4.5.2 Polycondensation adhesives2019-05-03T12:30:12+01:00

4.5.2 Polycondensation adhesives

Polycondensation adhesives: Silicones

  • 1-C RTC* systems, polycondensation    
  • 2-C RTC* systems, polycondensation    
  • 1-C HTC** systems, polyaddition    
  • 2-C RTC* systems, polyaddition    

* RTC = room temperature crosslinking, ** HTC = high temperature crosslinking, PA = polyaddition

Polycondensation adhesives: Silicones

General description:

  • Solvent-free adhesives; 1-C or 2-C processing, depending on the adhesive
  • Cure to become elastomers

Physical properties of the non-cured adhesives:

  • Paste-like to solid; some with thixotropic properties

Physical properties of the cured adhesives:

  • Very elastic
  • Low strength
  • Can be used from -100 to +200 °C; short periods up to 300 °C
  • Excellent resistance to weathering
  • Some susceptible to mould
  • Cannot be lacquered/painted

Note: Systems liberate substances (siloxanes) which can adversely affect further bonded joints and lacquering/painting processes.

Polycondensation adhesives: 1-C RTC silicones

Processing:

  • Manual, semi-automated or fully automated processing
  • For preferred equipment contact the adhesive manufacturer
  • Curing conditions: +5 °C to +40 °C, 5 – 95 % relative humidity
  • Liberation of cleavage products (e.g. acetic acid) during the curing
  • Normal contact pressure; for very firm adhesives, no positioning/sec‌uring necessary
  • Curing from outside to inside
  • Heed the skinning time!
  • Curing from the outside to the inside; several mm per day; initially fast, then slower depending on the available humidity/moisture
  • Adhesive film thickness: 5 – 25 mm
  • Take relevant measures for health and safety at work and environmental protection (General: see Section 7; Details: see safety data sheet)

Points to heed:

  • Heed the upper and lower temperature limits and the humidity requirements when processing the adhesive (see the technical data sheet)
  • The joining process and sec‌uring must be completed prior to the end of the skinning time
  • Once the skinning life has lapsed, the position of the bonded substrates may not be further altered
  • The cleavage products may affect the substrates (corrosion, stress cracking)

If you have questions about the product then see the technical data sheet or contact the adhesive manufacturer

Polycondensation adhesives: 2-C RTC silicones

Processing:

  • Manual, semi-automated or fully automated processing
  • For preferred equipment contact the adhesive manufacturer
  • Processing temperature: room temperature
  • Normal contact pressure; for very firm adhesives: no positioning/sec‌uring necessary
  • Adhesive film thickness: in general 5 – 25 mm
  • Curing by mixing the resin and hardener: at room temperature independent of the air humidity
  • Heed the mixing ratio
  • Thorough mixing absolutely essential, but avoid the incorporation of air bubbles
  • Heed the pot life/processing time
  • Liberation of cleavage products (e.g. alcohol) during the curing
  • Curing times: several hours
  • Secure until the bonded joint has reached hand strength
  • Take relevant measures for health and safety at work and environmental protection (General: see Section 7; Details: see safety data sheet)

Points to heed:

  • Heed the mixing ratio
  • Thorough mixing absolutely essential, but avoid the incorporation of air bubbles
  • Once the pot life has lapsed, do not use any more of the adhesive and dispose of any unused adhesive in the proper way!
  • Once the pot life has lapsed, the position of the bonded substrates may not be further altered
  • Heed the curing time
  • The cleavage products may affect the substrates

If you have questions about the product then see the technical data sheet or contact the adhesive manufacturer

Polyaddition adhesives: 1-C HTC silicones

Processing:

  • Manual, semi-automated or fully automated processing
  • For preferred equipment contact the adhesive manufacturer
  • Processing temperature: room temperature
  • Normal contact pressure; for very firm adhesives, no positioning/sec‌uring necessary
  • Adhesive film thickness: in general 5 – 25 mm
  • Curing at temperatures up to 150 °C in 15 to 30 seconds
  • Secure in position during the entire oven process
  • Very low shrinkage (ca. 0.1 %)
  • Take relevant measures for health and safety at work and environmental protection (General: see Section 7; Details: see safety data sheet))

Points to heed:

  • Ensure the substrates have adequate thermal stability
  • Take into account the heating-up time and cooling-down time for the substrates; this time must be added to the curing time for the adhesive
    → Take special care with thick substrates
  • The heating temperature refers to the temperature in the joint
    → Take special care with thick substrates
  • Stresses can develop in the bonded joint on heating up and cooling down; Only remove the positioning/sec‌uring device after reaching hand strength 

If you have questions about the product then see the technical data sheet or contact the adhesive manufacturer

Polyadditionsklebstoffe: 2K-RTV-Silikone, PA

Processing:

  • Manual, semi-automated or fully automated processing
  • For preferred equipment contact the adhesive manufacturer
  • Processing temperature: room temperature
  • Normal contact pressure; for very firm adhesives: no positioning/sec‌uring necessary
  • Adhesive film thickness: usually: 5 – 25 mm; sometimes less
  • Curing by mixing the resin and hardener: at room temperature independent of the air humidity
  • Heed the mixing ratio
  • Thorough mixing absolutely essential, but avoid the incorporation of air bubbles
  • Heed the pot life / processing time
  • Curing times: up to 24 hours at room temperature
  • Secure until the bonded joint has reached hand strength
  • Take relevant measures for health and safety at work and environmental protection (General: see Section 7; Details: see safety data sheet)

Points to heed:

  • Heed the mixing ratio
  • Thorough mixing absolutely essential, but avoid the incorporation of air bubbles
  • Once the pot life  has lapsed, do not use any more of the adhesive and dispose of any unused adhesive in the proper way!
  • Once the pot life  has lapsed, the position of the bonded substrates may not be further altered
  • Heed the curing time
  • The cleavage products may affect the substrates

If you have questions about the product then see the technical data sheet or contact the adhesive manufacturer

Polycondensation adhesives: Silane-modified adhesives

General description:

  • One-component adhesives (1-C)
  • Curing via moisture induced crosslinking with the cleavage of alcohol (e.g. methanol)
  • Cure to becomeelastomers

Physical properties of the non-cured adhesive:

  • Paste-like or solid, depending on the product; in some cases thixotropic properties

Processing properties:

  • Manual, semi-automated or fully automated processing
  • For preferred equipment contact the adhesive manufacturer
  • Processing temperature: room temperature
  • Normal contact pressure; for very firm adhesives, no positioning/sec‌uring necessary
  • Adhesive film thickness: usually 0.2 – 25 mm
  • Curing method: at room temperature (+5 °C to +40 °C) with air humidity (30 – 95 % rel. humidity)
  • Curing from outside to inside
  • Heed the skinning time!
  • The skinning time  is the processing time of the non-cured adhesive
  • Curing time: several mm in the first 24 hours, then slower; depends on the available humidity/moisture
  • Secure until the bonded joint has reached hand strength
  • Take relevant measures for health and safety at work and environmental protection (General: see Section 7; Details: see safety data sheet)

Typical properties of the cured adhesives:

  • Flexible-elastic, medium elongation at frature
  • Medium strength
  • Use at temperatures from -40 °C to max. +100 °C
  • Moderate UV protection
  • Broad adhesion spectrum
  • Coating/lacquering only wet-in-wet, otherwise pretreatment necessary
  • Repair-bonding on cut open beads only possible for some systems
  • Can only be smoothed to a limited extent

Points to heed:

  • The joining process and sec‌uring must be completed prior to the end of the skinning time
  • Once the skinning life has lapsed, the position of the bonded substrates may not be further altered
  • The cleavage products may affect the substrates (corrosion, stress cracking)

If you have questions about the product then see the technical data sheet or contact the adhesive manufacturer

Polycondensation adhesives: Phenolic resigns

General description:

  • One-component adhesives (1-C)
  • Curing under the effect of pressure and heat
  • Cleavage product on curing: Water
  • Cure to become thermosets

Physical properties of the non-cured adhesive:

  • Liquid
  • As film or web: solid

Processing properties:

  • Manual, semi-automated or fully automated processing
  • For preferred equipment contact the adhesive manufacturer
  • Processing temperature: room temperature
  • Select the correct contact pressure
  • Adhesive film thickness: usually 0.1 – 0.2 mm
  • Curing at 100 – 180 °C under pressure in a few hours
  • Pressure to avoid water vapour bubbles in the adhesive film
  • Secure in position during the entire oven process
  • Take relevant measures for health and safety at work and environmental protection (General: see Section 7; Details: see safety data sheet)

Typical properties of the cured adhesives:

  • High  strength
  • Brittle, low  elongation at frature
  • Temperature for continuous use: up to ca. 180 °C, some also higher
  • Very good  resistance to moisture and chemicals
  • Very good  adhesion and long-term stability on oxidatively etched aluminium surfaces, steel, stainless steel, and friction linings

Points to heed:

  • Check the thermal stability of the substrates prior to curing (in an oven)
  • Take into account the heating-up time and cooling-down time for the substrates; this time must be added to the
  • curing
  •  time for the adhesive
    → Take special care with thick substrates
  • The heating temperature refers to the temperature in the joint
    → Take special care with thick substrates
  • Stress can develop in the joint on heating and cooling

If you have questions about the product then see the technical data sheet or contact the adhesive manufacturer

Polycondensation adhesives: Polyimides (PI)

General description:

  • Solvent-containing one-component adhesive (1-C)
  • Curing via cleavage of liquid under the effect of heat
  • Cleavage product: water
  • Cure to become thermoplastics

Physical properties of the non-cured adhesive:

  • Liquid

Processing properties:

  • Manual, semi-automated or fully automated processing
  • For preferred equipment contact the adhesive manufacturer
  • Processing temperature: room temperature
  • Normal contact pressure
  • Adhesive film thickness: usually 0.1 – 0.2 mm
  • Storage at room temperature, store unstable precursors at -20 °C
  • Processing of the precursors often from solution (DMF, DMAC)
  • Evaporation of the solvent at ca. 100 °C
  • Curing temperature: 230 °C to 250 °C in the oven; pressure: 0.8 to 1 MPa
  • For some products: post-curing at 300 – 400 °C
  • Secure in position during the entire oven process
  • Take relevant measures for health and safety at work and environmental protection (General: see Section 7; Details: see safety data sheet)

Typical properties of the cured adhesives:

  • High strength
  • Very brittle, very low elongation at fracture
  • Maximum temperature for continuous use: up to 320 °C, short periods up to 500 °C
  • Sensitive to moisture

Points to heed:

  • Check the thermal stability of the substrates prior to curing (in an oven)
  • Take into account the heating-up time and cooling-down time for the substrates; this time must be added to the curing time for the adhesive
    → Take special care with thick substrates
  • The heating temperature refers to the temperature in the joint
    → Take special care with thick substrates
  • Stress can develop in the joint on heating and cooling

If you have questions about the product then see the technical data sheet or contact the adhesive manufacturer

Polycondensation adhesives: Polysulphides

General description:

  • Solvent-free two-component adhesives (2-C)
  • Curing via cleavage of liquid at room temperature or elevated temperature
  • Cleavage product: water
  • Cure to become elastomers

Physical properties of the non-cured adhesive:

  • Consistency: paste-like to solid; some with thixotropic properties

Processing properties:

  • Manual, semi-automated or fully automated processing
  • For preferred equipment contact the adhesive manufacturer
  • Processing temperature: room temperature
  • Normal contact pressure; for very firm adhesives, no positioning/sec‌uring necessary
  • Adhesive film thickness: usually 0.2 – 15 mm
  • 2-C processing
  • Curing on mixing together the resin and hardener; at room temperature or with heat input
  • Heed the processing time / pot life
  • The pot life is limited and describes the maximum processing time of the non-cured adhesive (see the technical data sheet)
  • Curing from a few hours up to days at room temperature; acceleration by heat
  • Strong odour (rotten eggs) during processing and curing
  • Secure until the bonded joint has reached hand strength
  • Take relevant measures for health and safety at work and environmental protection (General: see Section 7; Details: see safety data sheet)

Typical properties of the cured adhesives:

  • Low to medium strength
  • Flexible-elastic, medium to high elongation at fracture
  • Temperature for continuous use: -50 °C to max. 120 °C
  • Excellent resistance to fuels, solvents and weathering, high diffusion density
  • Relatively high resistance to a broad range of chemicals with the exception of oxidising chemicals

Points to heed:

  • Heed the mixing ratio
  • Thorough mixing absolutely essential, but avoid the incorporation of air bubbles
  • The pot life depends on the ambient temperature, quantity of mixture and the particular adhesive product
  • Once the pot life has lapsed, do not use any more of the adhesive and dispose of any unused adhesive in the proper way!
  • Once the processing time has lapsed, the position of the bonded substrates may not be further altered

For hotcuring:

  • Ensure the substrates have adequate thermal stability
  • Take into account the heating-up time and cooling-down time for the substrates; this time must be added to the curing time for the adhesive
    → Take special care with thick substrates
  • The heating temperature refers to the temperature in the joint
    → Take special care with thick substrates
  • Stress can develop in the joint on heating and cooling

If you have questions about the product then see the technical data sheet or contact the adhesive manufacturer