Question:
In injection blow molding of plastic beverage bottles, the blowing is accomplished by
In injection blow molding of plastic beverage bottles, the blowing is accomplished by
Show Hint
Plastic bottles are blown using heated, pressurized air because it expands uniformly and does not contaminate or cool the polymer during shaping.
Updated On: Jan 13, 2026
- hot water
- hot air
- hot oil
- alcohol
Show Solution
Verified By Collegedunia
The Correct Option is B
Solution and Explanation
Injection blow molding is one of the most widely used processes for producing high-quality, uniform plastic beverage bottles made of polymers such as PET (Polyethylene Terephthalate). The process consists of two main stages: injection molding of the preform and subsequent blowing of this preform to obtain the final bottle shape. In the blowing stage, it is essential to uniformly stretch the preform while it is still in a rubbery or softened condition. To achieve this, a pressurized medium must be supplied inside the hollow preform. The ideal medium must be capable of providing rapid expansion, clean operation, and precise pressure control without contaminating the plastic.
Hot air is used because it is clean, inexpensive, easily compressible, and capable of maintaining the preform at a suitable temperature during expansion. The temperature of the air prevents premature cooling and brittleness, ensuring uniform wall thickness and excellent clarity of the final product. Water or oil would interfere with the thermal balance and could cause uneven temperature distribution, poor surface finish, or contamination. Alcohol presents safety hazards due to flammability and volatility. Therefore, hot air is universally used as the blowing medium in injection blow molding.
Hot air is used because it is clean, inexpensive, easily compressible, and capable of maintaining the preform at a suitable temperature during expansion. The temperature of the air prevents premature cooling and brittleness, ensuring uniform wall thickness and excellent clarity of the final product. Water or oil would interfere with the thermal balance and could cause uneven temperature distribution, poor surface finish, or contamination. Alcohol presents safety hazards due to flammability and volatility. Therefore, hot air is universally used as the blowing medium in injection blow molding.
Was this answer helpful?
0
0
Top GATE PI Manufacturing Processes I Questions
- Mild steel plates are welded to make butt joints by arc welding with 85% heat transfer efficiency ignoring other losses. The first weld joint is made by selecting arc voltage of 30 V and current of 180 A with a welding speed of 6 mm/s. Using identical plates, a second weld joint is made with the same arc voltage and a welding speed of 8 mm/s. If both the welds have the same heat input, then the welding current (in A) for the second weld joint is _____. (Answer in integer)
- In a single pass cold rolling operation, a flat plate is reduced to a thickness of 3 mm. In this operation, two rolls of diameter 400 mm each are rotating in opposite direction at 300 RPM, and the elastic deflection of these rolls is negligible. The angle of bite is 10°. If the neutral point is present at an angle of 7° from the exit side, then the thickness of the plate (in mm) at the neutral point is _____ . (Rounded off to 1 decimal place)
- A blank of 100 mm diameter is to be cut out of a 2 mm thick sheet through blanking operation. If the radial clearance between the punch and die is 6% of the sheet thickness then the diameter (in mm) of the punch is _____ . (Rounded off to 2 decimal places)
- For polymers, match each process with the most suitable application listed.
Process Application P Extrusion 1 Producing complex parts with close tolerance Q Injection molding 2 Producing thermosetting plastic components R Blow molding 3 Producing long uniform sections S Compression molding 4 Producing hollow shapes - Which one of the following casting defects is caused due to the supply of the molten metal through two gates?
View More Questions
Top GATE PI Questions
- In an air-standard Otto cycle, the pressure and temperature of air just before the compression stroke are 200 kPa and 26.85 °C, respectively. The combustion process is assumed to be a constant volume process, where 1.02 MJ/kg heat is added. The cycle efficiency is 50%. The adiabatic index \(γ\) and specific heat at constant volume \(C_v\) can be considered to be constant during the process (corresponding values taken at the mean cycle temperature).
Assuming that the ideal gas law is applicable, \(γ = \frac 43\) and \(c_v= 0.85\ kJ/kg-K\), the maximum pressure (in MPa) reached during the cycle is _____ . (Rounded off to 1 decimal place) - A metallic cylindrical pressure vessel, used to store compressed air in a plant, has 1 m mean radius and 4 mm wall thickness. The maximum allowable normal and shear stresses in the cylindrical portion of the vessel are 100 MPa and 40 MPa, respectively. Considering only these data in the design, the maximum allowable internal gauge pressure (in MPa) of the compressed air is ______ . (Rounded off to 2 decimal places)
- A flat belt drive with pulley of r = 20 cm radius is designed to transmit 6.283 kW power at 600 RPM. In the figure, τ is the corresponding torque. If the coefficient of static friction between the belt and the pulley is 0.3, then the minimum value of the tightening force F (in kN) required to prevent the belt slip is _____ . (Rounded off 2 decimal places)
- Mild steel plates are welded to make butt joints by arc welding with 85% heat transfer efficiency ignoring other losses. The first weld joint is made by selecting arc voltage of 30 V and current of 180 A with a welding speed of 6 mm/s. Using identical plates, a second weld joint is made with the same arc voltage and a welding speed of 8 mm/s. If both the welds have the same heat input, then the welding current (in A) for the second weld joint is _____. (Answer in integer)
- In a single pass cold rolling operation, a flat plate is reduced to a thickness of 3 mm. In this operation, two rolls of diameter 400 mm each are rotating in opposite direction at 300 RPM, and the elastic deflection of these rolls is negligible. The angle of bite is 10°. If the neutral point is present at an angle of 7° from the exit side, then the thickness of the plate (in mm) at the neutral point is _____ . (Rounded off to 1 decimal place)
View More Questions