Polypropylene

Химические свойства

Polypropylene is a low-density resin that offers a good balance of thermal, chemical, and electrical properties, along with moderate strength. Strength can be significantly increased by using reinforcing agents such as glass fiber. Polypropylene has limited heat resistance, but it can be used in applications that must withstand boiling water or steam sterilization.
Polypropylenes can resist chemical attack and are unaffected by aqueous solutions of inorganic salts or mineral acids and bases, even at high temperatures. They are not attacked by most organic chemicals, and there is no solvent for these resins at room temperature. The resins are attacked, however, by halogens, fuming nitric acid, other active oxidizing agents, and by aromatic and chlorinated hydrocarbons at high temperatures .
Polypropylene is translucent and autoclavable. Properties can be improved by compounding with fillers, by blending with synthetic elastomers, and by copolymerizing with small amounts of other monomers.

Использование

Modifier for waxes to reduce blocking, scuffing and abrasion. Improves pigment dispersion in polypropylene films and fibers.

Определение

polypropylene: Anisotactic polymer existing in bothlow and high formula-weight forms.The lower-formula-weight polymer ismade by passing propene at moderatepressure over a heated phosphoricacid catalyst spread on aninert material at 200°C. The reactionyields the trimer and tetramer. Thehigher-formula-weight polymer isproduced by passing propene into aninert solvent, heptane, which containsa trialkyl aluminium and a titaniumcompound. The product is amixture of isotactic and atacticpolypropene, the former being themajor constituent. Polypropene isused as a thermoplastic mouldingmaterial.

Методы производства

In PP production, propylene monomer is polymerized to make the homopolymer by using a Ziegler–Natta type coordination catalyst. This catalyst results from the reaction and interaction of a transition metal compound and an organometallic compound, usually an alkylaluminum compound. Halide atoms are involved in most such catalyst systems .
Polypropylene can be made by solution, slurry (or solvent), bulk (or liquid propylene), or gas-phase polymerization, or a combination of these processes . The most widely used is the slurry process; however, the current trend is toward the gas-phase process. In the solution, slurry, and bulk processes, the catalyst system is mixed with propylene and a hydrocarbon diluent (usually hexane, heptane, or liquid propylene) in a reactor. After polymerization, the reaction mixture enters a flash tank where unreacted propylene is removed and recycled. Propylene–ethylene copolymers [9010-79-1] can be manufactured when ethylene is fed along with propylene to the polymerization reactor or by adding ethylene and propylene to a postpolymerization reactor that contains PP. This mixture may then be purified to remove lowmolecular weight and atactic fractions and washed to remove catalyst residues. The polypropylene resin is then dried and pelletized. During this time, additivesmay be incorporated in the gas-phase process; no liquid diluent is used .

Общее описание

Tan to white odorless solid. Less dense than water and insoluble in water. Hence floats on water.

Реакции воздуха и воды

Insoluble in water.

Профиль реактивности

Polypropylene reacts with chlorine, fuming nitric acid and other strong oxidizing agents.

Опасность

Questionable carcinogen.

Угроза здоровью

No apparent toxicity

Промышленное использование

Polypropylene is similar in structure to polyethylene,but every other carbon atom has oneof its H2 atoms replaced by a CH2group.Although electrically similar to polyethylene,polypropylene can be made in thinner films, say 5μm as against about 25 μm for polyethylene.These films replace paper for impregnatedcapacitors, with reduced loss.

Профиль безопасности

Moderately toxic by ingestion and intraperitoneal routes. Questionable carcinogen. When heated to decomposition it emits acrid smoke and irritating fumes. Used in injection molding for auto parts, in bottle caps, and in container closures.

Канцерогенность

No data on the carcinogenicity and mutagenicity of propylene are available for evaluation by the working group.