Polyvinyl chloride – PVC

Polyvinyl chloride, or PVC for short, is a polymer formed by the vinyl chloride monomer (VCM) in the trigger of peroxides, azo compounds, etc., and by the mechanism of free radical polymerization reaction under the action of light and heat. Vinyl chloride homopolymers and vinyl chloride copolymers are collectively referred to as vinyl chloride resins

PVC is white powder without shape, the degree of branching is small, glass temperature 77 to 90 degrees C, 170 degrees C or so began to decompose, the stability under light and heat is poor, above 100 degrees C or after a long period of exposure to sunlight, will be decomposed to produce hydrogen chloride, and further automatic catalytic decomposition, causing discoloration, physical mechanical properties are also rapidly reduced, in practical applications, stabilizer must be added to improve the stability of heat and light.

The PVC molecular weight of industrial production is generally in the range of 50,000 to 110,000, with a large multi-dispersion, molecular weight increases with the decrease of polymerization temperature, no fixed melting point, 80 to 85 degrees C began to soften, 130 degrees C become a sticky bullet state, 160 to 180 degrees C began to change into a viscous flow state, has better mechanical properties, tensile strength of about 60MPa, impact strength of 5 to 10kJ/m²; it has excellent dielectric performance.

PVC was once the world’s most produced general plastics, widely used in building materials, industrial products, daily necessities, floor leather, floor tiles, artificial leather, pipe, wire and cable, packaging film, bottles, foaming materials, sealing materials, fibers and other aspects are widely used.

History

PVC was discovered as early as 1835 by V. Renio in the United States, when he exposed vinyl chloride to sunlight to produce a white solid, PVC.

PVC was discovered twice in the 19^th century, once by Henry Victor Regnault in 1835 and once by Eugen Baumann in 1872. In both cases, the polymer in beakers made of vinyl chloride placed turned into white solid in the sun’s rays. At the beginning of the 20^th century, Russian chemist Ivan Ostromislensky and German company Griesheim-Elektron’s chemist Fritz Klatte both tried to use PVC for commercial purposes, but it was difficult to process the hard, sometimes brittle polymer.

In 1912, the German Fritz Klatte synthesized PVC and filed a patent in Germany, but was unable to develop a suitable product before the patent expired.

In 1926, the United States B.F. Goodrich’s Waldo Semon synthesized PVC and filed a patent in the United States. Waldo Semon and B.F. Goodrich Company developed the method of plasticizing PVC with a variety of additives in 1926, making it a more flexible and easy-to-process material and quickly gaining wide commercial use.

PVC plastic products are widely used, but in the mid-1970s, it was recognized that PVC resins and products residual monomer vinyl chloride (VCM) is a serious carcinogen, no doubt to a certain extent will affect the development of PVC. However, people have successfully reduced the residual VCM through automobiles and other means, so that PVC resin VCM content will be less than 10 ppm, meeting the requirements of sanitary resin, expanding the application of PVC. It can even reduce the VCM content in the resin to less than 5ppm, and there is very little VCM left after processing. Basically harmless to the human body, can be used in food packaging and children’s toys.

Main Categories

According to the application, PVC can be divided into: ordinary PVC resin, polymer PVC resin and cross-linked PVC resin. General PVC resin is polymerized by vinyl chloride monomer under trigger conditions. The highly polymerized PVC resin refers to a resin polymerized by adding a chain extender to the polymerization system of vinyl chloride monomer. The cross-linked PVC resin is a resin made from a cross-linking agent containing biphenyl and polyene in a vinyl chloride monomer polymerization system.

According to the method of obtaining vinyl chloride monomer, it can be divided into calcium carbide method, ethylene method and imported (EDC, VCM) monomer method (ethylene method and imported monomer method are usually collectively referred to as ethylene method).

According to the polymerization method, polyvinyl chloride can be divided into four categories: suspension polyvinyl chloride, emulsion polyvinyl chloride, bulk polyvinyl chloride and solution polyvinyl chloride. Suspended PVC is the one with the highest output, accounting for about 80% of the total output of PVC. Suspended PVC is divided into six models according to absolute viscosity: XS-1, XS-2…XS-6; XS-1, XS-2…XS-6; XS-1, XS-2…XS -6. XJ-1, XJ-2…, XJ-6. The meaning of the letters in the model: X suspension method; S type bulk type; J tight-fitting type.

According to the amount of plasticizer content, PVC plastic is divided into: no plasticizer PVC, plasticizer content is 0; hard PVC, plasticizer content of less than 10%, semi-hard PVC, plasticizer content of 10-30%, soft PVC, plasticizer content of 30-70%, PVC paste plastic, plasticizer content of more than 80%.

Produce method:

PVC can be made from ethylene, chlorine and catalysts. Because of its fire and heat resistance, PVC is widely used in a wide variety of products: wire skin, fiber optic skin, shoes, handbags, bags, ornaments, signboards and billboards, architectural decoration supplies, furniture, pendants, rollers, pipes, toys, curtains, shutters, auxiliary medical supplies, gloves, some food preservation paper, some fashion.

Polymerization:

PVC is prepared by free radical plus polymerization, which is mainly divided into suspended polymerization method, emulsion polymerization method and ontological polymerization method, mainly suspended polymerization method, accounting for about 80% of the total PVC output. Pure water, liquefied VCM monomer, dispersant added to the reactor, and then added triggers and other additives, heating up to a certain temperature after the VCM monomer free radical polymerization reaction to produce PVC particles. Continuous stirring causes the particles to have uniform granularity and suspends the resulting particles in water. In addition, there is the use of micro-suspension method to produce PVC paste resin, product performance and paste are good.

① Suspended polymerization method: the monomer is micro-drop-like suspension scattered in the water phase, the oil-soluble trigger used is soluble in the monomer, polymerization reaction in these microdrops, polymerization reaction heat is absorbed by water in time.In order to ensure that these micro-drops in the water is beaded dispersion,we need to add suspension stabilizers, such as gelatin, polyethylene alcohol, methyl cellulose, hydroxyl cellulose. The triggers are mostly organic peroxides and azo compounds, such as diispropanate peroxide, dicyclic hexester peroxide, diethylene dioxide and azo diisoster, diazepam. The polymerization takes place in an aggregator with a blender. After aggregation, the material flows into the unit recycling tank or the gas tower to collect the unit.

Then it flows into the mixing kettle, after washing and then centrifugal dehydration, drying, here is the resin product. The vinyl chloride monomer should be removed from the resin as many as possible. PVC for food packaging, free monomer content should be controlled below 1 ppm. In order to ensure the resin of the specified molecular weight and molecular weight distribution range and prevent explosion, the temperature and pressure of the polymerization process must be controlled. The particle size and particle size distribution of the resin are controlled by the mixing speed and the selection and dosage of the suspension stabilizer. The quality of the resin is characterized by particle size and particle size distribution, molecular weight and molecular weight distribution, apparent density, porosity, fisheye, thermal stability, color, impurities content and powder free flow. Polymer reactor is the main equipment, made of stainless steel or enamel lined with steel kettle body, equipped with agitator and temperature control heat transfer jacket, or internal cold drain pipe, reflux condenser and so on. In order to reduce production costs, the volume of the reactor has been gradually developed from a few cubic meters, more than a dozen cubic meters to large-scale development, the maximum has reached 200 cubic meters (kettle reactor). The polymer kettle is descaled after multiple use. PVC made of polyethylene alcohol and cellulose ether as suspension stabilizer is generally loose, has many pores, has a large surface area, and is easy to absorb plasticizers and plasticize.

② Emulsion polymerization method: one of the earliest methods of industrial production of PVC. In emulsion polymerization, in addition to water and vinyl chloride monomer, we also add sodium alkyl sulfate and other surfactants as emulsifiers, so that monomers scattered in the water phase into a emulsion-like, water-soluble potassium persulphate or ammonium persulphate as the trigger, can also be used “oxidation-reduction” trigger system, polymerization process and suspension method is different. There are also added polyethylene alcohol as emulsified stabilizer, xyl sulfurol as a regulator, sodium bicarbonate as a buffer. The aggregation method has three kinds of intermittent method, semi-continuous method and continuous method. The polymer product is latex-like, emulsion particle size 0.05 to 2 m, can be directly applied or dried by spray into powdered resin. The polymerization cycle of emulsion polymerization method is short, easy to control, the resin molecular weight is high, the polymerization degree is more uniform, suitable for PVC paste, artificial tanning or impregnated products. The formula of emulsion polymerization is complex and the impurities content of the product is high.

③ Ontal polymerization method: The polymerization device is special and consists mainly of vertical pre-polymerizer and horizontal polymerizer with box mixer. The aggregation is done in two segments. Monomers and triggers first pre-polymerize 1h in the pre-polymerization kettle, generate seed particles, then the conversion rate of 8% to 10%, and then into the second segment of the polymerization kettle, supplement with the same amount of pre-polymer monomer, continue to polymerize. To be converted rate of 85% to 90%, discharge the residual monomer, and then crushed, sieved to get the finished product. The particle size and particle shape of the resin are controlled by the stirring speed, and the reaction heat is brought out by the monomer reflux condensation. This method of production process is simple, product quality is good, production costs are also low.

PVC physical and chemical properties

The color is light yellow, translucent and shiny. PVC transparency is very good, its transparency is better than polyethylene, polypropylene, worse than polystyrene, with different additives, divided into soft and hard PVC, soft products have strong flexibility and feel, hard products are better than low-density poly The hardness of ethylene is higher, and polyethylene is lower than that of low-density polyethylene, and it becomes white folds after processing. Stable, not easy to be corroded by acid and alkali, and more heat-resistant.

PVC has the advantages of high chemical resistance (resistant to strong hydrochloric acid, 90% sulfuric acid, 60% nitric acid and 20% sodium hydroxide), flame retardant (flame retardant value greater than 40), mechanical strength and good electrical insulation.

PVC has poor stability to light and heat. The softening point is 80 degrees C and the decomposition begins at 130 degrees C. In the absence of heating stabilizers, PVC begins to break down at 100 degrees C, and decomposition is faster above 130 degrees C. Heat breaks down the release of hydrogen chloride gas (hydrogen chloride gas is toxic gas) to discolor it, from white → light yellow→ red→ brown → black. Ultraviolet light and oxygen in sunlight cause PVC to be photooxidized and decomposed, reducing PVC’s flexibility and finally brittleness. This is why some PVC plastics become yellow and brittle over time.

It has stable physical and chemical properties, is insoluble in water, alcohol, gasoline, gas, water vapor leakage is low, can withstand any concentration of hydrochloric acid at room temperature, less than 90% sulfuric acid, 50-60% nitric acid and caustic soda solution under 20% concentration, has a certain degree of resistance to chemical corrosion; It is fairly stable for salts, but can be dissolved in organic solvents such as ethers, ketones, chlorinated fatty hydrocarbons and aromatic hydrocarbons.

Industrial PVC resin is mainly amorphous structure, but also contains some crystalline areas (about 5%), so PVC has no obvious melting point, about 80 degrees C began to soften, thermal deformation temperature (1.82 MPa) is 70-71 degrees C, under pressure 150 degrees C began to flow, and began to slowly release hydrogen chloride, resulting in PVC discoloration (red by yellow, brown, or even black).

Industrial PVC weight relative molecular mass is in the range of 4.8-48,000, the corresponding number of relative molecular mass is 2-195 million. The weight relative molecular mass of most industrial resins is 10-20 million, and the relative molecular mass is 4.55-64,000. Hard PVC (without plasticizer) has good mechanical strength, weather resistance and fire resistance, can be used alone as structural materials, used in chemical manufacturing pipes, sheets and injection molding products. Hard PVC can be used as an enhanced material.

The properties of the material

Density：1380 kg/m³

Yang’s elastic modulus（E）：2900-3400 MPa

Stretch strength（σt） ：50-80 MPa

Break elongation： 20-40%

Glass temperature：87℃

Melting point：212℃

Softening temperature： 85℃

Heat conductivity（λ）： 0.16 W/(m·K)

Coefficient of thermal expansion（α）：8×10^-5 /K

Heat capacity（c）：0.9 kJ/(kg·K)

Water absorption rate（ASTM）： 0.04-0.4

Refractive index：1.52~1.55

PVC is characterized by flame retardant flame retardants and is therefore widely used in fire protection applications. But PVC releases hydrogen chloride and other toxic gases, such as dioxins, during combustion.

The combustion of PVC is divided into two steps. Hydrogen chloride gas and diolefins containing double bonds are first broken down at 240 ℃-340 ℃, and then carbon combustion occurs at 400 ℃-470 ℃.

It is one of the world’s most produced plastic products, cheap, widely used, PVC resin for white or light yellow powder. PVC plastics can exhibit different physical and mechanic properties depending on their use. The right amount of plasticizer is added to PVC resin to make a variety of hard, soft and transparent products.

Pure PVC has a density of 1.4g/cm3, and PVC with plasticizers and fillers is generally 1.15-2.00g/cm3

Hard PVC has better anti-pull, anti-bending, anti-pressure and impact resistance, can be used as a structural material alone.

Soft PVC has better softness, fracture elongation and cold resistance, but brittleness, hardness and tensile strength will be reduced.

PVC has good electrical insulation performance, can be used as low-frequency insulation material, its chemical stability is also good. Because of the poor thermal stability of PVC, long-term heating will lead to decomposition, release HCL gas, so that PVC discoloration, so its application range is narrow, the use temperature is generally between -15 to 55 degrees C.

The corresponding hardness of PVC, in Pa and Shore:

Pa	Shore
45	89±2，87~91A
50	86±2，84~88A
55	83±2，81~85A
60	80±2，78~82A
65	78±2，76~80A
70	75±2，73~77A
75	72±2，70~74A
80	69±2，67~71A

PVC Hardness Comparison
Palmer’s Hardness	厚度	Tested Shore’s Hardness	Average haedness
30P	6mm	93-96 °	94.5 °
35P	6mm	87-93 °	90 °
38P	6mm	89-90 °	89.5 °
40P	6mm	88-90 °	89 °
45P	6mm	84-90 °	85 °
50P	6mm	82-83 °	82.5 °
55P	6mm	70-80 °	79 °
60P	6mm	74-76 °	75 °
65P	6mm	73-75 °	74 °
70P	6mm	72-74 °	73 °
75P	6mm	70-70.5 °	70 °
80P	6mm	67-68 °	67.5 °
85P	6mm	64-66 °	65 °
90P	6mm	63-64 °	63.5 °
95P	6mm	58-60 °	59 °
100P	6mm	57-59 °	58 °
110P	6mm	54-56 °	55 °

Hardness Comparison
Pa	Shore’s Hardness
30	95±2
45	90±2
50	88±2
60	84±2
70	80±2
80	76±2
90	72±2
95	68±2
105	64±2
Note: The Shore hardness value is recorded every 15 seconds

Forming conditions

Hard PVC

Pipe temperature：160-190℃

Mold temperature：40-60℃

Dry temperature：80℃×2h

The spray pressure：700-1500kg/cm²

Density：1.4g/cm³

Shrinkage：0.1-0.5%

Thickness：2.0-50.mm

Water absorption rate（24h）：0.1-0.4%

Melt softening point：89℃

Thermal deformation temperature：70℃

Soft PVC

Pipe temperature：140-170℃

Mold temperature：40-60℃

Dry temperature：80℃×2h

The spray pressure：600-1500 kg/cm²

Density：1.4 g/cm³

Shrinkage：0.1-0.5%

Thickness：2.0-50.mm

Water absorption rate（24h）：0.1-0.4%

Melt softening point：85℃

Thermal deformation temperature：55℃

Material processing

PVC plastics come in different forms and are very different, and the processing methods are also varied, which can be pressed, extruded, injected, coated, etc. PVC resin particle size, fisheye, pine density, purity, foreign impurities, porosity have an impact on processing, paste resin should consider the viscosity and gel properties of paste.

PVC is amorphous high polymer with a small shrinkage. Powder processing should be preheated to remove moisture, enhance the plasticization effect to prevent bubbles. And PVC is very easy to break down, especially at high temperatures with steel, copper contact is easier to decompose (decomposition temperature 200 degrees C). The molding temperature range is small and the temperature must be strictly controlled. When using screw injectors and straight-through nozzles, the aperture should be large to prevent dead-end hysteresis. Mold pouring system should be large, gate cross-section should be large, mold should be cooled, mold temperature 30-60 degrees C, material temperature 160-190 degrees C.

PVC is glass at glass temperature (Tg, 80 degrees C), high elastic rubber at Tg  (Tf, approx. 160 degrees C) is highly elastic rubber and malleable, and thermal decomposition temperature (Td) at Tf is a viscous state, the higher the temperature is, the easier it flows. When the temperature exceeds Td, the PVC breaks down a large amount of hydrogen chloride (HCl) and the material loses its chemical stability and physical properties, so Td is the upper limit temperature for machining. Because polyethylene molecules act strongly, Tf is high, or even close to the decomposition temperature, plasticizers need to be added to reduce Tf. On the other hand, a stabilizer needs to be added to improve the Td of PVC in order to be processed and molded.

Glassed temperature (Tg) is only related to the structure of the molecular chain segment, and has little to do with molecular weight, while the viscous flow temperature (Tf) is the temperature at which the large molecule begins to move, which is related to the size of the molecular weight, the larger the molecular weight, the higher the Tf. Therefore, for some process molding (e.g. injection molding), it is necessary to reduce the molecular weight of the resin appropriately. Depending on the size of the molecular weight, domestic suspended PVC resin is divided into 1-7 grades, the larger the serial number, the smaller the molecular weight. XJ-4 (XS-4) to XJ-7 (XS-7) resin is often used in the manufacture of tubes, hard plates, etc. , other models are lower, the molecular weight of the larger resin, because Tf is higher, need to add a large number of plasticizers to reduce Tf, so often used in the manufacture of soft products.

PVC with an average polymerization of less than 1000 is called low polymerization PVC, which has good processing performance and can be added less plasticizer during processing, so that the product will not age at an accelerated rate due to the migration of plasticizer. Low polymerization PVC products have good transparency and are widely used in building materials, food and pharmaceutical packaging materials, as well as in the replacement of plexiglass products.

PVC melt is a non-Newtonian pseudofluor, the greater the shear speed is, the smaller the apparent viscosity is, and the change is quite sensitive. Raise the temperature, viscosity is not much, even if the plastic is below the decomposition temperature, but because of a long time at a higher temperature, will also heat and oxidation degradation phenomenon, and affect its performance. Therefore, improving the fluidity of PVC melt should mainly consider increasing the shear rate (increasing pressure). In fact, increasing the external force helps the movement of the polymer, which reduces Tf and allows the large molecule to flow at a lower temperature.

Main use:

1. Profile material

Profiles and profiles the largest sector among many PVC products, accounting for about 25% of the total PVC consumption, mainly used in the production of doors and windows and energy-saving materials, its application volume in the country still has a relatively large increase. In developed countries, plastic doors and windows also have the highest market share, such as Germany 50%, France 56%, the United States 45%.

2. PVC pipe

PVC pipelines are the second largest sector among many PVC products, accounting for about 20% of PVC total consumption. PVC pipe than PE tube and PP tube were development early, they have many varieties, excellent performance, a wide range of use, are important in the market..

3. PC film

PVC film is the third largest seller in the PVC market, accounting for about 10%. After the PVC is mixed with additives and plasticized, a three-roll or four-roll rolling mechanism is used to form a transparent or colored film with a specified thickness, and the method is processed into a roll film. It can also be cut, heat-treated bags, gloves, raincoats, yoga balls, tablecloths, jump ropes, curtains, ab wheels, inflatable toys, etc. The wide transparent film can be used in greenhouses, plastic sheds and films. A biaxially oriented film with heat shrinkability can be used for shrink packaging.

4. PVC hard material and plate

PVC, if added stabilizers, lubricants and fillers, after mixing, the extruder can be extruded from a variety of caliber tubes, special tubes, bellows, used as sewers, drinking water pipes, wire casings or stair handrails. The pressed sheets are recompressed and hot-pressed to make hard sheets of various thicknesses. Plates can be cut into the desired shape and then welded with hot air using PVC welding rods into a variety of chemically resistant tanks, ducts and containers.

5. PVC general soft products

The extruder can squeeze PVC into hoses, wires, cables, etc. Injection molding machines with various molds can make PVC into plastic sandals, fitness equipment, custom yoga mat accessories, shoe soles, slippers, mobile phone cases, toys, auto parts, etc.

6. PVC packaging materials

PVC products are used for packaging, mainly for various containers, films and rigid sheets. PVC film can be used to extrude laminates with other polymers at a lower production cost, as well as transparent products with good barrier properties. PVC film can also be used for stretch or heat shrink packaging, mattresses, fabrics, toys and industrial products.

7. PVC wall panels and floors

PVC wall panels are mainly used to replace aluminum wall panels. PVC floor tiles, with the exception of some PVC resins, are recycled materials, adhesives, fillers and other components, mainly used on the ground floor of the airport terminal and other places of hard ground.

8. PVC consumer goods

Bags are traditional products made from processed PVC, which is used to make a variety of imitation leathers for luggage, sports products such as basketball, football and football. It can also be used to make belts for uniforms and special protective equipment. PVC fabrics for clothing are generally adsorption fabrics (no coating required), such as ponchos, baby pants, faux leather jackets and various rain boots. PVC is used in many sports entertainment products, such as toys, records and sporting goods, and PVC toys and sporting goods have grown significantly, owing to their low production costs and easy molding.

9. PVC coated products

The artificial leather with the base material is coated on cloth or paper, and then plasticized at a temperature above 100 degrees Celsius. It is also possible to press PVC and additives into a film, and then press it into a substrate. The leather without the substrate is directly stretched into a flexible sheet with a certain thickness through a roller press, and then the pattern is pressed. Artificial leather can be used to make boxing gloves, suitcases, belts, wallets, book covers, slippers, sofas and car cushions, and can also be used as floor materials for construction.

10. PVC foam products

When mixing soft PVC and adding the right amount of foaming agent to make a sheet, foam molded into foam, can be used as foam slippers, sandals, insoles, and shock-proof buffer packaging materials. It can also be used to form low foam hard PVC plate and special profile, which can be used as an alternative to wood, and is a new type of building material.

11. PVC transparent sheet

If PVC is added to the shock absorber and organotin stabilizer, mixed, plasticized and pressed, it can become a transparent sheet. Thermoforming can be made into transparent thin-walled containers, and can also be used for vacuum blister packaging. It is an excellent packaging material and decoration material.

12. Other use

Doors and windows are made of hard, special materials. In some countries, we have jointly occupied the market of doors and windows with wooden doors and windows, such as aluminum windows;

Virtual circuit is one of the services provided by packet switching network (the other is data reporting service), in short, through the control mechanism within the network, establish a virtual logical connection between the user host, and ensure the correctness and order of transmitting the packet on it, before and after the communication to carry out the establishment and dismantling of virtual circuit. A permanent virtual circuit is a virtual circuit established when the network is initialized, and the virtual circuit remains. Both the X.25 network and B-ISDN offer PVC services. PVC plastic bags are generally disabled.

Speck, the leading fitness product manufacturer, purchases a large amount of high-quality PVC every year to manufacture jump ropes and other products.

New Materials Research

Plastics have been used in the automotive industry for more than 50 years. With the development of automobile to lightweight and energy-saving direction, higher requirements are put forward for materials. Since 1kg plastic can replace heavier materials such as 2-3kg steel, fuel consumption can be reduced by 6%-8% for every 10% drop in car self-weight. Therefore, increasing the amount of modified plastics in the car can reduce the cost, weight, and achieve energy-saving effect. Different plastic dosages vary from passenger and commercial vehicle to commercial vehicle. Last year, the demand for modified PPs, PC alloys and modified ABS was about 114.63, 15.13 and 149.7 million tons, respectively.

1.PVC replaces steel

Through the research of PVC modification technology, the advanced internal plasticization technology and additive formulation abroad are used to ensure the mechanical and electrical properties of PVC plastic steel, improve flame retardant performance, so that the product has the advantages of high strength, corrosion resistance, flame resistance, good insulation performance and light quality and convenient construction. Steel pipes can be completely replaced in electrical wiring systems.

2. PVC replaces timber

PVC wood plastic composite material is a new type of composite material prepared by heat pressing preparation process with waste wood fiber and plastic main raw materials, supplemented by appropriate processing aids. Its products fully reflect the concept of recycling of renewable resources and petroleum products, which is of great significance for alleviating the current shortage of timber and petroleum resources and serious environmental pollution. [8]  Industry experts pointed out that the PVC building materials to plastic wood, which not only save costs, but also recyclable, in line with the environmental sustainable development and circular economy trend.

14. Synthetic materials

PVC, or PVC for short, is a thermoplastic resin. PVC futures are also futures varieties with PVC as the target. Plastics: polyethylene; PVC; polystyrene; polyethylene alcohol; polypropylene; polyacrylic; polybutene; polysobutene; polyurethane; polyformaldehyde; polyamide; polycarbonate; polylactic acid; polytetrafluoroethylene; polyphenyl ethylphenate; epoxy resin; phenolic resin; polyurethane Synthetic rubber: shunbutyl rubber; butyl rubber; butyl rubber; neoprene Synthetic fibers: acrylic; polyester; nylon; acrylic; spandex; vinyl; nylon; daklun; kovlon

Identification method

The general identification methods of PVC are generally summarized into three categories :

(1) Burn:

Soften or melt the temperature range：75~90°C；

Burning condition: self-extinguishing after ignition；

Burning flame state: smoke in the upper yellow and green; off the fire extinguished; Irritating acidity

This method is the easiest and most straightforward and is generally preferred

(2) Solvent treatment：

Solvents: tethionolfuran, cyclohexone, methadone, dimethylmethamide; Non-solvent: methanol, acetone, etan. By adding the suspected PVC plastic to the above solvent, observe the dissolution of the plastic to determine whether it is PVC. When the solvent is heated, the dissolving effect is more obvious.

(3) Propotion：

The proportion of PVC is 1.35 to 1.45, which is generally about 1.38. PVC and other plastics can be distinguished by specificity differences or by measuring specific gravity. However, because PVC can be added plasticizers, modifiers and fillers, so that PVC becomes a large proportion of differences, hard and soft differences, but also due to the addition of some components, so that many of the performance of PVC plastic changes, resulting in our commonly used identification method effect is not obvious, or even change the phenomenon, can not make an accurate judgment. For example, in terms of density, PVC (about 40% plasticizer) is 1.19 to 1.35, while PVC hard products are increased to 1.38 to 1.50. In the case of high-fill PVC products, the density sometimes exceeds 2.

In addition, it can also be determined by determining whether chlorine is found in the material, but because vinyl chloride copolymers, neoprene, PVC, PVC, etc. all contain a higher proportion of chlorine, but also through the color rendering reaction to identify. Note that before the test, the reagent must be extracted by ether to remove the plasticizer, test method: the sample taken by ether benzene dissolved in tetrahydrofuran, filter out the insoluble ingredients, add methanol to make it precipitate, after extraction before 75 degrees of drying. A small sample that has been dried does not need 1mL of radon to react with it, after a few minutes, add 2 to the field drop 5% sodium hydroxide methanol solution (1g sodium hydroxide dissolved into 20mL methanol), immediately observe the color, 5min and 1h and then observe again. Different chlorine-containing plastics can be identified by color.

In daily life, there is a need to distinguish between PVC and PE plastic film (bag), simple method:

• Touch

With a sense of lubrication felt by hand, the surface is coated with a layer of wax (chemically called wax), which is a non-toxic polyethylene film bag, while PVC film feels a bit sticky.

• Jitter method Shake by hand

The sound is crisp, the texture easily floats is polyethylene film bag. The low-sounding hand shaker is the PVC film bag.

(3) Burning method In case of flammable fire, the flame is yellow, when burning paraffin-like oil drops, and candles when burning gas, is non-toxic polyethylene film bag. If not easy to burn, the fire is extinguished, the flame is green, PVC film bag

（4）Immersion

The plastic bag is immersed in water, pressed into the water by hand, can surface for polyethylene, sink into the bottom of the water is PVC (polyethylene density is less than water, PVC density is greater than water; at room temperature is about 0.92g/cm3 and 1.4g/cm3, respectively). Copper wire can also be taken, burned red in the fire, and then, the copper wire and the test plastic film contact, resulting in chemical changes, and then the copper wire with the plastic composition back into the flame. At this time, it is necessary to carefully observe, if there is a colorful, dazzling green flame, it is indicated that this plastic material contains chlorine, belongs to the PVC material.

Major hazards

PVC is also a commonly used plastic, it is a PVC resin, plasticizers and anti-aging agent resin, itself non-toxic. However, the addition of plasticizers, anti-aging agents and other major accessories toxic, daily PVC plastic plasticizer, mainly the use of benzodiazepines, phthalates, etc. , these chemicals are toxic, PVC anti-aging agent lead stearate is also toxic. Lead is precipitated in PVC products and in contact with ethanol, ether and other solvents. Lead-salted PVC is used as food packaging and oil bars, fried cakes, fried fish, cooked meat products, cake snacks meet, will make lead molecules spread to grease, so can not use PVC plastic bags to pack food, especially can not contain oily food. In addition, PVC plastic products at higher temperatures, such as around 50 degrees C will slowly break down hydrogen chloride gas, this gas is harmful to human health, so PVC products should not be used as food packaging.

Because most disposable medical device products use medical grade PVC or polycarbonate (PC), and PVC processing process of thermal decomposition of steel has a strong corrosive, PC is high hardness, viscosity, so the plastic parts material requirements must be anti-corrosion, anti-wear and high polishing performance. Most medical injection molding machines use the hard chrome-plated method of the barrel screw or the use of stainless steel as the material to make the machine simple screw to meet the above special requirements. In addition, in order to prevent the thermal decomposition of the PVC processing process to produce gas, the dynamic template surface is required to be aluminum-plated treatment, and the peripheral plate gold is also aluminum-plated treatment or the use of stainless steel plate plate gold, plate gold seam using non-toxic silicone seal, in order to prevent the plastic processing process generated by the gas to run outside (plastic processing process generated by the gas can be collected centrally through special equipment and then purified before discharge into the atmosphere).

PVC is the main source of dioxins. Dioxin (TCDD), the deadliest substance in the family of Dioxane, is a well-known carcinogen and hormone breaker and a toxic compound that is harmful to humans and animals. Dioxins are produced when PVC is produced, recycled and destroyed in incinerators, or when PVC products are accidentally burned, such as landfills.