What Are Polyamides?
A polyamide is a polymer with repeating units linked by amide bonds.
Polyamides occur both naturally and artificially. Examples of naturally occurring polyamides are proteins, such as wool and silk.
Artificially made polyamides can be made through step-growth polymerization or solid-phase synthesis yielding materials such as nylons, aramids, and sodium polyaspartate.
Synthetic polyamides are commonly used in textiles, automotive industry, carpets, kitchen utensils and sportswear due to their high durability and strength.
The transportation manufacturing industry is the major consumer, accounting for 35% of polyamide (PA) consumption.
Some examples of natural polyamides include wool, silk, collagen, and keratin. Synthetic polyamides can be broken down into three categories:
- Aliphatic Polyamides: This category also includes many grades of nylon such as Nylon 6 and Nylon 6/6.
- Aromatic Polyamides: Also known as aramids, this category is preferred by many Xometry users to create fibers such as Nomex (used in fire-resistant fabrics), and Kevlar (known for its use in the construction of bullet-resistant vests).
- Semi-Aromatic Polyamides: These high-performance engineering polymers, also known as polyphthalamides or PPA, have impressive high-temperature properties. Some of these include Rislan or Zytel, which is a material Xometry offers with its quick-turn injection molding service.
The molecular structure of polyamides can vary greatly, i.e., aliphatic polyamides like Nylon are polymerized from monomers like caprolactam and hexamethylenediamine.
Aromatic polyamides, on the other hand, are polymerized from para-phenylenediamine and terephthaloyl chloride.
Polyamides possess high tensile strength. Their name alone refers to a range of different materials, some of which can be woven into fibers, cast, or injection molded.
Nylon 6, for example, is an aliphatic polyamide that has a tensile strength of about 40MPa.
Kevlar 29 is an aromatic polyamide that has a tensile strength of 3600 MPa. This considerable difference is because of the huge range of materials in the polyamide group.
Uses of Polyamides
Synthetic polyamides are commonly used in textiles, automotive industry, carpets, kitchen utensils, and sportswear due to their high durability and strength.
The transportation manufacturing industry is the major consumer, accounting for 35% of polyamide (PA) consumption.
The applications of polyamides include:
#1. Textiles and Fibers.
Textiles and fibers are one of the first applications of polyamides. Fibers are long, thin extrusions of polyamide that can then be woven into a textile for clothing, bedding, upholstery, curtains, and carpets.
#2. Engineering Plastics.
Engineering plastics are broadly defined as plastics that have better-performing properties than more widely used plastics.
In the case of polyamides, these properties are good wear resistance, high strength, chemical resistance, and impact resistance.
These better properties mean polyamides are used for helmets, bearings, supports, piping, and protective equipment.
#3. Automotive Industry.
Polyamides are used in the automotive industry for their lightweight, low-cost, and good mechanical properties.
Specific automotive applications include engine air intakes, engine covers, pulley tensioners, fuel lines, fuel pumps, lights, and vehicle trim.
#4. Electrical and Electronics.
For a long time, polyamides have been the material of choice for electrical connectors.
This is because electrical connectors and other non-conductive electrical parts require high heat resistance, which polyamide can offer.
Polyamide is also chosen due to its low cost, easy formability, high strength, and electrical insulation properties.
#5. Filaments for 3D Printing.
A polyamide 3D printing filament takes the form of a spooled wire which is fed into a 3D printer to be processed into a part.
The polyamide filament then melts and turns into a liquid state which is then extruded out of the printhead and solidified on the print bed.
How to Identify Polyamides
There are also many different polyamide copolymers that can be identified in a simple manner like polyamides. But it is not always possible to make a full sign.
The polyamide can also be identified by a color reaction with p-dimethylaminobenzaldehyde.
The best way to identify a polyamide is by using a datasheet, but if there isn’t one available, the next best thing would be to send a sample to a lab for destructive testing.
It’s almost impossible to use the naked eye to identify a polyamide, as they typically include such a wide range of different materials.
A factor that makes visual identification even harder, is the fact that polyamides have no distinctive visual characteristics. Furthermore, they can either be stranded or molded.
Speaking of molded polyamides, some, like Nylon, are typically thermoplastics.
This means that when heated up to a certain temperature, they will soften, and then become solid again when cooled down.
Other polyamides like Nomex, though, have high-temperature resistance. Some are even classified as thermosets, which means they’re impossible to test by thermal testing.
Another way to potentially identify a polyamide is by calculating its density. This method, however, may not be precise enough to fully determine the grade of the polyamide.
A further identification method could be property testing. If one decides to go down this route, the samples would need to be prepared and tested according to the latest and most relevant standards, allowing the comparison with supplier values to be accurate and precise.
What is Nylon?
Nylon is a family of synthetic polymers with amide backbones, usually linking aliphatic or semi-aromatic groups.
Nylons are white or colorless and soft; some are silk-like. They are thermoplastic, which means that they can be melt-processed into fibers, films, and diverse shapes.
The properties of nylons are often modified by blending with a wide variety of additives.
Many kinds of nylon are known. One family, designated nylon-XY, is derived from diamines and dicarboxylic acids of carbon chain lengths X and Y, respectively.
An important example is nylon-6,6 (C₁₂H₂₂N₂O₂). Another family, designated nylon-Z, is derived from amino carboxylic acids with carbon chain length Z.
Nylon polymers have significant commercial applications in fabric and fibers (apparel, flooring and rubber reinforcement), in shapes (molded parts for cars, electrical equipment, etc.), and in films (mostly for food packaging).
Uses of Nylon
- Clothing: Shirts, Foundation garments, lingerie, raincoats, underwear, swimwear and cycle wear.
- Industrial uses: Conveyer and seat belts, parachutes, airbags, nets and ropes, tarpaulins, thread, and tents.
- It is used to make a fishnet.
- It is used as plastic in manufacturing machine parts
How to Identify Nylon
Like other polyamides, the best way to identify nylon is to use a datasheet or send a sample to a lab for destructive testing.
Nylon doesn’t have any distinguishing visual properties, so without using specialized techniques or equipment, it can be very difficult to identify.
For instance, nylon can be quite smooth to the touch, but then again, so are other polymers like PTFE.
Another way to potentially identify if a material belongs to the nylon category is by testing its melting point or density, but this won’t provide enough information to determine which grade of nylon the material belongs to.
Some nylon grades are even created by blending other grades together, making them even harder to identify. This is why sending a sample to a lab will prove to be the best option.
Differences Between Polyamides and Nylons
| Basis of comparison | Nylon | Polyamide |
| Define | They are the thermoplastic polyamide polymers, which are a family of extremely durable synthetic materials that are mostly utilized in fibers. | A form of synthetic polymer that is created by joining an amino group from one molecule and a carboxylic acid group from another, used to make numerous synthetic fibers like nylon. |
| Which type of fiber? | Synthetic fiber | Natural or synthetic fiber |
| Strength | They are stronger than polyamide due to its high melting point, which enables it to be stretched to its full length without breaking. | They are less strong than nylon as polyamide has a lower melting point and is less resilient to stretching when stressed. |
| Durability | More durable compared to polyamide. | Less durable compared to nylon. |
| Resistance | These fibers provide more resistant against rain and moisture. | These fibers provide less resistant against rain and moisture. |
| Abrasion-resistant | More resistant compared to polyamide. | Less resistant compared to nylon. |
| Chemical structure | They are symmetrical and very polar. | Their symmetry and polarity depend upon the structure of amides. |
| Identification | Through testing its melting point and density. | Through lab testing. |
| Flammability | This type of fiber melts easily. | This type of fiber melts while burning. |
| Static electricity | It generates more static electricity as compared to polyamides. | It generates less static electricity as compared to nylon. |
| What temperature the fiber can handle? | 121° F | 200° C |
| Uses | Clothing (Dresses, stocking, etc ), ropes, tents, etc. | Clothes (Shirts, pants, etc), bottles, bedsheets, etc. |
Similarities Between Nylon and Polyamide
- Both fibers are polymers.
- Both are breathable fibers.
- Both fibers can be synthetic.
- Both fibers are durable.
- Both fibers have high strength.
- Both fibers are used in consumer products.
Common Properties of Polyamides and Nylon
#1. Tensile Strength and Durability.
Both polyamides and nylon possess striking rigidity, making them appropriate for applications requiring materials to withstand high stress or impacts. This property has contributed to their far-reaching use.
#2. Protection from Wear and Impact Resistance.
One of the most striking qualities of polyamide and nylon is their astounding protection from wear and impact resistance.
This element makes them ideal material choices for applications that include steady friction and contact with harsh surfaces, like pinion wheels, orientation, and transport lines.
#3. Chemical Resistance.
Polyamides, by and large, display excellent protection from different synthetic compounds, oils, and solvents, albeit the degree of this obstruction shifts depending upon the particular kind and exposure duration.
This property has propelled their use in assorted modern settings where openness to cruel synthetic compounds is desirable.
#4. Water Resistance.
While nylon and polyamides possess good water resistance, nylon demonstrates higher water ingestion, in contrast with different polyamides.
This can be beneficial in specific applications, though it might present difficulties in others.
For instance, nylon fishing lines are designed to absorb water and perform better when they do absorb water; they lose their buoyancy so they can sink.
#5. Melting Point.
Different types of polyamides and nylons generally have varying melting points depending on their specific chemical compositions.
That being said, some types of nylon may have a lower melting point than certain polyamides due to differences in the length of their molecular chain.
For example, nylon-6 has a lower melting point than nylon-6.6 due to its shorter molecular chain length.
However, other types of polyamide may have lower melting points than some types of nylon.
Ultimately, a given polymer’s melting point is determined by various factors, including its molecular weight, crystallinity, and chemical structure.