Speaking of the refrigerator, I believe that everyone is familiar with the plastic parts of the refrigerator accounted for about 70% of the entire refrigerator parts, the total plastic quality accounted for about 40% of the total weight of the refrigerator.
Five kinds of refrigerator commonly used plastic raw materials
First, polystyrene - PS
Polystyrene commonly used in the production of refrigerators includes general purpose polystyrene (GPPS), high impact polystyrene (HIPS), and expandable polystyrene (EPS).
Polystyrene is the most widely used plastic in the production of refrigerators, and its dosage accounts for more than 60% of the total plastics used in refrigerators.
GPPS: It has good dimensional stability and low shrinkage. It is mainly used for injection molding to make transparent and hard parts in refrigerators, such as vegetable boxes and bottle holders.
HIPS: It is a toughened modified polystyrene with good impact resistance and good ductility after heating. Mainly used in the manufacture of refrigerator liners and door linings, the processing technology adopted is vacuum adsorption molding.
EPS: Good shock absorption performance, mainly used for manufacturing shock absorption auxiliary materials in the packaging and transportation of refrigerator products.
Second, polypropylene - PP
The production process is simple, the price is low, the injection molded product has high toughness and surface smoothness, and has good chemical corrosion resistance, and is mainly used for manufacturing refrigerator drawers in the production of refrigerators.
Third, acrylonitrile-butadiene-styrene - ABS
Excellent overall performance such as high strength, good gloss, easy processing, and low product shrinkage. It is mainly used for processing exterior parts such as door handles and various decorative strips.
Fourth, polyethylene - PE
It is odorless, tasteless, non-toxic, has good impact resistance and chemical resistance, and has low water permeability. Mainly used in the manufacture of various pipes, refrigerator companies usually use the process of blow molding to process.
Five, polyurethane - PU
In the polyurethane products, the foaming material accounts for more than 80% of the total amount, and has the characteristics of low thermal conductivity and good processing performance, and is very suitable for heat insulation, so it is widely used for the partition of the refrigerator door and the cabinet. Hot layer.
The heat insulation layer is a key component of the refrigerator. Most refrigerator manufacturers adopt the on-site foaming process. The polyol, isocyanate and cyclopentane are used as the main raw materials, and are filled into the door body of the refrigerator and the heat insulation layer of the cabinet at a certain high temperature. Under foam molding, and by adjusting the different ratios between raw materials, control the speed of foaming and cellbing effect to obtain the desired heat preservation effect.
Sixth, other plastics
In addition to the above five types of materials, polyvinyl chloride (PVC), polycarbonate (PC), polyoxymethylene (POM), polymethyl methacrylate (PMMA) and polyamide (PA) are also common in refrigerator production. Plastic, mainly used for door seals, lampshades, hinges, display panels and bushings.
Key plastic part molding process on refrigerator
Main plastics application
1, the door seal
Door seals are usually extruded from soft PVC. The typical production process is:
PVC powder, additive mixing â†’ granulation â†’ extrusion molding â†’ chamfering â†’ core penetration â†’ welding
The research on the structure and material of the door seal is to ensure the heat insulation effect of the door seal and seal, to achieve energy saving, and to ensure that the door seal is anti-mildew and antibacterial during use. In addition, the new door seal is also produced by the elastomeric die-casting process.
The liner is formed by vacuum forming ABS or HIPS material.
The contribution of the three components of ABS to performance is different.
A: Mainly contributes to chemical resistance and heat resistance;
B: Mainly contributes to impact resistance and toughness;
S: Mainly contributes to processability and rigidity.
Generally speaking, the rubber content increases, the impact strength increases, but the processing fluidity and photoaging performance decrease. When the acrylonitrile content increases, the chemical resistance and heat resistance increase, which is the biggest difference between ABS and HIPS.
The plastic forming of the refrigerator liner mainly has the following forms: male molding, negative molding, and vacuum forming. The vacuum forming process can create a more localized structure and save material.
Blister equipment: mainly linear and rotary multi-station blister machines, single-station blister machines, now mainly linear multi-station blister machines.
3, polyurethane insulation layer
The rigid PU foam is used in the insulation layer of the refrigerator. It is the key material related to the performance, structure and production process of the refrigerator. It is mainly based on isocyanate and polyether polyol, and then added various additives to infuse in the production site of the refrigerator. Foamed, the foaming agent mainly has R11, R141b, CO2, water and the like.
The different thermal conductivity of different blowing agents is the key performance of the polyurethane insulation layer. The main research direction of the fluorine-free foaming technology is to reduce the thermal conductivity of the foam and achieve energy saving.
The refrigerator box foaming equipment mainly includes: linear type and ground ring type; the refrigerator door body foaming equipment type mainly includes: crawler type and rotary type, and the box body infusion method has back board foaming and rear floor foaming.
4, door handle
The door handle of the refrigerator is usually made of ABS material. The structure of the handle reflects the shape of the door of the refrigerator. Therefore, the handle after injection is usually covered by the surface decoration process to meet the consumer's pursuit of the appearance of the refrigerator.
Surface decoration processes mainly include: electroplating, thermal transfer, hot stamping, pad printing, overprinting, and in-mold decoration. In-mold decoration is the most advanced surface decoration process to date. The secondary processing technology such as surface decoration and injection molding are completed once, and the quality is greatly improved. The in-mold decoration process is different from the ordinary injection molding process as follows:
1 There is a set of automatic foil feeding precision positioning device, which relies on the clamp or is equipped with vacuum adsorption to make the foil and the mold fit;
2 The mold thimble is designed on the same side as the gate.
5, refrigerator facade
Most of the refrigerator door panels have replaced the past painted or powdered metal panels with plastic coated steel sheets. The coated steel sheets are made of cold rolled steel sheets (CRS) or galvanized steel sheets (EG or GI). PVC pattern film can print various patterns to meet the needs of consumers. Due to different processing techniques and materials, there are some differences in the performance of coated steel sheets and powder-sprayed sheets. The typical processing techniques are as follows:
Substrate â†’ pretreatment â†’ coating â†’ composite PVC film â†’ paste protective film â†’ cut.
The common compressor cover is injection molded with PP. In recent years, the application of PP in refrigerators has been increasing, and in some cases it has been used to inject caps, drawer boxes, control panels, partitions, shelves, and the like. Due to its low density, it is beneficial to reduce the weight of parts and materials, and because of the improvement of polymerization process and blending modification, the processing property and physical and mechanical properties of PP are improved, so that the application of PP in refrigerators can replace PS in some occasions. , the trend of ABS.
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