Preparation and Characterization of Soft Glass Using Sarawak Silica Sand as Starting Material for Craftware

Soft glass is one of the soda-lime-silicate (SLS) glass which is well-known in the craftware industry by lamp working technique . It is produced by melting the glass batch of local silica sand and certain chemicals. The SiO2 content of the silica sand is determined by wet chemical method and XRF analysis. The sand which meets the standard will be ground to the size of 150 μm and below, dry mixed with chemicals in proportions according to the formulation. Three series of soft glass containing different amount of silica sand (70-75%) and two different melting temperature were produced. The melting temperatures varied from 1450°C to 1500°C. The thermal behavior of the glass produced was investigated by differential thermal analysis. The thermal properties of the glass such as glass transition temperature, melting temperature and linear thermal expansion coefficient were studied. From the results, it was found that the melting temperature is around 600°C 750°C and this is consistent with the value theoretically. Other characterizations such as density, refractive index and Vickers micro hardness were also been carried out. Abstrak Kaca lembut termasuk di dalam kumpulan kaca soda-kapur-silika (SLS) yang terkenal dalam industri penghasilan kaca kraf yang menggunakan teknik lampworking. Ia dihasilkan dengan meleburkan kelompok kaca pasir silika dan bahan-bahan kimia tertentu. Kandungan SiO2 bagi pasir silika tempatan ini ditentukan oleh kaedah kimia secara basah dan analisis XRF. Pasir yang menepati piawai akan dikisar sehingga ke saiz di bawah 150 μm dan dicampur dengan bahan-bahan kimia berdasarkan formulasi yang telah ditetapkan. Tiga siri kaca lembut telah dihasilkan iaitu yang mengandungi jumlah pasir silika yang berbeza (70-75%) pada dua suhu lebur yang berbeza iaitu 1450°C ke 1500°C. Kelakuan terma kaca yang dihasilkan telah diselidiki oleh analisis pembezaan terma (DTA) . Daripada ujian ini, sifat-sifat terma kaca seperti suhu peralihan kaca, suhu pelembutan dan pekali pengembangan terma linear telah dikaji. Daripada hasil kajian, didapati bahawa suhu lebur bagi kaca ini ialah pada sekitar 600°C - 750°C dan ini adalah selari dengan nilai teori. Pencirian lain seperti ketumpatan, indeks biasan dan mikrokekerasan Vickers juga telah dilakukan.