Choosing between ChemSeal 1® and ChemSeal PU® requires more than comparing two polyurethane sealants on a product sheet.

Both are one-component, moisture-curing polyurethane joint sealants from iChem, but their documented properties and application profiles differ in ways that can affect product selection for construction, movement and expansion joints.

The key question is not:

“Which product is better?”

It is:

“Which sealant better matches the movement, joint geometry, substrate, orientation and exposure conditions of the project?”

This technical comparison examines ChemSeal 1 vs ChemSeal PU from a practical specification perspective, helping engineers, consultants, specifiers and contractors identify which product deserves further evaluation for a particular joint.

For a broader explanation of sealant technologies, joint design and selection criteria, see iChem’s Expansion Joint Sealant: Selection, Applications & Technical Guide:

Read the Expansion Joint Sealant Guide

ChemSeal 1 and ChemSeal PU are both one-component, moisture-curing polyurethane sealants, but they are not interchangeable products.

ChemSeal 1 deserves particular consideration where documented properties such as abrasion and friction resistance and applications involving traffic areas, movement and connection joints, or precast concrete joints are relevant.

ChemSeal PU deserves particular consideration where non-sag application behavior, construction-joint applications, or documented resistance to seawater and diluted acids and alkalis are relevant.

Neither product is universally better.

The appropriate choice depends on:

Joint movement → Joint dimensions → Substrate → Orientation → Exposure → Mechanical conditions → Installation requirements

This distinction is important because selecting a joint sealant based only on polyurethane chemistry can overlook the properties that determine whether it is appropriate for the actual application.

Important: This table is intended for preliminary product selection only. Final specification should be based on the current Technical Data Sheet, project specifications and actual service conditions.

ChemSeal 1® is a one-component, moisture-curing polyurethane joint sealant from iChem that cures to form a flexible elastomeric material.

Its documented characteristics include:

• Permanent flexibility

• Strong adhesion to common construction materials under appropriate conditions

• Weather resistance

• UV resistance

• Abrasion and friction resistance

• Resistance to most chemicals as stated in the product documentation

• Low VOC

• Paintability

• Ease of application and finishing

These characteristics make ChemSeal 1 relevant when evaluating joints where movement accommodation must be considered alongside environmental or mechanical exposure.

Where Is ChemSeal 1 Used?

Its documented application profile includes suitable:

• Parking-area joints

• Movement and connection joints in floors

• Pedestrian and traffic areas

• Precast concrete joints

• Window and door applications

• Curtain wall applications

An application appearing in the product documentation does not remove the need to verify joint movement, dimensions, substrate and service conditions before specification.

Product Page:
ChemSeal 1® – iChem

Technical Data Sheet:
ChemSeal 1® Technical Data Sheet

According to the current Technical Data Sheet:

• Movement Capability: ±25%

• Elongation at Break: ≥600%

• Tensile Strength: 2.2 N/mm²

• Shore A Hardness: 35–40

• Recommended Width-to-Depth Ratio: 2:1 where applicable

• Minimum Joint Depth: 8 mm

• Maximum Joint Width: 50 mm

• Application Temperature: +5°C to +40°C

• Temperature Resistance: -40°C to +90°C

These values should be interpreted together rather than individually.

For example, elongation at break and movement capability are not the same property. A higher elongation value alone does not establish that a sealant is more suitable for a particular movement or expansion joint.

The more reliable assessment is:

Expected movement + Joint geometry + Substrate + Exposure + Service conditions

View the ChemSeal 1 Technical Data Sheet

ChemSeal PU® is a one-component, moisture-curing, gun-grade polyurethane sealant from iChem. A particularly relevant documented characteristic is its non-sag behavior, which can be important when evaluating suitable vertical applications.

Its documented characteristics include:

• Permanent flexibility

• Non-sag application behavior

• Weather resistance

• UV resistance

• Adhesion to suitable substrates under appropriate conditions

• Seawater resistance

• Resistance to diluted acids and alkalis

• Fast curing

• Low VOC

• Good cut and tear resistance after curing

• Paintability

Where Is ChemSeal PU Used?

Its documented application profile includes suitable:

• Concrete construction joints

• Dynamic structural cracks

• Roofing details

• Flashing and gutters

• Window and door joints

• Applications involving suitable concrete, wood and metal substrates

As with ChemSeal 1, the application list should be treated as a selection starting point, not automatic approval for every joint in that category.

Movement, geometry, substrate and service exposure must still be evaluated.

Product Page:
ChemSeal PU® – iChem

Technical Data Sheet:
ChemSeal PU® Technical Data Sheet

According to the current Technical Data Sheet:

• Flow: Non-Sag

• Elongation at Break: >150%

• Tensile Strength: >0.6 N/mm²

• Shore A Hardness: 27–33

• Classification: ASTM C920, Type S, Grade NS, Class 25

• Recommended Width-to-Depth Ratio: 2:1

• Minimum Joint Depth: 8 mm

• Maximum Joint Width: 50 mm

• Application Temperature: +5°C to +40°C

• Service Temperature: -20°C to +80°C

View the ChemSeal PU Technical Data Sheet

No. ChemSeal 1 and ChemSeal PU use the same general polyurethane sealant technology, but their documented technical properties and application profiles are not identical.

This becomes important when a specification requires particular:

• Movement performance

• Application behavior

• Mechanical properties

• Exposure resistance

• Substrate compatibility

• Joint dimensions

A common specification shortcut is:

Same chemistry = equivalent product

That assumption is not sufficient.

Before considering one product as an alternative to the other, the two should be compared against the actual technical requirements of the joint.

A more reliable selection process starts with the joint itself:

1. Define the joint function

2. Determine expected movement

3. Establish width and depth

4. Identify the substrate and its condition

5. Determine vertical or horizontal orientation

6. Identify weather, water and chemical exposure

7. Consider traffic or mechanical conditions

8. Check installation requirements

9. Verify the current Technical Data Sheet

This prevents a common mistake: selecting a sealant first and then trying to make the project conditions fit the product.

For other available sealing solutions, explore the official iChem category:

Explore iChem Joint Sealant Solutions

The technical differences between ChemSeal 1® and ChemSeal PU® become meaningful only when they are connected to actual project requirements.

Rather than asking which product has the “stronger” specification, evaluate how each documented property relates to:

Joint movement + Geometry + Substrate + Orientation + Exposure + Mechanical conditions

1. Movement Capability and Elongation

Movement performance is one of the first factors to evaluate when selecting a sealant for movement, construction or expansion joints.

According to the current Technical Data Sheets:

• ChemSeal 1: Movement Capability of ±25%

• ChemSeal PU: ASTM C920, Class 25

Their documented elongation at break also differs:

• ChemSeal 1: ≥600%

• ChemSeal PU: >150%

These values should not be compared as if they measure the same property.

Movement capability describes the sealant's ability to accommodate dimensional change within a properly designed joint, while elongation at break is a material property measured under test conditions.

Therefore:

Higher elongation at break ≠ automatically better movement-joint performance.

The relevant question is whether the documented performance of the selected sealant matches the expected joint movement and joint design.

ChemSeal 1 Technical Data Sheet

ChemSeal PU Technical Data Sheet

2. Hardness and Tensile Strength

The products also differ in their documented mechanical properties.

These figures provide useful information about material behavior, but they should not be turned into a simple ranking.

For example:

Higher tensile strength does not automatically mean “better sealant.”

A movement joint requires a combination of properties appropriate to its design and service conditions. Mechanical values should therefore be interpreted alongside movement, geometry and exposure rather than independently.

3. Joint Width, Depth and Geometry

Correct joint geometry is essential to sealant performance.

The current technical documentation identifies the following for both products:

• Minimum Joint Depth: 8 mm

• Maximum Joint Width: 50 mm

• Recommended Width-to-Depth Ratio: 2:1 where applicable

This apparent similarity should not be interpreted as proof that every joint can use either product interchangeably.

Why does joint geometry matter?

As a joint opens and closes, the sealant must deform with it. The width and depth of the sealant bead influence how that movement is distributed through the material.

An incorrectly proportioned bead may place unnecessary stress on the sealant or the bond line.

Where required, an appropriate backer rod can help:

• Control sealant depth

• Support the intended profile

• Reduce unnecessary sealant consumption

• Help prevent undesirable bonding at the base of the joint

For more detail on joint design and sealant selection:

Expansion Joint Sealant: Selection, Applications & Technical Guide

ChemSeal PU deserves direct consideration when non-sag behavior is a key requirement for a vertical joint.

Its Technical Data Sheet identifies it as a:

Gun-Grade, Non-Sag Polyurethane Sealant

Non-sag behavior helps the sealant maintain its applied profile before curing, which can be important in suitable vertical applications.

However, non-sag does not by itself establish product suitability.

A vertical joint still requires evaluation of:

• Expected movement

• Width and depth

• Substrate

• Surface preparation

• Backing material

• Primer requirements where applicable

• Application temperature

• Curing conditions

Selection takeaway: If non-sag behavior is essential, ChemSeal PU becomes particularly relevant—but the complete joint requirements still determine final suitability.

ChemSeal PU Product Page

ChemSeal PU Technical Data Sheet

ChemSeal 1 deserves direct evaluation when abrasion and friction resistance are important requirements.

Its documented characteristics include abrasion and friction resistance, while its application profile includes suitable:

• Parking-area joints

• Movement and connection joints in floors

• Pedestrian areas

• Traffic areas

• Precast concrete joints

This creates a useful selection signal for applications involving relevant mechanical exposure.

However, an important distinction must be made:

Sealant abrasion resistance is not the same as the load-bearing capacity of the complete joint system.

For joints exposed to traffic or mechanical activity, also evaluate:

• Type of traffic

• Traffic frequency

• Joint movement

• Condition of joint edges

• Sealant position within the joint

• Joint width and depth

• Water exposure

• Chemical exposure

• Other mechanical demands

Selection takeaway: Abrasion resistance makes ChemSeal 1 relevant for suitable mechanically exposed joints, but it does not automatically qualify every traffic joint.

ChemSeal 1 Product Page

ChemSeal 1 Technical Data Sheet

Both products have documented UV and weather resistance.

Therefore, for an exterior joint, asking:

“Which product is UV resistant?”

does not provide enough information to choose between them.

Instead, evaluate the complete exterior exposure:

• UV radiation

• Rain and moisture

• Temperature variation

• Thermal movement

• Joint orientation

• Substrate

• Joint dimensions

• Expected movement

• Other environmental exposure

Two products may both resist UV while differing in properties that are more important for the actual joint.

Selection takeaway: UV resistance is a requirement both products can address according to their documentation; it is not, by itself, the deciding factor between them.

Both products may be considered for suitable concrete joint applications, but the word “concrete” alone is not enough to select a sealant.

First identify the function of the joint.

Is it:

• A movement joint?

• A construction joint?

• An expansion joint?

• A connection joint?

• A precast concrete joint?

• A traffic-exposed floor joint?

Then establish:

• Expected movement

• Joint dimensions

• Vertical or horizontal orientation

• Environmental exposure

• Traffic or abrasion

• Water exposure

• Chemical exposure

When does ChemSeal 1 become particularly relevant?

ChemSeal 1 deserves direct evaluation when the application aligns with its documented characteristics and uses, such as suitable movement and connection joints, precast concrete joints, or areas where abrasion and friction resistance are important.

When does ChemSeal PU become particularly relevant?

ChemSeal PU deserves direct evaluation where requirements align with its documented characteristics, such as non-sag behavior, suitable construction-joint applications, or relevant seawater/chemical exposure.

Selection takeaway: Do not choose a sealant because the substrate is concrete. Choose it because its documented performance matches the specific concrete joint.

There is no universal winner for expansion joints. The appropriate product depends on the movement and design requirements of the specific joint.

Before comparing products, establish:

1. Expected movement

2. Minimum and maximum joint width

3. Required sealant depth

4. Width-to-depth relationship

5. Substrate

6. Backer rod requirements

7. Environmental exposure

8. Mechanical conditions

9. Installation conditions

This is particularly important because the term “expansion joint sealant” describes an application requirement, not a guarantee that every flexible polyurethane sealant is suitable for every expansion joint.

A useful selection principle is:

Do not make the joint fit the sealant. Select a sealant whose documented capabilities fit the joint.

For a broader technical explanation:

Read the iChem Expansion Joint Sealant Guide

ChemSeal PU deserves direct evaluation when seawater resistance is an important project requirement because seawater resistance is included in its documented characteristics.

However, the term seawater resistant should not be interpreted as universal approval for every marine condition.

There is a meaningful difference between:

• Occasional seawater splash

• Intermittent contact

• Repeated exposure

• Severe or unusual service conditions

The project should also be evaluated for:

• Exposure duration

• Temperature

• Joint movement

• Substrate

• Other chemicals or contaminants

• Overall service environment

For unusual or severe conditions, technical suitability should be confirmed before specification.

ChemSeal PU Technical Data Sheet

Chemical exposure requires more precise evaluation than a general claim of “chemical resistance.”

The documentation for ChemSeal 1 states resistance to most chemicals, while ChemSeal PU includes documented resistance to diluted acids and alkalis.

Before using either statement as a selection criterion, identify:

1. Chemical or substance involved

2. Concentration

3. Exposure temperature

4. Duration of contact

5. Continuous or intermittent exposure

6. Cleaning chemicals

7. Presence of water or other substances

8. Joint movement during service

Do not assume compatibility with a specific chemical, concentration or exposure condition unless it is supported by the relevant technical information.

For demanding chemical environments, project-specific technical review is the safer specification approach.

Both products have documented adhesion characteristics for suitable construction substrates.

However, statements regarding adhesion without priming should not be interpreted as:

“Primer is never required.”

Primer and surface-preparation requirements can depend on:

• Substrate type

• Surface condition

• Porosity

• Moisture

• Existing coatings

• Contamination

• Application environment

Even the correct sealant can experience adhesion problems when applied over:

• Dust

• Laitance

• Oil

• Grease

• Weak concrete

• Old sealant residue

• Incompatible coatings

• Improperly prepared surfaces

Surface preparation is part of sealant performance—not a separate cosmetic step.

The current Technical Data Sheet and application instructions should be followed for the actual substrate and project conditions.

Not automatically. The fact that ChemSeal 1 and ChemSeal PU are both one-component polyurethane sealants does not establish technical equivalence.

Before substituting one for the other, perform a technical equivalency review.

Technical equivalence should be demonstrated by matching project requirements to documented product performance—not by matching the words “polyurethane sealant.”

ChemSeal 1 deserves consideration when project requirements include a relevant combination of:

• One-component polyurethane technology

• Movement accommodation

• UV and weather resistance

• Abrasion and friction resistance

• Suitable traffic-area applications

• Movement and connection joints

• Precast concrete joints

• Paintability

• Low VOC

The product should then be checked against the actual joint dimensions, substrate, exposure and service conditions.

ChemSeal 1 Product Page

ChemSeal 1 Technical Data Sheet

ChemSeal PU deserves consideration when project requirements include a relevant combination of:

• One-component polyurethane technology

• Non-sag behavior

• Suitable vertical applications

• Construction-joint applications

• UV and weather resistance

• Documented seawater resistance

• Resistance to diluted acids and alkalis

• Suitable concrete, wood or metal substrates

• Paintability

• Low VOC

These characteristics provide a shortlisting framework, not automatic approval for a particular project.

ChemSeal PU Product Page

ChemSeal PU Technical Data Sheet

This matrix is for preliminary selection only. Final specification should be based on current technical documentation and the actual project requirements.

Selecting the correct sealant chemistry is only the first step. Specification problems often occur when one product feature is considered in isolation from the complete joint requirements.

1. Selecting by Polyurethane Chemistry Alone

Both ChemSeal 1 and ChemSeal PU are one-component polyurethane sealants, but this does not make them automatically interchangeable.

A reliable selection should also consider:

• Joint function

• Expected movement

• Width and depth

• Substrate

• Application orientation

• Environmental exposure

• Mechanical conditions

• Installation requirements

Same chemistry does not automatically mean the same application suitability.

2. Comparing Feature Counts Instead of Project Requirements

A product with more listed features is not necessarily the better choice.

For example, non-sag behavior may be highly relevant for a vertical application, while abrasion and friction resistance may be more important in a suitable traffic-area joint.

The better specification question is:

Which documented properties address the actual requirements of this joint?

3. Using UV Resistance as the Only Criterion for Exterior Joints

UV resistance is important, but exterior joints may also experience:

• Thermal movement

• Rain and moisture

• Temperature variation

• Movement between adjacent materials

• Different joint orientations

• Mechanical or chemical exposure

Both ChemSeal 1 and ChemSeal PU have documented UV and weather resistance, so this property alone does not normally determine which product should be selected.

4. Assuming Non-Sag Means ChemSeal PU Is Always the Better Choice

Non-sag behavior is an important documented characteristic of ChemSeal PU and can be particularly relevant for suitable vertical applications.

However, another project may place greater importance on movement, abrasion, substrate conditions or other service requirements.

A useful feature becomes a selection advantage only when the project actually requires it.

5. Treating Seawater Resistance as Universal Marine Approval

ChemSeal PU has documented seawater resistance, but marine exposure conditions can differ substantially.

A specification should distinguish between:

• Occasional splash

• Intermittent contact

• Repeated exposure

• Severe or unusual service conditions

The actual exposure should be compared with the available technical documentation before final product approval.

6. Ignoring Surface Preparation

Even a correctly selected sealant can perform poorly if the substrate is not properly prepared.

Potential adhesion problems include:

• Dust

• Laitance

• Oil and grease

• Weak concrete

• Old sealant residue

• Incompatible coatings

• Unsuitable moisture conditions

Sealant selection and substrate preparation should be treated as parts of the same joint-sealing system.

The following examples are intended to help with pre-selection, not replace project-specific technical evaluation.

Scenario 1: Exterior Joint Exposed to Sun and Weather

Start by evaluating both products.

Both have documented UV and weather resistance. Final selection should then consider movement, geometry, substrate, orientation and other environmental conditions.

Scenario 2: Vertical Joint Requiring Non-Sag Application

Start by evaluating ChemSeal PU.

Its documented non-sag behavior makes it directly relevant, while movement, geometry and substrate requirements must still be verified.

Scenario 3: Joint Where Abrasion and Friction Matter

Start by evaluating ChemSeal 1.

Its documented abrasion and friction resistance makes it relevant for suitable mechanically exposed applications.

Scenario 4: Joint Exposed to Seawater

Start by evaluating ChemSeal PU.

Its documented seawater resistance provides a clear reason for shortlisting it, subject to verification of the actual exposure conditions.

Scenario 5: Concrete Expansion Joint

Do not select either product based on “concrete” or “expansion joint” alone.

Start with:

Expected movement → Joint dimensions → Substrate condition → Orientation → Exposure → Installation requirements

Then compare those requirements with the documented capabilities of each product.

For a more detailed selection methodology, see:

Expansion Joint Sealant: Selection, Applications & Technical Guide

A project-specific technical review becomes particularly important when the joint involves conditions that cannot be confidently resolved from standard product information alone.

Examples include:

• Unusual or high movement requirements

• Joint dimensions close to product limits

• Severe chemical exposure

• Continuous or demanding water exposure

• Unusual substrates

• Existing or previously sealed joints

• Heavy mechanical exposure

• Multiple simultaneous exposure conditions

• Project specifications requiring particular standards or approvals

This is an important distinction:

A Technical Data Sheet defines documented product characteristics; it does not replace evaluation of the actual project conditions.

Before specifying ChemSeal 1 or ChemSeal PU, confirm:

1. What is the function of the joint?

2. What movement is expected?

3. What are the minimum and maximum joint dimensions?

4. What is the substrate?

5. What is the condition of the substrate?

6. Is the application vertical or horizontal?

7. Will the joint be exposed to UV and weather?

8. Will it contact water or seawater?

9. Is chemical exposure expected?

10. Will traffic, abrasion or other mechanical exposure occur?

11. What backer rod, primer and surface preparation are required?

12. Does the current Technical Data Sheet support the proposed application?

The purpose of this checklist is to move the selection process away from:

“Which sealant has more features?”

and toward:

“Which sealant has documented properties that match this joint?”

ChemSeal 1 and ChemSeal PU are part of iChem’s broader joint-sealing solutions.

If neither product clearly matches the project requirements—or if other sealant technologies need to be evaluated—review the complete category rather than forcing a choice between two products.

Explore iChem Joint Sealant Solutions

For a broader technical discussion of sealant technologies, applications, joint geometry and selection factors:

Read the Expansion Joint Sealant Technical Guide

ChemSeal 1®

Product Page:
ChemSeal 1® – iChem

Technical Data Sheet:
ChemSeal 1® Technical Data Sheet

ChemSeal PU®

Product Page:
ChemSeal PU® – iChem

Technical Data Sheet:
ChemSeal PU® Technical Data Sheet

Related Resources

Joint Sealant Products – iChem

Expansion Joint Sealant: Selection, Applications & Technical Guide

If the project conditions do not make the selection clear, prepare the following information before requesting technical guidance:

• Joint type and function

• Expected movement

• Width and depth

• Substrate and its condition

• Vertical or horizontal orientation

• Weather and UV exposure

• Water or seawater exposure

• Chemical exposure

• Traffic or abrasion conditions

• Project drawings and specifications, where available

Providing this information allows the product to be evaluated against the actual service conditions rather than a generic application category.

Contact the iChem technical team to discuss your project requirements and identify the most appropriate joint-sealing solution.

The choice between ChemSeal 1 and ChemSeal PU should not be reduced to which product is “better.” The technically relevant question is which product better matches the specific joint and its service conditions.

ChemSeal 1 deserves direct evaluation when requirements such as abrasion and friction resistance, suitable traffic-area applications, weather resistance and UV resistance are important.

ChemSeal PU deserves direct evaluation when requirements such as non-sag application behavior, seawater resistance, or resistance to diluted acids and alkalis are relevant.

For either product, final selection should follow the same sequence:

Project Requirements → Joint Movement → Joint Geometry → Substrate → Exposure → Installation Conditions → Current Technical Data Sheet

This ensures the selected sealant is based on actual project requirements and documented technical performance—not on product claims alone.