In the field of polymer material processing, in order to give the material a variety of excellent properties, it is often necessary to compound fireproof masterbatch with functional additives such as antioxidants and lubricants. However, the compatibility between different additives has a significant impact on the final performance of the material. Reasonable compatibility test standards and compounding scheme design are the key to ensuring product quality.
Compatibility testing must first focus on appearance. After adding fireproof masterbatch and other functional additives to the base resin in a planned proportion, samples are made by injection molding, extrusion and other processing methods. Observe whether the sample surface has stratification, precipitation, uneven color and other phenomena. If there is obvious stratification, it indicates that the compatibility between the additives is poor, which may lead to material performance degradation during processing or long-term use. For example, in the polypropylene (PP) system, if the flame retardant component in the fireproof masterbatch is incompatible with the lubricant, the surface of the product may "bloom" after injection molding, that is, the lubricant migrates to the surface, affecting the appearance of the product and subsequent processing procedures such as coating.
Thermal stability is also an important test indicator. Use thermogravimetric analyzer (TGA), differential scanning calorimeter (DSC) and other equipment to monitor the mass change and thermal enthalpy change of the compound additive system during the heating process. If abnormal mass loss or thermal enthalpy mutation occurs in a specific temperature range, it may mean that a chemical reaction has occurred between the additives, destroying the stability of the system. For example, some nitrogen-containing intumescent fireproof masterbatch may undergo condensation reaction with the phenolic hydroxyl group in the antioxidant at high temperature, which not only reduces the antioxidant effect, but also may affect the fireproof performance, resulting in a decrease in the material's protective ability in fire scenes.
Mechanical property testing is indispensable. Through mechanical experiments such as tensile, bending, and impact, the mechanical property data of the material after adding a single additive and a compound additive are compared. If the tensile strength, impact toughness and other indicators of the compounded material drop significantly, it means that the compatibility of the additives is poor. For example, in polyethylene terephthalate (PET), if the fireproof masterbatch is poorly compatible with the antioxidant, the force between the PET molecular chains will change, resulting in a significant decrease in tensile strength, affecting the load-bearing capacity of the product in actual use.
When designing a compounding scheme, it is necessary to consider the mechanism of action and synergistic effect of the additives. Antioxidants can inhibit the oxidative degradation of materials and extend their service life. When compounding with fireproof masterbatch, their impact on the flame retardant process should be considered. Some antioxidants are reducing and may interfere with the free radical capture flame retardant mechanism of fireproof masterbatch. At this time, hindered phenolic antioxidants with steric hindrance structures can be used to reduce interference with fireproof performance while exerting antioxidant effects. For example, in high-density polyethylene (HDPE) pipes, compounding hindered phenolic antioxidants with magnesium hydroxide-based fireproof masterbatch can not only improve the material's antioxidant capacity, but also ensure good flame retardant effects, meeting the fireproof and durability requirements of pipes for long-term outdoor use.
The addition of lubricants is intended to improve processing fluidity, but excessive use may weaken the material interface bonding strength. For the fireproof masterbatch system, a lubricant with good affinity for flame retardant components should be selected. For example, in polyvinyl chloride (PVC) wire and cable materials, calcium stearate is used as a lubricant, which can not only reduce the viscosity of PVC melt and improve processing performance, but also work with halogen-containing fireproof masterbatch to enhance the flame retardant and electrical insulation properties of the material.
In addition, the compounding ratio is also crucial. A large number of experiments are required to draw the change curve of material performance under different additive ratios and find the optimal performance ratio range. At the same time, considering the cost factor, the compounding scheme is optimized to reduce the cost of additive use under the premise of meeting performance requirements.
In short, the compatibility test of fireproof masterbatch with other functional additives needs to be carried out from multiple dimensions such as appearance, thermal stability, and mechanical properties. The design of the compounding scheme should comprehensively consider the action mechanism, synergistic effect and cost of the additives. Only in this way can we develop polymer material products with excellent performance and reasonable cost to meet the performance requirements of various industries for materials such as fire resistance, oxidation resistance, and easy processing.
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