FAQ > Urethane Adhesives
I   have   a   Volkswagen   Beetle,      when   I   called   Phoenix   Glass   for   a   price   on   a new   OEM   replacement   windshield,   the   customer   service   representative   told me   my   VW   called   for   the   application   of   a   different   type   of   adhesive   called high   modulus   urethane.      I   understand   it's   a   form   of   urethane   but   how   does   it differ from the type normally used? The    short    answer    is    that    your    VW,    along    with    many    other    German    automobile manufacturers,    such    as    Audi,    BMW,    Volvo    and    Mercedes,        have    mandated    a    rigidity requirement    on    the    vehicles    that    they    produce.        In    order    to    meet    that    engineering requirement   and   retain   the   structural   integrity   of   the   vehicle   it   is   necessary   to   use   a   different type   of   urethane   to   bond   the   windshield,   back   glass   and   side   windows   to   the   vehicle.      High Modulus   urethane   adhesives   provide   the   extra   strength   to   help   the   vehicle   resist   torsional   twisting   as   well   as   help   quiet   and   stabilize   the vehicles   ride.      Another   added   plus   that   is   built   into   High   Modulus   Urethane   is   that   it   preserves   radio,   cell   phone,   and   global   positioning system reception in an OEM antenna encapsulated windshield or rear back glass window.
The   long   answer    is   now   that   you   have   learned   how   important   it   is   and   how   it   all   works   together   we're   going   to recap   a   bit   as   we   get   into   why   it's   so   important   to   not   only   make   sure   your   new   windshield   is   installed   with   a High   Modulus   adhesive   but   with   the   "right   OEM   type"   of   High   Modulus   Urethane.      If   you   read   multiple   adhesive manufacturers   literature   to   determine   whether   their   urethane   is   high   modulus,   you   will   find   different   definitions of   the   term.   Some   manufacturers   define   their   windshield   adhesives   as   "modulus   enough"   or   "high   on   the   OEM specification   for   high   modulus   classification,"   but   does   that   really   mean   that   they   can   be   classified   as   high modulus   adhesives?      To   answer   that   question,   first   we   must   define   what   high   modulus   means.      High   modulus   is a   rigidity   requirement   of   cured   adhesive.      It   measures   the   ability   of   the   adhesive   to   withstand   a   variety   of stresses   and   still   return   to   its   original   form.      It   must   be   able   to   withstand   tension,   compression,   shear   and torsion   without   adhesive   or   cohesive   failure.      High   performance   and   luxury   vehicle   manufacturers   specify   and use   adhesives   like   BETASEAL   ONE   because   they   can   use   it   as   a   structural   element   to   stabilize   the   vehicle   which   improves   the   ride   and reduces   rattles,   vibrations   and   other   vehicle   noises.   High   modulus   adhesives   have   a   much   higher   resistance   to   stress.      This   characteristic enables   high   modulus   adhesives   to   stiffen   the   vehicle   body,   improving   handling   and   overall   stability   in   vehicles   designed   to   use   this advanced   technology.      Vehicle   designers   place   greater   demands   on   high   modulus   adhesives.      The   adhesive   bears   much   more   of   the pushes,   pulls   and   twists   associated   with   everyday   driving.      High   modulus   adhesives   must   have   a   higher   elastic   resistance   than   normal   so they   will   not   deform   or   rupture   under   the   increased   stress.      So   how   do   adhesive   manufacturers   know   which   property   and   specification should   be   met   in   order   to   be   high   modulus?   To   clarify,   it   must   be   understood   that   an   adhesive   is   either   high   modulus   or   it   is   not.      There is no in between modulus that is good enough for all vehicles.
According to Mercedes specifications, in order for an adhesive to be considered high modulus, it must meet 2.5 MPa. Dow   Automotive's   Betaseal   One   Urethane   Adhesive   passes   the   defining   test   to   be   called   high   modulus   with   a   shear   strength   of   2.7   MPa   at full cure. The Bottom Line A   urethane   manufacturer   cannot   claim   to   be   "on   the   high   end   of   the   specification"   and   therefore   be   considered   "modulus   enough"   for   all vehicles.      Any   urethane   manufacturer   claiming   to   be   high   modulus   should   be   able   to   provide   supporting   data,   to   include   laboratory testing as well as technical data. I’ve been reading your website about High Modulus Urethanes and it sounds like it would work better than the type used in my GM Vehicle.  If I have a new windshield installed wouldn’t it be better to use it.
Volkswagen Beetle Types of stress Types of stress
It   does   sound   better   but   your   vehicle   isn’t   designed   for   it.      According   to   I-CAR,      Using   a   high   modulus   adhesive   when   it's   not   specified   or when   it   was   not   designed   into   the   vehicle   could   alter   the   vehicle   by   making   it   stiffer   than   original   design   and   cause   other   potential problems.
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What is Urethane Adhesive? Polyurethane   better   known   as   Urethane   is   an   adhesive   that   is   specially   made   for   sealing   and   bonding   a   windshield,   side   window,   quarter glass,   and   rear   window   back   glass   in   the   automotive   industry.      Even   though   Europe   was   already   using   urethane   in   some   of   it’s   vehicles the   first   reported   use   in   an   American   produced   car   was   in   a   1973   Oldsmobile   windshield   and   rear   back   glass   window.      In   1974   it   was used   exclusively   in   all   General   Motors   as   well   as   American   Motors   vehicles.      In   later   years   GM   also   began   using   it   to   bond   rubber   gasket set windshields in GMC and Chevrolet pick up trucks.
In   today’s   foreign   and   domestic   vehicles   urethane   is   the   only   adhesive   technology   used   in   high   performance   auto   glass   bonding applications   because   urethane   is   capable   of   withstanding   high   levels   of   deformation   with   little   loss   of   adhesive   strength   and   performance.     Urethanes   are   tough   and   and   abrasion   resistant.      The   Betaseal   urethane   adhesives   we   use   here   at   Phoenix   Glass   are   formulated   to   be durable enough to withstand long term weather exposure.
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