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