Why do silicone products crack? Silicone products are widely used in medical, electronic, kitchenware, maternal and child care fields due to their excellent elasticity, temperature resistance, and chemical stability. However, in actual use or production processes, cracking of silicone products occurs from time to time, which not only affects product performance but may also pose safety hazards. We will deeply analyze the core causes of cracking in silicone products from four dimensions: raw material quality, production process, usage environment, and design structure, providing scientific references for industry practitioners and consumers.
1. Raw material quality: "congenital defects" of inferior rubber materials
The performance of silicone products directly depends on the quality of raw materials. If recycled materials, doped silicon powder or low purity silica gel are used, it will result in insufficient tear strength of the product, and cracks will appear under slight external force. For example, some manufacturers add a large amount of silicon powder to the adhesive to reduce costs, making materials that originally did not meet tear strength standards more prone to brittleness. In addition, if bubbles or impurities are not fully eliminated during the mixing process of the rubber material, stress concentration points will also form inside the product, becoming the "fuse" for cracking.
Key indicators: The tear strength of high-quality silicone should be ≥ 30kN/m, the tensile strength should be ≥ 8MPa, and it must pass food grade certifications such as FDA and LFGB. If the rubber material is stored for too long or not sealed, it may also cause performance degradation due to oxidation, further increasing the risk of cracking.
2. Production process: The subtle balance between temperature and time
The production of silicone products involves multiple processes such as mixing, vulcanization, and demolding, and any deviation in any link may cause cracking:
Uncontrolled vulcanization process: Excessive vulcanization temperature or time can cause excessive cross-linking of silicone molecular chains, resulting in brittle products; On the contrary, insufficient vulcanization will result in incomplete curing of the rubber material and easy tearing during demolding. For example, an experiment showed that when the vulcanization temperature increased from 180 ℃ to 200 ℃, the cracking rate of the product increased by 40%.
Mold design defects: Unreasonable mold structure (such as rounded corners and uneven wall thickness) can cause obstruction of silicone flow, resulting in stress concentration at thin walls. In addition, rough or dirty mold surfaces can hinder demolding, and forcibly peeling can easily strain the product.
Improper demolding operation: Excessive use of demoulding agent or rough handling techniques (such as prying with sharp tools) can directly scratch the surface of the silicone, forming micro cracks that gradually expand with prolonged use.
Optimization direction: Adopt segmented vulcanization process, first low-temperature pre vulcanization and then high-temperature shaping; Plating hard chromium or spraying PTFE coating on the surface of the mold to reduce the friction coefficient; Use compressed air assistance or silicone special demolding tools during demolding.
3. Design structure: the "invisible killer" of stress distribution
Structural optimization during the product design phase is key to preventing cracking:
Uneven wall thickness: Stress concentration is prone to occur at the transition between thickness and thinness, and it is necessary to use R-angle design (corner radius ≥ 0.5mm) or gradual wall thickness for smooth transition. For example, a certain brand of silicone kitchenware gradually increased the wall thickness at the connection between the pot handle and the pot body from 2mm to 5mm, resulting in a 75% decrease in cracking complaint rate.
Functional gap: The grooves and holes designed for installing screws or buckles will weaken the structural strength and need to be compensated by adding reinforcing ribs or local thickening. A certain medical grade silicone catheter adopts a wavy reinforcement structure at the joint, effectively dispersing the stress during insertion and removal.
Dynamic deformation design: For products that require repeated bending (such as silicone data cables), the deformation process needs to be simulated through finite element analysis to optimize material distribution and cross-sectional shape. A certain experiment showed that changing the cross-section of the data line from circular to D-shaped increased its bending life from 10000 times to 50000 times.
With the evolution of silicone materials towards high strength and toughness (such as the application of fluorosilicone and phenyl silicone), cracking problems will be further reduced in the future. But no matter how advanced the technology is, following scientific principles and process specifications is always the core rule to ensure the quality of silicone products.
