How many auxiliaries can you use in recycled plastic processing?

First, the role of plastic additives

The plastic additive can effectively improve the processing performance of the recycled material and improve the production efficiency; and can improve the physical and mechanical properties and the use performance of the recycled product, improve the use value and working life, and achieve the purpose of high value of the recycled material.

Second, the requirements for additives

Because plastics are processed and the products are affected by many factors, the requirements for the selection of additives will also be high, mainly the following:

1 should have good compatibility with the added synthetic resin, can be stable for a long time, and uniformly dispersed in the resin;

2 Synergies. Try to use plastic additives that promote each other's functions;

3 Durable. No dialysis, no hair, no migration or extraction by water and liquid substances;

4 suitable for the use of products;

5 Adaptability to processing conditions;

6 Good dispersibility, easy to disperse evenly during processing.

The above points can meet the requirements of most of the recycled materials for the additives. When the plastic additives can reach these points, they will exert an efficient effect and maximize the performance of the recycled plastics.

Third, several kinds of plastic additives are commonly used

Characteristic additive

The main function of such additives is to impart certain characteristics to plastic products, such as physical and mechanical properties, flexibility, flame retardancy and the like.

1 plasticizer

Plasticizers can reduce the melting temperature, viscosity and hardness of plastics, increase the fluidity of plastics and the softness and cold resistance of products, thereby improving the processing properties and performance of plastics. Plasticizers are mainly used in plastics such as PVC, cellulose derivatives, synthetic rubber and nylon. Not all plastics require plasticizers, of which about 80% of plasticizers are used in PVC.

2 filler

It is to add an inert material to the plastic in order to increase the quality, reduce the cost and so on. The filler is generally a powdery substance, and the main varieties are calcium carbonate, talc, kaolin, wollastonite, mica and wood powder, and are commonly used in PVC, polyolefin and ABS resins.

3 enhancer

The reinforcing agent can increase the strength of the recycled material, and most of them are high-strength, fibrous inert materials such as glass fiber, carbon fiber, asbestos, etc., and the glass fiber is used in the largest amount. Reinforcing agents are now widely used in plastics such as PVC, PP, PE and nylon.

4 colorants and fluorescent whitening agents

The coloring agent mainly imparts color to the plastic and makes the product more beautiful. Fluorescent whitening agent can effectively improve the appearance of recycled plastic products, and can be used with colorants to make the products more beautiful.

5 flame retardant

A flame retardant is an additive that prevents or retards the burning of plastics. Mainly divided into two types of additive flame retardants and reactive flame retardants. Additive flame retardants are usually added to the base resin in an additive manner, and they are simply a simple physical mixture with the resin; the reactive flame retardant is generally a monomer containing a flame retardant element and a reactive group in the molecule. Such as halogenated anhydride, halogenated bisphenol and phosphorus-containing polyol, etc., due to reactivity, can be chemically bonded to the molecular chain of the resin, becoming part of the plastic resin, most reactive flame retardant structures are synthetically added flame retardant Monomer of the agent.

6 impact modifier

Additives that increase the impact strength of plastics are called impact modifiers. Generally used for some elastomers and toughness plastics, mainly used in PVC, PS, PP and some engineering plastics.

7 foaming agent

A foaming agent is a substance which can generate a gas and cause a cell to produce cells or voids, and is classified into a physical foaming agent and a chemical foaming agent. Physical blowing agents generally rely on changes in their physical state to release gases, mostly volatile liquid substances, chlorofluorocarbons (such as Freon), low alkanes (such as pentane) and compressed gases are representative of physical blowing agents. Chemical foaming agents are foamed based on gases released by chemical decomposition. Most commonly used are hydrazine derivatives, the most important of which is azodicarbonamide, which can be used in PVC, PE, PS, PP and ABS. In plastic.

2. Stabilizer

The main function of the stabilizer is to delay or stop the degradation of the plastic under physical (heating, light) and chemical (oxygen, microbial) factors. There are mainly heat stabilizers, light stabilizers and antioxidants.

1 heat stabilizer

Thermal stabilizers can retard or avoid plastic damage and further degradation due to thermal effects. Usually not stated, the heat stabilizer refers specifically to the stabilizer used in the processing of polyvinyl chloride and vinyl chloride copolymers. Polyvinyl chloride and vinyl chloride copolymers are heat-sensitive resins, which are very easy to release hydrogen chloride during heat processing, thereby causing heat aging degradation reaction. The types of heat stabilizers widely used in industry generally include base-based stabilizers such as salt-based lead salts, metal soaps, organotins, and organic oximes, and epoxy compounds, phosphites, polyols, and Organic auxiliary stabilizers such as ketones.

2 light stabilizer

Light stabilizers mainly inhibit or reduce the photodegradation of plastics and improve the weather resistance of plastic products. Ultraviolet light in sunlight has the greatest destructive effect on plastics, and impurities or chromophores in the polymer can also promote photooxidative degradation of the polymer. Light stabilizers are mainly used for polyolefins, followed by rubber-modified PS, PVC, and PU.

3 antioxidants

Antioxidants can retard or inhibit the oxidative degradation of plastics. Antioxidants are the most important type of plastic stabilization aids, and almost all polymer resins are involved in the application of antioxidants.

Generally divided into primary antioxidants and auxiliary antioxidants. The main antioxidant has the main function of capturing polymer peroxy radicals; the auxiliary antioxidant has the function of decomposing the polymer peroxy compound, also called "peroxide decomposition agent".

3. Processing additives

Processing additives can make plastic recycled materials easy to mold or improve molding efficiency, mainly including release agents and lubricants.

1 lubricant

Lubricants can reduce the viscosity of plastic melt or the coefficient of friction between the melt and the processing equipment. It can be divided into internal lubricants and external lubricants. The internal lubricant can reduce the viscosity of the polymer in the molding process and reduce the energy consumption by reducing the friction between the polymer molecules; the external lubricant acts to reduce the friction or adhesion between the polymer and the processing equipment, usually external lubrication The agent is incompatible with the polymer.

2 release agent

Similar to an external lubricant, a thin layer of high-efficiency release agent is formed between the product and the mold to allow the product to self-release the mold.