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Nondestructive testing of defects in adhesive joints

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Synthesis, cur<strong>in</strong>g and characterization <strong>of</strong> tetraglycidyl epoxy res<strong>in</strong><br />

D.Armstrong*, V. Agneeswaran and Dr.B.Kothandaraman #<br />

Department <strong>of</strong> Rubber and Plastics Technology,<br />

Madras Institute <strong>of</strong> Technology, Anna University Chennai<br />

E-mail:armstrongmit@gmail.com, bkraman@mit<strong>in</strong>dia.edu<br />

Abstract:<br />

Epoxies generally out-perform most other res<strong>in</strong> types <strong>in</strong> terms <strong>of</strong> mechanical properties<br />

and resistance to environmental degradation, which leads to their almost use <strong>in</strong> aircraft<br />

components. It has outstand<strong>in</strong>g thermal and adhesion properties. Some <strong>of</strong> these res<strong>in</strong>s can be<br />

cured at room temperature, but heat can be used to accelerate the cure <strong>of</strong> the epoxy. Among the<br />

high temperature epoxy res<strong>in</strong>s, TetraGlycidyl Diam<strong>in</strong>o Diphenyl Methane can provide high crossl<strong>in</strong>k<strong>in</strong>g<br />

density, so that hardened bodies obta<strong>in</strong>ed from the known composition exhibits both high<br />

modulus and high heat resistance which is <strong>in</strong>evitable for matrix materials for the advanced<br />

composites used <strong>in</strong> aerospace, electronics, automotive and other <strong>in</strong>dustries. In the present<br />

<strong>in</strong>vestigation, TetraGlycidyl Diam<strong>in</strong>o Diphenyl Methane was synthesized through glycidation <strong>of</strong><br />

4, 4’-Diam<strong>in</strong>o Diphenyl Methane with a large excess <strong>of</strong> Epichlorohydr<strong>in</strong> under controlled<br />

reaction conditions. Diam<strong>in</strong>o Diphenyl Methane (specifically <strong>in</strong>creases temperature and chemical<br />

resistance), Diam<strong>in</strong>o Diphenyl Sulphone (DDS)and Triethylene Tetram<strong>in</strong>e(TETA) were used for<br />

cur<strong>in</strong>g. The formulated cur<strong>in</strong>g mixture was cured as per the cur<strong>in</strong>g schedule described. The<br />

molecular structure <strong>of</strong> tetraglycidyl diam<strong>in</strong>o diphenyl methane was confirmed by Nuclear<br />

Magnetic Resonance Spectroscopic technique. The degradation behavior <strong>of</strong> cured samples was<br />

studied by thermo gravimetric analysis. The res<strong>in</strong> was cured with the above mentioned 3 am<strong>in</strong>e<br />

curatives and their properties were compared us<strong>in</strong>g Differential Thermal Analysis (DSC)<br />

Introduction:<br />

Epoxy Res<strong>in</strong>s are class <strong>of</strong> thermoset materials extensively used <strong>in</strong> structural and<br />

specialty composite applications because they <strong>of</strong>fer a unique comb<strong>in</strong>ation <strong>of</strong> properties that are<br />

unbelievable with their many desirable properties, such as good adhesion, excellent chemical,<br />

thermal stabilities and electrical properties. The outstand<strong>in</strong>g adhesion to various substrates makes<br />

epoxy res<strong>in</strong>, an important and efficient res<strong>in</strong> system <strong>in</strong> <strong>adhesive</strong> <strong>in</strong>dustries. In 1970 s, Ciba-<br />

Geigy corporation developed a series <strong>of</strong> glycidylated res<strong>in</strong>s based on hydanto<strong>in</strong> and Shell<br />

Technologies <strong>in</strong>troduced the glycidylated res<strong>in</strong>s <strong>of</strong> hydrogenated bisphenol-A, but <strong>in</strong> both<br />

<strong>in</strong>stances commercial success was limited. Epoxy <strong>adhesive</strong>s can bond a wide variety <strong>of</strong> substrates<br />

with high strength particularly metals. They have been used to replace some traditional metal<br />

work<strong>in</strong>g methods <strong>of</strong> jo<strong>in</strong><strong>in</strong>g like nuts and bolts, rivets, weld<strong>in</strong>g, crimp<strong>in</strong>g, braz<strong>in</strong>g and solder<strong>in</strong>g.<br />

Epoxy res<strong>in</strong> <strong>adhesive</strong>s are used ma<strong>in</strong>ly <strong>in</strong> niche applications rather than as general purpose<br />

<strong>adhesive</strong>s. Good adhesion to nonporous surfaces allows them to be used <strong>in</strong> demand<strong>in</strong>g situations.<br />

In the present <strong>in</strong>vestigation, tetra functional epoxy res<strong>in</strong> was prepared from 4, 4’diam<strong>in</strong>o<br />

diphenyl methane and was cured with Diam<strong>in</strong>o Diphenyl Methane (DDM), Diam<strong>in</strong>o Di<br />

phenyl Sulphone (DDS) and triethylene tetram<strong>in</strong>e (TETA). The thermal stability <strong>of</strong> cured<br />

TGDDM res<strong>in</strong>s were studied by thermogravimetry <strong>in</strong> nitrogen atmosphere at a heat<strong>in</strong>g rate <strong>of</strong> 10°<br />

C/m<strong>in</strong>, as a systematic thermal study on the selected res<strong>in</strong> system was very limited.

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