b'Edge Cavitation is ain which the exterior edges of in dard isto a4-foot by 8-foot (1 xm) polyisocyanurate conditionsulationappliedtypical.22.4 board exhibit concave depr .cavitation is generally believed to beinsulation board, itldfor shrinkage or expansion ofto 3.8 essions Edgewou allowupinches aring defect that once was associated most fr with the(97 mm) in the longEven modest shrinkage cantr ively manufactu equentlydimension.resul in elatchange in blowing agents that occurred in the early 1990\'s; however,is stillwide gaps between tightlyinsulation boards, which can impact roof itbutted reported occasionally.system performance. Currently, edge cavitation is caused most often when art ofCrushing or Powdering sometimes is attributable tooff-ra othat is mino amoun anti mix usedSmall amoun Even water isas an ingredient in the manufacturing process.tstoo rich in isocyanate, resulting in foam that is too brittle.minor loads of water sometimes are added during the manufacturing process to generateon the in ion\'sincluding normal roof system installation trsulat surface,affic, car dioxide as aagent. The carbon dioxide can be useful incan crush the foam and tu it to powder if the mix isra o. Thiscan bonco-blowingrnoffti also improving some of the foam\'s physicalWhen changes were fir cause the facer sheet to delaminate from the foam core. properties.st made in the blowing agent, it was not known that the blowing agent (HCFCCrushing or powdering also can be caused by concentr and/or repetiated 141 b) had ato dissolve inpolymer matrix han thetive traffic on the insulation\'s or mem surface. This condition usually greater tendencythe foam\'st branes Ifsignificantthetoer previous blowing agent (CFC-11) did.aamount ofblowingwill be confined onlyhigh traffic areas, rath than other portions of the roof. agent dissolves into the cell walls,walls are weakened. the Also,chemical reactioncomponents in the production of thebetween the foam produces heat, with temperature withinreaching to the foam300F (149 C) during manufacturing and curing. The high reaction temperatures cause- - . AMERICA\'S LARGEST sure when the product cools. Ifdioxide isatmosphericof- -carbonpresent (e.g asresult- - -the gas pressure within the cells to be less than the ambient.,thepres - ROOFING, SIDING & .- -.-,, ,__,. ~ using aof waterthe process), the carbon dioxide will diffuse-.~ ~small amountin-put of the cells f rthe airdiffuse into the cells, WINDOWS WHOLESALER aste thancomponentsmagnify Supply Co. inc. ing the pressuren between the foam cells and the environment. differe tial The combination of weakened cell walls and great pressure differential cre 45 MIDWEST LOCATIONS ates elongated cells that are toofor the board\'s thickness. weekThis occurs most rapidly at the board\'sl infoam structure and boardBaraboo, WI920-9211=Pontiac, MlWest Allis, WI edges, resu tingpoor608-355-001 1414-47Hl600 edge cavitation.Freeport, IL248-334-3072 ~~~!~$t3o~815-232-0808Rochelle. IL~i~;;~~IL \',.Ml815-561-0333 Cupping or Bowing can be caused by an off-ratio mix; an turingGrand $apids, ma ufacCape Gir~e!!U, MO- 616-541 -4848 defectcreates distorted cell structures that are distributed unevenly within5733357222 that the foam\'s thickness. The uneven distribution of the cells creates inherent~;t~J~3/IA .dimensionalinstability and will exhibit substantially different compressive~ft.!Et~~hL strengthin the board\'s length, width and th When placed under1 valuesickness.~1d7\'~~:lat\'ltinght?~t~t;\' WI1 load, the board will resist the load differently, resu in cupping or bowing.~1 Kalam\'iiZ00 Ml Cicero,Jt._ Cupping or bowing also can occur when one of the board\'s facers gets wet.708-222-822,!\'6f!Rl49at;~78 ichlawrence,.JN As the facer dries, that side of the board shrinks, wh exerts unbalancedCollinsv\\ue, IL317546-3100"-618-345,150:0 forces within the board.top surface ofboard in acanOavenport 1lALouisville,tY Thethe topbundle also 502-\'637"13877 become wet if theinsulation is not properly protectedfrom precipitation.319323-4900Madison.\'Wi 608\'258-8880 happens, these\'f\'lain, When thisboards may become cupped.~1el~1~~6s~lMir.1"MN Cupping of boards as a resultexposure to precipitation typically is theDes Moines,IA.\\H-479\\2!1 of 515265-6135Miller,. IN result of inadequate packaging ofinsula:ionat the manufacturingDubuque, IA219-938-41$4Warreh,;Mr thebundles siteorinadequatematerialhandling, storage or application. The cupped319-557-9920:;~~tc.~ 1~:8\'11\'757\'3500 1Elkhart, IN om219-295-2466Watertoo.{A boards that result fr wetness generally will appear in randomlocationsMundelein, iL.;;""319-2S7-771!2 Farmington, MO. _ 8.i!l\'.-949-2:MJJthroughout the roof. Itldunusualall of the boards inbundle573-431-7076Muskegon Hts~.Wausau, WI wou beforanyofM1715-845.jl271 insulation to be wet only on their surfaces.Fond du Lac, Wl231-733-1264 Shrinkage of insulation boards generally is associated with an off-ratio foam mix. However, ASTM Ca ows up to a 4linear chan1289ll percentge, ,representing the pro dimensional stability when conditioned at 1duct\'s58F ?DC) and 97 percent relative humidity fordays. seven The ASTM methodology involves small-scale tests. However,the stan-if'