Quality control for packaging

The efficiency of many packaging processes, like flow wrapping with flexible packaging or stacking/filling rigid, thermoformed or injection moulded packaging can be influenced by many parameters. Foremost amongst these is the molecular architecture of the polymer(s) used in the packaging material. This may be even more critical for recycled or reprocessed materials.

The molecular architecture dictates the flow behaviour (rheology) of the polymer and may be measured through the rheological parameters of the polymeric material. They impact on the film-forming, mould-filling and thermoforming (possibility of thin spots) capability of a polymer, as well as many other flow-dependent processes. The flow properties of materials may be tested in the laboratory, using high-temperature rheometry.

The processing and packaging performance of the polymeric packaging materials may be tested on a laboratory scale using instrumented laboratory extruders, with small-scale, post-ex assets (like small-scale cast film dies, blown-film towers or injection moulders) for example. In this way, properly graded packaging base ingredients can be released for blending and processing. Pre- and post-processing quality assurance/fault tracing is facilitated. Some laboratory extruders may also be fitted with rheology dies, to measure rheological parameters as well as service the scaled-down, post-ex plant.

Even with a rheologically well-defined base material, random impurities can enter the production process and compromise the quality of the final product - by causing blemishes, holes and irregularities. This is particularly important for metalised, light-coloured or small-gauge packaging.

During the manufacture of flexible or rigid packaging, optical methods can prove invaluable for improving the final quality of these packaging materials. At the source (the polymer resin), optical scanning techniques can detect, qualify and quantify impurities such as black spots, before the resin is processed. Post-ex, scanning techniques can detect, quantify, and qualify impurities (eg, holes, fish eyes) and therefore accurately grade product. This is a good indicator of the likelihood of failures such as tearing during flow-wrapping, holes or weak spots during thermoforming and sealing, visible imperfections for moulded components during packaging operations later.