3D Printing Materials

Materials for 3D printing

New materials and new printers: the world of industrial production is undergoing a real revolution thanks to 3D printing. If until recently additive printing was reserved for the creation of prototypes or one-off pieces, today we are witnessing the introduction of three-dimensional printers for scale production in the automotive and aerospace sectors, but also in the biomedical field and in 'clothing. Technological evolution has made it possible to speed up and improve the printing process and the new materials make it possible to obtain components that have the same characteristics if not superior to those obtained with traditional molding methods.

Additive technology has the advantage of having unique precision and design flexibility and responds well to the need for customization increasingly demanded by consumers and markets. What needs to be perfected in 3D printing is the ability to obtain a product with the same mechanical and finishing capabilities typical of traditional molding technology. One of the main nodes lies in the materials for 3D printing. It must be remembered that for traditional production there are about 3,000 different types of polymers on the market, including resins, polyurethanes and polyesters, while only about thirty are currently available for 3D printing.

Covestro is working to expand the catalog of materials for digital printing both with an industrial acquisition policy and with research and collaboration projects with machine manufacturers.

We strongly believe in 3D printing because this type of production has high degrees of environmental sustainability because it allows zero kilometer production and eliminates waste. Investing in recyclable materials or bio-based polymers will make the principles of the circular economy more concrete and feasible.

High-tech materials for 3D printing

The main challenges in the field of 3D printing concern on the one hand the costs and on the other hand the availability of materials capable of ensuring the demands for flexibility, hardness, resistance or transparency of existing technologies. Covestro has developed a series of polymers specifically designed for the various additive technologies that combine physical and mechanical characteristics with eco-sustainable properties, the possibility of recycling or biocompatibility. It is a work in close partnership with printer manufacturers to create a synergy between the different types of three-dimensional printing and the materials to be used.

The competitiveness of 3D printers with more sophisticated and faster technologies than the most widespread FDM (filament deposit) make it possible to use advanced materials and improve both the final result and production times. These are laser systems with powder bed fusion (called SLS) or photopolymerization in a tank (SLA) which uses liquid polymers. These two systems are faster and allow complex details and shapes not achievable with classic filament additive printing. The limit of these technologies was the materials because until recently only one type of polymer could be used. It was a high-end material and therefore extremely expensive. Covestro has successfully introduced and experimented with the use of thermoplastic polyurethane (TPU) in powder, liquid or filament form which has demonstrated flexibility and economic competitiveness. Above all, it is possible to create elastic components up to now not obtainable with additive printing.

In addition to the molding of industrial parts, Covestro is studying the use of 3D printing in the application of adhesives. This technique opens up new possibilities for coatings and coatings manufacturers in various industries. With the drop-by-drop application, the overspray phenomenon would be reduced with a consequent reduction in material waste and an increase in safety and quality.

Filaments for additive printing

The Covestro catalog has an extensive range of filaments for 3D printing. Polycarbonate can be mixed in varying quantities with ABS, ASA, or with polyesters such as PET or PBT. The customization of polymer blends can provide perfect materials even for special applications in the medical field or for food use. The thermoplastic polyurethane and the high quality polycarbonate studied in the Covestro laboratories offer high resistance and flexibility in the temperatures of use to be used with different types of printers. The TPU developed by the laboratories has an extraordinary physical behavior in the fusion which results in a high cohesion between the layers. All the characteristics of the TPU are preserved in the additive printing which thus manages to produce components resistant to abrasion, impact, thermally stable and fireproof.

The characteristics of polycarbonates and thermoplastic polyurethanes in 3D printing are:

• versatility: large choice of materials and blends
• hardness: range of hardnesses from Shore 60A to Shore 75D
• solidity: perfect bonding of the layers
• fire resistance
• adaptability: wide variety of melting temperatures.

To complete the range of filaments there are thermally conductive plastics. This is a real revolution in the field of 3D printing applications because this material has the ability to transfer heat like a metal but with the advantages of flexibility, design, properties at the cost of conventional plastic.

Powdered thermoplastic polyurethanes for 3D printing

The powders are used in selective laser synthesizing (SLS) and high-speed synthesizing (HSS) 3D printing processes. In the first method, a laser polymerizes the powder contained in a printing chamber following the drawn model step by step. The second procedure is even faster with an infrared lamp synthesizes layer by layer the polymer on which an ink has been deposited that reproduces the design. HSS printers have a speed of execution that comes very close to industrial printing methods and thus can be the premise for scale production adoption of 3D printing. Covestro's thermoplastic polyurethane powders represent a great advantage for companies that want to take this path. The long molecular chains of the polyurethane developed by the laboratories have a regular casting behavior and an excellent mechanical result as regards good resistance to tearing and abrasion.

TPU powder for 3D printing is:

• ecological: it is almost 100% recyclable
• resistant: to tearing, abrasion, impact
• versatile: cures at different temperatures.

Liquid polyurethanes for 3D printing

The versatility of polyurethane can be exploited in 3D printing called sterolithography (SLA). In this type of printer, a laser or a projector is used to start the photopolymerization process of the liquid polyurethane injected by nozzles or syringes. Due to its cross-linking characteristics, this polymer has isotropic mechanical properties, which gives uniformity and stability to all parts of the molded piece. But other properties such as flexibility, toughness and wear resistance make PU perfect in applications where these physical characteristics are indispensable. Covestro liquid polyurethane has excellent compatibility with isocyanates and polyols in order to obtain customized resins that can respond to different production needs. Liquid polyurethane is perfect if you need:

• fastness and color fastness
• transparency
• customizable resins with specific physical properties
• low shrinkage and printing accuracy
• high resistance to chemical and atmospheric agents.

The applications of 3D printing

The new materials for 3D printing are giving a strong push to the production of components in various industrial sectors. Covestro participates in numerous experimental projects to develop the feasibility of widespread adoption of additive printing with manufacturers.

This technology is invaluable in the case of requests to be met quickly without implementing complex industrial manufacturing lines or where there is a need for strong customization and bespoke production.

In the clothing sector, customizable shoe insoles and other components for technical footwear have been created, but the creation of three-dimensional fabrics for durable and completely recyclable tailored garments is being experimented with.

With thermoplastic polyurethane it is possible to produce bodies for LED bulbs. Due to its lightness and thermal conductivity, the thermally conductive polymer is perfect for the protective shells of the LEDs because it allows the diode not to heat up and therefore to last longer. The same applies to electronic components in the automotive sector which have unbeatable thermal and fireproof characteristics. In the biomedical sector, 3D printing will become indispensable for the possibilities of customization. Covesto has collaborated with its resins to produce hearing aids perfectly adapted to the person. The devices have flexible soft components, resistant to movements and other factors such as creams, sweat, UV rays.