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Joint Preparation & Joint Dimensions

June 2020

Joints: Definitions

• Sealant: Material used to fill or seal the joint

• Side of the joint: Area where the sealant connects to the joint

• Depth of the joint: The depth of a joint which is required to be filled with a sealant to

get a correctly performing joint.

• Width of the joint: The width between the to sides of the joint

• Backing material: PU or PE material which is used in a joint to define the depth of the

joint and to prevent 3-point adhesion

• Joint movement: Every change in the width of the joint due to

• Temperature difference

• Difference in humidity

• Movement of the building elements due to shrink/expansion

• Movement due to environmental circumstances (traffic,

earthquakes, …….)

Joints: Types of joint

Static joint

• Movement of the joint between the elements is less than 7% (+/- =

expansion/contraction)

Connection Joint

• Movement of the joint between the elements is between 7% and 15% (+/- =

expansion/contraction)

Expansion joint

• Movement of the joint between the elements is between 15% and 25% (+/- =

expansion/contraction)

Application of sealants

• Joints must be clean, dry, free of dust and grease

• Optimal joint dimensions

• Primer, backer rod necessary?

• Taping to protect joint sides

• Application temperature

• Do not seal in rain or frost

• Humidity should be > 35%

• Apply sealant in joint

• Tool with soapy solution, rinse with clear water (to avoid soap stains)

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Primers for Porous (absorbing) Substrates

• Primers: used on porous substrates• Primer 100: isocyanate

based, used in combination with PU sealants.

• Primer 150: synthetic resins based, used in combination with silicones and SMX Polymers.

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Primer 100: PU sealants

porous substrates:• no plasticizer

migration (on natural stone)

• limits adhesion loss due to capillary water pressure

• prevents bubble formation

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Primer 150: silicones and hybrid (SMX)

porous substrates:• no plasticizer

migration (on natural stone)

• limits adhesion loss due to capillary water pressure

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Activators for Non-Porous Substrates

Surface Activator

• Dual function: cleaner and adhesion promoter in one

• Improves adhesion to non-porous substrates like metals and plastics.

• Leaves a white haze on the substrate, So only use on the covered-area

Activator Spray 601

• UNIVERSAL aerosol applied surface activator

• For use with silicone, PU and hybrid polymer basedsealants and adhesives.

• Used to improve the adhesion on anodized, lacqueredand powder coated aluminium.

• Also suitable for most plastics and other metals

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Joint dimensions – Elastic Sealants

Silicone, Polyurethanes, Hybrid (SMX),

1) Joint Size from 5-11mmdepth = widthE.g.• 5mm wide = 5mm deep• 6mm wide = 6mm deep• Etc…

2) Joint size from 12mm to max widthdepth = half the widthE.g.• 12mm wide = 6mm deep• 24mm wide = 12mm deep• Etc…

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Correct dimensions will ensure high sealant performance over

many years.

Joint dimensions – Plasto & Plasto-elastic

Acrylics and butyl mastics,

1) All recommended joint sizesdepth = width

E.g.• 5mm wide = 5mm deep• 6mm wide = 6mm deep• Etc…

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Common Issues

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If sealant applied too deep- Then the elastic properties are reduced. - There is too much sealant in the joint so

not freely able to flex- Resulting in adhesive failure

If sealant applied too thin- When the joint stretches there is not

enough sealant resulting in a weaker joint which can break more easily

- Resulting in cohesive failure

Joint : preparation

Backing rods are used to

determine correct depth and

are available in a range of

sizes.

Possible causes of cracking

3 points adhesion will lock the sealant to 3 sides not allowing free movement.- Possible solution = backing rod

If the joint movement exceeds the > max. allowed distortion, then the sealant stretch and eventually tear.- Possible solution = ensure correct

product selection

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Preparation of the joint –NEW JOINTS

• The joint surfaces need to be :

• Dustfree

• Stable (free of loose material)

• Free of grease

• Dry

• Use backing material to achieve the correct joint

dimension and prevent 3-point adhesion

• Often preparation is needed:

• Surface preparation

• Primer

• Others

Preparation of the joint –PREVIOUSLY SEALED JOINTS

• The joint surfaces need to be :

• Dustfree

• Stable (free of loose material)

• Free of grease

• Dry

• Use backing material to achieve the correct joint

dimension and prevent 3 point adhesion

• Often preparation is needed:

• Cut out existing sealant

• Surface preparation (Grinding)

• Primer

• Others

Acrylic Range

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Silicone Range

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Silirub+ 8800

• Migration of silicone oil into the natural stone

• Always use marble silicone: silicone oil is linked on the siloxane polymer and cannot migrate out of the silicone sealant.

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PU Sealants –Hybrid Polymer (SMX) Range

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ADHESION

• Porous and non-porous substrates

• Superior bonding to the widest range of substrates

DURABILITY

• Extended life cycle

• Crack resistant

• High UV resistance

• Non-shrinking and non-bubbling

APPLICATION

• Easy to work and tool

• Non-staining

• Faster curing

ENVIRONMENTALLY SAFE

• Solvent free

• Low VOC

• Low odour

• Isocyanate free

SMX® POLYMER ADVANTAGES

POLYURETHANES contain isocyanates which is classified as a carcinogenic, some of the health effects of isocyanate exposure include:

• Cancer• Eye irritation - watering and discomfort• Irritation of the respiratory tract• Dryness of the throat• Tightness of the chest• Difficulty in breathing• Headaches• Asthma attacks• Reddening, swelling and blistering of exposed skin if not washed off• Dermatitis

Source: Guidance note Controlling isocyanate hazards at work (http://www.commerce.wa.gov.au)

WHAT ARE ISOCYANATES?

UV Exposed Sealant

Polyurethane fully exposed to the elements

SMX Polymer vs. PU sealant

UV-stability:result after 6 weeks in artificial climate room

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SMX PU