Ecology UDC 691.175.2 Розглянута можливість збільшення об'ємів DOI: 10.15587/1729-4061.2019.163656 утилізації відходів буріння шляхом викори- стання їх в якості наповнювача для виготов- лення полімерного композиційного матеріалу. В результаті проведених досліджень проведе- IDENTIFICATION на модифікація вторинного поліетилену висо- кої густини відпрацьованим буровим розчином у OF PROPERTIES OF вигляді частинок високодисперсного наповнюва- ча. Одержані полімерні композити вторинного RECYCLED HIGH- поліетилену високої густини, які були наповнені відходами бурового виробництва із вмістом від- ходів до 30 %. В результаті дослідження виявле- DENSITY POLYETHYLENE ні закономірності зміни ударної в'язкості, руй- нуючої напруги при вигині і водопоглинання від COMPOSITES WHEN FILLED вмісту твердої фази відпрацьованого бурового розчин у(ТФВБР) у вторинному полімері. WITH WASTE MUD SOLIDS Показано, що при введенні до складу вто- ринного поліетилену високої густини ТФВБР N . R y k u s o v a у вигляді частинок високодисперсного напов- нювача відбувається значне підвищення їх міц- Pаstgraduate student ності без значного погіршення водопоглинання Department of Chemical Engineering and Industrial Ecology** (до 2,9 % при наповненні відходами до 30 %). E-mail: n_rykusova@ukr.net Встановлено, що оптимальний вміст відхо- O . S h e s t o p a l o v дів бурового виробництва у складі полімерних PhD, Associate Professor* композитів на основі вторинного поліетилену високої густини складає 20 % мас. При цьому E-mail: shestopalov.it@khpi.edu.ua досягаються максимальні значення ударної в'яз- V . L e b e d e v кості і руйнуючої напруги при вигині для компо- PhD, Associate Professor зиції з ТФВБР на основі бентонітової глини до Department of Technology of Plastics and 63,3 кДж/м2 і 200,1 МПа, а для композиції з соле- 2 Biological Active Polymer**вою ТФВБР до 38,1 кДж/м і 207,4 МПа відпо- відно. Одержані полімерні композити за своїми T . T y k h om y r o v a експлуатаційними характеристиками перевер- PhD, Associate Professor* шують відомі аналогічні полімерні матеріали з E-mail: tatikh@i.ua використанням таких наповнювачів як тальк і G . B a k h a r i e v а каолін. Це дозволяє рекомендувати сумісну ути- лізацію відходів буріння і полімерних відходів PhD, Associate Professor Ключові слова: композит полімерний, напов- Department of Occupational Safety and Environmental** нювач, відпрацьований буровий розчин, модифі- E-mail: baharevaann@gmail.com кація структури, ударна в'язкість, руйнуюча *Department of Chemical Technique and Industrial Ecology** напруга **National Technical University "Kharkiv Polytechnic Institute" Kyrpychova str., 2, Kharkiv, Ukraine, 61002 1. Introduction method of WM recycling is partial use in the production of building materials [3]. But this method has not found broad In well-drilling, drilling mud is used, which, after passing application. the technological cycle, most adversely affects the environ- One of the promising areas of WM recycling can be ment than any other drilling waste. Muds are polydisperse the use as a fine filler in the production of polymer com- heterogeneous systems, contain both coarse and colloidal posites. particles (more than 90 % of waste mud solids (WMS) No less urgent problem is polymer waste recycling. It is represent a fraction of less than 20 microns). According to known that recycled polymers do not fully possess the pri- the composition of the dispersion medium and the dispersed mary operational properties. At the same time, it is consid- phase, they are divided into water-based muds (clay, carbon- ered that irreversible relaxation processes take place in them ate, sulfate) and non-aqueous (hydrocarbon) muds [1]. To during the use of polymer products. achieve the required properties of muds, various chemical Very relevant today is the production of recycled poly- reagents are used [2]. olefin (polyethylene and polypropylene) polymer composites After the completion of drilling, waste mud (WM) is using disperse waste of various productions, both organic discharged in mud collectors (mud pits) and is subject to and inorganic. By changing the composition and structure of disposal. When drilling each gas well, an average of about the recycled polymer matrix, it seems possible to regulate the 500 m3 of WM is formed. Mud collectors or mud pits that quality characteristics of polymer waste composites within a are built to store drilling waste also remain potentially envi- fairly wide range. ronmentally hazardous after well construction. Therefore, the relevant area of research is the develop- The issue of the possibility of recycling and treatment ment of recycled polymer composites with structural modi- of drilling fluids is not fully resolved. The most common fication using industrial waste, such as WM. 55  N. Rykusova, O. Shestopalov, V. Lebedev, T. Tykhomyrova, G. Bakharievа, 2019 Eastern-European Journal of Enterprise Technologies ISSN 1729-3774 2/10 ( 98 ) 2019 2. Literature review and problem statement In [16], low-density polyethylene composites filled with talc and chalk are investigated. The optimal filler content of One of the widely used methods of structural modifica- 50 % in the composite is determined. tion of the recycled polymer matrix is the introduction of In [17], the composite based on unsorted crushed waste various mineral fillers [4]. In this case, it is possible not only of thermoplastic polymers – LDPE, HDPE in an amount to significantly reduce the cost of the composite, but also to of 10–50 wt % with the addition of disperse clay with a improve a number of physicomechanical characteristics. humidity of 8–12 % is proposed. The technical result of the The publication [5] shows the possibility to reuse invention consists in reducing energy consumption, simpli- non-metals of recycled printed circuit boards as reinforc- fying the method and obtaining material for the production ing fillers in polypropylene composites. An increase in the of walling, finishing and road-building composites for civil strength of composites to 133 % is revealed and the use of no engineering. more than 30 % of filler is recommended. In accordance with [18], thermoplastic (polyethylene, In [6], the possibility of increasing recycling volumes of polypropylene, polystyrene, etc.) polymer composite using production waste of alumina – red mud by using as a filler disperse barium sulfate is developed. By selective surface for the polymer composite production is considered. The modification of disperse barium sulfate, the operational developed composites with a filler content of 55–75 wt % properties of the composite can be controlled. of red mud had a density within 2,200–2,500 kg/m3, water Thus, the creation of composites using industrial waste absorption within 3.00–5.02 % and compressive strength is a common practice worldwide. At the same time, the cre- was over 17 MPa. ation of composite mixes with the introduction of any filler However, this method of polymer modification does not requires research into the properties of new composites. always provide the desired results. Most fillers are insuffi- From the analysis, it follows that additional infor- ciently moistened with the polymer matrix, which certainly mation is needed regarding changes in the properties of affects their basic physicomechanical properties [7]. In this high-density polyethylene when it is reinforced with solids regard, the most widespread technique is the introduction of of different muds. silane coupling agents into composites, intended for targeted improvement of the adhesive interaction at the polymer-filler interface. 3. The aim and objectives of the study Attention is drawn to research on the use of various industrial wastes as fillers of polymer composites. Thus, The aim of the study was to identify improvements in the [8] considers modification of the composite with calcium properties of recycled high-density polyethylene composites stearate. According to the authors’ recommendations, the by filling with waste mud solids. This will make it possible to filler share in composites is 5–20 wt %, which limits the re- use them instead of virgin polyethylene in the manufacture cycling of waste, especially large-tonnage, in the production of critical products for construction and household purposes. of composites. To achieve this aim, it was necessary to perform the The publication [9] reviewed the reinforcement of com- following tasks: posites with plant waste, such as rice husks and almond – to investigate the effect of waste mud solids on the shells. It is shown that the greatest improvement of polymer strength characteristics of recycled high-density polyeth- properties is limited by the filler share of 10–15 %, over ylene; which there is a deterioration of the mechanical properties – to identify the optimal waste mud solids content in and operational characteristics. recycled high-density polyethylene composites. In [10], the properties of composites, consisting of unsat- urated polyester filled with glass fibers and calcium carbon- ate, are considered, but the optimal waste concentration to 4. Method of experimental studies of recycled give the best mechanical properties to the composite is not polyethylene and WM composites reviewed. In [11], samples of plastics with organic fillers are stud- 4. 1. Method of composites research ied. It is shown that the properties of the obtained com- As a raw material for the filler production, two types of posites depend on fiber composition, adhesion properties, waste mud, selected at one of the operating gas wells were particle size and mass fraction of the filler. used. The first sample (WM 1) was selected at the drilling The paper [12] proved the prospects and feasibility of interval (220–2,400 m) and was a polymer-treated clay mud obtaining complex-modified basalt plastics based on corona- (based on bentonite clay). The second sample (WM 2) cor- treated high-density polyethylene and disperse basalt, since responded to the drilling interval (2,400–4,145 m) and was all physicochemical and mechanical properties of polyeth- a thin clay, polymer, salt mud (based on potassium, sodium ylene composites are enhanced. In [13], it is proved that the and calcium carbonate salts). Studies of mud properties were introduction of disperse basalt and vermiculite into poly- carried out according to standard methods used in mud ethylene makes it possible to increase the whole complex of quality testing [19]. physicomechanical characteristics and also to improve com- The chemical composition was determined by the follow- bustibility indices of the developed composites. ing standard methods. Flint (IV) oxide (with a mass fraction In [14, 15], the high efficiency of kaolin as a filler for from 1 % to 90 %) was determined by gravimetry and pho- mixes of such polymers as polystyrene, low-density poly- tometry according to DSTU 3305.3-96 (GOST 2642.3-97) ethylene (LDPE) and polypropylene is also shown. The using KFK-2 (Russia), iron oxide (III) – by photometry strengthening effect of such a filler on the complex of phys- according to DSTU 3305.6-96 (GOST 2642.6-97) using icomechanical characteristics of the obtained composites is KFK-2 (Russia), sulfur content – by gravimetry according demonstrated. to DSTU 3055-95, loss on ignition – by gravimetry ac- 56 Ecology cording to GOST 2642.2-86, potassium and sodium oxide were used to obtain finished images. The mass released from content (with a mass fraction from 0.1 % to 5 %) – by plas- the extruder was shaped as a 15×10×1.5–4.5 mm tile. ma spectrometry according to DSTU 3305.11-96 (GOST The study of impact strength and ultimate bending of 2642.11-97), aluminum, magnesium and calcium oxides – by the obtained samples was carried out on a pendulum pile complexonometry. driver according to GOST 4647 (DIN EN ISO 179-1-2006, Recycled polyolefins were used as an object of the study, DIN EN ISO 179-2-2000) and GOST 9550 (DIN EN ISO as well as composites on their basis with the addition of in- 178: 2006), respectively. The choice of these strength char- organic drilling waste. Selection of appropriate polymers for acteristics of the studied recycled polyethylene is due to the the composite was carried out according to the technological considerable fragility of this material due to its degradation and operational characteristics specified in the technical in use. This can be seen from the decrease in the studied documentation for the respective grades of polyolefins. strength properties in comparison with virgin polyethylene Waste materials of high-density polyethylene were chosen 276-73: impact strength decreased from 60 to 18.2 kJ/m2, as the polymer matrix for creating composites (Fig. 1, a). breaking stress from 250 to 120 MPa. These materials are crushed, out of service BLUE RAIN For micrographs of filler distribution at the fracture of water pumps, produced of high-density polyethylene 276-73. the samples, the USB Digital Microscope (China) with up The choice of the above polyolefins was primarily due to to 1600x magnification was used. the fact that they do not require complex preparation meth- Water absorption (wt%) of the samples was determined ods. In addition, the products made of these polymers are as the amount of water absorbed by the 15×10×1.5–4.5 mm not subject to significant impacts during use owing to the sample as a result of its stay in distilled water for 24 hours at short life cycle. Before recycling, such waste only needs to a temperature of 18–20 °С. be ground and, if necessary, granulated. Mathematical processing of experimental results was Also, the choice of these polymers was facilitated by their performed using the Statistica 7.0 software package. In the rheological characteristics, which determined the possibility regression analysis, the task was to search for the functional of obtaining composites at elevated temperatures with no dependency of the expectation of response M(Y) on the thermal degradation of the used filler, as well as high-quality values of the specified factors Х: M(Y)=f(X). As a response mixing of polymers with the filler. function, the properties of composites (Y1 – impact strength Dried (Fig. 1, c) and powdered (Fig. 1, d) WM samples a, kJ/m2; Y2 – breaking stress s, MPa; Y3 – water absorp- (Fig. 1, b) were used as a filler. tion, %) were considered in the experiments. As an inde- pendent variable (Х), affecting the response function, mud dosage was chosen. 5. Results of the study of composite properties with the introduction of drilling waste 5. 1. Results of the study of waste mud composition (sample 1 and sample 2) In this study, muds from different drilling intervals а b (depth), differing in composition and properties were used as a filler (Table 1). Table 1 Properties of muds Characteristics of mudsParameter WM 1 WM 2 WM sampling depth, m 2,400 4,145 c d Density, g/cm3 1.19 1.24 Relative viscosity, sec/quart 90 54 Fig. 1. Composite materials: a – high-density polyethylene waste; b – waste mud; c – dried mud; d – WMS powder pH 9.5 11.16 (ready composite filler) Solids, vol.% 22 16 Lubricant (Oil), vol.% 3 4 The obtained fine clay fraction (Fig. 1, d) was mixed Sand (solids larger than with recycled high-density polymer (Fig. 1, a) to the desired 0.3 0.275 microns) filler content from 0 to 30%. Chloride concentration, mg/l 2,000 90,000 Total hardness (Ca2+), mg/l 200 360 4. 2. Method of obtaining and testing composite samples KСl content, % – 6 + Composites were obtained by extruding prepared raw ma- K content, % – 3.14 terials in a single-screw laboratory extruder at a temperature of 170–210 °С and screw speed of 0.5–1.5 s–1. The extruder Analysis of Table 1 shows that excess chlorides in both L/D ratio is 25, while to increase the distribution homogene- samples (especially in WM 2) represent an environmental ity of disperse waste in the resulting composites, 3 mass runs hazard of contamination of underground aquifers in case of 57 Eastern-European Journal of Enterprise Technologies ISSN 1729-3774 2/10 ( 98 ) 2019 mud pit depressurization. Studies of the chemical composi- duction of both WMS samples relative to the original poly- tion are given in Table 2. mer without filler. Moreover, the bentonite clay WMS filler (WM 1) with a content of 20 % (change in impact strength Table 2 from 18.2 to 63.3 kJ/m2) has the highest indices. Chemical composition of waste mud samples Share, % 70 Chemical composition, index WMS 1 WMS 2 60 Silicon oxide (SiO2) 45.3 26.5 Aluminum oxide (Al2O3) 16.5 9.0 50 Calcium oxide (CaO) 6.6 7.6 Magnesium oxide (MgO) 2.84 0.84 40 Iron oxide (Fe2O3) 5.24 4.12 30 Sodium oxide (Na2O) 4.20 8.4 Potassium oxide (K2O) 2.10 9.4 20 WMS 1 Titanium oxide (Ti2O) 0.62 0.52 WMS 2 10 Sulfur oxide (S) 0.90 1.18 0 5 10 15 20 25 30 Loss on ignition 16.2 32.7 Filler level, % Fig. 2. Dependency of impact strength on waste mud filler Analysis of Table 2 confirms that these WM samples level differ in composition: WM 1 contains more aluminum and silicon compounds, which is typical for bentonite clays, and As a result of statistical data processing, equations of WM 2 contains more salts of sodium and potassium. approximating curves were obtained, allowing to calculate At the same time, of interest is the possibility of binding values of breaking stress s (MPa) depending on the WMS x the solids of drilling waste in the polymer matrix of recycled level (wt%) in the composite: polymers, for example, as a substitute for other kaolin-based fillers. This will allow not only recycling of drilling waste, sWMS1=118.9024+10.1506∙x–0.4088∙x2+0.0052∙x3; (3) but also, possible improvement of operational characteristics of composites obtained from HDPE waste. sWMS2=118.9857+8.5068∙x–0.1725∙x2–0.002∙x3. (4) 5. 2. Results of the study of the characteristics of the Graphically, these dependencies are shown in Fig. 3. obtained composite samples The results of the study of the obtained composite sam- 220 ples of recycled polymers and dried WM solids are presented 210 in Table 3 and Fig. 2–4. 200 190 Table 3 180 Results of the study of composite characteristics 170 160 Filler Impact strength, Breaking stress, Water level, kJ/m2 150 MPa absorption, % 140 % WMS 1 WMS 2 WMS 1 WMS 2 WMS 1 WMS 2 130 0 18.2 18.2 120 120 1 1 120 WMS 1 5 30.2 23.3 156.4 154 1.45 1.2 WMS 2110 10 39.4 28.4 188.8 187.6 1.9 1.4 0 5 10 15 20 25 30 15 54.1 34.5 195 199.3 2.3 1.7 Filler level, % 20 63.3 38.1 200.1 207.4 2.6 2.1 Fig. 3. Dependency of breaking stress on waste mud filler 25 56.1 34.1 197 189.7 2.75 2.5 level 30 39 28.7 195.1 166.6 2.9 2.9 Breaking stress also varies significantly: from 120 to 200.1 MPa (with the introduction of 20 % of the WMS 1 As a result of statistical processing of experimental data, filler). Filling of the composite with WMS 2 has a slightly equations of approximating curves were obtained, which better indicator (up to 207.4 MPa with the introduction of allow calculating the values of impact strength a (kJ/m2) 20 % of filler). The increase in WMS 2 amount leads to a depending on the WMS x filler level (wt%) in the composite: more pronounced drop in strength (up to 166.6 MPa with the introduction of 30 % of filler) than the introduction of WMS 1 aWMS 1=18.7405+1.1713∙x+0.1764∙x2–0.0064∙x3; (1) filler (up to 195.1 MPa with the introduction of 30 % of filler). As a result of statistical processing of experimental data, aWMS 2=18.1357+0.8089∙x+0.051∙x2–0.0022∙x3. (2) equations of approximating curves were obtained, allowing to calculate water absorption values (%) depending on the Graphically, these dependencies are shown in Fig. 2. WMS х filler level (wt %) in the composite: Filling of recycled polymer with the disperse phase leads to a significant increase in impact strength with the intro- Water absorptionWMS1=0.9738+0.11∙x–0.0015∙x2; (5) 58 Breaking stress, MPa Impact strength, kJ/m2 Ecology Water absorptionWMS 2=0.9952+0.0329∙x+0.001∙x2. (6) These assumptions can be illustrated by the example of fracture micrographs of the samples (Fig. 5). In case of insuf- Graphically, these dependencies are shown in Fig. 4. ficient filling (Fig. 5, a), there are unfilled pores and defects. With a filler share of 20 % (Fig. 5, b), there is a uniform par- 3,2 ticle distribution, sufficient filling of the pores and polymer 3,0 structure that provides the maximum strength. Excess filler 2,8 (Fig. 5, c) decreases the strength of the samples due to the 2,6 formation of large agglomerates. 2,4 2,2 2,0 1,8 1,6 1,4 1,2 WMS 1 1,0 WMS 2 0,8 0 5 10 15 20 25 30 Filler level, % а b Fig. 4. Dependency of moisture absorption on waste mud filler level With an increase in the filler share, water absorption increases (Fig. 4), and the dynamics of this indicator in the composite with WMS 1 filler is slightly higher than that of the composite with WMS 2 filler. But with a filling degree over 25 %, water absorption of the samples is close and levels off at 30 %. In general, an increase in water absorption up to c 3 % does not significantly affect the operational characteris- tics of the samples and does not lead to their swelling. Fig. 6. Photos of fracture of recycled high-density polyethylene composites filled with WMS 1: а – 10 % filling; b – 20 % filling; c – 30 % filling 6. Discussion of the results of the study of the developed polymer composites using waste mud It should be noted that the obtained composites outper- form similar recycled polyethylene polymer composites with Testing of composites for strength characteristics the use of disperse fillers of various nature. Thus, [7, 20] showed that the removal of inorganic drilling waste can recycled polyethylene composites using such fillers as talc, improve the strength characteristics of waste high-density TiO2 and others have significantly lower operational char- polyethylene. Composites with 20 % of WM filler have the acteristics than those of the composite samples developed highest strength characteristics, and both impact strength in this work. and ultimate bending increase. These results are consis- The limitation of this study is the insufficient knowledge tent with the general laws of the processes of filling poly- of the conditions (temperature, changes in the properties of mers with disperse fillers. Thus, in [8, 9] it is noted that composites during recycling, etc.) of possible recycling of the the introduction of disperse fillers in rather small amounts obtained recycled polyethylene composites filled with WMS (up to 10–20 %), as a rule, contributes to the preservation to 20–30 %. or even some increase of the strength of polymer compos- Further studies of the developed recycled high-density ites. However, exceeding the specified content additively polyethylene composites using inorganic drilling waste are reduces the strength properties of the composite. This associated with the structure and morphology of composites. suggests a general boundary degree of filling of polymers This is important for optimization of recycling conditions with disperse substances to increase their strength prop- depending on the composition and structure of drilling erties. It is worth noting that the introduction of WMS waste used. into polymer waste increases water absorption from 1 % to In general, modification of recycled high-density poly- 2.9 % with the maximum investigated filling of 30 %. The ethylene with the use of inorganic drilling waste (WMS in latter is due to the hydrophilic nature of the studied WMS the amount of 20 %) allows increasing the strength proper- samples, since clay particles in their composition are prone ties (impact strength up to 63.3 kJ/m2 and ultimate bending to swelling. to 207.1 MPa) of recycled composites on their basis. This The main reasons for the strengthening of recycled poly- allows using them in the manufacture of critical parts for ethylene due to the introduction of WMS in the form of fine construction, engineering and domestic purposes. particles are the growth restriction of polymer microcracks and their branching when meeting with filler particles. It is assumed that due to different particle sizes of the filler, the 7. Conclusions maximum density of packaging it in the polymer matrix and good homogenization of the filler in the polymer binder were 1. Introduction of WMS into recycled high-density poly- achieved. ethylene increased impact strength (up to 63.3 kJ/m2 after 59 Water absorption, % Eastern-European Journal of Enterprise Technologies ISSN 1729-3774 2/10 ( 98 ) 2019 the introduction of WMS 1) and ultimate bending (up to regression equations in the form of a quadratic polynomial, 207.1 MPa after the introduction of WMS 2) with a slight in- from which it follows that the maximum falls on the range of crease in moisture absorption to 3 %. The obtained recycled WMS filling of 15–25 %. high-density polyethylene polymer composites outperform 2. 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