Introduction to Plastics

Plastics are a class of materials consisting of a variety of synthetic or semi-synthetic organic compounds that are ductile and can therefore be molded into solid objects. Plasticity is a universal property of all materials, i.e. the ability to deform permanently without breaking. Polymers get their name from their elasticity and plasticity.

Plastics are usually high molecular weight organic polymers, but often contain other substances as well. They are usually synthetic, with the most common source being petrochemicals. However, with today’s environmental concerns, more and more plastics are derived from renewable materials, such as polylactic acid from corn or cellulose from cotton lint.

Due to their relatively low cost, ease of manufacture, versatility, and waterproofness, the range of applications for plastics has continued to expand. From simple paper clips to complex aircraft, plastics are everywhere.

Plastic materials come in a wide variety of forms and are used in a wide range of manufacturing applications. 3D printing is one of the newest and most exciting areas of manufacturing. New applications for 3D printing emerge almost every day, and a wide variety of plastic products have been produced using the 3D printing process. These items are mainly used in prototype labs, toys, mechanical gearboxes, medical prostheses, and more.

Plastic Classification

Plastics can be divided into two categories according to their own properties: thermoplastics that can be repeatedly melt-molded and basically maintain their characteristics, and thermosetting plastics that can only be melt-molded once. According to their uses, they can be divided into widely used and cheap.

General plastics with good comprehensive performance, such as PE, PP, PVC, PS, and amino plastics have good physical and mechanical strength, and may replace metals in engineering machinery. Engineering plastics such as: ABS, nylon, polyester, POM, TPX-1, etc. And a class of engineering plastics with particularly excellent properties, such as: special plastics with particularly good radiation resistance, high temperature resistance, etc., such as: polyaryl sulfone, liquid crystal polymer, etc. According to the size of the crystallization of thermoplastic resin molecules, thermoplastics can be divided into two categories: amorphous polymers and crystalline polymers.

Main Characteristics

The main characteristics of plastics are:
First, low density and high specific strength can achieve a higher packaging yield, that is, “the packaging volume or packaging area per unit mass.”

Second, most plastics have good chemical resistance, good acid resistance, alkali resistance, resistance to various organic solvents, and no oxidation after long-term storage.

Third, easy molding, the required molding energy consumption is lower than that of metal materials such as steel.

Fourth, good transparency and easy coloring.

Fifth, good strength, high strength per unit weight, impact resistance, and easy modification.

Sixth, low processing cost.

Seventh, excellent insulation.

Development of the packaging industry

In the synthesis, 25% is used in the packaging industry, so it is an important sector in the plastic packaging industry. Plastic packaging is one of the four major materials in the packaging industry: paper and paperboard account for 30%, plastic accounts for 25%, metal accounts for 25%, and glass accounts for 15%. The above two 25% fully illustrate the importance of the plastic packaging industry. Although the plastic packaging industry is the second packaging material, its actual application is not as good as paper and paperboard packaging. However, the plastic packaging industry is developing at a rate of 5% per year, while other packaging materials, including paper and paperboard, metal, glass, ceramics, hemp and cotton, are only growing at a rate of 2%. Therefore, one day the plastic packaging industry will surpass paper and paperboard and become the first packaging material.

In terms of the total volume of the packaging industry, China is already a packaging power, but not a packaging power, which is manifested in the fact that the independent innovation ability of enterprises is still weak, the added value of products is low, and the value of packaging is not fully reflected in the industrial chain. Low-level duplicate construction has led to a prominent contradiction between the overcapacity of low-end products and the insufficient supply of high-end products, and lack of stamina for development. China’s packaging industry needs to shift from relying solely on quantitative growth and expanding production capacity to relying on scientific and technological innovation, technological progress, and optimizing and adjusting structure to enhance the core competitiveness of industrial development.

In terms of packaging containers

In terms of packaging containers, the original containers for packaging beverages were glass bottles, followed by paper composite cans, and then PET bottles. Now, rigid PET bottles have become the largest packaging material for carbonated and non-carbonated beverages. In the United States in 1991, they accounted for 26.5% of beverage packaging containers. Glass bottles have dropped from 28.9% in 1981 to 19.5%, and aluminum cans account for 39%.

Moreover, plastic bottles are growing rapidly at an annual growth rate of more than 3%. It is certain that even in countries where the plastic packaging industry is most criticized. Plastics will continue to develop at a much faster speed than other packaging materials, because many of the characteristics of plastics cannot be replaced by any other packaging material. While occupying the sales packaging field, the plastic packaging industry has developed into transportation packaging, and will eventually force the “transportation packaging” that is still mainly metal to be replaced by plastic.

Classification and characteristics

Plastic packaging bags can be divided into OPP, CPP, PP, PE, PVA, EVA, composite bags, co-extruded bags, etc. according to the material.

OPP plastic bag:
Characteristics: hard, unchanged after pulling. Unstretchable (two-way stretching), single piece folded in half, edge seal welding, the longest length cannot exceed 640m/m. Single piece length 1.28M, width 0.6M.
Advantages: good transparency.
Disadvantages: easy to tear at the seals on both sides.

PP plastic bag: Polypropylene
Characteristics: hardness is inferior to OPP, stretchable (two-way stretching), stretched into a triangle, bottom seal or edge seal (envelope bag), tube material. Transparency is worse than OPP.
PE plastic bag: Polyethylene
Characteristics: contains formalin, slightly poor transparency.

HDPE: High-density low-pressure polyethylene High-density polyethylene feels brittle and is mostly used to make vest bags.

LDPE: Low-density high-pressure polyethylene Low-density polyethylene feels soft.

PVA plastic bag: Vinylon
Features: Environmentally friendly material, will dissolve in water. This raw material cannot be produced in China, it is imported from Japan, expensive, and widely used abroad.
Advantages: soft, good transparency, pollution-free.

CPP plastic bag:
Features: non-toxic, compoundable, better transparency than PE, slightly worse hardness. It will grow out after pulling, soft texture, with the transparency of PP and the softness of PE.

Composite bag:
Features: strong edge seal strength, printable, ink will not fall off.
Co-extrusion bag:
Features: good transparency, soft texture, printable.

Plastic Blister

Blister
A plastic processing technology, the main principle is to heat and soften the flat plastic hard sheet, vacuum absorb it on the mold surface, and form it after cooling. It is widely used in plastic packaging, lighting, advertising, decoration and other industries.

Blister packaging
The general term for plastic products produced by blister technology and packaged with corresponding equipment.

Features
The main advantages of blister packaging are saving raw and auxiliary materials, light weight, convenient transportation, good sealing performance, and meeting the requirements of environmentally friendly green packaging; it can package any special-shaped products, and no additional cushioning materials are required for packaging; the packaged products are transparent and visible, beautiful in appearance, easy to sell, and suitable for mechanized and automated packaging, which is convenient for modern management, saving manpower, and improving efficiency.

PPO Plastic

Concept
PPO plastic, Chinese name is polyphenylene ether. It has the advantages of high rigidity, high heat resistance, flame retardancy, high strength and excellent electrical properties. In addition, polyphenylene ether also has the advantages of wear resistance, non-toxicity and pollution resistance. The dielectric constant and dielectric loss of PPO are one of the smallest varieties among engineering plastics. It is almost unaffected by temperature and humidity and can be used in low, medium and high frequency electric fields. The load deformation temperature of PPO can reach above 190℃ and the brittle temperature is -170℃.

Pure PPO material has the disadvantages of poor melt fluidity and high price. The products sold on the market are all improved products with excellent comprehensive performance.

Application
PPO plastic is widely used in: Electronics and electrical: It can meet the requirements of excellent electrical insulation under humid, load and high temperature conditions. It is used to prepare TV tuners, coil cores, microwave insulation parts, shielding sleeves, high-frequency printed circuit boards, various high-voltage electronic components, TV, computer, fax machine, copier shells, etc.
Automotive industry: Applicable to instrument panels, window frames, shock absorbers, pump filters, etc.
Mechanical industry: Used as gears, bearings, pump impellers, blower impellers, etc.
Chemical industry: Used to make corrosion-resistant parts such as pipes, valves, filters and submersible pumps.