Polypropylene (PP) has a high recycling potential. However, the properties of mechanically recycled PP (R-PP) have not been fully compared to those of virgin PP (V-PP). Therefore, in this study, properties of R-PP and V-PP were compared using data from recyclers, virgin plastic suppliers, and the literature. The properties of recyclates could not be directly correlated either with the properties of the virgin polymers from which the recyclates were made or the recycling parameters. It was found that the MFR of R-PP was higher; MFR R-PP had a median value (m) of 11 g/10 min while MFR V-PP had a median value of 6.3 g/10 min (at 230 °C and with 2.16 kg). In terms of mechanical properties, in many cases R-PP exhibited stiffer and more brittle behavior, with a slightly higher Young’s modulus (E_R-PP = 1400 and E_V-PP = 1200 MPa), a reduced elongation at break (ɛb_R-PP = 4 l.-% and ɛb_V-PP = 83 l.-%), and notched charpy impact strength (NCIS_R-PP = 4.8 and NCIS_V-PP = 7.5 kJ/m²). However, the values for every property had a broad distribution. In addition to existing information from the literature, our research sheds fresh light on the variation of the characteristics of recycled polypropylenes presently on the market.

Silica gel is a well-known desiccant. Through dispersion of silica gel in a polymer, films can be made that absorb and desorb water vapor. The water vapor absorption becomes reversible by exposing such films to a water vapor pressure below that of the water vapor pressure during absorption, or by heating the film. The intention of this study was to achieve a better understanding about the water vapor absorption, permeability (H₂O, N₂, O₂, CO₂), and mechanical properties of films with dispersed silica gel. Low-density polyethylene (PE-LD) monolayer films with a nominal silica gel concentration of 0.2, 0.4, and 0.6 g dispersed silica gel per 1 g film (PE-LD) were prepared and they absorbed up to 0.08 g water vapor per 1 g of film. The water vapor absorption as a function of time was described by using effective diffusion coefficients. The steady state (effective) water vapor permeation coefficients of the films with dispersed silica gel were a factor of 2 to 14 (8.4 to 60.2·10⁻¹² mg·cm·(cm²·s·Pa)⁻¹, 23 °C) higher than for pure PE-LD films (4.3·10⁻¹² mg·cm·(cm²·s·Pa)⁻¹, 23 °C). On the other hand, the steady state gas permeabilities for N₂, O₂, and CO₂ were reduced to around one-third of the pure PE-LD films. An important result is that (effective) water vapor permeation coefficients calculated from results of sorption and measured by permeation experiments yielded similar values. It has been found that it is possible to describe the sorption and diffusion behavior of water by knowing the permeability coefficient and the sorption capacity of the film ( ${\mathrm{P}}_{\mathrm{eff}.}\approx {\mathrm{S}}_{\mathrm{eff}.}·{\mathrm{D}}_{\mathrm{eff}.}$ ). The tensile stress changed only slightly (values between 10 and 14 N mm⁻²), while the tensile strain at break was reduced with higher nominal silica gel concentration from 318 length-% (pure PE-LD film) to 5 length-% (PE-LD with 0.6 g dispersed silica gel per 1 g film).

Despite extensive sorting, packaging waste often contains a mixture of different materials that make high-quality recycling difficult, especially in the case of flexible packaging. This is partly due to the widespread use of multi-layer laminates and packaging consisting of different inseparably combined materials. To improve the post-consumer recyclate quality and develop optimised recycling processes, it is important to generate a comprehensive understanding of the composition of the sorted packaging waste streams. Therefore, in this study, polyolefin sorting fractions for flexible packaging waste from three European countries are analysed in detail. By selective extraction of the different plastics, their mass fractions in the waste streams are determined. This shows that the PE-rich sorting fractions for flexible packaging are made up of 85–90% of PE, but also contain a certain proportion of foreign materials. A detailed analysis of the layer structures of various types of packaging also provides information on the prevalence of multi-layer packaging and the polymer and non-polymer materials used therein. This shows that particularly in food packaging, with 63–84% of multi-layer and 50–70% of multi-material packaging, a high proportion of foreign materials is used and introduced into the sorting fractions. These insights provide a valuable contribution to the development of recyclable packaging, potential sorting streams and recycling processes, especially with regard to the challenges of the closed-loop recycling of food packaging.

Flexible organic electronic devices are often protected from degradation by encapsulation in multilayered films with very high barrier properties against moisture and oxygen. However, metrology must be improved to detect such low quantities of permeants. We therefore developed a modified ultra-low permeation measurement device based on a constant-flow carrier-gas system to measure both the transient and stationary water vapor permeation through high-performance barrier films. The accumulation of permeated water vapor before its transport to the detector allows the measurement of very low water vapor transmission rates (WVTRs) down to 2 × 10⁻⁵ g m⁻² d⁻¹. The measurement cells are stored in a temperature-controlled chamber, allowing WVTR measurements within the temperature range 23–80 °C. Differences in relative humidity can be controlled within the range 15%–90%. The WVTR values determined using the novel measurement device agree with those measured using a commercially available carrier-gas device from MOCON^®. Depending on the structure and quality of the barrier film, it may take a long time for the WVTR to reach a steady-state value. However, by using a combination of the time-dependent measurement and the finite element method, we were able to estimate the steady-state WVTR accurately with significantly shorter measurement times.

The integration of platelet-shaped montmorillonite particles to improve the oxygen barrier of polyvinyl-alcohol-based barrier layers is state-of-the-art, but research on roll-to-roll coatings of such composite barrier lacquers has not been widely published. In this study, two different coating techniques, slot-die and reverse gravure, were used on a roll-to-roll scale to apply barrier lacquers comprising polyvinyl alcohol and montmorillonite. The lacquers were analyzed regarding viscosity at certain shear rates and surface energy and the dried coating layers regarding oxygen barrier, surface morphology, and particle orientation. Low permeability coefficients delivering a high oxygen barrier of 0.14 and 0.12 $\frac{{\mathrm{cm}}^3\left(\mathrm{STP}\right)1\mathsf{\mu }\mathrm{m}}{{\mathrm{m}}^2\mathrm{d}\mathrm{bar}}$ were achieved for the coating layers with slot-die and reverse gravure coating, respectively. It turned out that the properties of the barrier lacquer need to be adjusted to the coating technique to achieve high oxygen barrier performance. By tailoring the barrier lacquer formulation, the orientation of the platelet-shaped montmorillonite particles can be achieved using both techniques. A low solid content of down to 3$\mathrm{wt}\%$ is preferable for the premetered slot-die coating, because it results in low agglomeration quantity in the coating layer. A high solid content of up to 9$\mathrm{wt}\%$ is preferable for the self-metered reverse gravure coating to assure a homogeneously coated layer.