Technical Data Sheet (provisional)

Sikaflex-521 UV (VP)Excellent adherent, weathering resistantsealant

Technical product data:

Chemical base one-part polyurethane-hybrid

Colour white, grey

Density (DIN 53479) (uncured) 1.4 kg/l, approx.

Stability (non-sag properties) Good, with no tendency to sag

Cure mechanism Moisture-curing

Tack-free time1) 30 min. approx.

Rate of cure1) 3.0 mm per 24 hrs, approx.

Shrinkage (DIN 52451) < 2%

Shore A hardness (DIN 53505) 40, approx.

Tensile strength (DIN 53504) 1.8 N/mm2, approx.

Elongation at break (DIN 53504) 300%, approx.

Tear strength (DIN 53515) 8 N/mm, approx.

Volume resistivity (DIN 53482) 1010 W cm, approx.

Glass transition temperature (DIN 53445) -60C, approx.

Service temperature (continuous)short term

-40C to +90Cup to 16 hrs.at 120C / 4 hrs.at 140C

Movement accommodation factor 10%, approx.

Shelf life (stored below 25C) 6 months1) = at 23C and 50% relative humidity

Description:Sikaflex-521 UV (VP) is a multi-purpose non-sag elastic one-partsealant based on a polyurethane-hybrid compound, which cures onexposure to atmospheric moistureto form a durable elastomer.Sikaflex-521 UV (VP) contains noisocyanate and is manufactured inaccordance with the ISO 9001/14001 quality assurance system.

Product benefits: one-part formulation resistant to UV radiation resistant to ageing and weath-

ering bonds well to a wide variety of

substrates without the need forpre-treatment

elastic

can be overpainted can be sanded low odour non-corrosive high electrical resistance VOC and solvent-free silicone-free PVC-free

Cure mechanism:Sikaflex-521 UV (VP) cures byreaction with atmospheric mois-ture. At low temperatures the watercontent of the air is lower and thecuring reaction proceeds a littlemore slowly.

Areas of application:Sikaflex-521 UV (VP) bonds wellto a wide variety of substrates andis suitable for making permanentelastic seals of high adhesivestrength.Suitable substrate materials aretimber, metals, metal primers andpaint coatings (two-part systems),ceramic materials and plastics.Seek manufacturers advice beforeusing on transparent materials thatare prone to stress cracking.

Chemical resistance:Sikaflex-521 UV (VP) is resistantto UV radiation, fresh water, sea-water and proprietary aqueouscleaning agents; temporarily re-sistant to fuels, mineral oils, vege-table and animal fats and oils; notresistant to organic acids, concen-trated mineral acids, caustic solu-tions or solvents.The above information is offeredfor general guidance only. Adviceon specific applications will begiven on request.

Method of application:Surface preparation: The faces ofthe joint must be clean, dry andfree from all traces of grease, oil,wax and dust. The adhesion of thesealant can be improved by wipingthe joint with Sika Hybrid Activator(a cleaning and activating agent)or eventually applying the appro-priate Sika Primer.Directions for the preparation andtreatment of different substratesare given in the Sika Primer Ta-ble.

Application: For cartridges: piercethe cartridge membrane and peelback completely. For Unipacs: re-move the clip. Place the unipac inthe application gun and snip off theclosure clip. Cut off the tip of thenozzle to suit joint width and gunthe sealant into the joint with asuitable hand-operated or com-pressed-air gun, taking care toavoid air entrapment.Once opened, packs should beused up within a relatively shortspace of time.To ensure satisfactory conditionsfor curing, do not apply at tem-peratures below 5C or above35C. The optimum temperaturefor substrate and sealant is be-tween 15C and 25C.

Tooling and finishing: Tooling andfinishing must be carried out withinthe tack-free time of the sealant.We recommend the use of Sika

Tooling Agent N. Other productsmust be tested for suitabil-ity/compatibility prior to use.

Overpainting: Sikaflex-521 UV(VP) can be overpainted beforetack-free. The paint must be testedfor compatibility by carrying outpreliminary trials.Curing speed of overpainted freshSikaflex-521 UV (VP) will be low-eredIt should be understood that thehardness and film thickness of thepaint might impair the elasticity ofthe sealant and lead to cracking ofthe paint film.

Removal:Uncured Sikaflex-521 UV (VP)may be removed from tools andequipment with Sika Remover-208. Once cured, the material canonly be removed mechanically.Hands and exposed skin should bewashed immediately using a suit-able industrial hand cleanser andwater. Do not use solvents!

Important:If Sikaflex-521 UV (VP) is used incombination with a PUR adhesive,the latter must be fully cured be-fore seam sealing with Sikaflex-521 UV (VP).

Further information:Copies of the following publica-tions are available on request: Safety Data Sheet

Packaging information:

cartridge 300 ml

unipac 600 ml

hobbock (on request) 23 l

drum (on request) 195 l

Important:For information and advice on thesafe handling, storage and dis-posal of chemical products, usersshould refer to the current SafetyData Sheet containing physical,ecological, toxicological and othersafety-related data for the appro-priate type of substance.

Note:The information, and, in particular, the rec-ommendations relating to the applicationand end-use of Sika products, are given ingood faith based on Sika's current know l-edge and experience of the products whenproperly stored, handled and applied undernormal conditions. In practice, the differ-ences in materials, substrates and actualsite conditions are such that no warranty inrespect of merchantability or of fitness for aparticular purpose, nor any liability arisingout of any legal relationship whatsoever,can be inferred either from this information,or from any written recommendations, orfrom any other advice offered. The pro-prietary rights of third parties must be ob-served. All orders are accepted subject toour current terms of sale and delivery. Us-ers should always refer to the most recentissue of the Technical Data Sheet for theproduct concerned; copies of which will besupplied on request.