olefin random polymer is also a kind of polypropylene, and the basic structure of its polymer chain is modified by adding different kinds of monomers. Ethylene is the most commonly used monomer, which changes the physical properties of polypropylene. Compared with pp homopolymer, random * * * polymer has improved optical properties (increased transparency and reduced haze), improved impact resistance, increased flexibility, and reduced melting temperature, thus reducing thermal welding temperature; At the same time, it is basically the same as homopolymer in chemical stability, water vapor isolation performance and organ sensory performance (low odor and taste). Used in the fields of blow molding, injection molding, film and sheet extrusion processing, as food packaging materials, medical packaging materials and daily consumer goods.
Edit this paragraph PPR- Basic Introduction
The English name of PPR is Pentaricopeptide Repeats PP-R, also known as Type III polypropylene pipe and random polypropylene, which is extruded into pipes and injected into pipes. It is a new plastic pipeline product developed and applied in Europe in the early 199s. At the end of 198s, about 5% PE was randomly and uniformly polymerized (random * * * polymerization) in the molecular chain of PP-R by gas phase * * * polymerization process, and became a new generation of pipeline materials. It has high strength, good impact resistance and long-term creep performance. At the same time, the pipeline has excellent chemical corrosion resistance and is insoluble in any known solvent at room temperature, so it is more suitable for conveying chemical fluids in chemical plants and other places besides home decoration. The service life can reach 5 years, and there is no cheaper material on the market to replace it.
edit PPR- chemical structure in this paragraph
PP random * * * polymers generally contain 1-7% by weight of ethylene molecules and 99-93% by weight of propylene molecules. In the polymer chain, ethylene molecules are randomly inserted in the middle of propylene molecules. In this random or statistical * * * polymer, most of the ethylene (usually 75%) is incorporated by monomolecular insertion, which is called X3 group (three consecutive ethylene [〔CH2〕] are arranged on the main {TodayHot} chain in turn), which can also be regarded as an ethylene molecule inserted between two propylene molecules. Another 25% of ethylene is incorporated into the main chain by multi-molecular insertion, also called X5 group, because there are five continuous methylene groups (two ethylene molecules are inserted between two propylene molecules together). It is difficult to distinguish X5 from higher groups such as X7 and X9. In view of this, the ethylene content of XS and higher groups is counted as > ＞X3％%. The randomness ratio x3/X5 can be determined. When the percentage of groups above X3 is large, the crystallinity of * * * polymer will be significantly reduced, which has a great influence on the final properties of random * * * polymer. The effect of extremely high ethylene content in * * * polymer on the crystallinity of polymer is similar to that of high random polypropylene content. Random PP*** polymers are different from homopolymers because ethylene molecules randomly inserted into the polymer backbone hinder the crystalline arrangement of polymer molecules. The decrease of crystallinity of * * * polymer leads to the change of physical properties: compared with PP homopolymer, random * * * polymer has lower stiffness, higher impact resistance and better transparency. Ethylene * * * polymers also have a low melting temperature, which has become their advantage in some applications. Random * * * polymers contain more leather and random PP, and polymer chains with much higher ethylene content. Depending on the different polymerization process, this high content of leather can be found in all commercial * * * polymer materials to varying degrees, which makes it difficult to meet the {HotTag} regulations of the Federal Food Administration (FDA) on food contact.
edit PPR- manufacturing method in this paragraph
The ethylene/propylene random polymer is prepared by simultaneous polymerization of ethylene molecules and propylene molecules, and the reactor used is the same as that used to produce PP homopolymer. The molecule of ethylene is smaller than that of propylene, and the reaction is faster than that of propylene (the reaction activity is about ten times). This weakens the stereospecificity of the catalyst and increases its activity, which leads to an increase in the amount of random polypropylene. In order to reduce the formation of this kind of random substance, it is necessary to lower the reaction temperature, thus reducing the activity of the catalyst and reducing the content of random isomers in the final product, so as to obtain a product with more balanced performance. The random polymer with high ethylene content (> 3%) is difficult to handle in the production process, and it is also difficult to polymerize in hexane diluent, because the secondary by-products of the reaction (random polypropylene and polymer with high ethylene content) can be dissolved in hexane. This is also true in bulk polymerization of liquid propylene, although the solubility is low. A large number of by-products produced by hexane dilution process must be separated in hexane recycling stage, which will increase the total production cost, but a cleaner polymer with a small amount of soluble components can be obtained. In the bulk polymerization process, these impurities will remain in the polymer and bring trouble when dealing with flaky materials. Moreover, the final poly product contains more soluble impurities. Using organic solvent for secondary cleaning can remove most impurities, but it will increase the total production cost of * * * polymer. Generally speaking, when the by-product content is high, the flaky random polymer will become sticky, and this problem is more prominent when the ethylene content is higher than 3.5% by weight. The decrease of melting point of * * polymer is directly related to ethylene content. It is reported that when the ethylene content is 7%, the melting point of * * * polymer is as low as 152 F. X3 content has a greater influence on the melting point of * * * polymer than that of children and higher gene content. It also depends on the catalyst itself and its ability to combine ethylene with X3 groups instead of X5 groups.
edit PPR- main properties of this paragraph
Polypropylene pipes are divided into three types: homo-polypropylene (PP-h), block * * * polypropylene (PP-b) and random polypropylene (PP-r). The rigidity of PP-H, PP-B and PP-R pipes decreases in turn, while the impact strength increases in turn. Polypropylene pipe for water supply is made of extraordinary PP-R. As a new type of pipe, PP-R pipe has the following performance characteristics: 2.1 The energy consumption of energy-saving PP-R pipe is only 2% of that of steel pipe, and its thermal conductivity is low [.2 W/(m k)], which is only 1/2 of that of steel pipe. It will greatly reduce the heat loss when it is applied to hot water system. 2.2 Corrosion-resistant, non-scaling, sanitary and non-toxic The use of PP-R pipes can avoid the "secondary pollution" of water quality caused by scaling and rust on the inner wall of galvanized steel pipes. Due to the simple composition of PP-R, the basic components are carbon and hydrogen, which conforms to the food hygiene regulations and is non-toxic, and is more suitable for drinking water transportation. 2.3 Heat resistance, pressure resistance and long service life The long-term service temperature of PP-R tube can reach 95℃, and the short-term service temperature can reach 12℃. Under the conditions of using temperature of 7℃ and working pressure of 1．2MPa, the service life can reach more than 5 years after long-term continuous use. 2.4 light weight, high strength and low fluid resistance, the density of PP-R pipe is only 1/8 of that of metal pipe, the pressure test strength is as high as 5MPa, and it has good toughness and impact resistance. Because the inner wall is smooth, does not rust and scale, the fluid resistance is small. The main technical indexes of PP-R pipe are as follows: density .9g/cm3, elastic modulus (2℃)8MPa, thermal expansion coefficient 1.8× 1-4/k, thermal conductivity .2w/(m.k), longitudinal shrinkage 2%, impact test damage rate ≤ 1%, short-term hydraulic test 1h, ring stress 16MPa, no leakage for long-term 95℃, 1h, and ring stress.
edit PPR- material properties
physical properties: generally speaking, random PP*** polymer has better flexibility and lower rigidity than PP homopolymer. When the temperature drops to 32°F, they can still maintain moderate impact strength, while when the temperature drops to-4 F, their usefulness is limited. The flexural modulus (secant modulus at 1% strain) of * * polymer is in the range of 483～134MPa, while that of homopolymer is in the range of 134 ~ 1379 MPa. The influence of molecular weight of PP * * polymer material on rigidity is not as great as that of PP homopolymer. The impact strength of cantilever beam with notch is generally in the range of .8 ~ 1.4 ft lb/inch. Chemical resistance: random PP*** polymer to acid. Alkali, alcohol, low-boiling hydrocarbon solvents and many organic chemicals have strong resistance. At room temperature, PP*** polymer is basically insoluble in most organic solvents. Moreover, when exposed to soap, soap lye. In water-based reagents and alcohols, they will not be damaged by environmental stress cracking like many other polymers. When in contact with certain chemicals, especially liquid hydrocarbons. Chlorinated organic compounds and strong oxidants can cause surface cracks or swelling. Non-polar compounds are generally more easily absorbed by polypropylene than polar compounds. Barrier performance: PP*** polymer and homopolymer have very low water vapor permeability (.5g/ml/1 square inches/24h). These properties can be improved by orientation. The stretch blow-molded polypropylene bottle has improved the water vapor permeability resistance to .3 and the oxygen permeability to 25. Electrical properties: Generally speaking, polypropylene has good electrical properties, including: high dielectric strength, low dielectric constant and low loss factor; However, homopolymer is generally selected for power applications.
editing the PP－R- production process of this paragraph
The production process of PP-R pipes is extrusion molding process. First, the PP-R raw materials in the hopper enter the extruder by their own weight, are heated and extruded and mixed in the extruder barrel, fully plasticized, and then extruded from the extruder die, and then enter the setting table. The shaped pipes are dragged by a tractor, determined by a fixed length, cut off by a cutting machine, and put into storage after inspection. The corresponding pipe fittings are produced by injection molding. Pipe production process: PP-R raw materials → vacuum suction feeding → hopper storage → feeding → extrusion molding → cooling setting → traction → cutting → inspection → warehousing pipe production process: PP-R raw materials → conveying and feeding → hopper storage → feeding → heating and melting → extrusion injection molding → cooling setting → mold opening → inspection → warehousing 3.3 Production process parameters: (PP-R raw materials → heating and melting → extrusion injection molding → cooling setting → warehousing) ~ 19℃ Zone 3 ~ 4 2 ~ 21℃ Mold temperature 2℃ Drawing speed 2 ~ 2m/min Pipe injection parameters: (1) Barrel temperature distribution 16 ~ 17℃ Barrel rear 2 ~ 23℃ Barrel front 18 ~ 2℃ (2) Nozzle 17 ~ 19℃
edit PPR- product standard in this paragraph
random polypropylene products shall be uniformly implemented. Generally, the enterprise standard is Q/321GPRO 217-26 "Special material for polypropylene resin by batch liquid-phase bulk method", in which hot and cold water pipes are generally implemented: petrochemical industry standard SH/T175-25 "For hot and cold water piping systems".
Edit PPR- Usage Features in this paragraph
Apart from the characteristics of light weight, corrosion resistance, no scaling and long service life of ordinary plastic pipes, PP-R pipes also have the following main characteristics: 1. Non-toxic and sanitary. The raw material molecules of PP-R are only carbon and hydrogen, and there are no harmful and toxic elements. PP-R is sanitary and can be used not only in cold and hot water pipelines, but also in pure drinking water systems. 2, heat preservation and energy saving. The thermal conductivity of PP-R pipe is .21w/mk, which is only 1/2 of that of steel pipe. 3. Good heat resistance. Vicat softening temperature of PP-R tube is 131.5℃. The highest working temperature can reach 95℃, which can meet the requirements of hot water system in building water supply and drainage code. 4. Long service life. The service life of PP-R pipe can reach more than 5 years under the conditions of working temperature 7℃ and working pressure (P.N)1.OMPa. The service life at normal temperature (2℃) can reach more than 1 years. 5, easy to install, the connection can be *. PP-R has good welding performance, pipes and fittings can be connected by hot melting and electric melting, which is convenient to install, and the joint can be *, and the strength of the connection part is greater than that of the pipe itself. 6. Materials can be recycled. After cleaning and crushing, PP-R waste can be recycled for the production of pipes and fittings. The amount of recycled materials does not exceed 1% of the total amount, which does not affect the product quality.
Edit PPR- in this paragraph-Main uses
1. Cold and hot water systems of buildings, including central heating systems; 2. Heating system in the building, including floor, wallboard and radiant heating system; 3. Pure water supply system that can be directly drunk; 4. Central (centralized) air conditioning system; 5, transportation or discharge of chemical media and other industrial pipeline systems.
Edit the selection of PPR- PP-R in this section
1. Pay attention to the determination of the overall utilization factor c (that is, the safety factor) of the pipeline: in general occasions, and the temperature is kept below 7℃ for a long time, c = 1.25 is optional; In important occasions, and the long-term continuous use temperature is ≥7℃, and it is possible to run at higher temperature for a long time, optional C = 1.5; 2. For cold water (≤4℃) system, pipes and fittings with P.N 1. ~ 1.6 MPa are selected; Used in hot water system to select pipes and fittings with ≥PN2.MPa or higher. 3. After considering the above three principles, the SDR of pipe fittings should not be greater than that of pipes, that is, the wall thickness of pipe fittings should not be less than that of pipes of the same specification.