Iron oxide pigments are the key coloring materials in the plastics and masterbatch industries. Their temperature resistance and dispersibility directly determine the color of the final products and the stability of the manufacturing process. This article provides professional guidance for plastic manufacturers in selecting these pigments, based on their key properties and applications.
Heat resistant
The core process in plastic processing is high-temperature melting and extrusion. Therefore, heat resistance is the most important criterion for using iron oxide pigments in plastic applications.
The processing temperatures required for different plastics vary greatly:
Common plastics like PE and PP are typically processed at temperatures ranging from 180 to 220°C.
Engineering plastics like PA and PET require a high temperature environment of 260–300°C to be processed.
This requires that iron oxide pigments maintain their chemical stability within the appropriate temperature range, without decomposing, changing color, or migrating.
High-quality iron oxide pigments (especially those of the rutile type that have undergone surface modification or are coated) can withstand long-term exposure to temperatures of 280–300°C. Some of the higher-end products can even maintain their color stability when exposed to temperatures of 320°C for short periods of time.
Two points need to be carefully verified during the purchasing process:
First, regarding thermal stability test data, suppliers are required to provide a Thermal Gravimetric Analysis (TGA) report issued by a third-party testing laboratory. This report must confirm that the decomposition rate of the pigment at the target processing temperatures is below the industry standards.
Secondly, actual processing and sample verification are carried out. The pigments are added to the corresponding plastic substrates in accordance with the production ratios. The materials are then extruded and granulated, or injection-molded. The color difference (ΔE) before and after processing is measured to ensure that there are no color deviations, yellowing, or black spots in the final product.
In addition, heat resistance also directly affects the weather resistance of pigments. Pigments that remain stable during high-temperature processing will be better able to resist fading caused by ultraviolet rays and temperature changes when used in plastic products outdoors over time. This helps prevent problems such as discoloration and uneven coloration in products like plastic pipes, building materials, and automotive interiors.
Dispersion
Dispersion is another key property of iron oxide pigments in plastic/color masterbatch applications. It directly affects the coloring strength of the color masterbatch, the uniformity of the finished product’s appearance, and the smoothness of the manufacturing process. As iron oxide pigments are inorganic powders, poor dispersion can lead to agglomeration during melting and processing. This results in color spots and streaks in the color masterbatch, as well as defects on the surface of plastic products. In severe cases, it can also clog the extruder’s filters, causing production disruptions and waste of raw materials.
There are two key factors that affect dispersion:
Firstly, there’s the particle size and particle size distribution of the pigments. For iron oxide pigments used in plastics, the particle size should be uniformly within the range of 0.1–0.3μm. If the particle size is too large, it becomes difficult to disperse the pigment properly. If the particle size is too small, the pigments tend to agglomerate together.
Second is surface modification. Quality suppliers use silane coupling agents, stearic acid, and similar substances to modify the surface of the pigments. This improves the compatibility between the pigments and the plastic substrate, allowing the powder to disperse quickly and evenly within the molten material.
The verification method is equally important: in addition to reviewing the dispersion test reports provided by suppliers, it’s necessary to conduct actual production tests. After the pigments are converted into masterbatches, their dispersion should be examined under a microscope to ensure that there are no agglomerated particles. Injection molding tests should also be performed to check whether the finished product’s surface has any streaks or color spots, and whether the coloring is uniform. For high-demand applications involving transparent plastics or thin-walled products, even higher standards for dispersion are required. In such cases, it’s necessary to use high-dispersion pigments that have been specially modified to meet the aesthetic requirements of premium products.
Applications
Oxide iron pigments are highly versatile in the fields of plastics and masterbatches, thanks to their non-toxic and environmentally friendly properties, as well as their resistance to weathering and light. They can be used in almost all types of plastics.
In the field of general plastics: pipes, profiles, and injection-molded products made from PE, PP, PVC, etc. Examples include water supply pipes, plastic-steel doors and windows, and household appliance casings. Iron oxide red, iron oxide yellow, and iron oxide black are commonly used for basic coloring and functional modifications.
In the field of engineering plastics: For automotive components and electronic equipment casings made from materials like PA, PET, PC, and ABS, it’s necessary to use modified iron oxide pigments with high heat resistance and excellent dispersion properties. These pigments are ideal for use in high-temperature processing conditions and demanding environmental scenarios.
Color Masterbatch Industry: As a key ingredient in general-purpose color masterbatches, iron oxide pigments can be used to create concentrated color masterbatches that can be directly added by plastic manufacturers. This simplifies the production process and ensures color consistency.
Special applications:** For plastics in contact with food (such as food packaging and tableware), as well as plastic toys for children, it is necessary to use iron oxide pigments that meet food contact standards such as those set by the FDA and EU 10/2011. This ensures safety and compliance with regulatory requirements.
Different application scenarios have varying requirements for pigments: Plastics used outdoors require weather resistance, those in contact with food need to meet regulatory standards, and thin-walled products demand good dispersibility. When purchasing, it’s important to consider the specific usage of one’s products and select the appropriate type of iron oxide pigment accordingly.
Target customers
Plastic manufacturers are the key customers for iron oxide pigments in the field of plastics/color masterbatches. This includes three main categories: general plastic processing plants, engineering plastic modification plants, and color masterbatch manufacturers. Different types of plastic manufacturers have significantly different requirements for iron oxide pigments.
General plastic processing plants: Emphasize cost-effectiveness and color stability. Prefer standard models that are resistant to heat and easy to disperse, to meet the needs of mass production.
Engineering plastic modification plants: The key requirements are high temperature resistance and good dispersion, to enable processing at high temperatures. Additionally, it’s important that the pigments do not affect the mechanical properties of the plastic.
Color masterbatch manufacturers: High requirements are placed on the coloring power, dispersibility, and batch stability of pigments. It’s necessary to use modified products with high purity and fine particle size to ensure uniform and consistent coloring in the color masterbatch.
For plastic manufacturers making purchases, price alone should not be the sole criterion for selection. A comprehensive evaluation system is necessary. In addition to two key properties: temperature resistance and dispersibility, it’s also important to assess the supplier’s ability to maintain consistent product quality across batches, their compliance with regulations, and their level of technical support. Quality suppliers can offer customized surface modification services to optimize pigment performance across different plastic substrates. They can also provide services like sample development, color matching, and process optimization. All these help plastic manufacturers improve product quality and reduce production costs.
Conclusion
The temperature resistance and dispersibility of iron oxide pigments are crucial factors in the processing of plastics and masterbatches. Selecting the right pigment based on the specific application is key for plastic manufacturers to improve product quality and ensure stable production.
If you need high-temperature-resistant and highly dispersed iron oxide pigments suitable for plastic processing, please contact us to obtain free samples and customized color-matching solutions!
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