What Determines the Breathability of PP Spunbond Nonwoven Fabric?

Introduction

Breathability is an important performance characteristic of polypropylene (PP) spunbond nonwoven fabric. It influences how easily air passes through the fabric and can affect comfort, ventilation, filtration performance, moisture management, and the suitability of the material for different applications.

For manufacturers and procurement professionals, understanding spunbond fabric breathability is essential when selecting materials for hygiene products, agricultural covers, protective packaging, disposable products, and other applications that require controlled airflow.

However, breathability is not determined by a single specification. Two PP spunbond fabrics with the same grammage can have different air permeability. A thicker fabric is not necessarily less breathable, and a lighter fabric does not automatically provide better airflow.

The final performance depends on several interacting factors, including filament diameter, web structure, pore distribution, thermal bonding, fabric density, and any surface treatment or lamination applied to the material.

This guide explains the factors affecting spunbond fabric breathability, how air permeability is measured, how buyers should interpret test results, and how to select suitable PP spunbond nonwoven fabric for different applications.

1. What Is Spunbond Fabric Breathability?

Spunbond fabric breathability describes how readily air can pass through the interconnected openings in a nonwoven structure.

PP spunbond nonwoven fabric is generally produced by extruding polypropylene into continuous filaments, arranging those filaments into a web, and bonding the web to form a stable fabric.

The resulting material contains solid polypropylene filaments and spaces between them. These spaces create pathways through which air can move.

When a pressure difference exists between the two sides of the fabric, air can flow through these pathways. The ease of that airflow depends on the structure and resistance of the material.

In technical testing, breathability is commonly evaluated using air permeability.

Air permeability measures the amount of air passing through a specified area of fabric under defined test conditions, including a specified pressure difference.

A higher air permeability result generally means that more air passes through the fabric under the same test conditions.

However, higher air permeability is not automatically better. The appropriate value depends on the intended application.

For example, an agricultural cover may require a balance between ventilation and protection, while a hygiene component may need a different combination of airflow, softness, barrier properties, and strength.

Breathability versus air permeability

The two terms are closely related, but their usage can differ.

A fabric may allow air to pass through while resisting liquid water to some degree. Conversely, a fabric with a surface treatment that improves liquid water resistance may experience a change in airflow.

These properties should be measured separately rather than inferred from one another.

2. How Is Air Permeability Measured in PP Spunbond Fabric?

Air permeability is commonly measured by creating a controlled pressure difference across a fabric sample and measuring the airflow through a defined test area.

The test instrument holds the sample in place, establishes the required pressure difference, and measures the air passing through the material.

The reported result depends on the test method and its conditions.

Common air permeability testing standards

Two commonly referenced methods for textile air permeability testing are:

• ISO 9237, Textiles — Determination of the permeability of fabrics to air

• ASTM D737, Standard Test Method for Air Permeability of Textile Fabrics

Before using either method for formal acceptance testing, buyers should confirm the applicable edition, scope, and suitability for the specific nonwoven material.

A buyer and supplier should agree on the test method and conditions before comparing results.

Common units of air permeability

Air permeability can be reported in several units.

When converting units, ensure that the underlying test conditions are identical. Unit conversion alone does not make results from different pressure differentials or test methods directly comparable.

Why test pressure matters

The pressure difference across the fabric affects the measured airflow.

In general, a greater pressure difference can drive more air through the same material. Therefore, an air permeability value measured at one pressure should not be directly compared with a result measured at another pressure without accounting for the difference.

A test report should identify the method and relevant test conditions.

At a minimum, buyers should confirm:

• The test standard and edition

• The pressure difference used

• The test area

• The number of measurements

• The units of measurement

• The sample identification

Without this information, a reported air permeability value may be difficult to interpret accurately.

3. The Eight Main Factors That Determine Spunbond Fabric Breathability

The breathability of PP spunbond nonwoven fabric results from the combined effect of its material structure and manufacturing conditions.

The following factors are particularly important.

3.1 Grammage (GSM)

Grammage is the mass of fabric per unit area, expressed in grams per square meter.

It is one of the first specifications buyers consider when selecting PP spunbond fabric.

When other structural factors remain similar, increasing GSM often increases the amount of polypropylene present within a given area. This can reduce the available space for airflow and increase resistance to air passing through the fabric.

However, the relationship between GSM and breathability is not universal.

Two fabrics with the same GSM may have different air permeability because their filaments, bonding patterns, and pore structures differ.

Likewise, increasing GSM does not necessarily produce a proportional decrease in airflow.

GSM is an important influence on breathability, but it is not a direct measurement of breathability.

Illustrative comparison

The following table describes a general tendency, not measured results or a guaranteed relationship.

For buyers, the correct approach is to specify GSM and test air permeability separately when both properties are important.

3.2 Filament Diameter

Filament diameter affects how polypropylene filaments occupy space within the nonwoven web.

For a given amount of polymer, changes in filament diameter and filament distribution can alter the number of filaments, the arrangement of contact points, and the geometry of the openings between filaments.

These structural differences can influence airflow.

However, finer filaments do not automatically produce higher air permeability, nor do coarser filaments always produce lower air permeability.

The result depends on how the filaments are distributed, bonded, and packed into the final fabric.

For example, a web made with finer filaments may have many small openings, while another construction may contain fewer but larger flow pathways. The resulting airflow depends on the complete pore structure rather than filament diameter alone.

When comparing two fabrics, buyers should avoid using filament diameter as a substitute for an actual air permeability test.

3.3 Pore Size and Pore Distribution

The size and distribution of openings within a nonwoven fabric are fundamental to its airflow characteristics.

Air moves through the available pathways between filaments. The dimensions, continuity, and distribution of these pathways influence the resistance encountered by moving air.

A fabric with relatively open, interconnected pathways may allow air to pass more readily than a fabric with a more compact structure.

However, average pore size alone is not enough to predict air permeability.

The distribution of pore sizes and the connectivity of the pathways also matter.

A fabric may contain relatively large openings in some locations but have restricted pathways elsewhere. Another fabric may have a more uniform distribution of smaller openings.

These structures can produce different airflow behavior.

For buyers, this explains why two materials with similar GSM and thickness can still have different air permeability.

3.4 Thermal Bonding Conditions

Thermal bonding is an important part of PP spunbond manufacturing.

During production, the web passes through a bonding system that joins filaments at selected contact points. In many spunbond processes, heated calender rolls create a combination of bonded areas and relatively open regions.

The bonding pattern and degree of compaction can influence the structure through which air passes.

Several factors matter:

• Bonding temperature

• Bonding pressure

• Roll geometry and bonding pattern

• Line speed and effective bonding conditions

• Uniformity of the web entering the bonding section

If bonding conditions cause excessive compaction, some airflow pathways may become smaller or more restricted.

However, changing bonding conditions can also affect tensile strength, surface appearance, fabric stability, and other properties.

The objective is not simply to minimize bonding to maximize airflow. The fabric must retain sufficient integrity and strength for its intended use.

A suitable production process balances breathability with mechanical performance and consistency.

3.5 Fabric Thickness and Bulk Density

Thickness is another property that buyers may consider when evaluating breathability.

However, thickness alone cannot reliably predict air permeability.

Two fabrics may have the same measured thickness but different grammage or internal structures. Conversely, two fabrics with the same GSM may have different thicknesses because their web structures and compressibility differ.

Bulk density can help explain part of this relationship.

A simplified apparent bulk density can be calculated as:

[
\rho_{\text{bulk}}=\frac{GSM}{t}
]

Where:

• (\rho_{\text{bulk}}) = apparent bulk density in kg/m³

• (GSM) = grammage in g/m²

• (t) = measured thickness in mm

For example, a hypothetical fabric with a grammage of 20 g/m² and a measured thickness of 0.20 mm has an apparent bulk density of:

[
\rho_{\text{bulk}}=\frac{20}{0.20}=100\text{ kg/m}^3
]

This value describes the apparent density of the overall web, including its internal void spaces. It is not the density of solid polypropylene.

Apparent bulk density can help buyers compare material structures, but it does not fully determine airflow. Pore geometry and connectivity remain important.

The practical lesson is straightforward: use thickness as supporting information, not as a replacement for air permeability testing.

3.6 Bonding Pattern and Open Area

The bonding pattern influences how much of the fabric structure is locally compacted and how the remaining web is arranged.

In calender-bonded PP spunbond fabric, the bonding pattern can influence:

• The distribution of bonded points

• The geometry of open regions

• Local web compaction

• Mechanical stability

• The available pathways for airflow

A pattern with different bonded-area coverage may produce different air permeability even when the GSM is similar.

However, open area alone does not determine airflow. The unbonded web also has its own complex filament structure, and air must pass through connected pathways rather than simply through visually open regions.

For product development, bonding-pattern changes should be evaluated alongside air permeability, tensile properties, and surface quality.

3.7 Surface Treatments and Laminations

PP spunbond fabric may be supplied untreated or with additional processing, depending on the product and application.

Possible treatments or constructions include:

• Hydrophobic or water-repellent finishes

• Surface treatments designed for specific end uses

• Laminated structures

• Coatings

• Multilayer nonwoven constructions

These processes may change the airflow characteristics of the finished material.

For example, a coating or film layer may substantially restrict airflow compared with an uncoated spunbond web. The actual effect depends on the coating coverage, film structure, and manufacturing process.

A surface treatment that changes liquid wetting behavior does not necessarily produce the same change in air permeability. These properties operate through different mechanisms.

Buyers should therefore test the finished material in the form in which it will be used.

If the product is laminated, test the laminate rather than relying only on the air permeability of the base spunbond fabric.

3.8 Production Uniformity

Even when a fabric has an acceptable average air permeability, local variations may affect product performance.

Possible sources of variation include:

• Uneven filament distribution

• Variations in web formation

• Changes in bonding conditions

• Local differences in compaction

• Inconsistent finishing or lamination

These variations can create areas with different resistance to airflow.

For applications where ventilation must be consistent across the material, uniformity is an important purchasing consideration.

Buyers should review the number and distribution of test locations rather than relying only on a single measurement.

4. How Do GSM, Thickness, and Breathability Interact?

GSM, thickness, and air permeability are related, but they measure different characteristics.

Understanding their differences helps buyers avoid selecting materials based on an incomplete specification.

Does higher GSM always mean lower breathability?

No.

Higher GSM often increases the amount of material within a given area, which may increase airflow resistance when other structural factors remain similar.

However, differences in filament distribution, bonding pattern, and pore geometry can change the relationship.

A carefully designed higher-GSM fabric may have different airflow characteristics from a lower-GSM fabric with a more compact structure.

Does thicker fabric always have lower breathability?

No.

Thickness is affected by the fabric's structure and its response to measurement pressure.

A thicker web may contain more internal void space, while another web with similar thickness may have a more compact structure. These differences affect airflow.

Thickness measurements are also sensitive to the specified testing conditions.

Can tensile strength predict air permeability?

Not reliably.

Tensile strength measures how the fabric responds to pulling forces. Air permeability measures the passage of air through the fabric.

Both properties may be influenced by GSM, filament distribution, and bonding conditions, but a high tensile strength result does not establish a particular air permeability value.

When both properties matter, they should be specified and tested independently.

5. How to Measure the Air Permeability of PP Spunbond Fabric

For buyers who need to verify spunbond fabric breathability, air permeability testing is more reliable than visual inspection or thickness measurement alone.

The following procedure outlines the main steps. The exact procedure should follow the selected testing standard and instrument instructions.

Step 1: Prepare a Representative Sample

Select a sample that represents the material being evaluated.

Avoid relying on a single visually attractive area if the fabric may have local variation.

Identify the material, GSM, production batch, and any relevant finishing treatment.

Step 2: Check the Test Equipment

Confirm that the air permeability tester is suitable for the material and the expected airflow range.

Check that the instrument is maintained and verified according to the manufacturer's recommendations and the applicable testing procedure.

Ensure that the test head and clamping system can hold the sample securely without creating unintended leakage around the edges.

Step 3: Confirm the Test Conditions

Before testing, establish the required pressure difference, test area, and other conditions specified by the selected method.

These conditions must remain consistent when comparing results.

Do not compare supplier reports solely because they use the same unit.

Step 4: Mount the Sample

Position the sample as instructed by the test equipment.

The fabric should cover the test area correctly and be held securely.

Avoid folds, creases, or unintended openings around the clamping area.

Air leakage around the sample can distort the result.

Step 5: Measure Airflow

Operate the instrument according to the testing procedure.

The instrument establishes the specified pressure difference and measures the airflow through the test area.

Record the result and its unit.

Step 6: Repeat at Multiple Locations

Repeat the test at representative locations according to the agreed sampling plan.

If cross-width uniformity matters, the sample plan should account for different positions across the roll.

The number of measurements should follow the applicable standard or agreed inspection specification.

Step 7: Calculate and Report the Results

Where the method requires multiple measurements, calculate the appropriate average and report the individual readings or variation indicators when needed.

The report should identify the test conditions so the results can be interpreted and compared correctly.

Example of an air permeability test report

The following is an illustrative report format, not actual MINGYU test data.

The example intentionally does not assign an air permeability value to 25 GSM fabric. GSM alone cannot establish the correct result.

6. How Should Buyers Interpret Air Permeability Test Results?

A higher air permeability result generally indicates that more air passes through the tested fabric under the specified conditions.

However, the purchasing decision should depend on the product's functional requirements.

A buyer should not automatically select the material with the highest airflow.

For some applications, airflow is a priority. For others, the fabric must balance airflow with protection, strength, softness, durability, or liquid resistance.

Comparing two hypothetical fabrics

Consider the following illustrative example.

The table shows why GSM and polymer type are not enough to predict breathability.

Even when two fabrics have the same nominal GSM, their air permeability may differ.

For a ventilation-focused application, Fabric A might be worth evaluating first. For an application requiring a different balance of protection and airflow, Fabric B could still be appropriate.

The final choice should be based on testing and the end product's performance requirements.

Questions to ask when reviewing test results

1. Were both fabrics tested using the same standard?

2. Was the same pressure difference applied?

3. Were the same units and test area used?

4. Were the samples representative of the production material?

5. Were multiple measurement locations tested?

6. Do the results meet the agreed specification?

7. Does the material also meet the required strength and other performance criteria?

These questions help prevent incorrect conclusions when comparing suppliers.

7. How to Choose PP Spunbond Fabric for Different Applications

The ideal breathability of PP spunbond nonwoven fabric depends on its intended use.

There is no single air permeability value that is suitable for every application.

7.1 Hygiene Products

PP spunbond nonwoven fabric is used in various hygiene-related constructions, depending on the product design.

Air permeability may be important when the material forms part of a structure where airflow and comfort are relevant.

However, hygiene products may contain multiple layers, and each layer can serve a different function.

A breathable outer layer, for example, does not guarantee that the complete product has the same air permeability.

Buyers should evaluate the finished construction and any other required properties, such as softness, strength, liquid resistance, or surface characteristics.

Where the material is intended for a regulated or specialized hygiene application, additional product-specific requirements may apply.

7.2 Agricultural Covers

Agricultural covers may require a balance between airflow, light transmission, moisture movement, and protection from environmental conditions.

The desired balance depends on the crop, climate, installation method, and intended use.

A more open structure may allow greater airflow, but the material must also meet the required strength and durability specifications.

Buyers should evaluate the relevant properties together rather than choosing the fabric based only on breathability.

7.3 Protective Packaging

In protective packaging, airflow requirements depend on what the material is protecting and how the packaged product will be stored or transported.

Some applications may benefit from ventilation, while others require reduced air movement or additional barrier properties.

A breathable spunbond material should not automatically be treated as a moisture barrier or a dust barrier.

Where the product requires protection against fine particles, liquid water, or other contaminants, the appropriate barrier performance must be established through relevant testing.

7.4 Disposable Covers and General Industrial Products

Disposable covers and industrial nonwoven products may require a combination of airflow, strength, coverage, and resistance to handling damage.

The appropriate fabric structure depends on the operating environment and the intended service conditions.

For products that are stretched, folded, cut, or mechanically processed, converting performance should be assessed alongside air permeability.

A fabric that performs well in an airflow test may still be unsuitable if it fails the product's tensile or dimensional requirements.

7.5 Medical and Protective Applications

Some medical and protective products require carefully controlled combinations of breathability and barrier performance.

In these applications, ordinary PP spunbond air permeability results cannot establish medical suitability, filtration efficiency, sterility, or protection against specific hazards.

The required tests depend on the intended use and applicable regulatory or customer requirements.

Buyers should evaluate the complete material or finished product against the relevant specifications rather than relying on a general claim that the fabric is breathable.

Application-based selection table

The correct specification should begin with the function of the finished product, not with a generic target for maximum breathability.

8. How Manufacturers Can Control Spunbond Fabric Breathability

For manufacturers, consistent air permeability requires control over the factors that determine the web structure.

Changing one production parameter may affect several properties simultaneously. For example, changing bonding conditions may influence both airflow and tensile strength.

The objective is to achieve the required performance consistently rather than maximizing a single property.

8.1 Control GSM Uniformity

Stable grammage helps reduce one source of variation in the nonwoven web.

Manufacturers should monitor GSM according to their production quality-control procedures and investigate significant deviations.

However, acceptable GSM does not guarantee acceptable air permeability. Both properties may need independent monitoring.

8.2 Maintain Stable Web Formation

The distribution of filaments influences the structure of the finished web.

Uneven web formation may create areas with different density and pore characteristics.

Manufacturing control should therefore consider the uniformity of the web, not only the final average weight.

8.3 Optimize Thermal Bonding

Bonding conditions should be selected to meet the required combination of mechanical integrity and airflow.

Changes to temperature, pressure, line speed, or bonding patterns may affect the finished material.

Manufacturers should evaluate these changes using actual test results rather than assuming that a particular process adjustment will always increase or decrease air permeability.

8.4 Monitor Surface Treatments and Additional Processing

Coatings, finishes, laminations, and other downstream processes may alter airflow.

If the final product has additional processing, quality control should include the finished material whenever possible.

Testing only the untreated base fabric may not accurately represent the performance of the delivered product.

8.5 Use a Consistent Testing Procedure

Consistent testing is necessary to distinguish actual production variation from measurement variation.

A suitable quality-control plan should define:

• The test method

• Equipment requirements

• Sampling locations

• Number of measurements

• Recording procedures

• Acceptance criteria

• Actions when results fall outside the specification

The exact requirements should reflect the product, customer agreement, and applicable testing method.

9. Common Mistakes When Evaluating Spunbond Fabric Breathability

Mistake 1: Assuming Lower GSM Always Means Higher Breathability

Lower GSM can be associated with greater airflow when other structural factors are similar, but it is not a guarantee.

Different web structures may produce different results at the same or similar GSM.

Better approach: Test air permeability directly when it is an important product requirement.

Mistake 2: Using Thickness as a Substitute for Air Permeability

Thickness measures the distance between the fabric's surfaces under specified conditions.

It does not directly measure how much air passes through the material.

Better approach: Record thickness and air permeability as separate properties.

Mistake 3: Comparing Test Results Without Checking Pressure

Air permeability depends on the pressure difference used during testing.

Better approach: Compare results only after confirming that the test methods and relevant conditions are compatible.

Mistake 4: Choosing the Fabric With the Highest Airflow

Maximum airflow may not be the best choice if the application also requires protection, strength, or liquid resistance.

Better approach: Define the functional requirements of the finished product and evaluate the trade-offs.

Mistake 5: Assuming Breathability Means Waterproofness or Liquid Resistance

Airflow and liquid penetration are different performance characteristics.

A fabric that allows air through may still resist some liquid water, depending on its structure and treatment, but this cannot be assumed from air permeability alone.

Better approach: Test liquid resistance and water repellency separately where required.

Mistake 6: Ignoring Laminations and Coatings

The base fabric and the finished construction may have very different airflow characteristics.

Better approach: Test the material in its delivered or intended-use condition.

Mistake 7: Relying on One Measurement

A single measurement may not represent the full sample or production roll.

Better approach: Use an appropriate sampling plan and review both average results and variation.

Mistake 8: Treating Air Permeability as Proof of Filtration Performance

Air permeability measures airflow, not the ability to capture particles of a particular size.

Better approach: Use application-specific filtration tests when particle capture or barrier efficiency is required.

10. What Should Buyers Include in an RFQ for Breathable PP Spunbond Fabric?

When requesting a quotation for PP spunbond nonwoven fabric, buyers should provide enough information for the supplier to understand the intended application and required performance.

If breathability is important, include an air permeability requirement rather than simply asking for a breathable material.

Recommended RFQ information

If the buyer does not yet know the required air permeability value, the RFQ can describe the intended application and ask the supplier to recommend a suitable sample for testing.

The final specification should be confirmed after evaluating the sample and determining the actual performance requirements.

Example RFQ statement

The following is a template buyers can adapt:

"We are looking for PP spunbond nonwoven fabric for [application]. The target grammage is [GSM], and the required roll width is [width]. Air permeability is an important performance requirement. Please provide the available test data, including the test method, pressure difference, measurement unit, and test results. Please also confirm the available material construction, relevant mechanical properties, sample availability, minimum order quantity, and lead time."

This approach helps suppliers provide more useful technical information than a general request for breathable nonwoven fabric.

11. Frequently Asked Questions About Spunbond Fabric Breathability

Q1. What determines the breathability of PP spunbond nonwoven fabric?

Breathability is influenced by GSM, filament diameter and distribution, pore size and connectivity, thermal bonding, fabric density, bonding pattern, surface treatments, and production uniformity. These factors interact, so no single specification can reliably predict air permeability.

Q2. How is spunbond fabric breathability measured?

It is commonly evaluated through an air permeability test. The test measures airflow through a defined area under a specified pressure difference. The selected method and test conditions should be recorded so that results can be compared reliably.

Q3. Does higher GSM mean lower air permeability?

Not always. Higher GSM may reduce air permeability when other structural factors remain similar, but differences in filament arrangement, bonding, and pore structure can change the result. GSM and air permeability should be specified separately when both matter.

Q4. Is thicker PP spunbond fabric less breathable?

Not necessarily. Thickness does not directly measure airflow. Two fabrics with similar thickness can have different pore structures and air permeability. Direct testing is the most reliable way to establish the airflow characteristics of the material.

Q5. What is the difference between breathability and porosity?

Breathability describes how readily air passes through a material, while porosity describes the proportion of its volume occupied by voids. Porosity can influence airflow, but the size, shape, and connectivity of the pores also affect air permeability.

Q6. Which standard is used to test nonwoven fabric air permeability?

ISO 9237 and ASTM D737 are commonly referenced textile air permeability test methods. Buyers should confirm the applicable edition and suitability for the specific nonwoven material and agree on the test conditions before comparing supplier results.

Q7. Does breathable PP spunbond fabric provide waterproof protection?

Not automatically. Breathability and liquid water resistance are different properties. A fabric may allow airflow while resisting some liquid penetration, depending on its structure and treatment, but the required liquid resistance must be tested separately.

Q8. Can air permeability determine filtration efficiency?

No. Air permeability indicates how readily air passes through the fabric under specified conditions. It does not establish the percentage of particles captured or the ability to block specific particle sizes. Filtration applications require appropriate application-specific tests.

Q9. Can two fabrics with the same GSM have different air permeability?

Yes. Different filament arrangements, bonding patterns, pore structures, and surface treatments can produce different air permeability values even when two fabrics have the same nominal GSM.

Q10. What should buyers request from a PP spunbond supplier?

Buyers should provide the application, GSM, width, required air permeability or performance target, and any other critical properties. They should also request relevant test data that identifies the test method and conditions. Samples should be evaluated before bulk production when breathability is critical.

Conclusion

The breathability of PP spunbond nonwoven fabric is determined by the combined effects of its filament structure, pore distribution, grammage, bonding conditions, thickness, surface processing, and manufacturing uniformity.

Although GSM and thickness can provide useful information about the material, neither property can replace an air permeability test.

For buyers, the most reliable approach is to define the required application performance, agree on a suitable test method, compare results under consistent conditions, and evaluate breathability alongside tensile strength and any other essential properties.

For manufacturers, consistent web formation, controlled bonding, and repeatable testing are important for maintaining the required airflow characteristics.

MINGYU supplies PP spunbond nonwoven fabric for international B2B applications. If you are sourcing PP spunbond fabric, share your intended application, target GSM, required width, air permeability requirements, and estimated order quantity. This information can help establish a suitable material specification and identify the key properties to evaluate before placing a bulk order.