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With China Plastic Machinery
With China Plastic Machinery
UPVC is also called PVCU, usually called hard PVC. It is an amorphous thermoplastic resin made by polymerization of vinyl chloride monomer and certain additives (such as stabilizers, lubricants, fillers, etc.). In addition to using additives, it is also blended with other resins to make it have obvious practical value. These resins include CPVC, PE, ABS, EVA, MBS, etc. UPVC has high melt viscosity and poor fluidity. Even if the injection pressure and melt temperature are increased, the fluidity does not change much. In addition, the molding temperature of the resin is very close to the thermal decomposition temperature, and the temperature range for molding is very narrow. It is a material that is difficult to mold.
UPVC must be modified and granulated before it can be used. PVC is brittle, has poor thermal stability, and is not easy to process. It cannot be used directly, and must be modified and mixed, and relevant additives must be added. The most common modification is modified granulation. Strictly speaking, the PVC modification formula for PVC products with special requirements is tailored to customer requirements. At present, many products of China's PVC modified material formula design have been exported abroad and obtained some independent intellectual property rights; UPVC particles absorb less than 0.02% of water after being at room temperature for 24 hours, so there is no need to dry. If drying is required, it can be placed in a hot air furnace at 60-70¡æ for 3 hours, or a dryer at 80¡æ for 1-1.5 hours.
Recycled materials can be mixed with new materials at a maximum of 20%, and the amount of recycled materials depends on the final use of the product. Abuse of recycled materials can cause injection molding failure, not only because of too much recycled components, but more because the materials have been reprocessed many times. The quality of recycled materials decreases more with each recycling.
UPVC has a high melt viscosity and is easy to decompose. The decomposition products are corrosive to metals. Its injection molding must use special plasticizing components and temperature control systems.
The mold temperature can be set to 40¡æ. The length of the runner should be short and the diameter should be large to reduce pressure loss and the pressure holding can be transmitted to the mold cavity. The shorter the gate is, the better. The die cutting surface should be round. The minimum diameter of the nozzle is 6mm, and it should be conical with an inner angle of 5¡ã.
The die cutting surface of the main channel should also be round and combined with the cold well. The main channel and the gate are connected by the cut surface radius. The diameter can be 7mm.
The gate should be connected to the plastic part with the radius of the cut surface. The shorter the better. The die cutting surface should be smooth.
The cold well can prevent semi-solidified materials from entering the mold cavity. Its importance is often overlooked.
The gate should be positioned correctly so that the material flows smoothly on the runner and will not stay in sharp corners, debris and metal traces to avoid compression or decompression. The runner should be kept smooth and fluent.
The mold should be cast in stainless steel with a chromium content of at least 13%, preferably 16%, and a Rockwell hardness of at least 55. Hard steel molds can be chrome-plated to form a protective effect.
After production, use mild alkali solution to carefully clean the mold surface and then spray it with oil spray or silicone spray.
can be measured by air injection method, ranging from 185-205¡æ. The accurate melt temperature of UPVC can be known from the smoothness of the injected material. If the material is rough and uneven after injection, it proves that the material is not uniform (insufficient plasticization), indicating that the set temperature is too low; if foaming and a lot of smoke emerge after injection, it means that the temperature is too high.
The injection speed should be slow, otherwise excessive shearing will degrade the material. When using UPVC to produce extremely smooth thick-walled products, a multi-stage injection mold filling speed should be used.
Should be determined in conjunction with the molding cycle. The screw surface speed should not exceed 0.15-0.2m/s. The back pressure can reach 150bar, the lower the better, and 5bar is common. The residence time of the barrel should not exceed 5 minutes at a temperature of 200¡æ. When the temperature is 210¡æ, the barrel residence time should not exceed 3 minutes. UPVC products: UPVC ball valve, UPVC butterfly valve, UPVC pipe, etc. UPVC pipe: It is actually a kind of plastic pipe. The interface is generally bonded with glue. The antifreeze and heat resistance of UPVC pipe are not good. Therefore, hot and cold water pipes are rarely used. PVC pipes are suitable for wire pipes and sewage pipes. In recent years, the scientific and technological community has found that the chemical additive phthalate, which can make PVC softer, has a great impact on the kidneys, liver, and testicles in the human body, causing cancer and kidney damage, destroying the human body's functional regeneration system, and affecting development.
a. Strong corrosion resistance: Compared with general cast iron pipes and galvanized pipes, PVC pipes have extremely strong corrosion resistance, can withstand strong acids and strong alkalis, and will not rust or scale. You don't have to worry about the "red water" phenomenon when using it.
b. Low fluid resistance: The inner wall of the PVC pipe is very smooth. Its surface roughness coefficient is only 0.009, the fluid resistance is very small, and the water pressure will not be reduced excessively.
c. High mechanical strength: UPVC pipes for water supply have good water pressure resistance, impact resistance, and tensile strength. They can withstand 110 atmospheres for 1 hour at room temperature without breaking.
d. Sanitary and non-toxic: UPVC pipes for water supply use a unique green and environmentally friendly lead-free formula system instead of the traditional composite lead salt formula system, so they will not damage the water quality or affect human health.
e. Light texture and convenient installation and construction: The density of PVC pipes is one-fifth of that of general cast iron, and it is easy to transport and load. And it is easy and quick to install and construct by using special adhesive or elastic seal.
f. Temperature performance of water supply pipe: The temperature range of UPVC pipe for water supply is best at room temperature. If the temperature is too low, the brittleness will increase, which is not conducive to installation and construction; if the temperature is too high, the tensile strength will decrease and the water pressure resistance will decrease.
g. Good water tightness: 15 minutes after the adhesive is bonded, the bonding strength can reach more than 12.5/C, and there will be no significant decrease after years of use. The sealing ring at the elastic seal joint also has a comparable service life with PVC pipes, and there is no worry about aging and leakage.
The difference between UPVC and PVC
Advantages of UPVC pipe fittings and pipes
Lightweight: The specific gravity of UPVC material is only 1/5 of that of cast iron, which is easy to transport and install, reducing costs.
Excellent chemical resistance: UPVC has excellent acid and alkali resistance, except for strong acids and alkalis close to the saturation point or strong oxydising agents atmaximun.
Non-conductive: UPVC materials cannot conduct electricity, nor are they corroded by electrolysis or electric current, so no secondary processing is required.
Cannot burn, nor support combustion, no fire concerns.
Easy to install, low cost: Cutting and connection are very simple, and the use of PVC glue connection practice has proved to be reliable and safe, easy to operate, and low cost.
Durable: Excellent weather resistance, and cannot be corroded by bacteria and fungi.
Low resistance, high flow rate: The inner wall is smooth, the fluid flow loss is small, and dirt is not easy to adhere to the smooth pipe wall, so maintenance is relatively simple and the maintenance cost is low.
PVC
PVC is polyvinyl chloride, a plastic product synthesized from 43% oil and 57% salt. Compared with other types of plastic products, PVC uses raw materials more effectively and reduces fuel consumption. At the same time, the PVC manufacturing industry consumes very little energy. And in the later stages of the use of PVC products, they can be recycled and converted into other new products or incinerated to obtain energy.
Stabilizers are added to PVC during production, but stabilizers are divided into non-toxic and toxic ones. Only when toxic stabilizers such as lead salts are added will hidden dangers arise. However, PVC products are mixed, and some small companies use lead salts as stabilizers, which makes it difficult to meet relevant health standards. When consumers choose PVC materials, it is best to go to a regular building materials market with a guaranteed reputation and quality, and require the supplier to issue a qualified test report. Consumers should pay attention to checking relevant certificates and signs, and only products that have obtained the "Sanitary License for Products Involving Drinking Water Hygiene and Safety" are safe.
With the development and improvement of additives and formulation technology, the use of UPVC is not only in pipe fittings and pipes for water supply and drainage. The molecular structure and performance of PVC, the diversity of additives, and the increasingly perfect formulation technology make UPVC have excellent performance that other polymer materials cannot compare with, which is mainly manifested in the following aspects:
Adding tin stabilizers during the modification and production of UPVC is not only environmentally friendly and harmless, but also enhances its thermal stability and dimensional stability.
Refers to the ability of plastics to withstand various climates. These include visible light and ultraviolet light, moisture, temperature, atmospheric chlorination, and chemical agents encountered during the use of products. The most important weather resistance includes non-fading, powder resistance, and durability of physical properties. The weather resistance of modified UPVC is comparable to that of ASA, and has better physical and chemical properties. As we all know, among all polymer materials, ASA is famous for its excellent weather resistance. UPVC can completely replace ASA in terms of weather resistance. In China, after years of research and development, Hanyong Plastic New Materials has successfully developed UPVC materials with a QUV test of more than 2,500 hours (i.e., weather resistance of more than 10 years), and obtained the invention patent of the material (patent number: 200710133473.9.), filling the gap.
UPVC itself has good flame retardant performance. The oxygen index of general UPVC is above 27. After special modification, the oxygen index of UPVC can reach or even exceed 42, which is unmatched by other general plastics.
UPVC will show different performances by adding additives with different performances to UPVC. This makes UPVC diverse. It makes its use more extensive. It makes it one of the largest plastic products in the world.
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