Processing Machinery
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Excessive Gel/Gel Particles in Polypropylene Extruded Products
Problem Phenomenon
Transparent or translucent gel particles (gel particles) can be seen in the extruded film or product, affecting the appearance and transparency of the product.
Gel is resin particles that are not fully plasticized or cross-linked.
Cause Analysis
(1) The high molecular weight components in the raw material are not fully plasticized
(2) The barrel temperature is too low, and part of the resin is not completely melted
(3) The mixing effect of the screw is insufficient
(4) The raw material contains cross-linked or oxidized gel
(5) The filter screen mesh is not fine enough, and the gel is not intercepted
Solution
(1) Appropriately increase the barrel temperature to the higher value within the range of 200-280°C
(2) Optimize the screw design and add mixing elements
(3) Increase the filter screen mesh to 80-120 mesh
(4) Select high-quality raw materials with low gel content
(5) Check whether cross-linked materials are mixed into the regrind
Key Takeaway
Gel is caused by insufficient plasticization or raw material quality problems, and needs to be solved from temperature control, screw design, and raw material selection.
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