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1 raw material factors
The generation of porosity in the rubber extrusion section is closely related to the quality and selection of raw materials.
The following are some of the raw material factors that may lead to the generation of porosity.
1.1 Excessive low molecular volatiles low molecular volatiles in the rubber material in the extrusion process is easy to volatilise out, the formation of air bubbles. These bubbles form pores when the extruded section is cooled and cured.
1.2 Low adhesive viscosity Low adhesive viscosity will lead to uneven flow of adhesive during extrusion, which is prone to air entrapment and air bubbles. In addition, low viscosity adhesives are more prone to deformation and shrinkage during the extrusion process, further aggravating the formation of pores.
1.3 Moisture and volatile components of rubber, additives, fillers in the water and volatile components in the extrusion process is easy to heat evaporation to form bubbles. These bubbles form pores when the extruded section cools and solidifies.
1.4 Fillers and reinforcing materials The type, amount and dispersion of fillers and reinforcing materials also affect the porosity of the rubber extruded section. For example, fillers such as silica may lead to porosity if they contain moisture or are not evenly dispersed.
2 Process factors
The process parameters in the rubber extrusion process also have an important influence on the generation of section porosity. The following are some process factors that may lead to the generation of porosity.
2.1 Extrusion temperature is too high or too low Extrusion temperature is too high will lead to the rapid volatilisation of low molecular volatiles in the rubber material to form air bubbles; while the extrusion temperature is too low will lead to poor fluidity of the rubber material, which is easy to produce air entrapment and air bubbles.
2.2 Extrusion speed is too fast or too slow extrusion speed is too fast will lead to the rubber in the extruder residence time is not enough, can not be fully plasticised and exhaust; and extrusion speed is too slow will lead to the rubber in the extruder overheating decomposition of air bubbles.
2.3 Cooling is not timely or uneven after the extrusion of the rubber material needs to be cooled in a timely manner to prevent the expansion and spread of air bubbles. If the cooling is not timely or uniform, it may lead to the formation of air bubbles in the extruded section after cooling and curing.
2.4 Mould design defects Mould design is unreasonable or defective may also lead to the generation of rubber extrusion cross-section porosity. For example, improperly designed mould runners and poor air venting may result in air bubbles not being discharged smoothly during the extrusion process.
The generation of porosity in the rubber extrusion section is closely related to the quality and selection of raw materials.
The following are some of the raw material factors that may lead to the generation of porosity.
1.1 Excessive low molecular volatiles low molecular volatiles in the rubber material in the extrusion process is easy to volatilise out, the formation of air bubbles. These bubbles form pores when the extruded section is cooled and cured.
1.2 Low adhesive viscosity Low adhesive viscosity will lead to uneven flow of adhesive during extrusion, which is prone to air entrapment and air bubbles. In addition, low viscosity adhesives are more prone to deformation and shrinkage during the extrusion process, further aggravating the formation of pores.
1.3 Moisture and volatile components of rubber, additives, fillers in the water and volatile components in the extrusion process is easy to heat evaporation to form bubbles. These bubbles form pores when the extruded section cools and solidifies.
1.4 Fillers and reinforcing materials The type, amount and dispersion of fillers and reinforcing materials also affect the porosity of the rubber extruded section. For example, fillers such as silica may lead to porosity if they contain moisture or are not evenly dispersed.
2 Process factors
The process parameters in the rubber extrusion process also have an important influence on the generation of section porosity. The following are some process factors that may lead to the generation of porosity.
2.1 Extrusion temperature is too high or too low Extrusion temperature is too high will lead to the rapid volatilisation of low molecular volatiles in the rubber material to form air bubbles; while the extrusion temperature is too low will lead to poor fluidity of the rubber material, which is easy to produce air entrapment and air bubbles.
2.2 Extrusion speed is too fast or too slow extrusion speed is too fast will lead to the rubber in the extruder residence time is not enough, can not be fully plasticised and exhaust; and extrusion speed is too slow will lead to the rubber in the extruder overheating decomposition of air bubbles.
2.3 Cooling is not timely or uneven after the extrusion of the rubber material needs to be cooled in a timely manner to prevent the expansion and spread of air bubbles. If the cooling is not timely or uniform, it may lead to the formation of air bubbles in the extruded section after cooling and curing.
2.4 Mould design defects Mould design is unreasonable or defective may also lead to the generation of rubber extrusion cross-section porosity. For example, improperly designed mould runners and poor air venting may result in air bubbles not being discharged smoothly during the extrusion process.
