Polypropylene, propylene prepared by the polymerization of a thermoplastic resin. Methyl-arranged position into isotactic polypropylene (isotactic polypropylene), random polypropylene (atactic polypropylene) and syndiotactic polypropylene (syndiotactic polypropylene) three.
Methyl arranged in the main chain of the same side of said isotactic polypropylene, if methyl disorderly arranged on both sides of the main chain, said random polypropylene, methyl alternately arranged in the main chain between the two sides, said isotactic polypropylene. General industrial production of polypropylene resins, the isotactic structure content of about 95%, the remainder being atactic or syndiotactic polypropylene. Industrial products isotactic thereof as a main component. Polypropylene also includes small amount of propylene copolymers, including ethylene. Usually translucent colorless solid, odorless and non-toxic. Due to regular and highly crystalline structure, so the melting point of up to 167 ℃. Heat-resistant, corrosion-resistant products available steam sterilization is its advantage. Density, is the lightest general-purpose plastics. The disadvantage is poor low temperature impact resistance, easier to aging, but can be overcome by modifying respectively.
Copolymer PP materials have a lower heat distortion temperature (100 ℃), low transparency, low gloss, low rigidity, but there is a stronger impact strength, impact strength of PP increased with increasing ethylene content . PP Vicat softening temperature of 150 ℃. Due to the high degree of crystallinity, surface rigidity and scratch resistance properties of this material is very good. PP environmental stress cracking problem does not exist.
PP melt mass flow rate (MFR) is usually 1 to 100. Low MFR PP material better impact properties, but the extension of lower intensity. MFR for the same material, copolymer impact strength than homo-type is higher. Crystal, PP contraction rate is very high, typically 1.6 to 2.0%.
Physical properties of Polypropylene:
Polypropylene is non-toxic, odorless, tasteless milky white highly crystalline polymers, density of only 0. 90 -. "0 91g / cm3, is one of the lightest of all the plastic varieties it particularly stable water. the water absorption of only 0.01%, a molecular weight of about 8 150 000 in case. moldability is good, but the shrinkage (1% to 2.5%). thick-walled products easy to depression, some high dimensional accuracy parts, it is difficult to meet the requirements, product surface gloss.
Mechanical properties of Polypropylene:
High crystallinity polypropylene, regular structure, which has excellent mechanical properties. Higher than the absolute value of the mechanical properties of polypropylene, polyethylene, a plastic material, but remained at a low species, its tensile strength reaches 30 MPa or only slightly higher level. Regulatory and other large index of polypropylene has a high tensile strength, but increases with isotactic index, impact strength decreased, but not down to a certain value
Polypropylene resin
Polypropylene resin
Then change.
Temperature and strain rates a great influence on the toughness of polypropylene. When the temperature is higher than the glass transition temperature, fracture toughness, impact damage was below the glass transition temperature of brittle fracture and impact strength values dropped significantly. Improve the loading rate can rise to the fracture toughness of brittle fracture transition temperature. Polypropylene has excellent resistance to bending fatigue resistance, and its products at room temperature can be bent 106 times without damage.
However, at room and low temperatures, high regularity molecular structure itself, so that the poor impact strength. The most outstanding performance is the bending fatigue resistance of polypropylene, commonly known as the pleated plastic.
Thermal Performance
Polypropylene has good heat resistance, the article can be sterilized at a temperature above 100 ℃, under the condition without outside, 150 ℃ not deformed. Brittle transition temperature of -35 ℃, below -35 ℃ embrittlement occurs, cold resistance than polyethylene. Values reported for polypropylene has a glass transition temperature 18qC, 0qC, 5 ℃, etc. This is because people with different samples, which contained different crystal phase and amorphous phase proportion, so that the molecular chain of different chain lengths amorphous part due. Higher than the melting temperature of polypropylene polyethylene about 40 to 50%, about 164 a 170 ℃, 100% isotactic polypropylene having a melting point of 176 ℃.
Chemical stability
Chemical stability of polypropylene well, in addition to be concentrated sulfuric acid, concentrated nitric acid erosion, but a variety of other chemical reagents are relatively stable, but low molecular weight aliphatic hydrocarbons, aromatic hydrocarbons and chlorinated hydrocarbons soften and make polypropylene swelling, while its chemical stability also improved with increasing degree of crystallinity, it is suitable for the production of polypropylene pipes and fittings of various chemical, anti-corrosion effect is good.
Electrical Properties
It has a high dielectric constant with increasing temperature, the heat can be used to produce electrical insulation products. It is also high breakdown voltage, suitable for use as electrical accessories. Anti-voltage arc resistance, static high copper contacts easy to aging.
Weatherability
Polypropylene UV-sensitive, adding zinc oxide, dilauryl thiodipropionate, carbon black or similar creamy white fillers to improve its anti-aging properties.
Hydrophobic parameter calculation reference value (XlogP): 3.32, the number of hydrogen bonds for the body: 03, number of hydrogen bond acceptor: 34 rotatable bond number: 15, the number of mutual tautomers: 6, topological molecular polar surface area (TPSA ): 29.5 avoid strong oxidizing agents, chlorine, potassium permanganate closed, cool and dry place to ensure that there is good ventilation.
Polypropylene Features:
Non-toxic, tasteless, density, strength, stiffness, hardness and heat resistance are superior to low pressure polyethylene, can be used at 100 ℃. It has good dielectric properties and high-frequency insulation and is not humidity, but the low temperature brittle, do not wear, easy to aging. Suitable for production of general machinery parts, corrosion-resistant parts and insulating parts. Common acid and alkali organic solvents it almost does not work, can be used for utensils.
Polypropylene has many excellent features:
1, the relative density of small, only 0.89-0.91, is one of the lightest plastic varieties.
2, good mechanical properties, in addition to impact resistance, the other mechanical properties than polyethylene, good processing behavior.
3, has a high heat resistance, continuous use temperature up to 110-120 ℃.
4, good chemical resistance, almost non-absorbent, does not react with most chemicals.
5, pure texture, non-toxic.
6, good electrical insulation.
7, polypropylene products, transparency is high density polyethylene products, good transparency.
It has many advantages but also disadvantages:
1, poor cold products, low temperature impact strength.
2, the product in use, subject to the action of light, heat and oxygen and aging.
3, the coloring is not good.
4, easy to burn.
5, good toughness, high static electricity, dyeing, printing and poor adhesion.
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