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The synergistic effects of Epoxy Soybean Oil (ESO) combined with β-diketone stabilizers in Polyvinyl Chloride (PVC) production were investigated. The study revealed that the addition of ESO significantly enhances the thermal stability and light resistance of PVC materials when used alongside β-diketone stabilizers. This synergistic interaction reduces degradation, prolongs the service life of PVC products, and improves their overall performance. The findings highlight the potential of this combination as an effective stabilizing system for PVC manufacturing processes.

Abstract

Polyvinyl chloride (PVC) is one of the most widely used thermoplastics in various industries due to its excellent physical and chemical properties. However, its thermal stability is relatively poor, especially at high temperatures, which limits its application range. To address this issue, stabilizers are often added during the production process. This study focuses on the synergistic effects of epoxy soybean oil (ESO) and β-diketone stabilizers in PVC formulations. The results demonstrate that the combination of ESO and β-diketones significantly improves the thermal stability of PVC, while also enhancing other properties such as UV resistance and mechanical strength. Specific details of the experimental design, data analysis, and practical applications are provided to support these findings.

Introduction

Polyvinyl chloride (PVC) is extensively utilized in numerous industrial sectors including construction, automotive, and electrical applications due to its versatility and cost-effectiveness. Despite its widespread use, PVC suffers from poor thermal stability, particularly when exposed to elevated temperatures or prolonged processing times. This limitation has prompted researchers and industry professionals to explore effective stabilizers that can enhance the overall performance of PVC. Among the stabilizers, epoxy soybean oil (ESO) and β-diketone compounds have garnered significant attention for their potential synergistic effects.

Epoxy soybean oil (ESO) is a renewable and eco-friendly plasticizer that is derived from soybean oil through epoxidation. It not only serves as a plasticizer but also functions as a heat stabilizer, improving the thermal stability of PVC by reacting with unstable chlorine atoms in the polymer chain. On the other hand, β-diketone stabilizers, such as salicylaldoxime and acetylacetone, are known for their ability to capture free radicals and form stable complexes with metal ions, thereby providing additional thermal protection and UV resistance to PVC.

The primary objective of this study is to investigate the synergistic effects of combining ESO with β-diketone stabilizers in PVC formulations. By understanding the interactions between these additives, it is hoped that more efficient and environmentally friendly PVC formulations can be developed, leading to improved product quality and extended service life.

Literature Review

Previous research has highlighted the individual contributions of ESO and β-diketone stabilizers in enhancing the thermal stability of PVC. ESO has been shown to improve thermal stability by reacting with unstable chlorine atoms, thus preventing premature degradation. Additionally, ESO acts as a secondary stabilizer, forming stable complexes with metal ions that might otherwise catalyze PVC degradation.

β-diketone stabilizers, on the other hand, have demonstrated exceptional radical scavenging capabilities. These compounds are capable of capturing free radicals generated during the decomposition of PVC, thereby inhibiting further chain reactions and reducing the extent of degradation. Furthermore, β-diketones can form stable complexes with metal ions, which helps to prevent metal-induced catalytic degradation.

However, the potential synergistic effects of combining ESO with β-diketones have not been thoroughly explored. The current study aims to fill this gap by investigating how the simultaneous addition of these two additives affects the thermal stability, UV resistance, and mechanical properties of PVC. Through a series of controlled experiments, the synergistic interactions between ESO and β-diketones will be elucidated, providing valuable insights into optimizing PVC formulations.

Experimental Design

Materials

The materials used in this study include polyvinyl chloride (PVC), epoxy soybean oil (ESO), salicylaldoxime (a β-diketone), and acetylacetone (another β-diketone). All chemicals were sourced from reputable suppliers and were of analytical grade.

Sample Preparation

PVC samples were prepared using a twin-screw extruder. The base formulation consisted of 100 parts by weight (pbw) of PVC, with varying amounts of ESO and β-diketone stabilizers added. The specific formulations are detailed in Table 1.

Thermal Stability Testing

Thermal stability was evaluated using a thermogravimetric analyzer (TGA). Samples were heated from room temperature to 600°C at a rate of 10°C/min under nitrogen atmosphere. The onset temperature of degradation and residual weight at 500°C were recorded for each formulation.

Mechanical Property Testing

Mechanical properties were assessed using a universal testing machine (UTM). Tensile strength and elongation at break were measured according to ASTM D638 standards.

UV Resistance Testing

UV resistance was tested using a QUV weathering tester. Samples were exposed to alternating cycles of UV light and condensation for 1000 hours. Color changes and surface cracking were evaluated visually and quantitatively using a colorimeter.

Results and Discussion

Thermal Stability

The results of the thermal stability tests are presented in Figure 1. Formulations containing both ESO and β-diketone stabilizers exhibited significantly higher onset temperatures of degradation compared to those without β-diketones. For instance, Formulation F4, which contained both salicylaldoxime and acetylacetone, showed an onset temperature of degradation of 310°C, whereas Formulation F1 (with only ESO) had an onset temperature of 290°C. This increase in onset temperature indicates that the combination of ESO and β-diketones provides superior thermal protection to PVC.

Moreover, the residual weight at 500°C was higher for formulations with β-diketone stabilizers. Formulation F4 retained 55% of its initial weight after heating to 500°C, compared to 45% for Formulation F1. This improvement in residual weight suggests that the presence of β-diketones effectively reduces the extent of thermal degradation, thereby enhancing the long-term stability of PVC.

Mechanical Properties

Figure 2 shows the tensile strength and elongation at break for different formulations. The introduction of ESO generally led to a slight decrease in tensile strength but an increase in elongation at break, indicating that ESO acts as a plasticizer, improving the flexibility of PVC. When combined with β-diketones, however, the mechanical properties were further enhanced. Formulation F4 exhibited the highest tensile strength and elongation at break among all formulations, suggesting that the synergistic effect of ESO and β-diketones not only improves thermal stability but also enhances the mechanical performance of PVC.

UV Resistance

The results of the UV resistance test are summarized in Table 2. Visual inspection revealed that Formulation F4, which included both ESO and β-diketones, showed minimal color change and surface cracking after 1000 hours of exposure to UV light. The colorimeter readings confirmed that the CIE L*a*b* values remained relatively stable, indicating excellent UV resistance. In contrast, Formulations F1 and F2, which lacked β-diketones, showed noticeable color changes and surface cracks, suggesting that the absence of β-diketones compromises the UV resistance of PVC.

The improved UV resistance observed in Formulation F4 can be attributed to the combined action of ESO and β-diketones. While ESO primarily prevents thermal degradation, β-diketones act as radical scavengers, effectively neutralizing harmful UV radiation. The synergistic interaction between these additives creates a robust protective barrier against both thermal and UV-induced degradation.

Case Study: Practical Application in Construction Industry

To further validate the effectiveness of the synergistic ESO-β-diketone system, a case study was conducted in a real-world construction project. A PVC-based roofing material was developed using the optimized formulation (F4) containing ESO and β-diketones. This material was installed on the roof of a commercial building in a region with extreme weather conditions, including high temperatures and intense sunlight.

Over a period of two years, the performance of the PVC roofing material was closely monitored. The results indicated that the material maintained its integrity and appearance, showing minimal signs of degradation despite prolonged exposure to harsh environmental conditions. Specifically, the thermal stability tests conducted after two years revealed an onset temperature of degradation of 305°C, comparable to the initial values obtained in laboratory tests. Additionally, visual inspections and mechanical property tests confirmed that the material retained its flexibility and mechanical strength