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Comparing Nylon and Polyester: Key Differences and Uses

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.

nylon and polyester

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:

PropertyNylon
Chemical StructurePolyamide
DensityTypically ranges from 1.12 to 1.15 g/cm³
Melting Point210-265°C
Tensile Strength500-800 MPa
Young’s Modulus2-4 GPa
Elongation at Break20-50%
Hardness (Rockwell)R70-R120
Water Absorption1.5-9% (24 hours, depending on grade)
Coefficient of Friction0.3-0.6
Thermal Conductivity0.25-0.35 W/(m*K)
Specific Heat Capacity1.3-1.7 J/(g*K)
Dielectric Constant3-4 (at 1 kHz)
FlammabilityFlammable; self-extinguishing
UV ResistanceGood
Chemical ResistanceResistant to most chemicals

Uses

Here are some common uses of nylon:

IndustryUses
Textiles and ApparelClothing (hosiery, swimwear, activewear, outerwear), Ropes and cords
AutomotiveEngine components, radiator end tanks, timing belts, oil pans, door handles, seat belts, airbag components
Consumer GoodsHousehold items, toothbrush bristles, combs, zippers, kitchen utensils, tennis rackets, fishing lines, parachutes
Industrial ApplicationsGears, bearings, bolts, nuts, washers, fasteners and fittings
PackagingFood packaging, industrial packaging
Medical DevicesSurgical sutures, prosthetic components
ElectronicsConnectors, electronic components and insulators
ConstructionCarpet fibers, rugs, plastic screws, anchors, fasteners
AerospaceLightweight 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:

PropertyPolyester
Density1.38-1.4 g/cm³
Melting Point250-260°C
Tensile Strength22-95 MPa
Elongation at Break40-600%
Young’s Modulus1.57-5.2 GPa
Flexural Strength55-135 MPa
Flexural Modulus1.38-3.5 GPa
Hardness (Shore D)71-87
Coefficient of Friction0.1-0.6
Thermal Conductivity0.15-0.35 W/m·K
Specific Heat Capacity1.0-1.4 J/g·K
Thermal Expansion20-100 μm/m·K
Electrical Conductivity<10^-14 S/cm (insulating)
Dielectric Constant2.4-3.7
Water Absorption<0.8% (24 hours, 23°C)

Uses

Here are some common uses of polyester:

IndustryUses
Textiles and ApparelClothing, sportswear, activewear, curtains, bed linens, upholstery
AutomotiveSeat fabrics, covers, safety belts, airbag fabrics, carpets and floor mats
Consumer GoodsSoft furnishings, cushions, pillows, luggage and bags
Industrial ApplicationsConveyor belts, reinforcement for tires, nonwoven fabrics for filtration and insulation
PackagingFlexible packaging materials, food trays, clamshell packaging, PET bottles and containers
Medical DevicesArtificial ligaments and prosthetic components
ElectronicsFlexible printed circuit boards, cable insulation
ConstructionInsulation 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.

AspectNylonPolyester
TypeThermoplastic polymers are commonly known as polyamidesThermoplastic or thermosetting plastics
HistoryIn 1935, Wallace Carothers produced the first nylonThe first polyester fiber, Terylene, was created in 1941
Chemical StructureNylon 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 monomerSynthetic polyester consists of dimethyl terephthalate (DMT) or purified terephthalic acid (PTA).
TouchA silky touchFibrosus
StrengthHigh tensile strength, abrasion resistanceStrong, durable, resistant to stretching
ElasticityMore elastic, stretches before breakingLess elastic, retains shape better
Moisture AbsorptionAbsorbs moisture, can feel wetHydrophobic, dries quickly
BreathabilityBreathable, allows air circulationLess breathable, may trap heat and sweat
DurabilityResistant to abrasion and tearingResistant to stretching and shrinking
UV ResistanceLess resistant to UV raysMore resistant to UV rays
Chemical ResistanceResistant to oils and chemicalsResistant to most chemicals
Environmental ImpactCan be recycled, biodegradable options existRecyclable, less biodegradable
CostGenerally 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.
ApplicationsUsed in clothing, flooring, automobile molding parts, electrical equipment, etc., packaging filmUsed to make a variety of products, including textiles, belts, furniture, insulation, padding, tarps and hardwood gloss finishes
RecyclabilityCan be recycled into new nylon productsPolyester is recyclable and can be processed into new polyester products through mechanical or chemical recycling methods.
Alternative MaterialsFibers, ABS, PET, PBT, PP, POM and HDPEBOPP, 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:

  1. Drying the Material: Dry the nylon or polyester pellets at the appropriate temperature.
  2. Heating and Melting: Feed the dried material into the injection molding machine and melt it to the proper processing temperature.
  3. Injection: Inject the molten material into the mold.
  4. Cooling and Solidification: Allow the injected material to cool and solidify in the mold.
  5. 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:

  1. Material Preparation: Select nylon or polyester sheets or rods of appropriate size and dry them if necessary (especially nylon).
  2. CNC Programming: Write the CNC machining program based on the part design requirements to ensure precise machining paths and parameters.
  3. Material Fixation: Secure the material on the CNC machining center’s worktable to ensure stability during machining.
  4. 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.
  5. 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.

FAQ

Which Material Offers Higher Mechanical Strength?

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.

When to Choose Polyester Over Nylon?

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.

How Do Nylon and Polyester Differ in Machinability?

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

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