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232 CHEMICAL PROBLEMS 2021 no. 4 (19) ISSN 2221-8688
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UDC 678.01: 541.68
PHYSICAL-MECHANICAL PROPERTIES OF NANOCOMPOSITES BASED ON GRAPHITE AND MODIFIED POLYOLEFINS
Kh.V. Allahverdiyeva
Institute of Polymer Materials of the National Academy of Sciences of Azerbaijan S. Vurgun str., 124, AZ 5004, Sumgait, Azerbaijan; e-mail: [email protected]
Received 01.08.2021 Accepted 04.12.2021
The influence of the graphite concentration on the main physical-mechanical properties of nanocomposites based on such polyolefin as high density polyethylene, low density polyethylene and polypropylene is considered. Properties such as tensile yield stress, ultimate tensile stress, and ultimate bending strength, elongation at break, heat resistance, flexural strength, MFI, and melting points are analysed. To improve the compatibility of the mixed components of the mixture, we used an Exxelor PO1040 compatibilizer for all grades of polyethylene and Exxelor PO1020 for polypropylene. Graphite was introduced into the composition ofpolyolefin at the following concentrations: 1.0, 3.0, 5.0, 10, 15, 20, and 30 wt%. As a result of the research, it was found that the introduction of graphite into the composition of polyolefin was accompanied by an improvement in strength characteristics with maximum at various concentrations. For high density polyethylene, the maximum values of strength characteristics are observed at 3.0 wt%, for low density polyethylene at 10 wt%, and for polypropylene at 5.0 wt% content of graphite. It revealed that such a difference in the value of the threshold concentration of graphite which provides the maximum value of strength indicators,was directly related to the degree of crystallinity of the polymer matrix. Keywords: tensile yield stress, ultimate tensile stress, ultimate bending strength, elongation at break, heat resistance, MFI, crystallinity degree DOI: 10.32737/2221-8688-2021-4-232-240
Introduction
To expand application areas of industrial polyolefin, low density polyethylene (LDPE), high density polyethylene (HDPE), polypropylene (PP), various methods are applied to modify their structure and properties using fillers, plasticizers, stabilizers, nucleators, etc. [1-3]. Through changing the concentration of the above modifiers in the composition of polyolefins, one might significantly affect changes in the supra-molecular structure and properties of composite materials. In recent years, the interest of researchers in the development of nanocomposites based on
polyolefins and mineral fillers has significantly increased, following which, with a minimum concentration of the latter, it became possible to obtain materials with predetermined properties [3-6]. However, despite the above, the literature provides very contradictory information on the structure and properties of nanocomposites based on graphite and polyolefins [7].
In this regard, in this work, the main attention is paid to the study of the effect of graphite concentration on the main physico-mechanical characteristics of polyolefin-based nanocomposites.
Experimental part
HDPE is characterized by the following break - 435%, density - 957 kg/m3, Vicat heat properties: ultimate tensile stress - 31.3 MPa, resistance - 139°C, melting point - 145°C, flexural strength - 34.4 MPa, elongation at
CHEMICAL PROBLEMS 2021 no. 4 (19) www.chemprob.org
crystallinity - 82%, melt flow index (MFI) -4.65 g/10min.
LDPE has the following properties: ultimate tensile stress - 13.1 MPa, flexural strength - 16.2 MPa, elongation at break -720%, Vicat heat resistance - 85°C, melting point - 101°C, crystallinity - 59%, density -931 kg/m3, MFI - 2.9 g/10min at a temperature of 190°C and a load of 5.0 kg.
PP is characterized by the following properties: ultimate tensile stress - 33.0 MPa, flexural strength - 35.0 MPa, elongation at break - 130%, Vicat heat resistance - 160°C, melting point - 169°C, density - 903 kg/m3, crystallinity - 65%, MFI - 3.6 g/10min.
Compatibilizer (PEMA) - high density polyethylene functionalized with maleic anhydride (MA) - Exxelor P01040 for all grades of polyethylene and Exxelor P01020 for polypropylene. The MA grafting degree in HDPE is 5.6 wt%.
Graphite (Gr) as one of the allotropic modifications of carbon has a layered structure. The layers of the crystal lattice, located relative to each other, form a number of structural modifications, with symmetry from hexagonal
to trigonal. The layers are slightly wavy, almost flat, composed of hexagonal layers of carbon atoms. As an object of research, we used graphite with a particle size of 80-110 nm.
In order to modify the properties of the above polyolefins, up to 5.0 wt% of PEMA was introduced into their composition on hot rollers at a temperature of 170° C, and then graphite nanoparticles were added to the molten polymer mixture in parts. The amount of graphite in the HDPE composition varied within 1.0, 3.0, 5.0, 10, 15, 20, 30 wt%.
The particle size of the graphite was determined on an STA PT1600 Linseis Germany instrument.
Heat resistance was determined according to Vica.
The MFI of polymeric materials was determined on a capillary rheometer of the MELT FLOW TESTER, CEAST MF50 (INSTRON, Italy) at a temperature of 190°C and a load of 5 kg.
The melting point was estimated from the data of the derivatographic analysis of the Paulik-Paulik-Erdey system.
Results and Discussion
Carrying out complex investigations to study the effect of graphite on the physico-mechanical properties of polyolefins was due to the fact that it has a noticeable effect on the electrical conductivity of polymers, and on the other hand, it opens up great opportunities for significant reduction in the abrasion and the coefficient of friction of composite materials [79]. At the same time, the literature contains fragmentary information on the study into physical-mechanical characteristics of graphite-filled polymer composites. Research on the effect of graphite nanoparticles on properties is very limited. Also, it is also known that polyolefins haven't well enough compatibility with mineral fillers and graphite. In this regard, in this work we will try to show a systematic approach to the study of the role of graphite in the formation of the basic physical-mechanical and physical-chemical properties of nanocomposites in compatibilizers [10, 11].
For this purpose, Table 1 shows the
results of the study into the effect of graphite concentration on the properties of HDPE modified with compatibilizer. Properties such as tensile yield stress, ultimate tensile stress, elongation at break, heat resistance, ultimate bending strength, melting point, and melt flow index (MFI) were investigated. As can be seen from the Table, the main attention is focused not only on the study into the concentration dependence of the properties of HDPE on graphite but also the effect of such a compatibilizer as PEMA on the compatibility of the mixed components. Data on the effect of sulphur on the HDPE vulcanization process are presented to be detailed below.
From a comparative analysis of the data presented in Table 1, it can be established that the introduction of 2 wt% PEMA in the composition of the initial HDPE leads to a slight decrease in the strength parameters which is apparently associated with plasticizing effect of the latter (sample 2). As the concentration of
graphite in HDPE increases, there is a slight increase in the tensile yield stress and ultimate tensile stress with a maximum at 3.0 wt% graphite content (sample 4). A further growth in the concentration of graphite leads to a natural decrease in strength indicators and elongation at break of nanocomposites (sample 5-9). When the concentration of graphite exceeds 10 wt%, a
sharp deterioration in the elongation at break is observed, up to brittle fracture at its 20-30 wt% content (sample 8-9).. The very fact that the values of the tensile yield strength and ultimate tensile stress are equal is a confirmation of the brittle fracture of the considered samples of nanocomposites.
Table 1. Physical-mechanical properties of nanocomposites based on HDPE, graphite (Gr) and
PEMA
№ Composite formulation, Tensile Ultimate Elongation Vicat heat Flexural
% yield stress, tensile at break, % resistance strength,
MPa stress, MPa °C MPa
1 HDPE 32.3 31.3 435 139 34.4
2 HDPE+2PEMA 32.0 32.8 105 139 33.5
3 HDPE+1Gr 32.5 31.6 150 140 34.1
4 HDPE+3Gr 32.9 31.8 85 140 34.4
5 HDPE+5Gr 32.0 31.5 40 141 35.0
6 HDPE+10Gr 29.3 28.8 25 141 35.6
7 HDPE+15Gr 28.2 27.6 15 142 35.8
8 HDPE+20Gr 27.7 27.7 - 142 35.0
9 HDPE+30Gr 25.1 25.1 - 142 34.0
10 HDPE+2PEMA+1Gr 33.3 32.9 160 139 34.5
11 HDPE+2PEMA+3Gr 35.8 34.5 110 140 36.3
12 HDPE+2roMA+5Gr 34.6 33.6 70 141 38.8
13 HDPE+2PEMA+10Gr 33.9 32.8 50 142 39.6
14 HDPE+2PEMA+15Gr 31.4 31.0 40 142 39.5
15 HDPE+2PEMA+20Gr 29.6 29.2 30 143 38.6
16 HDPE+2PEMA+30Gr 28.0 27.6 20 144 37.0
17 HDPE+2PEMA+5Gr+5S 36.3 35.4 75 143 38.7
18 HDPE+2PEMA+10Gr+5 S 34.1 33.8 60 144 39.0
S - sulfur
However, the introduction of PEMA into the composition of graphite-containing HDPE nanocomposites made it possible to look differently at the general picture of changes in the physico-mechanical properties of nanocomposites. Analysing the data presented in Table-1, it can be noted that regardless of the concentration of graphite the introduction of PEMA into the composition of nanocomposites contributes to significant improvement in the complex of their physical-mechanical properties, in particular the tensile yield stress, ultimate tensile stress (sample 10-16), and elongation at break. According to the data obtained, the maximum strength in the compatibilized nanocomposites falls on a sample with 3.0 wt% graphite content (sample
11). It is characteristic that even at 20-30 wt% filler content, nanocomposites do not undergo brittle fracture (samples 15-16). Another indicator of the strength of nanocomposites is that the ultimate bending strength almost constantly increases with an increase in the concentration of graphite in the HDPE composition. Only with a high content of graphite (over 20 wt%) there is a slight decrease in the value of this indicator.
Following the comparison of data on the heat resistance of nanocomposites, it becomes obvious that the introduction of graphite is accompanied by rise in their heat resistance in the presence of PEMA from 139 to 144°C. An increase in the value of this indicator by 5.0°C might be due to the existence of an adhesive
contact in the polymer-filler system and indicates the physical thermal stability of the spherulite structure of nanocomposites. In this case, the use of PEMA, apparently, makes it possible not only to improve the compatibility of the mixed components of the mixture, but also contributes to the orientation of the macro-chains of the compatibilizer and the polymer matrix on the developed surface of graphite nanoparticles. It is this circumstance that can interpret the appearance of heterogeneous nucleation centers. The melting point of
nanocomposites was investigated by derivategraphic analysis. According to the data obtained, the melting point is practically independent of the graphite concentration and is equal to the melting temperature of the initial HDPE - 145° C. Only at a graphite concentration of 20 wt% and higher is the melting peak shifted to 146°C.
At the same time, account has to be taken of the fact that the introduction of 5.0 wt% graphite into the HDPE composition led to the rise in the MFI value from 4.65 to 6.35 g/10 min. This is explained as being due to the fact that graphite has a layered structure, which has a lubricating effect that improves the melt flow of the nanocomposites.
It seemed interesting to consider the effect of sulfur on the nature of changes in the physico-mechanical properties of
nanocomposites. It is quite obvious that here we are not talking about the full-fledged vulcanization of the polymer matrix, since HDPE lacks a sufficient number of vinyl groups. These are mainly terminal vinyl groups and partially trans-vinylene double bonds. As can be seen from table 1, the introduction of 5.0 wt% sulfur leads to an improvement in all physico-mechanical characteristics (sample 1718). A slight increase in properties in comparison with samples 12-13 indicates, first of all, a partial crosslinking of macro-chains,
and on the other hand, a decrease in the MFI of HDPE+5.0 wt% graphite nanocomposites (sample 12) from 6.35 to 4.78 g/10 min directly accounts for the formation of a sparsely reticulated spatial structure with a subsequent increase in the viscosity of the melt.
Table 2 shows the results of research into physical-mechanical properties of
nanocomposites based on LDPE and graphite. Comparing the data in this Table makes it possible to establish that the properties of nanocomposites change according to a certain pattern. So, for example, in samples 3-9, with an increase in the concentration of graphite from 1.0 to 30 wt%, the maximum value of the tensile yield stress and ultimate tensile stress appears at its 10 wt% content. As can be seen from the Table, the elongation at break of nanocomposites is very sensitive to the concentration of graphite. Even at 1.0 wt% content, a noticeable decrease in elongation at break from 720 to 200% is observed (sample 3). A rather sharp deterioration in strength indicators and elongation at break was recorded at a graphite concentration of more than 15 wt%. At 20 wt% graphite content in the LDPE composition, the sample becomes practically brittle and loses its ability to uniaxial deformation, as a result of which the tensile yield stress becomes equal to the ultimate tensile stress. In comparison with the initial LDPE, the heat resistance of nanocomposites at 30 wt% graphite content rises by 3°C, i.e. from 85 to 88°C. Ultimate bending strength constantly grows as the graphite content grows up to 15 wt%. At the same time, according to the data of derivate-graphic analysis, the melting temperature of nanocomposites at 30 wt% graphite concentration rises from 101 to 102°C. Thus, in LDPE-based nanocomposites, the melting point remains practically unchanged depending on the graphite content.
Table 2. Physical-mechanical properties of nanocomposites based on LDPE, Gr and PEMA
№ Composite formulation, Tensile Ultimate Elongation Vicat heat Flexural
% yield stress, tensile at break, % resistance strength,
MPa stress, MPa °C MPa
1 LDPE 12.2 13.1 720 85 16.2
2 LDPE+2PEMA 11.0 12.5 305 85 16.5
3 LDPE+1Gr 12.7 13.9 200 85 16.9
4 LDPE+3Gr 14.6 14.0 115 85 17.4
5 LDPE+5Gr 15.1 14.5 60 87 18.0
6 LDPE+10Gr 15.6 15.0 35 87 19.5
7 LDPE+15Gr 15.2 14.8 25 87 21.8
8 LDPE+20Gr 11.7 11.7 10 88 20.2
9 LDPE+30Gr 9.5 9.5 - 88 20.4
10 LDPE+2PEMA+1Gr 13.6 14.2 230 85 19.6
11 LDPE+2PEMA+3Gr 15.4 15.0 160 85 21.2
12 LDPE+2PEMA+5Gr 16.1 15.3 90 86 23.8
13 LDPE+2PEMA+10Gr 17.0 16.2 60 87 24.6
14 LDPE+2PEMA+15Gr 17.5 16.8 40 87 25.5
15 LDPE+2PEMA+20Gr 14.6 14.0 30 89 25.6
16 LDPE+2PEMA+30Gr 12.2 11.9 20 89 26.0
17 LDPE+2PEMA+5Gr+5S 16.9 15.7 75 90 26.8
18 LDPE+2PEMA+10Gr+5 S 17.6 16.5 60 92 27.6
S - sulfur
It has been experimentally established that the introduction of graphite into the LDPE composition (samples 3-9) is accompanied by rise in MFI in the following sequence 3.2, 4.0, 5.0, 5.8, 6.9, 5.5, and 4.8 g/10min. Analysing these data, it can be unambiguously asserted that, as in the case of HDPE, the graphite, due to its layered structure, improves the melt flow. The maximum MFI value is observed for a nanocomposite with 15 wt% graphite content. The existence of a maximum MFI in the concentration dependence of nanocomposites testifies to the fact that in the process of supersaturation, nanoparticles agglomerate in the melt which, to a certain extent, can result in increase in the viscosity of the polymer matrix accompanied by a slight decrease in the MFI. But, despite this, the MFI of nanocomposites always remains higher than that of the initial LDPE.
It is characteristic that the introduction of PEMA into the composition of nanocomposites improves all the physical-mechanical properties of LDPE nanocomposites. The latter circumstance is explained as being due to the fact that the introduction of PEMA actually exhibits the ability to improve the compatibility and adhesive contact of nanoparticles with a polymer matrix. This circumstance becomes possible due to the uniform dispersion of nanoparticles throughout the entire volume of the polymer matrix which minimizes the
probability of their agglomeration, so the samples do not lose plasticity even at 30 wt% graphite content (sample 16) [16].
During sulfur vulcanization of nanocomposites (samples 17 and 18), the peak of their melting temperature at 5.0-10 wt% graphite content rose to 103°С. At the same time, all strength characteristics, elongation at break and heat resistance increased. These noticeable changes in physical-mechanical properties in the process of partial sulfur vulcanization make it possible to assert the formation of a sparsely reticulated spatial structure in the polymer matrix. In contrast to HDPE, the number of terminal, trans-vinylene and vinylidene double bonds in LDPE is relatively higher. It is possible that this very circumstance confirms some significant changes in the properties of cross-linked nanocomposites [16, 17]. It is known that in the process of crosslinking of a polymer matrix, a drop in the MFI of composites is observed. In particular, we found that after sulfur crosslinking, the MFI of nanocomposites with 5.0 and 10 wt% graphite content (samples 17-18) decreases, respectively, from 5.0 and 5.8 g/10 min to 4.2 and 5.0 g/10 min, which confirms the occurrence of partial crosslinks in the structure of the polymer matrix.
Another representative of the class of polyolefins is isotactic polypropylene (PP), which, due to a number of structural features, is
widely used in various industries. In this respect, it seemed interesting to consider the possibility of changing its properties by introducing graphite nanoparticles. The results of studying the properties of nanocomposites
S
The differences are manifested mainly in the quantitative expression of the data. For example, as the concentration of graphite in the PP composition rises in the absence of a compatibilizer, a change in the strength characteristics (tensile yield stress, ultimate tensile stress) is observed with a maximum at 5.0 wt% filler content. Accordingly, a sharp decrease in the elongation at break is observed already at 3.0 wt% graphite content. And this is quite understandable, since when using nano-scale particles, their number per unit volume is hundreds of times greater than when using the same amount of conventional dispersed fillers. As in the case of using HDPE and LDPE as a polymer matrix, the introduction of graphite (samples 3-9) into the PP composition leads to
The introduction of PEMA has a positive effect on improving the compatibility of the mixture components and, accordingly, on the physical-mechanical characteristics of PP
are shown in Table 3. As can be seen from this Table, the concentration of graphite in the PP matrix has a significant effect on the main physical and mechanical properties of nanocomposites.
rise in the MFI of nanocomposites in the following sequence: 4.1, 4.8, 6.2, 7.9, 8.2, 6.6, 4.2 g/10 minutes. According to these data, the maximum MFI value is observed for specimens with 15 wt% graphite content (8.2 g/10 min). There are grounds to believe that such a sharp decrease in the MFI of the samples after the maximum confirms once again our arguments over the existence of a peculiar threshold concentration of graphite after which the spontaneous formation of agglomerates of filler nanoparticles is observed which results in a regular increase in the viscosity of the nanocomposites. Moreover, the MFI of nanocomposites is always higher than that of the initial PP (3.6 g/10 minutes).
nanocomposites. In this case, the point is not about thermodynamic, but technological compatibility which ensures uniform miscibility and the existence of adhesive contact between
Table 3. Physical-mechanical properties of nanocomposites based on PP, Gr and PEMA
№ Composite Tensile yield Ultimate Elongation Vicat heat Flexural
formulation, stress, MPa tensile at break, % resistance, strength,
% stress, MPa °C MPa
1 PP 34.9 33.0 130 160 35.0
2 PP+2PEMA 34.2 32.5 140 160 34.6
3 PP+1Gr 35.3 33.6 110 160 36.7
4 PP+3Gr 36.6 35.2 75 160 37.4
5 PP+5Gr 38.1 36.5 50 161 38.0
6 PP+10Gr 35.2 34.6 25 163 39.6
7 PP+15Gr 31.5 31.2 15 163 41.4
8 PP+20Gr 27.7 27.7 - 165 39.3
9 PP+30Gr 25.5 25.5 - 165 38.5
10 PP+2PEMA+1Gr 36.7 34.5 120 160 37.6
11 PP+2PEMA+3Gr 37.4 35.6 85 160 39.2
12 PP+2PEMA+5Gr 39.7 38.1 60 160 40.8
13 PP+2PEMA+10Gr 36.5 36.0 35 162 41.6
14 PP+2PEMA+15Gr 33.8 33.1 25 163 43.5
15 PP+2PEMA+20Gr 30.6 30.4 15 165 43.1
16 PP+2PEMA+30Gr 28.3 28.2 10 166 40.2
17 PP+2PEMA+5Gr+5S 41.4 39.8 85 162 42.6
18 PP+2PEMA+10Gr+5S 38.5 36.9 60 164 43.8
- sulfur
the components of the mixture. Table 3 shows the results of a research into the effect of sulfur crosslinking on the nature of changes in physical-mechanical properties (samples 17-18). It can be noted that in this case, the use of sulphur as a crosslinking agent contributes to a noticeable improvement in the main physical-mechanical properties of nanocomposites. A drop in the MFI of these samples from 6.2 and 7.9 g/10 minutes, respectively, to 5.1 and 6.5 g/10 minutes reaffirms the probability of crosslinking in the PP structure. From a comparative analysis of the data shown in Tables 1-3, it can be established that the maximum value of the strength characteristics in HDPE is achieved at 3.0 wt%, in LDPE at 15 wt%, and in PP at 5.0 wt% graphite content. Of course, the type of polyolefin and the degree of its crystallinity are fundamental factors that determine the optimal content of graphite in its composition. For example, in HDPE which is characterized by a linear macro-chain structure, the degree of crystallinity is 82%, in LDPE -59%, and in PP - 65%. From this it follows that the lower the crystallinity of the polyolefin, the greater the "vacant free volume" in the inter-spherolite region for filling with graphite nanoparticles.
Based on the foregoing, it can be concluded that the use of graphite as a filler makes it possible to obtain a whole set of nanocomposites with predetermined properties. This circumstance allows us to assert the receipt of a high-tech construction material intended for use in special fields of engineering and technology. Based on the data obtained, it can be assumed that the considered nanocomposites
are characterized by satisfactory MFI values which allow them to be processed by the most common processing methods such as extrusion and injection moulding.
Thus, according to the results of the experimental studies performed, one can come to the conclusions as follows:
1. The effect of graphite concentration on physical-mechanical properties of nanocomposites based on HDPE, LDPE, and PP, such as tensile yield strength, ultimate tensile stress, elongation at break, heat resistance, flexural strength, melting point and MFI, has been studied. It found that, depending on the type of polyolefin used, the limiting values of the graphite concentration change at which comparatively high values of the strength characteristics of nanocomposites are observed for HDPE at 3.0 wt%, LDPE at 10 wt% and PP at 5.0 wt% graphite content.
2. It was found that the introduction of compatibilizer - PEMA into the composition of graphite-filled polyolefins leads to significant improvement in the complex of physical-mechanical properties of nanocomposites.
3. The influence of sulfur on the character of changes in the properties of nanocomposites is considered. It is shown that the introduction of sulfur into the composition of polyolefins leads to some improvement in the properties of composite materials while maintaining the MFI at a satisfactory level, sufficient for their processing by extrusion and injection molding.
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QRAFiT VO MODiFiKASiYA OLUNMU§ POLiOLEFiNLOR OSASINDA NANOKOMPOZiTLORiN FiZiKi-MEXANiKi XASSdLdRJ
X.V. Allahverdiyeva
Azarbaycan Milli Elmlar Akademiyasinin Polimer Materiallari institutu S. Vurgun kugasi, 124, AZ 5004, Sumqayit, Azarbaycan; e-mail: [email protected]
Qrafitin miqdarinin yuxari sixliq polietileni, a§agi sixliq polietileni va polipropilen kimi poliolefinlar asasinda nanokompozitlarin asas fizki-mexaniki xassalarina tasiri nazardan kegirilmi§dir. Dartilmada axiciliq haddi, dartilmada mohkamlik haddi, ayilmada mohkamlik haddi, nisbi uzanma, istiliyadavamliliq, ayilmada mohkamlik, arintinin axiciliq haddi va arima temperaturu kimi xassalar tadqiq edilmi§dir. Qari§igin qari§dirilan komponentlarinin uygunlugunun yax§ila§dirilmasi ugun butun polietilen markalari ugun Exxelor Р01040 markali, polipropilen ugun is a Exxelor 1020 markali kompatibilizatordan istifada edilmi§dir. Poliolefnlarin tarkibina qrafit a§agidaki miqdarlarda daxil edilmi§dir: 1.0, 3.0, 5.0, 10, 15, 20, 30 kutla%. Aparilmi§ tadqiqatlar naticasinda muayyan olunmu§dur ki, qrafitin poliolefnlarin tarkibina daxil edilmasi onun muxtalif miqdarlarinda maksimumun alda edilmasi ila mohkamlik xususiyyatlarinin yax§ila§masi ila mu§ayat olunur. Yuxari sixliqli polietilen ugun mohkanlik xususiyyatlarinin maksimal qiymati qrafitin 3.0 kutla%, a§agi sixliqli polietilen ugun 10 kutla%, polipropilen ugun isa 5.0 kutla% miqdarinda mu§ahida olunur. Gostarilmi§dir ki, mohkamlik gostaricilarinin maksimal qiymatini tamin edan qrafitin bu hadd miqdarinin qiymatinda bela farq birba§a polimer matrisanin kristalliklik daracasi ila baglidir. Agar sozfor: dartilmada axiciliq haddi,dartilmada mohkamlik haddi, ayilmada mohkamlik haddi nisbi uzanma, istiliyadavamliliq, arintinin axiciliq gostaricisi, kristalliklik daracasi.
ФИЗИКО-МЕХАНИЧЕСКИЕ СВОЙСТВА НАНОКОМПОЗИТОВ НА ОСНОВЕ ГРАФИТА И МОДИФИЦИРОВАННЫХ ПОЛИОЛЕФИНОВ
Х.В. Аллахвердиева
Институт Полимерных Материалов Национальной Академии Наук Азербайджана улица С. Вургуна, 124, AZ 5004, Сумгаит, Азербайджан; e-mail: [email protected]
Рассмотрено влияние концентрации графита на основные физико-механические свойства нанокомпозитов на основе таких полиолефинов, как полиэтилен высокой плотности, полиэтилен низкой плотности и полипропилен. Исследованы такие свойства, как предел текучести при растяжении, разрушающее напряжение, предел прочности на изгиб, относительное удлинение, теплостойкость, прочность на изгиб, показатель текучести расплава и температура плавления. Для улучшения совместимости смешиваемых компонентов смеси использовали компатибилизатор марки Exxelor Р01040 для всех марок полиэтилена и Exxelor Р01020 для полипропилена. Графит вводили в состав полиолефинов в следующих концентрациях: 1.0, 3.0, 5.0, 10, 15, 20, 30 %масс. В результате проведенных исследований установлено, что введение графита в состав полиолефинов сопровождается улучшением прочностных характеристик с максимумом при различных его концентрациях. Для полиэтилена высокой плотности максимальные значения прочностных характеристик наблюдаются при 3.0 %масс., для полиэтилена низкой плотности - при 10%масс., а для полипропилена - при 5.0 %масс. содержании графита. Показано, что такое различие в значении пороговой концентрации графита, обеспечивающей максимальное значение прочностных показателей, напрямую связано со степенью кристалличности полимерной матрицы. Ключевые слова: предел текучести при растяжении, разрушающее напряжение, предел прочности на изгиб, относительное удлинение, теплостойкость, показатель текучести расплава, степень кристалличности.
