20+ MetLife Interview Questions and Answers

Optimizing zonal phases of injection nozzle parameters for different polymers to ensure consistent mold quality.

• Understand the specific requirements of each polymer in terms of temperature, pressure, screw speed, etc.

• Adjust the zonal phases accordingly to meet the optimal processing conditions for each polymer.

• Monitor the mold surface for any signs of bubble formation, excess flash, uneven surface, or polymer residues.

• Make necessary adjustments to the parameters to eliminate ...read more

Operating a melt flow indexer involves setting the temperature, loading the sample, and recording the melt flow index.

• Set the temperature of the indexer according to the polymer being tested

• Load the sample into the indexer and allow it to melt

• Measure the melt flow index by recording the time it takes for the polymer to flow through the die

• Some melt flow index parameters for polymers: PVC - 100-450 g/10 min, PP - 0.3-50 g/10 min, PE - 0.1-50 g/10 min

Operating a benchtop spectrophotometer involves understanding its principle, calibrating with known standards, and comparing color characteristics of polymers.

• Understand the principle of spectrophotometry - measures the intensity of light at different wavelengths

• Calibrate the spectrophotometer using known standards to ensure accurate readings

• Prepare samples of the specific polymer and the known standard for comparison

• Measure the color characteristics of both samples using the...read more

To operate a bunsen burner in a flammability cabinet for checking flame retardants in polymers, follow safety protocols, adjust the flame, place the sample in the cabinet, observe the flame behavior, and record results.

• Ensure proper safety measures are in place before operating the bunsen burner.

• Adjust the air and gas flow to create a blue flame with a well-defined cone.

• Place the polymer sample in the flammability cabinet and ignite it using the bunsen burner.

• Observe the flam...read more

Cleaning and purging the injection molding machine before test molding a different polymer material is important to prevent contamination and ensure product quality.

• Prevents contamination of the new polymer material with remnants of the previous material

• Ensures consistent product quality by removing any residue or impurities from the machine

• Helps prevent defects in the final product caused by mixing different materials

• Avoids potential equipment damage or malfunctions due to i...read more

Lubricant is used in injection molding machines to reduce friction, prevent wear and tear, and improve overall machine performance.

• Lubricants such as silicone oil, mineral oil, and grease are commonly used in injection molding machines.

• Proper lubrication should be done at regular intervals to ensure smooth operation and prevent breakdowns.

• Over-lubrication should be avoided as it can lead to contamination of the molded parts.

• Examples of proper lubrication times include before ...read more

Vulcanisation of rubber is a chemical process that involves adding sulfur to raw rubber to improve its strength, elasticity, and durability.

• Raw rubber is heated with sulfur in the presence of an accelerator, typically zinc oxide, to initiate the vulcanisation process.

• The mixture is then heated to a specific temperature for a certain amount of time to allow the sulfur to cross-link with the rubber polymer chains.

• This cross-linking creates a three-dimensional network within the...read more

Polymerisation process of synthetic polymers involves the linking of monomer units to form long chains or networks.

• Synthetic polymers are created through a chemical reaction called polymerisation.

• Monomer units, which are small molecules, are linked together to form long chains or networks.

• Polymerisation can be initiated by heat, light, or a catalyst.

• Examples of synthetic polymers include polyethylene, polypropylene, and polystyrene.

Some branches of organic chemistry related to the polymer industry include polymer chemistry, polymer physics, and polymer engineering.

• Polymer chemistry focuses on the synthesis and study of polymer structures.

• Polymer physics deals with the physical properties and behavior of polymers.

• Polymer engineering involves the design and processing of polymers for specific applications.

Instruments commonly used for quality control in the polymer industry include spectrophotometers, rheometers, and thermal analyzers.

• Spectrophotometers are used to measure the color and transparency of polymers.

• Rheometers are used to measure the flow and deformation behavior of polymers.

• Thermal analyzers are used to study the thermal properties of polymers, such as melting point and glass transition temperature.

A tensile testing machine measures the strength of a material by applying a pulling force until it breaks.

• Calibrate the machine before testing to ensure accurate results

• Secure the material in the grips of the machine

• Apply a gradually increasing force until the material breaks

• Record the maximum force applied before failure

• Calculate the tensile strength by dividing the maximum force by the cross-sectional area of the material

An impact testing machine is operated by placing the specimen between the anvils and releasing a pendulum to strike the specimen, measuring the energy absorbed.

• Place the specimen between the anvils of the machine.

• Release the pendulum to strike the specimen.

• Measure the energy absorbed by the specimen during impact.

• The principle of impact testing is to determine the ability of a material to absorb energy during fracture.

• Common types of impact testing machines include Charpy and...read more

Operating a melting point apparatus involves setting up the sample, heating it gradually, and recording the temperature at which the sample melts.

• Set up the melting point apparatus according to the manufacturer's instructions.

• Place a small amount of the sample in a capillary tube and insert it into the apparatus.

• Gradually heat the sample while observing it through a magnifying lens.

• Record the temperature at which the sample begins to melt and the temperature range over which ...read more

To operate a notch cutter, vernier caliper, and micrometer, one must have knowledge of their functions and proper handling techniques.

• To operate a notch cutter, ensure the material is securely clamped and align the cutting edge with the desired notch location before cutting.

• When using a vernier caliper, gently close the jaws around the object being measured and read the measurement from the scale, taking care not to apply excessive force.

• To operate a micrometer, place the obj...read more

Operating an injection molding machine involves setting up the machine, loading the material, adjusting parameters, and monitoring the process.

• Set up the injection molding machine by connecting it to power and ensuring all safety measures are in place.

• Load the material (such as plastic pellets) into the machine's hopper.

• Adjust parameters like temperature, pressure, and injection speed based on the material being used and the desired outcome.

• Start the machine and monitor the i...read more

Instruments used in quality control for polymers are calibrated using standardized procedures to ensure accuracy and reliability.

• Calibration involves comparing the measurements of an instrument to known standards.

• Adjustments are made to the instrument to minimize any discrepancies between the instrument's readings and the known standards.

• Calibration certificates are often provided by external calibration labs to verify the accuracy of the instrument.

• Regular calibration schedu...read more

A glow-wire test apparatus is operated by heating a wire to a specified temperature and then applying it to the test sample to assess its flammability.

• Turn on the glow-wire test apparatus and set the temperature to the specified level.

• Place the test sample under the glow-wire.

• Bring the heated wire in contact with the test sample for a specified duration.

• Observe the sample's reaction to the heat and record the results.

• The principle of the glow-wire test is to simulate the effe...read more

Ash content can be checked using a muffle furnace and silica crucible by heating the sample to burn off organic material and weighing the residue.

• Weigh the clean and dry crucible before adding the sample.

• Place the sample in the crucible and heat it in the muffle furnace to burn off organic material.

• Cool the crucible in a desiccator before weighing the residue to determine the ash content.

• The principle is based on the fact that organic material combusts at high temperatures, l...read more

Young's modulus is a measure of stiffness of a material, while secant modulus is a measure of the material's response to stress. They are used to check the durability of polymers.

• Young's modulus is a measure of the stiffness of a material and is defined as the ratio of stress to strain within the elastic limit.

• Secant modulus is a measure of the material's response to stress and is calculated by drawing a line from the origin to a specific point on the stress-strain curve.

• Youn...read more

Chain initiation, propagation, transfer, and termination are key steps in polymerization reactions.

• Chain initiation involves the formation of reactive species that can start the polymerization process.

• Chain propagation is the repeated addition of monomers to the growing polymer chain.

• Chain transfer involves the transfer of a growing polymer chain to another molecule, affecting the chain length.

• Chain termination occurs when the polymer chain stops growing, usually due to the c...read more

Initiator chemicals used for polymerisation include organic peroxides, azo compounds, and photoinitiators.

• Organic peroxides are commonly used as initiators in polymerisation reactions.

• Azo compounds are another type of initiator chemical used in polymerisation.

• Photoinitiators are used in photopolymerisation processes to initiate polymerisation upon exposure to light.

A moisture analyser is operated by placing a sample in the chamber, setting the parameters, and allowing the instrument to measure the moisture content based on the principle of loss on drying.

• Place a sample of the material to be tested in the chamber of the moisture analyser.

• Set the parameters such as temperature and time for the drying process.

• Start the analyser to heat the sample and measure the weight loss as the moisture evaporates.

• The principle of operation is based on ...read more

A viscometer is operated by filling the sample into the instrument, setting the desired parameters, and measuring the viscosity based on the principle of fluid flow resistance.

• Ensure the viscometer is clean and calibrated before use.

• Fill the sample into the viscometer according to the manufacturer's instructions.

• Set the desired parameters such as temperature and speed of rotation.

• Initiate the measurement and record the viscosity value displayed on the instrument.

• Clean the vis...read more

A notch cutter is required before impact testing to create a standardized defect in the specimen, which helps in determining the material's toughness and resistance to fracture.

• Notch cutter creates a standardized defect in the specimen

• The presence of a notch helps in determining the material's toughness and resistance to fracture

• Without a notch, the impact test results may not accurately reflect the material's behavior under stress