Main­te­nance mat­ters

DEMM Engineering & Manufacturing - - CONTENTS -

Mod­ern in­stant ad­he­sives can of­ten help to make industrial man­u­fac­tur­ing pro­cesses faster, safer and more eco­nom­i­cal. They also open up com­pletely new de­sign op­por­tu­ni­ties for se­ries pro­duc­tion. But in or­der to get per­fect re­sults, the right choice of prod­uct is crit­i­cal. To make sure that all the benefits of this bond­ing tech­nol­ogy can be fully ex­ploited, Henkel’s Loc­tite brand of­fers a broad range of in­stant ad­he­sives tai­lored to meet the spe­cific needs of the man­u­fac­tur­ing in­dus­tries.

Ad­he­sive bond­ing is one of the most im­por­tant tech­niques em­ployed to join ma­te­ri­als in mod­ern man­u­fac­tur­ing pro­cesses to­day. When prop­erly se­lected and ap­plied, ad­he­sives can be used to achieve last­ing bonds be­tween vir­tu­ally all ma­te­ri­als in any com­bi­na­tion. Users can choose from a va­ri­ety of bond­ing tech­nolo­gies to find the best so­lu­tion for their ap­pli­ca­tion and re­quire­ments. In­stant ad­he­sives are play­ing an in­creas­ingly im­por­tant role in industrial man­u­fac­tur­ing where they of­fer many ad­van­tages over tra­di­tional ma­te­rial join­ing tech­niques like ul­tra­sonic and sol­vent weld­ing or me­chan­i­cal fas­ten­ing meth­ods such as clip­ping or bolt­ing.

Fast, ver­sa­tile and ef­fec­tive

In­stant ad­he­sives, also known as cyanoacry­lates, are ideal for bond­ing small and medium-sized parts to achieve a close fit in se­ries man­u­fac­tur­ing. The prod­ucts are ap­plied in dots or beads to one of the parts to be joined, ei­ther di­rectly from the er­gonom­i­cally de­signed, easy-to-use bot­tle or us­ing man­ual or au­to­matic dispensing de­vices. For best re­sults, the sur­faces of the parts must be clean and free of grease. Plas­tic parts can nor­mally be pro­cessed with­out any ad­di­tional sur­face prepa­ra­tion, as long as they are not heav­ily soiled. As soon as the parts have been joined, the cyanoacry­late cures within sec­onds by re­act­ing with the mois­ture on the sur­faces of the parts. This re­sults in rapid as­sem­bly op­er­a­tions as the bond­line de­vel­ops suf­fi­cient strength to al­low fur­ther pro­cess­ing af­ter only five to 20 sec­onds.

In ad­di­tion to speed­ing up pro­cesses, cyanoacry­lates also ad­here to a very broad spec­trum of dif­fer­ent ma­te­ri­als. They can be used to bond sim­i­lar or dis­sim­i­lar com­bi­na­tions of plas­tic, rub­ber, metal, tex­tile, wood or pa­per ma­te­ri­als – with­out prob­lems and with­out dam­ag­ing the ma­te­ri­als ei­ther chem­i­cally or ther­mally. This per­for­mance ca­pa­bil­ity makes cyanoacry­lates es­pe­cially well suited for bond­ing sen­si­tive ma­te­ri­als such as plas­tics, rub­ber or la­tex to one an­other or to met­als. An­other point in fa­vor of ad­he­sive bond­ing is that it achieves full-sur­face join­ing rather than join­ing only at iso­lated, highly stressed con­tact points as is usual with con­ven­tional tech­niques. Stress peaks can there­fore be avoided.

Be­cause they are so ver­sa­tile, as well as en­abling fast, easy and eco­nom­i­cal pro­cess­ing, cyanoacry­lates can now be found in many dif­fer­ent industrial ap­pli­ca­tions. Ex­am­ples in­clude bond­ing rub­ber feet to ABS hous­ings, at­tach­ing clips and switches to mo­bile elec­tronic de­vices, and form­ing f lex­i­ble gas­kets on steel. More­over, this bond­ing tech­nol­ogy can of­ten re­place me­chan­i­cal constructions such as the frames used for me­chan­i­cal fix­ing of heat-sen­si­tive ma­te­ri­als like foam. This re­sults in sim­pler and more es­thetic struc­tures that can be built faster while at the same re­duc­ing man­u­fac­tur­ing costs by sav­ing on ma­te­ri­als.

Mul­ti­pur­pose and spe­cialised prod­ucts

Cyanoacry­lates are gen­er­ally characterised by their abil­ity to cre­ate high-strength bonds with very good aging re­sis­tance, even in the small­est gaps. Even small amounts of ad­he­sive are suf­fi­cient to cre­ate high-per­for­mance bond­lines whose strength is of­ten higher than that of the ma­te­ri­als they join.

But choos­ing the right prod­uct is es­sen­tial to get the best re­sults. Loc­tite there­fore of­fers users a broad range of in­dus­tryproven cyanoacry­lates. While mul­ti­pur­pose prod­ucts al­ready de­liver very good re­sults for bond­ing a va­ri­ety of dif­fer­ent ma­te­rial com­bi­na­tions, the spe­cialty prod­ucts have ad­di­tional specif­i­cally en­gi­neered char­ac­ter­is­tics which con­sid­er­ably ex­tend the spec­trum of pos­si­ble ap­pli­ca­tions. Pow­er­ful so­lu­tions are avail­able even for dif­fi­cult-to-bond plas­tics such as PP, PE, POM, PTFE or sil­i­cones.

Each of the dif­fer­ent prod­uct cat­e­gories has been op­ti­mized as ap­pro­pri­ate for the ap­pli­ca­tions in­volved. For ex­am­ple, the elas­tomer-mod­i­fied cyanoacry­lates from Loc­tite of­fer good im­pact and shock re­sis­tance and are there­fore used to bond loud­speaker parts (fig. 1), the hous­ings for recharge­able bat­ter­ies in power drills, or sim­i­lar ap­pli­ca­tions. Flex­i­ble prod­ucts, on the other hand, can re­li­ably with­stand re­peated

twist­ing or bend­ing of the bonded ma­te­ri­als and are there­fore suit­able for bond­ing the plas­tic sheaths on the metal tem­ples of f lex­i­ble-frame sun­glasses or for at­tach­ing rub­ber pro­files to re­frig­er­a­tor doors made of painted metal (fig. 2). For trans­par­ent parts re­quir­ing very good op­ti­cal per­for­mance, light-cur­ing cyanoacry­lates will be the best choice. Th­ese ad­he­sives cure within sec­onds when ex­posed to UV or vis­i­ble light. And they re­main clear and trans­par­ent af­ter cur­ing (fig.3).

Gap-fill­ing bonds The scope of ap­pli­ca­tions in industrial man­u­fac­tur­ing pro­cesses has been dis­tinctly broad­ened by the re­cent ad­di­tion of the first gap-fill­ing cyanoacry­late, Loc­tite 3090. Since con­ven­tional cyanoacry­lates mostly have very low vis­cos­ity, they were only used to join close-fit­ting parts. This was a draw­back that se­verely re­stricted their range of uses. With Loc­tite 3090, Henkel has vastly broad­ened the ap­pli­ca­tion range of in­stant ad­he­sives, of­fer­ing an un­matched ca­pa­bil­ity to fill gaps up to 5 mm wide (fig. 4). The new in­stant ad­he­sive is suit­able for al­most all ma­te­ri­als, in­clud­ing met­als, most plas­tics, rub­ber and ce­ram­ics. Even por­ous sub­strates such as wood, pa­per and cork can be re­li­ably bonded with it.

Users also ben­e­fit from the sig­nif­i­cantly im­proved han­dling: The trans­par­ent cyanoacry­late is a high-vis­cos­ity gel, which al­lows eas­ier ap­pli­ca­tion to dif­fi­cult ver­ti­cal sur­faces – with­out drip­ping. An­other new fea­ture is the con­ve­nient two-cham­ber sy­ringe pack­ag­ing en­abling pre­cise and clean ap­pli­ca­tion. Un­like one-com­po­nent sys­tems, Loc­tite 3090 does not de­pend on the mois­ture on the sur­faces to cure, but has an ad­di­tional ac­ti­va­tor. The two com­po­nents are dis­pensed into an in­te­grated static mixer, which en­sures that cur­ing is trig­gered within the de­fined time­frame, re­gard­less of mois­ture or tem­per­a­ture, and that the com­po­nents are al­ways mixed in the right ra­tio. The ad­he­sive has a work­ing time of 90 to 180 sec­onds af­ter ap­pli­ca­tion. The bond is then strong enough for use or down­stream pro­cess­ing of the joined parts.

Light-cur­ing ad­he­sives make a vis­i­ble dif­fer­ence – ideal for bond­ing

clear and trans­par­ent ma­te­ri­als for a per­fect vis­ual ap­pear­ance.

For parts sub­jected to re­peated flex­ing there are spe­cially de­signed flex­i­ble cyanoacry­late ad­he­sives, which can be used to at­tach rub­ber pro­files to re­frig­er­a­tor doors or for sim­i­lar ap­pli­ca­tions.

Of­fer­ing an un­matched ca­pa­bil­ity to fill gaps up to 5 mm wide, Loc­tite 3090 has vastly broad­ened the ap­pli­ca­tion range of in­stant ad­he­sives.

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