NBS Source

Application

Suitable for:

  • Use in structural and weather seal applications.
  • Repair and/or replacement of structurally glazed glass and other substrates where a fast cure is required.
  • On-site structural glazing, including storefront systems.
  • Attachment of panel stiffeners where quick cure is required.
  • In-shop structural glazing where the use of a two-part pump is not viable.


Method:

  • Install backup material or joint filler, setting blocks, spacer shims, and tape. Mask areas adjacent to joints to ensure clean sealant lines.
  • DOWSIL™ 121 Structural Glazing Sealant curing agent and base must be thoroughly mixed using an airless mixing system.
  • DOWSIL™ 121 Structural Glazing Sealant is compatible with most existing pneumatic dispensing tools that accommodate 2 x 200 ml cartridges.
  • The air pressure used to dispense the material should be limited to 90 psi (6 bar) to ensure a good mix and to prevent damage to the sealant cartridge.
  • Eighteen-element static mixers are included in the packaging and are required to mix the material.
  • A new static mixer must be used for each cartridge to ensure proper mixing of the material.
  • Neither hand-mixing nor mechanical mixing is satisfactory due to the incorporation of air, resulting in altered physical properties.


Description

Dowsil 121 Structural Glazing Sealant is a two-part silicone formulation designed specifically for use in structural glazing applications in field and factory applications.


The material is supplied in a two-part cartridge in which the catalyst is a smooth, white paste and the base is tinted either black or grey. Once catalysed, the material cures into a medium-modulus, flexible silicone rubber that is flexible for use in structural and weather seal applications. It can be used in deep, narrow joints to obtain a complete cure.


Features and benefits:

  • Approved for structural and weather seal applications.
  • High level of mechanical properties.
  • Structural capability.
  • Odourless and non-corrosive cure.
  • Excellent stability through wide temperature range: -50°C to +150°C.
  • Stable viscosity for base and catalyst, no heating required.
  • The cured product exhibits excellent weathering characteristics, and a high resistance to ultra-violet radiation, ozone, heat and humidity.
  • Primerless adhesion to alodine and anodized aluminum.
  • Adhesion to DOWSIL™ structural sealants for re-glazing applications.
  • Adhesion and structural strength achieved in 24–48 hours.
  • Meets ASTM C 719 Class 25 (G, A, O).
  • Meets ASTM C1184 Structural Sealant Specification.


Preparation:

  • Clean all joints and glazing pockets, removing all foreign matter and contaminants such as grease, oil, dust, water, frost, surface dirt, old sealants or glazing compounds and protective coatings.
  • In re-glazing applications where the structural sealant is performing per specification, a thin (less than 1/16 inch) layer of the existing DOWSIL™ sealant should remain on the substrate.
  • DOWSIL™ 121 Structural Glazing Sealant will achieve primer-less adhesion to the cured sealant.

General information

Color

Black

Base.

Grey

Base.

White

Catalyst.

Material

Silicone

Shape

Formless

Uniclass

Pr_30_31_76_78 Silicone glazing compounds and sealantsPrimary

CAWS

H13/115 Structural glass assembly

Specification data - Silicone glazing compounds and sealants Enhanced data

Third party certification

ASTM C 719 Class 25 (G, A, O) and C1184.

Material

Neutral cure.

Colour

Black and white.

Dark grey and white.

VOC content

As Catalyzed – Mixed at 1:1 base to catalyst by volume.

Mixed: <25 g/L.

SAG

As Catalyzed – Mixed at 1:1 base to catalyst by volume.

<5 mm.

Tensile strength (MPa)

As Catalyzed – Mixed at 1:1 base to catalyst by volume.

0.93 Mpa.

After seven days.

Elongation

As Catalyzed – Mixed at 1:1 base to catalyst by volume.

325%.

After seven days.

Movement

As Catalyzed – Mixed at 1:1 base to catalyst by volume.

Capability: ± 25%.

Hardness (shore A)

30–40 points.

Shelf life

12 months.

  • When stored in original, unopened containers in a dry location below 30°C, DOWSIL™ 121 Structural Glazing Sealant has a shelf life of 12 months from date of manufacture.
  • Refer to product packaging for “Use By” date.

Capacity

2 x 200 ml.

DOWSIL™ 121 Structural Glazing Sealant is available in kits of 400 ml net fill (2 x 200 ml)/13.5 fl. oz. net fill (2 x 6.8 fl. oz.) cartridges.

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