion d^> 2.5 means the transition from brittle fracture to quasibrittle (quasitough) one, where the main role plays not acr value, but local (macroscopic) plastic deformation mechanisms. The greatest value acr at maximum repulsion interaction, i.e. e =1.0, is equal to 448 mcm.

The equations (2) and (3) combination allows to obtain the following relationship between basic structural characteristic df and molecular parameter e, which is true for the linear polymers:

dr =

3

1+e '

(9)

Thus, the equations (6)-(9) suppose the correlation between Ap and d. This supposition is confirmed by Fig. 4 plot, where the dependence Ap(df) for the considered PET/PBT blends is adduced. This dependence shows linear Ap growth at df increasing and the equations (6)-(8) combination allows to obtain the following relationship:

A

e + 0.33 e - 0.20'

(10)

Ap, kJ/m 15

Fig. 4. The dependence of impact toughness Ap on structure fractal dimension df for blends PET/PBT. Designations are the same, that in Fig. 1

From the relationship (10) it follows, that

minimum value A =0 is realized at e = -0.33, i.e.

p '

the greatest attraction interaction or at polymer blend zero plasticity, that was to be expected (see

the equation (7)). The greatest value Ap ^да is realized at e = 0.20 or df =2.5. From the practical point of view the condition Ap ^ да means the transition from brittle to tough fracture [1].

Conclusions

Thus, the present work results have confirmed the stated above Academician Kargin postulate. The impact toughness Ap of PET/PBT blends is controlled by macromolecular coils interactions, which on molecular level are reflected by structure fractal dimension. It has been shown that interaction parameter e controls the transition to both absolutely brittle (A = 0, e = -0.33) and to tough (Ap ^да, e = 0.20) fracture.

Acknowledgements

The work is performed within the complex project on creation of hi-tech production with the participation of the Russian higher educational institution, the Contract of Tanneta JSC with the Ministry of Education and Science of the Russian Federation ofFebruary 12, 2013 No. 02.G25.31.0008 (Resolution of the Government of the Russian Federation No. 218).

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7. Kozlov G.V, Dolbin I.V, Zaikov G.E. The Fractal Physical Chemistry of Polymer Solutions and Melts. Toronto, New Jersey, Apple Academic Press, 2014. 316 p.

8. Kozlov G.V., Mikitaev A.K. Structure and Properties of Nanocomposites Polymer/Organoclay. Saarbracken, LAP LAMBERT Academic Publishing GmbH and Co., 2013. 318 p.

9. Kozlov G.V., Yanovskiy Yu.G., Zaikov G.E. Structure and Properties of Particulate-Filled Composites: the Fractal Analysis. New York, Nova Science Publishers, Inc., 2010. 282 p.

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ВЛИЯНИЕ СТРУКТУРЫ НА МОЛЕКУЛЯРНОМ УРОВНЕ НА СВОЙСТВА СМЕСЕЙ ПОЛИ(ЭТИЛЕН ТЕРЕФТАЛАТА)/ПОЛИ(БУТИЛЕН ТЕРЕФТАЛАТА)

Микитаев Муслим Абдулахович

Кандидат химических наук,

старший научный сотрудник кафедры органической химии и высокомолекулярных соединений,

Кабардино-Балкарский государственный университет им. Бербекова

I_dolbin@mail.ru

ул. Чернышевского, 175, 360004 г. Нальчик, Российская Федерация

Козлов Георгий Владимирович

Старший научный сотрудник кафедры органической химии и высокомолекулярных соединений,

Кабардино-Балкарский государственный университет им. Бербекова

I_dolbin@mail.ru

ул. Чернышевского, 175, 360004 г. Нальчик, Российская Федерация

Пирс Элай М.

Доктор наук, профессор,

Бруклинский филиал Нью-Йоркского университета EPearce@poly. edu

ул. Джей, 333, 12001 г. Бруклин, Соединенные Штаты Америки

Заиков Геннадий Ефремович

Доктор химических наук, профессор,

заведующий отделом биологической и химической физики полимеров, Институт биохимической физики им. Н.М. Эмануэля РАН chembio@sky. chph. ras.ru

ул. Косыгина, 4, 119334 г. Москва, Российская Федерация

Микитаев Абдулах Касбулатович

Доктор химических наук,

профессор кафедры органической химии и высокомолекулярных соединений, Кабардино-Балкарский государственный университет им. Бербекова I_dolbin@mail.ru

ул. Чернышевского, 175, 360004 г. Нальчик, Российская Федерация

Аннотация. В ходе исследования было подтверждено, что свойства полимерных материалов кодируются структурой на молекулярном уровне. Ударная вязкость смесей поли(этилен терефталата)/поли(бутилен терефталата) регулируется с помощью макромолекулярных взаимодействий, которые отражаются на структуре их фрактальной размерности. Показано, что параметр взаимодействия определяет тип излома указанной смеси.

Ключевые слова: смеси полимеров, высокомолекулярные соединения, структура, взаимодействие, свойства.