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Why do some silicone rubber products need to undergo secondary vulcanization after molding?

Silicone rubber products are believed to be familiar to everyone. Some products can be directly used after being molded, while others require secondary vulcanization (also known as secondary sulfurization). Actually, after molding, it looks good to the naked eye and can be used normally. Why do we need to undergo secondary vulcanization? Firstly, it should be noted that not all silicone rubber products require secondary vulcanization of silicone. However, depending on the formula of the raw materials, some can be directly molded in one go, while some special materials such as fluororubber products and EPDM silicone rubber products require secondary vulcanization. This is because during the primary vulcanization of these materials, the peroxides inside will decompose and undergo high polymer reactions, producing some low molecular weight compounds (such as benzene, benzoic acid, etc.). These low molecular weight compounds mixed with rubber will reduce the mechanical properties and lifespan of silicone rubber, and are also toxic. This is very unfavorable for silicone kitchenware, so silicone rubber product manufacturers often use secondary vulcanization to decompose and evaporate low molecular weight compounds. Secondly, after the first vulcanization is completed, the silicone molecules may not be fully crosslinked (vulcanization is insufficient). Secondary vulcanization of silicone rubber can make it more fully and evenly vulcanized, thereby improving the mechanical properties and durability of the rubber. Thirdly, it can be subjected to silicone secondary vulcanization, such as the EPD silicone rubber products widely used in automobiles, which can remove odors and improve the comfort of car passengers after secondary vulcanization. Fourthly, in order to reduce costs and increase production capacity, silicone product manufacturers often shorten the first silicone vulcanization time and then extend the second vulcanization time to ensure that the products are fully vulcanized while also improving their competitiveness.

2025

07/01

Do you know the reason why rubber products produce bubbles?

In the daily production process, various problems are encountered, and bubbles are a common one. Some bubbles are on the surface of rubber products, while others are inside. There are many reasons for their occurrence. Next, Kexin, a silicone protective cover manufacturer, will share the reasons with you as follows: 1. The problems with the raw materials themselves may be due to poor quality, formulation matching issues, or excessive moisture in the materials (which can be solved by adding some calcium oxide during mixing). It is recommended that the manufacturer eliminate them one by one, 2. Improper operation can lead to insufficient or uneven rubber mixing, which can be avoided by improving the operation manual. A complete and compliant operation manual is the most basic requirement for rubber product manufacturers, 3. The problem of exhaust first needs to be ruled out whether there is a process of setting exhaust during the processing. Secondly, there is a problem with the mold itself. If the mold does not have an exhaust groove, or the exhaust hole design is unreasonable, or if it is blocked by foreign objects, bubbles will also be generated 4. Problems during vulcanization, such as insufficient vulcanization time, insufficient pressure during vulcanization, or high impurities in the vulcanizing agent, can also generate bubbles 5. The product is too thick, which slows down the heat transfer of the rubber. In the end, only the outer surface is vulcanized, while the inside is filled with bubbles   Other suggestions 1. Slow down the injection speed of the material, and excessive injection speed during the processing is also an important reason for the generation of bubbles. 2. We know that the generation of bubbles is due to the entry of air, and the solution is to prevent air from entering. Therefore, a more thorough solution is to replace the vulcanization molding machine with a vacuum molding machine.

2025

06/30

What are the precautions for using silicone tableware.

What are the precautions for using silicone tableware? In daily life, tableware is the item that comes into contact with food the most frequently, and the selection and safety of its material are highly concerned. In recent years, silicone tableware has gradually gained popularity among consumers due to its non-toxic, odorless, high-temperature resistant, and easy to clean characteristics. However, despite the many advantages of silicone tableware, there are still some precautions to be taken during use to ensure its safety and durability.   The high temperature resistance of silicone tableware is one of its highlights, but this does not mean that it can be placed in extreme high or low temperature environments at will. Generally speaking, silicone tableware can withstand temperatures ranging from -40 ℃ to 230 ℃, and it is safe to use within this range. However, if exposed to an environment beyond this temperature range for a long time, silicone may undergo deformation or aging, affecting its service life. Therefore, when heating or freezing silicone tableware, it is advisable to avoid exceeding its tolerance temperature as much as possible to avoid affecting its performance.   When using silicone tableware, it is also important to avoid contact with sharp or rough objects. Although silicone is soft and has a certain degree of elasticity, long-term exposure to sharp objects or rough surface wear can also lead to surface scratches or damage. This not only affects aesthetics, but may also accumulate dirt and affect hygiene. Therefore, when using silicone tableware, direct contact with sharp objects such as knives and spatulas should be avoided as much as possible to avoid scratching the surface. Silicone tableware also needs to pay attention to some details during the cleaning process. Due to the silicone material's resistance to absorbing grease and stains, it is relatively easy to clean. However, it should be noted that rough cleaning tools or strong detergents should be avoided to prevent damage to the silicone surface. At the same time, after cleaning, ensure that the tableware is completely dry and avoid prolonged immersion in water to prevent the growth of bacteria. When storing silicone tableware, attention should also be paid to avoiding direct sunlight and humid environments. Direct sunlight can accelerate the aging of silicone materials, while humid environments may trigger the growth of mold. Therefore, it is recommended to store silicone tableware in a cool and dry place, and use sealed bags or storage boxes to keep it dry and hygienic. In addition to the above points, attention should also be paid to the scope of application of silicone tableware. Although silicone tableware has many advantages, it is not suitable for all occasions. For example, when heating food in a microwave oven, it is advisable to avoid using silicone tableware as much as possible, as the heating method may cause heat accumulation inside the silicone tableware, leading to deformation or damage. In addition, for certain dishes that require prolonged high-temperature heating, it is not recommended to use silicone tableware to avoid exceeding its temperature tolerance range. Special attention should be paid to silicone tableware used by infants and young children. Due to the weaker resistance of infants and young children, they also have higher hygiene requirements for tableware. Therefore, when choosing silicone tableware for infants and young children, it should be ensured that it meets relevant national safety standards and undergoes regular disinfection treatment. During use, attention should also be paid to observing whether the tableware is damaged or deformed, and if found, it should be replaced in a timely manner. It should be noted that although silicone tableware has many advantages, not everyone is suitable for use. For some people who are allergic to silicone materials, using silicone tableware may cause allergic reactions. Therefore, an allergy test should be conducted before use to ensure that you will not experience any allergic reactions to it.  

2025

06/26

What is the hot pressing process for silicone products?

1.Basic principles Hot pressing is an important process in the processing of silicone products. Silicone itself is made from silicone rubber raw material, which is a polymer with high elasticity. During the hot pressing process, silicone rubber is placed in a specific mold, and by heating and applying pressure, the silicone rubber flows inside the mold and fills various parts of the mold, thereby forming the desired shape of the silicone product. The main principle is to use thermal energy to make the molecular chains of silicone rubber more active, reduce their viscosity, and make them more fluid. At the same time, pressure helps silicone rubber better fill the gaps in the mold, ensuring that the molded product is dense and complete.   2.Process steps Preparation stage Firstly, it is necessary to choose suitable silicone rubber raw materials. Select the appropriate silicone rubber formula based on different product requirements, such as hardness, temperature resistance, color, etc. For example, for silicone products that require high hardness, silicone rubber with higher cross-linking density will be selected; For products that require high temperature resistance, corresponding high temperature resistant additives will be added. At the same time, the mold should be cleaned and preheated. Molds are usually made of metal (such as aluminum alloy, steel, etc.), and cleaning is to remove impurities, oil stains, etc. on the surface of the mold to prevent affecting the forming quality. Preheating the mold can accelerate the vulcanization speed of silicone rubber and reduce the molding time. The preheating temperature is generally around 100-200 ℃, depending on the type of silicone rubber and the characteristics of the product. Forming stage Place an appropriate amount of silicone rubber into the mold cavity. This' appropriate amount 'is precisely calculated to ensure that the mold cavity can be completely filled without causing excessive overflow. Then close the mold and place it into a hot pressing equipment (such as a flat vulcanizing machine). Then start heating and pressurizing. The heating temperature is usually between 150-250 ℃, and the pressure is generally around 5-20mpa. Under high temperature and pressure, silicone rubber undergoes vulcanization reaction. The vulcanization reaction is the process of forming cross-linking bonds between the molecular chains of silicone rubber through cross-linking agents, transforming the silicone rubber from a plastic state to a highly elastic solid state. This process usually lasts from a few minutes to several tens of minutes, depending on factors such as the formula of the silicone rubber, the size of the mold, and the thickness of the product. Post processing stage When the predetermined molding time is reached, stop heating and pressurization, open the mold, and remove the molded silicone product. At this point, silicone products may still have some burrs or excess silicone rubber parts that need to be trimmed. The trimming methods include manual trimming, mechanical cutting, etc. Sometimes it is necessary to perform post vulcanization treatment on silicone products. Post vulcanization can further improve the performance of silicone products, such as enhancing their heat resistance and mechanical strength. Post vulcanization is usually carried out in an oven at a temperature of around 200-250 ℃ for a duration of about 2-4 hours. If silicone products are not post vulcanized and used directly, their performance may decrease over time during subsequent use.   3.Equipment and materials Equipment: The main equipment for hot press forming is a hot press forming machine, commonly known as a flat vulcanizing machine. This machine has two heating plates on top and bottom, which can evenly heat the mold. It is also equipped with a pressure system that can precisely control the pressure applied to the mold. At the same time, the control system can set and adjust parameters such as temperature, pressure, and time to meet different molding requirements. Materials: In addition to silicone rubber raw materials, some auxiliary materials will also be used. For example, release agents can prevent silicone rubber from adhering to the mold, making it easier to remove after molding. Release agents are generally organic silicon or wax substances, which are evenly applied to the surface of the mold during use. In addition, various additives such as crosslinking agents, reinforcing agents, pigments, etc. will be added to improve the performance of silicone rubber. Crosslinking agents are used to promote the vulcanization crosslinking reaction of silicone rubber; Reinforcing agents (such as white carbon black, etc.) can improve the mechanical strength of silicone rubber; Pigments are used to color silicone products. The hot pressing process can produce various complex shaped and high-performance silicone products, which are widely used in electronics, medical, automotive, home and other fields, such as silicone seals, silicone buttons, silicone toys, etc.

2025

06/25

Should silicone products avoid direct sunlight exposure?

Should silicone products avoid direct sunlight? Silicone products have been widely used in daily life and industrial fields due to their high and low temperature resistance, flexibility, and environmental friendliness. However, long-term exposure to sunlight may cause irreversible damage to silicone products. Research has shown that ultraviolet (UV) radiation can damage the molecular structure of silicone, leading to material aging, discoloration, and even performance degradation. For example, issues such as yellowing of silicone phone cases and hardening of silicone kitchen utensils are often directly related to sun exposure. Although some silicone materials have improved their weather resistance by adding anti UV agents, direct sunlight is still considered the main environmental factor accelerating their deterioration.   1.The destructive mechanism of ultraviolet radiation on silicone products Molecular chain degradation The main component of silicone, polydimethylsiloxane (PDMS), undergoes photooxidation reaction under ultraviolet radiation, causing the silicon oxygen bonds (Si-O) and carbon hydrogen bonds (C-H) in the molecular chain to break, resulting in a decrease in material elasticity and surface cracking. This process is particularly significant in high-temperature environments, such as in summer when the temperature inside the car can reach over 60 ° C, exacerbating the aging rate of silicone products. Decomposition of pigments and additives Dyes and anti-aging agents in colored silica gel products are sensitive to ultraviolet radiation. Long term sun exposure can cause pigments to fade and turn yellow, while weakening the effectiveness of anti UV agents, forming a vicious cycle of "protective layer failure accelerated aging". For example, white silicone tableware may gradually turn yellow, while dark silicone phone cases are prone to localized fading. Irreversible loss of physical properties Ultraviolet radiation not only affects the appearance, but also alters the mechanical properties of silicone. Experiments have shown that after UV aging testing, the tensile strength of silicone products may decrease by 20% -30%, and their tear resistance may weaken, leading to seal failure or reduced protective effect of protective products such as silicone pads.   2. Practical strategies for light avoidance preservation Optimize storage environment Silicone products should be stored in a cool, dry, and well ventilated environment, with an ideal temperature of 15-25 ° C and humidity below 50% RH. Avoid placing silicone products in areas with direct sunlight such as balconies and windowsills, and use blackout curtains or storage boxes for physical isolation. For example, kitchen silicone tools can be stored in dark drawers, and outdoor silicone products are recommended to be stored in dedicated moisture-proof boxes. Collaborative protection of cleaning and maintenance Regular cleaning can reduce the synergistic destructive effects of dust, grease, and ultraviolet radiation. It is recommended to use neutral cleaning agents and a soft cloth to wipe the surface, to avoid solvents such as alcohol corroding the material. After cleaning, it should be thoroughly dried (not exposed to direct sunlight), and if necessary, a silicone protective agent can be applied to form an antioxidant barrier. Active avoidance in usage scenarios Try to minimize the exposure time of silicone products during outdoor activities. For example, when using a silicone phone case on the beach, it can be paired with a parasol or placed in a bag; Silicone accessories inside the car, such as steering wheel covers, should avoid the front windshield area or use sun visors to block direct light.   3. Targeted protection for special silicone products Limitations of UV resistant silicone gel Some industrial grade silicone can enhance its UV resistance by adding components such as nano titanium dioxide, but its protective effect is still limited by its service life and external conditions. This type of product needs to be regularly inspected for surface condition, and if there are small cracks or signs of hardening, it should be replaced in a timely manner. Strict requirements for medical and food grade silicone Medical catheters, baby pacifiers, and other products require extremely high material stability. It is recommended to follow the dual principle of "avoiding light+sealing": when storing, use aluminum foil bags for packaging and label the opening date to ensure that they are used within the validity period. Color maintenance of artistic silicone products Silicone artworks such as sculptures and decorations can be treated with UV protective spray, which can not only retain color saturation, but also resist more than 90% UV damage. At the same time, the display location should be away from strong light sources such as spotlights to extend the artistic lifespan.   The threat of direct sunlight to silicone products is both hidden and long-lasting, and scientific light avoidance preservation strategies can effectively delay material aging, maintain its functionality and aesthetics. From molecular level protection to detailed adjustments for daily use, every step is related to the service life of silicone products.

2025

06/24

What is the difference between tempered glass and heat-resistant glass?

With the development of modern society, glass, as a living material, has been applied to various occasions. There are a wide variety of glass types, and each type of glass has different material performance characteristics, such as tempered glass and heat-resistant glass. So, what are the differences between tempered glass and heat-resistant glass?   1. Different applications: Tempered glass is used in construction, building templates, decoration industry, furniture manufacturing industry, home appliance manufacturing industry, electronics and instrumentation industry, automobile manufacturing industry, daily necessities industry, and special industries. And heat-resistant glass is used in the daily necessities industry, such as industrial boiler mirrors, mechanical equipment window glass, etc.   2. The impact of temperature changes varies: Heat resistant glass refers to glass containing strong heat-resistant components such as boric acid and silicic acid, which can withstand rapid temperature changes. It is a special type of glass that can withstand temperature differences between hot and cold fusion, and has a series of excellent properties such as low expansion, thermal shock resistance, high temperature resistance, corrosion resistance, and high strength. So it is safe to use tempered glass in ovens and microwaves, as sudden temperature changes in the microwave may cause it to burst. In the process of making tempered glass, due to the presence of "nickel sulfide" inside, the glass expands with time and temperature, and there is a possibility of self explosion. It cannot be used in the oven at all.   3. Different crushing methods: When heat-resistant glass breaks, it does not break but instead produces cracks and does not scatter. Heat resistant glass does not pose a risk of self explosion due to nickel sulfide. Heat resistant glass gradually cools down, and there is no condensation energy inside the glass, so it will not scatter when broken. When tempered glass breaks, it will burst and scatter. During the tempering process, pre stress and condensed energy are formed inside the glass. Therefore, when it breaks or self explodes, the condensed energy will be released, forming fragments that scatter and producing explosive sounds.   The above content explains the differences between tempered glass and heat-resistant glass, hoping to be helpful to everyone.

2025

06/23

What are the differences between the production and processing of conductive adhesive and ordinary adhesive?

Conductive adhesive is a commonly used type of adhesive in most electronic conductive products, mainly used for thermal sensing, suitable for precision lead assembly, low-temperature connection, especially for interconnection of thermal sensitive components, and also has good flexibility and fatigue resistance. It is widely used in adhesives. However, silicone rubber and conductive silicone are currently the most commonly used types of adhesive in products. In the production process of silicone product manufacturers, they have different production differences in performance, and the specific differences are as follows:   Conductive silicone products: Conductive adhesive is widely used in electronic assembly sensing, including thin wires and printing materials, electroplated substrates, metal layers of ceramic adhesives, metal chassis bonding, bonding wires and sockets, bonding components and flat holes passing through printed circuits, bonding waveguide tuning and hole repair, etc. All of these functionalities are derived from its material blending characteristics, including fillers such as silver or copper, nickel, carbon powder, etc., which achieve conductivity. Among them, adhesive strength additives and rheological promoters are their main additives, thus creating the advantages and disadvantages of conductive silicone.   The production of ordinary silicone and conductive silicone still has certain differences in performance. In terms of silicone product processing, ordinary silicone has faster efficiency, lower defect rate, and different yield performance. The tensile toughness of ordinary silicone is generally better than that of conductive silicone, while conductive silicone is affected not only in terms of conductivity, but also in terms of toughness and material life. Its corrosion resistance, high and low temperature resistance, wear resistance, and electrical insulation aging all decrease.

2025

06/19

How to store silicone products and how to store silicone products?

Generally speaking, silicone products have good sealing effects after production, and they are made of silicone raw materials that are also resistant to high temperatures. Therefore, silicone products are relatively easy to store. However, in many cases, customers will purchase a large amount of silicone products, and it is inevitable that dust will fall in the warehouse storage for a long time. So how to store silicone products?   Storage methods and precautions for silicone products We need a cool and dry environment, and if necessary, we can install air conditioning and temperature and humidity monitoring devices for daily checks. Secondly, the mixed rubber materials cannot be directly stacked together and need to be coated with a separating agent on the surface to prevent the raw materials from sticking together. Next, finished and semi-finished silicone rubber products should be labeled with dust-free bags, sealed and packaged in a way that does not come into direct contact with air, which can accelerate product aging and whitening. The rubber raw materials that have been added with vulcanizing agents should be well managed and generally stored for no more than 15 days. They should be used up in a timely manner before expiration. 1. Anti fouling Keep the silicone raw materials clean, as any stains on the raw materials can lead to the scrapping of silicone products, which is also one of the main reasons directly affecting the appearance of silicone products. 2. Waterproof Once silicone raw materials enter the water, it is easy to cause bubbles in the molding process of silicone products. Therefore, silicone product manufacturers not only need to ensure the waterproofness of the warehouse when storing raw materials, but also need to regularly check the dryness and wetness of the silicone raw material room; 3. Mold proof Long term storage of silicone products or silicone raw materials may cause mold growth due to the humid and hot environment in the warehouse. Once the silicone undergoes mold growth, it will lead to product deformation or loss of elasticity; Dry ventilation in the warehouse is also a key issue that silicone product manufacturers need to pay attention to; 4. Sunscreen We usually need to pay attention to the possibility of high temperature exposure when transporting silicone raw materials or products, and take corresponding sun protection measures for corresponding situations to prevent silicone products from accelerating aging under high temperature exposure for a long time; In summary, the storage of silicone products requires a cool and dry environment, and the packaging should be sealed as much as possible to avoid direct contact with air. Attention should also be paid to the waterproof, anti fouling, and anti mold storage of silicone products. The above is the method of storing silicone products. I believe everyone has gained some understanding after reading it.

2025

06/18

How to store silicone products and storage methods for silicone products?

How to store silicone products? Generally speaking, silicone products have good sealing effects after production, and they are made of silicone raw materials that are also resistant to high temperatures. Therefore, silicone products are relatively easy to store. However, in many cases, customers will purchase a large amount of silicone products, and it is inevitable that dust will fall in the warehouse storage for a long time. So how to store silicone products?   Storage methods and precautions for silicone products We need a cool and dry environment, and if necessary, we can install air conditioning and temperature and humidity monitoring devices for daily checks. Secondly, the mixed rubber materials cannot be directly stacked together and need to be coated with a separating agent on the surface to prevent the raw materials from sticking together. Next, finished and semi-finished silicone rubber products should be labeled with dust-free bags, sealed and packaged in a way that does not come into direct contact with air, which can accelerate product aging and whitening. The rubber raw materials that have been added with vulcanizing agents should be well managed and generally stored for no more than 15 days. They should be used up in a timely manner before expiration. 1. Anti fouling Keep the silicone raw materials clean, as any stains on the raw materials can lead to the scrapping of silicone products, which is also one of the main reasons directly affecting the appearance of silicone products. 2. Waterproof Once silicone raw materials enter the water, it is easy to cause bubbles in the molding process of silicone products. Therefore, silicone product manufacturers not only need to ensure the waterproofness of the warehouse when storing raw materials, but also need to regularly check the dryness and wetness of the silicone raw material room; 3. Mold proof Long term storage of silicone products or silicone raw materials may cause mold growth due to the humid and hot environment in the warehouse. Once the silicone undergoes mold growth, it will lead to product deformation or loss of elasticity; Dry ventilation in the warehouse is also a key issue that silicone product manufacturers need to pay attention to; 4. Sunscreen We usually need to pay attention to the possibility of high temperature exposure when transporting silicone raw materials or products, and take corresponding sun protection measures for corresponding situations to prevent silicone products from accelerating aging under high temperature exposure for a long time;   Silicone products require a cool and dry environment for storage, with sealed packaging as much as possible to avoid direct contact with air. Attention should also be paid to waterproof, anti fouling, anti mold and other storage precautions for silicone products. The above is the method of storing silicone products. I believe everyone has gained some understanding after reading it.

2025

06/17

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