Product stickiness

Calendered product surface is sticky and easily blocks; fingers touching it feel obvious tackiness, and film layers are difficult to separate after sticking together. Product stickiness directly affects winding and storage — film layer blocking makes unwinding difficult and damages the film surface in severe cases. Causes of stickiness include plasticizer surface migration, insufficient cooling, and improper formulation design, most common in flexible PVC calendered products.

1. Material/formulation factors: Excessive plasticizer dosage in formulation or plasticizer type causing surface migration. 2. Cooling/environmental factors: Insufficient cooling causes product to be warm and sticky. 3. Comprehensive factors: Ambient temperature too high. 4. Roll gap adjustment factors: Crown and cross-angle compensation of calender rolls is the core means of controlling the transverse thickness distribution of the film. Crown design is based on roll deflection calculations; if it does not match the actual process load, it will cause abnormal transverse distribution of film thickness — thicker in the middle and thinner at both ends, or an inverse bow-shaped distribution. 5. Feed uniformity factors: The temperature uniformity of the calender feed and the shape stability of the material bank directly affect the uniformity of feeding into the roll nip. A material bank that is too narrow, skewed, or unevenly rolling all cause transverse thickness abnormalities in the product; the temperature and flow rate of the banbury or extrusion feed must be kept stable.

1. Process parameter optimization and adjustment: Check whether plasticizer dosage and grade are appropriate. 2. Mold/tooling improvement and maintenance: Reduce cooling roll temperature or add cooling sections. 3. Equipment inspection and system maintenance: Reduce workshop temperature. 4. Material/formulation optimization: Use anti-blocking release powder or film before winding. 6. Preventive management: Establish standardized process parameter cards and quality control limits for each mold/product, and regularly conduct process capability index (CPK) evaluations. For recurring problems, use fishbone diagrams or 5Why analysis to trace the root cause, and solidify countermeasures as PFMEA control points. Establish a regular equipment maintenance system and implement life management for key tooling such as dies/spinnerets/calender rolls/coating heads.

This problem is a typical manifestation of product stickiness in calender molding. The core of the solution lies in precise adjustment of roll gap compensation, uniform control of roll temperature distribution, and assurance of feed system stability. It is recommended to start troubleshooting from roll system parameters and gradually go deeper into the equipment and formulation levels.