Post-Weaving

Post-Weaving Processes:
Dying, Coatings, Laminates, Surfacing & Finishes

We’ve zoomed in on the yarn and then further zoomed in on how those yarns are woven together into fabrics. Now we’ll be zooming in on all of the various finishing processes that are applied to the woven fabrics, transforming them into the high-performance ingredients of bicycle bags. These processes dramatically enhance the fabric’s properties, improving water resistance, adding color, altering the appearance, increasing durability and improving many other characteristics.

We will be examining the most common of the post-weaving processes applied to the fabrics of bike bags, nylon, polyester and UHMWPE. For most fabrics, a combination of post-weaving processes are applied. We are presenting them here in the order that they would typically be applied.

Fabric Preparation

Before the initial post-weaving treatments can be applied, the fabric must undergo several preparation steps to prepare a clean, consistent, dimensionally stable surface. These steps ensure that the fabric is ready for processing.

The fabric preparation processes presented here are in the order that they are typically performed in. This order can sometimes deviate for various reasons. Additionally, not all steps are always performed and sometimes alternative steps are added into the process.

When multiple post-weaving processes are applied to a fabric, many of these fabric preparation steps are repeated between each process to prepare the fabric for the next process.

Desizing

Desizing is the first step in preparing outdoor sports fabrics like nylon, polyester, and UHMWPE for post-weaving processes by removing the sizing agents applied before the weaving process. Sizing agents are applied because the improve yarn strength and weaving efficiency, however they obstruct adhesion and penetration of post-weaving treatments. Proper fabric desizing locks in the weave pattern, improves dye penetration, prevents shrinkage and warping and enhances adhesion for coatings, laminates, treatments and finishes.

Common Methods
  • Chemical Desizing:
    • uses agents like acids or alkalis to dissolve synthetic sizes
    • Oxidation or hydrolysis breaks down synthetic sizes
    • Used for synthetic sizing agents
    • Nylon and polyester often require chemical desizing
  • Enzymatic Desizing:
    • breaks down starch-based sizes with amylases
    • Uses specific enzymes to break down starch-based sizes
    • Common for natural sizing agents
  • Hot Water Washing:
    • Removes water-soluble sizing agents through multiple rinses
    • Often combined with other methods

Scouring

Deep cleaning process removing oils, waxes, and other contaminants from the fabric surface.

Process Components
  • Alkaline Bath Treatment:
    • Removes processing oils and residues
    • Typically uses sodium hydroxide solution
  • Surfactant Application:
    • Helps penetrate and remove contaminants
    • Improves wetting properties
  • Temperature Control:
    • Heated to optimize cleaning efficiency
    • Temperature varies by fiber type
  • Rinse Cycles:
    • Multiple rinses remove cleaning agents
    • Final rinse ensures neutral pH

Heat Setting

The initial stabilization process for synthetic fabrics involves careful application of heat to relieve internal stresses and prevent future dimensional changes.

Process Components
  • Temperature Control: Each polymer type requires specific temperature ranges
    • Nylon: 180-210°C
    • Polyester: 160-180°C
    • UHMWPE: 130-150°C
  • Tension Control: Fabric is held under precise tension during heating
  • Time Control: Duration is optimized for fabric weight and composition
  • Cooling: Controlled cooling locks in the stabilized structure
Benefits
  • Clean Surface: Improves coating adhesion
  • Consistent Properties: Ensures uniform treatment
  • Enhanced Absorption: Better dye penetration
  • Remove Contaminants: Cleans manufacturing residues

Surface Activation (if needed)

Modifies the fabric’s surface energy to enhance adhesion for coatings, dyes, or laminates. Surface activation is not always needed but is sometimes used with challenging fibers like polyester and UHMWPE.

Common Methods
  • Corona Treatment: Uses a high-voltage discharge to increase surface energy.
  • Plasma Treatment: Ionized gas alters the surface properties at a molecular level, increasing wettability.
Process Steps
  • Passing fabric under corona discharge or plasma for surface activation
  • Ensuring uniform exposure across the fabric’s surface

Dyes and Color Treatment

Color application processes are carefully controlled to ensure durability and consistency while maintaining the fabric’s technical properties.

Dyeing typically follows preparation when piece dyeing is applied to woven fabrics. The dye process should be done early since it needs to penetrate the fiber without interference from coatings or finishes.
Note: Solution-dyeing (dying fibers before weaving) would occur much earlier and not be affected by other post-weaving processes.

  • Color application
  • Washing
  • Drying
  • Heat setting

Dyeing Methods

Solution Dyeing
Piece Dyeing
  • Dyeing of finished fabric
  • Types:
    • Batch dyeing
    • Continuous dyeing
  • Benefits:
    • Flexibility in color selection
    • Smaller production runs
  • Process steps:
    1. Fabric preparation
    2. Dye application
    3. Fixation
    4. Washing
    5. Drying

Color Management

Color Matching
  • Precise color specification
  • Measurement methods:
    • Spectrophotometry
    • Visual assessment
    • Standard comparison
  • Quality control:
    • Delta E measurements
    • Light box evaluation
    • Multiple light source checking
Colorfastness Testing
  • Light fastness
  • Wash fastness
  • Rub fastness
  • Weather fastness
  • Perspiration fastness

Coatings

Coatings are applied to enhance specific fabric properties, particularly water resistance, durability, and UV protection. Different coating types and application methods are selected based on the desired performance characteristics.

Coatings are usually applied after dyeing but before other finishes and surfacing treatments. This layer serves as a protective barrier and provides essential properties such as water repellency or abrasion resistance.
Order Rationale: Coatings can impact the fabric’s ability to bond with additional treatments if applied afterward, as some finishes won’t adhere effectively to a coated surface.

  • Base coating layer
  • Performance coating layers
  • Heat setting

Coating Types

Polyurethane (PU) Coatings
  • Most common coating for bike bag fabrics
  • Available in various formulations:
    • Standard PU: Basic water resistance
    • High-Performance PU: Enhanced durability
    • Breathable PU: Allows moisture vapor transfer
  • Application weights: 15-50 g/m²
Acrylic Coatings
  • Used for UV protection and water resistance
  • Properties:
    • Excellent UV stability
    • Good water repellency
    • High flexibility
    • Clear finish option
  • Application weights: 10-30 g/m²
Silicone Coatings
  • Premium coating for maximum water resistance
  • Characteristics:
    • Highest water repellency
    • Excellent flexibility
    • Superior durability
    • Temperature resistant
  • Application weights: 20-40 g/m²

Coating Application Methods

Knife Coating
  • Direct application using a blade to spread coating
  • Process Components:
    • Coating viscosity control
    • Blade angle adjustment
    • Speed regulation
    • Gap height setting
  • Best for: Uniform, heavy coatings
Roller Coating
  • Application through pressured rollers
  • Variables:
    • Roller pressure
    • Speed differential
    • Coating viscosity
    • Temperature control
  • Best for: Light to medium coatings
Foam Coating
  • Application of foamed coating material
  • Benefits:
    • Reduced coating weight
    • Better penetration
    • More uniform coverage
  • Best for: Lightweight fabrics

Multi-Layer Coating Systems

Complex coating systems combining multiple layers for enhanced performance.

Structure

  1. Base Layer:
    • Provides adhesion to fabric
    • Seals fabric surface
  2. Performance Layer:
    • Main functional coating
    • Water resistance or durability
  3. Top Layer:
    • Protection for other layers
    • Surface properties
Common Combinations
  • PU Base + DWR Top:
    • Robust water resistance with beading effect
    • Common in all-weather bags
  • PU Base + Silicone Mid + DWR Top:
    • Maximum water protection
    • Premium waterproof bags
  • Acrylic Base + PU Mid + DWR Top:
    • UV protection with enhanced water resistance
    • High-performance outdoor bags

Laminates

Laminate Types

Lamination involves bonding multiple layers of material together to create composite fabrics with enhanced properties. This process is crucial for creating waterproof-breathable fabrics and other high-performance materials.

Laminates are often applied over coatings to create a stronger, waterproof layer. Laminates like TPU or PE are applied through bonding or thermal fusing, which relies on a stable, sometimes coated, fabric surface.
Order Rationale: Applying laminates over coatings maximizes durability and provides a complete barrier for waterproofing.

  • Membrane application
  • Film bonding
  • Heat setting
Membrane Laminates
  • Thin functional layers bonded to fabric
  • Common membranes:
    • ePTFE (Expanded Polytetrafluoroethylene)
    • PU (Polyurethane)
    • TPU (Thermoplastic Polyurethane)
  • Properties:
    • Waterproof-breathable
    • Wind resistant
    • Durable
Film Laminates
  • Solid polymer films bonded to fabric
  • Types:
    • PU Films
    • TPU Films
    • Polyester Films
  • Properties:
    • Completely waterproof
    • High durability
    • No breathability
Fabric Laminates
  • Multiple fabric layers bonded together
  • Configurations:
    • 2-Layer: Face fabric + membrane
    • 2.5-Layer: Face fabric + membrane + protective coating
    • 3-Layer: Face fabric + membrane + backing fabric

Lamination Methods

Adhesive Lamination
  • Uses liquid or solid adhesives
  • Process steps:
    1. Adhesive application
    2. Layer alignment
    3. Pressure application
    4. Heat curing
  • Best for: Complex multi-layer assemblies
Heat Lamination
  • Direct bonding through heat and pressure
  • Process components:
    • Temperature control
    • Pressure regulation
    • Speed adjustment
    • Cooling control
  • Best for: Thermoplastic materials
Hot Melt Lamination
  • Uses thermoplastic adhesive films
  • Process steps:
    1. Film placement
    2. Heat application
    3. Pressure bonding
    4. Cooling
  • Best for: High-performance technical fabrics
  • Color added during fiber production
  • Benefits:
    • Excellent colorfastness
    • Reduced water usage
    • UV resistant
  • Limitations:
    • Higher minimum quantities
    • Limited color changes

Surface Treatments

Final processes that enhance specific surface properties of the fabric.

Surfacing processes like calendering, brushing, and singeing generally come after coatings and laminates to refine the fabric’s surface feel, appearance, and grip.
Order Rationale: Surfacing can be the final touch on a laminated and coated fabric, as it provides a finished texture without disturbing the functionality of previous layers.

  • Mechanical modifications (sanding, brushing, etc.)
  • Calendering
  • Embossing
  • Heat setting (if required)
  • Texture development
  • Final appearance adjustments

Calendering

Heat and pressure treatment to modify fabric surface.

Process Variables
  • Temperature: Controlled heating for specific fiber types
  • Pressure: Varied for desired surface effect
  • Speed: Affects treatment intensity
  • Roller Surface Type:
    • Smooth: For gloss finish
    • Embossed: For textured patterns
    • Matte: For reduced shine
Effects
  • Controlled surface texture
  • Enhanced fabric density
  • Modified light reflection
  • Improved fabric handle
  • Reduced fabric thickness
Brushing

Mechanical surface treatment using rotating brushes to modify fabric texture.

Process Types

  • Single-side brushing
  • Double-side brushing
  • Continuous brushing
  • Intermittent brushing

Effects

  • Modified surface texture
  • Enhanced fabric feel
  • Improved thermal properties
  • Altered appearance

Plasma Treatment

Surface modification using ionized gas.

Benefits
  • Enhanced adhesion
  • Improved wettability
  • Clean surface
  • No chemical residues
Applications
  • Coating preparation
  • Adhesion improvement
  • Surface cleaning
  • Property modification

Singeing

Controlled burning of surface fibers to create clean, smooth surface.

Process Variables
  • Flame intensity
  • Exposure time
  • Fabric speed
  • Cooling control
Effects
  • Reduced surface fuzz
  • Cleaner appearance
  • Improved coating adhesion
  • Enhanced print quality

Fabric Finishing

Chemical treatments that enhance specific performance properties of the fabric. These finishes are carefully selected based on end-use requirements and are typically applied after lamination but before dyeing, though some may be applied at other stages depending on chemical compatibility and process requirements.

Finishing treatments (e.g., anti-microbial, UV stabilization, and DWR) are generally applied last to provide the fabric with specific protective attributes.
Order Rationale: Finishes work best as a final layer since they directly impact the fabric’s interaction with the environment, especially DWR, which must be applied last to maximize water-repellency.

  • UV stabilizers
  • Antimicrobial treatments
  • Anti-static treatments
  • DWR application
  • Heat setting

Finish Types and Properties

DWR (Durable Water Repellent)
  • Thin-layer coating creating microscopic surface structures
  • Types:
    • C6 Fluorocarbons: Shorter-chain chemistry with reduced environmental impact
    • C0 (Fluorine-free): More environmentally friendly alternatives
    • Silicone-based: Long-lasting water repellency
    • Hydrocarbon-based: Economic option with moderate durability
  • Application Methods:
    • Pad application: Most common for uniform coverage
    • Spray application: For specialized or localized treatment
    • Foam application: Reduces chemical usage
  • Properties:
    • Creates microscopic “peaks” that water beads on
    • Maintains fabric breathability
    • Reduces surface tension
    • Can be combined with other coating systems
UV Stabilization
  • Critical for outdoor performance
  • Types:
    • HALS (Hindered Amine Light Stabilizers)
    • UV Absorbers
    • Combination systems
  • Application Methods:
    • Pad application
    • Exhaustion process
    • Coating incorporation
  • Effectiveness:
    • Polyester: Inherent UV resistance enhanced
    • Nylon: Critical for preventing degradation
    • UHMWPE: Essential for outdoor use
  • Performance Metrics:
    • UV Protection Factor (UPF) rating
    • Strength retention after exposure
    • Color stability
    • Long-term durability
Anti-Static Treatment
  • Reduces static charge buildup
  • Types:
    • Topical anti-static agents
    • Conductive fiber additives
    • Hydrophilic treatments
  • Application Methods:
    • Pad application
    • Spray application
    • Fiber incorporation
  • Material Considerations:
    • Nylon: Highly prone to static
    • Polyester: Moderately prone
    • UHMWPE: Less problematic
  • Performance Metrics:
    • Surface resistivity
    • Charge decay time
    • Durability to washing
Antimicrobial Treatment
  • Prevents odor and material degradation
  • Types:
    • Silver-based treatments
    • Quaternary ammonium compounds
    • Zinc-based solutions
  • Application Methods:
    • Pad application
    • Exhaustion process
    • Coating incorporation
  • Material Compatibility:
    • Nylon: Excellent absorption
    • Polyester: Good compatibility
    • UHMWPE: Limited absorption
  • Performance Metrics:
    • Bacterial reduction rate
    • Wash durability
    • Environmental impact
Soil Release/Stain Resistance
  • Enhances cleaning and maintenance
  • Types:
    • Fluorocarbon-based
    • Silicon-based
    • Non-fluorinated alternatives
  • Application Methods:
    • Pad application
    • Spray application
    • Bath treatment
  • Material Considerations:
    • Nylon: Good absorption
    • Polyester: Excellent compatibility
    • UHMWPE: Limited effectiveness
  • Performance Metrics:
    • Oil repellency rating
    • Stain release grade
    • Wash durability

Application Methods

Pad Application
  • Most common method
  • Process Components:
    • Chemical bath preparation
    • Padding mangle
    • Drying/curing chamber
  • Variables:
    • Pick-up percentage
    • Bath concentration
    • Temperature control
    • Drying conditions
Exhaust Process
  • Used for certain finishes
  • Process Steps:
    • Bath preparation
    • Temperature ramping
    • Chemical exhaustion
    • Rinse cycles
  • Controls:
    • Time/temperature profile
    • pH control
    • Agitation level
    • Bath ratio
Spray Application
  • For specialized treatments
  • Components:
    • Spray system
    • Chemical delivery
    • Coverage control
    • Drying system

Finish Combinations

Common Combinations
  • UV + Anti-static:
    • Standard for light-colored fabrics
    • Enhanced outdoor performance
  • Antimicrobial + Soil Release:
    • Used in high-wear areas
    • Improved maintenance
  • UV + Antimicrobial + Anti-static:
    • Premium outdoor fabrics
    • Maximum protection
Application Considerations
  • Chemical compatibility
  • Process sequence
  • Temperature limitations
  • pH requirements
  • Cure conditions