Flame Retardant Modified Plastic Formulation And Design Points

Flame Retardant Modified Plastic Formulation And Design Points

As a company specializing in the research and development of modified plastic products, our workflow typically involves several key steps whenever we undertake a new project. Initially, we determine the material type, followed by understanding the molding methods, technical performance parameters (including component usage, flame-retardant grade, product color, etc.), and any special requirements regarding reliability (durability).

The core of formulation design lies in resin selection, the combination of raw materials and additives, dosage ratios, and mixing and compounding processes. Based on years of experience in formulation design, YINSU Flame Retardants offers the following key points for reference:

I. Determining the Material

• Customer Specifies the Material Type:

If the customer can clearly specify the material type, we can proceed with further work based on the specific material requirements and physical property parameters provided by the customer.

• Customer Cannot Specify the Material Type but Provides Samples:

If the customer cannot specify the material type but provides samples, we can conduct tests and analyses to identify the material. Some materials can be identified based on experience or simple tests like burning, while others may require the use of analytical instruments for accurate determination, such as infrared spectroscopy.

• Customer Cannot Specify the Material Type and Provides No Samples:

In cases where the customer cannot specify the material type and provides no samples, we can assist in material selection based on our experience. The resin should be chosen based on the performance requirements specified by the customer. For example, if high transparency is required, transparent resins such as AS, PS, PMMA, or PC should be considered first. If additional high-temperature resistance is needed, PC would be the best choice.

Different grades of the same resin can have significant differences in properties, including flowability, impact resistance, tensile strength, and elongation. Therefore, it is essential to be well-versed in the properties of various resin grades from different manufacturers and to accumulate experience through continuous research and documentation.

II. Determining the Molding Method

Different molding methods have varying requirements for material flowability, making the selection of the base resin's flowability crucial. In formulations, the viscosities of various raw material resins should be similar to ensure processability and flow. For materials with significant viscosity differences, it is necessary to reduce the viscosity gradient. For example, in PA66 toughening and flame-retardant formulations, PA6 is often added to adjust the viscosity.

Even within the same resin type, flowability can vary significantly due to differences in molecular weight and structure, resulting in various grades. Resins can be categorized by processing methods into injection molding grade, extrusion grade, blow molding grade, and calendering grade.

By understanding these factors, suitable materials and base resins can be selected, laying a solid foundation for further adjustments in other performance aspects.

III. Determining Technical Performance Parameters

Technical performance parameters include the functional requirements of the component, physicochemical properties, flame-retardant grade, color, and other specifications. After determining the material and molding method, it is essential to further understand the specific function and purpose of the customer's product. For example, if the customer's product is a PP bumper, it clarifies that the component is a relatively large part, and the material will require better flowability. In this case, we would select a high-flow, high-impact copolymer PP resin. If the customer's product is an engine compartment component, the focus would shift to requirements such as high-temperature resistance, oil resistance, and flame retardancy.

Understanding the customer's product information can more specifically define the functional direction of the modified formula and provide a basis for selecting materials and setting performance requirements. The technical parameters of physicochemical properties are crucial for the design of the modified formula and can be obtained through the customer's property requirements, various international or national standards, or analysis of test samples. Select the appropriate raw materials and additives based on the required physicochemical properties, ensuring that they fully exert their intended effects and meet the required standards.

The specific selection of raw materials and additives can be referenced in the table below:

Table 2 Modification objectives and selection of raw and auxiliary materials

When using raw and auxiliary materials and additives for plastic modification, many factors need to be considered. In line with diverse and changing requirements, the best - suited materials and proportions should be grasped. The main concerns summarized here are as follows:

• Use of Flame Retardants

For different types of resins, corresponding flame - retardants should be selected. However, the synergy and antagonism between raw materials need to be considered. For example, halogen - based flame - retardants need to be used in combination with antimony trioxide (Sb₂O₃) to be beneficial to the flame - retardant properties of materials. But PC and PET cannot use antimony trioxide, as these can cause the depolymerization of resin materials. The acidity and alkalinity of various raw and auxiliary materials and additives should be consistent with that of the resin. Otherwise, reactions will occur, which have a great impact on the properties.

Synergistic Raw Materials

In the halogen/antimony - based composite flame - retardant system, halogen - based flame - retardants can react with Sb₂O₃ to form SbX₃. SbX₃ can isolate oxygen, thus achieving the purpose of enhancing the flame - retardant effect. In the halogen/phosphorus - based composite flame - retardant system, the two types of flame - retardants can also react to generate gases such as PX₃, PX₂, and POX₃. These gases can play a role in isolating oxygen. In addition, the two types of flame - retardants can promote each other in the gas phase and liquid phase respectively, thereby improving the flame - retardant effect.

Antagonistic Raw Materials

Experience shows that the combined use of halogen - based flame - retardants and silicone - based flame - retardants will reduce the flame - retardant effect. Also, there is antagonism when red - phosphorus flame - retardants are used in combination with silicone - based flame - retardants. Red - phosphorus flame - retardants are effective for materials such as PE, PA, PBT, and PET. However, only red or black products can be made in terms of color, and they cannot be used for light - colored products. In addition, red phosphorus is prohibited in many products due to environmental protection issues. Nitrogen - based flame - retardants are effective for oxygen - containing resins such as PA, PBT, and PET. However, when these materials are reinforced with glass fibers, there will be a wick effect between MCA and glass fibers, which affects the flame - retardancy. Therefore, other flame - retardant systems can only 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 less the amount required to achieve the same flame - retardant effect. Some literature studies have shown that adding 4% of Sb₂O₃ with a particle size of 45μm to ABS has the same flame - retardant effect as adding 1% of Sb₂O₃ with a particle size of 0.03μm, which is more conducive to maintaining good mechanical properties and reducing costs.

• Use of Reinforcing and Filling Materials

Morphology of Materials

Fibrous fillers have a good reinforcing effect. The degree of fiberization can be expressed by the aspect ratio (L/D). The larger the L/D, the better the reinforcing effect. For example, long glass fibers need to be added through the exhaust port, or short glass fibers can be added through side - feeding. This molten state is conducive to maintaining the aspect ratio and reducing the impact of broken fibers. Filler materials reinforced by wollastonite with different aspect ratios have significant differences in reinforcing effects. Spherical fillers have a good toughening effect and high brightness. Barium sulfate is a typical spherical filler. Therefore, barium sulfate is selected for filling high - gloss PP. Precipitated barium sulfate can also be selected for rigid toughening. Calcium carbonate, a low - cost filler material, is also spherical. An appropriate proportion can achieve the goals of toughening, reinforcing, and cost - reduction. The reinforcing effect of flaky fillers is between that of fibrous and spherical fillers. Talc powder is a typical representative. The higher the silicon content, the better the stiffness - increasing effect. The shrinkage rate of the material is also between that of fibrous and spherical filler materials.

Particle Size of Powders

The smaller the particle size, the more beneficial it is to the tensile strength and impact strength of the filled material. For example, when comparing PP materials filled with calcium carbonate of 200 - mesh and 1250 - mesh particle sizes, the impact strength and tensile strength of PP filled with 1250 - mesh calcium carbonate can be increased by 1.5 times. In PVC materials, the use of finer calcium carbonate for reinforcement results in significantly better tensile strength and elongation than the use of coarse - particle - sized calcium carbonate.

• Surface Treatment of Raw and Auxiliary Materials or Additives

The compatibility between raw and auxiliary materials and the resin needs to be considered to ensure the dispersion effect of each component and achieve the predetermined target performance. Good compatibility with the resin is the key to giving full play to its efficacy and increasing the addition amount. Therefore, to improve or enhance the compatibility, suitable compatibilizers need to be added, or surface activation treatment with coupling agents can be carried out on powder materials. After the surface treatment of inorganic additives, the modification effect will be improved. This is particularly obvious for fillers, and it also applies to glass fibers, inorganic flame - retardants, etc. The main surface - treatment agents are coupling agents and compatibilizers. Specific coupling agents include silanes, titanates, and aluminate esters, and the compatibilizer is the maleic anhydride - grafted polymer corresponding to the resin. For example, after calcium carbonate is generally modified with aluminate coupling agents or phthalate coupling agents, the tensile strength and elongation will be significantly improved.

IV. Determining Reliability (Durability) Requirements

Plastic resins inherently have many weaknesses, such as poor resistance to thermal aging. Modified materials are required to meet various reliability requirements based on their specific applications. The common reliability tests include the following aspects:

• Weathering and Thermal Aging Requirements

Thermal oxidative aging is a crucial indicator of material service life, and there is extensive research on the thermal oxidative aging behavior of various materials. To enhance weathering and thermal aging performance, two main approaches are used: (1) selecting resins with better weathering and thermal aging resistance, and (2) adding stabilizers such as antioxidants, UV absorbers, light stabilizers, and weather-resistant pigments like titanium dioxide and carbon black.

For PVC resins, higher molecular weight generally correlates with better thermal aging resistance. High-temperature PVC materials benefit from using plasticizers like TOTM, which are superior to DOTP and DOP. Different applications have varying weathering and thermal aging requirements. Outdoor products, for example, require longer resistance to UV or xenon lamp aging. Automotive front windshield wiper blades typically use ASA, which has outstanding weathering resistance. In contrast, ABS materials are less suitable due to the susceptibility of butadiene double bonds to breakage, significantly reducing their service life.

Some materials can also be improved through post-processing. For instance, the heat resistance of polyolefin wire and cable materials is categorized into 90°C, 105°C, 125°C, and 150°C grades. Higher heat resistance is achieved through microcrosslinking or irradiation crosslinking, which must be considered in the formulation design by selecting crosslinkable base materials and crosslinking aids.

• Humidity and Heat Testing (Dual 85 Test)

The Dual 85 test refers to the evaluation of material properties and appearance after storage in a high-temperature and high-humidity chamber at 85% RH and 85°C for 168 hours. For specific products, the required storage time may be even longer. Many materials used in new energy vehicles now require testing for over 1000 hours.

• Resistance to Bloom and Extraction

The resistance to bloom and extraction of modified materials is critical when selecting base resins and additives. For example, PVC materials must meet n-hexane extraction requirements, which can be achieved by using high molecular weight PVC (above 1000) and more stable plasticizers like TOTM or epoxidized soybean oil.

In flame-retardant materials, controlling low-molecular-weight additives and selecting appropriate flame retardants are essential. For instance, the use of MCA systems in flame-retardant nylon can lead to whitening, while flame-retardant enhanced nylon with MPP systems can cause mold corrosion and whitening due to flame retardant bloom. Therefore, it is advisable to avoid flame retardants prone to bloom or to modify them to improve compatibility and reduce bloom.

In addition to low-molecular-weight resins and some flame retardants, the selection and dosage of antioxidants and low-molecular-weight lubricants should be carefully controlled, especially in black products. Low-molecular-weight additives can easily bloom and cause whitening on the surface under high-temperature and high-humidity conditions.

V. Conclusion

In reality, the process of formulating modified plastic compounds involves far more considerations than those listed above. Often, enhancing one property may necessitate a trade-off with another. Therefore, when designing formulations, it is crucial to take a holistic approach to minimize negative impacts on other properties.

Beyond the performance characteristics of the materials, processing properties must also be considered to ensure the successful molding of the product and to avoid any adverse effects on processing equipment or the operating environment.

The accessibility of raw materials and additives is another important factor. Many materials are subject to the complexities of importation. Where possible, domestic materials should be preferred over imported ones, and common materials should be used instead of rare or hard-to-find alternatives. The use of scarce materials can lead to supply chain disruptions and instability in formulations.

Additionally, cost considerations are essential. Whenever possible, lower-cost raw materials and additives should be selected, adhering to the principle of local sourcing to minimize transportation costs. Only by doing so can the overall formulation cost be competitive in the market.

In the complex landscape of flame-retardant modified plastics formulation, YINSU Flame Retardant company stands out as a leading provider of high-performance solutions. YINSU's flame-retardants are designed to meet stringent industry standards, offering excellent performance while adhering to environmentally friendly, halogen-free principles. These flame retardant not only enhance the flame-retardant properties of plastics but also maintain the mechanical and processing characteristics required for various applications. With a focus on cost-effectiveness, YINSU's products are competitively priced, making them an attractive choice for manufacturers seeking to balance performance, sustainability, and economic viability. By integrating YINSU's flame-retardant technology into their formulations, customers can achieve superior protection against fire hazards without compromising on quality or increasing costs, thus gaining a significant edge in the market.