What is PVC sheet?
PVC sheet is a kind of vacuum blister sheet, also known as decorative sheet or attached adhesive sheet, and has been applied to surface packaging in the industries of building materials, packaging, and medical care.
According to the degree of softness and hardness, PVC sheets can be divided into soft PVC film and PVC rigid sheets. Soft PVC film is mainly used on floors, ceilings, and leather surfaces. However, soft PVC film contains softeners, which is also the difference between soft PVC film and PVC rigid sheet, so it is easy to become brittle and difficult to preserve, thus limiting its range of use. On the contrary, PVC rigid sheet contains no softeners, so it is easy to form, non-toxic and pollution-free, will not brittle, and has a long preservation time, which increases its development and application value.
What are the advantages of PVC rigid sheet?
With the development of environmental protection concepts, people attach more and more importance to the recycling and utilization of PVC rigid sheets. Consequently, PVC rigid sheet has been widely used in the sectors of petroleum, chemical, construction, medical, automotive, and electronic communications, etc., for its outstanding strengths including excellent corrosion resistance, strong hardness, high strength, anti-UV, water absorption without deformation, and easy processing. For example, the air duct made of China transparent PVC rigid sheet requires no flange connection or silencer, has the features of fire prevention and moisture-proof, and its thermal insulation properties also meet the requirements of use. In the United States, rigid PVC materials begin to replace PC materials used in transparent medical parts, such as Y connector, bush, filter, instillator, and sample container, because the strength and transparency of rigid PVC can be comparable to PC. However, stress cracks often occur when PC meets ducts and other parts, and rigid PVC can reduce or eliminate stress cracks.
Features of PVC rigid sheet
PVC rigid sheet, a superior thermoforming material, can replace some stainless steel and other corrosion-resistant materials. PVC possesses high hardness, which increases as the increase of molecular weight, or decreases as the temperature rises. PVC rigid sheet has strong mechanical properties, with elastic modulus reaching up to 1500-3000 MPa, but the elasticity of soft PVC is only 1.5-15 MPa. However, the rupture elongation of China’s transparent PVC rigid sheet can be up to 200%-450%. PVC has ordinary friction properties, with a static friction factor of 0.4-0.5, and a dynamic friction factor of 0.23. Due to its poor heat resistance stability, PVC begins to decompose at 140 ℃ and melt at 160 ℃. PVC has a low linear expansion coefficient, is incombustible, and its oxidation index can reach over 45. PVC is a polymer with good electrical properties, but due to its higher polar nature, the electrical insulating property is inferior to PP and PE. It has a large dielectric constant, dielectric loss angle tangent, and volume resistivity, but low corona resistance, so PVC is generally suitable for low-voltage and low-frequency materials. China PVC rigid sheet can be resistant to most inorganic acids, alkalis, salts, and organic solvents. PVC is resistant to most inorganic acids, alkalis, salts, and organic solvents.
Due to its excellent corrosion resistance and certain mechanical strength, PVC rigid sheet, after secondary processing, can be transferred into the sulfuric acid (hydrochloric acid) tank, empty medicine needle rack, chemical process rack, public bathroom water tank; processed product template, decorative plate, exhaust duct, and equipment lining as well as other special-shaped products and containers. It can be clearly found from the feedback of customers of China PVC rigid sheet manufacturers that PVC has become the ideal material for chemical, building materials, decoration, and other industries.
Key points in the processing process of PVC rigid sheet
PVC rigid sheet adopts the processing process of batching and mixing. The quality of PVC mixture preparation directly affects the extrusion speed, process parameters, and product quality, so this process should be strictly controlled. The main equipment for the preparation of PVC mixture includes a mixer, screw feeder, and hopper. The mixer is a horizontal type, double-cone mixer; the screw feeder is a metering feeder; the hopper is a storage tank.
1. For batching process, materials of formula components should be accurately measured to prevent large measurement errors, which may lead to changes in the actual formula and increase the difficulty of quality analysis and quality control. China PVC rigid sheet manufacturers often ignore this key point in the actual production process and should pay sufficient attention to it.
2. PVC rigid sheet should be cut into appropriate sizes according to the actual needs of users. The inappropriate size will also result in measurement errors and quality problems in the production process.
3. PVC rigid sheet has many components, so it’s critical to choose a reasonable feeding order, which should benefit the additives to function, prevent any confrontation effects between additives, and improve the speed of dispersion.
4. The welding process of China PVC rigid sheet is also very important. Inappropriate welding will easily lead to quality problems in the products. There are a lot of welding techniques, and the most commonly used are gas shielded arc welding and submerged arc welding.
Typical mixing process of PVC rigid sheet
1. Stir PVC resin in the high-speed mixer first and increase the temperature to 60 ℃.
2. Add the stabilizer, and continue to raise the temperature to 90 ℃.
3. Add internal lubricants, processing additives, impact modifiers, fillers, coloring agents, etc.
4. Input external lubricants, and continue to raise the temperature to 115-120 ℃.
5. Discharge materials into the rotating cold mixer with coolant at a low speed.