20 key points for plastic modification formulations

1. Masterbatch core:

The amount of core in the masterbatch is generally more than 20%.

2. Dispersant:

Its function is to make the filler have good compatibility with the carrier resin, and the melting point and melt viscosity should be lower than the carrier resin. Common dispersants are stearic acid and its salts, erucic acid amide, solid paraffin, liquid paraffin, polyethylene wax (that is, relative molecular weight polyethylene), oxidized PE, α-methylstyrene and so on.

The melting point of the dispersant is low, and it can melt rapidly when the temperature rises, and it is coated on the surface of the inorganic filler treated by the coupling agent and crosslinking agent, so that the surface tension of the masterbatch is closer to the main resin, thus greatly improving the dispersibility of the inorganic filler, and can reduce the viscosity of the composite material and improve the fluidity, and the general dosage is about 5%.

3. Carrier resin:

The key to the uniform dispersion of the filler masterbatch in the main resin is the choice of carrier resin, the soft point of random polypropylene is low, the coating effect of calcium carbonate and other particles is good, the melt flow rate of the filler masterbatch is high, and the dispersion of the masterbatch in the main resin is good, but the mechanical properties of the product are greatly affected, and the better needs of the product cannot be reached.

Since the filler masterbatch is mainly used for the processing of polyolefin plastic products such as polyethylene or polypropylene, the carrier resins available are mainly LDPE, PS, EVA, CPE, etc., but HDPE, PP, PS are used as the filler masterbatch for the production of carrier resin alone, the material strip is brittle, not easy to cut into granules (particles are fragile), and the melt flow rate of LLDPE is low. The masterbatch is not easily dispersed.

4.ABS plastic vs PVC:

ABS plastic can significantly enhance the impact strength of PVC, but the effect of reducing the tensile strength is not obvious, some varieties have the function of processing AIDS, the general dosage of 5 to 15. Due to the different composition and relative molecular weight of ABS, the modification effect is often not the same.

5.ABS plastic and MBS plastic:

ABS plastics and MBS plastics are effective impact modifiers of PVC, the main difference is that the former is mainly used for extruding pipes, profiles and calending and blow molding bottles, it should be noted that such modified polymers due to the composition of butadiene unsaturated double bond structure, so mixed with PVC weather resistance is poor, in the formula should be added light stabilizer. Both are very toxic and can be used in contact with food.

6.CPE:

CPE generally contains 20% to 50% chlorine, and varieties with a chlorine content greater than 25% are non-combustible. CPE modified PVC, the biggest feature is good weather resistance, it is generally believed that the varieties with 36% chlorine content, the best modification effect in hard PVC, can obtain good processability, dispersion and impact resistance;

It can be used as a compatible agent of PVC and PE blends, such as PVC/PE/PP blending system (30:28:42) with CPE15%~25%, can get better blending results.

Varieties with a chlorine content of less than 25% are not compatible with PVC, and the main disadvantage of CPE is that the transparency of its products is poor, the tensile strength is low, and the surface luster of the products is not as good as that of pure PVC products.

In addition, the pores of CPE particles are higher than PVC, and there are more gas sandwiched. During the processing, special attention needs to be paid to exhaust, and it is best to use an exhaust extruder when extruding.

7.PVC:

Due to the composition of the shell, the core, the number of layers, etc., there are many varieties of PVC. For rigid PVC products, it is one of the most successful transparency (processing or impact) modifiers developed after MBS.

ACR plays the following role in the modification of PVC:

a, improve the impact strength of rigid PVC material. With the increase of the amount of ACR added, the impact strength of rigid PVC gradually rises, especially within the range of 5 to 10 dosages, the impact strength changes the fastest, and at 10 dosages, it basically reaches the peak, and then there is no obvious effect in increasing the amount of ACR added.

b, as the amount of ACR added to the blend increases, the melting plasticizing time decreases. ACR has the effect of promoting PVC resin gel and plasticizing. PVC with ACR has a significant increase in extrusion expansion than PVC without ACR. ACR201 is generally used in 1 to 3 dosages .

8.EVA plastic raw material modified PVC plastic:

EVA modified plastic PVC varieties are mostly terpolymer EVA, such as ethylene - vinyl acetate - carbon oxide (E-VA-CO), the two blend compatibility is very good, play the role of polymer plasticizer, because of its excellent durability and used in building materials, automobiles, boots and other industries.

9.PVC plastic and butyl cyanide rubber (NBR) :

PVC plastic and butadiene rubber (NBR) have good compatibility, but the compatibility of the two is extremely affected by the acrylic cyanide (AN) in NBR, when the AN content in NBR is about 20%, it has the highest impact strength with PVC blend.

10. PA plastic and PP plastic blend:

When PA plastic and PP plastic are blended, the chemical properties of the blend are improved with the increase of compatibilizers, indicating that when the amount of grafted copolymer is added within a certain range, the chemical reaction generated at the two interfaces is also increased, and the compatibility of PA and PP is better, but when the grafted copolymer exceeds 6.25%, the performance decreases.

11. Natural rubber and PE blend:

In the blending system of natural rubber and PE, due to the interfacial penetration of the non-crystalline part of PE and non-crystalline natural rubber, the mechanical properties are poor. If 6% of the two block copolymer (NR-b-PE) is added, the compatibility of the two is improved, and the interfacial tension is reduced, and the dispersion size of PE is reduced.

12. Compatible agent:

Under the premise of fully saturating the entire interface of the blend, the less the better, the usual dosage is less than 20%.

13. Reactive compatibilizers:

Reactive compatibilizers mostly contain acid group, epoxy group, isocyanate group and vinyl group, etc., which form new chemical bonds between the compatibilizers and the polymer components of the blend, also known as chemical compatibilizers. It is especially suitable for blending polymers with poor compatibility and reactive functional groups.

There are mainly carboxylate PE, carboxylate PP, carboxylate PS, etc., which are designed to promote the compatibility of non-polar polymers (PE, PP, PS, etc.) and polar polymers polyamide (PA).

14. Classification of flame retardant grade of plastics

The flame retardant grade of plastics increases step by step from HB, V-2, V-1 to V-0:

HB: The lowest flame retardant class in UL94 and CSA C22.2 No.0.17 standards. For samples 3 to 13 mm thick, the combustion rate is less than 40 mm per minute; For samples less than 3 mm thick, the burning rate is less than 70 mm per minute; Or extinguish in front of the 100 mm sign.

V-2: After two 10-second combustion tests of the sample, the flame is extinguished within 60 seconds. There can be combustibles falling.

V-1: After two 10-second combustion tests of the sample, the flame is extinguished within 60 seconds. Nothing can fall.

V-0: After two 10-second combustion tests on the sample, the flame is extinguished within 30 seconds. Nothing can fall.

15. Routine precautions for modified plastic dyeing:

(1) PS coloring formula

PS is a colorless transparent plastic, its coloring, mainly to make full use of its excellent coloring performance, to produce a variety of beautiful colors, should focus on considering the colorant's brightness, transparency and heat resistance. Due to the general color migration in the PS middle, there is a wide range of colorants to choose from.

(2) PVC coloring formula

There are the following factors that affect the coloring of PVC: First, PVC is thermally decomposed to release HCL, so heat stabilizer should be added to the formula. Secondly, in order to reduce costs, fillers are often added, and the types and amounts of these additives have a great impact on the change of color; Third, soft and hard products, especially the former with plasticizer, will also make a great change in color, which should be fully understood and paid attention to.

16. Insufficient use of titanate coupling agent

(1) High cost.

(2) titanate due to its own oxidation or with some antioxidants in polyolefin, easy to form a darker compound, affecting the whiteness of calcium carbonate, made of masterbatch gray.

(3) Calcium carbonate treated with titanate coupling agent, in the storage process or processing process, the oil-wet end of the titanate molecule is prone to hydrolysis or alcoholysis and lose its role. The best amount of titanate according to the nature of the filler and the use of the product through the experiment to determine, under normal circumstances, the recommended amount of filler 0.5%-3%.

17. Aluminate coupling agent:

It can improve the dispersion of various fillers and pigments and the vividness of pigments, and its color is lighter, and it can increase the organic skin film of fillers such as calcium carbonate. The thermal stability is better than titanate, it can play a chemical role on the surface of the filler, and can produce bonding and crosslinking effects at the interface.

The amount of titanate coupling agent is generally 0.5% to 2.5% of the filler, and the amount of filler with high specific surface area or high active surface such as carbon black and alumina can be increased to 1.5% to 2.5%. Aluminate coupling agent can be used with titanate coupling agent to produce synergistic effect, improve performance and reduce cost.

18. Titanate:

The amount of titanate is calculated as a percentage of the filler, and the best amount in the modified plastic process should be determined by experiment according to the nature of the filler and the use of the product, under normal circumstances, the recommended amount is 0.5% to 3%.

19. Aluminate:

The general amount of aluminate is 0.25 to 0.5 parts, which can be used with tribasic lead sulfate and disalt lead phosphate to play a synergistic stabilizing effect, and have a certain lubricating effect on PVC, and the surface finish of the product has been improved. Aluminate coupling agent is cheap, can reduce the cost of formula, can also be used in PE, PP, PU, PS and other formulations.

20.MBS modified plastic PVC:

When PVC is modified with MBS, the amount of MBS is usually maintained at 10% to 15%. And MBS modified PVC is generally transparent products.