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Polymer vs. Metal: What Are the Differences?

Learn more about the differences betwen these two materials in manufacturing.

Xomety X
By Team Xometry
April 15, 2023
 11 min read
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Engineers and materials scientists often face the choice between polymer vs. metal for their work. Both classes of materials have unique properties and applications. In contrast to polymers, which are large molecules made up of repeating units, metals are naturally crystalline and composed of metallic elements. Polymers are useful in many applications, such as packaging materials and medical implants. Metals, on the other hand, are necessary for industries like construction and electronics due to their conductivity and strength. Due to fundamental structural differences, these materials have different mechanical, electrical, and thermal properties. This article will discuss each material's advantages, traits, and applications as well as how they differ.

What Is Polymer?

A polymer is a large molecule made of repeated monomers. Chemical bonds connect these units, which can be natural or synthetic, to create long chains. Natural polymers include things like silk, proteins, and DNA whereas plastics and synthetic rubber are made of synthetic polymers. Polymers are useful in a wide range of applications due to their diverse range of physical and chemical properties.

What Is Polymer Made Of?

Polymers are made up of monomers — small molecules that can interact chemically to form long chains or networks. Most are based around hydrocarbon molecules, meaning that carbon and hydrogen are central to their structure. Diverse monomers, including proteins, plastics, and rubbers, can be used to create these chains, which can be linear, branched, or cross-linked.

What Is the Importance of Polymers?

Polymers play a significant role in most modern industries, including: packaging, textiles, electronics, and medicine. Affordability, portability, durability, and design flexibility are some of their advantages. Some polymers are biodegradable and thus contribute to sustainability efforts by reducing waste and energy use during manufacturing processes.

What Are the Properties of Polymer?

Among the distinctive characteristics of polymer materials are:

  1. High Strength and Toughness: Some polymers, like polyethylene (PE), have excellent mechanical characteristics, including high strength, toughness, and stiffness. Their molecules are composed of lengthy molecular chains that can entangle and withstand deformation.
  2. Low Density: Polymers are perfect for applications that call for weight minimization because they are typically lighter and less dense than metals and ceramics.
  3. Good Thermal and Electrical Insulation: Polymers are effective insulators for both electrical and thermal applications because of their low conductivity.
  4. Chemical Resistance: Many polymers are highly resistant to some chemicals that would degrade other materials. They are perfect for use in harsh chemical environments.
  5. Biocompatibility: Some polymers can be used for drug delivery systems and medical implants because they are biocompatible.

What Is the Structure of Polymer?

The large molecules known as polymers are made up of monomers, or repeating structural units, linked together by covalent bonds. This basic repeating structure is a property that all polymers share. Note, though, that each polymer's structure can differ considerably depending on the monomers used and the polymerization conditions.

What Is the Advantage of Polymer Compared to Metal?

Compared to metals, polymers have many benefits, including:

  1. Low Weight: Polymers are the best choice for applications that call for minimal weight because they are lighter than metals.
  2. Corrosion Resistance: Polymers do not corrode in the way metals do, which makes them suitable for use in harsh environments.
  3. Insulation: Polymers are helpful in electrical applications because they are effective heat and electricity insulators.
  4. Design Flexibility: Polymers can be molded into intricate shapes, increasing design flexibility.

What Are Examples of Polymers?

Polymers can be found in a wide range of goods and materials, such as: plastics, fibers, adhesives, and coatings. Here are a few examples of polymers:

  1. Polyethylene: This is one of the most common plastics, making up products like plastic bags, water bottles, and food containers. Repeated ethylene monomers make up versatile polyethylene chains. 
  2. Polystyrene: This is used to create items like foam cups, packaging, and toys. Styrene monomers are joined repeatedly to create the polystyrene structure.
  3. Polyvinyl Chloride (PVC): This plastic is utilized in products like electrical cables, medical equipment, and building materials. Vinyl chloride monomers are the building blocks for the polymer known as PVC.

What Is Metal?

Metal is a substance composed primarily or entirely of metallic elements. Metals are usually hard, shiny, malleable, ductile, and conductive. Examples are: iron, copper, aluminum, and gold. Due to their strength, durability, and other desirable qualities, they are widely used in manufacturing, construction, transportation, and other industries. For more information, see our guide on Metal.

What Is Metal Made Of?

Metals are made up primarily or entirely of atoms that the periodic table of elements categorizes as metallic. Metallic elements are common in the crust of the Earth.

What Is the Importance of Metals?

Metals are valuable because of their distinctive physical and chemical characteristics, which make them necessary in many applications. They are strong and resilient, excellent heat and electricity conductors, and easily moldable. Metals are employed in nearly every field of manufacturing, including construction, transportation, electronics, and medicine.

What Are the Properties of Metal?

The properties of metals include:

  1. High Electrical Conductivity: Metals are excellent conductors of electricity, which makes them essential in electrical wiring and circuitry.
  2. High Thermal Conductivity: Metals also conduct heat well, making them important in heating and cooling systems.
  3. High Ductility: Metals can be stretched and shaped without breaking, allowing metal items to be manufactured in various forms and shapes.
  4. High Malleability: Metals can be easily hammered, pressed, or rolled into thin sheets or other shapes without breaking.
  5. High Melting and Boiling Points: Most metals have high melting and boiling points, which makes them useful in high-temperature applications.

What Is the Structure of Metal?

A crystal lattice, or closely packed arrangement of atoms in a regular pattern, is what distinguishes metal from other crystalline solids. Metallic bonds, which entail the delocalization of electrons over a significant number of atoms, hold atoms together. Thermal and electrical conductivity, ductility, and malleability are natural consequences of such bonds. 

What Is the Advantage of Metal Compared to Polymer?

Metals have several advantages over polymers, including:

  1. Strength and Durability: In general, metals are far stronger than polymers. They are resistant to degradation and breaking at higher temperatures, pressures, and loads.
  2. Conductivity: Compared to polymers, metals have superior thermal and electrical conductivity, making them the best choice for applications requiring heat dissipation or electrical conductivity.
  3. Hardness: Metals can withstand wear and tear better than polymers because they are typically harder materials. This is a result of the metals' intermolecular structure which produces potent interatomic forces that resist deformation.
  4. Resistance to High Temperatures: Polymers cannot withstand high temperatures as well as metals. Metals’ melting points are typically much higher than those of polymers. 

What Are Examples of Metals?

Here are some examples of metals:

  1. Iron: Iron is a typical metal that has been used in construction, tools, and weapons for millennia. It is a crucial component of steel, which is one of the modern world’s most fundamental structural materials. 
  2. Aluminum: Aluminum is a strong, lightweight metal that can be used for a variety of things, including electronics, construction, and packaging. It is also a vital component in the production of aircraft due to its favorable strength-to-weight ratio.
  3. Gold: For thousands of years, people have prized gold as a precious metal because of its beauty and scarcity. It serves as a store of value and appears in coins and jewelry. Gold is also used in electronics and medical equipment due to its excellent conductivity and biocompatibility.

Which Is Better, Polymer or Metal?

Your decision between polymer or metal depends on the specific application and context, so there is no clear-cut answer. Both material categories have distinctive qualities, benefits, and drawbacks. For instance, metals are sturdy and long-lasting while polymers are lightweight and corrosion-resistant. In the end, the decision over which to use should be based on the demands and limitations of the application.

Is a Polymer a Metal?

No, a polymer is not a metal. Polymers have large molecules made up of repeating subunits. While metals are usually used for structural purposes or as conductors of electricity and heat, polymers end up in things like plastics, fibers, and adhesives.

Is Polymer Stronger Than Metal?

It depends on the specific metal and polymer under comparison. As a general rule, metals are usually stronger. In terms of tensile strength and stiffness, some polymers — like Kevlar® and carbon fiber-reinforced polymers — can be stronger than certain metals. Metals are better suited for applications that call for high toughness and durability, such as in structural and aerospace engineering.

Is Polymer Cheaper Than Metal?

The relative prices depend heavily on the properties you expect out of the material. The production of polymers is typically less expensive than that of metals, though high-performance polymers can sometimes be more expensive than some metals. Cost can also be impacted by factors like the manufacturing process and volume.

Do Polymers Break Down Easily?

This depends upon the specific type of polymer and the environment to which it is exposed. While some polymers, like polylactic acid, can degrade relatively quickly when exposed to heat and moisture, others, like polyethylene, can take hundreds of years to degrade in the environment.

What Is the Difference Between Polymer and Metal in Terms of Tensile Strength?

Metals typically have higher tensile strengths than polymers due to their crystalline structure and metallic bonding. This allows for a more effective distribution of stress throughout the material. However, some high-strength polymers, like carbon-fiber-reinforced polymers, can match the strength of some metals. For more information, see our guide on Tensile Strength.

What Is the Difference Between Polymer and Metal in Terms of Weight?

Since polymers typically have a lower density than metals, they weigh less per unit of volume. However, each particular type has its density, so it’s best to compare specific materials against one another rather than depend upon this generalization. 

What Is the Difference Between Polymer and Metal in Terms of Hardness (Durometer)?

In comparison to metals, polymers typically have a lower durometer hardness rating. Metals are typically harder because of their crystalline structure and metallic bonding, though the hardness of polymers can vary depending on their specific composition and processing. For more information, see our guide on Durometer (Hardness).

What Is the Difference Between Polymer and Metal in Terms of Chemical Structure?

Monomer-repeating units called polymers are joined together most often by covalent bonds. By contrast, metallic bonds, which involve the sharing of delocalized electrons, hold a lattice of atoms together to form metals. The physical and chemical characteristics of metals and polymers differ due to this fundamental difference in chemical structure.

What Is the Difference Between Polymer and Metal in Terms of Application?

Polymers are synthetic materials that are lightweight, flexible, and have good insulating properties. Consumer goods, textiles, and packaging are just a few examples of their uses. On the other hand, metals are strong, long-lasting substances that frequently get used in the building, manufacturing, and transportation sectors.

What Is the Difference Between Polymer and Metal in Terms of Ductility?

Polymers are typically less ductile than metals due to their weaker intermolecular bonds, leading to limited plastic deformation and eventual fracture. The metallic bonding of metals, on the other hand, makes them highly ductile, allowing atoms to dislocate and move plastically. Metals are often able to deform predictably before they fracture. For more information, see our guide on Ductility.

What Is the Difference Between Polymer and Metal in Terms of Production?

When monomers are joined to form long chains through the process of polymerization, a material known as a polymer is created. In contrast, metals are created by mining and refining earthbound ores, which are then melted and shaped as desired using casting, forging, or extrusion techniques.

Summary

This article presented polymers vs. metals, explained what each is, and discussed the various differences between them in manufacturing. To learn more about polymer vs. metals, contact a Xometry representative.

Xometry provides a wide range of manufacturing capabilities and other value-added services for all of your prototyping and production needs. Visit our website to learn more or to request a free, no-obligation quote.

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Xomety X
Team Xometry
This article was written by various Xometry contributors. Xometry is a leading resource on manufacturing with CNC machining, sheet metal fabrication, 3D printing, injection molding, urethane casting, and more.