Nylon and polyester are versatile synthetic polymers used widely in various applications. Nylon, a high-strength polyamide, is ideal for bristles, fabrics, ropes, and yarns, although it absorbs water, affecting its stability. Polyester, often PET, is water-resistant and self-extinguishing, commonly used in fabrics.This article delves into the key differences between nylon and polyester, their unique properties, and their respective uses.
What is Nylon?
Nylon, a synthetic thermoplastic within the polyamide family, is engineered through a process involving the reaction of diamines and dicarboxylic acids. Alternatively, it can stem from a self-condensing amino acid or its lactam, featuring the distinctive “CONH” groups arranged in a ring structure. Initially conceived as a substitute for silk, nylon has evolved into a multifaceted material renowned for its exceptional attributes in various industries.
Nylon manifests in diverse grades, with nylon 66, 11, 12, and 46 being predominant variants, delineated by the carbon counts within their polymeric chains. Adhering to the standard nomenclature of PA for polyamide, designations like PA6 or PA6/66 signify its composition. The material commonly presents in black, white, and natural hues, with Nylon 66 reigning supreme in engineering and plastic domains. Its chemical formula, (C12H22N2O2)n, underscores its molecular structure and versatility.From toothbrushes to medical devices and beyond, nylon’s versatility shines in various industries, including engineering, textiles, and healthcare.
Physical Properties
Here are some of its key physical properties:
| Property | Nylon |
|---|---|
| Chemical Structure | Polyamide |
| Density | Typically ranges from 1.12 to 1.15 g/cm³ |
| Melting Point | 210-265°C |
| Tensile Strength | 500-800 MPa |
| Young’s Modulus | 2-4 GPa |
| Elongation at Break | 20-50% |
| Hardness (Rockwell) | R70-R120 |
| Water Absorption | 1.5-9% (24 hours, depending on grade) |
| Coefficient of Friction | 0.3-0.6 |
| Thermal Conductivity | 0.25-0.35 W/(m*K) |
| Specific Heat Capacity | 1.3-1.7 J/(g*K) |
| Dielectric Constant | 3-4 (at 1 kHz) |
| Flammability | Flammable; self-extinguishing |
| UV Resistance | Good |
| Chemical Resistance | Resistant to most chemicals |
Uses
Here are some common uses of nylon:
| Industry | Uses |
|---|---|
| Textiles and Apparel | Clothing (hosiery, swimwear, activewear, outerwear), Ropes and cords |
| Automotive | Engine components, radiator end tanks, timing belts, oil pans, door handles, seat belts, airbag components |
| Consumer Goods | Household items, toothbrush bristles, combs, zippers, kitchen utensils, tennis rackets, fishing lines, parachutes |
| Industrial Applications | Gears, bearings, bolts, nuts, washers, fasteners and fittings |
| Packaging | Food packaging, industrial packaging |
| Medical Devices | Surgical sutures, prosthetic components |
| Electronics | Connectors, electronic components and insulators |
| Construction | Carpet fibers, rugs, plastic screws, anchors, fasteners |
| Aerospace | Lightweight brackets, housings,tubing, clamps, fasteners |
What is Polyester?
Polyester is a type of polymer that belongs to the polyester family. Specifically, it often refers to polyethylene terephthalate (PET), although the polyester family encompasses various other naturally occurring and synthetic chemicals. PET, the most common form of polyester, is synthesized through the reaction of ethylene glycol and terephthalic acid.The term “polyester” can refer to a variety of specific types of polyester polymers, each with unique properties and uses.
Polyester fibers are widely used in fabric manufacturing, either as the sole component or blended with natural fibers to enhance their properties. Polyester fabrics are known for their durability, resistance to wrinkles and shrinkage, and ease of care. They are commonly used in clothing, upholstery, carpets, and other textile applications.
Physical Properties
Tabl list important properties of polyester:
| Property | Polyester |
|---|---|
| Density | 1.38-1.4 g/cm³ |
| Melting Point | 250-260°C |
| Tensile Strength | 22-95 MPa |
| Elongation at Break | 40-600% |
| Young’s Modulus | 1.57-5.2 GPa |
| Flexural Strength | 55-135 MPa |
| Flexural Modulus | 1.38-3.5 GPa |
| Hardness (Shore D) | 71-87 |
| Coefficient of Friction | 0.1-0.6 |
| Thermal Conductivity | 0.15-0.35 W/m·K |
| Specific Heat Capacity | 1.0-1.4 J/g·K |
| Thermal Expansion | 20-100 μm/m·K |
| Electrical Conductivity | <10^-14 S/cm (insulating) |
| Dielectric Constant | 2.4-3.7 |
| Water Absorption | <0.8% (24 hours, 23°C) |
Uses
Here are some common uses of polyester:
| Industry | Uses |
|---|---|
| Textiles and Apparel | Clothing, sportswear, activewear, curtains, bed linens, upholstery |
| Automotive | Seat fabrics, covers, safety belts, airbag fabrics, carpets and floor mats |
| Consumer Goods | Soft furnishings, cushions, pillows, luggage and bags |
| Industrial Applications | Conveyor belts, reinforcement for tires, nonwoven fabrics for filtration and insulation |
| Packaging | Flexible packaging materials, food trays, clamshell packaging, PET bottles and containers |
| Medical Devices | Artificial ligaments and prosthetic components |
| Electronics | Flexible printed circuit boards, cable insulation |
| Construction | Insulation materials |
| Aerospace | – Composite materials for aircraft interiors |
Differences Between Nylon and Polyester
Nylon and polyester are both thermoplastic materials, but polyester compounds can also be thermosetting materials. They are essentially synthetic. The following table lists their main differences.
| Aspect | Nylon | Polyester |
|---|---|---|
| Type | Thermoplastic polymers are commonly known as polyamides | Thermoplastic or thermosetting plastics |
| History | In 1935, Wallace Carothers produced the first nylon | The first polyester fiber, Terylene, was created in 1941 |
| Chemical Structure | Nylon is formed by condensation of copolymers. The method uses equal amounts of dicarboxylic acid and diamine. There are peptide bonds at the end of the monomer | Synthetic polyester consists of dimethyl terephthalate (DMT) or purified terephthalic acid (PTA). |
| Touch | A silky touch | Fibrosus |
| Strength | High tensile strength, abrasion resistance | Strong, durable, resistant to stretching |
| Elasticity | More elastic, stretches before breaking | Less elastic, retains shape better |
| Moisture Absorption | Absorbs moisture, can feel wet | Hydrophobic, dries quickly |
| Breathability | Breathable, allows air circulation | Less breathable, may trap heat and sweat |
| Durability | Resistant to abrasion and tearing | Resistant to stretching and shrinking |
| UV Resistance | Less resistant to UV rays | More resistant to UV rays |
| Chemical Resistance | Resistant to oils and chemicals | Resistant to most chemicals |
| Environmental Impact | Can be recycled, biodegradable options exist | Recyclable, less biodegradable |
| Cost | Generally more expensive, Nylon 6 for molding: $2.0 per kg in bulk. Nylon 6 fiber: $2.3 per kg. | Generally less expensive, Virgin PET granules for molding: $1.5 per kg. Recycled PET granules for molding: $0.9 per kg. |
| Applications | Used in clothing, flooring, automobile molding parts, electrical equipment, etc., packaging film | Used to make a variety of products, including textiles, belts, furniture, insulation, padding, tarps and hardwood gloss finishes |
| Recyclability | Can be recycled into new nylon products | Polyester is recyclable and can be processed into new polyester products through mechanical or chemical recycling methods. |
| Alternative Materials | Fibers, ABS, PET, PBT, PP, POM and HDPE | BOPP, BOPE, PVC, LDPE, ABS, Nylon 6, Nylon 66, Nylon 11, Nylon 12, PP, POM, HDPE, HDPE, LDPE, and PET |
How to Process Nylon and Polyester
Nylon and polyester are two common engineering plastics widely used in manufacturing precision parts. Their processing methods are varied, with the most common being injection molding and CNC machining. Here is a detailed explanation of these methods:
Injection Molding
Nylon and polyester both have high melting points, requiring precise temperature control to ensure material stability and prevent degradation. Nylon typically melts between 220°C and 275°C, while polyester melts between 250°C and 290°C.
Nylon is hygroscopic and must be dried before processing, usually at 80°C to 100°C for 2 to 4 hours, to ensure processing performance and final product quality. Although polyester is less sensitive to moisture, it still needs drying before processing, typically at 120°C for 2 to 4 hours, to ensure product quality.
Mold design must consider the material’s shrinkage rate. Nylon’s shrinkage rate is typically between 1.5% and 2%, whereas polyester’s shrinkage rate is smaller, usually between 0.2% and 0.6%. This means that mold design must be adjusted for the different shrinkage rates of nylon and polyester to ensure the accuracy of the finished product.
Processing Steps:
- Drying the Material: Dry the nylon or polyester pellets at the appropriate temperature.
- Heating and Melting: Feed the dried material into the injection molding machine and melt it to the proper processing temperature.
- Injection: Inject the molten material into the mold.
- Cooling and Solidification: Allow the injected material to cool and solidify in the mold.
- Demolding: Open the mold and remove the finished product.
CNC Machining
Nylon’s hygroscopic nature means it should be dried before machining to ensure dimensional stability and surface quality. Polyester, with its low moisture absorption, does not require special drying treatment. However, both nylon and polyester should be machined using sharp, high-hardness tools (such as carbide tools) to reduce heat generation and surface roughness. Sharp tools effectively lower the heat generated during machining, preventing material deformation.
Additionally, to prevent material deformation and tool overheating during machining, it is recommended to use coolant. Coolant helps reduce machining temperature, preventing nylon and polyester materials from deforming or sticking to the tool at high temperatures.
Processing Steps:
- Material Preparation: Select nylon or polyester sheets or rods of appropriate size and dry them if necessary (especially nylon).
- CNC Programming: Write the CNC machining program based on the part design requirements to ensure precise machining paths and parameters.
- Material Fixation: Secure the material on the CNC machining center’s worktable to ensure stability during machining.
- Machining: Start the CNC machine and perform cutting, drilling, milling, and other machining operations according to the programmed instructions, using coolant to control the temperature.
- Post-Processing: After machining, perform necessary deburring and cleaning to ensure surface smoothness and dimensional accuracy of the parts.
Injection molding is suitable for mass production, while CNC machining is ideal for small batches and high-precision parts. In addition to the above two methods, nylon and polyester are also widely used in the production of 3D parts printed through selective laser sintering (SLS). The 3D printing technology used for producing plastic prototypes has various advantages, such as the production of complex parts, personalized design, and cost-effectiveness in small-scale production.
Conclusion
In summary, this article introduces nylon and polyester, analyzing their characteristics, differences, and application areas. Nylon is widely used in outdoor sports, industrial, and clothing fields due to its strength, toughness, and abrasion resistance, while polyester finds extensive applications in textiles, packaging, and industrial products owing to its durability, ease of maintenance, and lower cost. For more information on nylon and polyester materials, as well as comprehensive parts machining services to meet your prototype and production needs, please contact the BOYI team. Get your free quote now.
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FAQ
Nylon is preferred for applications requiring high mechanical strength due to its excellent tensile strength and impact resistance. It excels in load-bearing components such as gears, bearings, and structural parts subjected to heavy loads and mechanical stress.
Polyester is better suited for applications requiring superior dimensional stability, resistance to moisture, chemicals, and heat. It finds use in precision machining operations where tight tolerances are critical, as well as in environments exposed to harsh chemicals or elevated temperatures, such as chemical processing equipment, storage tanks, and insulation materials.
Both nylon and polyester offer excellent machinability, allowing for precision machining processes such as milling, turning, and injection molding. However, nylon tends to absorb moisture from the environment, affecting its dimensional stability and machinability. Polyester, being less hygroscopic, maintains its dimensional accuracy during machining operations, making it preferred for applications requiring precise tolerances.
Catalog: Materials Guide
This article was written by engineers from the BOYI team. Fuquan Chen is a professional engineer and technical expert with 20 years of experience in rapid prototyping, mold manufacturing, and plastic injection molding.
