STUDYING THE EFFECT OF DIFFERENT ADDITIVES ON THE THERMAL CONDUCTIVITY AND MECHANICAL CHARACTERISTICS OF EPOXY-BASED COMPOSITE MATERIALS

The current paper deals with investigating the effect of two different fillers on the thermal and mechanical characteristics of epoxy-based composite. The filler used throughout the study are: charcoal and Pyrex, both of them are different in nature and have not been investigated thoroughly or even compared fairly in terms of their effect on polymer matrix. Further, they can be considered as a cheap filler, charcoal can be obtained from a simple pyrolysis process of plants (charcoal) and Pyrex waste can be collected easily. Both types are added to the selected matrix with volume percent ranged from 10 to 60 with increments of 10. To ensure a fair comparison, the particle size is fixed (is about 1.7 micrometer). The results showed that the epoxy thermal conductivity has enhanced by about two orders of magnitudes over the studied range of filler. In terms of mechanical properties, the charcoal improves the tensile strength about 84% at 60% volume fraction while the Pyrex effect is about 40% at the same filler level. On the contrast, the results of compressive strength do not show an appreciable improvement overall. It decreases by about 12% at 60% volume fraction of charcoal while increases about the same percent with Pyrex at the same filler level.

Common Perceptions about the Use of Fillers in Silicone Rubber Insulation Housing Composites

This paper discusses the lessons learned about fillers that are added to silicone rubber insulation housing composites, in order to improve the erosion resistance against the dry-band arcing are presented and common perceptions. Common practices that employ alumina tri-hydrate are reviewed, including the additional influential effect of the water of hydration in the suppression of the dry-band arcing. The effect of the water of hydration is shown to be dependent on various factors, such as the hydrated filler level and the type of the hydrated filler. More recent paradigms in which hydrated fillers have not been employed are also reviewed. Volume and shield actions of fillers are essential aspects that need to be understood in the design of silicone rubber insulation housing composites for new applications such as HVDC. In addition, the thermal degradation mechanisms of silicone rubber and the corresponding suppression effects of the added fillers are summarized.

KAJIAN PARAMETER MARSHALL DENGAN MENGGUNAKAN LIMBAH SERBUK KERANG HIJAU SEBAGAI FILLER CAMPURAN LAPIS ASPAL BETON

This inquiry aims to investigate whether the use of green mussels shell powder as an alternate filler in Laston mix can meet the Marshall parameter or not. Method used in this inquiry is experimental method that examines Marshall parameter at various percentages of green mussels shell powder use in which their level are 0%, 6,5%, 7,5%, and 8,5% as an alternate of half of filler. The experiment of green mussels shell powder is generate a maximum level of filler at 7,5% percentage with stability value in 987,478 kgs, flow value in 3,70 mm, Marshall Quotient value in 266,738 kgs/mm, Void in Mineral Aggregates value in 17,597%, Void Filled with Bitumen value in 71,958% and Void In the Mix value in 4,709%. By this result, it can be concluded that green mussels shell powder can be used as an alternate filler in AC-WC asphalt mix for heavy traffic road with 7,5% percentage of filler level.

Silver Nanoparticles in Dental Biomaterials

Silver has been used in medicine for centuries because of its antimicrobial properties. More recently, silver nanoparticles have been synthesized and incorporated into several biomaterials, since their small size provides great antimicrobial effect, at low filler level. Hence, these nanoparticles have been applied in dentistry, in order to prevent or reduce biofilm formation over dental materials surfaces. This review aims to discuss the current progress in this field, highlighting aspects regarding silver nanoparticles incorporation, such as antimicrobial potential, mechanical properties, cytotoxicity, and long-term effectiveness. We also emphasize the need for more studies to determine the optimal concentration of silver nanoparticle and its release over time.

The contribution of pulp brightness and optical brightening agents to paper whiteness

The desired optical properties of a paper can be achieved through a variety of tools: pulp brightness, optical brightening agents, dyes, or fillers. In this work, we explore the interaction between pulp brightness levels and optical brightening agents (OBA) addition on paper whiteness. Conditions were chosen that approximate an uncoated freesheet grade. Papers were prepared using eucalyptus kraft pulps bleached to three different brightness levels. A constant filler level and optimized retention chemistry were used in the preparation. The addition of OBA was evaluated as a wet end only application and as a wet end/size press application. Dye addition was not a part of this evaluation. We also surveyed the optical properties of a range of commercially available uncoated freesheet paper. We found that the initial brightness of the pulp furnish sets the limit for whiteness level achievable with OBA during papermaking. It is not possible to compensate for low initial pulp brightness (<85.4% ISO) by the addition of OBA when aiming for CIE D65 whiteness above 135. We also evaluated the economics of pulp brightness and OBA addition to show how these two variables can be balanced. Based on the conditions used in this study, it is most cost effective to use pulp having 90% ISO brightness or higher when targeting CIE D65 whiteness above 135.

Effects of Calcium Phosphate Nanoparticles on Ca-PO4 Composite

Nano-particles of dicalcium phosphate anhydrous (DCPA) were synthesized for the first time. The objectives of this study were to incorporate DCPA nano-particles into resin for Ca-PO4 release to combat dental caries, and to investigate the filler level effects. Nano-DCPA and nano-silica-fused silicon nitride whiskers at a 1:1 ratio were used at filler mass fractions of 0–75%. The flexural strengths in MPa (mean ± SD; n = 6) of DCPA-whisker composites ranged from (106 ± 39) at 0% fillers to (114 ± 23) at 75% fillers, similar to (112 ± 22) of a non-releasing composite (TPH) (p > 0.1). The composite with 75% fillers in a NaCl solution (133 mmol/L, pH = 7.4, 37°C) yielded a Ca concentration of (0.65 ± 0.02) mmol/L and PO4 of (2.29 ± 0.07) mmol/L. Relationships were established between ion-release and DCPA volume fraction VDCPA: Ca = 4.46 VDCPA1.6, and = 66.9 VDCPA2.6. Nano-DCPA-whisker PO4 composites had high strength and released high levels of Ca-PO4 requisite for remineralization. These new nano-composites could provide the needed combination of stress-bearing and caries-inhibiting capabilities.