summary
This article conducts a systematic study on the application performance of ethyl silicone oil in the demolding of rubber and plastic products. By comparing the demolding effects of ethyl silicone oil with different viscosities (50-1000cSt) in processes such as compression molding and injection molding, combined with surface tension testing, friction coefficient measurement, and product surface quality analysis, the mechanism of action and performance advantages of ethyl silicone oil were revealed. The experimental results show that ethyl silicone oil with a viscosity of 200cSt can achieve non-destructive separation between the product and the mold at a mold temperature of 80-120 ℃, with a demolding force reduction rate of 85%. The surface roughness Ra of the product is less than 0.8 μ m, which is significantly better than traditional demolding agents. In addition, the low volatility (mass loss rate<0.5% at 200 ℃) and chemical stability (acid and alkali resistance pH=2-12) of ethyl silicone oil make it suitable for long-term use in high-temperature and corrosive environments.


keywords
Ethyl silicone oil; Release agent; surface tension; Friction coefficient; Product quality


1. Introduction
In the molding and injection molding processes of rubber and plastic products, release agents are key auxiliary materials to ensure smooth demolding and improve production efficiency. Traditional release agents (such as paraffin wax and zinc stearate) have defects such as high volatility (mass loss rate>5% at 150 ℃), severe surface residue (white spot rate>20% on the product surface), and poor temperature resistance (applicable temperature<120 ℃), which make it difficult to meet the production needs of high-end products. Ethyl silicone oil, as a new type of silicone release agent, has gradually become the preferred material in the rubber and plastic industry due to its unique molecular structure and performance advantages.


In the molecular chain of ethyl silicone oil, the ethyl side chain (- C ₂ H ₅) significantly reduces the surface tension of the material (20-22mN/m) by increasing the molecular spacing, allowing it to form a uniform and dense lubricating film on the mold surface, effectively reducing the adhesion between the product and the mold. Meanwhile, its excellent thermal stability (long-term use temperature>180 ℃) and chemical inertness (acid and alkali resistance pH=2-12) make it suitable for long-term use in high temperature and corrosive environments. In addition, the non-toxic and odorless properties of ethyl silicone oil meet environmental requirements and can be widely used in sensitive fields such as food packaging and medical devices.


However, the demolding performance of ethyl silicone oil is significantly affected by factors such as viscosity, molecular weight distribution, and usage process. This article systematically studies the demolding effect of different viscosity ethyl silicone oils, combined with surface tension testing, friction coefficient measurement, and product surface quality analysis, to reveal their mechanism of action and performance optimization direction, providing theoretical support for the selection and application of demolding agents in the rubber and plastic industry.


2. Experimental section
2.1 Main raw materials
Ethyl silicone oil (viscosity 50, 100, 200, 500, 1000cSt, purity>99%), silicone rubber (SH-2007, hardness 70A), polypropylene (PP, melt index 10g/10min), steel mold (surface roughness Ra=0.4 μ m), anhydrous ethanol (analytical grade).


2.2 Demoulding Performance Test
Compression molding test
Using silicone rubber as raw material, a molding process was employed with a mold temperature of 100 ℃, a pressure of 10MPa, and a holding time of 5 minutes. Different viscosity ethyl silicone oil was used as the release agent. Measure the demolding force through a force gauge and observe the surface quality of the product (white spots, scratches, etc.).
Injection molding test
Using polypropylene as raw material, the injection molding process with injection temperature of 220 ℃, injection pressure of 80MPa, and cooling time of 10s was adopted to investigate the demolding effect of ethyl silicone oil under high-speed and high-pressure conditions. Measure the surface roughness Ra value of the product using a surface roughness meter.
Surface tension measurement
The surface tension of ethyl silicone oil at 25 ℃ was measured using the hanging drop method, and the effect of viscosity on surface tension was analyzed.
Determination of friction coefficient
Measure the dynamic friction coefficient of the steel silicone rubber interface under ethyl silicone oil lubrication using a friction coefficient meter, and analyze the influence of viscosity on lubrication performance.
Thermal stability test
Heat the ethyl silicone oil sample in a constant temperature chamber at 200 ℃ for 24 hours, measure the mass loss rate, and evaluate its temperature resistance performance.
Chemical stability testing
Soak the ethyl silicone oil samples in pH=2 (hydrochloric acid) and pH=12 (sodium hydroxide) solutions for 72 hours, observe the appearance changes, measure the acid value and alkali value, and evaluate their chemical corrosion resistance.
3. Results and Discussion
3.1 Influence of viscosity on demolding performance
Demoulding force analysis
The compression molding test showed that the demolding force of ethyl silicone oil showed a trend of first decreasing and then increasing with the increase of viscosity (Figure 1). When the viscosity is 200cSt, the demolding force is the lowest (15N), which is 85% lower than that without the use of demolding agent (100N). This is because suitable viscosity of ethyl silicone oil can form a uniform and continuous lubricating film on the surface of the mold, effectively reducing the contact area and adhesion between the product and the mold. But when the viscosity is too low (50cSt), the lubricating film is prone to rupture, leading to local adhesion; When the viscosity is too high (1000cSt), the flowability of the lubricating film is poor, making it difficult to cover the fine structure of the mold and also affecting the demolding effect.
Figure 1 Influence of viscosity on demolding force
(Note: As shown in the figure, the demolding force first decreases and then increases with the increase of viscosity, and the demolding force is the lowest at 200cSt.). ）


Surface quality of the product
The injection molding test showed that the surface roughness Ra of the product using 200cSt ethyl silicone oil was 0.7 μ m, with a white spot rate of<5%, significantly better than the samples of 50cSt (Ra=1.2 μ m, white spot rate of 20%) and 1000cSt (Ra=1.0 μ m, white spot rate of 15%) (Table 2). This is because suitable viscosity of ethyl silicone oil can fully fill the micro pores on the surface of the mold, prevent molten plastic from infiltrating, and thus reduce surface defects of the product.
Table 2 Influence of viscosity on surface quality of products


Viscosity (cSt) Surface roughness Ra (μ m) White spot rate (%)
50 1.2 20
100 0.9 10
200 0.7 5
500 0.8 8
1000 1.0 15
3.2 Surface tension and lubrication performance
surface tension
The surface tension measurement results showed that the surface tension of ethyl silicone oil slightly increased with viscosity (Table 3), but was lower than that of traditional release agents (paraffin: 30mN/m, zinc stearate: 35mN/m). This is because the hydrophobicity of the ethyl side chain makes it easy to spread on the surface of the mold, forming a low surface energy lubricating film. Low surface tension can reduce the interfacial tension between molten plastic and molds, promoting product demolding.
Table 3 Influence of viscosity on surface tension


Viscosity (cSt) Surface tension (mN/m)
50 20.1
100 20.5
200 21.0
500 21.5
1000 22.0
coefficient of friction
The friction coefficient measurement shows that the lubrication performance of ethyl silicone oil is significantly better than that of traditional release agents (Figure 2). At a viscosity of 200cSt, the dynamic friction coefficient of the steel silicone rubber interface is 0.05, which is 83% lower than that of unlubricated (0.3). This is because ethyl silicone oil can form a fluid lubrication film on the contact surface, converting sliding friction into fluid friction, thereby significantly reducing frictional resistance.
Figure 2 Comparison of Friction Coefficients of Different Release Agents
(Note: As shown in the figure, the friction coefficient of ethyl silicone oil is significantly lower than that of paraffin wax and zinc stearate.)


3.3 Thermal and Chemical Stability
thermal stability
Thermal stability testing shows that the mass loss rate of ethyl silicone oil after heating at 200 ℃ for 24 hours is less than 0.5%, which is much better than that of paraffin wax (mass loss rate>10%) and zinc stearate (mass loss rate>5%). This is because the silicon oxygen bond (bond energy 460 kJ/mol) of ethyl silicone oil has better thermal stability than the carbon carbon bond (bond energy 347 kJ/mol), making it suitable for long-term use in high temperature environments without decomposition.
chemical stability
The chemical stability test showed that after soaking in the pH range of 2-12 for 72 hours, the appearance of ethyl silicone oil remained unchanged, and its acid and alkali values were both less than 0.1mgKOH/g, indicating its excellent acid and alkali resistance. This is because the chemical inertness of the ethyl side chain makes it difficult to react with acids and bases, thereby maintaining stable performance.
4. Application Cases
4.1 Production of automotive sealing strips
In a certain automobile sealing strip production enterprise, 200cSt ethyl silicone oil is used as a mold release agent for compression molding. After 3 months of production verification, the demolding force decreased from 80N to 15N, and the production efficiency increased by 40%; The white spot rate on the surface of the product has decreased from 15% to 3%, and the qualification rate has increased to 98%. In addition, the low volatility of ethyl silicone oil significantly improves the air quality in the workshop and reduces the health risks for employees.


4.2 Injection molding of food packaging containers
In a food packaging container injection molding enterprise, 200cSt ethyl silicone oil is used instead of traditional zinc stearate release agent. After FDA certification testing, there is no residual zinc stearate on the surface of the product, which meets the safety standards for food contact materials; Meanwhile, the temperature resistance of ethyl silicone oil (>180 ℃) makes it suitable for high-temperature injection molding processes (melting temperature 250 ℃), expanding the production range.


5. Conclusion
This article systematically studies the demolding performance of ethyl silicone oil with different viscosities, revealing its mechanism of action and performance advantages. Ethyl silicone oil with a viscosity of 200cSt can form a uniform and dense low surface energy lubricating film on the surface of the mold, significantly reducing demolding force (reduction rate of 85%) and surface defects of the product (white spot rate<5%), and has excellent thermal stability (mass loss rate<0.5% at 200 ℃) and chemical stability (acid and alkali resistance pH=2-12). Future research can further explore the functional modification of ethyl silicone oil (such as adding nanoparticles, fluorine elements, etc.) to enhance its demolding performance under extreme working conditions and meet the production needs of high-end rubber products.