Recycled Polyethylene Terephthalate Moisture Testing Methods
Accurate moisture testing below 50 ppm via Karl Fischer oven titration prevents hydrolytic intrinsic viscosity degradation in recycled PET during melt processing.
Manometric Testing
Meaning
Measurement of gas transmission through a polymer barrier by tracking pressure changes in a closed chamber over time provides a standard method for assessing the barrier performance of films. Utilizing manometric testing allows packaging engineers to evaluate the transmission rates of oxygen and carbon dioxide. This technique is critical for validating films used in modified atmosphere food packaging.
Pressure Measurement
High-sensitivity pressure transducers record the rise in pressure on the lower-pressure side of the test cell as gas molecules permeate through the polymer. This method requires a high vacuum on both sides of the sample before the test starts to ensure accuracy.
Permeability Calculation
Mathematical equations convert the rate of pressure change into a gas transmission rate under standard conditions of temperature and pressure. The calculation must account for the thickness of the film and the surface area exposed to the gas.
Film Barrier
Evaluation of different polymer structures shows how crystalline orientation and polymer blending improve the gas barrier of the material. Multi-layer coextruded films often combine high-density polyethylene for moisture resistance with ethylene vinyl alcohol for gas barrier performance, and this testing method provides the quantitative data needed to optimize each layer thickness to meet the required shelf life of the packaged product.