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Test MethodologyDetermining The Experimental MatrixThe Selection of AdhesivesIt was desired to evaluate adhesives from all families that are bestsuited for bonding plastics. The families were identified as ethylcyanoacrylates, light cure, two part and no mix acrylics, silicones, hotmelts, epoxies, polyurethanes, and static mix acrylics. From each ofthese categories, an adhesive was then selected which was believedto be representative of the performance of that family of adhesiveswhen bonding plastics. The adhesives which were selected aretabulated below:The Selection of PlasticsThe various types of plastics which are currently available weresurveyed, and thirty of the most commonly used plastic types wereselected for testing. The specific formulations of these plastics whichwere evaluated were chosen in one of the two following ways:Specialty FormulationsSeventeen of the thirty materials were compounded specifically todetermine the effect different additives and fillers had on thebondability of the base resin using the following procedure:ADHESIVELoctite ® 380 Black Max ® Instant AdhesiveLoctite ® 401 Prism ® Instant Adhesive,MEDICAL: Loctite ® 4011 Prism ® Instant AdhesiveLoctite ® 401 Prism ® and 770 Prism ® PrimerMEDICAL: Loctite ® 4011 Prism ® /Loctite ® 7701 Prism ® PrimerLoctite ® 414 Super Bonder ® Instant AdhesiveLoctite ® 330 Depend ® AdhesiveLoctite ® 3105 Light Cure Adhesive,MEDICAL: Loctite ® 3311 Light Cure AdhesiveLoctite ® 3340 Light Cure AdhesiveLoctite ® 4305 Flashcure ® Light Cure AdhesiveFLUORESCENT: Loctite ® 4307 Flashcure ®Light Cure AdhesiveLoctite ® H3000 Speedbonder Structural AdhesiveLoctite ® H4500 Speedbonder Structural AdhesiveLoctite ® 3030 AdhesiveLoctite ® E-00CL Hysol ® Epoxy AdhesiveLoctite ® E-90FL Hysol ® Epoxy AdhesiveLoctite ® E-30CL Hysol ® Epoxy AdhesiveMEDICAL: Loctite ® M-31CL Hysol ®Epoxy AdhesiveLoctite ® E-20HP Hysol ® Epoxy AdhesiveMEDICAL: Loctite ® M-21HP Hysol ®Epoxy AdhesiveLoctite ® E-214HP Hysol ® Epoxy AdhesiveLoctite ® 1942 Hysol ® Hot Melt AdhesiveLoctite ® 3651 Hysol ® Hot Melt AdhesiveLoctite ® 7804 Hysol ® Hot Melt AdhesiveLoctite ® 3631 Hysol ® Hot Melt AdhesiveLoctite ® U-05FL Hysol ® Urethane AdhesiveLoctite ® Fixmaster ® Rapid Rubber RepairOEM: Loctite ® U-04FL Hysol ®Urethane AdhesiveLoctite ® 5900 ® Flange SealantDESCRIPTIONRubber-toughenedethyl instant adhesiveSurface insensitiveethyl instant adhesivesSurface insensitive ethyl adheisvesused in conjunction withpolyolefin primerGeneral-purposeethyl instant adhesiveTwo-part, no-mix acrylic adhesiveLight curing acrylic adhesivesLight cure adhesiveLight cure adhesivesTwo-part acrylic adhesiveTwo-part acrylic adhesivePolyolefin bonderFast setting epoxy adhesiveTough, flexible epoxy adhesiveClear, glass bondingepoxy adhesiveHigh strength epoxy adhesivesOne component heat cureepoxy adhesiveEVA hot melt epoxy adheisvePolyolefin hot melt epoxy adhesivePolyamide hot melt adhesiveReactive urethane hotmelt adhesiveTwo-part high performanceurethane adhesiveRapid rubber repairurethane adhesiveOEM: Two-part fast settingurethane adhesiveHeavy body RTV flange sealant1. A grade of the plastic which had no fillers or additives wasselected and tested for bond strength performance with theaforementioned adhesives.2. The most common additives and fillers used with each plasticwere identified.3. A separate formulation of the plastic was compounded witha high fill level of each of the identified common additivesand fillers.4. Adhesive bond strength evaluations were performed on thevarious formulations which were compounded.5. The results were analyzed to determine if the filler or additiveresulted in a statistically significant change in the bondabilityof the plastic from the unfilled resin within 95% confidence limits.Commercially Available GradesFor thirteen of the thirty plastics, commercially available grades wereselected to represent each major category available for that plastic.For example, when testing ionomer, grades were evaluated whichrepresented each of the major cation types. Moreover, whileevaluating phenolics, a grade was selected to represent each of theend use applications, such as general-purpose, glass-filled, heatresistant, and electric grades.84The Loctite ® Design Guide for Bonding Plastics, Volume 4
Determining The Test MethodThe lap shear test method ASTM D1002 is typically used todetermine adhesive shear strengths. However, because it wasdesigned for use with metals, it has several serious limitations whenevaluating plastics. For example, because plastics have much lowertensile strength than metals, the plastic lap shear specimens aremuch more likely to experience substrate failure than the metal lapshear specimens. This makes the comparative analysis of differentadhesives on a plastic very difficult because many of the adhesiveswill achieve substrate failure, rendering it impossible to identify theadhesive best suited for that material. Another major disadvantageto using the lap shear test method is that because plastics havemuch lower modulii than metals, they deform more during testing,which introduces peel and cleavage forces on the joint.Consequently, the lower the modulus of the plastic, the more it willdeform under load, and the less representative the experimentalshear strength will be of the actual shear strength which shouldhave been achieved on that material.Due to these limitations, a block shear test method (ASTM D4501) waschosen. Since block shear testing places the load on a thicker sectionof the test specimen, the specimen can withstand higher loads beforeexperiencing substrate failure. In addition, due to the geometry of thetest specimens and the block shear fixture, peel and cleavage forces inthe joint are minimized.LimitationsWhile the bond strengths in this guide give a good indication of thetypical bond strengths that can be achieved with many plastics, aswell as the effect of many fillers and additives, they also face severallimitations. For example, while the additives and fillers were selectedbecause they were believed to be representative of the mostcommonly used additives and fillers, there are many types of eachadditive and filler produced by many different companies, and differenttypes of the same additive or filler may not have the same effect onthe bondability of a material. In addition, the additives and fillers weretested individually in this guide, so the effect of interactions betweenthese different fillers and additives on the bondability of materialscould not be gauged.Another consideration that must be kept in mind when using this datato select an adhesive/plastic combination is how well the block sheartest method will reflect the stresses that an adhesively bonded jointwill see in “real world” applications. Adhesively bonded joints aredesigned to maximize tensile and compressive stresses, and tominimize peel and cleavage stresses, so the magnitude of the formertwo are generally much larger than the latter two. Thus, the shearstrength of an adhesive is generally most critical to adhesive jointperformance, but since all joints experience some peel and cleavagestresses, their effects should not be disregarded.Finally, selecting the best adhesive for a given application involvesmore than selecting the adhesive which provides the highest bondstrength. Other factors such as speed of cure, environmentalresistance, thermal resistance, suitability for automation, and price willplay a large role in determining the optimum adhesive system for agiven application. It is suggested that the reader refer to the chapterswhich explain the properties of the various adhesives in greater detailbefore choosing the best adhesive for an application.Although there are some limitations to the degree the informationprovided in this guide can be extrapolated, the data contained hereshould be invaluable in helping the end user quickly make comparativeevaluations of the bond strengths that various adhesive/plasticcombinations provide. Once the most promising combinations ofadhesives and plastics have been identified, it is important that testingbe performed on assemblies to insure that they will meet or exceed allperformance requirements.The Loctite ® Design Guide for Bonding Plastics, Volume 4 85
Page 3:
Table of ContentsIntroduction 2How
Page 6 and 7:
How To Use The Plastic Bonding Guid
Page 8 and 9:
Cyanoacrylate AdhesivesGeneral Desc
Page 10 and 11:
Hot Melt AdhesivesGeneral Descripti
Page 12 and 13:
Polyurethane AdhesivesGeneral Descr
Page 14 and 15:
No-Mix and Static Mix Acrylic Adhes
Page 16:
Acetal HomopolymerThermoplasticTrad
Page 20:
Acrylic-Styrene-Acrylonitrile (ASA)
Page 23 and 24:
ADHESIVE SHEAR STRENGTH(psi)(MPa)Ac
Page 25 and 26:
ADHESIVE SHEAR STRENGTH(psi)(MPa)Di
Page 27 and 28:
ADHESIVE SHEAR STRENGTH(psi)(MPa)Ce
Page 29 and 30:
ADHESIVE SHEAR STRENGTH(psi)(MPa)Ep
Page 31 and 32:
ADHESIVE SHEAR STRENGTH(psi)(MPa)Po
Page 33 and 34:
ADHESIVE SHEAR STRENGTH(psi)(MPa)Io
Page 35 and 36: ADHESIVE SHEAR STRENGTH(psi)(MPa)Li
Page 37 and 38: ADHESIVE SHEAR STRENGTH(psi)(MPa)Ph
Page 39 and 40: ADHESIVE SHEAR STRENGTH(psi)(MPa)Po
Page 53 and 54: ADHESIVE SHEAR STRENGTH(psi)(MPa)Lo
Page 73 and 74: ADHESIVE SHEAR STRENGTH(psi)(MPa)St
Page 75 and 76: ADHESIVE SHEAR STRENGTH(psi)(MPa)Vi
Page 77 and 78: Surface TreatmentsAdhesive Abrading
Page 79 and 80: Adhesive Joint DesignIntroductionIn
Page 81 and 82: TitleDesign GuidelinesEngineers mus
Page 83 and 84: Shortening bond overlaps reduces bo
Page 85: Softening and weakening of the surf
Page 89 and 90: Block Shear Test Method1. Assemblie
Page 91 and 92: ViscosityViscosity is a product pro
Page 93 and 94: Index of Trade NamesTrade Name Plas
Page 95 and 96: Trade Name Plastic Type Manufacture
Page 97 and 98: AcknowledgmentsThis manual would no
Page 99: For more information, please call 1
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