ENHANCING THERMAL STABILITY OF POLYETHYLENE COMPOSITES THROUGH ORGANO-INORGANIC MODIFICATION

ABSTRACT

This article presents the results of research on obtaining organo-inorganic composite materials based on polyethylene (PE) and increasing their thermal stability. During the work, components such as ammonium dihydrogen phosphate, carbamide, sodium metasilicate, magnesium and calcium oxides, and melamine were used. The synthesized viscous substance was processed in a drying oven at a given temperature and time, and maleic anhydride and low molecular weight maleinized polyethylene were used as modifiers. The thermal properties of the obtained samples were studied, and it was shown that the modifiers increase the thermal decomposition temperature in the PE matrix and improve the heat resistance of the material.

АННОТАЦИЯ

В данной статье представлены результаты исследований по получению органо-неорганических композиционных материалов на основе полиэтилена (ПЭ) и повышению их термической стабильности. В процессе работы использовались такие компоненты, как дигидрофосфат аммония, карбамид, метасиликат натрия, оксиды магния и кальция, а также меламин. Синтезированное вязкое вещество обрабатывали в сушильном шкафу при заданной температуре и времени, а также использовали малеиновый ангидрид и низкомолекулярный малеинизированный полиэтилен в качестве модификатора. Изучены термические свойства полученных образцов и показано, что модификаторы повышают температуру термического разложения в ПЭ-матрице и улучшают термостойкость материала.

Keywords: polyethylene, organo-inorganic composites, ammonium dihydrogen phosphate, urea, maleic anhydride, modifier, thermal stability, TGA, DSC.

Ключевые слова: Полиэтилен, органо-неорганические композиты, дигидрофосфат аммония, мочевина, малеиновый ангидрид, модификатор, термостойкость, ТГА, ДСК.

Introduction. In recent years, the improvement of the physicochemical properties of polymer materials, particularly the enhancement of their thermal stability, has become one of the most relevant scientific directions. Polyethylene (PE) is distinguished by its low cost, ease of processing, and wide range of applications; however, its low heat resistance and limited thermal stability restrict its use in certain fields [1]. Therefore, the development of modified organo-inorganic composite materials based on PE and the improvement of their thermal and mechanical properties represent an important scientific and practical task. In this study, a viscous substance was synthesized by incorporating urea, ammonium dihydrogen phosphate, sodium metasilicate, magnesium oxide, calcium oxide, and melamine. [2,3]. In addition, the structure formation and heat resistance of composites using maleic anhydride and maleated polyethylene were studied [12].

Research method

Urea: A chemical compound, the diamide of carbonic acid. White crystals, soluble in polar solvents [8].

Formula: Ch₄N₂O, melting point: 133°C, solubility: water, glycerin, ethanol

Density: 1.32 g/cm³, molar mass: 60.06 g/mol, chemical formula: (NH2)2CO

Melamine: Colorless crystal, slightly soluble in water. In 2007, world production was over 1 million tons [6].

Chemical formula: C3H6N6, solubility: freely soluble in water, molar mass: 126.12 g/mol, melting point: 345°C, density: 1.57 g/cm³

Ethylene glycol: H2O-CH₂-CH₂-OH - an oxygen-containing organic compound, a diatomic alcohol, one of the representatives of polyols. When purified, it is a transparent, colorless liquid with a slightly oily consistency. It is odorless and has a sweet taste [5].

Chemical formula: C₂H₆O₂, density: 1.11 g/cm³, melting point: -12.9°C

Magnesium oxide: A chemical compound with the formula MgO, white crystals, slightly soluble in water, fire and explosion resistant. It belongs to the class of basic oxides. Its main form is the mineral periclase [10].

Chemical formula: MgO, molar mass: 40.3044 g/mol, IUPAC name: magnesium oxide, melting point: 2.852°C, density: 3.58 g/cm³

Calcium oxide: A white crystalline substance, formula CaO. It belongs to the class of basic oxides. Lime and its reaction product with water, Ca (OH)2, are widely used in construction [11

Chemical formula: CaO, molar mass: 56.0774 g/mol, IUPAC name: Oxocalcium, solubility: water, glycerin, melting point: 2.572°C, density: 3.34 g/cm³

1. 0.1 mol (11.5g) of ammonium dihydrogen phosphate (NH4H2PO4), 0.1 mol (6g) of urea (CH4N2O), 0.05 mol (5.6g) of sodium metasilicate (Na2SiO3) and 0.01 mol (8g) of zinc oxide (ZnO) were weighed on a scale, dissolved in distilled water in a 100 ml beaker and evaporated in a water bath. A viscous substance was formed. The resulting viscous substance was dried in a drying cabinet for 2 hours.

2. 0.1 mol (6g) of ammonium dihydrogen phosphate (NH4H2PO4), 0.1 mol (6g) of carbamide (CH4N2O), 0.05 mol (5.6g) of sodium metasilicate (Na2SiO3), and 0.01 mol (5.6g) of calcium oxide (CaO) were weighed and dissolved in distilled water, and 0.05 mol (6.3g) of melamine (C3H6N6) was dissolved in 50 ml of ethyl alcohol, mixed, and then evaporated in a water bath. A viscous substance was formed. The resulting viscous substance was dried in a drying cabinet for 3 hours [5].

3. 0.2 mol (12g) of urea (CH₄N₂O), 0.2 mol (19.6g) of phosphoric acid (H3PO4), 0.1 mol (4g) of magnesium oxide (MgO) were weighed on a scale and dissolved in distilled water in a 100 ml beaker, and 0.2 mol (12g) of ethylene glycol (C₂H₆O₂) was dissolved in 50 ml of alcohol. The resulting viscous substance was dried in a drying cabinet for 2 hours [12].

Modifiers

Maleic anhydride

C4H2O3 (GOST-5854-78), a.u.t., colorless rhombic crystals, Mr = 98.06 g / mol, Tqay = 84.0 ° C / 14 mm wire. Driven under vacuum at

Cyul = 60 ° C, ρ60 = 1.3140 g / cm3.

4. Low molecular weight maleated polyethylene

Low molecular weight maleated polyethylene was used in the work.

Scheme 1. Formula of the maleated link of polyethylene

Research results. Low molecular weight maleated polyethylene is a viscous mass (1.9 Pa.s at 323 K), with an acid number of 65 mg (potassium hydroxide)/g.

The residual content of maleic anhydride in low molecular weight maleated polyethylene is approximately 0.3%.

Table 1.

Recipe of organic-inorganic materials

During the research, polyethylene-based organo-inorganic composite materials were synthesized with various modifiers and their thermal properties were evaluated [13]. The results obtained showed the following:

Effect of Modifiers: When the compositions containing ammonium dihydrogen phosphate, urea, sodium metasilicate, and magnesium and calcium oxides were dried under identical conditions, their viscosity and structural-forming ability increased.

Effect of Maleated Polyethylene and Maleic Anhydride: These modifiers exhibit good compatibility with the PE matrix and enhance the heat resistance of the material. According to the TGA results, the onset temperature of thermal decomposition in the composites was found to be 20–30 °C higher compared to the control samples.

Structural Stability: DSC analysis revealed a well-defined melting point and an increased degree of crystallinity in the composite materials, which in turn contributed to improved mechanical strength.

Optimized Composition: The incorporation of urea and melamine in specific proportions played a key role in enhancing heat resistance. In particular, the addition of melamine at a concentration of 0.05 mol produced the most optimal result.

Technological Convenience: Drying the synthesized viscous substance for 2–3 hours resulted in the formation of a stable composition, thereby simplifying the production process under industrial conditions.

General Conclusion: Overall, the experimental results confirmed that the thermal stability of polyethylene-based composites can be significantly enhanced through appropriate modification of their properties.

Conclusion

The results of the conducted studies clearly demonstrate that the selected modifiers play a decisive role in significantly enhancing the thermal stability of polyethylene-based composite materials. In particular, the incorporation of maleic anhydride and maleated polyethylene not only elevates the decomposition temperature of the PE matrix but also substantially improves its resistance to thermal degradation. Such modifications expand the scope of potential applications of the developed compositions, especially in the production of high-temperature-resistant structural and technical products where durability and thermal reliability are critical. For future research, it is recommended to conduct a systematic study of the synergistic effects arising from varying concentrations and combinations of different modifiers. Establishing an optimized formulation that balances thermal stability, mechanical strength, and technological convenience will be of practical importance. Such an approach will not only advance the scientific understanding of modification processes but also support the development of next-generation polymer composites tailored for demanding industrial applications.

References:

1. Karpov V. L., Soloviev V. N. Chemistry and technology of polymers. – Moscow: Chemistry, 2019. – PP. 456.
2. Khmelnitsky G. M., Petrov A. V. Organo-inorganic composites: structure, properties and application. – Saint Petersburg: Nauka, 2020. – PP. 384.
3. GOST (state standard) 5854–78. Maleic anhydride. Technical conditions. – Moscow, 2018.
4. Sapozhnikova E. I., Abdullin R. A. Thermogravimetric analysis of polymeric materials. // Journal of Applied Chemistry – 2021. – Vol. 94. – No. 3. – PP. 412–420.
5. Zhi, J., Wang, X., & Li, P. Thermal Stability Enhancement of Polyethylene Using Inorganic Fillers. Polymer Degradation and Stability, 2022, 198. – PP. 109–120.
6. Sahnoun, A., Benali, A., & Merabet, F. Effect of Maleic Anhydride Grafted Polyethylene on Composite Properties. Journal of Applied Polymer Science, 2021, 138(20). – PP. 505–512.
7. GOST (state standard) 132–06. Ammonium dihydrogen phosphate. Technical conditions. – Moscow, 2017.
8. GOST (state standard) 4517-88. Urea. Technical conditions. – Moscow, 2019.
9. GOST (state standard) 13830-97. Sodium metasilicate. Technical conditions. – Moscow, 2016.
10. GOST (state standard) 4526-75. Magnesium oxide. Specifications. – Moscow, 2020.
11. GOST (state standard) 9179-77. Calcium oxide. Specifications. – Moscow, 2021.
12. Yu, L., Chen, W., & Fang, J. DSC and TGA Characterization of Polyethylene Blends with Urea and Phosphate Modifiers. Journal of Thermal Analysis and Calorimetry, 2023, 147. – PP. 2135–2148.
13. Khaidarov, Tuymurod & Rakhmankulov, Alikul & Karimov, Ma’sud & Djalilov, Abdulahat. (2024). Temperature stability of polypropylene-based composites modified with carbon nanotubes. Universum: Chemistry & Biology. – PP. 121. 10.32743/UniChem.2024.121.7.17893.