What Are Thermoplastic Materials?

Thermoplastics are a class of plastics that are malleable at a certain temperature, solidify after cooling, and can repeat this process. The molecular structure is characterized by a linear polymer compound, which generally does not have active groups, and does not undergo linear intermolecular cross-linking when heated. After the waste products are recycled, they can be reprocessed into new products. The main varieties are polyolefins (vinyl, olefins, styrenes, acrylates, fluoroolefins, etc.), celluloses, polyether polyesters, and Aromatic heterocyclic polymers. ^[1]

Thermoplastic is the most widely used type of plastic. It is made of thermoplastic resin with various main ingredients and various additives. Under certain temperature conditions, plastics can soften or

Thermoplastics can be divided into general-purpose plastics,

Thermoplastic Vulcanizate (English: Thermoplastic Vulcanizate), TPV for short, Chinese name for Thermoplastic Vulcanized Rubber (English Thermoplastic Rubber), TPR for short, but this name is easily confused with other types of thermoplastic elastomers (English: Thermoplastic Elastomer) Together because usually thermoplastic elastomers are also called thermoplastic rubbers, especially

Thermoplastic Elastomer-TPE is also known as Thermoplastic Rubber-TPR. It is a material that has both rubber and thermoplastic properties. Thermoplastic elastomers have multiple possible structures. The most fundamental one is that at least Two mutually dispersed polymer phases. At normal use temperature, one phase is fluid (making the temperature higher than its Tg-glass transition temperature) and the other phase is solid (making the temperature lower than or equal to its Tg) , And there is an interaction between the two phases. That is, the polymer material that shows rubber elasticity at normal temperature and can be plasticized at high temperature has mechanical properties and use properties similar to rubber, and can be processed and recycled as a thermoplastic. It stands between plastic and rubber. A bridge. As a result, thermoplastic elastomers can process rubber products as quickly, efficiently, and economically as thermoplastics. In terms of processing, it is a plastic; in terms of nature, it is also a rubber. Thermoplastic elastomers have many advantages over thermoset rubbers. At present, there is no uniform name for thermoplastic elastomers. It is customary to use the English acronym TPR for thermoplastic rubber and TPE for thermoplastic elastomers, both of which are used in related materials. For the sake of uniformity, they are all called TPE or thermoplastic elastomer. At present, the domestic thermoplastic styrene-butadiene block copolymer is called SBS (styrene-butadiene-styren block copolymer), and the thermoplastic isoprene-styrene block copolymer is called SIS (styrene-isoprene block copolymer), saturated SBS is called SEBS, which is the abbreviation of Styrene-ethylene-butylene-styrene block copolymer, which is styrene-ethylene-butene-styrene block copolymer. Other types of thermoplastic elastomers are called by the manufacturer's trade name. China also uses the code of SBS, which means thermoplastic styrene-butadiene-styrene block copolymer, which is customarily called thermoplastic styrene-butadiene rubber. Elastomer is an artificial thermoplastic elastomer with unique properties and has a very wide range of uses. Its excellent product applicability comes from the adjustment and controllability of its special molecular structure, which shows the following excellent properties:

Excellent physical properties: good appearance and texture, mild touch, easy coloring, uniform color, stable; adjustable physical properties, providing broad product design space; mechanical properties comparable to vulcanized rubber, but without vulcanization and crosslinking; wide hardness range, from SHORE- A 0 degrees to SHORE-D70 degrees adjustable; excellent tensile resistance, tensile strength up to a dozen MPa, elongation at break up to ten times or more; long-term temperature resistance can exceed 70 , low temperature environmental performance Good, can still maintain good bending performance at -60 ; good electrical insulation and voltage resistance characteristics. Has outstanding anti-skid performance, abrasion resistance and weather resistance.

Excellent chemical properties: resistance to general chemicals (water, acid, alkali, alcohol solvents); can be processed in solvents, can be immersed in solvents or oils for a short time; non-toxic; good resistance to ultraviolet radiation and oxidation resistance, can be used Outdoor environment; Good bonding performance, suitable bonding technology can be directly bonded to genuine leather or artificial leather surface.

Production and processing advantages: it has the characteristics of traditional vulcanized rubber without vulcanization, and saves auxiliary materials such as vulcanizing agents and accelerators; suitable for various processes such as injection molding, die-casting, hot-melt and dissolving coating; Completely recycle and reuse without changing performance, reduce waste; simplify processing technology, save processing energy consumption and equipment resources, short processing cycle, reduce production cost, improve work efficiency; simple processing equipment and technology, save production space and reduce defective products The product is non-toxic, non-irritating odor, and harmless to the environment, equipment and personnel. The material can be used repeatedly, and the waste material can be recycled. It can be said that there is no waste material in production. There are fewer processing aids and additives, which can save the product. Expenses for quality control and testing; high dimensional accuracy and easier quality control; less material weight and adjustable; can be directly blended with PP, ABS and other plastics to make special plastic alloys.

Elastomers have superior physical and chemical properties and are easy to process. At the same time, the product also has the advantages of being non-toxic, pollution-free and recyclable for environmental protection. Therefore, it is widely used in many industrial fields, such as: toys, sports equipment, footwear, stationery, hardware, power tools, communications, electronics, food and beverage packaging, household appliances, kitchen supplies, medical equipment, automobiles, construction engineering , Wires and cables. What's more valuable is that she is a high-quality material leading new product design and market orientation. Its soft texture and adjustable physical properties, hardness, suitable for a variety of processing processes, and environmental protection advantages-provide a large number of product designers. The huge play space will undoubtedly help you to innovate products, increase value, and lead the market trend. ^[4]

The molecular weight of polymers in general thermoplastics can reach hundreds of thousands to millions, and the length of macromolecule chains can reach 10 ^-3 mm. These macromolecules can be linear, such as LLDPE, HDPE; they can also be branched, such as LDPE. Macromolecules are entangled with each other in a disorderly or relatively ordered arrangement, forming "

Plastics can be divided into two types, thermosetting and thermoplastic. The former cannot be reshaped, and the latter can be repeatedly produced.

Thermoplastic

It softens to flow when heated, and hardens when cooled. This process is reversible and can be repeated. Polyethylene, polypropylene, polyvinyl chloride, polystyrene, polyformaldehyde, polycarbonate,

Affects thermoplasticity

1. PP is the English abbreviation of Polypropylene, and the Chinese name is polypropylene. Advantages of polypropylene (PP):

1. It has excellent mechanical properties, its strength and elasticity are higher than HDPE, and its bending fatigue resistance is good.

2. It has good heat resistance, melting point is 164-170 ° C, the product can be sterilized and sterilized at a temperature above 100 ° C, the heat distortion temperature can usually reach 110 ° C, and the brittleness temperature is -35 ° C.

3. The chemical stability is very good, except that it can be attacked by concentrated sulfuric acid and concentrated nitric acid, it is relatively stable to other chemical reagents. 4. The high-frequency insulation performance of polypropylene is excellent. Because it hardly absorbs water, the insulation performance is not affected by temperature.

Disadvantages of polypropylene (PP):

1. The shrinkage is large, and the thick-walled products are easy to sag.

2. At low temperatures, the impact strength is poor.

3, high static electricity, easy to age in contact with copper.

4, very sensitive to ultraviolet rays.

Compared with pure PP, impact-resistant modified PP has the following advantages:

1. The impact strength, toughness and mechanical modulus are significantly improved. It can be seen from the performance table that the modified PP represents higher rigid tensile strength, bending strength and hardness than pure PP, and the impact strength representing toughness is also Improved, especially the low temperature brittleness of PP.

2. Reduce the shrinkage rate and effectively improve the warpage and deformation of the product.

3. Improve the aging resistance of PP and greatly increase the service life of the product.

HDPE is the English abbreviation of High Density Polyethylene, and its Chinese name is high density polyethylene. Advantages of high density polyethylene (HDPE):

1. Good impact resistance and cold resistance, resistance to environmental stress cracking.

2. Excellent chemical stability and good oil resistance.

3. Water absorption and tiny, low water permeability and large organic vapor transmission rate.

4. Good electrical insulation and excellent dielectric properties in all frequency ranges.

Disadvantages of high density polyethylene (HDPE):

1. The operating temperature of HDPE is not high, generally below 110 .

2. HDPE has poor aging resistance, and gradually becomes brittle under the action of the atmosphere, sunlight and oxygen, and the mechanical strength and electrical properties decrease.

3. At the molding temperature, due to oxidation, the viscosity will decrease, discoloration will occur, and stripes will occur.

3. ABS is the English abbreviation of Acrylonitrile Butadiene Styrene. The Chinese name is acrylic copolymer-butadiene-styrene copolymer. The advantages of acrylonitrile-butadiene-styrene copolymer (ABS):

1. Good rigidity, high impact strength, and will not decrease rapidly at low temperature.

2. Good heat resistance and low temperature resistance, high wear resistance, chemical resistance, and excellent electrical performance.

3, easy to process, processing dimensional stability.

4, good surface gloss, easy to paint, color, can also be sprayed metal, electroplating, welding and bonding secondary processing performance.

Disadvantages of acrylonitrile-butadiene-styrene copolymer (ABS):

1. ABS has strong hygroscopicity in air. It must be dried before injection molding, and the resin should be pre-dried at 70-80 ° C for more than 4h.

2. Poor weather resistance. ^[2]