Polypropylene overview
Polypropylene (PP) is obtained by catalytic polymerization of propylene using a Ziegler-Natta catalyst, which is a crystalline isotactic polymer in which molecular chain links are well aligned. The polymerization process production methods include: a solvent polymerization method (slurry method), a liquid phase bulk polymerization method, a gas bulk polymerization method, and a solution polymerization method. However, the main method is the solvent method (slurry method), and the isotacticity is above 95%, and the molecular weight is about 8 to 150,000.
1. performance
(1) Physical properties Polypropylene is a non-toxic, odorless, odorless, milky white, highly crystalline polymer with a density of only 0.90 to 0.91 g/cc. It is one of the lightest brands of all plastics. It is particularly stable to water, with a water absorption rate of only 0.01% in water and a molecular weight of about 8 to 150,000. Good formability, but due to the large shrinkage rate (1% to 2.5%), thick-walled products are easy to sag, and it is difficult to meet the requirements for some parts with high dimensional accuracy. The surface of the product is glossy and easy to color.
(2) Mechanical properties Polypropylene has high crystallinity and regular structure, so it has excellent mechanical properties. Its yield, tensile strength, compressive strength, hardness and elasticity are higher than HDPE, but at room temperature and low temperature, due to its own The molecular structure has a high degree of regularity, so the impulse strength is poor, and when the molecular weight is increased, the impact strength is also increased, but the molding processability is deteriorated. Polypropylene has outstanding bending fatigue strength, such as PP injection-body active hinge, can withstand 70 million opening and closing folding bending without damage marks, its friction resistance is also good, dry friction coefficient and nylon Similar, but in oil lubrication, the friction performance is obviously not as good as nylon. PP can only be used to make gears and bearings with low PV values ​​and no impact loads. In terms of surface effects, such as embossing, engraving, etc. on the surface of the article, it is easier than any other thermoplastic. Polypropylene products are particularly sensitive to gaps. Therefore, care must be taken when designing the mold to avoid the presence of sharp corners, otherwise stress concentration will easily occur and affect the service life of the product.
(3) Thermal properties Polypropylene has good heat resistance. Its melting point is 164~170 °C, and the product can be sterilized at a temperature above 100 °C. When it is not subjected to external force, it does not deform at 150 °C, and has good stress relaxation resistance at 90 °C. Its embrittlement temperature is -35 °C, brittle cracking occurs at temperatures below -35 °C, and cold resistance is not as good. Polyethylene, if reinforced with asbestos fibers and glass fibers, has a high heat distortion temperature, dimensional stability, and low temperature impact properties.
(4) Chemical stability The chemical stability of polypropylene is very good. Besides being attacked by concentrated sulfuric acid and concentrated nitric acid, it is stable to various other chemical reagents, but low molecular weight aliphatic hydrocarbons, aromatic hydrocarbons and chlorinated hydrocarbons. It can soften and swell polypropylene, and its chemical stability increases with the increase of crystallinity. Therefore, it is suitable for various chemical pipes and fittings, and has good anti-corrosion effect.
(5) Electrical properties Polypropylene has good high-frequency insulation properties, and since it hardly absorbs water, the insulation properties are not affected by humidity. It has a high dielectric constant and can be used to make heated electrical insulation products with increasing temperature. It has a high breakdown voltage and is suitable for use as an electrical accessory. It has good resistance to voltage and arc resistance, but it has high static electricity and is easy to age with copper.
(6) Weather resistance Polypropylene is very sensitive to ultraviolet light, and zinc oxide, thiopropionate dilaurin, carbon black or similar white filler can improve the aging resistance.
2. Molding processability polypropylene has good molding processability, so there are many molding methods, such as injection molding, extrusion molding, blow molding, vacuum thermal molding, coating, rotary molding, welding, machining, plating and foaming, etc. Metal surface painting. Generally, the PP melt index for injection molding is 3~4.5, and some can reach 20, its hygroscopicity is small, only 0.01%, so it only needs to be preheated in the general blast oven at 80~100 °C before molding. . When the PP is in contact with the metal wall for a long time, it will decompose and carbonize, so care should be taken not to cause it to stagnate in the barrel for a long time. In order to facilitate plasticization, it is better to lengthen the splitter. If the injection cycle is to be shortened, the injection temperature can be appropriately increased, and it is limited to the extent that no serious degradation occurs. It is very important to select an appropriate temperature during injection molding because the polypropylene molecules are easily oriented, strain is generated after molecular orientation, and impact strength is lowered, and the orientation phenomenon is most likely to occur at low temperature and high pressure injection, and thus the temperature cannot be too low. The mold temperature is preferably about 80 ° C, not lower than 50 ° C, otherwise the surface of the molded product is poorly glossed, or defects such as weld lines are generated, but the mold temperature is too high, the shrinkage of the product is too large and the depression occurs, so the pressure is as much as possible Improve some, generally mastered to not waste the edge as the standard.
The secondary processing performance of polypropylene is very good, its printing performance is better than that of polyethylene, and the printing methods such as photographic convex plate, offset plate and flat concave plate can be used. To obtain good printing performance of heat resistance, oil resistance and water resistance, It must be printed after corona discharge treatment. The products can be bronzing, printing, bonding, etc., and the bonding can be carried out by hot-adhesive method, solvent-based adhesive or high-frequency sealing, etc., and can be ultrasonically welded by hot air or thermal energy, and the welding performance is good. Electroplating is used for decorative parts such as instruments, meters, and electronics.
3. Modified polypropylene can be modified by filling, strengthening, blending, copolymerization and cross-linking. If fillers such as calcium carbonate, talc, minerals, etc. are added, rigidity, hardness, heat resistance and dimensional stability can be improved; glass is added. Fiber, asbestos fiber, mica, glass beads, etc. can improve tensile strength, and can improve creep resistance, low temperature impact resistance; add elastomer and rubber to improve impact performance, transparency; weather resistance, flame retardant Properties, conductivity, nucleation, antistatic properties, electroplatability, can also be solved with a variety of special additives.
4. Use Polypropylene homopolymer is polymerized from a single propylene monomer, with high crystallinity, good mechanical strength and heat resistance. The polypropylene copolymer is obtained by copolymerizing a small amount of ethylene monomer during polymerization, and has high impact strength, and the random copolymer has high impact strength and permeability.
Our advantages:
(1) multicolors
(2) Super Soft, Super absorbent, quick dry
(3) Clean and protect delicate surfaces
(4) Ecofriendly and compact
(5) Ideal for cleaning car,kitchen,window and more
(6) Remove visible and invisible dirt without any scratch
(7) No bad odors
(8) Easy to wash without detergent Materials:
80% Polyester 20% Polyamide, 100% polyester
Feature:
Soft hand, good water-absorbent ability
Size:
40cm*40cm, customized size available
Weight:
From 400-800gsm
Color:
Any pantone color
MOQ:
1 PCS
Custom Logo:
Available, printed & embroidery & embossed
Lint Free:
Yes
AZO free:
Yes
Production Capacity:
1,000,000 PCS/Month
OEM Service:
Yes
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