Flame Retardant Modified Plastics Formulation Design Points

Flame Retardant Modified Plastics Formulation Design Points

We do modified plastics product development work, each received a case, need to understand the process is generally: first determine the material, and then understand the molding method, technical performance parameters (including parts use, flame retardant level, product color, etc.), reliability (durability) and other special requirements.

The key core of the formulation design for the selection of resin, raw materials and auxiliaries with the matching, dosage ratio and mixing and blending. According to the author's many years of experience in the design of formulations, to provide the following aspects of the key points for your reference.

1. Determine the material

Customers to define the material type

If the customer can specify the material of the product, we can further develop the work according to the specific material requirements and physical parameters provided by the customer.

Customers can not specify the type of material, but there are sample materials or samples

We can test and analyze according to the samples provided by the customer, material identification analysis, some materials can be clear based on experience or fire, but also with the help of analytical instruments for accurate determination, such as infrared spectroscopy and other spectra.

Customers can not specify the material, there is no sample material and sample pieces

We can help customers select materials based on experience, the resin should be selected with the customer's requirements of the performance of the closest varieties, such as the requirements of high transparency, the resin should be the first to consider the choice of transparent resins AS, PS, PMMA, PC, such as the further requirements of high temperature resistance, it is best to choose PC.

Different grades of the same resin, the performance difference is also very large, fluidity, impact properties, tensile strength and elongation and other properties need to be familiar with, so the need for a variety of resins of different manufacturers of grades to collect information and accumulate experience.

2. Determine the molding method

Different molding methods have different requirements for the fluidity of the material, so it is important to choose the fluidity of the main resin.

The viscosity of various raw material resins in the formula should be close to ensure processing fluidity. For a large difference in viscosity materials, the need to reduce the viscosity gradient, such as PA66 toughened flame retardant formulations often add PA6 to adjust the viscosity.

Even the same variety of resins have different mobility, because different types of resins with different molecular weights and molecular structure, but also divided into many different models. According to the processing method, they can be divided into injection molding grade, extrusion grade, blow molding grade, calendering grade, etc.

Through the above understanding, we can select the suitable material and the main raw material resin, and lay a good foundation for other performance adjustment in the next step.

3.Determine the technical performance parameters

Technical performance parameters include the functional use of parts, physical and chemical properties, flame retardant grade, color and other requirements.

After determining the material and molding method, we need to further understand the specific function and use of the customer's products. For example, the customer's product is a PP bumper, it is clear that the product is a larger part, the material ultimately need better fluidity, we need to choose a high fluidity and high impact copolymer PP resin. If the customer's products are engine compartment parts, then the focus is to consider the requirements of high temperature resistance, oil resistance, flame retardant.

Understand the customer's product information, can be more specific to indicate the functional direction of the modified formula, can be more clear for the selection of materials and performance requirements for the basis.

Physical and chemical properties of the technical parameters is an important basis for the design of modified formulations, through the customer's physical properties table requirements, various international standards or national standards requirements, test samples to analyze the data.

According to the physical and chemical properties to be achieved to select the appropriate raw materials and additives, the addition of raw materials and additives should be able to give full play to its expected effectiveness, and to achieve the required indicators.

The specific selection of raw materials and auxiliaries can refer to the following table:

Table 2 Selection of modification targets and raw and auxiliary materials

The use of raw materials and auxiliaries for plastic modification requires attention to a number of factors, combined with a variety of changing requirements, to grasp the optimal selection of materials and ratios. The following points of concern are summarized here:

The use of flame retardants

Different types of resins, select the appropriate flame retardant, but need to consider the synergy and confrontation between the raw materials, for example, halogenated flame retardants need to be used in conjunction with antimony trioxide in order to facilitate the flame retardant properties of the material, and PC and PET can not be used with antimony trioxide, which can lead to depolymerization of the resin material.

The acidity and alkalinity of various raw materials and auxiliaries should be consistent with the acidity and alkalinity of the resin, otherwise it will also produce reactions and have a greater impact on the performance.

Synergistic raw materials: in the halogen/antimony composite flame retardant system, the halogen flame retardant can react with Sb2O3 to generate SbX3, SbX3 can isolate the oxygen so as to achieve the purpose of increasing the flame retardant effect.

In the halogen/phosphorus composite flame retardant system, the two types of flame retardants can also react to generate PX3, PX2, POX3 and other gases, these gases can play a role in isolating oxygen. In addition, the two types of flame retardants can also promote each other in the gas phase and liquid phase, so as to improve the flame retardant effect.

Raw materials with antagonistic effect: experience shows that halogenated flame retardants and organosilicon flame retardants and will reduce the flame retardant effect; and red phosphorus flame retardant and organosilicon flame retardants and also the existence of antagonistic effect.

Red phosphorus flame retardant is effective for PE, PA, PBT, PET and other materials, but the color can only be red or black products, light-colored products can not be used, in addition, due to environmental issues, many products prohibit red phosphorus.

Nitrogen-based flame retardants are effective for oxygen-containing resins, such as PA, PBT, PET, etc. However, when these materials are reinforced with glass fibers, MCA and glass fibers will have a wick effect, which will have an impact on the flame retardancy, and therefore only other flame retardant systems can be selected.

The smaller the particle size of the flame retardant, the better the flame retardant effect. For example, the smaller the particle size of hydrated metal oxides and Sb2O3, the smaller the amount added to achieve the same flame retardant effect.

Literature research shows that in ABS add 4%, particle size of 45 μm Sb2O3 and add 1%, particle size of 0.03 μm Sb2O3 flame retardant effect is the same, more favorable to maintain better mechanical properties and reduce costs.

Enhance the use of filler materials

Morphology of the material: the enhancement effect of fibrous filler is good. The degree of fibrillation can be expressed in the L/D ratio, the larger the L/D, the better the enhancement effect, for example, long glass fibers need to be added from the exhaust holes, or short glass fibers from the lateral feed to join, so that the melt state is conducive to maintaining the L/D ratio, reducing the impact of broken fiber. Different L/D ratio wollastonite reinforced filler, the enhancement effect has a large difference.

The spherical filler has good toughening effect and high brightness. Barium sulfate is typical of the spherical, so the filling of high gloss PP choose barium sulfate, rigid toughening can also choose precipitation method of barium sulfate, and low-cost filler material calcium carbonate is also spherical, the right amount of the ratio can be achieved to toughening enhancement of the purpose of cost reduction.

Sheet filler enhancement effect between fibrous and spherical, typical representative of talcum powder, of which the higher the silicon content, the better the effect of increasing rigidity, the shrinkage rate of the material is also between the fibrous and spherical filler materials.

Powder particle size: the smaller the particle size, the more beneficial to the tensile strength and impact strength of the filler material, for example, calcium carbonate particle size 200 mesh and 1250 mesh filler PP material comparison, 1250 mesh filler PP impact strength and tensile strength can be increased by 1.5 times. The effect of using finer calcium carbonate in PVC materials to enhance the tensile strength and elongation is significantly better than the use of coarse particle size calcium carbonate.

Surface treatment of raw and auxiliary materials or additives

It is necessary to consider the compatibility of the raw and auxiliary materials with the resin in order to ensure the dispersion effect of each component to achieve the intended target performance, and good compatibility with the resin is the key to play its efficacy and increase the amount of additives. Therefore, to increase or improve the compatibility, it is necessary to add suitable compatibility agent, or use coupling agent for powder material surface activation treatment, etc..

After the surface of inorganic additives are treated, the modification effect will be improved. Especially the filler is the most obvious, and other glass fiber, inorganic flame retardant, etc.. Surface treatment is based on coupling agent and compatibilizer, coupling agent specific such as silanes, titanates and aluminum esters, compatibilizer for the resin corresponding to the maleic anhydride graft polymer. For example, calcium carbonate is generally modified with an aluminum ester coupling agent or phthalate coupling agent, the tensile strength and elongation will be significantly increased

4. Determining reliability (durability) requirements

Plastic resin itself has many weaknesses, such as not heat aging, modified materials according to different use occasions usually require reliability tests are as follows:

Weathering and thermal aging requirements

Thermal and oxygen aging requirements is an important indicator of the service life of the material requirements, so there is a lot of research on the thermal and oxygen aging behavior of various types of materials.

Improvement of weathering and heat aging performance is mainly through the selection of better weathering and heat aging performance of the resin on the one hand, and on the other hand through the addition of weathering additives such as antioxidants, UV inhibitors, light stabilizers and other weathering additives, as well as good weathering pigments, such as titanium dioxide and carbon black, and so on.

Such as PVC resin, the higher the molecular weight, the better the heat aging, heat-resistant grade of PVC materials, plasticizers can choose TOTM than DOTP, DOP.

Materials used in different occasions, there are different weathering and heat aging requirements, outdoor products require UV or xenon lamp aging time are longer, such as automotive front window water strips, are generally used ASA this weathering performance is very prominent material, and if the use of ABS, due to the butadiene unsaturated bond is easy to break, the service life will be greatly reduced.

In addition, some materials can be post-processing products can also improve the temperature resistance and heat aging level, such as polyolefin wire and cable materials for the heat-resistant level of 90 degrees, 105 degrees, 125 degrees and 150 degrees, and the higher the temperature resistance level, you need to achieve the purpose of micro-crosslinking or irradiation cross-linking, then the design of the formula needs to be considered to cross-linking of the body of the raw material and cross-linking additives.

Dual 85 test for moisture and heat resistance

The general double 85 test refers to the changes in physical properties and appearance after storage in a high temperature and high humidity test chamber at a humidity of 85%RH and a temperature of 85℃ for 168H. In specific products, the required storage time will be longer, and now many materials for new energy vehicles are required to be stored for more than 1000H.

Resistance to precipitation and extraction

Resistance to precipitation and extraction of modified materials requires attention to the selection of base resins and raw and auxiliary materials, such as the extraction resistance of PVC materials to meet the requirements of n-hexane test, PVC can be selected molecular weight of more than 1,000, the plasticizer requires more stable TOTM or epoxy soybean oil.

Flame-retardant materials of the anti-extraction requirements, on the one hand, low molecular raw materials to be controlled, on the other hand, the selection of flame retardants is particularly important. Such as flame retardant nylon with MCA system is easy to white, or flame retardant reinforced nylon flame retardant containing MPP system corrosion mold white, are the impact of flame retardant precipitation. Therefore, try to avoid the use of easily precipitated flame retardants, or through the modification of flame retardants and improve compatibility to reduce the impact of precipitation.

In addition to low molecular resin and some flame retardants are easy to precipitate, antioxidants and low molecular weight lubricants need to control the selection and amount of additive, especially in the black products in the low molecular additives in the high temperature and high humidity environment is very easy to precipitate out of the surface resulting in whitening.

Conclusion

In fact, in the process of modified plastics formulation design, far more than the above list, other factors to consider a lot, such as in order to improve a certain performance and have to reduce other properties, so in the design of the formula, we must take into account the full range, as far as possible not to affect the other properties.

In addition to the performance of the material factors, but also need to consider the processing performance of the material to ensure that the molding of the product, and the processing equipment and the use of the environment without adverse effects.

Convenience of procurement of raw and auxiliary materials, there are many materials will be affected by the import of many links, can use domestic materials as much as possible with domestic materials, can use general-purpose materials as much as possible with general-purpose, rare and scarce materials are often not easy to purchase, but also prone to out-of-stock resulting in unstable formulations.

Also need to consider the cost of materials, as far as possible, the use of low-priced raw materials and additives, follow the principle of procurement in the vicinity of the low cost of transportation, so that the total cost of the design of the formula in order to have market competitiveness.

Conclusion

In the process of formulating modified plastics, various factors need to be taken into consideration to ensure high performance and quality of the final product. YINSU Flame Retardant Company, based on its expertise in the field of flame retardant, provides a series of specialized flame retardant solutions for different materials.

YINSU Flame Retardant Company: Innovative Flame Retardant Solution

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