Research ArticleDevelopment of Epoxy-Polyester Composite with ImprovedThermophysical Properties for Restoration of Details ofSea and River Transport

A. Buketov, M. Brailo, S. Yakushchenko , and A. Sapronova

Department of Transport Technologies, Kherson State Maritime Academy, 20 Ushakova Ave., Kherson 73000, Ukraine

Correspondence should be addressed to S. Yakushchenko; yakushchenko.sv@gmail.com

Received 16 April 2018; Accepted 31 August 2018; Published 2 October 2018

Academic Editor: Yee-wen Yen

Copyright © 2018 A. Buketov et al. )is is an open access article distributed under the Creative Commons Attribution License,which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

)e results of the experimental investigations of the optimization of the content of the polyester resin in the epoxy binder areshown in the work. It was determined that composite with concentration of the polyester (q� 10 mas.fr.) was characterized by themaximal values of the thermophysical properties. )e Martens thermal resistance temperature, the linear shrinkage, the thermalcoefficient of linear expansion, and the glass transition temperature of the epoxy-polyester matrix were investigated. It was foundthat introducing the polyester resin into the epoxy oligomer in quantity of q� 10 mas.fr. leads to improving the Martens thermalresistance of the material to the T� 352K and decreasing the linear shrinkage to the Δl� 0.06%. )e nonlinear dependence of theTCLE on the temperature was confirmed, and the tendency of changes in their values, depending on the content of polyester resin,was defined.)e dilatometric curves were analyzed, and the glass transition temperature of developed epoxy-polyester matrix wasdetermined at the level Ts � 318K.

1. Introduction

It is necessary to use polymer materials in the construction,repair, and restoration of individual parts and mechanismsat the present stage of the development of the transporttechnology industry [1, 2]. In this direction, one of therational solutions is the use of polymer composites.)erefore, the question of the creation of the polymericcomposite materials (CM) with improved properties is ac-tual today [3]. In particular, the advantages of CM over othermaterials (impermeability to water, chemical resistance, andhigh processability) allow them to be used in many in-dustries. A special place is occupied by shipbuilding:polymers are used in the form of final products and asa restoring material of ship systems and devices. )e detailsof the air ducts of the ship’s ventilation and air-conditioningsystem, the technological isolation of the pipes of the shipsystems, the ship pipelines of the power plants, the dead-wood bearings, etc., are the examples. Simultaneously, withthe development of technologies, the requirements to the

properties of polymers are increasing. If it is necessary toprepare a composite with a new complex of properties, it isexpedient to obtain a mixture of polymers [4, 5]. )erefore,a compound of two binders with different nature in the oneCM is interesting. )is approach allows, even at low con-centrations, to obtain a material that is characterized byincreased performance characteristics [6]. At the same time,the importance in the manufacture and operation ofa polymer product or protective coating has predictions ofindicators of thermophysical properties. For the significantdifference in thermal expansion leads to the formation ofsignificant residual stresses, which are the cause of strati-fication and destruction of products and failure of parts andmechanisms as a result. )us, the development of compositematerial with combination of polyester resin in epoxy binderwith improved and specified parameters of thermophysicalproperties is an actual task of modern industry.

)e authors had shown the results of investigation ofthermophysical properties of epoxy composites in the works[7–10]. )e kinetics of the glass transition process, thermal

HindawiAdvances in Materials Science and EngineeringVolume 2018, Article ID 6378782, 6 pageshttps://doi.org/10.1155/2018/6378782

expansion, and shrinkage were described and the thermalresistance (Martens) of materials was investigated. )e mainphysical and chemical phenomena and processes in theepoxy binder at the polymerization that have a significantimpact on the values of thermophysical properties ofcomposites were defined. )e results of experimental in-vestigations of epoxy-polyester matrix were described in theworks [11, 12]. )e adhesion and physicomechanicalproperties of polymer materials were investigated by au-thors: P. Stukhlyak (Ukraine), Yu. Sokolova, D. Zharin(Russia), M. Mikhailov, A. Karpov, Yu. Pleskachevsky(Republic of Belarus), Y. Jahani, M. Ehsani (Iran), B.Mottershead, and S. J. Eichhorn (Great Britain) [13–17].However, the thermophysical properties of developedpolymer composites are not enough investigated. As it isknown, the values of thermophysical properties significantlyaffect the performance characteristics of the product basedon the polymer material. )erefore, the analysis of dynamicsof thermophysical processes in the materials is an importantstage of the creation of polymer products.

)e purpose of this work was to develop the epoxy-polyester matrix with improved thermophysical propertiesfor restoration of details of sea and river transport.

2. Materials and Methods

For the formation of the matrix for CM with increasedthermophysical properties, the following components wereused in the work:

(a) Epoxy resin ED-20 (GOST 10587-84) (q� 100 mas.fr.).

(b) Orthophthalic dicyclopentadiene (DCPD) un-saturated preaccelerated polyester resin ENYDYNEH 68372 TAE (q� 10 mas.fr.) (the content is in-dicated on 100 weight parts of epoxy resin), whichhas an inhibitor to prevent instant polymerization(gel time from t� 20 to 24min). It should be notedthat during the copolymerization reaction of thecomposition of unsaturated polyesters with non-limiting monomer compounds in the presence ofinitiators, a significant amount of heat is released;therefore, the reaction is exothermic.

(c) )e cold curing hardener polyethylene polyamine(PEPA) (TU 6-05-241-202-78) (q� 10 mas.fr.) (thecontent is indicated on 100 weight parts of epoxyresin).

(d) )e initiator for polyester resins Butanox-M50(q� 1.5 mas.fr.) (the content is indicated on 100weight parts of polyester resin), which is a peroxideof methyl ethyl ketone (MEKP) and contains a lowamount of water and a minimum amount of polarcompounds in comparison with ethylene glycol.

)e matrix was formed at a cross-linking temperature ofT� 393± 2K.

)e following thermophysical properties of CM wereinvestigated for determining the optimal ratio between theconcentration of polyester resin (PR) and epoxy oligomer in

the binder: the Martens thermal resistance temperature, thethermal coefficient of linear expansion, the glass transitiontemperature, and the shrinkage. )e content of the un-saturated polyester has been changed within the range fromq� 10 to 120 mas.fr. per 100 mas.fr. of epoxy oligomer ED-20. )e concentration of hardeners in the compositions andthe cross-linking temperature has been defined according tothe previous research results.

)e Martens thermal resistance for CM was determinedaccording to GOST 21341-75. )e methodology of in-vestigation consists in determining the temperature at whichthe specimen has been heated at a rate of υ � 3K/min underthe influence of the constant bending load F� 5± 0.5MPa, asa result of which it is deformed on a predetermined amount(h� 6mm).

)e thermal coefficient of linear expansion (TCLE) ofmaterials was calculated by the curve of the relative de-formation from a temperature, approximating this de-pendence by the exponential function. )e relativedeformation was determined from the change in the spec-imen length with increasing the temperature under steady-state conditions (GOST 15173-70). Specimens for the re-search with the size of 65×12×12 mm had nonparallelismof the polished ends of not more than 0.02mm.)e length ofthe specimen was measured with an accuracy of ±0.01mm.)e heating rate was υ� 2K/min.

)e structure of the CM was studied on a XJL-17ATmetallographic microscope, which is equipped with a Lev-enhuk C310 NG (3.2 megapixels) camera. )e image en-largement range varied from ×100 to ×1600 times. Directlyin the work, the samples were examined with an increase of×400 times. For the processing of digital images, “LevenhukToupView” software was used.

)e materials were solidified according to the followingregimen: the formation of specimens and their holding overtime t� 12.0± 0.1 h at a temperature T� 293± 2K, heating ata speed of υ� 3K/min to a temperature T� 393± 2K,holding the specimens at a given temperature during thetime t� 2.0± 0.05 h, and slowly cooling to a temperature ofT� 293± 2K. In order to stabilize the structural processes inthe matrix, the specimens were kept during time t� 24 h inair at a temperature T� 293± 2K, followed by conductingexperimental tests.

3. Results and Discussion

)ermal resistance (Martens) of CM was investigated on thefirst stage. As it is known, the thermal resistance is de-termined by the properties of the binder. )e epoxy olig-omer with addition of polyester unsaturated resin was usedas a binder according to the methodology of investigation.)e introduction of the polyester in quantity of q� 10mas.fr.(the content is indicated on 100 weight parts of epoxy resin)leads to increasing the thermal resistance of composites fromT� 341K (matrix based on an epoxy binder) to T�352K(Figure 1).)emonotonic decrease in the thermal resistance(Martens) of developed composite materials was determinedwith the increasing of the concentration of polyester fromq� 20 to 120 mas.fr. (Figure 1, Table 1).

2 Advances in Materials Science and Engineering

�e results can be explained on the basis of the ther-modynamics of polymer mixture [18]. According to thetheoretical positions, the mutual solubility of most polymerpairs over a wide range of temperatures is a tenth or evena hundredth of a percent. A slight di�erence in the chemicalstructure or polarity of the two polymers results in their lowmutual solubility. �at is, the two polymers form a biphasicmixture.�e polyester resin at a slight content is in a discretephase in the epoxy binder. With a further increase in theconcentration of the ENYDYNE H 68372 TAE (from q� 20to 120 mas.fr.), a continuous polyester phase is clearlyformed. In this case, thermophysical properties of CM aredeteriorating which, in our opinion, is due to the excesscontent of the polyester resin in the binder.

For qualitative con�rmation of the results of the ex-periment, microstructure of the fracture surface of thespecimen was studied using an optical microscope. �etypical forms of the surfaces of the studied specimens areshown in Figure 2. It was found that the structure of thematerial surface at the concentration of polyester q � 10 mas.fr. was characterized by a homogeneous structure. �ere areno visible defects in the cross-linking of the two polymers(Figure 2(b)). With an increase of the content of thepolyester binder (q� 60 mas.fr.), the appearance of defects inthe cross-linking of the matrix was observed (Figure 2(c)).�is may be due to the excessive amount of the chemicalbonds of the polyether component of the matrix that do notinteract with the epoxy binder during polymerization andthe formation of temperature stresses. With an increase ofthe concentration to q� 120 mas.fr., a similar propagation ofdefects on the fracture fractogram of the composite materialwas observed (Figure 2(d)).

Similarly, the functional dependence of linear shrinkageon the concentration of the polyester resin in the epoxybinder was observed. �e shrinkage of the matrix based onthe epoxy binder was Δl� 0.31%. It was found that theminimal shrinkage (Δl� 0.06 %) has CM which containENYDYNE H 68372 TAE in quantity of q� 10 mas.fr.Further increasing of concentration of polyester resin leadsto the increasing of linear shrinkage from Δl� 0.10 to 0.48%(Figure 1, Table 1). According to the relaxation theory ofglass transition, the mobility of kinetic units of polymer withthe increasing of the temperature increases as a result ofincreasing of intensity of thermal motion, and also due to thedestruction of the bonds between them in the case of�uctuation collisions [19].

At the next stage, the thermal coe�cient of linear ex-pansion of matrices and their glass transition temperature wasinvestigated. �e singularity of the thermal expansion ofepoxy-polyester matrices was investigated in the followingtemperature ranges: (1) ΔT� 303–323K; (2) ΔT� 303–373K;(3) ΔT� 303–423K; and (4) ΔT� 303–473K (Figure 3). �efollowing values of TCLE were obtained for the matrix:ΔT� 303–323K, α� 6.3×10−5K−1; ΔT� 303–373K,α� 6.8×10−5K−1; ΔT� 303–423K, α� 9.9×10−5K−1; andΔT� 303–473K, α� 10.9×10−5K−1. It was found that at the�rst temperature range, the minimal TCLE has CM with thecontent of PR q� 10 mas.fr. Compared with the initial epoxymatrix, the TCLE decreased by Δα� 4.6×10−5K−1 (Table 2).Analogical dynamics of TCLE values was observed also at thefollowing temperature ranges at the same concentration ofpolyester resin: ΔT� 303–373K, α� 2.2×10−5K−1;ΔT� 303–423K, α� 3.8×10−5K−1; and ΔT� 303–473K,α� 8.9×10−5K−1.�e obtained data can characterize a matrix

10 20 30 40 50 60 70 80 90 100 110

0.55

0.45

0.35

0.25

0.15

0.05

0

352

342

332

322

312

302

∆l (%

)

T (K

)q (mas.fr.)

1

2

Figure 1: �e dependence of thermophysical properties of matrix on the content of polyester resin. 1: thermal resistance (Martens), T; 2:linear shrinkage, Δl.

Table 1: �ermophysical properties of CM with di�erent contents of the polyester resin.

No Content of the polyester resin, q,mas.fr.

�ermal resistance,T, K

Glass transition temperature,Tg, K

Glass transition area,ΔT, K

Shrinkage, Δl,%

1 — 341 311 306–343 0.312 10 352 318 310–355 0.063 20 347 312 309–342 0.104 40 328 309 305–333 0.165 60 318 317 311–323 0.216 80 313 315 307–333 0.247 100 304 317 303–323 0.328 120 302 304 303–317 0.48

Advances in Materials Science and Engineering 3

100 µm

(a)

100 µm

(b)

100 µm

(c)

100 µm

(d)

Figure 2: Microstructure of surfaces of the studied composite materials (with an increase of ×400 times): (a) matrix, (b) 10 mas.fr., (c) 60mas.fr., and (d) 120 mas.fr.

123α×

10–5

(К–1

)

123456789

10

4

20 40 60 80q (mas.fr.)

0 100

11

Figure 3: )e dependence of thermal coefficient of linear expansion on the content of polyester resin at different temperature ranges. 1:ΔT� 303–323K; 2: ΔT� 303–373K; 3: ΔT� 303–423K; 4: ΔT� 303–473K.

4 Advances in Materials Science and Engineering

with concentration of PR q� 10 mas.fr. as a material witha higher cross-linking density, compared with epoxy [19].With an increase of the concentration of polyester from q� 20to 100 mas.fr., an increase of the TCLE was observed at alltemperature ranges of the study (Figure 3; Table 2). As a resultof the studies, it was confirmed that the dependence of TCLEon temperature is nonlinear. When the polyester resin isintroduced over q� 100 mas.fr., the sharp falloff of TCLE wasobserved. In our opinion, this is a consequence of the de-structive processes taking place in the composite: the de-struction of spatial structures, the change in the nature andintensity of the intermolecular interaction, and the destructionof intermolecular bonds.

As it is known, one of the important performance prop-erties of CM is a glass transition temperature (Tg). )e Tg

determines the upper permissible range of operating tem-peratures and is the edge of the glassy and highly elastic states.)e dilatometric curves which image the dependence of rel-ative linear deformation of the specimens on the temperaturewere investigated. It was experimentally found that the glasstransition temperature of the epoxy matrix is Tg � 311K andthe maximal value Tg � 318K is designated for the compositewith content of PR in quantity of q� 10mas.fr. (Figure 4). Itwas detected that the glass transition temperature shifts to lowtemperatures (Figure 4, Table 1) with the further increasing ofconcentration of polyester resin (from q� 20 to q� 120 mas.fr.). Evidently, the increasing of glass transition temperature islinearly related to the degree of cross-linking of the polymermatrix [20]. )erefore, it was considered that the increasing ofthe concentration of PR over q� 10 mas.fr. decreases thenumber of physicochemical bonds in the spatial polymernetwork. It leads to decreasing of Tg and deterioration ofthermophysical properties of CM. )e results of the in-vestigation of the glass transition temperature accord withvalues of the thermal resistance and TCLE. Also, it should benoted that it correlates with previous data of the investigationof adhesion and physicomechanical properties of CM. )isindicates the reliability of the obtained results of the study.

4. Conclusion

)e thermophysical properties of epoxy matrix have beeninvestigated at different concentrations of polyester resin. It

was found that the epoxy matrix with the content ofpolyester resin ENYDYNE H 68372 TAE in quantity ofq� 10 mas.fr. is characterized by maximal values of thethermophysical properties. In addition, the following resultswere found:

(1) )e introduction of the polyester resin in the epoxybinder at a low concentration (q� 10mas.fr.) leads toincreasing of the thermal resistance of the matrixfrom T� to T� 352K and decreasing of the linearshrinkage of the composite from Δl� 0.31% toΔl� 0.06%.

(2) Value of indicators of thermal coefficient of linearexpansion at all the studied temperatureranges decreases compared with the indicators ofTCLE of epoxy matrix. Minimal values of the in-dicators of TCLE were obtained at concentrationof polyester resin q� 10 mas.fr. at the appropriateranges: ΔT� 303–323K, α� 1.7×10−5K−1; ΔT�

303–373K, α� 2.2×10−5K−1; ΔT� 303–423K,α� 3.8×10−5K−1; ΔT� 303–473K, α� 8.9×10−5K−1.

(3) Glass transition temperature Tg of the developedmaterial increases from Tg � 311K to Tg � 318K.)is is caused by increasing of the degree of cross-linking of the matrix.

)e obtained results of investigation of thermophysicalproperties of composite materials correlate with data ofinvestigation of the adhesion and physicomechanical per-formance. )is confirms the expedience of the use ofpolymer products based on the developed CM for therestoration of transport details.

Table 2:)e values of TCLE depending on the content of PR at thedifferent temperature ranges.

Content of PR, q, mas.fr.

)ermal coefficient of linearexpansion, α× 10−5, K−1

Temperature test ranges, ∆T, K303–323 303–373 303–423 303–473

— 6.3 6.8 9.9 10.910 1.7 2.2 3.8 8.920 2.0 2.4 4.0 9.140 1.9 2.5 5.9 10.760 2.4 2.9 6.0 10.680 3.4 3.5 5.9 10.5100 3.5 3.8 6.5 11.0120 2.5 2.8 3.8 8.1

303 323 343 363 383 403 423 443 463 4830

ε (%

)

T (K)

0.2

0.4

0.6

0.8

1.0

1.2

1.4

1.6

1.8

Matrixq = 10 mas.fr.q = 20 mas.fr.q = 40 mas.fr.q = 60 mas.fr.

q = 80 mas.fr.q = 100 mas.fr.q = 120 mas.fr.

А – glass transition temperatureof material (Тg).

А

Figure 4: Dilatometric curves of the matrices at the differentcontent of polyester resin.

Advances in Materials Science and Engineering 5

Data Availability

)e data used to support the findings of this study areavailable from the corresponding author upon request.

Conflicts of Interest

)e authors declare that they have no conflicts of interest.

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