The development of bio-based polymer materials, such as polylactic acid (PLA) -based polymers, is an effective strategy to reduce dependence on petrochemical-based polymers. However, the preparation of bio-based polymers with high barrier properties is a major challenge. To overcome this challenge, a nacreous layer structure with a ‘ brick and mud ’ pattern is mimicked to improve the overall performance of the material. In this paper, Poly ( L -lactic acid) (PLLA) and Polypropylene Glycol (PPG) was combined to prepare bio-based polyurethane (PU-PLLA), which is used as the slurry structure of nacreous layer. The bio-based biomimetic composite membrane (PU-PLLA/BN) is then obtained by adding boron nitride (BN, brick structure of pearl layer) to it. The water vapor permeability test results show that the permeability of PU-PLLA material can be reduced by more than 50% by 5 wt.% BN, which is because the addition of BN can increase the length and tortuosity of the gas molecular diffusion path in the composite. Therefore, this pearl-inspired PU-PLLA/BN film has excellent moisture resistance, which opens up a broad road for the practical application of PLLA in flexible laminated packaging.
The emerging of flexible package market compels us to develop printing inks that are eco-savvy and suitable for polymer films. Owing to the advantages of low toxicity, environmental-friendly and cost-effective, water-based inks growingly occur to researchers and the studies on binders for water-based inks unprecedentedly flourish. Notwithstanding, the adhesion on polymer films and the slower dryness rate constrain the water-based inks to be the mainstream in the field of flexible package printing. In this work, a crosslinkable polyacrylate emulsion for water-based inks binders was successfully synthesized via semi-continuous seed emulsion polymerization to improve the adhesion and dryness rate of ink films. Particularly, crosslinkable monomer allyl acetoacetate (AAA) was utilized as crosslinkable monomers, hexamethylenediamine (HDA) was added as a crosslinker. Isobornyl methacrylate (IBOMA) was employed to endow the emulsion with desirable adhesion for water-based inks. The viscosity, surface tension, water contact angle, particle size distribution and glass-transition temperature (Tg) were evaluated to research the influence of the AAA and HDA crosslinkable system. Performances of the acrylate emulsion and the latex films, with emphasis on resistance to Ca 2+ and thermal stability were obviously superior to other polyacrylate emulsions synthesized in this paper. The 100 % adhesion ratio on polyvinyl chloride (PVC) and polyethylene (PE) films and 80.08 % adhesion ratio on biaxially oriented polypropylene (BOPP) was attained with AAA-HDA crosslinkable polyacrylate emulsion. The dryness rate was accelerated from 23 mm/30 s to 40 mm/30 s. This work provides ideas and inspiration for design of the water-based inks that served in flexible package.
Conventional solvent-based polyurethane (PU) adhesives, widely utilized in the flexible packaging industry, have raised environmental concerns due to their emission of volatile organic compounds during use. Therefore, there is growing interest in the development of solvent-free PU adhesives that offer improved cooking resistance and use environmentally friendly raw materials. Herein, eco-friendly solvent-free PU adhesives derived from biomass sources for flexible packaging applications are reported. Specifically, two biobased polyols were prepared through the ring-opening reaction of epoxy soybean oil with rosin and the reaction of castor oil with 2,2-dimethylolpropionate. The biobased polyols, together with polyester polyols, were then mixed with another adhesive component (prepolymers containing isocyanate) and cured at room temperature, resulting in the PU bioadhesives. The impact of the polyols on the cooking resistance of the bioadhesives was evaluated by peel strength and package-cooking tests. The results revealed that the addition of 10 wt % epoxidized soybean oil/rosin achieved the best adhesive performance. The peel force before and after boiling treatment reached 7.48 and 5.30 N, respectively, an increase of 18.7 and 21.3%, respectively, compared with that of the samples without additives. The introduction of a long-chain fatty acid from vegetable oil and the rigid tricyclic phenanthrene skeleton structure of rosin into the PU adhesives effectively enhanced their hydrothermal and cooking resistance properties. The biomass-based solvent-free PU adhesives developed in this study hold promising potential for partially substituting solvent-based PU adhesives for flexible packaging applications.
危险品化学品经营许可证（带存储）