operating characteristic
Physical properties of 1
Polypropylene is a non-toxic, odorless and highly crystalline polymer with a density of only 0. 90-"0.9 1g/rm is one of the lightest plastics at present. It is particularly stable to water, and its water absorption in water is only 0. O 1%, and the molecular weight is about 80,000-1.5 million. Good formability, but due to the large shrinkage (1%~2.5%), thick-walled products are prone to sag, and some mechanical properties and dimensional accuracy are 2 2:
The higher part is difficult to meet the requirements, and the product has good surface gloss and is easy to color.
Polypropylene has high crystallinity and regular structure, so it has excellent mechanical properties. The absolute value of mechanical properties of polypropylene 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. Polypropylene with larger isotactic index has higher tensile strength.
Strength, but with the increase of isotactic index, the impact strength of the material decreases, but it remains unchanged 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 glass transition temperature, the impact failure is ductile fracture, and when it is lower than the glass transition temperature, it is brittle fracture, and the impact strength value decreases greatly. Increasing loading rate can increase the transition temperature from ductile fracture to brittle fracture. Polypropylene has excellent bending fatigue resistance, and its products can be bent 106 times at room temperature without damage.
However, at room temperature and low temperature, due to its high molecular structure regularity, its impact strength is poor. The most outstanding performance of polypropylene is bending fatigue resistance, commonly known as hundred-fold adhesive.
3 Thermal performance:
Polypropylene has good heat resistance, and the product can be sterilized at the temperature above 100℃, and will not deform at 150℃ without external force. Brittle temperature is -35℃, and it will be brittle below -35℃, and its cold resistance is not as good as that of polyethylene. The reported glass transition temperatures of polypropylene are 18qC, OqC, 5℃ and so on. This is also because people use different samples, which contain different proportions of crystalline phase and amorphous phase, resulting in different chain lengths of amorphous parts in molecular chains. The melting temperature of polypropylene is about 40-50% higher than that of polyethylene, about 164- 170℃, and the melting point of 100% isotactic polypropylene is 176℃.
4 chemical stability:
The chemical stability of polypropylene is very good, except that it can be corroded by concentrated sulfuric acid and concentrated nitric acid, and it is relatively stable to other chemical reagents. However, low molecular weight aliphatic hydrocarbons, aromatic hydrocarbons and chlorinated hydrocarbons can soften and swell polypropylene, and at the same time, its chemical stability increases with the increase of crystallinity, so polypropylene is suitable for making various chemical pipelines and fittings with good anticorrosion effect.
5 Electrical performance:
It has a high dielectric constant and can be used to make heated electrical insulation products with the increase of temperature. Its breakdown voltage is also very high, and it is suitable for electrical accessories. Good voltage and arc resistance, but high static electricity, easy to age in contact with copper.