The main production equipment of modified plastics is twin-screw extruder, the characteristics of modified plastics are different, the use of different methods, additives are also different. Based on more than 20 years of experience and technological innovation, Xinpanyu Company now brings you a brief understanding of the basics of modified plastics and production process.

What is modified plastic?

The main component of plastic is resin, so its basic properties are mainly determined by the nature of the resin, but additives also play a role. The resin accounts for about 40% to 100% of the total weight of the plastic, and the resin is a polymer compound that has not been mixed with various additives.

Plastic modification is through physical, chemical, mechanical and other ways to enhance or improve the original properties of the resin are called plastic modification. The modified plastics are collectively called “modified plastics”.

The process of modification can occur in the process of polymerization of synthetic resins, that is, chemical modification, such as copolymerization, grafting, cross-linking, etc., but also in the process of synthetic resins are processed, that is, physical modification, such as filler, blending, enhancement and so on.

In the actual production of plastics, a certain percentage of stabilizer is almost always added, in order to prevent the degradation of raw materials in storage, transportation and processing. Therefore, non-modified plastics are basically non-existent.

All plastics can be modified to improve the quality of the plastic, such as density, hardness, precision, processability, chemical properties, corrosion resistance, aging resistance, abrasion resistance, flame retardant, barrier and cost.

Plastic modification is the most effective way to reduce cost and improve performance. Especially in the recycled plastics industry is widely used.

Why plastic modification?

1、The concept of resource regeneration is deeply rooted in people's mind

World resources will always be a major hot topic for mankind, the concept of resource regeneration has been deeply rooted in people's hearts, plastics are made from petroleum refining products, and petroleum resources are limited, so recycling recycled plastics can save petroleum resources, in response to the national advocacy of resource conservation.

Recycled plastic is often lost the original plastic properties, to use recycled materials to produce new plastics, plastic modification process is inevitable.

According to different needs, the processing of a certain aspect of the properties of the corresponding products, so as not to let the loss of resources. People through the recycling of resources, in order to truly achieve environmental protection and energy saving.

2、Expand the scope of application of plastic

First of all, let's talk about the advantages and disadvantages of plastics.

Advantages: most plastics are light; good chemical stability, not easy to rust; have a certain toughness, that is, good impact resistance; good insulation, low thermal conductivity; easy to process, low processing costs.

Disadvantages: poor heat resistance, flammable; easy stress deformation, poor dimensional stability; strength is not high; low temperature brittleness; poor solvent resistance, etc..

The properties of these plastics, such as strength, flame retardancy, impact resistance and processing performance, need to meet the specified requirements before they can be applied in the market in practical applications.

For example, PP as a general-purpose plastics, in the field of automotive exterior trim, pure PP material low-temperature, rigidity, toughness can not meet the requirements of the PP material in the performance of the performance of rigidity and toughness modification to meet the needs of use.

Daily applications often need plastics with a variety of characteristics, to a certain degree of toughness but also resistance to low-temperature brittleness; not only to insulation, but also stability.

The purpose of plastic modification is to broaden the use of raw materials environment, greatly enhance the performance of some of the raw materials, thereby expanding the scope of application of plastic, so the significance of plastic modification is self-evident.

3, the synthesis of new polymer materials difficult, neither economic nor practical

Plastics chemical industry from the birth of the first plastic product counting, the development of the plastics industry has been 120 years of history, has successfully researched and synthesized thousands of polymer materials, but which has an industrial value of only more than a hundred kinds of plastics, and more than 90% of commonly used plastics are concentrated in the five major general-purpose resins of PE, PP, PVC, PS, ABS.

The development of new polymers is not only a huge investment, but also the application prospects are uncertain, neither economic nor realistic. Therefore, it is the most cost-effective solution to utilize the existing plastics and expand their performance through modification technology.

What are the methods of plastic modification?

1, filler modification (mineral filling)

By adding inorganic mineral (organic) powder to ordinary plastics, the rigidity, hardness, heat resistance and other properties of plastic materials are improved. There are many kinds of fillers, and their characteristics are also complex.

The role of plastic fillers: improve plastic processing performance, improve physical and chemical properties, increase volume, reduce costs.

Requirements for plastic additives:

(1) chemically inactive, inert, no adverse reaction with the resin and other additives;

(2) It does not affect the water resistance, chemical resistance, weathering resistance and heat resistance of plastics;

(3) It does not reduce the physical properties of plastics;

(4) It can be filled in large quantities;

(5) The relative density is small, and it has little effect on the density of products.

2、Enhanced modification (glass fiber/carbon fiber)

Enhancement measures: by adding glass fiber, carbon fiber and other fibrous substances.

Enhancement effect: can significantly improve the material's rigidity, strength, hardness, heat resistance.

Adverse effects of modification: but many materials will lead to poor surface and reduced elongation at break.

Reinforcement principle:

(1) The reinforced material has high strength and modulus;

(2) The resin has many inherent good physical, chemical (corrosion resistance, insulation, irradiation resistance, resistance to transient high temperature ablation, etc.) and processing properties;

(3) resin and reinforcing materials composite, reinforcing materials can play a role in enhancing the mechanical or other properties of the resin, while the resin on the reinforcing materials can play a role in bonding and transfer of load, so that the reinforced plastics have excellent performance.

3、Toughening modification

There are more materials are not tough enough, too brittle, can be added through the toughness of the material or ultra-fine inorganic materials, increase the toughness of the material and low-temperature performance.

Toughening agent: in order to reduce the brittleness of the plastic after hardening, improve its impact strength and elongation and join the resin in an additive.

Commonly used toughening agent - mostly maleic anhydride graft compatibilizer:

Ethylene vinyl acetate copolymer (EVA)

Polyolefin elastomers (POE)

Chlorinated polyethylene (CPE)

Acrylonitrile-butadiene-styrene copolymer (ABS)

Styrene-Butadiene Thermoplastic Elastomer (SBS)

Ethylene propylene diene rubber (EPDM)

4、Flame retardant modification (halogen-free flame retardant)

In the electronic and electrical appliances, automotive and many other industries require materials with flame retardant, but many plastic raw materials themselves have low flame retardancy. Flame retardant can be added to improve the flame retardancy of the material.

Flame retardant: also known as flame retardant, refractory agent or fire retardant, giving flammable polymers flame retardant functional additives; most of them are compounds of elements in the VA (phosphorus), VIIA (bromine, chlorine) and ⅢA (antimony, aluminum) group of the periodic table.

Molybdenum compounds with smoke suppression, tin compounds and iron compounds also belong to the category of flame retardants, mainly for plastics with flame retardant needs, delay or prevent the combustion of plastics, especially polymer plastics. It is mainly used to delay or prevent the combustion of plastics, especially polymer plastics, so that their ignition time increases, and they are self-extinguishing and difficult to ignite.

Plastic flame retardant grade: from HB, V-2, V-1, V-0, 5VB to 5VA step by step.

5、Weathering modification (anti-aging, UV protection, low temperature resistance)

Generally refers to the cold resistance of plastics at low temperatures. Due to the inherent low-temperature brittleness of plastics, plastics become brittle at low temperatures, and thus for many plastic products used in low-temperature environments, they are generally required to be cold-resistant.

Weatherability: It refers to a series of aging phenomena such as fading, discoloration, cracking, chalking and strength loss of plastic products due to sunlight irradiation, temperature changes, wind and rain and other external conditions. Ultraviolet irradiation is the key factor to promote plastic aging.

6、Modified alloy

Plastic alloy is the use of physical blending or chemical grafting, copolymerization methods, two or more materials prepared into a high-performance, functional, specialization of a new material to improve the performance of a material or both the characteristics of the purpose of the material. It can improve or enhance the performance of existing plastics and reduce costs.

General-purpose plastic alloys: such as PVC, PE, PP, PS alloys are widely used, the production technology has been generally mastered.

Engineering plastics alloy: refers to engineering plastics (resin) blends, mainly including PC, PBT, PA, POM (paraformaldehyde), PPO, PTFE (polytetrafluoroethylene) and other engineering plastics as the main body of the blending system, as well as the ABS resin modification materials.

The growth rate of the use of PC/ABS alloy is in the forefront of the plastics field. At present, PC / ABS alloying research has become a polymer alloy research hot spot.

7, other modifications

Such as the use of conductive fillers to reduce the electrical resistivity of plastics; add pigments / dyes to change the color of the material, add internal / external lubricants to improve the processing properties of the material, the use of nucleating agents to change the crystalline properties of semi-crystalline plastics to improve their mechanical properties and optical properties and so on.