How to choose plastic raw materials?

The key to formula design is the selection of materials, collocation, dosage, and mixing. The surface looks very simple, but it actually contains a lot of internal connections. It is not easy to design a high-performance, easy-to-process, low-price formula. There are many factors to consider. Today, Jiuzhi Plastics Co., Ltd. provides the following factors for your reference.

1. Selection of resin

(1) Selection of resin type The resin should be selected to be the one closest to the performance of the modification purpose, so as to save the use amount of the auxiliary agent. Such as wear-resistant modification, the resin should first consider the choice of three major wear-resistant resins PA, POM, UH-MWPE; and if transparent modification, the resin should first consider the choice of three transparent trees PS, PMMA, PC.

(2) The choice of the resin grade is different from the grade of the same resin, and the performance difference is also very large. The grade closest to the performance of the modification should be selected. For example, heat-resistant modified PP can be selected within the range of PP grades with heat distortion temperature of 100~l4O °C. We should use PP grades with heat resistance of 140 °C, such as PP-4012 of Korean oil.

(3) Resin fluidity selection The viscosity of various plasticized materials in the formulation should be close to ensure processing fluidity. For materials with widely varying viscosities, a transition material is added to reduce the viscosity gradient. For example, PA66 is toughened in PA66, and PA6 is often used as a transition material. In PA6 toughening and flame retardant formulations, HDPE is often added as a transition material.

Different processing methods require different fluidity.

Different varieties of plastic have different fluidity. The plastic is thus divided into high-flow plastics, low-flow plastics and non-flowable plastics, as follows: high-flow plastics, PS, HIPS, ABS, PE, PP, PA, etc.; low-flow plastics, PC, MPPO, PPS, etc.; non-flowing plastics, polytetrafluoroethylene, UHMWPE, PPO, etc.

Plastics of the same variety also have different fluidity. The main reason is the difference in molecular weight and molecular chain distribution, so the same raw materials are divided into different grades. Different processing methods require different fluidity, so the grades are divided into injection molding grade, extrusion grade, blow molding grade, and calendering grade. Different modification purposes require different fluidity, such as high filling requirements, such as magnetic plastics, filler materials, halogen-free flame retardant cable materials.

(4) The selectivity of the resin to the auxiliary agent such as PPS cannot be added with lead and copper-containing additives, and PC cannot use antimony trioxide, which can cause depolymerization. At the same time, the acidity and alkalinity of the additive should be consistent with the acidity and alkalinity of the resin, otherwise it will react with both.

2. Selection of additives

(1) Select the auxiliaries according to the purpose to be achieved according to the purpose to be achieved. The auxiliaries should be able to fully exert their expected effects and meet the specified targets. The specified indicators are generally the national standards of the products, international standards, or performance requirements proposed by the customer. The specific selection range of the auxiliary agent is as follows.

Toughening - selection of elastomers, thermoplastic elastomers and rigid toughening materials.

Enhanced - glass fiber, carbon fiber, whisker and organic fiber.

Flame retardant - bromine (common bromine and environmentally friendly bromine), phosphorus, nitrogen, nitrogen / phosphorus composite expansion flame retardant, antimony trioxide, hydrated metal hydroxide.

Antistatic - all kinds of antistatic agents.

Conductive - carbon (carbon black, graphite, carbon fiber, carbon nanotubes), metal fibers and metal powder, metal oxides.

Magnetic - ferrite magnetic powder, rare earth magnetic powder including samarium cobalt (SmCo5 or Sm2Co17), neodymium iron boron (NdFeN), cobalt nickel cobalt magnetic powder three categories.

Thermal conductivity - metal fibers and metal powders, metal oxides, nitrides and carbides; carbon materials such as carbon black, carbon fibers, graphite and carbon nanotubes; semiconductor materials such as silicon, boron.

Heat resistant - glass fibers, inorganic fillers, heat resistant agents such as substituted maleimides and beta crystal nucleating agents.

Transparent - nucleating agent, sorbitol series Millad 3988, which is an alpha crystal nucleating agent for PP, works best.

Wear-resistant - graphite, molybdenum disulfide, copper powder, etc.

Insulation - calcined kaolin.

Barrier - mica, montmorillonite, quartz, etc.

(2) Auxiliary resin has selective red phosphorus flame retardant effective for PA, PBT, PET; nitrogen flame retardant is effective for oxygen-containing, such as PA, PBT, PET, etc.; nucleating agent effect on copolymerized polypropylene Good; glass fiber heat-resistant modification has a good effect on crystalline plastics, and has poor effect on amorphous plastics; carbon black is filled with conductive plastics and has good effects in crystalline resins.

(3) Form of additives

The auxiliaries of the same composition have different effects on the modification.

(1) Shape of the auxiliary agent The reinforcing effect of the fibrous auxiliary agent is good. The degree of fiberization of the additive can be expressed by the aspect ratio. The larger the L/D, the better the reinforcement effect, which is why we add glass fiber to the vent. The molten state is advantageous for maintaining the aspect ratio and reducing the fiber breaking ratio.

The spherical auxiliaries have good toughening effect and high brightness. Barium sulphate is a typical spherical auxiliaries, so high-gloss PP is filled with barium sulfate, and a small degree of rigidity and toughness can also be used.

(2) Particle size of the auxiliary

1. Effect of particle size on mechanical properties The smaller the particle size, the more beneficial the tensile strength and impact strength of the filler material.

For example, in terms of impact strength, the particle size of antimony trioxide is not reduced by 1 μm, and the impact strength is doubled.

2. Effect of particle size on flame retardancy The smaller the particle size of the flame retardant, the better the flame retardant effect. For example, the smaller the particle size of the hydrated metal oxide and the antimony trioxide, the less the amount of addition to achieve the same flame retardant effect.

For another example, the addition of 4% of antimony trioxide having a particle size of 45 μm to ABS has the same flame retarding effect as the addition of 1% antimony trioxide having a particle size of 0.03 μm.

3. Effect of particle size on color matching The smaller the particle size of the coloring agent, the higher the coloring power, the stronger the hiding power and the more uniform the color. However, the particle size of the colorant is not as small as possible, there is a limit value, and the limit values ​​for different properties are different. For the coloring power, the ultimate particle size of the azo colorant was 0.1 μm, and the limit particle size of the phthalocyanine colorant was 0.05 μm. For the hiding power, the limiting particle size of the colorant is about 0.05 μm.

4. Effect of Particle Size on Conductivity The carbon black is taken as an example. The smaller the particle size, the easier it is to form a network-like conductive path, and the same conductive effect is added to reduce the amount of carbon black. However, like the coloring agent, the particle size also has a limit value, the particle size is too small to be gathered and difficult to disperse, and the effect is not good.

(3) The surface treatment auxiliary of the auxiliary agent should have good compatibility with the resin, so as to ensure the dispersion of the auxiliary agent and the resin according to the expected structure, to ensure the completion of the design index, and to ensure the long-lasting effect of the effect in the service life. Lifting, migration resistance, and resistance to precipitation. If most of the formulations require uniform dispersion of the auxiliaries and the resin, it is desirable for the barrier formulation to be layered in the resin. In addition to a small amount of additives such as surfactants, good compatibility with the resin is the key to its efficacy and increased addition. Therefore, it is necessary to try to improve or improve the compatibility, such as surface activation treatment with a compatibilizer or a coupling agent.

After the surface of all inorganic additives has been treated, the modification effect will be improved. Especially the filler is most obvious, and other glass fiber, inorganic flame retardant and the like. The surface treatment is mainly a coupling agent and a compatibilizer, the coupling agent is specifically a silane, a titanate and an aluminate, and the compatibilizer is a maleic anhydride graft polymer corresponding to the resin.

4. Reasonable amount of additives

(1) The more additives are added, the better, such as flame retardant, toughening agent, magnetic powder, barrier, etc., the more the amount added, the better.

(2) Some additives have the best value, such as conductive additives, which can be formed after the electrical path, and then add no effect; if the coupling agent is used, the surface can be coated, and then useless; The electrostatic agent can form a charge-discharging layer on the surface of the product.

5. Relationship between additives and other components

The auxiliaries selected in the formulation should exert their own functions, and should not affect the function of other auxiliaries without deteriorating or minimally limiting. It is best to have synergistic effects with other auxiliaries. In a specific formulation, many types of auxiliaries may be added for different purposes, and the interrelationship between these auxiliaries is complicated. Some additives have a synergistic effect, and some additives have an antagonistic effect.

(1) Synergistic synergy means that the effect of adding two or more additions in a plastic formulation is higher than the average value of the individual additions.

1. In the anti-aging formula, the specific synergistic effect is: two kinds of phenolic antioxidants with different steric substitutions of hydroxy groups and synergistic effects; two kinds of amine antioxidants with different structures and activities have synergistic effect Effect; synergistic effect of combined use of amines and phenolic antioxidants with different oxidation resistance; synergistic effect of fully hindered phenols and phosphite antioxidants; synergistic effect of semi-hindered phenols and thioester antioxidants Function, mainly used in indoor products; hindered phenolic antioxidants and hindered amine light stabilizers; hindered amine light stabilizers and phosphorus antioxidants; hindered amine light stabilizers and ultraviolet light absorbers.

2. In the flame retardant formula, there are many examples of synergistic effects, mainly the following.

In the halogen/antimony composite flame retardant system, the halogen flame retardant can react with Sb2O3 to form SbX3, and SbX3 can isolate oxygen to achieve the purpose of increasing the flame retardant effect.

In the halogen/phosphorus composite flame retardant system, two types of flame retardants can also react to form high-density gases such as PX3, PX2, and POX3, which can function to isolate oxygen. In addition, the two types of flame retardants can also promote each other in the gas phase and the liquid phase, thereby improving the flame retarding effect.

(2) Counteracting effect The counteracting effect means that the effect of adding two or more additives together in a plastic formulation is lower than the average value of the individual additions.

a. In the anti-aging plastic formula, there are many antagonistic particles, and the main conditions are as follows.

HALS-based light stabilizers are not used in combination with thioether-based antioxidants because the acidic components of comb ethers inhibit the photostability of HALS. Aromatic amines and hindered phenolic antioxidants are generally not used in combination with carbon black-based external light-shielding agents because carbon black catalyzes the direct oxidation of amines or phenols and inhibits the anti-oxidation effect. The commonly used antioxidants have an antagonistic effect with some of the sulfides, especially polysulfides, because the polysulfides help to oxidize.

If HALS is not compatible with acidic additives, the acid additives will react with the alkaline HALS, causing the HALS to fail. In the presence of acidic additives, generally only UV absorbers can be used.

b. In the flame retardant plastic formula, there are also examples of countermeasures, mainly the following.

The combination of a halogen-based flame retardant and a silicone-based flame retardant will reduce the flame retardant effect; the red phosphorus flame retardant and the silicone-based flame retardant may also have an antagonistic effect.

c. Examples of other countermeasures are as follows.

Lead salt additives cannot be used together with additives containing sulfur compounds, and lead U causes lead pollution. Therefore, in the PVC processing formula, the lead stearate lubricant and the thiol organotin should not be added together; the thiol tin stabilizer can not be used in the insulation layer of the steel cable, otherwise it will cause copper pollution; In the filling formula of a large number of oil-absorbing fillers, the amount of oil additives such as DOP and lubricant should be increased accordingly to compensate for the absorbed portion.

6. The ingredients of the formula should be mixed evenly.

(1) Some components are added in portions for a formulation with a large amount of filler, and the filler is preferably added in two portions. The first time in the hopper, the second time in the middle side feed port. For example, if PE is added to a halogen-free flame retardant formulation of 150 parts of aluminum hydroxide, it should be added in two portions, otherwise it cannot be granulated. For the coupling agent treatment of the filler, it is generally sprayed in three times to be evenly dispersed, and the coupling effect is good.

(2) Reasonable arrangement of feeding order In the formula of PVC or filled masterbatch, the order of feeding of various materials is very important. In the filling masterbatch formulation, the filler should be added first, and after mixing, the water can be removed after heating, which is beneficial to the subsequent coupling treatment. In the PVC formulation, the external lubricant is added later to avoid affecting the uniform mixing of other materials.

7. The negative impact of the formulation on other properties

The designed formulation should not degrade or minimally affect the basic physical and mechanical properties of the resin. At the very least, the original properties should be retained, and it is preferable to improve some properties of the original resin. However, the objective fact is that everything has two sides. When improving a certain performance, it may reduce other performances. Therefore, when designing a formula, it must be considered comprehensively, and as far as possible, it does not affect other performance. For example, the high-filling formula has a great influence on the mechanical properties and processing properties of the composite material, and the impact strength and tensile strength are greatly reduced, and the processing fluidity is deteriorated. If the product has specific requirements on the mechanical properties of the composite, specific compensation should be made in the formulation, such as adding elastomeric material to compensate for impact properties, and adding lubricant to improve processing performance.