Gray PP rod Gray PP rod White PP board [diameter]

r, >Polypropylene is a
thermoplastic resin: r, > produced by the polymerization of
propylene: r, >. According to the arrangement position of
Methyl group: r, >, it is divided into
isotactic polypropylene: r, >(r),
atactic polypropylene: r, >(r) and
Syndiotactic polypropylene: r, >(r) three types.
Methyl groups: r, > are arranged on the same side of the main chain of the molecule, which is called isotactic polypropylene.
<:rr, ,
If the methyl groups are arranged randomly on both sides of the main chain of the molecule, it is called isotactic polypropylene. When the methyl groups are alternately arranged on both sides of the main chain of the molecule, it is called syndiotactic polypropylene. In general industrially produced polypropylene resin, the isotactic structure content is about 10%, and the rest is atactic or syndiotactic polypropylene. Industrial products contain isoforms as main components. Polypropylene also includes copolymers of propylene and a small amount of ethylene. It is usually a translucent colorless solid, odorless and non-toxic. Due to its regular structure and high degree of crystallization, the melting point can be as high as ℃. Heat resistance and corrosion resistance, and the products can be sterilized by steam are its outstanding advantages. It has low density and is the lightest general-purpose plastic. The disadvantages are poor low-temperature impact resistance and easy aging, but these can be overcome through modification.
<:rr, , Copolymer-type materials have lower heat distortion temperature (℃), low transparency, low gloss, and low rigidity, but have stronger impact strength. The impact strength increases with that of ethylene. Increases with increasing content. The Vicat softening temperature is ℃. Due to its high degree of crystallinity, this material has good surface stiffness and scratch resistance. There are no environmental stress cracking issues.
<:rr, , the melt mass flow rate) is usually ~. Materials with low R have better impact resistance but lower ductile strength. For materials with the same R, the impact strength of the copolymer type is higher than that of the homopolymer type. Due to crystallization, the shrinkage rate is quite high, generally... Polypropylene is a non-toxic, odorless and tasteless milky white highly crystalline polymer with a density of only . . /crrrb : .>
. It is one of the lightest varieties of all plastics currently. It is particularly stable to water, its water absorption rate in water is only . , and its molecular weight is about 10,000. The formability is good, but due to the large shrinkage (~.), thick-walled products are easy to dent, and it is difficult to meet the requirements for some parts with high dimensional accuracy. The surface of the product is glossy and easy to color. : >Polypropylene has high crystallinity and regular structure, so it has excellent mechanical properties. The absolute value of the mechanical properties of polypropylene is higher than that of polyethylene, but it is still on the low side among plastic materials, and its tensile strength can only reach or slightly higher levels. Polypropylene with a larger isotactic index has higher tensile strength, but as the isotactic index increases, the impact strength of the material decreases, but does not change after it drops to a certain value.
<:rr, , Temperature and loading rate have a great influence on the toughness of polypropylene. When the temperature is higher than the glass transition temperature, the impact damage will be ductile fracture, and below the glass transition temperature, it will be brittle fracture, and the impact strength value will decrease significantly. Increasing the loading rate can increase the temperature at which ductile fracture transitions to brittle fracture. Polypropylene has excellent resistance to bending fatigue, and its products can be bent several times at room temperature without damage.
<:rr, , However, at room temperature and low temperature, due to its high regularity in molecular structure, its impact strength is poor. The most outstanding performance of polypropylene is its resistance to bending fatigue, commonly known as Baizhe glue.