SikaMelt®-680 LV

Polyurethane Hot Melt with low viscosity and high initial tack

SikaMelt®-680 LV is a versatile reactive adhesive based on polyurethane hot melt that cures on exposure to atmospheric humidity. It is suitable for lamination of textiles, foils, non woven materials and foams.  

  • High final strength and flexibility 
  • High initial tack 
  • Very good washing and cleaning resistance 
  • Broad adhesion spectrum 
 
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PRODUCT BENEFITS

  • High final strength and flexibility 
  • High initial tack 
  • Very good washing and cleaning resistance 
  • Broad adhesion spectrum 
 

Areas of Application

SikaMelt®-680 LV has a broad adhesion spectrum. It is suitable for permanent strong bonding of polar polymers like ABS, PC, SMC and PVC, and wood, foams, textiles, painted and primed steel. Non polar polymers like PP and PE can also be bonded after special pre-treatment.
This product is suitable for professional experienced users only. Test with actual substrates and conditions have to be performed to ensure adhesion and material compatibility.  

Product Details

Typical Product Data
Chemical base

Polyurethane

Color (CQP001-1)

Transparent

Cure mechanism

Moisture curing

Density (uncured)

1.2 kg/l

Viscosity (by Brookfield)

at 130 °C

2 000 mPa·s

Application temperature

 

short term max.1 h

90 – 140 °C

160 °C A

Curing time (CQP558-1)

15 h

Green strength (CQP557-1)

0.01 MPa

Tensile strength (CQP036-3)

15 MPa

Shelf life

18 months

CQP = Corporate Quality Procedure

A) Only valid for nozzle
Technical Information

CURE MECHANISM

SikaMelt®-680 LV cures by reaction with atmospheric moisture. At low temperatures the water content in the air is lower, which will result in a lower curing speed (see diagram 1).
When bonding hydrophobic (e.g. PP) and/or moisture impermeable substrates a significantly longer curing time has to be taken into account. This applies especially on assembly applications with an adhesive thickness > 100 µm. For lamination applications of hydrophobic and/or moisture impermeable substrates the adhesive layer shall not exceed 100 µm. In such cases project related tests with original substrates and conditions are mandatory.

en_PNG_01-diagram-sikamelt-680LV

Diagram 1: Curing time for 500 µm film

CHEMICAL RESISTANCE

SikaMelt®-680 LV is resistant to aqueous surfactant, weak alkaline/acids solutions and temporarily resistant to fuels, solvents and mineral oils.
The chemical resistance is influenced by several factors such as chemical composition, concentration, period of exposure and temperature. Therefore a project related testing in case of chemical or thermal exposure is required.

Application

Application Information

Surface preparation

Surfaces must be clean, dry and free from grease, oil and dust.
Based on the surface and type of material, a physical or chemical pre-treatment might be required. Type of pre-treatment must be determined by preliminary tests.

For metals best results are achieved, if substrates are heated up between 40 °C and 60 °C prior the assembly process.

 

Application

With adequate processing equipment SikaMelt®-680 LV can be applied as film, dot, bead or spray application. For automated applications a suitable filter system is required.
To meet the required application properties the adhesive viscosity can be adjusted by adapting the application temperature (see table Typical Product Data).
During breaks SikaMelt®-680 LV is to be processed as follows:
For breaks ≥ 1 h the heating needs to be lowered to 80 °C and for breaks ≥ 4 h the heating needs to be switched off.
To guarantee a constant quality during the whole production process it is mandatory to protect the adhesive in the melting tank with nitrogen, carbon dioxide or dried air (to avoid possible reaction of the product with humidity). At breaks or shut downs dip nozzle in dried oil in order to prevent curing of the adhesive (avoid blockage).
For advice on selecting and setting up suitable processing equipment contact the System Engineering Department of Sika Industry.

Removal

Equipment and application tools can be cleaned with SikaMelt®-009. Cured material can for cleaning purposes be swelled with SikaMelt®-001 and needs to be removed mechanically (see also cleaning instruction). SikaMelt®-680 LV may be removed from tools and equipment with Sika® Remover-208 or another suitable solvent.
Hands and exposed skin have to be washed immediately using hand wipes such as Sika® Cleaner-350H or a suitable industrial hand cleaner and water. Do not use solvents on skin.

STORAGE CONDITIONS

SikaMelt®-680 LV has to be stored at temperature below 30 °C in a dry place.
For transportation purposes, the storage temperature can be exceeded for a period of max. 2 weeks up to 60 °C.