How to distinguish between thermoplastic and thermoset, the difference between thermoplastic and the

1. Thermoplastics.

When heated, it softens to the point of flowing, and cooling becomes hard, a process that is reversible and can be repeated. Polyethylene, polypropylene, polyvinyl chloride, polystyrene, polyoxymethylene, polycarbonate, polyamide, acrylic plastics, other polyolefs and their copolymers, polyirony, polyphenylene ether, chlorinated polyether, etc. are all thermoplastics. The resin molecular chains in thermoplastics are all linear or branched structures, and there are no chemical bonds between the molecular chains, and the process of softening and flowing when heated and cooling and hardening is a physical change.

2. Thermosetting plastics.

When heated for the first time, it can soften the flow, and when it is heated to a certain temperature, it produces a chemical reaction and hardens in a cross-chain, and this change is irreversible. It is with this characteristic that the molding process is carried out, and the plasticizing flow during the first heating is used to fill the cavity under pressure, and then solidify into a product that determines the shape and size. This material is called thermoset plastic.

The resin of thermosetting plastics is linear or branched before curing, and after curing, chemical bonds are formed between the molecular chains, which become a third-degree network structure, which can no longer be melted and dissolved in solvents. Phenolic, aldehyde, melamine formaldehyde, epoxy, unsaturated polyester, organic silicon and other plastics are thermosetting plastics.

It is thermoplastic and easy to deform when heated, and thermosetting is not easy to deform when heated.

The difference between thermoplastic and thermoset is the difference in physical and performance aspects.

1. Physical differences.

Thermoplastics can be like water. It can vary between ice and water. As a result, the curing process is reversible, meaning they can be reshaped and remodeled.

The thermoset polymer will form a cross-linked structure during the curing process, preventing it from melting and remodeling. For example, think of thermosets as concrete. Once cured, it can never return to the liquid state.

2. The difference in performance is the face of the mask.

Thermoplastics typically offer high strength, flexibility, and resistance to shrinkage, depending on the type of resin. They are versatile materials that can be used for anything from plastic bags to high-stress bearings and precision mechanical parts.

Thermosets typically have high chemical and heat resistance, as well as a high strength structure that is not easy to deform.

Factors influencing shrinkage in thermoplastic molding:

1. In the molding process of thermoplastics, plastic varieties due to the volume change caused by crystallization, strong internal stress, large residual stress frozen in the plastic parts, strong molecular orientation and other factors, the shrinkage rate is larger than that of thermosetting plastics, the shrinkage rate is wide, the directionality is obvious, and the shrinkage rate after molding, annealing or humidification treatment is generally larger than that of thermosetting plastics.

2. When the characteristics of the plastic part are formed, the molten material contacts the surface of the cavity and the outer layer is immediately cooled to form a low-density solid shell. Due to the poor thermal conductivity of plastics, the inner layer of the plastic part is slowly cooled to form a high-density solid layer with large shrinkage.

Therefore, the wall thickness, slow cooling, and high-density layer thickness shrink greatly. In addition, the presence or absence of inserts, the layout and quantity of inserts directly affect the direction of material flow, density distribution and shrinkage resistance, etc., so the characteristics of plastic parts have a great influence on the shrinkage size and directionality.

Identify the difference between thermoplastics and thermosets: heated, if melted, thermoplastics; If it does not melt, it is a thermosetting plastic

Thermoplastic means that its raw material will become flexible when it is subjected to heat, and can be restored to its original state, or can be reshaped into a different shape. Some thermoplastics are vinyl chloride, acetate, butyrate. Ethylene, polyethylene, polypropylene and styrene.

The plastic components of thermosets solidify when exposed to heat and do not change their original shape when reheated. Some thermosets are phenolic, polyester, and formaldehyde.

Precautions and key points for thermoplastics and thermosets:

Thermoplastics typically have high strength, flexibility, and shrinkage resistance; are linear polymers, i.e. composed of weak molecular bonds in the form of straight chains; It is a resin that is solid at room temperature, but becomes plastic and soft when heated and ignited, due to the melting of the crystals or by flowing beyond the glass transition temperature.

Thermosets typically have higher chemical and heat resistance, as well as stronger structures that are less prone to deformation, and are network polymers, i.e., composed of high cross-linking and strong chemical bonds. Thermoset resins or thermoset polymers are usually liquid materials at room temperature that harden irreversibly upon heat or chemical addition. When it is placed in a mold and heated, the thermoset material solidifies into the specified shape.

Thermoplastic.

It is a plastic that can be softened by repeated heating and hardened by cooling. Thermoplastics can be reused, which is more environmentally friendly and saves materials than general materials. Thermoplastics will lose tung and harden in boiling water. For example, plastic basins. For example, plastic wrap.

Thermosetting plastics are no longer malleable and can no longer be used when heated again, and they are less environmentally friendly than those encountered, and thermosets will become soft in boiling water.

In contrast to the two, thermoplastics can be softened or melted by repeated heating to form products, while thermosets are molded without softening or melting even if they are heated.

The thermoplastic molding process can be continuous, can be molded at high speed, and there are many process methods, and defective products.

And waste plastics can be reused, and the products have good physical and mechanical properties.

However, it has poor heat resistance and rigidity.

Thermosetting plastic molding can only be produced intermittently, it is difficult to achieve continuous production back chain, and the production efficiency is low.

According to the different physical and chemical properties of various plastics, plastics can be divided into two types: thermosetting plastics and thermoplastics. Thermoplastics: refers to plastics that melt after heating, can flow to the mold after cooling, and then melt after heating; Heating and cooling can be used to cause reversible changes (liquid and solid), which is called physical change.

The continuous use temperature of general-purpose thermoplastics is below 100, and polyethylene, polyvinyl chloride, polypropylene, and polystyrene are called the four major general-purpose plastics. Thermoplastics are divided into hydrocarbons, vinyl containing polar genes, engineering, cellulose and other types. It softens when heated and hardens when cooled, and can be repeatedly softened and hardened to maintain a certain shape.

Soluble in a certain solvent, it has the property of being fusible and soluble. Thermoplastics have excellent electrical insulation, especially polytetrafluoroethylene (PTFE), polystyrene (PS), polyethylene (PE), polypropylene (PP) have extremely low dielectric constant and dielectric loss, and are suitable for high-frequency and high-voltage insulating materials. Thermoplastics are easy to mold and process, but they have low heat resistance and are prone to creep, and the degree of creep varies with the load, ambient temperature, solvent, and humidity.

In order to overcome these weaknesses of thermoplastics and meet the needs of applications in space technology, new energy development and other fields, countries are developing melt-moldable heat-resistant resins, such as polyetheretherketone (PEEK), polyethersulfone (PES), polyarylsulfone (PASU), polyphenylene sulfide (PPS), etc. Composites with them as matrix resins have high mechanical properties and chemical resistance, can be thermoformed and welded, and have better interlayer shear strength than epoxy resins. For example, polyetheretherketone is used as the matrix resin and carbon fiber to make composite materials, and the fatigue resistance exceeds that of epoxy carbon fiber.

It has good impact resistance, good creep resistance at room temperature, good processability, can be used continuously at 240 270, and is a very ideal high-temperature resistant insulating material. The composite material made of polyethersulfone as matrix resin and carbon fiber has high strength and hardness at 200 degrees, and can still maintain good impact resistance at -100 degrees. It is non-toxic, non-combustible, with the least smoke and good radiation resistance, and it is expected to be used as a key component of the spacecraft, and can also be molded into a radar radome.

The relative concept of thermoplasticity is thermosetting, which refers to the property that cannot be softened and repeatedly molded when heated, nor dissolved in solvents, and bulk polymers have this property. Plastics that have thermosetting properties are called thermosets.

The difference between thermoplastic and thermoset is mainly due to the difference in physics, properties, and properties.

Thermosetting: Thermosetting refers to the ability to not soften and repeatedly mold when heated, nor to dissolve in solvents, and bulk polymers have this property. Thermoset polymers are plastics, such as epoxy resins, that have the properties of curing after heating and are insoluble, non-melting.

This plastic can only be molded once.

Thermoplasticity: Thermoplasticity refers to the property that a substance can flow and deform when heated and can maintain a certain shape after cooling. Most linear polymers exhibit thermoplasticity and are easily molded by extrusion, injection, or blow molding.

Within a certain temperature range, it can be softened by repeated heating and cooled to harden, as is the case with linear or branched polymers. In daily life, things like plastic bags, plastic clothes hangers and other things are thermoplastic. Therefore, they can be melted by heat for sealing, bonding, etc.

Thermosets in life:

Commonly used thermosetting plastics include phenolic resins, urea-formaldehyde resins, melamine resins, unsaturated polyester resins, epoxy resins, etc.

1. Phenolic resin (PF).

Phenolic resins are one of the longest plastic varieties in history, commonly known as bakelite or bakelite, with a yellow-brown or black appearance and are typical of thermoset plastics.

2. Urea-formaldehyde resin (UF).

Urea-formaldehyde resin is a colorless plastic that can be used as a molding material, adhesive, etc., and is prepared from urea and formaldehyde. Urea-formaldehyde resin molding material is filled with cellulose.

3. Melamine-formaldehyde resin (MF).

Melamine-formaldehyde resin, also known as melamine-formaldehyde resin, is a plastic that makes up for the shortcomings of urea-formaldehyde resin that is not water-resistant, but it is higher than urea-formaldehyde resin.

4. Unsaturated polyester resin (UF).

Unsaturated polyester resins are transparent liquids with different viscosities of pale yellow or amber. Because the strength of unsaturated polyester resin is not high, it is often used with reinforcing materials such as glass fiber, and the product is commonly known as "glass fiber reinforced plastic".

5. Epoxy resin (EP).

Epoxy resins are thermosetting plastics that are cured with a curing agent. It has excellent adhesion, excellent electrical properties, and good mechanical properties.