There are Several major plastics of
1, polyethylene plastic Branch
Polyethylene plastic is a polymer of ethylene monomers. Raw materials oil, coke oven gas or alcohol. Industrial production of polyethylene in general, alcohol dehydration, catalytic hydrogenation or pyrolysis of acetylene obtained. Its trade names referred to as "B & S"; English abbreviated as PE. As the density of polyethylene of different sizes, divided into low-density polyethylene. [PE (L)], medium-density polyethylene [PE (M)] and high-density polyethylene [PE (H)].
The molecular structure of polyethylene: (-CH2 1 CH2-) n. It is the linear geometry, in theory there is no branched-chain, prone to crystallization. Polyethylene macromolecules are usually from the crystalline region and in the high-elastic state of amorphous zones staggered formation; crystalline region of polyethylene plastic to give a higher hardness, strength, chemical stability, etc.; amorphous zone to give a higher soft polyethylene plastic Xing, toughness, and transparency. In fact, the PE molecules is not absolutely branch chain. Its crystallization degree of different densities are also different, there are differences in physical and mechanical properties.
1. Low-density polyethylene
Also known as "high-voltage soft plastic." It is made of ethylene monomer with micro-oxygen as initiator, in 1200 a 2000 atm, the temperature is 100 1 300 ¡æ under the conditions of oxygen, organic peroxides or azo compounds as initiators for polymerization.
2. Medium-density polyethylene
In the 30-70 atmospheric pressure, the temperature is l00-250 ¡æ condition, using chromium oxide or molybdenum oxide as catalyst synthesis of medium-density polyethylene. Practice, obtained with use of the following methods:
¢Ù the low-density polyethylene and high-density polyethylene obtained by blending a certain percentage;
¢Ú The slurry method or solution method, from ethylene and propylene, butylene and other second monomers obtained;
¢Û Production of high-pressure, from ethylene and vinyl acetate, acrylic esters second monomers obtained, or to control the ethylene conversion rate is very low under the conditions obtained;
¢Ü using gas law too.
3. High-density polyethylene
It is the atmospheric pressure of 10 atmospheres, and under the condition of 60-80 ¡æ, with alkyl aluminum and titanium tetrachloride-based catalyst for polymerization of.
1. Physical and mechanical properties
PE as a milky white translucent wax-like body of material, lighter than water, odorless and tasteless non-toxic; HDPE soft, LDPE rigid; permeability decreases with the increase of the density of N2, O2, CO2 and other thin film of air permeability comparison, HDPE large, but relatively to the water vapor permeability was small; PE low temperature performance is the best general-purpose plastics, the embrittlement temperature of -70 ¡æ, but not heat; HDPE strength and hardness than the good, but the impact strength, poor flexibility, transparency is low; while the LDPE and vice versa.
Between the performance of MDPE between
2. Resistance to chemical corrosion
PE at room temperature capability in general acid, alkali, salt, but the intolerance concentrated in H2SO4, HNO3, at 60 ¡æ for the following capability in most organic solvents, aliphatic hydrocarbons, aromatic hydrocarbons and chlorinated hydrocarbons in the swelling.
3. Anti-aging properties
PE in the air under the action of the slow degradation of O2; heat, ultraviolet radiation, the role of high-energy radiation, degradation speed.
4. Insulation performance
Small dielectric constant.
5. Bonding, printing, coloring poor.
(D) combustion characteristics of
Flammable, away from the fire continued to burn after, and released the same with the smell of burning paraffin wax; combustion, the flame tip yellow, the bottom of the blue; smoke less; burning edge melting, side burn, side dripping.
(E) use of
Very extensive use of low-density polyethylene using extrusion blow molding method can produce films, hollow containers, pipe can be produced using extrusion method, using extrusion rolling method, in order to kraft paper as the substrate composite films can be produced using injection can be production of daily necessities, such as baby bottles, soap box, toys, cups, plastic flowers.
Medium-density polyethylene is mainly used for production of all kinds of bottle products, insulating products, cable products and high-speed automatic packaging film.
High-density polyethylene plastic, high strength, wear resistance, it is mainly used for manufacture of rope, packing tape, etc. can also produce boxes, barrels, shells, etc. thermos.
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