The differences and characteristics of PVC, CPVC, UPVC, PP and FRP

PP (polypropylene)

Chemical name of PP plastic: polypropylene, English name: olypropylene (PP for short), specific gravity: 0.9-0.91 g/cubic centimeter, molding shrinkage: 1.0-2.5%, molding temperature: 160-220°C.

Features: non-toxic, odorless, low density, strength, stiffness, hardness and heat resistance are better than low-voltage polyethylene, can be used at around 100 degrees, has good electrical properties and high-frequency insulation and is not affected by humidity, but low temperature It becomes brittle over time, is not wear-resistant, and ages easily. Suitable for making general mechanical parts, corrosion-resistant parts and insulating parts. Common acid and alkali organic solvents have almost no effect on it and can be used in tableware.

Molding characteristics:

1. Crystalline material has low hygroscopicity, is prone to melt rupture, and is prone to decomposition in long-term contact with hot metal.

2. It has good fluidity, but has a large shrinkage range and value, and is prone to shrinkage holes, dents, and deformation.

3. The cooling speed is fast. The pouring system and cooling system should dissipate heat slowly, and pay attention to controlling the molding temperature. The material is easy to orient at low temperature and high pressure. The mold temperature is lower than 50 degrees. The plastic parts are not smooth and are prone to poor welding and flow marks. 90 Warping deformation is prone to occur above the degree.

4. The plastic wall thickness must be uniform to avoid lack of glue and sharp corners to prevent stress concentration.

PVC (polyvinyl chloride)

Basic characteristics: It is one of the most produced plastic products in the world. It is cheap and widely used. PVC resin is white or light yellow powder.

Different additives can be added according to different uses, and PVC plastic can exhibit different physical and mechanical properties. By adding an appropriate amount of plasticizer to PVC resin, a variety of hard, soft and transparent products can be made.

Rigid polyvinyl chloride has good tensile, bending, compression and impact resistance, and can be used alone as a structural material. The softness, elongation at break, and cold resistance of soft PVC will increase, but the brittleness, hardness, and tensile strength will decrease.

The density of pure PVC is 1.4g/cm3, and the density of PVC plastic parts with plasticizers and fillers added is generally 1.15-2.00g/cm3.

PVC has good electrical insulation properties, can be used as low-frequency insulation material, and its chemical stability is also good. Due to the poor thermal stability of polyvinyl chloride, long-term heating will cause decomposition, release of HCL gas, and discoloration of polyvinyl chloride. Therefore, its application range is narrow, and the use temperature is generally between -15 and 55 degrees.

Main uses: Polyvinyl chloride is synthesized from vinyl chloride by acetylene gas and hydrogen chloride, and then polymerized. It has high mechanical strength and good corrosion resistance. Due to its high chemical stability, it can be used to make anti-corrosion pipes, pipe fittings, oil pipelines, centrifugal pumps and blowers, etc. PVC hard boards are widely used in the chemical industry to make linings for storage tanks, corrugated boards for buildings, door and window structures, wall decorations and other building materials. Due to its excellent electrical insulation properties, it can be used in the electrical and electronic industries to manufacture plugs, sockets, switches and cables. In daily life, PVC is used to make sandals, toys, artificial leather, etc. When the plasticizer is added in an amount of 30% to 40%, soft polyvinyl chloride is produced, which has high elongation, soft products, good corrosion resistance and electrical insulation, and is often made into films for Industrial packaging, agricultural seedling cultivation and daily raincoats, insulation layers, etc.

The difference between PVC and UPVC is that UPVC is unplasticized and has higher strength.

CPVC (chlorinated polyvinyl chloride)

Chlorinated polyvinyl chloride (CPVC) is a new type of engineering plastic produced by chlorination modification of polyvinyl chloride (PVC) resin. The product is white or light yellow, tasteless, odorless, non-toxic loose granules or powder. After PVC resin is chlorinated, the irregularity of the molecular bonds increases and the polarity increases, which increases the solubility and chemical stability of the resin, thereby improving the material's heat resistance, acid resistance, alkali resistance, salt, oxidant resistance, etc. corrosion. The mechanical properties of numerical heat distortion temperature are improved, the chlorine content is increased from 56.7% to 63-69%, the Vicat softening temperature is increased from 72-82 ℃, (raised to 90-125 ℃), and the maximum use temperature can reach 110 ℃. The long-term use temperature is 95 ℃.

PVDF polyvinylidene fluoride

PVDF (Polyvinylidene fluoride), which is polyvinylidene fluoride, mainly refers to vinylidene fluoride homopolymer or copolymer of vinylidene fluoride and other small amounts of fluorine-containing vinyl monomers. It has the characteristics of both fluororesin and general-purpose resin. In addition to In addition to good chemical resistance, high temperature resistance, oxidation resistance, weather resistance, and radiation resistance, it also has special properties such as piezoelectricity, dielectricity, and thermoelectricity. It ranks second among fluorine-containing plastics in terms of output. It is a large-scale product with a global annual production capacity of more than 53,000 tons.

PVDF is a PVDF fusible fluorocarbon resin for coatings made from the homopolymerization of vinylidene fluoride (VDF) with a purity of ≥99.99%. The paint film made of fluorocarbon paint made of 70% PVDF resin and baked through spraying or roller coating has unparalleled super weather resistance and processing performance. It fully complies with the American building materials standard AAMA2605 and the People's Republic of China industry standard HG/T3793-2005. PVDF not only has strong wear resistance and impact resistance, but also has high fading resistance and UV resistance in extremely harsh and harsh environments.

Product Features:

1. Fluorinated resin that can be injected and extruded (commonly known as thermoplastic Teflon).

2. Excellent chemical resistance.

3. Wear-resistant, high mechanical strength and toughness.

4. Weather-resistant, resistant to ultraviolet rays and nuclear rays.

5. Good heat resistance and high dielectric strength.

Usage: Chemical-resistant parts, wires and cables, etc.

FRP (fiber reinforced composite plastic)

FRP (Fiber Reinforced Plastics), fiber reinforced plastics, generally refers to the matrix of unsaturated polyester, epoxy resin and phenolic resin reinforced with glass fiber, commonly known as fiberglass.

FRP has the following characteristics:

1.Lightweight and high strength

The relative density is between 1.5 and 2.0, which is only 1/4 to 1/5 of carbon steel. However, the tensile strength is close to or even exceeds carbon steel, and the specific strength can be compared with high-grade alloy steel. Therefore, it has excellent results in aviation, rockets, spacecraft, high-pressure vessels and other products that need to reduce their own weight. The tensile, bending and compressive strength of some epoxy FRP can reach more than 400Mpa. Note: Specific strength is intensity divided by density.

2. Good corrosion resistance

FRP is a good corrosion-resistant material and has good resistance to the atmosphere, water, general concentrations of acids, alkalis, salts, and various oils and solvents. It has been applied to all aspects of chemical anti-corrosion and is replacing carbon steel, stainless steel, wood, non-ferrous metals, etc.

3. Good electrical performance

FRP is an excellent insulating material used to make insulators. Good dielectric properties can still be protected at high frequencies. It has good microwave permeability and has been widely used in radar radomes.

4.Good thermal performance

The thermal conductivity of FRP is low, 1.25~1.67kJ/(m·h·K) at room temperature, which is only 1/100~1/1000 of metal. It is an excellent thermal insulation material. Under instantaneous ultra-high temperature conditions, it is an ideal thermal protection and ablation-resistant material, which can protect spacecraft from being washed away by high-speed airflow at temperatures above 2000°C.

5. Good designability

① Various structural products can be flexibly designed according to needs to meet the use requirements, which can make the product have good integrity.

② Materials can be fully selected to meet the performance of the product. For example, materials can be designed to be corrosion-resistant, resistant to instantaneous high temperatures, have particularly high strength in a certain direction of the product, have good dielectric properties, etc.

6.Excellent craftsmanship

① The molding process can be flexibly selected according to the shape, technical requirements, use and quantity of the product.

② The process is simple, can be formed in one go, and has outstanding economic effects. Especially for products with complex shapes and small quantities that are difficult to form, its process superiority is highlighted.

One type of FRP cannot be required to meet all requirements. FRP is not a panacea. FRP also has the following shortcomings.

1. Low elastic modulus

The elastic modulus of FRP is twice larger than that of wood, but 10 times smaller than steel (E=2.1×106). Therefore, the rigidity of FRP is often insufficient in product structures and it is easy to deform.

It can be made into a thin shell structure or a sandwich structure, or it can be compensated for by high modulus fibers or reinforcements.

2. Poor long-term temperature resistance

Generally, FRP cannot be used for a long time at high temperatures. The strength of general-purpose polyester FRP drops significantly above 50°C, and is generally only used below 100°C. The strength of general-purpose epoxy FRP drops significantly above 60°C. However, high-temperature-resistant resin can be selected to make long-term working temperatures between 200 and 300°C possible.

3. Aging phenomenon

Aging is a common defect of plastics, and FRP is no exception. It can easily lead to performance degradation under the action of ultraviolet rays, wind, rain, snow, chemical media, mechanical stress, etc.

4. Low interlayer shear strength

The interlaminar shear strength is borne by the resin, so it is very low. The interlayer adhesion can be improved by selecting processes, using coupling agents, etc. The most important thing is to avoid shearing between layers during product design.