Contents - Akademi Sains Malaysia

ASM Sci. J., 7(1)A Study on the Effects of Environmenton Curing Characteristics of Thixotropic andRoom Temperature Cured Epoxy-basedAdhesives Using DMTAZ. Ahmad 1 *, H. Rohana 1 and P. Md Tahir 2This study investigated the thermal properties of three room temperature curing adhesives containing nanoparticleswhich were thixotropic and shear thinning which allowed injection into overhead holes when exposedto different environmental conditions. Viscosity and shear stress of the adhesives were measured as a functionof shear rate. The thermal behaviour of the adhesives were measured using dynamic mechanical thermaland the glass transition temperature (T g T g increased withthe temperature increase, even though the adhesives were subjected to high humidity and this was due tofurther cross-linking. The results showed that room temperature cured epoxies were only partially cured atroom temperature.Key words: Glass transition temperature; DMTA; thermal properties; epoxy-based adhesive; nano- and microparticles;viscosity; humidity; rheological propertiesIn the study of adhesives and their applications, it isimportant to understand the concept of the glass transitiontemperature, T g As the temperature rises above the T g ,the adhesive becomes more rubber-like because bondsbetween polymer chains become weak and the polymerbecomes soft. Thus, knowledge of T g is essential in theselection of materials for various applications. The useof thermal characterization studies on thermosetting resinmaterials helps to determine the processing propertiesof the adhesives. Thermal analysis measures chemicalor physical changes as a function of temperature. Thesemeasurements allow access to processing and performanceinformation relating to adhesives and composites.Properties obtainable include gel points, glass transitiontemperatures, reaction rates and cure kinetics, effectsof individual or combinations of components, polymerstability and material life predictions.There are many thermal analysis techniques availablein the market but most frequently used are dynamicmechanical thermal analysis (DMTA), differentialscanning calorimetry (DSC), thermogravimetric analysis(TGA) and thermomechanical analysis (TMA). Muchinformation regarding thermal analysis and its applications as a function of temperature has been extensively used tostudy the cure kinetics of various thermosetting polymers(Montserrat 1993; Thiagarajan et al. most common technique for evaluating changes in T gand cure state of thermosetting polymers (Turi 1981).However, DSC does not provide information on structuralchanges at the molecular level. By contrast, the DMTAtechnique imposes a small oscillatory deformation whichgenerates viscoelastic materials properties such as: thestorage modulus E’; loss modulus E’ and the mechanical changes of the material’s structure during cure. The DMAtechnique involves in the measurement of storage and lossmodulus in shear, tension, compression or bending for arange of temperature and loading (frequency, amplitudes)conditions. The measurement of the loss modulus providesrelaxation temperatures (such as T g and sub-T g ). In1 Faculty of Civil Engineering, Universiti Teknologi MARA, 40450 Shah Alam, Selangor, Malaysia2 Institute of Tropical Forest Products, Universiti Putra Malaysia, 43400 Serdang, Selangor, Malaysia* Corresponding author (e-mail: zakiahah@hotmail.com)37