Moisture absorption model of dry pharmaceutical packaging: experimental verification of HDPE bottles and LDPE bags

Research background and model construction: During consumer use of dry medicine, the packaging is repeatedly opened and single doses are taken out one by one. The moisture content inside the packaging will change over time and with the operation steps. In response to this scenario, researchers have developed a simple mathematical model to estimate the moisture content of dry pharmaceutical products with desiccants under usage conditions. The model is based on water mass balance, linking the permeation of packaging water vapor to the linear moisture absorption isotherm equilibrium between the packaging headspace, product, and desiccant. For static storage inside packaging, the model expresses moisture prediction using aggregated water vapor transmission parameters and linear moisture absorption isotherm parameters; For the process of sequentially extracting doses, an analytical solution is constructed by sequentially summing up the various steps of water vapor permeation and internal equilibrium in the packaging layer.

Experimental validation and key data

Two types of experimental packaging were used for validation: high-density polyethylene (HDPE) bottles and low-density polyethylene (LDPE) film bags, each containing 60 and 30 dry agent tablets, respectively, with 1 g of desiccant.

. The sample is stored at 25 ° C and 85% relative humidity, and the tablets are taken out in order every day. The moisture content predicted by the model is in good agreement with the experimental data, and the accuracy is acceptable. This result indicates that the model can describe the actual process of moisture redistribution between the packaging layer’s moisture permeability and the internal headspace, product, and desiccant.

Significance for the Packaging Materials and Additives Industry

Although this study focuses on pharmaceutical packaging, the HDPE bottles and LDPE film bags involved are widely used resin and container forms in food and daily chemical packaging. Moisture barrier and content stability are also core performance indicators for packaging material design.

. For the packaging materials industry, this model provides a quantifiable design approach: by adjusting the moisture permeability parameters and desiccant dosage of the packaging layer to match the moisture control requirements within the target service life. At the material formulation and processing level, the moisture permeability of HDPE and LDPE is affected by the resin structure, processing conditions, and additive system. When designing packaging, it is necessary to consider both the material barrier properties and the moisture absorption characteristics of the contents. For packaging systems that use recycled materials, fluctuations in batch to batch barrier performance may be more pronounced. Using such moisture prediction models can help evaluate the impact of recycled material addition on content protection performance and provide reference for desiccant configuration and packaging structure optimization.

Application tips and limitations

Researchers point out that this model is suitable for packaging design of desiccant products and can help determine the optimal amount of desiccant that meets the required service life.

. It should be noted that model validation is based on specific drugs, specific packaging sizes, and specific temperature and humidity conditions. When extrapolating to other products, packaging forms, or environmental conditions, the applicability of parameters needs to be re evaluated. For the packaging materials and additives industry, the value of this method lies in incorporating packaging moisture permeability, moisture absorption behavior of contents, and desiccant configuration into a unified moisture balance framework, providing a reference analytical tool for barrier design and processing stability control of food contact packaging.

Information source:Moisture Change Model for Active Package of Dry Dosage Forms Under Consumer Use Condition， Organized by Herun Chemical.