Comparison of Characteristics and Main Uses of Several Commonly Used Plastic PipesW
PVC pipe features good tensile strength and compressive strength, but its flexibility is not as good as other plastic pipes, and its corrosion resistance is excellent. The price is the cheapest in all kinds of plastic pipes, but the brittle connection method at low temperature is bonding and socketing. The apron connection and flange connection are mainly used for water supply and drainage, irrigation, gas supply and exhaust pipes, wire conduits, rainwater pipes, and industrial anticorrosive pipes in residential life, industrial and mining, and agriculture.
CPVC pipe Features outstanding heat resistance, heat distortion temperature of 100 °C, excellent chemical resistance. Bonding, flanged threaded connection. Mainly used for hot water pipe
PE pipe features light weight, good toughness, good low temperature resistance, non-toxic, cheaper, high impact strength, but low compressive strength, low tensile strength. Connections Hot melt welding, flanged thread connection is mainly used for drinking water Pipes, rainwater pipes, gas pipes, industrial corrosion-resistant pipes
PP pipe features good corrosion resistance, good strength, high surface hardness, surface finish, and a certain degree of high temperature resistance. Connection method Hot melt welding, flanged screw connection is mainly used for chemical sewage, seawater, oil and irrigation The pipes are used for indoor concrete floor heating pipes for heating systems.
ABS pipe features excellent corrosion resistance, lighter weight, heat resistance than PE, PVC, but the price is more expensive. Connection type bonding, flanged screw connection Mainly used for sanitary ware plumbing, sewerage, sewage pipe, underground cable pipe, high anti-corrosion industrial pipe, etc.
The strength of PB pipe is between PE and PP, and the flexibility is between LDPE (LDPE: low density polyethylene) and HDPE (HDPE: high density polyethylene). Its prominent feature is creep resistance (cold deformation), repeated Continuous winding, temperature resistance, chemical properties are also very good connection Hot-melt welding, flanged screw connection is mainly used for water supply pipes, hot and cold water pipes, gas pipes, underground buried high pipe
GRP pipe Excellent corrosion resistance, light weight, high strength, good designability Connection method Socking apron connection, flange connection widely used petrochemical pipelines and large diameter water supply and drainage pipelines
How to identify PP pipe?
1. "Touch": whether the texture is delicate and whether the particles are even. At present, PPR pipes in the market are mainly in several colors of white, gray and green. Under normal circumstances, recycled plastics cannot be made white, so consumers often think that white is the best. In fact, this view is one-sided. As technology has improved, color is not a good standard for distinguishing PP-R tubes. The quality of the pipe can't solve the problem. If it is touched, the rough particles are likely to be mixed with other impurities.
2. "Smell": There is no smell. The main material of the PP-R pipe is polypropylene. Good pipes have no odor. Bad ones have strange smells. They are very willing to blend polyethylene instead of polypropylene.
3. "Pinch": PP-R pipe has a considerable hardness, you can easily deform into a deformed tube, certainly not PP-R pipe.
4. "砸": A good PP-R tube, "Resilience" is good, too easy to break up is not a good PP-R tube. However, the hardness is not equal to the flexibility, and consumers will have questions about PP-R tubes that are not broken. Because some unscrupulous manufacturers increase the hardness of pipes by adding too many impurities such as calcium carbonate, such pipes are prone to embrittlement for a long time.
5. "Burn": Igniting a fire, very intuitive and very useful. PP-R tubes containing recycled plastics and other impurities in the raw materials will emit black smoke and have a pungent odor; good materials will not only emit black smoke and odor after burning, but the burnt-out liquid will remain clean after burning.
How to identify PVC?
PVC conventional identification methods are generally classified into the following three categories, namely:
1
Identification of combustion method:
Softening or melting temperature range: 75~90°C;
Burning situation: difficult to soften;
Burning flame state: There is smoke on the yellowish green; after the fire: away from the fire; odor: pungent sourness.
This method is the most simple and straightforward and generally preferred.
2
Solvent treatment identification:
Solvents: tetrahydrofuran, cyclohexanone, methyl ketone, dimethylformamide;
Non-solvents: methanol, acetone, heptane.
Add the suspected PVC plastic to the above solvent and observe the dissolution of the plastic to determine if it is PVC. Solvent heating, the dissolution effect will be more apparent.
3
Specific gravity method:
The proportion of PVC is 1.35 to 1.45, which is generally about 1.38.
Differentiating the specific gravity or determining the specific gravity can distinguish between PVC and other plastics.
However, due to PVC can add plasticizers, modifiers and fillers, so that the proportion of PVC becomes very different, the difference is very hard and soft, but also due to the addition of some ingredients, so that a lot of performance changes in PVC plastic, resulting in Our commonly used identification methods have no obvious effect, and even the phenomenon has changed, and we cannot make accurate judgments. For example, in terms of density, plasticized polyvinyl chloride (about 40% plasticizer) was 1.19 to 1.35; while PVC hard products increased to 1.38 to 1.50. If it is a high-filled PVC product, the density sometimes exceeds 2.
4
Determined by the determination of chlorine in the material
In addition, it can also be determined by determining whether the material contains chlorine, but because vinyl chloride copolymers, neoprene, polyvinylidene chloride, chlorinated polyvinyl chloride, etc. contain a higher proportion of chlorine, but also through the pyridine color Reaction to identify. Note that prior to the test, the sample must be extracted with ether to remove the plasticizer. Test method: The sample taken from ethyl ether benzene is dissolved in tetrahydrofuran, insoluble components are filtered off, and precipitated by adding methanol, after extraction Degrees of dryness below. A small amount of the dried sample was reacted with 1 ml of pyridine. After a few minutes, 2 drops of sodium hydroxide in methanol (1 g of sodium hydroxide dissolved in 20 ml of methanol) were added to the field, and the color was immediately observed. 5 min. Observe them again after 1 h. According to the color, different chlorine-containing plastics can be identified.
In daily life, the contact with more need to be resolved is the PVC and PE plastic film (bag), simple method:
1
Touch method
The hand feels a sense of lubrication, and the surface is coated with a layer of wax (chemically known as wax). This is a non-toxic polyethylene film bag, while the PVC film is slightly sticky to the touch.
2
Dither method
Shake hands, sound crisp, easy to float is a polyethylene film bag. In the case of hand-shake, the sound is low, and it is a PVC film bag.
3
Combustion method
It is flammable in the event of fire, the flame is yellow, there is a drop of waxy oil when burning, and there is gas when the candle burns. It is a non-toxic polyethylene film bag. If it is not flammable, the fire will extinguish and the flame will be green. It is a PVC film bag.
4
Water immersion method
When the plastic bag is immersed in water and pressed into the water by hand, the surface of the water can be expressed as polyethylene, and the PVC that sinks into the bottom is polyvinyl chloride (the density of polyethylene is less than water, the density of polyvinyl chloride is greater than water; about room temperature, respectively). 0.92 g/cm3 and 1.4 g/cm3).
It is also advisable to take one piece of copper wire and burn it red in the fire. Then, the copper wire is brought into contact with the test plastic film to produce a chemical change, and then the copper wire containing the plastic component is put back into the flame. At this time, it is necessary to carefully observe, if there is colorful, dazzling green flame, it shows that this plastic material contains chlorine, which belongs to PVC materials.
