Varieties and Requirements of Masterbatches for 3D Printing Plastic Materials

3D printing technology officially emerged in 1986, but it did not attract attention until the 1990s. Today, products ranging from aerospace components to toys all rely on 3D printing technology. Since 3D printing can produce fully assembled products, it greatly reduces assembly costs. In the future, it may even challenge traditional mass production methods.

The "National Additive Manufacturing Industry Development Promotion Plan" issued by the Ministry of Industry and Information Technology and the Ministry of Finance of China will promote significant development of 3D printing technology in China, with an average annual growth rate of over 30%.

3D printing refers to a manufacturing method driven directly by CAD (Computer-Aided Design) models, capable of producing structures of any complexity. Its core lies in the integration of digital, intelligent manufacturing and materials science, with main features including digitally driven manufacturing and additive manufacturing.

Additive manufacturing, as opposed to traditional subtractive manufacturing, is a technology that creates physical models based on 3D model data by adding material in layers using forming equipment. "It's like building a house, layering bricks to build walls, except instead of bricks and cement, it uses engineering plastics, powders, nylon, photosensitive resins, and even metals and ceramics."

The main 3D printing technologies include Stereolithography (SLA), Fused Deposition Modeling (FDM), and Selective Laser Sintering (SLS), which are the three mainstream processes. Among them, the advantage of SLA is its high precision; SLS is characterized by being much stronger than SLA and is often used to produce structural and functional parts. FDM, on the other hand, produces objects with higher strength and allows for color printing, but the surface of the finished product tends to be rough. The advantages and disadvantages of these three processes can be clearly seen in the diagram below.

In the field of 3D printing, plastic is the most commonly used printing material. The types of commonly used plastics include ABS plastic, polylactic acid (PLA) plastic, nylon and glass fiber-filled nylon, polycarbonate, etc. By mixing these materials in different proportions, nearly 120 new materials with varying degrees of hardness can be produced.

Currently, 3D printing plastic materials are mainly used in Fused Deposition Modeling (FDM) technology.

The Fused Deposition Modeling (FDM) process was developed by American scholars in 1988.

The working principle of FDM is as follows:Under the control of a computer, the heated nozzle moves in the X-Y plane according to the cross-sectional contour information of the product part. Thermoplastic filament material is fed to the hot-melt nozzle by a feeding mechanism, where it is heated and melted into a semi-liquid state. The material is then extruded and selectively deposited on the worktable. After rapid cooling, it forms a thin layer approximately 0.127 mm thick. Once a layer’s cross-sectional shape is completed, the worktable lowers by a certain height, and the next layer of deposition begins, effectively "drawing" the cross-sectional contour layer by layer in this cycle.

The FDM process is clean, easy to operate, does not produce waste, and can be safely used in office environments without the risk of toxic gases and chemical pollution.

In addition to the required material strength, filamentous plastic materials used for FDM processes must also meet the following requirements:

(1) Plastic materials have a low melting temperature, which allows them to be extruded at relatively low temperatures, helping to extend the lifespan of the nozzle and the entire mechanical system; it can also reduce the temperature difference before and after extrusion, thereby decreasing thermal stress and improving the accuracy of the prototype.

(2) Plastic materials have good fluidity. If the fluidity is poor, a high feeding pressure is required for extrusion, which increases the start-stop response time of the nozzle and thus affects forming accuracy.

(3) Good adhesion of plastic materials: The quality of adhesion determines the strength of the part after molding. The interface between layers is often the weakest point in the part's strength. If the adhesion is too low, cracking between layers may occur during the molding process due to thermal stress.

(4) The shrinkage rate of plastic materials is low: the shrinkage rate affects the forming precision of parts in many aspects.

The mainstream materials currently used for fused deposition modeling 3D printers are ABS and PLA.That is, to melt and extrude the color masterbatch and resin into a uniform filament with a diameter of 1.75 mm.

First: Requirements for masterbatch formulation for 3D printing PLA filament

PLA is the English abbreviation for polylactic acid, a biodegradable plastic. Polylactic acid, also known as polylactide, belongs to the polyester family. PLA is a new type of biodegradable material made from starch raw materials proposed from renewable plant resources (such as corn). After use, PLA plastics degrade when buried in soil, with the resulting carbon dioxide directly entering the soil organic matter or being absorbed by plants, rather than being released into the air, thus not causing a greenhouse effect. This achieves a natural cycle in the environment, making it an ideal green polymer material.

Polylactic acid (PLA) has excellent mechanical and physical properties, possessing the best tensile strength and elongation. It also has compatibility with various materials, surface gloss, transparency, and a smooth hand feel, making it widely applicable. The processing temperature of PLA is 170–230°C, so a wide variety of pigments can be chosen, including classic pigments, phthalocyanine pigments, and high-performance pigments. Attention should be paid to pigment dispersibility, ductility, and safety. Since PLA contains ester, hydroxyl, and carboxyl groups in its structure, pigments with corresponding surface properties should be selected.

Second: Requirements for masterbatch preparation for 3D printing ABS materials.

ABS resin is one of the five major synthetic resins, known for its excellent impact resistance, heat resistance, low-temperature resistance, chemical resistance, and electrical properties. It also features easy processing, dimensional stability of products, and good surface gloss. It is widely used in industries such as machinery, automotive, electronics and electrical appliances, instrumentation, textiles, and construction. It is a widely used thermoplastic engineering plastic.

ABS resin is a terpolymer composed of acrylonitrile, butadiene, and styrene.

When formulating 3D printing ABS materials, attention should be paid to the heat resistance, dispersibility, and safety of the pigments. The choice of pigments can be clearly seen from the table below.

Summary:

(1) The so-called 3D printing refers to a category of manufacturing methods driven directly by CAD (Computer-Aided Design) models, capable of completing the fabrication of any complex structures. Its core lies in the combination of digital and intelligent manufacturing with material science, with the main features being digitally driven manufacturing and additive manufacturing.

(2) The main 3D printing technologies include three mainstream processes: Stereolithography (SLA), Fused Deposition Modeling (FDM), and Selective Laser Sintering (SLS).

(3) When preparing FDM 3D printing masterbatch, attention should be paid to the pigment's heat resistance, dispersibility, and safety.