UCTEA Chamber of Metallurgical & Materials Engineers Proceedings Book

86 IMMC 2016 | 18th International Metallurgy & Materials Congress

Fabrication of Alumina-Epoxy Interpenetrating Network Composites

Okan Bilgiç, Yasin Altın, Ayse Bedeloğlu, Onur Saray, Ayşe Kalemtaş

Bursa Technical University - Türkiye

Abstract

In this study, macroporous alumina ceramics containing interconnected porosity were prepared by a simple and economical technique, polymeric sponge technique. Commercial polyurethane sponges with 10 pores per inch were used to prepare porous alumina ceramics. Then ceramic-epoxy composites were fabricated by infiltrating epoxy resin into the highly porous alumina substrates under vacuum conditions to eliminate air bubbles during the processing step. Scanning electron microscopy investigations of the produced composites revealed that there is a good bonding between the ceramic and epoxy materials. It was also determined that dense and macroscopically homogenous ceramic-polymer interpenetrating network composites were produced. I. Introduction

Composites materials are used in increasing quantities in various fields of industry such as automotive [1], defence [2, 3], transportation [4], aviation [5], marine [6], health [7, 8] and communication [9, 10]. Interpenetrating network composites is a subgroup of composites materials and in recent years there is a significant increase in research activity and publications in this area. Interpenetrating network composites that have a 3D interpenetrating microstructure have drawn a significant attention [11-15] due to achieved enhanced properties when compared with the particle reinforced counterparts. It was experimentally shown that interpenetrating network composites has enhanced elastic properties when compared with discontinuously reinforced composites. [16-18] Interpenetrating network composites has more homogenous structure and as a result they have promising properties when

compared with particle reinforced traditional ceramic composites. There are various fabrication methods for the interpenetrating network composite structures. One of the most common method is to impregnate a desired second phase into a preexisting open-cell porous substrate material. The goal of the current work was to produce alumina-epoxy interpenetrating network composites by using a simple and economical approach. Firstly, highly porous alumina ceramics with a network structure was produced via polymeric sponge method. Then, epoxy resin was infiltrated into these ceramics which was containing interconnected porosity to produce interpenetrating network ceramic-polymer composites. Alumina ceramics and epoxy both have a very wide application area as a monolithic material or a member of a composite structure. Alumina ceramics have a widespread use in industry due to good mechanical properties, such as high hardness, an ability to work at high temperatures and high resistance to thermal shock, excellent wear and chemical resistance. Epoxy polymers have a wide engineering and structural applications such as plastic-tool industries, electrical and electronic industries, transportation, communications, construction, commercial and military aircrafts industries due to its low density, outstanding mechanical properties, excellent dimensional, thermal and environmental stabilities, good electrical insulation, low shrinkage rate, easy process ability, and economical processing capabilities.

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8718. Uluslararas ı Metalurj i ve Malzeme Kongresi | IMMC 2016

2. Experimental Procedure In this study, commercial alumina powder was used as the major ceramic material and low amount of bentonite was used to adjust rheological properties of the ceramic slurry. Also some rheological additives such as dispersant, thickening agent and binder were used to achieve desired solid loading and improve rheology of the slurry, respectively. Commercial polymeric sponges (10 ppi) were used as templates to produce porous alumina substrates for the fabrication of interpenetrating ceramic-polymer composites.

Thermogravimetry (TG) and differential thermal analysis (DTA) of the polymeric sponge was carried out by using a simultaneous TG/DTA analyzer (NETZSCH STA 449F3) in air atmosphere to determine heating regime of binder burn-out process. Applied heating rate during TG-DTA was 10 C/min. It was determined that pyrolysis of the polymeric sponge was completed at

650 C (Fig. 1).

Figure 1. TG/DTA curves of the polymeric sponge. Alumina slurry preparation was performed in deionized water by using a planetary ball mill. Polymeric sponges were immersed into the ceramic slurry and compressed to provide coating of the sponge walls with alumina suspension. Then, the sponges were removed from the slurry. The sponge immersion process was repeated for a few times to achieve desired ceramic coating thickness. Prepared samples were initially dried at room temperature for two days. Dried samples were slowly (1 C/min) heated up to 650 C and a 60 min dwell time was applied to burn out the polymeric sponge and other organic additives used during the slurry preparation step before sintering. Subsequently, the samples were heated to the sintering temperature (1600 C) at a rate of 3 C/min with a 1 hour dwell time. Alumina-epoxy composites were fabricated by infiltrating epoxy resin into the highly porous ceramic substrates under vacuum conditions to eliminate air bubbles during the processing step. Microstructures of the fabricated interpenetrating network composite samples were investigated with

a scanning electron microscope (SEM, Zeiss Supra 50 VP) in secondary electron image mode (SEI). 3. Results and Discussion A representative photo of the porous alumina ceramic substrate taken by digital camera is given in Fig. 1. As clearly visible from the macroscopic photograph of the sample pores are interconnected and structure is highly porous.

Figure 1. Macroscopical picture of the fabricated porous alumina substrate.

UCTEA Chamber of Metallurgical & Materials Engineers Proceedings Book

88 IMMC 2016 | 18th International Metallurgy & Materials Congress

Scanning electron microscopy investigation of the fracture surfaces of the produced porous alumina samples confirmed that these samples are containing interconnected porosity and the structure is highly porous. (Fig. 2)

Figure 2. SEM micrographs of fractured porous alumina samples at different magnifications. Fracture surface investigations of the produced alumina-epoxy interpenetrating network composite samples via scanning electron microscopy investigation revealed that the composites are dense, microstructure is homogenous and there is good bonding between alumina ceramic and epoxy. (Fig. 3)

Figure 3. SEM micrographs of fractured alumina-epoxy interpenetrating network composite samples at different magnifications. 4. Conclusion In the current study, dense and macroscopically homogenous alumina-epoxy interpenetrating network composites were produced via a cost effective and readily applicable fabrication technique. Microstructural investigations of the fabricated ceramic-polymer interpenetrating network composites also revealed that there is a good bonding between the components of the structure, alumina and epoxy. This study represents

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8918. Uluslararas ı Metalurj i ve Malzeme Kongresi | IMMC 2016

initial results of an ongoing project and mechanical properties of the produced porous ceramics and alumina-epoxy interpenetrating network composites will be investigated. References

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