Effects of filler shape and size on the properties of silver filled epoxy composite for electronic applications

Epoxy composites filled with nano- and micro-sized silver (Ag) particulate fillers were prepared and characterized based on flexural properties, coefficient of thermal expansion, dynamic mechanical analysis, electrical conductivity, and morphological properties. The influences of these two types of Ag fillers, especially in terms of their sizes and shapes, were investigated. Silver nanoparticles were nano-sized and spherical, while silver flakes were micron-sized and flaky. It was found that the flexural strength of the epoxy composite filled with silver flakes decreased, while the flexural strength of the epoxy composite filled with silver nanoparticles showed an optimum value at 4 vol.% before it subsequently dropped. Both silver composites showed improvement in flexural modulus with increasing filler loads. CTE value indicated significant decrements in filled samples compared to neat epoxy. Results on the electrical conductivity of both systems showed a transition from insulation to conduction at 6 vol.%.     

Study on Tensile,Electrical, and Thermal Properties of Aluminium Particle Filled Natural Rubber (NR) and Ethylene-Propylene-Diene Terpolymer (EPDM) Composites

Comparative studies on the effect of aluminium particles in natural rubber (NR) and ethylene-propylene-diene terpolymer (EPDM) were conducted. The incorporation of aluminium particles in NR or EPDM composites increased the cure time, t ₉₀, and scorch time, t _S2 . At a fixed filler loading, EPDM composites exhibited longer t ₉₀ and t _S2 than NR composites. The results also indicate that the maximum torque, M _H of aluminium filled NR and EPDM composites increase with increasing filler loading. For tensile properties, EPDM composites show lower tensile properties than NR composites. Thermogravimetric analysis (TGA) results show that aluminium filled EPDM composites have better thermal stability than aluminium filled NR composites.

The results for electrical properties indicate that the electrical properties of aluminium filled NR and EPDM composites increase with increase in filler loading.     

Effects of Natural Weathering on Properties of Recycled Newspaper-filled Polypropylene (PP)/Natural Rubber (NR) Composites

Natural weathering has been applied to investigate the properties of recycled newspaper (RNP)-filled polypropylene (PP)/natural rubber (NR) composites. Three sizes of RNP (11 mm, 23 mm, and 53 mm) were used in this study. These composites were subjected to natural weathering conditions; i.e, tropical climate in Penang, Malaysia, for 3 and 6 months. Different techniques including mechanical tests, Fourier transform infrared spectrometry (FTIR), differential scanning calorimetry (DSC), and scanning electron microscopy (SEM) were used in order to obtain a comprehensive view of degradation occurring during the natural weathering of the composites. Results of mechanical tests show that an increasing content of RNP in composites decreased the tensile strength and elongation at break (EB), while increasing the Young's modulus after exposure of 3 and 6 months. Scanning electron microscopy on surfaces after weathering shows that the filler was poorly wetted by the matrix. This explains the reduction in tensile strength and elongation at break after weathering. The Fourier transform infrared spectrometry results on the composites after exposure to natural weathering indicate the presence of carbonyl, vinyl, and hydroxyl groups, which formed from various chemical reactions taking place during weathering.     

Characterization of microstructure and mechanical properties of biodegradable polymer blends of poly(L‐lactic acid) and poly(butylene succinate‐co‐ε‐caprolactone) with lysine triisocyanate

Effect of lysine triisocyanate (LTI) as an additive on the microstructure and the mechanical properties of biodegradable polymer blends of poly(L ‐lactic acid) (PLLA) and poly(butylene succinate‐co‐ε‐caprolactone) (PBSC) were investigated by using Fourier transform infrared (FTIR) spectroscopy, differential scanning calorimetry (DSC), field‐emission scanning electron microscope (FE‐SEM), and bending and mode I fracture testing techniques. It was found that the addition of LTI dramatically improves the phase‐separation morphology of the PLLA/PBSC blends. FTIR analysis suggested that the NCO groups of LTI were acted as compatibilizer by attributing secondary process between the two polymers PLLA and PBSC, resulting lower peak intensity of ACI samples, understood as secondary process is polar interaction and hydrophobic process. DSC and FE‐SEM results also supported such improvement of immiscibility between PLLA and PBSC. Macroscopic mechanical properties such as the bending fracture energy and the mode I fracture properties are also effectively improved by the LTI addition. Void formation is suppressed due to such morphological change in PLLA/PBSC/LTI blends, and, as a result, energy dissipation in the notch‐tip region of the blends becomes higher than in that of PLLA/PBSC where localized stress concentration due to voids tends to accelerate fracture initiation and, therefore, lowers the fracture energy. POLYM. ENG. SCI., 2010. © 2010 Society of Plastics Engineers     

Flexibility improvement of epoxy nanocomposites thin films using various flexibilizing additives

Epoxy thin films have attracted substantial research attention in the electronic industry because of their excellent thermo-mechanical properties, ease of processing, chemical resistance capability combined with superior electrical insulation, and favorable economics. However, the major drawback of epoxy systems comes from their brittleness, which causes poor resistance to crack, low impact strength, and low toughness. The present paper reports on the effects of the addition of different types of flexibilizers; flezibilizing resin (FR-1), polyol resin (FR-2), and toughening resin (FR-3), and synthetic diamond (SD) nanofillers, on the mechanical, thermo-mechanical, and thermal stability properties of epoxy nanocomposite thin films. The addition of flexibilizing additives into the epoxy matrix results in a major enhancement in flexibility as identified by the improvement in elongation at break. FR-1 and FR-3, which contain silicone elastomers, cause less severe degradation on the tensile modulus and strength compared with FR-2. The addition of SD helps increase the stiffness of epoxy nanocomposite thin films and improves their thermal stability but decreases their flexibility.     

Polypropylene/natural rubber composites filled with recycled newspaper: Effect of chemical treatment using maleic anhydride‐grafted polypropylene and 3‐aminopropyltriethoxysilane

A study on effect of chemical treatment using maleic anhydride‐grafted polypropylene (MAPP) and 3‐aminopropyltiethoxysilane (3‐APE) was investigated. The performance of the MAPP and 3‐APE were investigated by means of torque development, mechanical properties, thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), scanning electron microscopy morphology, and water absorption. The results revealed that the use of MAPP or 3‐APE in the composites has increased the stabilization torque, tensile strength, Young's modulus, water absorption, and thermal stability of the PP/NR composites. The incorporation of MAPP in the composites shows higher stabilization torque, tensile strength, E_B, Young's modulus, and lower water uptake when compared with the use of 3‐APE in the PP/NR composites. TGA and DSC results indicated that primary and secondary peak of DTG curve, initial degradation temperature (T₀), degradation temperature (T_deg), melting temperature (T_m), heat of fusion of composites (ΔH_f(com)), crystallinity of composites (X_PP), and PP (X_PP) increased, while total weight loss and thermal degradation rate decreased for both treated composites. The MAPP‐treated RNP‐filled PP/NR composites were found to be more thermal resistance and more crystalline than 3‐APE‐treated filled PP/NR RNP composites. POLYM. COMPOS., 2012. © 2012 Society of Plastics Engineers     

Thermo‐physical,thermal degradation,and flexural properties of betel nut husk fiber reinforced vinyl ester composites

This study aims to investigate the thermo‐physical, mechanical, and thermal degradation properties of betel nut husk (BNH) fiber reinforced vinyl ester (VE) composites. These properties were evaluated as a function of fiber maturity, fiber content, and fiber orientation. Thermo‐physical properties were analyzed experimentally using a hot disk TPS method. The introduction of BNH was found to reduce the thermal conductivity of neat VE. The thermal conductivity and thermal diffusivity of BNH reinforced VE composites decreased with the increase in fiber content. Short fiber BNH reinforced VE composites showed the lowest thermal conductivity as compared to the unidirectional and random nonwoven composites. The TGA analysis shows lower resin transition peak for the BNH reinforced VE composites than the peak of neat VE. Fiber maturity had a notable effect on the flexural modulus of the BNH fiber reinforced VE composites. Incorporation of 10 wt% BNH fibers into the composite has increased the composites' flexural modulus by 46.37%. However, further increases in the fiber content reduced both flexural strength and modulus of the composites. POLYM. COMPOS., 37:2008–2017, 2016. © 2015 Society of Plastics Engineers     

Effect of intumescent ammonium polyphosphate (APP) and melamine cyanurate (MC) on the properties of epoxy/glass fiber composites

The effects of halogen-free flame retardants (FR) such as intumescent ammonium polyphosphate (APP) and melamine cyanurate (MC) on the flammability and mechanical properties of epoxy/glass fiber composite systems were studied. Overall, intumescent APP shows better flammability results compared with MC. The composite with 5 vol.% APP performed sufficiently well in the UL-94 test and LOI, whereas 20 vol.% MC is required to achieve similar results. The addition of 1 vol.% MC into 4 vol.% APP had shown some improvement on the composite flame resistance. The composite attains the maximum flexural strength at 15 vol.% while the dynamic mechanical analysis shows that the addition of flame retardants increased the storage modulus but did not change the glass transition temperature T_g.     

Properties of calcium copper titanate and barium titanate filled epoxy composites for electronic applications: effect of filler loading and hybrid fillers

Inorganic ceramics such as calcium copper titanate, CaCu₃Ti₄O₁₂ (CCTO) and barium titanate (BaTiO₃) were used as fillers to produce epoxy thin film composites for capacitor application. The effects of filler types and loading range on the dielectric, tensile, morphology, and thermal properties of the epoxy thin film composites were determined. Results showed that epoxy thin film composites with 20 vol% filler loading of CCTO and BaTiO₃ showed good dielectric properties, thermal stability, and thermal conductivity. However, the tensile properties of the CCTO/epoxy thin film composite was reduced as the filler loading increased. On the other hand, the tensile properties of BaTiO₃/epoxy thin film composite improved as the filler loading increased. Hybrid fillers CCTO and BaTiO₃ filled epoxy composites were fabricated and the effect of hybrid fillers on the dielectric properties and morphology of the epoxy thin film composites were investigated. Results indicated that positive hybrid effect in dielectric constant and dielectric loss showed by the hybrid composites.