The shining stars of the plastic world: the legendary journey of PE, PET, TPE and TPU

Have you ever been curious about the plastic products in our daily lives and how they were born? Next, we will take you to the four kings of the plastic world: polyethylene (PE), polyethylene terephthalate (PET), thermoplastic elastomer (TPE) and thermoplastic polyurethane (TPU). These materials not only contain their own legendary stories, but also have amazing unique properties. Let us embark on this unique exploration journey together and unveil their mysteries one by one.

 

The first to appear is polyethylene (PE), which occupies a pivotal position in the plastic world and is known as the leader in the plastic world.

Let's go back to 1922, when polyethylene (PE) was synthesized for the first time, opening a new chapter in the plastic world. In 1933, the important discovery of British scientists-ethylene can be polymerized into PE under high pressure, paved the way for the industrial production of PE, thus profoundly changing our daily lives.

 

PE stands out for its outstanding versatility and adaptability. It can be flexible and hard, transparent or opaque, depending on the needs. Its refractive index ranges from 46 to 50, making it a natural choice for the world of light, from transparent food packaging to sturdy pipes. Its applications are extremely wide, from the plastic bags we use every day to children's toys to complex cable and pipe systems. Its excellent flexibility and durability have won the favor of engineers and designers.

 

In addition, PE has many types. Depending on the polymerization method, molecular weight and chain structure, PE can be divided into high-density polyethylene (HDPE), low-density polyethylene (LDPE), linear low-density polyethylene (LLDPE) and ultra-high molecular weight polyethylene (UHMWPE). Different types of PE have their own advantages in performance and use.

 

At the same time, PE has unique optical properties. Its optical performance indicators such as transparency, refractive index and light transmittance vary due to differences in density and molecular weight. For example, LDPE has a high transparency, while HDPE and LLDPE have a relatively low transparency. In addition, PE has a weak resistance to ultraviolet rays, so in practical applications, it is necessary to add anti-ultraviolet agents to improve its weather resistance.

 

Finally, let's take a look at the production process of PE. It mainly includes polymerization, melt extrusion, cooling and shaping, and post-processing. The fine control of these process links ensures that the quality and performance of PE products meet expectations.
Polymerization is a key step in PE production, and different processes such as high-pressure method, low-pressure method and gas phase method can be used. The high-pressure method is mainly suitable for the production of LDPE, while the low-pressure method and gas phase method are used for the manufacture of HDPE and LLDPE. In the melt extrusion stage, PE resin is heated to a molten state and then extruded into a specific shape through a die. After cooling and shaping, the extruded molten material is quickly solidified and formed. Finally, through post-processing such as cutting and winding, we get the finished PE film or molded parts.

 

Due to its excellent versatility and adaptability, PE plays an important role in many industries. In the packaging industry, PE is widely used in the manufacture of food packaging bags, shopping bags and agricultural covering films. At the same time, it is also an important player in the field of building materials, such as the production of pipes, cable insulation and waterproof materials. In addition, the consumer goods industry, such as toys, containers and daily necessities, also cannot do without the application of PE. The same is true in the automotive industry, where PE is used in the manufacture of fuel tanks, pipes and interior parts.

 

However, it is worth noting that although polyethylene (PE) excels in many aspects, another polymer, polyethylene terephthalate (PET), is gradually emerging. This environmentally friendly material is gradually becoming a new favorite in the market with its unique properties and sustainability.

Jump to 1941, when British scientists invented polyethylene terephthalate (PET). This material quickly became an ideal choice for fibers and containers due to its high transparency and excellent heat resistance. At the same time, its environmentally friendly characteristics also make it a model for recycling.

According to different uses and properties, PET can be divided into several categories: fiber-grade PET is used for the manufacture of synthetic fibers such as polyester, bottle-grade PET is used for the production of beverage bottles and other containers, and film-grade PET is suitable for the manufacture of films such as food packaging and protective films for electronic products. In addition, engineering-grade PET is used as an engineering plastic and is widely used in the manufacture of electronic and electrical components, automotive parts, etc.

 

PET has a refractive index of 636, which gives it excellent transparency and gloss, making it very suitable for the manufacture of transparent packaging and films. Its light transmittance of up to 90% and low haze characteristics provide clear and beautiful visual effects. At the same time, PET also has good chemical resistance and can withstand most chemicals, including acids and alkalis, but it should be noted that it may be hydrolyzed by alkali at high temperatures.

 

The production process of PET covers multiple links such as polymerization reaction, melt extrusion, cooling and shaping, and post-processing. Among them, the polymerization reaction can use the ester exchange method or direct esterification method to convert the raw material into PET resin. Subsequently, the resin is heated to a molten state by melt extrusion and extruded through a mold. After the cooling and shaping link, the extruded molten material is rapidly solidified. Finally, after post-processing steps such as cutting and winding, the finished PET film or bottle blank can be obtained.

 

PET has a wide range of applications, covering packaging, building materials, consumer goods and the automotive industry. Its environmentally friendly characteristics make it popular in the market and become a representative of sustainable development.
Textile industry: Polyethylene terephthalate (PET) can be spun into polyester fibers, which play a key role in the manufacture of textiles such as clothing, curtains and carpets.

 

Electronics and electrical appliances: PET materials are also widely used in the field of electronic equipment. They are often used to manufacture electronic equipment components and electrical product housings to ensure the durability and aesthetics of the equipment.

Automotive industry: The automotive manufacturing industry is also inseparable from PET. This material is often used to produce automotive parts, such as switchboard covers and ignition coils, providing strong support for the performance and safety of the car.

Thermoplastic elastomer (TPE): Soft guardian

Thermoplastic elastomer (TPE) plays a protective role in many fields with its soft characteristics. This material is not only easy to process and shape, but also has excellent physical properties. It is widely used in seals, pipes, wires and cables, etc., to ensure the durability and safety of products.

 

The birth of TPE has undoubtedly promoted the development of materials science. This material, which combines the softness of rubber with the convenience of plastic processing, has opened a new era of soft product manufacturing since it was first introduced by DuPont in Canada in the 1960s.

 

TPE, as a block copolymer composed of hard segments and soft segments, has unique properties due to the clever combination of the two. Hard segments are usually based on polymers with higher glass transition temperatures. They act as physical crosslinking points in the material, providing TPE with the necessary strength and processing performance. The soft segments, on the other hand, are composed of polymers with lower glass transition temperatures, giving TPE excellent elasticity and flexibility.

 

According to the specific composition of the soft and hard segments, TPE can be divided into many types, such as polystyrene TPE (TPS), polyolefin TPE (TPO), polyester TPE (TPEE) and polyurethane TPE (TPU). These different types of TPE play a unique role in their respective fields.

 

In addition, TPE also has excellent optical properties. It has good light transmittance, low haze, and excellent touch and visual effects. These characteristics make TPE shine in the manufacture of transparent or translucent products. At the same time, the simple production process and the characteristics of not requiring vulcanization make TPE unique in the field of plastic processing.

Injection molding: This is the most commonly used processing method for TPE, especially for the manufacture of parts with complex shapes. Its injection molding cycle is short and the production efficiency is extremely high.

 

Extrusion molding: This method is very suitable for the production of continuous-shaped products such as profiles, pipes, and films. TPE extrusion molding can quickly produce long-length products.

Blow molding: Mainly used to manufacture hollow products such as bottles and containers. TPE blow molding technology can ensure uniform wall thickness of the product.

 

TPE has a wide range of applications, covering:

• Automotive industry: used to manufacture automotive interior parts, sealing strips, and shock-absorbing components, etc.
• Medical industry: Due to its biocompatibility and non-toxicity, TPE is widely used in the manufacture of medical devices, such as infusion sets, blood bags, etc.
• Consumer electronics: Such as mobile phone cases, computer keyboards, and headphone cables, all use TPE materials.
• Toy industry: TPE is widely used in the manufacture of children's toys because of its soft and safe characteristics.
• Sports equipment: TPE is also used to make sports shoe soles, sports equipment grips, etc., providing athletes with excellent elasticity and grip.

 

TPU, a material first synthesized by German scientists in the 1950s, perfectly combines the elasticity of rubber and the thermoplasticity of plastic, making it an ideal choice for outdoor sports equipment and industrial applications. Its unique molecular structure, composed of hard segments and soft segments, gives TPU excellent physical properties. The soft segment, as a flexible segment, mainly affects the elasticity and low temperature resistance of the material, while the hard segment, as a rigid segment, plays a key role in the hardness, heat resistance and mechanical strength of the material.

 

According to the difference between the soft segment and the hard segment, TPU can be further divided into polyester type, polyether type and polycaprolactone type. Polyester type TPU stands out for its excellent wear resistance and mechanical properties, while polyether type TPU is favored for its excellent hydrolysis resistance and low temperature resistance. Polycaprolactone type TPU cleverly combines the advantages of both, showing excellent hydrolysis resistance, low temperature resistance and excellent elasticity.

 

In addition, TPU also has excellent optical properties, including good light transmittance, low haze and moderate refractive index. Its high transparency makes TPU shine in the manufacture of transparent or translucent products. At the same time, the simple production process and wide applicability also make TPU a powerful assistant in industrial production and daily life. Whether it is injection molding, extrusion molding or blow molding, TPU can easily cope with it and quickly produce products that meet various needs.

Because TPU perfectly combines the elasticity of rubber and the thermoplasticity of plastic, its application field is extremely wide. In terms of shoe materials, TPU is often used to make logos and air cushions for sports shoes, as well as mountaineering shoes and snowshoes. At the same time, it is also widely used in the field of clothing, such as composite materials for snow suits, raincoats, windbreakers and cold-proof jackets. In addition, TPU also has important applications in many fields such as medical, national defense, sports goods and industrial supplies. For example, in the medical field, it is used to make surgical gowns, caps, shoes, hospital mattresses and ice packs; in defense products, TPU is used to produce aircraft fuel tanks, weapons sealing films and tent windows. Its excellent physical properties and simple production process make TPU a powerful assistant in various industries, bringing more convenience and possibilities to our lives.