Polypropylene (4 sheets)
polypropylene
Trademark name: such as Asota? Asota gmbh
Maximum continuous working temperature
drying condition
90 ? C
Maximum peak temperature
100 ? C
Special density
0.9 1 g/cm?
strength of extension
About 120- 150 Dan/5cm.
melting temperature
162 - 176 ? C
moisture absorption
0%
LOI (limiting oxygen index)
18
characteristic
superiority
Strong acid and alkali resistance
Strong ability to prevent organic solvents.
Low special density
disadvantaged
Low maximum working temperature
It is easy to age during oxidation.
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applied range
Automobile industry (mainly uses PP containing metal additives: fenders, ventilation pipes, fans, etc. ), instruments (dishwasher door gasket, dryer ventilation pipe, washing machine frame and cover, refrigerator door gasket, etc. ), daily consumer goods (lawn and gardening equipment such as lawn mowers, sprinklers, etc. ).
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Molding characteristics
1. Crystalline substance, low hygroscopicity, easy to melt, fracture and decompose when in contact with molten iron for a long time.
2. The fluidity is good, but the shrinkage range and shrinkage value are large, which is prone to shrinkage cavity, dent and deformation.
3. The cooling speed is fast. The cooling of gating system and cooling system should be slow, and the molding temperature should be controlled. The material temperature is easy to orient at low temperature and high pressure. When the mold temperature is lower than 50 degrees, the plastic parts are not smooth, and it is easy to produce poor welding and flow marks, and it is easy to warp and deform above 90 degrees.
4. The plastic wall thickness should be uniform, avoiding lack of glue and sharp corners and preventing stress concentration. [ 1]
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Process condition
Drying treatment: if stored properly, drying treatment is not needed.
Melting temperature: 220~275℃, be careful not to exceed 275℃.
Mold temperature: 40~80℃, 50℃ is recommended. The crystallinity is mainly determined by the mold temperature.
Injection pressure: up to 1800 bar.
Injection speed: Generally, high-speed injection molding can minimize the internal pressure. If the product surface is defective, low-speed injection molding at higher temperature should be adopted.
Runner and gate: For cold runner, the typical runner diameter is 4 ~ 7 mm. It is recommended to use circular injection port and runner. All types of gates can be used. Typical gate diameters range from 1 to 1.5 mm, but gates as small as 0.7 mm can also be used. For the side gate, the minimum gate depth should be half of the wall thickness; The minimum gate width should be at least twice the wall thickness. PP material can completely use hot runner system.
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Correlation characteristic
PP is a semi-crystalline material. It is harder and has a higher melting point than PE. because
Polypropylene products
Homopolymer PP is very brittle when the temperature is higher than 0℃, so many commercial PP materials are random * * * polymers and block * * * polymers with ethylene content of 1~4% or higher. * * * Polymer-based PP material has low thermal deformation temperature (100℃), low transparency, low gloss and low rigidity, but strong impact strength. The strength of polypropylene increases with the increase of ethylene content. The Vicat softening temperature of polypropylene is 65438 050℃. Because of its high crystallinity, this material has good surface hardness and scratch resistance. PP has no problem of environmental stress cracking, and it is usually modified by adding glass fiber, metal additives or thermoplastic rubber. The range of MFR of PP is 1~40. PP with low MFR has better impact resistance, but lower tensile strength. For materials with the same MFR, the strength of polymer type is higher than that of homopolymer type. Due to crystallization, the shrinkage of PP is quite high, generally 1.8~2.5%. And the directional uniformity of shrinkage is much better than that of PE-HD and other materials. Adding 30% glass additive can reduce the shrinkage to 0.7%. Both homopolymer and polymer PP materials have excellent moisture absorption resistance, acid and alkali corrosion resistance and solubility resistance. But it is not resistant to aromatic hydrocarbon (such as benzene) solvents and chlorinated hydrocarbon (carbon tetrachloride) solvents. The oxidation resistance of PP at high temperature is not as good as that of PE. [2]
Polypropylene (PP) is a lightweight plastic with excellent electrical properties, which can be used as a high-frequency insulation material with high moisture resistance. Polypropylene is a crystalline polymer. When the melt is condensed, it shows a large shrinkage rate (1.0%- 1.5%) due to the large change of specific volume and high molecular orientation. In the molten state, the effect of reducing the viscosity of PP by increasing the temperature is not significant. Therefore, in the molding process, the injection pressure and shear rate should be mainly increased to improve the molding quality of products. 0.94 g/cm
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line production
1, the pressure and melt flow process required in each stage of PP molding.
Polypropylene products
PP molding mainly includes mold filling stage, densification stage, pressure maintaining stage and cooling stage. The pressure required for each stage is different, and the melt flow is also different.
1. 1 mold filling stage
Polypropylene is heated and preformed in the barrel of injection molding machine and melted. At the beginning of injection molding, it is a high-pressure and high-speed mold filling process under the action of dynamic pressure from the injection pressure generated by the screw head to the melt filling the mold cavity. At this time, the flow of high-temperature melt in the mold cavity largely determines the surface quality and physical properties of the product, and the flow of melt is affected by injection pressure and melt itself. When the injection pressure is too low, the melt will slowly enter the mold cavity, and the layer of melt near the inner wall of the mold cavity will solidify due to the rapid drop of temperature and the increase of viscosity, and will soon spread to the center, making the flow channel of melt narrow in a short time, greatly weakening the flow of melt entering the mold cavity, resulting in ripples, lack of materials and bubbles on the surface of the product. When the injection pressure is too high, the melt fills the mold too fast, enters the mold cavity in the form of turbulence near the gate, and free injection occurs, and the gas in the mold cavity cannot be exhausted, and defects such as cloud spots appear on the surface of the product, and the residual stress of product demoulding is large, which is easy to produce flash and difficult to demould. Although high injection pressure can improve the injection rate and obtain a large shear effect during injection. So as to reduce the viscosity of the melt, but physically speaking, too high pressure will increase the viscosity of the melt, because with the increase of pressure, the distance between molecular chains will be compressed, the dislocation between molecular chains will be more difficult, the melt flow will be difficult, and the viscosity will also increase. Therefore, in the mold filling stage, we should pay attention to the role of high-speed injection, that is, high shear rate, rather than blindly increasing injection pressure. For some high-grade products with large wall thickness variation and flange and rib thickness, multi-stage injection molding should be used to control the shear rate. In actual production, it is generally adjusted to low speed and low pressure to make the melt enter the mold smoothly; Then, two different high-speed and high-pressure are used to make the melt almost fill the mold cavity and prevent the generation of eddy current; Finally, the first stage of low speed and medium pressure is used to avoid flash, so as to successfully complete the filling process.
1.2 densification stage
After mold filling, the rapid flow of PP melt stopped, the cavity pressure began to increase, and the injection pressure also increased rapidly. When the injection pressure reaches the maximum, the cavity pressure does not reach the maximum, and the extreme value of the cavity pressure lags behind the maximum injection pressure for a period of time, during which the melt flow process is a densification process. In this short time, the melt will fill all the gaps in the mold cavity and it will be compressed. The flow rate of melt is very small and the temperature change is not obvious. At this time, the injection pressure is also transferred to the surface of the mold cavity by the melt, resulting in the mold cavity pressure (the difficulty of transfer depends on the fluidity of the melt). It can be said that the maximum injection pressure determines the maximum cavity pressure during injection densification. With the rapid increase of injection pressure, the pressure in the mold cavity also reaches the maximum, and there is a great kinetic energy impact in the mold cavity, which makes the clamping mechanism and mold system of the injection molding machine deform and makes the mold expand slightly. Under normal deformation conditions, the micro-expansion of the mold has the function of deflation, so it is necessary to inject at higher pressure, which can not only compact the melt, but also integrate the viscous melt that fills the mold cavity from different directions. But the injection pressure should not be too high, otherwise the product will stick to the mold, and the product will overflow after being ejected, which will affect the molding quality.
1.3 pressure maintaining stage
In the pressure maintaining stage, the pressure and specific volume of PP melt in the mold cavity changed continuously (the specific volume of PP changed to 16%) until the gate was closed. The main factor affecting the pressure holding process is pressure. Holding pressure can make the melt in the mold cavity always get enough pressure and feeding before it is completely solidified, so that the melt can flow, which is characterized by the slow flow rate due to the cooling shrinkage of the melt. Because when the injection temperature is lowered to the mold temperature, the macromolecules in PP melt will relax and crystallize, and the volume shrinkage rate will be large, so it is necessary to overcome the gate resistance and have enough holding pressure for feeding. The increase of holding pressure will also increase the density of the product, reduce the degree of free change of the surface after the product is taken out of the die, obtain the surface roughness close to the die surface, reduce the molding shrinkage, enhance the fusion between various parts of the melt and improve the mechanical properties of the product. Generally, the holding pressure can be 60-70% of the highest injection pressure. In order to improve the molding quality of products, sectional pressure keeping can also be used for pressure control.
Holding time is another important process parameter in the process of holding pressure. At the initial stage of pressure holding, the product weight increases with the increase of pressure holding time, and does not increase after a certain period of time. Prolonging the holding time is helpful to reduce the shrinkage of the product, but too long holding time will make the radial shrinkage of the product different from the axial shrinkage, increase the internal stress difference in all directions of the product, and cause the product to warp and stick to the mold. When the holding pressure and melt temperature are constant, the choice of holding time should depend on the solidification time of the gate.
1.4 cooling stage
After the holding, the holding pressure is released, and the pressure in the runner drops sharply, which is much lower than that in the die cavity. At this point, although the door is closed, it has not completely solidified. Under the action of the pressure in the cavity, the melt in the cavity will flow back to the gating system, and the pressure in the cavity will drop rapidly until the channel between the cavity and the runner is blocked by the gradually solidified melt (the pressure and temperature in the cavity when blocked are called sealing pressure and sealing temperature), and the backflow will stop. At this time, although the amount of melt in the mold cavity does not change, it has two opposite effects, one is the cooling shrinkage of melt, the other is the decompression expansion, and the two effects are contradictory. If shrinkage is dominant, the product will soon leave the surface of the mold cavity, and under the action of residual heat, the surface of the product will appear defects such as fog, pitting and dullness. If expansion is dominant, it will cause defects such as die sticking and die opening strain. The production practice shows that when the sealing temperature is constant, the higher the sealing pressure, the higher the product density and the more obvious the expansion after pressure relief. When the sealing pressure is constant, the higher the sealing temperature, the smaller the product density and the more obvious the cold shrinkage effect. In order to avoid these two effects, the heat preservation time should be prolonged, with the aim of controlling the sealing pressure and reducing the sealing temperature, so as to obtain high-quality products.
With the extension of cooling time, the solidified layer of the product becomes thicker, and the melt in the mold cavity no longer flows under the action of external pressure, but conducts heat until the product has enough rigidity to leave the mold.
2. Conclusion
(1) In the mold filling stage, attention should be paid to adjusting the injection pressure and injection rate to make them match properly, so as to control the shear rate and make the linear velocity of each point of the melt close to the same in the process of advancing into the mold cavity.
(2) Densification stage is the stage where injection pressure is transferred to the cavity and cavity pressure is generated. Injection pressure determines the cavity pressure, and only when the injection pressure is relatively high can the melt be compacted into a whole.
(3) In the holding stage, the holding pressure should be controlled to achieve the purpose of feeding the mold cavity. Generally speaking, the holding pressure can be 60%-70% of the highest injection pressure.
(4) In the cooling stage, the melt in the mold cavity will flow backwards, and the pressure in the mold cavity will drop. Controlling sealing pressure and reducing sealing temperature are helpful to improve the molding quality of products.
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Characteristic application
I. Characteristics
1, corrosion resistance
2. Corrosion resistance
3, portability and low density
4, high temperature resistance
5, anti-aging, the service life of PE is relatively short.
6, excellent surface finish
7. Sufficient thermal stability
8. Low melting rate, excellent surface smoothness and good food grade recognition.
9. low price
Second, the application
1, chemical storage tank manufacturing and processing
2, high acid-base solution storage
3. Processing equipment and building materials
4. Electronic plating equipment container
5, experimental equipment and appliances
6. General processing instruments and equipment
7. Scrubbers, air filtration systems and duct systems
8. Waste gas treatment and washing system
9, circuit board pickling equipment
10, electroplating bath
1 1, medical application components
12, computer digital machining center and precision equipment parts
13, transportation
Third, the application industry.
1, chemical processing industry
2. Surface treatment industry
3. Medicine
4. Life sciences
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technical parameter
Taking ITW FORMEX GK- 10 as an example, the technical parameters of polypropylene sheet are introduced:
1, color: white;
2, mechanical properties:
Tensile yield: longitudinal direction: 4400 psi (test method: ASTM D-822)
TD: 3200 psi (test method: ASTM D-822)
3. Physical properties:
Thickness: 0.25mm.
Density:1.035g/cm3
Fire rating: 94VTM-0
Oxygen index: 29 (test method: ASTM D-2863)
Water absorption: 0.06% (test method: ASTM D-576)
Thermal deformation temperature (under the pressure of 66 pounds): 12 1℃ (test method: ASTM D-576).
Relative temperature index (RTI): 1 15℃ (test method: UL746B).
Surface energy: surface energy? 50 dynes/cm (test method: ASTM D-2578)
4. Electrical properties:
Dielectric breakdown voltage: 22,000 volts (test method: ASTM D- 149)
Insulation strength: 2200 volts/inch (test method: ASTM D- 149).
Insulation resistance: 3.97* 10 (test method: ASTM D-257)
Dielectric constant: 2.3 (test method: ASTM D- 150)
Dissipation factor: 0.00 19 (test method: ASTM D- 150)
High current melting rate (hai): 200 (test method: 746A)
Hot wire melting speed (HWI): 7 seconds (test method: UL 746A)
Comparative path index (CTI): 600 volts (test method: ASTM D-3638).
The above is a detailed introduction of PP Nordic Chemical Hoe 1 1NP, including the price, model, pictures and manufacturers of PP Nordic Chemical Hoe11NP!
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