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Some knowledge about PP Plastics
- Apr 11, 2018 -

Talking about polypropylene Everyone must be confused, but said that plastic is clear, pp plastic is polypropylene, propylene polymerization by the preparation of a thermoplastic resin. According to the position of the methyl is divided into the same regulation of polypropylene, polypropylene, and three kinds of polypropylene.


So, what is PP plastic?

What is PP plastic

PP plastic, chemical name: polypropylene

English name: polypropylene (PP)

Specific gravity: 0.9-0.91 g/cubic centimeter molding shrinkage: 1.0-2.5% Molding temperature: 160-220 ℃ Features: non-toxic, tasteless, degree of small, strength stiffness, hardness and heat resistance are better than low pressure polyethylene, can be used around 100 degrees. With good electrical properties and high frequency insulation is not affected by humidity, but low-temperature time-varying brittle, not wear-resistant, easy aging. Suitable for general mechanical parts, corrosion-resistant parts and insulating parts.


The common acid and alkali organic solvents have little effect on it and can be used for utensils.

PP Plastic Molding characteristics:

1. The crystallization material, moisture absorption is small, easy to occur melts the body to rupture, long-term and hot metal contact easy decomposition.

2. The fluidity is good, but the shrinkage scope and the shrinkage value are big, easy to happen the shrinkage hole. Dents, deformations.

3. Cooling speed, gating system and cooling system should be slow cooling, and pay attention to control the molding temperature. Low temperature and high pressure when the material temperature is easy to orientation, mold temperatures below 50 degrees, plastic parts are not smooth, easy to produce poor weld, flow marks, more than 90 degrees prone to warping deformation

4. Plastic wall thickness should be even, avoid the lack of glue, sharp angle, to prevent stress concentration.


Second, pp plastic properties

Physical properties Polypropylene is non-toxic, odorless, tasteless milky high crystalline polymers, the density is only 0. 90-- "0. 91G/RM is one of the lightest varieties of plastics at present. It is particularly stable to water, the water absorption rate is only 0. o1%, the molecular weight is about 801.15 million.

The molding is good, but because the shrinkage rate is big (for 1%~2.5%). Thick-walled products are easy to sag, for some of the higher precision parts, but also difficult to meet the requirements, the product surface gloss is good, easy to color.


Mechanical properties Polypropylene has excellent mechanical properties because of its high crystallinity and regular structure. The absolute value of polypropylene mechanical properties is higher than that of polyethylene, but it is still a low type in plastic material, and its tensile strength can only reach MPA or slightly higher level.

The high tensile strength of polypropylene with higher gauge index, but with the increase of the gauge index, the impact strength of the material decreased, but dropped to a certain value and no longer changed. Temperature and loading rate have great effect on the toughness of polypropylene. When the temperature is higher than the glass temperature, the impact damage is ductile fracture, the brittle fracture is lower than the glass temperature, and the impact strength value decreases greatly. Increasing the loading rate can increase the temperature of ductile fracture transition to brittle fracture.

Polypropylene has excellent bending fatigue resistance, its products can be bent 106 times at room temperature without damage. But at room temperature and at low temperature, the impact strength is poor because of the high structure regularity. Polypropylene's Most outstanding performance is the bending fatigue resistance, commonly known as 100 glue.