Anaerobic adhesives testing

Anaerobic adhesives. Test nnethods for anaerobic adhesives nnay be obtained fronn the Ministry of Defence under DTD 5628 or from HMSO. Cyanoacryiate adhesives. Test methods for cyanoacrylate adhesives may be obtained from the Ministry of Defence under TS 468 and TS10168. 

Testing of Anaerobic Adhesives. Testing standards and performance specifications for anaerobic adhesives and sealants have been established by government agencies and industrial organizations in several countries. In the United States there are military specifications for thread lockers, sealants, and retaining compounds. Many of these specifications are being superseded by commercial standards. 

In Germany, standards have been published describing the Compression Shear Test (DIN 54452), Dynamic Viscosity Determination of Anaerobic Adhesives by Rotational Viscometer (DIN 54453), Initial Breakaway Test at Bonded Threads (DIN 54454), and Torsion Shear Test (DIN 54455). DIN 54455 is particularly interesting since it is one of a very few tests in which a nut and bolt (MIO) are seated to a measured torque before the anaerobic sealant is allowed to cure. 

The International Organization for Standardization (ISO) has finalized an International Standard (ISO/DIS 10964 1993) Adhesives Anaerobic Adhesives— Determination of Torque Strength of Anaerobic Adhesives on Threaded Fasteners. This standard describes testing procedures for liquid and preapplied sealants using manual and graphical procedures. 

Slant shear test, loaded in compression, for resins used in construction concrete substrates used Collar and pin bonded with anaerobic adhesive and loaded in tension... 

In this Institute, there are approximately 200 research personnel and one fourth of them are working on adhesives in two laboratories, one pilot-plant, one testing group and one adhesive-film manufacturing and testing facility. Their research and development broadly covered structural adhesives, strain gauge adhesives, wood adhesives, second-generation acrylics, anaerobic adhesives and composite binders. Their products varied from J-01 to J-53. There were at least thirty different kinds of adhesive and sealant, for example, nitrile-phenolics, modified epoxies, acrylics and epoxy-phenolics. 

Figure 2.18 Effect of surface finish and gap size on the shear strength of an anaerobic adhesive. Adhesive DTD 5633/G2 tested to DTD 5628 using given finish and gap.

Table 2.3 Vs in.-16 tpi bolt vibration test effect of anaerobic adhesives on vibration resistance...

At room temperature, a good conventional anaerobic adhesive begins to harden within a few minutes of assembly and components can often be handled quite satisfactorily after 10-20 minutes. However, without an accelerator or elevated temperature, full adhesive strength will not develop for one to two hours. Hence normal batch testing is usually carried out after three hours but for full standardisation and type testing a 24-hour cure time is allowed. 

But do not overlook the fact that standard tests use standard test pieces and cannot compare as an assessment of suitability with the testing of the actual bonded components themselves. A classic illustration is the torque testing (DTD 5628 Method D) of anaerobic adhesives compared to the actual vibration testing of locked threaded fasteners (see Sections 2.3.2 and 3.6). The former test gives a strength ranking - needed for design and quality control - while the latter shows quite clearly that all these adhesives resist severe vibration - their raison d etre. The two are not comparable but are often confused. 

Dragoni, E. (2003). Fatigue testing of taper press fits bonded with anaerobic adhesives. The Journal of Adhesion, 79(8-9), 119-lM. 

ISO 10964 (August 15, 1993) Adhesives—Anaerobic adhesives— Determination of torque strength of anaerobic adhesives on threaded fasteners describes testing procedures for liquid and preapplied sealants. 

The change by a manufacturer of automated teller machine rollers from one anaerobic adhesive to another to meet performance requirements is examined. Topics covered include assembly procedures, testing and cost savings in the two years that Hiawatha Rubber has been using the anaerobic adhesive, only two bonded rollers out of about 16,000 units have failed - each time attributed to improper application of the adhesive. Details are given. HIAWATHA RUBBER CO. 

Standards ASTM D 4562 and ISO 10123 describe a shear test in which the specimen is a pin bonded inside a coUar. The test uses a press to force the pin through the collar, which rests on a support cylinder. The test results are the load required to initiate failure divided by the bonded area between the pin and the collar. This type of test is particularly suited to test anaerobic adhesives. The shear strength determined with this test is only an average value because the stress distribution is not uniform along the overlap (Neme et al. 2006 Martinez et al. 2008). ASTM E 229 also uses a pin-and-coUar type of specimen except that here torsional loadings cause failure. The adhesive stress distribution in this case is more uniform and may be used to determine the adhesive shear modulus and strength. However, the standard was withdrawn in 2003. 

Until relatively recently the most widely used specifications for anaerobic adhesives were the American MIL specifications which have been criticised because they were of little relevance to quality control. The Ministry of Defence has therefore issued specifications DTD5628-5633 which cover test procedures and performance requirements for sixteen materials. Five strength bands and a wide range of viscosity levels are defined. 

Parker et al. (30) reported the synthesis of phosphorous containing bismaleimides and demonstrated their outstanding non-flammability characteristics. Graphite fabric composites prepared from such P-containing BMI as a matrix resin show a LOI of 100 and an anaerobic char yield of 88% at 700 °C. Other P-containing BMI have recently been synthesized (31) for example, bis(3-maleimidophenoxy-4-phenyl)phenyl phosphine oxide (Figure 8) has been tested as a composite matrix resin with the aim of improving the fibre/resin interfacial adhesion. 

Many strains over 200 were isolated from seawater samples and many of them showed adhesive growth to culture flasks and/or flocculated growth. More than 10 strains were tested to examine algal productivity, starch content and ethanol production. Table 1 shows some strains having a productivity of ca. 30 g/m2 d, accumulated a starch more than 30 % (vs dry weight), but had a variety of starch conversion rate to ethanol. One of the excellent strains, Chlamydomonas sp. YA-SH-1, which was isolated from the Red Sea showed (1) a growth rate of 30 g-dry biomass/m d, (2) a starch content of 30 %(dry base), and (3) a conversion rate from starch to ethanol of 50 % in the dark and anaerobic condition. 

One of the tests is maintaining strength through a gap. This can be affected by air inhibition, as well as by the diffusion of accelerators. In another test, air was beaten into several adhesive formulations. The aerobic adhesives were only marginally affected by air inclusion when cured between surfaces. Like anaerobics, fillets or adhesive squeezed outside of a bonded joint will remain uncured unless exposed to UV light. 

In the last test, a porous material, pine wood, was chosen as a substrate because it assures that air is to remain in intimate contact with the curing adhesive. The ability to lock the threads of an iron nut and bolt without use of an activator is a recognized test for determining whether a formulation is capable of anaerobic cure. 

To obtain additional information as to the level of adhesion on aluminum adherends a series of anaerobically cured tensile lap shear specimens were fabricated and tested at room temperature. The results showed shear strengths of 925 + 20 psi and indicated good bonding... 

Anaerobic acrylic sealants or cyanoacrylates are known sensitizers, while the modified acrylic structural adhesives that cure in air more rarely cause allergy. Tosti et al. (1993) reported of three carpenters, each of whom became sensitized to wood paints and glues with butyl acrylate, 2-ethoxyethyl methacrylate, or a phth-late. Epoxy resin compounds are another commonly used group of adhesives, which contain resins (generally included in patch-test screening batteries), hardeners, and reactive diluents, as well as many other potentially harmful ingredients, such as tar, fillers, colorants, and other plastics. 

Anaerobics are ideal for locking and sealing threaded parts and, with few exceptions (discussed separately in Section 2.3.2.9), are normally the only adhesives to consider. A variety of vibration and impact tests have shown that even medium-strength grades out-perform all conventional means of maintaining bolt tension (see Table 2.3). Frequently the test specimens fail due to metal fatigue with the nut still firmly attached to the bolt shank. 

Weaker anaerobics should be used with soft alloy nuts and other threaded fasteners to prevent thread stripping during disassembly. Soft alloy and plastics fasteners exhibit a lower removal torque than their steel equivalents, because less hoop stress is generated as the adhesive is crushed during removal. Despite this apparently lower performance (remember removal is only a test method ranking) the parts will still be effectively locked and resistant to vibration. 

In industries that are bonding plasticized materials, there are some specific tests to measure for instance peel strength before and after accelerated aging test. The A and S suppliers, who know the raw materials included in their formulations, can tell quickly whether a given adhesive should be sensitive or not to oils, greases and plasticizers. Some adhesives are sensitive to oils (vinyl emulsion glues), some are not (epoxies, anaerobics, etc.). 

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