NEWS

　　What is polypropylene (PP) and what is it used?

Polypropylene (PP) is a thermoplastic addition polymer made from a combination of propylene monomers. A wide range of applications, including consumer packaging, plastic parts for the automotive industry and textiles. Philips scientists Paul Hogan and Robert Banks first made polypropylene in 1951, and later Italian and German scientists Natta and Rehn also made polypropylene. Natta perfected and synthesized the first polypropylene commodity in Spain in 1954, and its ability to crystallize aroused great interest. By 1957, polypropylene's popularity surged and widespread commercial production began throughout Europe. Today, it is one of the most commonly used plastics in the world.

Medicine box made of PP with living hinged lid

According to reports, the current global demand for PP materials is about 45 million tons per year, and it is estimated that the demand will grow to about 62 million tons by the end of 2020. The main application of PP is the packaging industry, accounting for about 30% of the total consumption. This is followed by electrical and equipment manufacturing, which consumes about 26%. The household appliances and automobile industries each consume 10%. Construction industry consumption accounted for 5%.

PP has a relatively smooth surface and can replace some other plastic products, such as gears made of POM and foot pads for furniture. The smooth surface also makes it difficult to bond PP to other surfaces, that is, PP cannot be firmly bonded with industrial glue, and sometimes welding must be used for bonding. PP also has a low density relative to other plastics, which can reduce weight for users. PP has excellent resistance to organic solvents such as grease at room temperature. However, PP is easily oxidized at high temperature.

One of the main advantages of PP is its excellent processing properties, which can be formed by injection molding or CNC machining. For example, PP medicine box, the lid is connected to the bottle body by living hinge. The medicine box can be directly processed by injection molding or CNC. The living hinge that connects the lid is a very thin piece of plastic that can be bent repeatedly (with an extreme range of movement approaching 360 degrees) without breaking. Although the living hinge made of PP can not bear the load, it is very suitable for application on the bottle cap of daily necessities.

Another advantage of PP is that it can be easily copolymerized with other polymers (such as PE) to form composite plastics. The copolymer significantly changes the properties of the material, allowing for more robust engineering applications compared to pure PP.

Another inestimable application is that PP can act both as a plastic material and as a fiber material.

The above characteristics mean that PP can be used in many applications: plates, trays, cups, tote bags, opaque plastic containers, and many toys.

　　What are the characteristics of PP?

The most important characteristics of PP are as follows:

Chemical resistance: Diluted alkalis and acids do not react with PP, which makes it an ideal container for such liquids (such as cleaning agents, first aid products, etc.). Elasticity and toughness: PP is elastic within a certain range of deflection, and will undergo plastic deformation without breaking in the early stage of deformation, so it is usually considered a "tough" material. Toughness is an engineering term defined as the ability of a material to deform (plastically rather than elastically) without breaking. Fatigue resistance: PP retains its shape after a lot of twisting and bending. This feature is particularly valuable for making living hinges. Insulation: PP material has high resistance and is an insulating material. Transmittance: It can be made transparent, but it is usually made into a natural opaque color with a certain color transmittance. If high transmittance is required, acrylic or PC should be selected. PP is a thermoplastic with a melting point of about 130 degrees Celsius and becomes a liquid after reaching the melting point. Like other thermoplastics, PP can be repeatedly heated and cooled without significant degradation. Therefore, PP can be recycled and easily recovered.

　　What are the different types of PP?

There are two main types: homopolymers and copolymers, with copolymers being further divided into block copolymers and random copolymers. Each category has unique applications. PP is often referred to as the "steel" of the plastics industry because additives can be added to PP or manufactured in a unique way to modify and customize PP to meet unique application requirements.

PP for general industrial use is a homopolymer. Block copolymer PP, is to add ethylene to improve the impact resistance. The random copolymer PP is used to make a more ductile, transparent product.

　　How is PP manufactured?

As with other plastics, starting from the "fraction" (lighter radicals) formed by the distillation of hydrocarbon fuels, combined with other catalysts, the plastics are formed by polymerization or polycondensation reactions.