Differences and characteristics of PVC, CPVC, UPVC, PP and FRP
1.PP (polypropylene)
PP plastic, chemical name: polypropylene
English name: olyi lene (PP)
Weight: 0.9 to 0.91 grams per cubic centimeter Molding shrinkage rate: 1.0 2.5% molding temperature: 160-220 ℃
Features: non-toxic, tasteless, density is small, the strength stiffness, hardness, heat resistance are better than that of low pressure polyethylene, can be used in 100 degrees. It has good performance and high frequency insulation is not affected by humidity, but low temperature time-varying crisp, wear-resisting, easy to aging. Suitable for making general machinery parts, corrosion parts and insulation parts. Common acid and alkaline organic solvents have little effect on it and can be used for food.
Molding characteristics:
a. Crystallization material, small moisture absorption, easy to occur melt fracture, long – term and hot metal contact with easy decomposition.
b. Good fluidity, but the contraction scope and shrinkage value are large, prone to shrinkage cavity. Concave mark, deformation.
c. The cooling speed, gating system and cooling system should slow cooling, and pay attention to control the molding temperature. Easy orientation when low temperature temperature high pressure, mold temperature is lower than 50 degrees, the plastic parts is not smooth, easy to cause weld adverse, flow mark, 90 degrees or more prone to buckling deformation
d. The thickness of plastic wall should be uniform, avoiding the lack of glue and sharp Angle, in case of stress concentration.
2. PVC (PVC)
Basic features:
It is one of the world’s most productive plastic products, cheap and widely used, and polyvinyl chloride resin is white or light yellow powder. Different additives can be added to different USES, and polyvinyl chloride plastics can show different physical properties and mechanical properties. In polyvinyl chloride resin, a suitable amount of plasticizer can be made into a variety of hard, soft and transparent products.
The density of pure polyvinyl chloride is 1.4g/cm3, and the density of polyvinyl chloride plastic parts, such as plasticizer and filler, is generally 1.15-2.00 g/cm3.
Hard polyvinyl chloride has good tensile, anti-bending, anti-pressure and impact resistance, but can be used as structural material alone.
Soft polyvinyl chloride’s flexibility, elongation and cold tolerance will increase, but brittleness, hardness and tensile strength will decrease.
Polyvinyl chloride has good electrical insulation properties and can be used as low-frequency insulation material, and its chemical stability is good. Due to the poor thermal stability of polyvinyl chloride (PVC), heating for a long time can lead to decompose, release HCL gas, discoloring the polyvinyl chloride (PVC), so its application scope is narrow, using temperature generally between 15 to 55 degrees.
Main USES:
Due to its high chemical stability, it can be used in the production of anticorrosive pipes, fittings, pipelines, centrifugal pumps and blower. The hard board of polyvinyl chloride is widely used in the chemical industry to make the lining of various storage tanks, the corrugated board of the building, the structure of the doors and Windows, the wall decorations and other building materials. Due to excellent electrical insulation performance, it can be used in electrical and electronic industries to make plugs, sockets, switches and cables. In daily life, polyvinyl chloride is used to make sandals, raincoats, toys and artificial leather.
Polyvinyl chloride (PVC)
Polyvinyl chloride is synthesized from acetylene gas and hydrogen chloride. It has high mechanical strength and good corrosion resistance. It can be used in the production of chemical, textile and other industrial waste gas discharge tower, gas liquid conveying pipe, and can replace other corrosion-resistant materials manufacturing storage tank, centrifugal pump, ventilator and joint, etc. When 30% ~ 40% for the amount of plasticizer, then made of soft PVC, the elongation rate is high, the products are soft, and has good corrosion resistance and electrical insulation, often made into film, used in industrial packaging, agricultural base and daily raincoat, table cloth, etc., can also be used for production of acid and alkali resistant hose, cable sheathing, insulation, etc.
The difference between PVC and UPVC is that UPVC is not plasticized and its strength is higher.
3.cpvc resin
It is modified by PVC resin and is a new type of engineering plastics. The product is white or light yellow tasteless, odorless, non-toxic loose particles or powders. After chloride, PVC resin molecular bonds of irregularity, polarity, increased solubility of the resin, chemical stability, so as to improve the heat resistance of the material, acid, alkali, salt corrosion, antioxidant, etc. Improved numerical mechanical properties, thermal deformation temperature of the chlorine content increased by 56.7% to 63-56.7%, vicat softening temperature from 72-72 ℃, (90-90 ℃), the highest temperature can reach 110 ℃, the long using temperature is 95 ℃.
4. FRP(Fiber Reinforced Plastics)
namely Fiber Reinforced plastic, generally refers to the glass Fiber Reinforced unsaturated polyester, epoxy resin and phenolic resin matrix, commonly known as FRP. FRP has the following characteristics.
(1) light quality and high strength
The relative density is between 1.5~ 2.0, only 1/4-1/5 of carbon steel, but the tensile strength is close to, or even more than carbon steel, compared with the strength of the high alloy steel. Therefore, in aviation, rockets, space vehicles, high pressure vessels, and in other products that need to reduce weight, they have excellent results. The tensile, bending and compression strength of certain epoxy FRP can reach over 400Mpa. Note: ratio strength is intensity divided by density.
(2) good corrosion resistance
FRP is a good corrosion resistant material with good resistance to acid, alkali, salt and various oils and solvents of the atmosphere, water and general concentration. It has been applied to various aspects of chemical preservative, replacing carbon steel, stainless steel, wood, nonferrous metal etc.
(3) good electrical performance
Is a fine insulating material used to make an insulator. High frequency can still protect good dielectric. Microwave transmission is good and has been widely used in radar radome.
(4) good thermal performance
The thermal conductivity of FRP is low, at room temperature is 1.25~1.67 kJ/(m &# 8226). H & # 8226; K) only 1/100~1/1000 of the metal is a good insulator. Under the condition of the instantaneous ultra high temperature, is the ideal thermal protection and ablation resistant material, can protect the spacecraft at above 2000 ℃ under high-speed air flow.
(5) good design
The product can be flexibly designed according to the need to meet the requirements of use, so that the products can be well integrated.
The materials can be fully selected to meet the performance of the products, such as: can be designed to resist the corrosion, the instantaneous high temperature, the products in a certain direction have special high strength, the dielectric good, and so on.
(6) excellent technology
It can choose the forming process flexibly according to the product’s shape, technical requirement, use and quantity.
The process is simple, can be formed at once, the economic effect is outstanding, especially to the shape complex, the quantity of not easy to form is small, highlight its technological superiority.
The FRP cannot be required to meet all requirements. FRP is not omnipotent, and FRP has the following shortcomings.
(1) low elastic modulus
The elastic modulus of FRP is twice as large as that of wood, but it is 10 times smaller than that of steel (E =2.1 * 106). Therefore, it is often rigid in product structure and easy to deform.
It can be made into thin shell structure, sandwich structure, and can be made up by high modulus fiber or reinforcement.
(2) poor long-term temperature tolerance
General FRP can use for a long time at high temperature, general polyester FRP above 50 ℃ intensity is decreased obviously, generally only used in under 100 ℃; General-purpose epoxy FRP above 60 ℃, intensity is decreased obviously. But can choose high-temperature resistance resin, make long-term working temperature at 200 ~ 300 ℃ is possible.
(3) aging phenomenon
The aging phenomenon is a common defect of plastics, and FRP is no exception, which can lead to the degradation of performance under uv, wind yarn, rain and snow, chemical media, mechanical stress, etc.
(4) low shear strength between layers
The shear strength between layers is assumed by resin, so it is very low. By selecting process and using coupling agent, we can improve the bonding force between layers. The main thing is to avoid the interlayer shear when designing the product.
