Poly bd® Resins in ConstructionApplications

IntroductionPoly bd® resins are liquid, hydroxyl terminatedhomopolymers of butadiene. The reaction of Polybd® resins with curing agents, such as conventional di-and polyisocyanates, provides an economical route forthe preparation of general-purpose elastomers, suchas polyurethanes.

The unique structure of the Poly bd® resin allowsformulators to produce polyurethanes with propertiessurpassing those of polyurethanes produced fromconventional polyether or polyester polyols, as wellas those of general-purpose rubbers. Moreover, theexcellent compatibility of Poly bd® resin with asphaltallows formulators to make a variety of polymer-modified asphalt systems.

Uses In Construction ApplicationsPoly bd® resins have been used to prepare castableelastomers, caulks, sealants, membranes, foams,adhesives, coatings, propellant binders, potting, andencapsulation compounds.

In the construction area, some specific applicationuses are listed below:

• Penetration joints and adhesives on EPDM orasphalt roofing membranes (pitch pan)

• Adhesives and sealants for crack filling orexpansion joints for roofs, roads, bridges, andairport runways, providing excellentresilience, rut resistance, and adhesion tovarious substrates

• Waterproof membranes, coatings orgeomembranes for :

- parking decks, roof decks, terraces- waste water, potable water (NSF 61

approved for direct contact), paper mills,sewage pipes

- below grade waterproofing• Self adhering systems (e.g., pressure sensitive

adhesives with or without asphalt), providingimproved low temperature tack and minimumsagging at high temperatures

• Tank and pipe sprayable coatings• Self-leveling waterproofing and sound damping

adhesives for use between floors in buildingand for basement joints

• Foamable (intumescent or swellable)formulations

• Vibration absorption membranes, gels, andfoams for railroad tracks

Properties Provided By Poly bd® ResinsDue to the molecular structure of the Poly bd® resins,the resulting polyurethane products exhibit some uniquecharacteristics that are especially valued in theconstruction uses. These characteristics are discussedindividually.

Hydrolytic StabilityThe hydrophobic backbone of Poly bd® resin impartsexcellent hydrolytic stability to the finished product,surpassing properties of any other type of poly-urethane. Poly bd®-based urethanes exhibit a lowwater absorption rate, even in boiling water. TheMoisture Vapor Transmission Rate (MVTR) is lowerthan conventional products derived from polyether orpolyester polyols. Some systems can even cureunderwater with no change in the product’s finalcharacteristics.

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For example, a simple 2-component polyurethaneformulation based on Poly bd® R45HTLO resin and apolymeric MDI shows less than 0.01% weight uptakeafter being immersed in water for a day at roomtemperature, and less than 0.20% weight gain whenimmersed in boiling water for 2 hours.

Table 1 describes two starting formulations and theMVTR values of the cured products according to thestandard ASTM E96 (38 oC / 90% RH) method.

also retain their elastic properties at high temperature,the materials produced with Poly bd® resins maintainoutstanding elasticity and elastic return when subjectedto temperature cycling.

Chemical ResistancePolyurethane elastomers based on Poly bd® resinsexhibit excellent resistance to aqueous inorganic acidsand bases. This characteristic is mainly due to the sturdycarbon-carbon bonds in the polybutadiene backbone.This property is important in applications requiringlong-term exposure to acidic and alkaline water, suchas sealants, coatings and membranes for landfills,tanks and pipes. Moreover, Poly bd® resin-basedpolyurethane elastomers have outstanding resistanceto brine.

The Poly bd®-based urethanes will swell to a certainextent when exposed to solvents. However, unlikeasphalt or even thermoplastic-modified asphalts, whichdissolve readily in solvents, the crosslinkedpolyurethane will maintain its integrity. Thischaracteristic allows the Poly bd®-based poly-urethanes to be used as a sealant in airport pavements,where they be exposed to aviation fuel spills or deicingfluids.

AdhesionSince Poly bd® resins have a low surface tension, theyreadily wet most common substrates such as concrete,wood, metallic surfaces, glass, plastics and cement.This property provides the necessary condition forestablishing good adhesion.

Poly bd® resins can be formulated as two-componentadhesives and sealants or as moisture curableprepolymers.

Compatibility With Asphalt and Process OilsPoly bd® resins are compatible with many hydrocarbonoils, chlorinated oils, asphalts and other related, low-cost materials. Such mixtures can be cured withconventional di-isocyanates to produce oil- or asphalt-extended elastomers. The cure time of preparingasphalt-extended polyurethane with Poly bd® resin canalso be controlled with catalysts.

Low Temperature Flexibility/High TemperatureResistancePolyurethane elastomers based on Poly bd® resinsexhibit outstanding low temperature properties whichare attributed to the “rubbery” polybutadienebackbone. The brittle point of Poly bd® resins is -75oC (-100 oF), so incorporation of Poly bd® into aformulation usually results in a low brittle point for thefinished product. For example, the brittle point offormulations highly filled with asphalt and process oilscan typically be -40 oC (-40 oF). In such formulations,only one brittle point is observed, showing that Polybd® resin is fully compatible with the asphalt andprocessing oils. Good low temperature flexibility isespecially critical for the joint sealants or crack-bridgingapplications. At low temperatures, the gap betweenjoints or cracks becomes wider as a result of thesubstrate shrinkage. Thus, a product with excellentelongation at low temperature is ideal for thoseapplications. In addition, since Poly bd® formulations

Formulation(parts by wt.)

Non-filled

Asphalt-extended

Poly bd® R45HT resin 100 100Chain extender (2-Ethyl-1,3-Hexanediol) 10 10

Asphalt (pen. 180/220) 200Isonate 143L(NCO index=1.05) 33.6 36.2*

MVTR (g. 2mm/m2.24hr) at 2mmthickness of the samples 5.16 2.14

* The quantity includes the isocyanate equivalency of the asphalt.

Table 1

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Process oils, such as soybean oil, are generally usedas plasticizers to reduce the viscosity, hardness, andcost of elastomeric systems. Process oils can provideimproved physical properties, such as increasing theelongation at break of the cured material.

Asphalts such as AC20 or AC5 are fully compatiblewith Poly bd® R45HTLO resin, but are not ascompatible with Poly bd® R20LM resin, which is oflower molecular weight and has a higher concentrationof polar hydroxyl groups. Polyurethane formulationsbased on Poly bd® resins accept large quantities ofasphalt. However, the asphalt used needs to have alow moisture content to reduce the side reactionbetween water and isocyanates during the curingreaction. This can be achieved by addition of molecularsieves into the formulation, where they act as a waterscavenger.

In joint sealing or crack filling applications, asphalt-modified Poly bd® urethanes have several advantagescompared to SBS-modified systems. First, thepreparation of asphalt-modified urethanes based onPoly bd® resins is possible at room temperature,whereas SBS resins are often melted at elevatedtemperatures prior to formulation. Furthermore, Polybd® pourable systems (joint sealants) can be formulatedwithout solvents. Not only is this attractive for theenvironment, but this also can lead to improved finalproperties, since there is no shrinkage andembrittlement of the final material caused by theevaporation of solvents. The asphalt-modified Poly bd®

urethanes produce a thermoset network which has

good sag resistance at high temperature and whichmaintains high elongation at break and elastic returnover a wide range of temperatures. In addition, therut and solvent resistance properties of Poly bd®-modified asphalt are superior to those of SBS-modified asphalt as a result of this thermoset structure.

The elastic modulus versus the temperature of an SBS-modified asphalt system and an asphalt-extendedpolyurethane formulation based on Poly bd® are shownin Figure 1 below. The elastic modulus is measuredby DMA (Dynamic Mechanical Analysis).

Figure 1 shows that even though the modulus is thesame (145 psi) for both systems at room temperature,the modulus of SBS-modified asphalt becomes10times lower than that of the Poly bd® resin-modifiedsystem at 100 oF. This suggests that the SBS-modifiedasphalt system softens significantly at elevatedtemperatures. At -20 oF the Poly bd® urethane-modified asphalt is still elastomeric, having a modulus10 times lower than that of the SBS-modified product.

Compatibility With High Loadings Of FillersPoly bd® resins are known for their ability to acceptlarge amounts of fillers without adverse changes in theproperties of the final product. Common fillers suchas calcium carbonate, silica, clay, aluminum trihydrate,carbon black and titanium dioxide are dispersed easilyin Poly bd® resins. The optimum amount of filler isdetermined based on the balance of properties, suchas viscosity, hardness, elongation at break, modulusand cost of the final products.

®0.5 175 45000 -40.6250.8 143.75 10000 -21.87510 106.25 450 31.25

175 68.75 175 68.751750 31.25 100 106.25

45000 -6.25 90 143.75100000 -21.875 85 175137000 -40.625

Figure 1 Modified Asphalt - SBS vs Poly bd

01

10100

100010000

1000001000000

-50 0 50 100 150 200

Temperature (oF)

Ela

stic

Mod

ulus

(psi)

SBS asphalt Poly bd asphalt

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Other Properties Of Poly bdÒ BasedFormulationsLike many other polyurethane systems, Poly bdÒ resin-based formulations generally have good abrasionresistance. Furthermore, the curing reactions of PolybdÒ resins occur with very low or even no exotherm,and with no or a very low shrinkage.

Starting Point Formulations

Cold-Applied, Two-Component System For AnExpansion Joint Sealant Or A Crack-FillingCompoundThe information in Table 2 is meant to serve as a startingformulation, and the process parameters andmechanical properties of the cured product can beadjusted to meet specific application needs. Forexample, a variety of types of asphalt, filler, andisocyanate can be substituted in this formulation.Furthermore, a portion of the asphalt can also be mixedwith the isocyanate in Part B. This can facilitate themixing of the isocyanate and the polyol blend bymatching more closely the viscosities of the Parts Aand B.

Self-Adhesive FormulationsPoly bdÒ resin-based polyurethanes can beformulated to make self-adhesive systems. Suchsystems may contain tackifying resins or asphalt. Thekey to prepare such a product is to cure the systemusing a NCO index of less than 1 (preferably between0.65 and 0.8). This can lead to a very good self-adhesive product. Further, since the glass transitiontemperature of the Poly bdÒ resin is very low, the tackis maintained at low temperatures, allowingcontractors to work under winter-like weatherconditions. Since this is a thermoset system, it alsomaintains its integrity at high temperature with excellentsag and chemical resistance.

Several starting formulations for self-adhesiveapplications are listed below; the specific propertiesdepend upon the asphalt, the type of MDI derivativesand the ratios of NCO to OH in the formulations.Based on Formulations 1A&B and 2A-D (see Table3 and 4), there appears to be no significant differencein performance of adhesives based upon either Isonate143L or Mondure MRS 2. Further, the tackiness canbe increased moderately by reducing the NCO indexfrom 0.7 to 0.65 (Formulations 2A-D).

Different Curing Methods For Poly bdÒ ResinFormulations

Two-Components SystemsMost of the formulations that use Poly bdÒ resins inconstruction applications are two-component urethanesystems, with or without asphalt. As previouslydescribed, a typical coating formulation can be: PolybdÒ R45HTLO resin (100 parts), chain extender,asphalt (100 - 200 parts), filler (100 - 200 parts),plasticizer additives (DUP, process oil, naphtenic orparaffinic oil) in one part, and MDI or an aliphaticisocyanate, or a prepolymer in the other part.

Although the preparation requires a mixing step (usuallyaccomplished with a mixer connected to a drill), thereis usually no need to heat the products before use.

An alternative way to cure Poly bdÒ resins at roomtemperature without using a polyisocyanate is to usemaleinized butadiene resins, such as RiconÒ productssupplied by Cray Valley Company, Inc. The resultingproduct is a polyester with improved high- and low-temperatures properties and good elastomericbehavior.

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Part A : Resin Ingredients Quantity NotesPoly bd® R45HTLO 100 Polyol2-Ethyl-1,3-hexanediol 15 Short polyol (chain extender) used to improve mechanical properties and

the mixing ratioAsphalt (120-150 pen.) 150 Soft grade used in road construction. AC20 or AC5 types of asphalt are the

most commonly usedCaCO3 150 Calcium carbonate (alternatively, clay, silica, or other fillers can be used)Molecular sieve 10 Absorbs the moisture: e.g., Siliporite SA1720 from Atofina

(www.siliporite.com)Dibutyltin dilaurate 0.1 Catalyst to adjust the pot life and the cure timeProcess oil 100 Naphthenic or phthalate based to reduce viscosityPart B: HardenerPolymeric MDI(mixing ratio) 100 parts A/

7.3 parts BIsocyanate. The curing agent for the polyols

Properties Of Part A FormulationViscosity (Part A formulation)@85 °C@70 °C@50 °C

18500 cPs44500 cPs200000 cPs

Viscosity depends on temperature and can be lowered by adding plasticizer(e.g., 20 pbw Santicizer 160 reduces viscosity by a factor of 2 or more)

Properties Of Final ProductHardness (15 sec.)@72 °F@14 °F

28 shore A45 shore A

According to ISO 86B (European standard)

Elongation at break@73 °F@14 °F@-22 °F

345%307%232%

Elongation at break remains high. The elastic return is almost 100% as well.Elongation can be higher with more plasticizer. SBS-asphalt systemsusually have 2% elongation at break @-22 °F

100% Modulus@73 °F@14 °F@-22 °F

122 psi461 psi

1,040 psi

The mechanical properties are measured according to ISO 527 (1993 1BA),at 50 mm/min (or 2 inch/min)

Tensile strength@73 °F@14 °F@-22 °F

300 psi810 psi1190 psi

ISO 527 (1993 1BA), at 50 mm/min (or 2 inch/min)

Tear strength@73 °F@14 °F@-22 °F

60 pli160 pli280 pli

According to ISO 34 method B

Table 2. Cold Applied, Two-Component System ForA) Expansion Joint Sealant orB) Crack-Filling Compound

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Table 3Formulations 2A-D

Table 4Formulations 1A & B:

Moisture Cure SystemsPoly bdÒ resins can be formulated to make aprepolymer, which, in turn, moisture cures to apolyurea. Cray Valley Company has developedstarting formulations to make prepolymers based onPoly bdÒ resins and MDI. However, since pre-polymers based solely on Poly bdÒ resin are veryhydrophobic, moisture cannot penetrate easily into thedeep sections of an article made from the prepolymerto initiate curing. Therefore, other more hydrophilic

Ingredients Quantity (pbw)A B C D

Poly bd® R45HTLO 27.27 27.27 27.27 27.27Asphalt AA5501 (77 pen.) 54.55 54.55 54.55 54.55Renoil 18.18 18.18 18.18 18.18T-12 0.006 0.006 0.006 0.006Mondur MRS 2 2.13 1.98 - -Isonate 143 L - - 2.33 2.16Index 0.7 0.65 0.7 0.65

Ingredients Quantity (pbw)A B

Poly bd® R45HTLO 27.27 27.27Asphalt AA4909 (407 54.55 54.55Renoil 18.18 18.18T-12 0.006 0.006Isonate 143L 2.16 -Mondur MRS 2 - 1.98NCO/OH Ratio .65 .65

polyols are usually incorporated into the formulationto enhance the moisture penetration. For example,Poly bdÒ resin and poly (propylene glycol) (PPG)polyether polyols form compatible blends, andprepolymers made from these blends are goodcandidates for the moisture cure system. For moreinformation about blending of Poly bdÒ resins withother polyols, please consult the Cray ValleyTechnical Bulletin “Compatibility Between Poly bdÒR45HTLO and Polyether/Polyester Polyols.”

Cray Valley also offers new low functionality Poly bdÒResins which generate prepolymers with lowerviscosity. For more information on these resins, pleaseconsult the Cray Valley bulletin entitled Poly bdÒResins in Adhesive Applications.

Aqueous Dispersions Based On Poly BdÒ

ResinsCray Valley Company has developed a waterbornepolyurethane dispersion (PUD) based on Poly bdÒ

R45HTLO resin (patent number WO 9948941). Aseparate brochure is now available to provide moreinformation about this technology.

Reactive Hot MeltA reactive hot melt based on Poly bdÒ resin can behandled exactly like a regular non-reactive hot meltwith the exception that the fully formulated producthas to be stored away from moisture. It can beprocessed at a relatively mild temperature and curedby moisture after being applied. The crosslinkedproduct has a good elastic return and exhibits improvedproperties at low and high temperatures.

The information in this bulletin is believed to be accurate, but all recommendations are made without warranty since the conditions of use are beyond Cray Valley Company'scontrol. The listed properties are illustrative only, and not product specifications. Cray Valley Company disclaims any liability in connection with the use of the information,

and does not warrant against infringement by reason of the use of its products in combination with other material or in any process.