Right from 16th Century, chemical research teams have used glass containers for a very basic reason; the glass container is transparent, almost invisible. And so the contents and the reaction are clearly visible. But because chemists must heat, cool and mix chemical substances, ordinary glass is not always adequate for laboratory work.
Laboratory work requires apparatus made in a glass – which can readily be moulded into any desired shape or form, which offers maximum inertness when in contact with the widest range of chemical substances, which can withstand thermal shock without fracture and high temperature work without deforming, and which will be resilient enough to survive the everyday knocks to which it will be subjected in normal laboratory handling, washing and sterilizing processes.
Borosilicate glass represents unmatched standardized glass for construction of plant and piping in the chemical, dyestuff, food pharmaceutical, petrochemical industries. Borosilicate glass is also very widely used for scientific applications. Made from low thermal expansion borosilicate glass its intrinsic qualities of resistance to physical and chemical attack and ability to stand thermal shock make it an ideal material of construction for scientific and laboratory apparatus, for industrial applications like syringe manufacture, gauge glasses, photo printing cylinders, petromax lantern chimneys, explosion-proof lighting covers and for fabrication of chemical process plant and piping.
Its steadily growing use is due to many advantages over conventional materials.
- Outstanding corrosion resistance
- Smooth pore free surface
- Transparency
- Catalytic inertness
- No effect on taste and odour
- Physiological inertness
Our borosilicate glass tubes represent optimum mechanical, thermal and chemical behaviour. This glass is used in laboratories as well as for industrial applications where maximum thermal resistance, thermal shock resistance, mechanical resistance as well as unusual chemical resistance are required.
Borosilicate glass tubing is drawn on fully automatic machines which permit close tolerances on dimensions. These also undergo careful and strict quality control. A large and comprehensive range of standard tubing in diameters from 4mm to 163mm and in light, medium and heavy wall is available ex-stock.
Gauging / Dimension Control:
Outside Diameter – When specified, all outer diameters at any point on a piece of tubing will be within the tolerances specified. These tolerances include out of round (ovality).
Inside Diameter – When specified, all inner diameters at each end of a piece will be within the tolerances specified. These tolerances include out of round.
Wall – All points at each end of a piece will be within the wall tolerances specified. Siding is included.
Lengths – All standard lengths will be within the tolerances specified.
Standard Lengths:
| Sizes up to 35mm O.D. | As machine cut | : 1500 ± 50 mm |
| Sizes above 35mm O.D. | Trim and cut | : 1226 ± 6 mm |
Technical Data
Chemical Composition
Borosilicate glass is chosen for its unique chemical and physical properties. Borosilicate glass can be considered as being composed of oxides. The chemical and physical properties of any glass depends to a varying degree on the chemical composition of the glass.
A low alkali borosilicate composition made to Code No. 7740. Its typical chemical composition is given alongside. It is virtually free of magnesia-lime-zinc group and contains only traces of heavy metals.
| % by weight | |
|---|---|
| SiO2 | 81 |
| B2O3 | 13 |
| Na20 | 4 |
| Al203 | 2 |
Thermal Properties
As the coefficient of thermal expansion of Borosilicate glass is low, the thermal stresses under a given temperature gradient are consequently low and the glass can withstand higher temperature gradients and also sudden temperature changes / thermal shocks. Minute scratching of glass surface can however reduce its thermal resistance.
| Coefficient of Linear Expansion | 32.5 x 10-7°C |
|---|---|
| Strain Point | 515°C |
| Annealing Point | 565°C |
| Softening Point | 820°C |
| Specific Heat | 0.2 |
| Thermal Conductivity (Cal/cm3/°C/sec) | 0.0027 |
In general “Strain point” should be regarded as the maximum safe operating temperature of borosilicate glasses. When heated above 500°C the glass may acquire permanent stresses on cooling.
All our glass tubes are annealed in modern Lehr ovens under strictly controlled conditions to ensure minimal residual stress in the products.
Chemical Durability
Our borosilicate glass tubes are highly resistant to water, neutral and acid solutions, concentrated acids and their mixtures as well as to chlorine, bromine, iodine and organic matters. Even during extended period of reaction and at temperatures above 100°C, its chemical resistance exceeds that of most metals and other materials. It can withstand repeated dry and wet sterilisation without surface deterioration and subsequent contamination.
Resistance to attack of various chemicals is shown below. Only hydrofluoric acid, very hot phosphoric acid and alkaline solutions increasingly attack the glass surface with rising concentration and temperature.
| Contact chemical | Duration in hr. | Loss in wt. (mg/m2) |
|---|---|---|
| Water distilled at 100°C | 6 | 10 |
| Water Vapour Steam at 121°C | 1 | 75 |
| Acid HCl | 6 | 100 |
| 80% H2SO4 at 130°C | 12 | 140 |
| Alkali- lN soln. of Na2CO3boiling | 6 | 4000 |
| Infusion Fluids Isotonic | ||
| NaCl (0.85%) 121°C | 2 ½ | 70 |
| Glucose (5%) 121°C | 2 ½ | 50 |
Optical Properties
Our borosilicate glass tubes show no noticeable absorption in the visible region of the spectrum. It appears consequently clear and colourless.
Fabricating
Due to low expansion of glass and easy workability, this glass can be shaped, formed, joined into complicated apparatus. It can be done even by an analyst in one’s own laboratory and kept on changing till one gets what one needs. In case where annealing in a controlled oven is difficult one can do so by flame annealing which is also a great advantage.