Views: 36 Author: Site Editor Publish Time: 2018-11-12 Origin: Site
Polypropylene is a thermoplastic resin made by polymerization of propylene.They are classified into three types according to the position of methylpolypropylene, atpi polypropylene and syndiotpi polypropylene. When methyl is arranged on the same side of the molecular main chain, it is called isotactic polypropylene. If methyl is arranged irregularly on both sides of the molecular main chain, it is called random polypropylene. When methyl is arranged alternately on both sides of the molecular main chain, it is called intercalary polypropylene.In general industrial polypropylene resins, the content of isoformic structure is about 95%, the rest is random or interformable polypropylene.Industrial products are mainly composed of isotactic materials.Polypropylene also includes a copolymer of propylene with a small amount of ethylene.Usually transparent colorless solid, odorless non - toxic.Because of its neat and high crystallization structure, so the melting point can be as high as 167 ℃.Heat - resistant, corrosion - resistant products available steam disinfection is its outstanding advantages.Low density is the lightest general purpose plastic.The disadvantages are poor impact resistance and easy aging, but can be overcome by modification. Copolymer of PP material with low thermal deformation temperature (100 ℃), low transparency and gloss, low rigidity, but have stronger impact strength, impact strength of PP increased with the increase of ethylene content increased.PP vicat softening temperature is 150 ℃.Due to high crystallinity, this material has good surface stiffness and scratch resistance.PP does not have the problem of environmental stress cracking. The melt mass flow rate (MFR) of PP is usually between 1 and 100.Low MFR PP material has good impact resistance but low tensile strength.For materials with the same MFR, the impact strength of the copolymerization type is higher than that of the homogenous type.Due to crystallization, PP shrinkage is quite high, generally 1.6~2.0%.
Physical properties: polypropylene is a non-toxic, odorless, tasteless opalescent polymer with a density of 0.90 --" 0.91g /cm3, one of the lightest of all plastics available.It is particularly stable to water, with a water absorption rate of only 0.01% and a molecular weight of about 81.15 million.Good molding, but due to large shrinkage rate (1%~2.5%). Thick wall products are easy to sag, for some parts with high dimensional accuracy, it is very difficult to meet the requirements, products with good surface gloss.
Polypropylene has excellent mechanical properties due to its high crystallinity and regular structure.The absolute value of polypropylene's mechanical properties is higher than that of polyethylene, but it is still a low variety in plastic materials, and its tensile strength can only reach 30 MPa or slightly higher level.The polypropylene with large isometric index has higher tensile strength. However, with the increase of isometric index, the impact strength of the material decreases, but does not change after falling to a certain value.
Temperature and loading rate have great influence on the toughness of polypropylene.When the temperature is higher than the vitrification temperature, the impact failure is ductile fracture, while the temperature is lower than that of vitrification is brittle fracture, and the impact strength value decreases greatly.Increasing the loading rate can increase the temperature of ductile fracture to brittle fracture.Polypropylene has excellent resistance to bending fatigue, and its products can be bent 106 times at room temperature without damage.
However, at room temperature and low temperature, the impact strength is poor due to the high degree of molecular structure.Polypropylene is the most outstanding performance is bending fatigue, commonly known as 100 fold glue.However, at room temperature and low temperature, the impact strength is poor due to the high degree of molecular structure.Polypropylene is the most outstanding performance is bending fatigue, commonly known as 100 fold glue.
Polypropylene has good heat resistance, products can be in above 100 ℃ temperature disinfection sterilization, under the condition of not affected by external forces, 150 ℃ and deformation.Brittle temperature - 35 ℃, 35 ℃ below - will happen embrittlement, cold tolerance than polyethylene.Reported values for polypropylene glass transition temperature of a 18 qc, 0 qc, 5 ℃, it is also because people with different samples, containing crystalline and amorphous facies proportion is different, make the molecular chains in the amorphous part of different chain length.Than polyethylene polypropylene melt temperature around 40 a 50%, about 164 an 170 ℃, 100% degree of isotactic polypropylene melting point is 176 ℃.
Polypropylene has a good chemical stability, besides can be concentrated sulfuric acid, nitric acid erosion, for other kinds of chemical reagents are stable, but the low molecular weight fatty hydrocarbon, aromatic hydrocarbon and chlorinated hydrocarbon can make polypropylene softening and swelling, such as its chemical stability at the same time there is some increase with the increase of the crystallinity, chemical pipe and fittings for the production, so the polypropylene anti-corrosion effect is good.
It has a high dielectric coefficient, and with the rise of temperature, can be used to make heating electrical insulation products.Its breakdown voltage is also very high, suitable for use as electrical accessories, etc.Good resistance to voltage and arc, but high electrostatic, and copper contact aging.Weather:
Polypropylene is very sensitive to ultraviolet light. Adding zinc oxide, dilauryl thiolate, carbon black or similar white filler can improve its aging resistance.
Hydrophobic parameter calculation reference (XlogP) : 3.32, the number of hydrogen bonding donor: 03, hydrogen bond receptor number: 34, the number of rotating chemical bonds: 15, tautomer quantity: 6, topological molecular polar surface area (TPSA) : 29.5 to avoid strong oxidizer, chloride, potassium permanganate sealed, a cool and dry place preserve, ensure good ventilation.