On the basis of general plastics and engineering plastics, through physical, chemical, mechanical and other methods, through filling, blending, reinforcement and other processing methods, performance of plastics is improved or functions are added, mechanical properties such as flame retardancy, strength, impact resistance, toughness of plastics are improved and enhanced, making plastics suitable for use in special electrical, magnetic, light, thermal and other environmental conditions.

From production of raw resin to production of modified plastic masterbatch of various specifications and varieties; it is used in raw materials and molding process of almost all plastic products.
Plastic modification has a wide range of applications, and properties of almost all plastics can be improved through modification methods. 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, etc. In order to reduce cost of plastic products, improve performance, and enhance functions, plastic modification technology is inseparable.

 

Physical modification: In principle, no chemical reaction occurs, it is mainly a physical mixing process. Physical modification process is often accompanied by chemical reactions.
Chemical modification: chemically perform reactions such as block copolymerization, graft copolymerization, cross-linking and degradation on polymer molecular chain, or introduce new functional groups to form polymer materials with specific functions.

By adding inorganic mineral (organic) powder to ordinary plastics, rigidity, hardness, heat resistance and other properties of plastic materials can be improved. There are many types of fillers and their properties are extremely complex.

Role of plastic filler (filler for plastics): improve plastic processing performance, improve physical and chemical properties, increase volume, and reduce costs.

 

Characteristics that plastic extender fillers should have:
(1) It is chemically inactive and inert, does not react adversely with resin and other additives;
(2) Does not affect water resistance, chemical resistance, weather resistance, heat resistance, etc. of plastic;
(3) Does not reduce physical properties of plastics;
(4) Can be filled in large quantities;
(5) Relative density is small and has little impact on density of product;
(6) Price is relatively low.

1) Measures: By adding fibrous substances such as glass fiber and carbon fiber.

 

2) Effect: It can significantly improve rigidity, strength, hardness and heat resistance of material.
3) Adverse effects: However, many materials will cause poor surface quality and significantly reduced toughness.
4) Enhancement principle:
Reinforcement materials have higher strength and modulus;
Resin has many inherent excellent physical, chemical (corrosion resistance, insulation, radiation resistance, instantaneous high temperature ablation resistance, etc.) and processing properties;
After resin is compounded with reinforcing material, reinforcing material can improve mechanical or other properties of resin, resin can bond and transmit loads to reinforcing material, giving reinforced plastic excellent properties.

There are many materials that are not tough enough or too brittle. Toughness and low-temperature performance of materials can be increased by adding materials with better toughness or ultra-fine inorganic materials.
Toughening agent: An additive added to resin in order to reduce brittleness of plastic after hardening, improve its impact strength and elongation.
Commonly used toughening agents:
Mostly maleic anhydride graft compatibilizer)——
Ethylene-vinyl acetate copolymer (EVA),
Chlorinated polyethylene (CPE),
Acrylonitrile-butadiene-styrene copolymer (ABS),
Styrene-butadiene thermoplastic elastomer (SBS),
Ethylene propylene diene rubber (EPDM)......
They are all effective toughening agents for plastics, especially engineering plastics.

 

In many occasions, materials are required to be flame retardant. The more commonly used occasions are electronic appliances. Automotive industry also has flame retardant requirements, but they are generally lower. Flame retardancy can be achieved by adding flame retardants.
Most plastics are flammable. With wide application of plastics in construction, furniture, transportation, aviation, aerospace, electrical appliances, etc., improving flame retardancy of plastics has become a very urgent issue.
Flame retardants: also known as flame retardants, fire retardants or fire retardants, functional additives that make flammable polymers flame retardant; most of them are compounds of elements from groups VA (phosphorus), VIIA (bromine, chlorine) and IIIA (antimony, aluminum) in periodic table.

 

Molybdenum compounds, tin compounds and iron compounds that have smoke-suppressing effects are also included in category of flame retardants. They are mainly suitable for plastics that require flame retardancy to delay or prevent burning of plastics, especially polymer plastics.
Ignition time is increased, ignition self-extinguishes, and it is difficult to ignite.

 

1) Endothermic effect
Heat released by any combustion in a short time is limited. If part of heat released by fire source can be absorbed in a short time, flame temperature will decrease, radiate to burning surface and act on gasified gas. Heat required to break down combustible molecules into free radicals will be reduced, and combustion reaction will be inhibited to a certain extent.
Under high temperature conditions, flame retardants undergo a strong endothermic reaction, absorbing part of heat released by combustion, lowering temperature of surface of combustible materials, effectively inhibiting generation of flammable gases, and preventing spread of combustion. Flame retardant mechanism of Al(OH)3 flame retardant is to increase heat capacity of polymer, allowing it to absorb more heat before reaching thermal decomposition temperature, thereby improving its flame retardant performance. This type of flame retardant gives full play to its ability to absorb a large amount of heat when combined with water vapor to improve its own flame retardant ability.
2) Covering effect
After adding flame retardants to combustible materials, flame retardants can form a glassy or stable foam covering layer at high temperatures to isolate oxygen, have functions of heat insulation, oxygen isolation, and preventing flammable gases from escaping outward, thereby achieving purpose of flame retardancy.
For example, organic phosphorus flame retardants can produce cross-linked solid substances or carbonized layers with a more stable structure when heated. On the one hand, formation of carbonized layer can prevent further pyrolysis of polymer, and on the other hand, it can prevent thermal decomposition products inside it from entering gas phase to participate in combustion process.
3) Inhibit chain reaction
According to chain reaction theory of combustion, free radicals are needed to maintain combustion. Flame retardants can act on gas phase combustion zone to capture free radicals in combustion reaction, thereby preventing spread of flames, reducing flame density in combustion zone, and ultimately reducing combustion reaction speed until it is terminated.
For example, evaporation temperature of halogen-containing flame retardants is same as or similar to decomposition temperature of polymer. When polymer decomposes by heat, flame retardant also volatilizes at the same time. At this time, halogen-containing flame retardant and thermal decomposition products are in gas phase combustion zone at the same time. Halogen can capture free radicals in combustion reaction, thereby preventing spread of flame, reducing flame density in combustion zone, ultimately reducing combustion reaction speed until it is terminated. .
4) Non-flammable gas suffocation effect
Flame retardants decompose into non-combustible gases when heated, diluting concentration of combustible gases decomposed from combustible materials below lower combustion limit. At the same time, it also has a diluting effect on oxygen concentration in combustion zone, preventing continuation of combustion and achieving a flame retardant effect.

Flammability UL94 rating - is the most widely used flammability performance standard for plastic materials. It is used to evaluate ability of a material to extinguish after being ignited. There are many evaluation methods based on burning speed, burning time, anti-drip ability and whether dripping beads burn.
Plastic flame retardant grade: gradually increases from HB, V-2, V-1, V-0, 5VB to 5VA.
HB: The lowest flame retardant grade in UL94 standard.

 

V-2, V-1, V-0, 5VB, 5VA flame retardant standards

Generally refers to cold-resistant ability of plastics at low temperatures. Due to inherent low-temperature brittleness of plastics, plastics become brittle at low temperatures. Therefore, plastic parts like automobiles generally require cold resistance.
Weather resistance: refers to a series of aging phenomena such as fading, discoloration, cracking, powdering and loss of strength caused by plastic products being affected by external conditions such as sunlight, temperature changes, wind and rain.
Ultraviolet radiation is a key factor in aging of plastics.
Various weather resistance measurement methods have been developed for various materials and different usage situations, such as various aging tests to simulate natural climate conditions and conduct tests.
Coating weather resistance test, also known as atmospheric exposure test, evaluates durability of coating itself to atmosphere.
Weather resistance of leather can be measured in a weather resistance test chamber (or aging chamber, accelerated weather resistance instrument) that simulates natural climate.

 

Plastic alloys use physical blending or chemical grafting or copolymerization methods to prepare two or more materials into a high-performance, functional, and specialized new material to to achieve purpose of improving performance of one material or combining characteristics of two materials.
Plastic alloys are widely used in automobiles, electronics, precision instruments, office equipment, packaging materials, building materials and other fields.
It can improve or enhance performance of existing plastics and reduce costs.
General plastic alloys: such as PVC (polyvinyl chloride), PE (polyethylene), PP (polypropylene), PS (polystyrene) alloys, are widely used and production technology is generally mastered.
Engineering plastic alloy: generally refers to blends of engineering plastics (resins), mainly including blending systems based on engineering plastics such as PC, PBT, PA, POM (polyoxymethylene), PPO, PTFE (polytetrafluoroethylene), etc., as well as ABS resin modified materials.
Output of PC/ABS alloys is growing at a rate of about 10% every year, and its growth rate ranks among the highest in plastic field. At present, PC/ABS alloying research has become a hot spot in polymer alloy research.

Following table shows main subcategories, consumer groups and market applications of modified plastics.

 

Flame-retardant plastic products can greatly reduce risk of fire in the event of short circuit, overload, water immersion, etc.

 

It is mainly divided into weather-resistant toughened PP special materials, glass fiber reinforced thermoplastics and other products.
1) Weather-resistant and toughened PP special material: Weather-resistant and toughened PP special material is a new polypropylene material with engineering plastic characteristics. It has advantages of good low-temperature toughness, small molding shrinkage, high rigidity, and strong weather resistance. It is mainly used for It needs to be resistant to weather and ultraviolet rays in outdoor environments. Its main consumer groups include home appliance companies, auto parts companies, etc.
2) Glass fiber reinforced thermoplastics: Main products 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 include computer accessories companies, mechanical parts companies, power tool companies, lighting companies, etc.

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, etc.
PC alloy applications: automotive instrument panels, computer and office automation equipment, power tool housings, cellular phones, etc.
PVC/ABS alloy: It is produced using PVC and ABS as matrix and adding various modifiers such as tougheners, lubricants, stabilizers, and flame retardants.
Performance advantages: excellent mechanical properties, weather resistance, processing rheological properties, good surface gloss of products, good injection molding and extrusion effects, and is an alloy material with extremely excellent cost performance.
Scope of application: It can replace flame-retardant and weather-resistant ABS, PC, etc., and is used in home appliance casings, electrical switches, meter casings, lighting materials, communication networks, building materials, etc.
Polyester alloy: has excellent mechanical properties (fatigue resistance), dimensional stability, resistance to chemical reagents, and resistance to environmental stress cracking,
Application scope: automobiles, home appliances, power tools and other fields.

Mainly refers to high impact polystyrene toughened flame retardant color masterbatch.

 

Characteristics of functional color masterbatch - it can not only reduce production costs but also improve product quality.
1) Meet flame retardant requirements for electrical and electronic products according to standards such as UL94, IEC-65 and GB8898;
2) Improve toughness, processing fluidity and demoulding properties of HIPS resin;
3) Give HIPS resin color.

Although new varieties of engineering plastics are constantly increasing and application fields are constantly being expanded, and due to expansion of production equipment, costs are gradually decreasing. However, today, as modification equipment and modification technology continue to develop and mature, general-purpose thermoplastic resins continue to have engineering characteristics through modification, and have seized part of application market of traditional engineering plastics.

With vigorous development of domestic automobile, electrical, electronic, communications and machinery industries, demand for modified engineering plastics will increase significantly, various high-strength and heat-resistant engineering plastics will be widely used.

High-performance engineering plastics such as polyphenylene sulfide (PPS), polyimide (PIM), polyetheretherketone (PEEK), polysulfone (PSF) and liquid crystal polymer (LCP) have good electrical properties, high temperature resistance, and dimensional stability. Some also have good flame retardancy, radiation resistance, chemical resistance and mechanical properties. Therefore, it has increasingly important applications in cutting-edge technology fields such as electronic appliances, automobiles, instruments and meters, home appliances, aviation, coatings industry, petrochemical industry, rockets, and aerospace.