What is Polypropylene?
Polypropylene (PP for short) is a semi-crystalline thermoplastic polymer made from propylene monomers through addition polymerization. It is usually a white waxy solid, non-toxic, odorless, transparent in appearance and light in texture. Its chemical formula is (C3H6)n, and its density is 0.89-0.92 g/cm3, making it the thermoplastic resin with the lowest density; its melting point is 164-176 °C, softening at around 155 °C, and its operating temperature range is -30-140 °C.
Polypropylene has the characteristics of being light, wear-resistant, antibacterial and easy to dye, and is widely used in fiber products such as clothing and blankets; it has good insulation properties and is used to manufacture housings and parts of refrigerators, washing machines, air conditioners, and televisions; it has good chemical stability, heat resistance, transparency and mechanical properties, and is used to manufacture medical devices; it has good corrosion resistance, weather resistance and plasticity, and is used to manufacture construction and building materials products.
What are PP plastics used for?
The properties of polypropylene (PP) make it suitable for use in a wide range of industries. This plastic has excellent chemical resistance and a very high melting point (around -10°C), which means it can withstand steam sterilization, effectively killing bacteria, fungi and parasites. This makes it ideal for medical applications, medical devices, the food container industry, and applications that require heat resistance.
Due to its lightweight and flexible properties, PP is used throughout the automotive industry to make car dashboards, bumpers, cladding and exterior trim, as well as interior components.
In the packaging sector, it has a wide range of applications, some of which you may not be aware of. Due to its low price and superior performance, flexible packaging has replaced cellophane, metal and paper. As a result, you will find it used as film and soft packaging for tobacco, clothing, food and confectionery.
Disadvantages of polypropylene
In terms of the wider environment and global resource conservation, a key disadvantage of polypropylene is that it is not easily recyclable. When burned, it undergoes an irreversible chemical change. If you try to reheat polypropylene that has already been melted and formed, it will simply burn and will not liquefy again. Therefore, other methods of recycling or reprocessing must be considered, and the costs will increase significantly.
The low melting point also means that polypropylene is extremely flammable, has limited resistance to high temperatures, and is susceptible to UV degradation and oxidation. In addition, while the glossy appearance of polypropylene makes it beautiful and easy to handle, this property also makes it difficult to bond to other surfaces and materials, such as paints and glues. When using polypropylene to make joints or hinges, alternative bonding methods such as welding must be used.
What is PP plastic around us?
PP plastic is common in all aspects of daily life due to its versatility and superior performance. Some common uses of PP plastic include:
A. Packaging: PP is widely used to package items such as food containers, beverage caps, and medicine bottles due to its excellent moisture and chemical resistance.
B. Textiles: PP fibers are used to make non-woven fabrics for items such as reusable shopping bags, masks, and disposable clothing.
C. Automotive: PP plastic is used in automotive parts such as bumpers, interiors, and battery casings due to its strength and impact resistance.
D. Medical devices: It is used to produce medical devices such as syringes and test tubes due to its purity and sterilizability.
E. Household products: PP is used in a variety of household items such as storage containers, kitchenware, and furniture due to its durability and easy cleaning.
F. Industrial applications: Due to its chemical resistance, PP plastic is used in items such as chemical tanks, pipes, and industrial packaging in industrial environments.
G. Construction: PP pipes are used for plumbing and drainage systems in buildings, and PP sheets are used for signs and displays.
H. Stationery: Items such as folders, binders, and plastic sheet protectors are often made of PP because it is durable.
PP plastic is valued for its balance of cost-effectiveness, durability, and chemical resistance, making it suitable for a wide range of products and industries.
PP Recycling
A: Waste PP recycling technology
Polypropylene (PP) is currently the second largest general-purpose plastic. With the development of industries such as construction, automobiles, home appliances and packaging, waste PP has become one of the waste polymer materials with the largest output in recent years. At present, the main ways to deal with waste PP are: incineration for energy supply, catalytic cracking to prepare fuel, direct utilization and recycling. Considering the technical feasibility, cost, energy consumption and environmental protection in the process of treating waste PP, recycling is currently the most commonly used, effective and most advocated way to treat waste PP.
B: Recycled materials
With the rise in global crude oil prices, the price of plastic products, as one of the petroleum derivatives, has naturally risen, and the recycling of waste plastics has also been put in the first place. The recycling and reuse of waste plastics has been widely adopted by modern chemical companies. After manual screening and classification, waste plastics must also go through processes such as crushing, granulation, and modification to become various transparent and opaque plastic particles, and then be classified according to the appearance, and finally become recycled materials that can be reused.
C: Fuel
Initially, plastic recycling used landfill or incineration methods in large quantities, resulting in huge waste of resources. Therefore, foreign countries use blast furnace injection to replace coal, oil and coke, use cement rotary kilns to replace coal to burn cement, and make solid waste fuel (RDF) for power generation, with ideal results.
D: Power generation
Waste solid fuel power generation was first applied in the United States, and there are 37 RDF power plants, accounting for 21.6% of waste power plants. Japan has realized the huge potential of waste plastic power generation. In conjunction with overhaul, Japan has converted some small waste incineration plants into RDF production plants so that they can be concentrated for continuous and efficient large-scale power generation, increasing the steam parameters of waste power plants from 30012 to about 45012, and the power generation efficiency from the original 15% to 20%-25%.
E: Degradable and recyclable
Degradable plastics can be decomposed in the sun. Starch is also added to plastics to make them easier to biodegrade, but the decomposition is still incomplete. Some people even use genetically modified bacteria to produce completely biodegradable plastics, but the cost is still high. BASF of Germany has developed a biodegradable plastic called Ecoflex for food packaging. The above degradable plastics are rarely used due to cost issues. And this kind of plastic must be exposed to air to decompose, so if it is landfilled, it will still cause solid waste problems.
