Modification knowledge necessary for plastics

On the basis of general plastics and engineering plastics, through physical, chemical, mechanical and other methods, through filling, blending, reinforcement and other processing methods to improve the performance or increase the functionality of plastics, flame retardancy, strength, impact resistance of plastics The mechanical properties such as toughness are improved and improved, so that the plastic can be applied under special environmental conditions such as electricity, magnetism, light and heat.

Application range of modification technology

From the production of raw resin to the production of modified plastic masterbatch of various specifications and varieties, it is widely used in the raw materials and molding process of almost all plastic products. Such as plastic appearance, transparency, density, precision, processability, mechanical properties, chemical properties, electromagnetic properties, corrosion resistance, aging resistance, wear resistance, hardness, thermal properties, flame retardancy, barrier properties. In order to reduce the cost of plastic products, improve performance, and improve functions, plastic modification technology is indispensable.

Commonly used modification methods:

1. Filling modification

Improve the rigidity, hardness, heat resistance and other properties of plastic materials by adding inorganic mineral (organic) powder to ordinary plastics. There are many types of fillers, and their characteristics are also complicated.

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

Requirements for plastic additives:

(1) It is inert, inert, and does not react adversely with resins and other additives;

(2) Does not affect the water resistance, chemical resistance, weather resistance, heat resistance, etc. of the plastic;

(3) does not reduce the physical properties of the plastic;

(4) can be filled in a large amount;

(5) The relative density is small, which has little effect on the density of the product;

(6) The price is relatively low.

2, enhanced modification

Enhancement measures: by adding fibrous materials such as glass fiber and carbon fiber.

Enhancement effect: can significantly improve the rigidity, strength, hardness and heat resistance of the material.

Adverse effects of modification: However, many materials can cause surface defects and elongation at break.

Enhancement principle:

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

(2) The resin has many inherently excellent physical and chemical properties (corrosion resistance, insulation, radiation resistance, transient high temperature ablation, etc.) and processing properties;

(3) After the resin is combined with the reinforcing material, the reinforcing material can promote the mechanical or other properties of the resin, and the resin can bond and transfer the load to the reinforcing material, so that the reinforced plastic has excellent performance.

3. Toughening modification

There are many materials with insufficient toughness and too brittleness. It can increase the toughness and low-temperature performance of the material by adding a material with good toughness or ultra-fine inorganic materials.

Toughener: An additive added to a resin to reduce the brittleness of the plastic after hardening and to increase its impact strength and elongation.

Common toughening agents - mostly maleic anhydride grafting compatibilizer:

Ethylene-vinyl acetate copolymer (EVA)

Polyolefin elastomer (POE)

Chlorinated polyethylene (CPE)

Acrylonitrile-butadiene-styrene copolymer (ABS)

Styrene-butadiene thermoplastic elasticity (SBS)

EPDM

4, flame retardant modification

In many industries such as electronic appliances and automobiles, materials are required to have flame retardancy, but many plastic raw materials have low flame retardancy. Increasing the flame retardancy can be achieved by adding a flame retardant.

Flame retardant: also known as flame retardant, fire retardant or fire retardant, a functional additive that imparts flame retardancy to flammable polymers; most of them are VA (phosphorus), VIIA (bromo, chlorine) and A compound of the IIIA (锑, aluminum) group element.

Molybdenum compounds, tin compounds and iron compounds, which have a smoke suppressing effect, are also in the category of flame retardants, and are mainly suitable for plastics having flame retardant requirements, delaying or preventing the burning of plastics, especially polymer plastics. It makes its ignition time increase, ignites itself and is difficult to ignite.

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

5, weathering modification

It 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. Therefore, for many plastic products used in low temperature environments, they are generally required to have cold resistance.

Weather resistance: refers to a series of aging phenomena such as fading, discoloration, cracking, chalking and strength degradation of plastic products due to exposure to external conditions such as sunlight, temperature changes, wind and rain. Ultraviolet radiation is a key factor in aging plastics.

6, modified alloy

Plastic alloys are prepared by using physical blending or chemical grafting and copolymerization to prepare two or more materials into a new material with high performance, functionalization and specialization to improve the performance of one material or both. The purpose of the material properties. It improves or improves the performance of existing plastics and reduces costs.

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

Engineering plastic alloy: Refers to the blend of engineering plastics (resin), mainly including blending systems based on engineering plastics such as PC, PBT, PA, POM (polyoxymethylene), PPO, PTFE (polytetrafluoroethylene). And ABS resin modified materials.

The output of PC/ABS alloys is increasing at a rate of about 10% per year, and its growth rate ranks among the top in the plastics field. At present, PC/ABS alloying research has become a hot spot in polymer alloy research.

Main categories of modified plastics:

The main sub-categories, consumer groups and market applications of modified plastics.

1. Flame retardant resin

Flame-retardant plastic products can greatly reduce the risk of fire when short circuit, overload, flooding, etc. occur.

2, enhanced toughening resin

Mainly divided into weathering toughened PP special materials, glass fiber reinforced thermoplastics and other products.

(1) Weathering and toughening PP special material: weathering and toughening PP special material is a new polypropylene material with engineering plastic properties, which has the advantages of good low temperature toughness, small molding shrinkage, high rigidity, strong weather resistance, etc. For outdoor environments that require weather and UV resistance. Its main consumer groups are home appliance companies and auto parts companies.

(2) Glass fiber reinforced thermoplastics: The products mainly include glass fiber reinforced AS/ABS, glass fiber reinforced PP, glass fiber reinforced nylon, glass fiber reinforced PBT/PET, glass fiber reinforced PC, glass fiber reinforced PPE/PPS, etc. Its main consumer groups are computer parts companies, mechanical parts companies, power tool companies, lighting companies.

3, plastic alloys

Mainly divided into PC alloy, PVC alloy and polyester alloy.

PC alloy product features: high impact strength, creep resistance, heat resistance, low water absorption, non-toxic, excellent dielectric properties.

PC alloy applications: automotive instrument panels, computer and office automation equipment, power tool housings, cellular phones, etc.

PVC/ABS alloy: It is made of PVC and ABS as matrix, adding various modifiers such as toughening agent, lubricant, stabilizer and flame retardant.

Performance advantages: excellent mechanical properties, weather resistance, processing rheological properties, good surface gloss, good injection molding and extrusion, and an excellent alloy material with excellent cost performance.

Scope of application: It can replace flame retardant weathering ABS, PC, etc., and is used in home appliance casings, electrical switches, meter casings, lighting materials, communication networks, building materials, etc.

Polyester alloy: It has excellent mechanical properties (fatigue resistance), dimensional stability, chemical resistance, and resistance to environmental stress cracking. Applications: Automotive, home appliances, power tools, etc.

4, functional color master class

Mainly refers to high impact polystyrene toughened flame retardant masterbatch.

The characteristics of the functional color master - can reduce production costs and improve product quality.

(1) Meet the requirements of UL94, IEC-65 and GB8898 for the flame retardant requirements of electrical and electronic products;

(2) improving the toughness, processing fluidity and mold release property of the HIPS resin;

(3) The color of the HIPS resin is imparted.