OBTAINING COMPOSITE MATERIALS BASED ON POLYVINYL CHLORIDE (PVC) MODIFIED WITH PERLITE FILLER AND Ca(C₁₇H₃₅COO)₂

ABSTRACT

This study investigates composite materials based on polyvinyl chloride (PVC) modified with perlite and calcium stearate (Ca(C₁₇H₃₅COO)₂). Perlite (5–10%) and Ca(C₁₇H₃₅COO)₂ (1–2%) were added to 15% plasticized PVC granules, and new composite granules were produced using an extruder at 190°C. The mechanical properties of the obtained composites were analyzed. The addition of perlite and calcium stearate increased the hardness and mechanical strength of PVC, but reduced its elasticity. The density of the material also decreased, making it lighter, which allows its use as a construction and decorative material. Optimal results were observed when 5% perlite and 1% Ca(C₁₇H₃₅COO)₂ were added.

АННОТАЦИЯ

В данной работе исследуются композиционные материалы на основе поливинилхлорида (ПВХ), модифицированного перлитом и стеаратом кальция (Ca(C₁₇H₃₅COO)₂). Перлит (5–10%) и Ca(C₁₇H₃₅COO)₂ (1–2%) добавлялись к 15% пластифицированных гранул ПВХ, и новые композитные гранулы были получены с помощью экструдера при температуре 190 °C. Проведен анализ механических свойств полученных композитов. Добавление перлита и стеарата кальция повышало твердость и механическую прочность ПВХ, но снижало его эластичность. Также снижалась плотность материала, что делало его легче, что позволяет использовать его в качестве строительного и декоративного материала. Оптимальные результаты были получены при добавлении 5% перлита и 1% Ca(C₁₇H₃₅COO)₂.

Keywords: polyvinyl chloride, perlite, calcium stearate, plasticization, tensile strength, hardness, and Charpy test.

Ключевые слова: поливинилхлорид, перлит, стеарат кальция, пластификация, прочность на разрыв, твердость, испытание по Шарпи.

Introduction

Among widely used thermoplastics, polyvinyl chloride (PVC) remains one of the most demanded polymers because of its durability, chemical resistance, and relatively low production cost. These features allow PVC to be applied in numerous industrial areas, including pipe manufacturing, building panels, window profiles, and protective coatings. For this reason, enhancing PVC performance through the incorporation of natural or mineral fillers has become a key research focus in modern material science [1].   

Table 1.

Chemical and physical properties of perlite [3]

The incorporation of perlite into a PVC matrix contributes to reducing the overall density of the material, increasing its resistance to heat, and strengthening its mechanical characteristics, making the resulting composite highly suitable for construction applications. Moreover, such PVC–perlite systems are recognized as both environmentally friendly and cost-effective materials [2;3].

The manufacturing process of these composites usually involves several technological steps: preliminary drying of both the polymer and the filler, accurate proportioning and blending of the components, thermal melting of the mixture, and subsequent shaping by extrusion or pressing methods. In most formulations, the amount of perlite is maintained at 5–10%, since adding more filler tends to decrease the flexibility and deformation resistance of the composite. When the mixture is prepared under optimal parameters, the final material demonstrates improved mechanical durability and a smooth, uniform surface structure [4;5].

2.Materials and Methods

The main polymer used in the study was 15% plasticized PVC. As a filler, natural expanded mineral perlite with a particle size of 0.1–0.25 mm was used. Calcium stearate Ca(C₁₇H₃₅COO)₂ was selected as a stabilizer and surface-active agent. Perlite was added in amounts of 5% and 10%, while calcium stearate was added in amounts of 1–2%, and tests were conducted to determine the optimal composition of samples with different ratios.

Initially, PVC, perlite, and calcium stearate were dried at 80–90°C for 1 hour. Then the measured masses of these components were mixed in a laboratory mixer for 10 minutes until a uniform distribution is obtained.

Table 2.

Composition and appearance of samples prepared based on PVC

The resulting mixture was processed through an extruder at 190°C to obtain composite granules. Samples with different percentage compositions—PVC, PVC+2P, PVC+3P, PVC+4P—are prepared (Table 2). Based on these samples, mechanical tests were performed, namely tensile (Shimadzu AG-X Series Universal Testing Machine), hardness (Shimadzu HMV-G Vickers Hardness Tester), and impact tests (Impact Testing Machine).

3. Results and Discussion

Tensile Tests

All samples had a total length of 7 mm and were clamped in grips during the test, with a test length of 40 mm, a width of 5 mm and a thickness of 2 mm. The device presented the results in graphs after the tests (Figure 2): one shows the relationship between force (N) and elongation (mm) (Figure 2a), the other shows the relationship between stress (MPa) and deformation (%) (Figure 2b). These graphs were used to determine the tensile behavior, mechanical strength and elastic modulus of the material.

Figure 2. Mechanical properties of PVC-based composites: a-stress-strain and b-pressure-strain relationships

We have visually analyzed the stress-strain properties of the materials in Figure 2a. The first sample consists of only 15% plasticized PVC, and as can be seen from the graph, the initial stress is low, the strength increases gradually and increases proportionally with the elongation. In this sample, the maximum force is around 64.5 N and the elongation reaches 47.66 mm, which shows that PVC is very elastic. The second sample, PVC+2P, has increased stiffness and reached a maximum force of 117.3 N, while the elongation is 24.6 mm. In this graph, this sample is almost 1.8 times less elastic than the first sample, but its stiffness is higher because the filler and stabilizer increase the resistance to tension. The third sample, PVC+3P, has increased the maximum force to 142 N but the elongation only reaches 12.1 mm. This material showed a strong and less elastic, i.e. brittle behavior compared to other materials, due to the high amount of perlite. The PVC+4P sample, on the other hand, has a maximum force approaching 135.2 N and an elongation of 24.5 mm. This sample contains 5% perlite, like sample 2, but the Ca(C₁₇H₃₅COO) content is increased from 2 to 1%. The elasticity is almost unchanged due to the uniformity of the perlite content, but the high Ca stearate content increases the strength.

Pressure (MPa) and deformation (%) It is helpful to study the elastic and strength properties of the materials in Figure 2b. The maximum stress of the first sample reaches approximately 6.45 MPa and the elongation is 119.1 %. This shows the basic elastic properties of PVC. The maximum stress of PVC+2P increases to 11.73 MPa and the elongation decreases to 62.4%. The material is strengthened, but the elongation decreases. The PVC+3P combination increases the stress to 14.26 MPa and the elongation is 30%. This material is stronger, but the deformation is very small. The PVC+4P sample reaches a maximum stress of 13.5 MPa, and the elongation is 62.4%. It is clear that increasing the Ca stearate content does not significantly affect the elongation of the material, but increases the strength.

These results represent the general mechanical properties of PVC-based composites, perlite and Ca stearate additives increase the mechanical strength of the material, but a high filler content reduces the elasticity.

Hardness (Vickers Hardness)

A Vickers Hardness (VHN) test was conducted to determine the hardness properties of PVC-based composites. This test allows you to evaluate the surface hardness of the material and compare the effect of various additives (perlite and Ca stearate). The test used pure 15% plasticized PVC and composites of different compositions. Several measurements were taken for each sample and the average values ​​​​are listed in the table (Table 3).

Table 3.

Results of the Vickers Hardness (VHN) test of composites

The results showed that the PVC sample showed the lowest stiffness, indicating that it had a soft and flexible behavior. The combination of PVC+2P significantly increased the stiffness (VHN=12), which is associated with strengthening the material and increasing its resistance to deformation. PVC+3P showed the highest stiffness (VHN=20), but the elongation and elasticity decreased, meaning that the material was stiffer but had lower ductility. PVC+4P, on the other hand, gave an average result in terms of stiffness (VHN=15), providing an optimal balance of strength and elasticity. The results in the table show that the addition of perlite and Ca stearate increases the stiffness and mechanical strength of PVC-based composites. Higher perlite and Ca stearate contents stiffen the material but reduce its elasticity.

Impact test (Charpy)

A Charpy impact test was performed to evaluate the impact resistance of PVC-based composites. This test allows us to determine how much energy a material can absorb under rapid impact. The samples were 60 mm long, 10 mm wide and 4 mm thick, with a 2 mm V-notch in the center. Each sample was tested using a device and the energy absorbed (J) was measured, then normalized to the surface area of ​​the sample to calculate the energy absorption (kJ/m²).

Table 4.

Charpy impact test results and impact strength values

The results showed that the pure PVC sample had the lowest impact energy (approximately 75 kJ/m²), indicating that it had a soft and flexible behavior. The PVC+2P combination increased the impact energy to 125 kJ/m², indicating that the material was strengthened and resistant to deformation under impact. PVC+3P showed the highest (150 kJ/m²), but the elongation was reduced, meaning the material was stiff and had low elasticity. The PVC+4P combination balanced strength and elasticity, showing 137.5 kJ/m². The results of this Table 4 indicate that the addition of perlite and Ca stearate increases the impact resistance of the material. A higher filler content stiffens the material and increases strength, but slightly reduces the ductility and elasticity.

4. Conclusion

This study investigated composite materials based on polyvinyl chloride (PVC) modified with perlite and Ca(C₁₇H₃₅COO)₂. The mechanical properties of the resulting composites were analyzed. The tensile results indicate the following mechanical properties of PVC-based composites, namely, the addition of perlite and Ca stearate increases the mechanical strength of the material, but a high filler content reduces the elasticity. Hardness and impact tests show that the addition of perlite and Ca stearate increases the hardness and mechanical strength of PVC-based composites. The density of the material also decreased and its weight became lighter, which allows it to be used as a construction and decorative material. The optimal result was observed with 5% perlite and 1% Ca(C₁₇H₃₅COO)₂, the material has strong and moderate elastic properties.

References:

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