Analysis of abnormal vulcanization of rubber products
Below the common abnormalities in the vulcanization process of rubber products are summarized and analyzed.
Lack of vulcanization
Insufficient vulcanization is mainly manifested in the physical properties of rubber products that are not up to standard, have poor elasticity, easy to deform, and may even have odor. There are the following reasons for the lack of vulcanization:
1. Low vulcanization temperature: The control of temperature during vulcanization is important. Too low a temperature will lead to a slow vulcanization reaction, unable to meet the expected cross-linking density, resulting in insufficient vulcanization.
2. Insufficient vulcanization time: When setting the vulcanization time, if the thickness and formula characteristics of the rubber are not fully considered, the short time will cause the rubber to not fully vulcanize and affect the performance of the finished product.
3. Formula design problem: Insufficient sulfur content in the formula or uneven distribution can also lead to insufficient vulcanization, especially using improper sulfur or catalysts.
Excessive vulcanization
The main manifestations of excessive vulcanization are decreased elasticity and reduced strength, especially in dynamic performance and fatigue performance. The factors that cause excess vulcanization are:
1. Excessive vulcanization temperature: Excessive vulcanization temperature will accelerate the cross-linking response, leading to excessive cross-linking of the rubber, affecting product elasticity and strength.
2. Excessive vulcanization time: Long-term high-temperature effects can cause rubber excessive vulcanization, especially when using high-active vulcanizers, excessive vulcanization time can easily cause excessive vulcanization.
3. Excessive vulcanizer: Excessive sulfur content in the formula will make the sulfide process uncontrollable and cause product performance to decrease.
Bubble and empty cave
It is manifested as small bubbles or empty holes in the finished product. This type of defect not only affects the appearance of rubber products but also reduces its mechanical strength and sealing performance. The reasons for the formation of bubbles and cavities include:
1. Contain impurities: Rubber material contains insoluble impurities that can cause bubbles. The impurities are not compatible with the rubber matrix. In the process of vulcanization, a local gap will be formed, which is manifested as a bubble.
2. High moisture content: The raw material contains too much moisture. During the vulcanization process, heating will evaporate and generate gas, thereby forming a bubble or empty hole.
3. Unemployment of ingredients: The distribution of fillers, sulfur, or auxiliary agents in the formula is unevenly distributed, and local bubbles or empty holes will be formed during the vulcanization process, which will affect the quality of the product.
4. Improper operation: Improper temperature control, insufficient mixing time, or too long during rubber mixing, will cause bubbles in the rubber.
Uneven vulcanization
There may be the following reasons for uneven vulcanization:
1. Unewal of temperature distribution: The temperature distribution of vulcanization molds or equipment is unevenly distributed, resulting in different heating conditions in different areas, and the degree of vulcanization is different.
2. Unewal thickness: The thickness of rubber products is large, which will cause insufficient vulcanization in thicker parts, while thinner parts may have excessive vulcanization.
3. Unewal distribution of vulcanizers: In the process of ingredients or mixed, uneven distribution of sulfur agents will cause different sulfurization in the internal parts of rubber products.
Surface sticky
In the process of vulcanization, the surface of rubber products may appear up, which makes the product feel poor and easy to absorb dust or impurities. The main reasons for rubber products on the surface are:
1. Surly vulcanization temperature: Insufficient temperature can lead to insufficient surface cross-linkage, forming viscous substances that are not fully vulcanized.
2. Insufficient vulcanization time: Insufficient vulcanization time can also cause the surface to stick, especially for thicker products, it is more likely to occur.
3. Migration of vulcanizing agent: During the sulfide process, some vulcanizers or additives may migrate to the surface, causing the surface viscosity to increase.
Crispy
The main manifestation is that the product is prone to break or tear during use, which not only affects the durability of rubber products but also affects its safety. There are several reasons for brittle cracks:
1. Excessive vulcanization: Excessive vulcanization will cause the rubber to become crisp, reduce its elasticity, and increase the possibility of crisp cracking.
2. Excessive vulcanization temperature: Excessive temperature can cause the rubber molecular chain to break, reduce its toughness, and increase the risk of crisp cracking.
3. Insufficient antioxidant: Not enough antioxidants are added to the formula, resulting in the oxidation of crisp cracks prone to rubber after vulcanization.
Adhesive
The problem of adhesion not only affects production efficiency but also causes surface defects on rubber products. The main reasons for the adhesion are:
1. Excessive temperature of the mold: rubber is easily adhered to the surface of the mold at high temperatures, causing the adhesive problem.
2. Improper molding agent: Using inaccurate dealer, or insufficient use of molding agents, will increase the possibility of rubber adhesion.
3. Incompatientness and molds: certain sulfur or additives may have a chemical reaction with the mold material, resulting in an adhesive mold phenomenon.
Uneven color
It is manifested as the surface color of the finished product. Unexpected colors not only affect the appearance but also may reflect the differences in the internal structure. The causes of uneven color include:
1. Unemployment of temperature: In uneven temperature during the vulcanization process, the degree of vulcanization of different parts will be different, which will affect the color distribution.
2. Unexpected ingredients: The color filler is unevenly distributed, or the pigment content in the formula is inconsistent, which will lead to color differences.
3. Migration of vulcanizers: During the process of vulcanization, sulfur or certain additives may be migrated to the surface, causing color differences.
Inconsistent hardness
The hardness of rubber products directly affects its performance, such as sealing parts, earthquake reduction, etc. The hardness is uniform. The cause of inconsistent hardness may include:
1. Unemployment of vulcanization: Unemployment of vulcanization can cause inconsistent hardness, usually caused by the uneven distribution of temperature, vulcanization time, or vulcanizer.
2. Unewal distribution of fillers: The filler is not evenly distributed when mixed, resulting in hardness differences in different parts.
3. Formula design problem: The unevenness of the sulfur or auxiliary in the formula will directly affect the sulfurization effect and cause inconsistency of the hardness.
Accelerate
Aging acceleration will cause products to have problems such as brittleness and discoloration in the product in a short period. The reasons for aging acceleration include:
1. Excessive temperature: Excessive temperature during vulcanization will accelerate the oxidation and thermal aging of rubber.
2. Insufficient anti-aging agent: There is not enough anti-aging agent in the formula, resulting in the rapid aging of the product after vulcanization.
3. High environmental humidity: In the process of vulcanization, excessive environmental humidity will increase oxidation speed and accelerate aging.
suggestions
There are many abnormalities in the process of vulcanization of rubber products. These problems will not only affect the appearance of the product but also directly affect their utilization performance and life. To avoid the occurrence of the above problems, the following measures can be taken:
1. Strictly control the parameters of the vulcanization process: reasonably control the process parameters such as temperature, time, and pressure, and adjust according to the needs of different products.
2. Optimize the formula design: Select suitable sulfur, fillers, and additives to ensure that each component is evenly distributed to avoid quality defects caused by formula problems.
3. Use the appropriate de-molding agent and mold material: Prevent adhesive problems, while ensuring that the molding agent does not affect product performance.
4. Strengthen quality testing: Timely discover abnormal conditions in the process of vulcanization through various testing methods, and adjust the production process to ensure product quality.
Through scientific and reasonable process control and formula design, it can effectively reduce the abnormal conditions in the vulcanization process of rubber products and improve product quality and production efficiency.
