3、 Common problems and treatment methods of extrusion compounding:
1. Poor composite strength
The reasons for the poor composite strength are as follows
1) The surface oxidation of resin is insufficient. Countermeasures: increase the resin temperature; reduce the production line speed; increase the air gap (air gap refers to the distance from the die mouth of T-shaped handle to the tangent line between the compound roller and the cooling roll).
2) The resin temperature is too low. Countermeasures: increase the temperature of resin; increase the back pressure (resin pressure); check whether the heater has fault.
3) Insufficient compound pressure. Countermeasures: increase the compound pressure.
4) The drying of AC agent was not complete. Countermeasures: increase the drying temperature; reduce the linear speed; increase the drying wind.
5) The surface activity of the substrate is not enough and the corona value is low. Countermeasures: use corona pen or corona testing fluid to test the corona treatment value of the substrate before production, and do not use the base material that fails to meet the requirements.
2. Uneven composite thickness
The main reasons are as follows:
1) The temperature of T-die is not set properly. Countermeasures: adjust the temperature set by T-die.
2) The die gap of T-shaped die is not uniform. Countermeasures: adjust the die gap of T-shaped die.
3) The mouth of T-shaped head mould is sticky. Countermeasures: stop the machine and clean the die mouth.
3. Compound wrinkle.
The causes of compound wrinkling are as follows
1) The composite silicon cot is damaged or roundness is not good. Countermeasures: grind or replace the composite silicon rubber roller.
2) The guide roller is unbalanced. Countermeasures: check and adjust each guide roller to balance the guide roller.
3) The linear speed is too low. Countermeasures: increase the linear speed.
4) The tension is too low. Countermeasures: increase tension.
5) The problem of raw materials. Countermeasures: replace raw materials.
4. Poor transparency of composite film
The reasons for the poor transparency of the composite film are as follows
1) The extrusion temperature of extruder is too low, resulting in poor plasticization of resin. Countermeasures: according to the characteristics of resin properties and actual production conditions, the corresponding extrusion temperature should be set and controlled to ensure good plasticization of resin, which is one of the preconditions to improve the transparency of composite film.
2) The surface temperature of cooling steel roller is too high and the cooling effect is too poor, which greatly reduces the transparency of composite film. Countermeasures: properly reduce the temperature of cooling water and the surface temperature of cooling steel roller. Generally speaking, the temperature of cooling water is controlled below 20c, and the surface temperature of cooling steel roller is controlled below 60C.
3) The transparency of the substrate itself is not good. Countermeasures: change the substrate with good transparency.
5. composite membrane gel and fish eye spot.
reason:
1) Improper setting of extruder temperature, especially the temperature of die head and resin is too low, resulting in poor resin plasticization, resulting in shark skin phenomenon or fish eye like spots in the molten resin. Countermeasures: adjust the extrusion temperature and resin temperature of extruder to appropriate value to ensure good plasticization of resin.
2) There is moisture in the resin, which affects the plasticization of the resin. Countermeasures: stir and dry the resin to remove the moisture contained in it, so that the resin can be fully plasticized.
3) If other resins with different melt index or density are mixed into the resin, the plasticization of the resin is not good or incomplete. Countermeasures: change the resin with proper melt index and density.
4) When the resin is replaced, the barrel is not cleaned thoroughly, and other residual resins or impurities in the barrel have adverse effects on the resin plasticization. Countermeasures: thoroughly clean the barrel and remove the influence of impurities.