| Nanjing Sumino Precision Machinery Co.,Ltd | WhatsApp +8617712413069 Inquire Product information |
- |
- |
- |
1¡¢ Shrinkage phenomenon
The viscoelastic behavior of the polymer melt when the film is cast with a T-shaped die causes the following problems
¢Ù The width of the film narrows due to the shrinkage phenomenon;
(ii) The problem of film stretching, which is the phenomenon of material surge or breakage during stretching in air (i.e., in the air gap). When fused cast film is thermally stretched in air, the film narrows, and as a result, the edge of the film thickens. The difference between the width of the die head slit and the width of the film is usually defined as the shrinkage. The greater the shrinkage, the thicker the edge of the film (the rolled edge), and therefore the yield of the product decreases with the increase of the edge.
2¡¢Rolled edge phenomenon
Rolled edge formation mechanism: polymer cast film is the polymer through a uniform thin die head slit melt extrusion to a quench roller production. Between the die head and the quenching roller, a thick edge, called a crimp, forms. This crimp must be cut from the film and either disposed of as scrap or recycled. Edge rolls are often caused by three factors: surface tension, mold release expansion and edge stress effects. Surface tension and mold release expansion can be important factors when the material is in a low viscosity and elastic state, respectively. The main cause of crimping is still the edge stress effect, which occurs when the film is stretched between the die and the rollers. The edge of the film elongates under uniaxial stress while the material in the center elongates in a plane of tension.
The main cause of crimping is the edge stress effect. All polymer films and coatings whose thickness is controlled by drafting can suffer from this effect. Other factors such as surface tension and mold release expansion affect crimping, but the size of the crimp is much smaller and the width of the crimp is at the same level as the thickness of the film. The width of the crimp due to edge stress effects is about the same as the distance from the die head to the rollers. The edge stress effect occurs between the die head and the rollers. Edge rolls due to surface tension and high die expansion occur only under special conditions such as low viscosity of elastic fluid.
Nanjing Suminoe Precision Machinery Co., Ltd. has professional cast film production line, the company's main cast film manufacturing production line: TPU hot melt adhesive film production line, CPP/CPE cast film production line, EVA solar energy encapsulation adhesive film production line, PE sanitary breathable film production line, PVDF cast film production line, PP three-dimensional film production line, medical blood purification film production line, multi-layer co-extruded barrier film production line, LLDPE wrapping film production line production line, LLDPE winding film production line and so on.
The viscoelastic behavior of the polymer melt when the film is cast with a T-shaped die causes the following problems
¢Ù The width of the film narrows due to the shrinkage phenomenon;
(ii) The problem of film stretching, which is the phenomenon of material surge or breakage during stretching in air (i.e., in the air gap). When fused cast film is thermally stretched in air, the film narrows, and as a result, the edge of the film thickens. The difference between the width of the die head slit and the width of the film is usually defined as the shrinkage. The greater the shrinkage, the thicker the edge of the film (the rolled edge), and therefore the yield of the product decreases with the increase of the edge.
2¡¢Rolled edge phenomenon
Rolled edge formation mechanism: polymer cast film is the polymer through a uniform thin die head slit melt extrusion to a quench roller production. Between the die head and the quenching roller, a thick edge, called a crimp, forms. This crimp must be cut from the film and either disposed of as scrap or recycled. Edge rolls are often caused by three factors: surface tension, mold release expansion and edge stress effects. Surface tension and mold release expansion can be important factors when the material is in a low viscosity and elastic state, respectively. The main cause of crimping is still the edge stress effect, which occurs when the film is stretched between the die and the rollers. The edge of the film elongates under uniaxial stress while the material in the center elongates in a plane of tension.
The main cause of crimping is the edge stress effect. All polymer films and coatings whose thickness is controlled by drafting can suffer from this effect. Other factors such as surface tension and mold release expansion affect crimping, but the size of the crimp is much smaller and the width of the crimp is at the same level as the thickness of the film. The width of the crimp due to edge stress effects is about the same as the distance from the die head to the rollers. The edge stress effect occurs between the die head and the rollers. Edge rolls due to surface tension and high die expansion occur only under special conditions such as low viscosity of elastic fluid.
Nanjing Suminoe Precision Machinery Co., Ltd. has professional cast film production line, the company's main cast film manufacturing production line: TPU hot melt adhesive film production line, CPP/CPE cast film production line, EVA solar energy encapsulation adhesive film production line, PE sanitary breathable film production line, PVDF cast film production line, PP three-dimensional film production line, medical blood purification film production line, multi-layer co-extruded barrier film production line, LLDPE wrapping film production line production line, LLDPE winding film production line and so on.