Plastic Film Extrusion Molding
DATE：2022/9/29 8:32:09 / READ： / SOURCE：This station
Plastic Film Extrusion Molding
(4) Molding process Extrusion plastic light turning insulation PE film barrel process temperature: 120~150 ℃ in the feeding section, 160~180 ℃ in the plasticizing section, and 180~200 ℃ in the homogenizing section. Forming mold temperature: 190~200 ℃. Bubble blowing ratio is 2.5~3. Air ring cooling.(5) Notes
① In order to prolong the use time of the greenhouse film, some light oxygen stabilizers should be added to the raw materials for light conversion film forming when necessary.
② In order to increase the heat preservation effect of the greenhouse film, some anti infrared blocking agents can be properly added to the raw materials for light conversion greenhouse film forming.
③ The effective life of light conversion is within 4~6 months. In order to avoid affecting the light conversion effect of the greenhouse film, the manufacturer shall package the finished products with light proof materials.
6.2.11 Low density polyethylene degradable mulching film
The characteristic of degradable polyethylene mulch film is that it can be automatically degraded and broken into small pieces after the effective use period of the mulch film. Even if the degraded fragments remain in the soil, they will not affect the growth of crop seedlings, root development and hinder the capillary action of the soil. It can be seen that the degradable film reduces the adverse effects on soil and environmental pollution.
The process conditions and equipment used in the extrusion blow molding of degradable film are exactly the same as those of ordinary polyethylene film. The difference between the two films is only that the formula of the raw materials used is somewhat different. The raw material for degradable polyethylene mulching film is mainly low-density polyethylene. The MFR value of the melt flow rate is in the range of 4~7g/10min. A certain proportion of linear low-density polyethylene (LLDPE) can also be mixed in the LDPE resin. The strength of the mulching film formed by this mixture can be improved, while the thickness of the film can be reduced. In order to achieve the degradation and fragmentation of mulching film after the effective use period, a certain proportion of auxiliary materials that can promote the degradation of products should be added to the raw materials. This is the difference between degradable film and ordinary polyethylene film.
At present, HDPE is used as the main raw material, and the degradable film for extrusion blow molding shopping bags has also begun to be widely used.
The raw material formula for degradable polyethylene mulching film is as follows.
① The controllable photodegradable mulching film is made by adding some photodegradable agents into the main raw materials. For example, some copolymers containing ketone compounds (such as ethylene and carbon monoxide, methyl vinyl ketone, methacrolone, etc.) are added into low-density polyethylene. As ketone group has the function of chromophore, it will cause photodegradation effect after absorbing ultraviolet ray in sunlight. In addition, some additives that can promote photodegradation (such as ferrocene, benzophenone, etc.) should be added to enhance and adjust the photodegradation rate.
② The materials and lakes are made into biodegradable mulching film. When the film is used to cover the soil, the starch in the film will be destroyed by microorganisms in the soil, resulting in the fragmentation of the film.
③ The main raw material (LDPE) for plastic film forming is added with photodegradable agent and starch to make the film. Under the simultaneous action of photodegradable agent and microorganism, this kind of mulching film will have better degradation effect.
④ It can be used in the forming raw materials of shading mulch film to increase the proportion of calcium carbonate to form the film. The carbonyl group in CaCO3 in the film can accelerate the aging of surrounding resin to a certain extent, which can also be used as a photo degradable mulch film.
When adding the above auxiliary materials (starch, calcium carbonate and other additives) into PE resin, it should be noted that if the proportion of additives is too large, it will bring certain difficulties to the blow molding of LDPE mulch film.
6.2.12 Air cushion film
The so-called air cushion film is actually a kind of membrane containing bubble interlayer in the middle of the film. This kind of film material is made of low-density polyethylene resin, which is extruded and melted by an extruder
Two layers of membrane are extruded in the molding die; One layer of membrane is blistered into a mold on the vacuum roller
After the membrane bubble is formed, it is combined with another layer of membrane, and the latter is close to the opening with the membrane bubble for width
On the surface, this composite film is an air cushion film. If the convex membrane bubble surface is also compounded with a layer of film, it will become a three layer composite air cushion film. Because there is a bubble layer in the middle of the three-layer composite air cushion film, the composite film is relatively light and elastic. In addition, it has the characteristics of moistureproof, shockproof, sound insulation, beautiful appearance, insect proof, mold proof, and low price. According to the characteristics of composite air cushion film, people often use this film as the packaging material for air cushion meters, instruments, ceramics and glassware.
(1) The main raw material for extrusion molding of air cushion film is low-density polyethylene tree film, and the melt flow rate MFR of resin is required to be within the range of 5~8g/10min. In addition, a certain proportion of
(2) (3) Air cushion film extrusion flat film forming process ① Production process sequence is shown in Figure 6-29
Fig. 6-29 Production process sequence of flat film forming by air cushion film extrusion: 1 - single screw extruder, 2 - flat film forming die; 3 - Bubble blister forming roll; 4 - Guide roller; 5 - Coiling device; 6 - Traction cooling composite roll; 7 - Connections
The main raw material LDPE and its auxiliary materials are metered. The mixed plastic raw material is in molten state → mold forming two-layer film sheet → blister forming → traction guide roller compounding → winding
② Process temperature of each section of extrusion raw material barrel: 130~150 ℃ for feeding section, 170~190 ℃ for plasticizing section, and 200~220 ℃ for homogenizing section. The connecting section between the forming die and the barrel is 160~180 ℃. Forming die 160~170 ℃
The vacuum degree of the blister roll is about 0.04MPa.
(4) The quality of low-density polyethylene air cushion film shall meet the quality requirements
QB/T1259-91. See Table 6-21 for the mechanical property requirements of the film. See Table 6-22 for air cushion film compression test conditions
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