Metal replacement: why replace metals with polymers and composites?
What is metal replacement?
Metal replacement is the substitution of metals with polymers. This procedure was made possible with the advent of high-performance polymers and composites that, thanks to their high mechanical properties and excellent temperature resistance, enabled new possible applications.
The world of materials is a broad universe, and every material family has its unique properties. The different materials sets are metals, polymers, ceramics, and composites. Materials are chosen depending on the application, the industry, and the operating conditions.
Metal VS Polymers, what is the difference?
A metal is a high mechanical resistance material that can reflect light and conducts heat and electricity. They are characterized mainly by crystalline bonds. Typically, metals can be attacked by acids and bases and in some cases by water as well. They are fusible when subjected to heat and are malleable or ductile, allowing different manufacturing methods. Their main disadvantages might be electrical and thermal conductivity and high weight.
Why are polymer-based materials replacing metals?
A polymer is a material consisting of very large molecules, or macromolecules, composed of many repeating subunits. Polymer properties depend on their structure. For instance, thermoplastics become moldable at a certain elevated temperature and solidify upon cooling. Among the major characteristics of plastics, there is ease of processing, along with cost-effectiveness, thermal, electrical, acoustic, and vibration insulation, corrosion, and chemical resistance.
Can metal be replaced?
The age of metals began eight thousand years ago (6000 BC) when humans learned to melt copper. Since then, metals have been increasingly used for production. The history of plastic is more recent as it was discovered a bit more than one century ago. The first polymers to be found were thermosets and standard polymers, like Xylonite, when metal replacement started but was mainly focused on consumer goods due to the lower costs of plastics. In industrial environments, substituting metals with polymers was an enormous challenge, given the low mechanical properties of standard polymers.
Only lately, with the advent of high-performance polymers and composites, has the world started to think about replacing metals in challenging applications.
High performance polymers are thermoplastic polymers with high mechanical, thermal and chemical performance with innumerable uses. In fact, they can replace metals such as bronze, brass, stainless steel and aluminum alloys.
Among the main advantages for metal replacement, there are:
- weight reduction
- chemical resistance
- improved material performances.
But what happens when metal replacement meets a disruptive technology such as 3D printing? Let’s check out the main advantages.
3D metal printing: advantages of metal replacement
Roboze technology, with its high-performance polymers and composites, combines the advantages of metal replacement with the advantages of additive manufacturing technology. It results in increased process productivity and lower production costs.
When substituting traditional manufactured metals with 3D printed polymers and composites, one should expect the following advantages:
- Maintain and optimize the mechanical, thermal, and chemical characteristics required by the metal project.
- Improve the dielectric and insulation characteristics.
- Reduction of vibrations and noise.
- Weight reduction, mainly due to the change in density (more than a 50% reduction). Metals are heavier than polymers, meaning that their supply, operation, and transportation costs are higher. Lighter products are more ergonomic as well, improving the safety of workers.
- Lower production costs.
- Lower lead time.
- Greater geometric design freedom and flexibility that improve the efficiency of the parts.
- Lower volatility of raw material costs.
- Reduction of waste material due to the deposition of the material to use only.
Advantages of metal replacement with Roboze: why are polymer-based materials replacing metals?
The metal replacement era has just begun: with 3D printed high-performance polymers and composites, substituting metals is easier than ever. PEEK, Carbon PEEK and Carbon PA are the best materials to enable metal replacement. Metals are known to be tough, durable and to survive at very high temperatures. For sure not everything that is done in metal today can be replaced by non-metallics. However, in more and more industrial applications, polymers and composites are used to replace metals, leading to impressive benefits.
Here are the advantages of high-performance polymers and composites compared to metals:
- Thermal, electrical, and acoustic insulation of polymers and composites
Metals are known to be electrically and thermally conductive. Their volume resistivity is usually lower than 10-5 Ohm/cm and their thermal conductivity may range up to 400 W/(m*K) for copper. On the other hand, the volume resistivity of polymers is generally between 1012 and 1019 Ohm/cm, while the thermal conductivity is around 0.43 W/(m*K) for PEEK. Composites may have lower values of volume resistivity and higher values of thermal conductivity compared to plastics, due to the conductivity of carbon fibers. Handling components at high temperatures might be a risk for the workers in the shopfloor. At the same time, handling electrically conductive parts might also harm the workers’ safety, due to discharges and electric shocks. Having polymers instead of metals results in safer handling for any component, either at high temperatures or at high voltages.
- Lightweight of polymers and composites
The density of metals varies in a broad range: for aluminum alloys it is around 2,7 g/cm3, for stainless steel 8 g/cm3, for brass around 8,7 g/cm3. Polymer density is very low, generally at least half compared to metals, ranging around 0,9 to 1,5 g/cm3. For instance, PEEK is 84% lighter than SS316 and 52% lighter than Aluminum 6063. Some industries, like aerospace and transportation, push for the weight reduction of their components because it results in an increase of the range or the reduction of fuel consumed. For instance, the price of sending 1 kg of payload with SpaceX’s Falcon 9 launcher is about $2720. Imagine how much can be saved just by reducing the parts weight.
- High mechanical resistance of polymers and composites
Metals used in the industry are known to have very high mechanical properties. With the development of new composites, mainly reinforced with Carbon fibers, the ultimate tensile strength has seen enormous improvements. For instance, Roboze Carbon PEEK can have a UTS up to 138 MPa, that is even higher than that of some aluminum alloys like Aluminum 6063 (UTS of 130 MPa). This allows Carbon PEEK and Carbon PA to fully substitute Aluminum in the manufacturing industry.
- High specific strength of polymers and composites
The specific strength is calculated as the ratio between the ultimate tensile strength and the density of any material. Metals have generally high mechanical properties but a high density as well. On the other hand, high-performance polymers and composites have fairly high mechanical properties and low density, resulting in very high specific strength. This is the case of Carbon PA, a composite material that has a specific strength of 98,6 MPa*cm3/g - more than double the specific strength of Aluminum 6063 and almost one third higher than Stainless Steel 316.
- High temperature resistance of polymers and composites
Common industrial metals are known to melt at very high temperatures. General polymers don’t resist well to temperatures higher than 212°F /100°C. With the spread of high-performance polymers and composites, the continuous use temperatures have risen to reach up to 536°F/280°C. This property enables the use of these materials for a wider range of temperature that was thought to be only for metals so far.
- Chemical and corrosion resistance of polymers and composites
Corrosion is a terrible issue for metals. It not only causes damage, it also reduces the efficiency of a product that must be replaced more frequently. On the contrary, polymers can be resistant to a wide range of chemicals, both acids and bases, having a longer lifespan. That is the example of PEEK and its composites that are extremely resistant to a broad range of chemicals, for instance: fuels, lubricants, hydrogen, chlorine, seawater, ammonium nitrate, and many more.
Metal replacement applications: how to identify a part for metal replacement
Many more applications can be enabled by the replacement of metals with high-performance polymers and composites. Here is a short guideline on how to understand whether metal replacement is suitable for your application:
- Operating temperature below 572 °F / 300 °C.
- Low to medium loads, UTS needed below 140 MPa.
- Highly corrosive environment, e.g., Oil&Gas sector.
- Mass-critical applications, e.g., aerospace applications.
- Request for insulating parts, e.g., electrical industry.
What can be used instead of metal? Some examples
The metals that are more often replaced by polymers are aluminum, stainless steel, and brass. Reach out to our team of engineers to check if your metals can be replaced by our high-performance polymers and composites. Here are some examples of metal replacement applications:
- Metal Replacement in marine industry: brass is widely used in the marine industry, despite its high weight, because it is easy to machine and it is resistant to seawater and antibacterial - meaning that its good chemical resistance doesn’t allow bacteria and algae to grow on it. Thanks to the chemical resistance towards seawater, PEEK and Carbon PEEK can substitute brass. One recent case study shows the 3D printing of a Carbon PEEK gear that substitutes leaded brass in the marine environment.
- Metal Replacement in the manufacturing industry: the applications focus more on fair mechanical resistance of the parts at a low cost and low weight; therefore, aluminum is widely utilized. Thanks to its outstanding mechanical properties, having an Ultimate Tensile strength up to 138 MPa, Carbon PA can substitute aluminum jigs and fixtures on any shop floor. That’s the case of drilling jigs, usually manufactured in Aluminum, that are replaced by Carbon PA.
- Metal Replacement in the chemical industry: stainless steel is famous for having good chemical resistance, hence its use in the chemical industry. Substituting it with PEEK and Carbon PEEK, due to their superlative chemical resistance, allows for massive weight reduction and subsequently, improved ergonomics. For instance, stainless steel can corrode if in contact with chloride, hydrochloric acid, acetic acid, or hydrogen sulfide while PEEK would resist unscratched in these environments.