What Is The Difference Between PE And PP Plastic?

- May 14, 2019-

What is the difference between PE and PP plastic?

   Both PP and PE are saturated hydrocarbons, which are similar in many respects, but differ in some important properties. In addition to ultra high molecular weight polyethylene, PP has a higher melting point and glass transition temperature than PE, but PP requires a higher processing temperature.

What is PE? What are the characteristics and characteristics?

   Polyethylene is abbreviated as PE, which is a thermoplastic resin obtained by polymerization of ethylene. Industrially, copolymers of ethylene and a small amount of an α-olefin are also included. Polyethylene is odorless, non-toxic, feels like wax, has excellent low temperature resistance (minimum use temperature can reach -70~-100°C), good chemical stability, and can resist most acid and alkali corrosion (not resistant to oxidizing properties) The acid is insoluble in common solvents at normal temperature, has low water absorption and excellent electrical insulation properties; however, polyethylene is very sensitive to environmental stress (chemical and mechanical action) and has poor heat aging resistance. The nature of polyethylene varies from species to species and depends primarily on molecular structure and density. Products of different densities (0.91 to 0.96 g/cm3) can be obtained by different production methods. Polyethylene can be processed by conventional thermoplastic molding methods (see plastic processing). It is widely used in the manufacture of films, containers, pipes, monofilaments, wires and cables, daily necessities, etc., and can be used as high-frequency insulation materials for televisions, radars, etc.

Type of PE:

(1) LDPE: low density polyethylene, high pressure polyethylene

(2) LLDPE: linear low density polyethylene

(3) MDPE: medium density polyethylene, bimodal resin

(4) HDPE: high density polyethylene, low pressure polyethylene

(5) UHMWPE: Ultra High Molecular Weight Polyethylene

(6) Modified polyethylene: CPE, cross-linked polyethylene (PEX)

(7) Ethylene copolymer: copolymer of ethylene-propylene copolymer (plastic), EVA, ethylene-butene copolymer, ethylene-other olefin (such as octene POE, cyclic olefin), ethylene-unsaturated ester copolymer ( EAA, EMAA, EEA, EMA, EMMA, EMAH)

  PE characteristics: corrosion resistance, electrical insulation (especially high frequency insulation), chlorination, chemical crosslinking, radiation crosslinking modification, glass fiber reinforced. Low melting polyethylene melting point, rigidity, hardness and strength High, low water absorption, good electrical properties and radiation resistance; high-pressure polyethylene has good flexibility, elongation, impact strength and permeability; ultra-high molecular weight polyethylene has high impact strength, fatigue resistance and wear resistance. Low-pressure polyethylene is suitable for making corrosion-resistant parts and insulating parts; high-pressure polyethylene is suitable for making films; ultra-high molecular weight polyethylene is suitable for making shock absorption, wear-resistant and transmission parts.

Molding characteristics:

 1. Crystallized material, low moisture absorption, no need to fully dry, excellent fluidity, fluidity is sensitive to pressure, high pressure injection should be used during molding, material temperature is uniform, filling speed is fast, pressure is sufficient. It is not suitable to use direct gate to prevent shrinkage Uneven, the internal stress increases. Pay attention to the location of the gate to prevent shrinkage and deformation.

 2. Shrinkage range and shrinkage value are large, the direction is obvious, easy to deform and warp. The cooling speed should be slow, the mold is set with cold material, and there is cooling system.

 3. Heating time should not be too long, otherwise decomposition will occur.

 4. When the soft plastic part has a shallow side groove, it can be forced to demould.

 5. The melt may break and it is not suitable to contact with organic solvents to prevent cracking.

 High-pressure polyethylene: more than half for film products, followed by pipes, injection molded products, wire wraps, etc.

 LDPE and MDPE: mainly injection molded products and hollow products.

 UHMWPE: Due to the excellent comprehensive properties of ultra-high molecular polyethylene, it can be used as engineering plastics.

What is PP?  what is the Features and characteristics ?

   Polypropylene, abbreviated as PP, is a thermoplastic resin obtained by polymerizing propylene. There are three configurations of isotactic, random and syndiotactic, and industrial products are mainly composed of isotactics. Polypropylene also includes copolymers of propylene and a small amount of ethylene. Usually a translucent, colorless solid, odorless and non-toxic. Due to the regular structure and high crystallization, the melting point is as high as 167 ° C, heat resistance, steam sterilization of products can be its outstanding advantages. With a density of 0.90g/cm3, it is the lightest general purpose plastic. Corrosion resistance, tensile strength 30MPa, strength, rigidity and transparency are better than polyethylene. The disadvantage is that it is poor in low temperature impact resistance and easy to age, but can be overcome by modification and addition of antioxidants.

Features: non-toxic, odorless, low density, strength, stiffness, hardness and heat resistance are better than low-pressure polyethylene, can be used at about 100 degrees. Has good electrical properties and high-frequency insulation is not affected by humidity, but at low temperatures It becomes brittle, non-abrasion resistant and easy to age. It is suitable for making general mechanical parts, corrosion resistant parts and insulating parts. Common acid and alkali organic solvents have little effect on it and can be used in food utensils.

Molding characteristics:

1. Crystalline material, low hygroscopicity, easy to cause melt fracture, long-term contact with hot metal is easy to decompose.

2. Good fluidity, but the shrinkage range and shrinkage value are large, and shrinkage, dent and deformation are easy to occur.

3. The cooling rate is fast, the pouring system and the cooling system should be slowly dissipated, and the molding temperature should be controlled. When the material temperature is low temperature and high pressure, the orientation is easy. When the mold temperature is lower than 50 °C, the plastic parts are not smooth, and the welding is not easy. , 90 ° C or more is prone to warping deformation.

4. Plastic wall thickness should be uniform to avoid lack of material and sharp corners to prevent stress concentration

The same points and differences between PE and PP:

Same point: 

1. PE, PP uncolored are all milky white translucent, waxy polymer.

2. Both are non-polar crystalline polymers with good compatibility.

3. Non-toxic, good chemical stability, easy to shape and process.

4. Poor weather resistance.

The difference: 

1. PP has better rigidity, strength and heat resistance than PE, and PE is easily decomposed by photooxidation, thermal oxidation and ozone.

2. PP density is smaller than PE, and PP density is only 0.90~0.91g/cm3.

3. PP toughness is poor at low temperatures

  Asia Billion as a custom plastic injection molding company and high quality injection mould maker, we use a lot of PP, HDPE and LDPE material in our pasted experience,  we have many projects for medical device , electronic, food industry and commodity.  if you want to find a good partner for you project. contat us freely at:

Asia Billion Innovational Technology Ltd


Mobile for business:  +86-134 8063 8827

Previous:The 33rd Chinaplas Industrial Exhibition Was Held At Carton Fair Next:How Much Is A Plastic Injection Mold ?