Key quality problems of rubber compound silicone products and their possible causes.personalized silicone pacifier clip company

　　1. Poor dispersion

　　A. In the mixing process, the mixing time is not enough, and the discharge temperature is too high or too low; at the same time, acidic and basic compounding agents are added to the raw materials of silica gel products (for example, stearic acid and anti-scorch agent ESEN are added together with zinc oxide and magnesium oxide); Insufficient mixing; improper order of compounding; fillers added too late in the mixing cycle; small particle size carbon black and resin or viscous oil added at the same time; insufficient time for metal oxide dispersion; Add liquid accelerator after crushing; batch size is too large or too small

　　b. Process does not follow established mixing procedures; aggregates of oily and dry materials stick to top pin and hopper sides; rotor speed is not appropriate; compound is unloaded from tablet press too quickly; not used correctly Glue turning device on tablet press

　　c. Equipment Internal mixer temperature control failure; insufficient pressure on the top bolt; wear transition of the welding layer in the mixing chamber; tablet press roll temperature control failure; failure of the overhead rubber turning device on the tablet press

　　D. Material Rubber expired and partially gelled; EPDM or butyl rubber too cold; frozen natural rubber; insufficient pre-mastication of natural rubber; excess moisture in filler (clumping); added below pour point temperature Viscous compound; compound used inappropriately

　　E. The Mooney viscosity of the elastomer used in the formulation design is too different; the selection of plasticizer and rubber is not appropriate; too much hard particle compounding agent; too much filler with small particle size; resin with too high melting point; insufficient liquid plasticizer; filling agents and plasticizers

　　2. Scorch

　　A. Compounding The amount of vulcanizing agent and accelerator is too much; the vulcanization system acts too fast; the compounding agent is not weighed correctly; the small particle size filler is too much; the liquid plasticizer is not enough

　　b. Excessive filling capacity during mixing operation; insufficient cooling of the mixer; too high rotor speed; too high initial feeding temperature; Local high concentration of vulcanizing agent and accelerator due to uneven dispersion; poor dispersion of accelerator and/or vulcanizing agent; resin accumulation on the rotor; omission of anti-scorch agent; The roll is too large, or it has not cooled sufficiently after unloading

　　c. When the compound is still hot and wet, the compound is accumulated; the compound is parked for too long; the temperature of the parking place is too high; the air is not circulating

　　D. Measures to prevent scorch Strictly control roll temperature, improve cooling conditions, add materials according to operating regulations, strengthen rubber management, etc.; adjust vulcanization system and add scorch inhibitor. Commonly used anti-scorch agents are organic acid anhydrides (such as phthalic anhydride), and the general dosage is not more than 0.4 part; the amount of new high-efficiency anti-scorch agents is 0.1-0.2 parts, such as anti-scorch agent CTP (N-cyclohexylthio phthalic acid) Dimethylimide); scorch retarder is added before vulcanizing agent and accelerator

　　3. Compounding agent agglomeration

　　Insufficient plasticization of raw rubber, too large roller distance, too high roller temperature, powder falling on the surface of the roller; pressed into flakes; too large capacity of glue; powdery compounding agent coarse particles or agglomerates; too much gel

　　4. Large shrinkage

　　A. Sulfur-free compound: plasticity is too low; mixing time is too short or mixer mixing time is too long, resulting in agglomeration

　　b. Vulcanized compound: compound starts to scorch

　　w Inappropriate plasticity of plasticized rubber; too long or too short mixing time; improper mixing temperature; mixed rubber is not mixed well; more or less plasticizer is added; more or less carbon black is added or the wrong variety is used

　　7. Relative density is too high, too low or uneven

　　Inaccurate weighing, missing or mismatching of compounding agents; when carbon black, zinc oxide, calcium carbonate, etc. or oil plasticizers are less than the specified amount, the relative density of the rubber compound will exceed the specified amount; dust flying during mixing Too much loss, too much adhesion to the container wall or the feeding container is not poured cleanly; uneven mixing

　　8. The scorch time is too long or too short

　　A. Prolonged scorch time: wrong type of accelerator and less addition; missing addition of zinc oxide; wrong type of carbon black, such as using pine tar as engine oil; adding more asphalt and clay

　　B. Shortened scorch time: too much accelerator or wrong species; wrong carbon black species; excessive calcium carbonate

　　9. The hardness is too high, too low or uneven

　　If the compounding agent is not weighed accurately, if the reinforcing agent, vulcanizing agent or accelerator is excessive, the hardness of the vulcanizate will be high; on the contrary, the hardness will be low; if the plasticizer and rubber are weighed too much, the hardness will be low; uneven mixing , uneven vulcanization hardness

　　10. Frosting

　　Insufficient and uneven mixing of the rubber compound; inaccurate weighing of the compounding agent; agglomeration of sulphur or more than its solubility in rubber at room temperature; too high rubber temperature during vulcanization; too much softener; too long storage time of rubber compound ; Products lacking sulfur, etc.

　　11. Vulcanizing agent

　　Accelerator weighing inaccurate (too little), or missing zinc oxide or stearic acid; wrong carbon black variety

　　12. Undersulfur

　　Accelerator, vulcanizing agent and zinc oxide are missing or under-mixed; improper mixing operation, too much loss of vulcanizing agent or accelerator flying

　　13. Layering

　　Natural rubber compound mixed with butyl rubber or vice versa

　　14. Sticky roll. Or take off roll

　　A. Sticky roll: the roll temperature is too high or the roll distance is too small; the plasticity is too high; the softener is too much; the mixing time is too long or the dosing sequence is violated, such as adding asphalt rosin later, etc.

　　B. Roll off: the glue content is too low; the glue is hard; the roll distance is large during mixing; some synthetic rubber

　　15. Pollution

　　Physical contamination of elastomers and rubber chemicals by dust, dirt, sand and other substances; chemical contamination of butyl and EPDM rubber by other elastomers such as natural rubber and nitrile rubber ; The shovel and spoon were not used separately for different compounding agents; the improper compounding agent was used; the compounding agent remained in the previously used material tray; the oil seepage of the internal mixer oil seal; On the feeding hopper and the top bolt, if the cleaning compound is used for regular cleaning, the occurrence of such problems can be reduced; the remaining compound sticks to the discharge chute, the catch tray, the guide chute and the overhead turning device; Glue builds up at seal ring; area around mixer and tablet press is uneven

　　16. Unqualified or inconsistent physical and mechanical properties

　　Inaccurate weighing of compounding agents, especially reinforcing agents; mis-matching of vulcanizing agents and accelerators; excessive mixing; unreasonable feeding sequence and uneven mixing, which can easily lead to inconsistent performance

　　17. Performance differences between batches

　　Difference in initial feeding temperature; difference in cooling water flow or temperature; difference in top bolt pressure; error in compounding weighing; difference in compounding agent between different batches; use of substitute compounding agent; difference in discharge time and temperature ; Different operators use different methods to process the rubber on the tablet press; Variation of tamping time; different degrees of dispersion

　　18. Poor calendering performance

　　Improper selection of calendering roll temperature; failure of control of roll temperature and roll speed ratio and roll speed; Mooney viscosity of rubber compound is too low; too much tackifier; too much filling amount of viscous filler (such as clay); Processing aids; insufficient or excessive loading; wrong choice of elastomer viscosity; poor dispersion; easy scorch;

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