The most essential difference between plastics and rubber is that plastic deforms when plastic deforms, while rubber deforms elastically. In other words, plastic is not easy to restore its original state after deformation, while rubber is relatively much easier. The elasticity of plastics is very small, usually less than 100%, while rubber can reach 1000% or more. Most plastic molding processes are completed, and the product process is also completed; After the rubber molding process is completed, a vulcanization process is also required.
"Plastics and rubber are both high molecular materials, mainly composed of carbon and hydrogen atoms, and some contain small amounts of oxygen, nitrogen, chlorine, silicon, fluorine, sulfur, and other atoms. Their properties and uses are special. At room temperature, plastics are solid, very hard, and cannot be stretched or deformed. Rubber has low hardness, elasticity, and can be stretched and lengthened.", "Stopping stretching can restore the original state. This is due to their different molecular structures. Another difference is that plastics can be recycled and reused multiple times, while rubber cannot be directly recycled. It can only be processed into recycled rubber before it can be used. The morphology of plastics at temperatures between 100 and 200 degrees is similar to that of rubber at temperatures between 60 and 100 degrees. Plastics do not include rubber."
Complex statement:
Broadly speaking, rubber is actually a type of plastic, including rubber. Here is a detailed introduction
1、 Formation of raw rubber:
Raw rubber can be divided into two categories: natural rubber and synthetic rubber:
Natural rubber: Raw rubber material formed by cutting the trunk of a rubber tree and collecting the outflow of rubber slurry through processing procedures such as impurity removal, solidification, fumigation, and drying.
Synthetic rubber: A by-product produced by the petrochemical industry, raw rubber materials with different physical properties are synthesized according to different needs. Common examples include: SBR, NBR, EPDM, BR, IIR, CR, Q, FKM, etc. However, due to differences in synthesis methods, the same type of rubber can be divided into several different types of raw rubber, and through formula settings, any type of rubber can be changed into thousands of raw rubber that meet the requirements of the product.
Natural rubber comes from tropical and subtropical rubber trees. Because rubber plays an important role in the fields of industry, agriculture, and national defense, it is an important strategic material, prompting countries lacking rubber resources to take the lead in researching and developing synthetic rubber.
2、 Chemical composition of rubber
By analyzing the chemical composition of natural rubber, it was found that its basic composition was isoprene. Therefore, people were inspired to use isoprene as a monomer for polymerization reaction to obtain synthetic rubber, known as isoprene rubber. The structure and properties of isoprene rubber are basically the same as those of natural rubber. At that time, isoprene could only be obtained from turpentine, and the source of raw materials was limited, while butadiene was abundant. Therefore, a series of synthetic rubbers based on butadiene were developed. Such as cis-1,4-polybutadiene rubber, styrene butadiene rubber, nitrile rubber, chloroprene rubber, etc.
With the development of the petrochemical industry, various gases such as ethylene, propylene, butene, isobutylene, butane, pentene, and isopentene can be obtained from oilfield gas and refinery gas through high-temperature cracking and separation and purification. They are good raw materials for manufacturing synthetic rubber.
In the world's rubber production, natural rubber accounts for only about 15%, while the rest is synthetic rubber. There are many varieties of synthetic rubber with various properties, which can replace or even exceed natural rubber in many occasions. Synthetic rubber can be divided into general rubber and special rubber. The amount of general rubber used is large, for example, styrene butadiene rubber accounts for 60% of the production of synthetic rubber; Followed by cis-1,4-polybutadiene rubber, accounting for 15%; In addition, there are isoprene rubber, neoprene, sodium butadiene rubber, ethylene-propylene rubber, butyl rubber, etc., which are all general-purpose rubbers.
3、 Preparation of rubber raw materials:
The preparation of rubber raw materials can be divided into three basic processes:
1. Plasticizing: Plasticizing refers to the mixing operation of cutting raw rubber, plasticizing and homogenizing raw rubber, and assisting in the mixing of ingredients. The effect is to improve the dispersion of drugs, prevent friction heat generated during operation, which can cause scorching of the rubber, thereby changing the processability of the rubber.
2. Mixing: Mixing refers to uniformly mixing mixed drugs into the finished raw rubber, and the quality of mixing directly affects the quality of the product. The drug is unevenly dispersed, the molecular structure cannot be fully crosslinked, and rubber cannot achieve ideal physical properties.
Press out: After the mixing of raw rubber, the excess air contained in the rubber is pressed out and the required thickness is completed to facilitate the molding operation in the mold.
4、 Rubber molding:
The molecular structure of raw rubber is an elastomer with unsaturated long bonds, so it is necessary to have appropriate pharmaceutical additives and external environmental factors (such as time, temperature, pressure, etc.) in the molding process to destroy its unsaturated bonds, then recombine them into saturated bonds, and use vacuum assistance to completely force out the contained air. In this way, the molded rubber can exert its due characteristics. If there are any defects in its molding process (such as formula errors, insufficient time, improper temperature, etc.), it can cause physical property loss, excess drug release, deformation, accelerated aging, and various serious adverse phenomena.
5、 Aging phenomenon of rubber:
According to the environmental conditions of the finished rubber product, over time, it causes cracking or hardening, and degradation of rubber physical properties, which is called aging phenomenon. The causes of aging include external and internal factors:
External factors: External factors include oxygen, oxides, ozone, heat, light, radiation, mechanical fatigue, lack of processing, etc.
Internal factors: Internal factors include the type of rubber, molding method, degree of bonding, type of compatible drugs, factors in processing engineering, etc.
The prevention of aging phenomena focuses on the correct selection of rubber species and formulation design, coupled with a rigorous production philosophy. In this way, the service life of rubber products can be increased and their special functions can be brought into play.
6、 Basic characteristics of rubber products:
When rubber products are molded, they are pressed under high pressure, and due to the inherent cohesion provided by the elastomer, they cannot be eliminated. During molding and demolding, they often produce extremely unstable shrinkage (the shrinkage rate of rubber varies depending on the type of rubber). It must take some time before they can be gentle and stable. Therefore, at the beginning of a rubber product design, regardless of the formula or mold, it is necessary to carefully calculate the fit. If not, it is easy to cause product size instability, resulting in low product quality.
Rubber is a thermoplastic elastomer, while plastic is a thermosetting elastomer. Due to the different types and main bodies of sulfides, the temperature range of rubber molding and curing also varies considerably, and can even be affected by climate change and indoor temperature and humidity. Therefore, the production conditions of rubber finished products need to be adjusted appropriately at any time. If not, there may be differences in product quality.
7、 Double sided adhesive for rubber bonding:
General industrial double-sided adhesive can be divided into two categories: acrylic adhesive and rubber adhesive. Both of these two categories can be divided into two types: base material and non base material (with base material: adding a layer of cotton to the adhesive to enhance the amount and strength of the double-sided adhesive itself; without base material: pure gum to ensure the transparency of the double-sided adhesive). The main body of the rubber system is CR, which is used for rubber products and is easily reacted with the vulcanization system of rubber to turn yellow. Therefore, lighter colored rubber products are all made of double-sided adhesive with a base material in the acrylic adhesive system (the same type of double-sided adhesive, whether with or without a base material, is distinguished by its own gum thickness.
Reference: China Engineering Rubber Network
The components of plastic include the following:
Plastics can be divided into single component and multi component. Single component plastics contain only the synthetic resins essential to plastics. For example, plexiglass is made of a single component of polymethyl methacrylate plastic, and most plastics include fillers, hardeners, colorants, and other additives in addition to synthetic resins. This is called multicomponent plastics.
1. Synthetic resin
Synthetic resins are almost always used in plastics. Resin is the most important component in plastics, which acts as an adhesive and can bond other components of plastics into a whole. Although adding various additives can change the properties of plastics, resin is a fundamental factor in determining the type, performance, and use of plastics.
The commonly used resin types in plastic decorative materials include:
Polyethylene (PE), polyvinyl chloride (PVC), polystyrene (PS), phenolic aldehyde (PF), urea formaldehyde (UF), epoxy (EP), polyester (PR), polyurethane (PU), polymethyl methacrylate (PUMA), organic silicon (SI), etc.
According to the changes that occur when heated, synthetic resins can be divided into thermoplastic resins and thermosetting resins.
(1) Thermoplastic resin: It has the properties of softening by heating and hardening by cooling, and does not react chemically. It can maintain this property no matter how many times heating and cooling are repeated. The molecular structure of any thermoplastic resin is linear. It includes both fully polymerized resins and partially condensed resins. Thermoplastic resins include: polyethylene, polyvinyl chloride, polystyrene, polyamide, polyformaldehyde, polycarbonate, polyphenylene ether, polysulfone, rubber, etc. The advantage of thermoplastic resins is that they are easy to process and have high mechanical energy. The disadvantage is poor heat resistance and rigidity.
(2) Thermosetting resin: After heating, the resin undergoes chemical changes and gradually hardens to form. When heated, it does not soften or dissolve. The molecular structure of thermosetting resins is body type, which includes most condensation resins. The advantages of thermosetting resins are high heat resistance and resistance to deformation under pressure. Its disadvantage is poor mechanical performance. Thermosetting resins include phenolic, epoxy, amino, unsaturated polyester, and silicone ether resins.
2. Filler
Fillers can improve and enhance the properties of plastics. For example, adding fibers can improve the mechanical strength of plastics; Adding asbestos can enhance the heat resistance of plastics; Adding mica can enhance the electrical insulation properties of plastics; Adding graphite and molybdenum disulfide can improve the friction and wear resistance of plastics. Adding fillers can also reduce the cost of plastics.
3. Plasticizer
Adding plasticizers to plastics can improve their plasticity and softness, and reduce their brittleness. Common plasticizers include dibutyl phthalate, dioctyl phthalate, trimethyl phosphate, camphor, benzophenone, etc.
4. Hardener
Hardener is also known as a curing agent or curing agent. Its main function is to cross-link the linear molecular structure of the polymer into a body type molecular structure, thereby making the resin thermosetting. The commonly used hardener in phenolic resins is urotropine (hexamethylene tetramine). The commonly used hardeners for epoxy resins include amines and anhydrides.
5. Colorant
Adding colorants to plastics can give them bright colors and luster. Colorants often use various pigments and dyes, and sometimes pigments that produce fluorescence or phosphorescence are also used.
6. Stabilizer
Many plastics undergo premature degradation, oxidative chain breakage, cross-linking, and other phenomena due to the effects of heat, light, or oxygen during molding and product use, resulting in deterioration of material properties. In order to stabilize the quality of plastic products and extend their service life, stabilizers are usually added to their components. Common stabilizers include stearates, lead whites, epoxides, and so on.
7. Other additives
During plastic processing, lubricants are often needed in order to release mold and make products smooth and clean. The commonly used lubricants include fatty acids and their salts. In order to make plastic products such as plastic flooring and plastic mats antistatic, antistatic agents are added to improve surface conductivity and rapidly discharge charged plastic.
In order to improve the performance of plastic products to meet various usage requirements, there are also antioxidants, ultraviolet absorbers, flame retardants, foaming agents, luminescent agents, balm, etc.
2. Classification of plastics:
The classification system of plastics is relatively complex, and various classification methods also intersect. According to conventional classification, there are mainly three types: first, classification by use characteristics; Classification according to physical and chemical characteristics; The third is classification by processing method.
1. Classification by usage characteristics
According to the different use characteristics of well-known plastics, plastics are generally divided into three types: general purpose plastics, engineering plastics, and special plastics.
2. Classification by physical and chemical characteristics
According to the different physical and chemical properties of various plastics, plastics can be divided into two types: thermosetting plastics and thermoplastics.
3. Classification by processing method
According to different molding methods of various plastics, they can be divided into various types, such as film pressing, laminating, injection, extrusion, blow molding, casting plastics, and reaction injection plastics
Daihata is a leading brand manufacturer of water chillers and mold warmers. Taiwan Dahota is a modern high-tech enterprise specializing in the production of industrial refrigeration equipment, industrial temperature control equipment, and plastic machinery peripheral equipment. With more than ten years of experience in research and development, production, sales, and service, continuous improvement and improvement of product quality, adhering to Taiwan's philosophy, Japanese and European technology, and integrating modern management, production and operation are orderly, and products are constantly innovative; In order to meet customer needs, while investing a large amount of funds, we have continuously strengthened talent training and production technology improvement, and achieved a professional image with advanced technical quality and rigorous control system, laying a solid foundation for Dahetian's first-class products.