Polyurethane sealant | Expansion joint sealant | Supex India

What and why of Joint sealing and need for expansion joint sealant

Joints in between construction elements can be found in different parts of a construction, e. g. between

precast concrete elements in facades, around windows and doors, between floors and walls, around \

storage tanks, etc. Joints sealants play a very important role here.

Polyurethane expansion Joint sealant has to meet various requirements depending on function and

location of the respective joint. The purpose of joint sealing generally is to: ́ Prevent passage of media'

(air, water, chemicals, smoke etc.) ́ Provide thermal and sound insulation ́ Enhance the visual

appearance of the construction

WHY ELASTIC SEALING?

Buildings and civil engineering structures consist of individual elements which exhibit relative

movements to each other. There are two kinds of such movements:

1. Thermal movements :Temperature changes due to climatic, solar and weather effects results

in expansion or contraction of the building elements. For the sealants connecting them this leads to

permanent movement. In case of increasing temperatures, the elements expand, the joints

become smaller and the sealant is compressed as shown in the image below:-

In case of decreasing temperatures, the elements shrink, the joints become larger and the sealant
expanded or elongated as shown in the image below:-

In the latter case the adhesion of the sealant to the substrate is crucial. Thermal movements are

considerably in case of large elements or when different materials are used for example a brick wall

and vinyl window frame.

2. Structural movements: Structural movements can have several reasons. They can originate

from settlement of the structure, vibrations or other loads like wind. Structural movements change the

initial joint dimensions and consequently can apply considerable stress to the sealing material, often

shear stress as shown in the image below:-

Movement within the joints is a reality and the long-term solution to accommodate them are high-

performance elastic joint sealants. These sealants retain their original functionality and good adhesion

to the substrate throughout their whole life cycle and provide durable tightness

Properties of polyurethane expansion Joint Sealant

The application properties of sealants have a direct impact on the efficiency, reliability and

appearance of the joint sealing job.

KEY APPLICATION ADVANTAGES

LOW EXTRUSION FORCE: For efficient application the sealant must be easy to extrude – even at

low temperatures.

SHORT CUT-OFF STRING: Avoid unnecessary cleaning. Long cutoff strings will mess up your

construction elements and permanently stain them.

NON-SAG BEHAVIOUR: Sealants must stays where they are applied. Non-sag behaviour is essential

when the joints are wide and in a vertical or overhead position. The rheology of Sika’s facade sealants

is designed not to flow or sag after application.

GOOD “BODY” AND TACK-FREE SURFACE: To achieve a visually attractive finish the sealant must

be easy to tool. Sika sealants stand out due to their good body, tack-free surface and sufficient tooling

'time, even under warm and humid conditions – the prerequisite to perfectly shape and smooth out the

sealant surface.

LOW SMELL AND LOW VOC: Being exposed to badly smelling products and volatile organic

compounds (VOC) all day will make you feel bad. When creating our products we take care that their

smell is not disturbing and the VOC meets the stringent market requirements

Concrete Joint Sealant/ Elastomeric joint sealant/ Expansion

joint sealant/ Urethane joint sealants

Supex provides a full range of polyurethane expansion joint sealants and accessories for

your construction with the following main advantages:

Long-term elasticity to accommodate joint movements
Good and durable adhesion to common construction materials to ensure durable tightness
Perfect handling for efficient, reliable and attractive joint sealant application
Visual appearance that meets the demands of architects and owners
Excellent mechanical properties, chemical resistance and weatherability ensuring sustainable
performance even under most adverse conditions and loads
Technical support and training for architects, specifiers and applicators

Supex offers sealant solutions for a great variety of applications:

Building envelope joints like precast concrete facades, glass and metal facades,
natural stone facades and joints in exterior insulation and finishing systems
(EIFS)for wall cladding
Concrete Facade

Glass and Metal Facade

Civil engineering joints in containment bunds of fuel stations, water and sewage
treatment plants and swimming pools

Civil Engineering Joints

Interior finishing joints in bathrooms and kitchens
Floor joints

Floor Joints

Roof and flashing joints

Sealing Joints on Metal Roofs

Supex sealants makes construction joints sustainably air and water tight. The best performance for

your application is the key issue; therefore Supex sealants produces high quality products in all

major technologies.

FACADE- Joint design for effective

waterproofing & durable joints.

THE FACADE IS THE FACE of your building. In contemporary architecture the facade is of special

interest expressed by large dimensions, unconventional shapes and high material diversity. Joint

design is demanding and prone to mistakes. For integral joint specification, following some rough
guidelines will result in a long-lasting and tight building envelope.

JOINT DESIGN FOR LONG-LASTING & TIGHT BUILDING ENVELOPE JOINTS JOINT WIDTH

A construction joint’s expected movement can be calculated from the dimensions and thermal

expansion coefficients of the facade elements and the maximum and minimum temperature your

facade will be exposed to. The expected movement and the sealant’s movement capability leads to a

minimum joint width required to withstand the daily and seasonal cyclic movement. To simplify your

choice, sealants are classified according to their movement class by several standards.

MATERIALS TO BE JOINED

Depending on the design of your facade, it may consist of facade elements of different materials like

'concrete, glass, metal, brick or stone, just to mention the most common ones. These elements have

to be sealed to each other but also to other waterproofing products like membranes or structural

glazing elements consisting of glass, spacer and adhesives. The sealant must show good adhesion

to the adjacent materials and at the same time must be compatible with all materials to avoid

discoloration, loss of adhesion over time or any changes of properties.

ENVIRONMENTAL EXPOSURE

Environmental conditions have an impact on the service life and the performance of the sealant.

Expected UV and heat exposure as well as the chemical impact must be considered when choosing

the product. Additionally, when sealing between the inside and outside of the building the vapor

permeability of the sealant has to be considered to avoid accumulation of water in the walls. The

general rule is to use a sealant with lower vapor permeability on the warm side of the wall, as warm

air is generally more humid than cold air (or the same vapor permeability but thicker applied on

the inside). APPEARANCE Ugly joints are like scares on a facade. Therefore, when specifying

the joint sealant, the visual appearance and matched color of the joint is important. When sealing

natural stone or glass a products staining and streaking must be checked as this would damage the

appearance of the whole facade irreversibly. In this case stone and glass must be replaced.

By using non-staining and non-streaking products where required money can be saved ultimately.

MECHANICAL EXPOSURE

Floor and some wall joints are exposed to mechanical impact. (Floor: Tyres, heels, tolly, fork lift,

cleaning machines (high pressure water, brushes). Wall: People that pick and play with the sealants,

especially in zones where they have to wait like bus stations). This impact damages the joint sealants.

Therefore choose harder sealants, with high tear propagation resistance and plan recessed floor

joints to avoid contact with the wheels.

JOINT DIMENSIONING

The design of a sealing system involves more than just the selection of a sealant with suitable

physical and chemical resistance. In order to obtain optimal long-term performance the following

considerations are essential as well:

Proper joint design, including correct dimensioning and backup material selection
Type and nature of substrates
Application process and ambient conditions at the time of the installation

GENERAL RULES FOR JOINT DESIGN

Movement capability of the sealant and joint width must fit to the expected movement of the adjacent

building elements.

Joint width: Must be designed according to the sealants movement capability Sealant dimensions:
The optimal ratio of sealant width to depth is 2:1 for facade joints and 1:0.8 for floor joints

Joint depth: A joint must have sufficient depth so that backer rod and sealant fit inside.

Spacing between joints: In the following tables an example for joint dimensions for concrete elements

and a sealant with 25% movement capability are given:

Facade Joints			Interior Floor Joints			Exterior Floor Joints
Joint spacing	Minim. joint	Sealant depth	Joint spacing	Minim. joint	Sealant depth	Joint spacing	Minim. joint	Sealant depth
(m)	width (mm)	(mm)	(m)	width (mm)	(mm)	(m)	width (mm)	(mm)
2	15	8	2	10	12	2	12	10
4	20	10	3	10	12	3	12	10
6	25	12	4	10	12	4	15	12
8	30	15	5	10	12	5	18	15
10	35	18	6	10	12	6	20	17
			8	10	12	8	30	25

The sealant must be capable of extending and contracting along with the building elements to which it

is joined. If this is not possible the consequence may be adhesive and/or cohesive failure.

The sealant depth defines the stress at the sealant/substrate interface. If the sealant depth is too large

this will lead to severe stress on the interface at low temperatures and finally adhesion failure.

3-side adhesion must be avoided. Any other adhesion than to the joint flanks leads to massive

reduction of the elasticity and movement capability of the sealant and consequently to failure of the

sealant. The correct use of backing material can avoid these problems. The backer rod defines the

joint depth and avoids 3-side adhesion.

FLOOR JOINT DESIGN

Depending on the location and expected loads of a floor joint special design considerations for floor

joints are necessary. Generally high modulus sealants are recommended for floor joint applications.

Joints in areas with a lot of car and/or equipment traffic should be recessed to reduce mechanical loads.

Joints in pedestrian areas should be flush with the surface to prevent tripping hazard. The sealant

must also have a certain hardness and indentation resistance due to high mechanical impacts from
narrow heels.

JOINT RENEWAL AND REPAIR

REASONS FOR JOINT REPAIR

A careful visual inspection is usually enough to determine if the joint sealing is improper or worn out

and a replace-ment is needed. Reasons for joint refurbishment may include but are not limited to

the following:

Failures in workmanship
Use of unsuitable type of sealant
Wrong joint design
Underestimated load
Sealant reached end of its service life.
Compatibility issues with adjacent materials (e. g. gaskets)
Exposure to aggressive chemicals
Insufficient surface preparation (loss of adhesion

Following steps should be done:

Remove old sealant. Up to 0.5 mm of the old sealant can be left on the sur-face
if the substrate and the adhesion are still in good shape.
Make sure that the substrate & joint flanks are still strong. In areas with adhesion loss,
mechanical cleaning of the bonding area is mandatory.
In order to ensure long-term durability and tightness of the newly sealed joint both the

Polyurethane Expansion Joint Sealants

Different names for the same product or application: self leveling concrete joint filler, polyurethane

sealant for concrete, elastomeric polyurethane sealant, self leveling expansion joint filler, crack and

joint sealant, vertical expansion joint sealant, sealing expansion joints, best expansion joint sealant, '

concrete gap sealer, flexible joint sealant, elastomeric sealant concrete, sealants for joints in buildings,

concrete gap sealant, sealant for precast concrete joints, seal concrete joints, concrete joint

compound, expansion joint compound, control joint sealant, construction joint sealant.

Supex PU 25 Polyurethane sealant – one part moisture cure PU sealant, manufactured in Europe as

per special requirement of Indian conditions.

PU sealants from Accumetric Silicones/ Boss Products/ Boss Silicones

Boss PU 25 – General purpose Polyurethane for sealing and bonding.

Boss PU SL – Self levelling polyurethane sealant for construction joints.

Boss PU LM– Low modulus PU sealant from Boss products, flexible sealing.

Boss PU 50 – high adhesive property, higher hardness, higher strength. Special grade PU sealant

even suitable for high strength bonding.

Construction Polyurethane sealant from Mccoy Soudal

Soudaflex FC– excellent performance for construction joints.

These products are available online from this

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