production method: slurry method. Polymerization in diluent (such as hexane) is the earliest industrialized method and the largest production so far. Liquid bulk method. Polymerization was carried out in liquid propylene at 7℃ and 3MPa. Polymerization is carried out under the condition that propylene is gaseous. The latter two methods do not use diluent, which is short in process and low in energy consumption. The liquid-phase bulk method has now shown the advantage of coming from behind. Molding characteristics: Physical properties: PP is a non-toxic, odorless, milky white and highly crystalline polymer, which is one of the lightest varieties of all plastics at present. It is particularly stable to water, and its water absorption in water for 14 hours is only .1%. The molecular weight is about 8, ~ 15,, and the formability is good. However, due to the large shrinkage, the original wall products are easy to sag, and the products have good surface gloss and are easy to be colored. Mechanical properties: PP has excellent mechanical properties due to its high crystallinity and regular structure, and its strength, hardness and elasticity are higher than those of HDPE. The outstanding feature is the bending fatigue resistance (7× 1 7), and the dry friction coefficient is similar to nylon, but it is not as good as nylon under oil lubrication. Thermal properties: PP has good heat resistance, the melting point is 164~17℃, and the product can be sterilized at a temperature above 1℃. Under the action of no external force, it does not deform at 15℃. Embrittlement is -35℃, and embrittlement will occur below -35℃, and the heat resistance is not as good as that of PE.
chemical stability: PP has good chemical stability, which is relatively stable to other chemical reagents except concentrated sulfuric acid and concentrated nitric acid, but low molecular weight aliphatic hydrocarbons and aromatic hydrocarbons can soften and swell PP, and the chemical stability is improved with the increase of crystallinity. Therefore, PP is suitable for making Russian-Chinese chemical pipelines and fittings, with good anti-corrosion effect. Polypropylene has excellent high-frequency insulation performance. Because it hardly absorbs water, its insulation performance is not affected by humidity, and it has a high dielectric coefficient. With the increase of temperature, it can be used to make heated electrical insulation products, and its breakdown voltage is also very high, so it is suitable for electrical accessories. Good voltage resistance and arc resistance, but high static electricity, easy to age in contact with copper. Polypropylene is very sensitive to ultraviolet rays, and its aging resistance can be improved by adding zinc oxide lauryl thiopropionate and carbon black similar milky white filler.