Application progress of rosin in food packaging: A review

Foodborne illness caused by Gram bacteria is the most important food safety issue worldwide. Food packaging film is a very important means to extend the shelf life of food. It reduces microbial contamination and provides food safety assurance during the sales process. However, the food packaging material is derived from plastic. Most plastics are not only non-degradable but also harmful to human health. Biodegradable natural polymers are an ideal substitute, but their poor mechanical properties, hydrophilicity and weak antibacterial properties limit their applications. Rosin is an oily pine ester in the pine family, which is a natural renewable resource with a wide range of sources. It is widely used in various fields, such as surfactants, adhesives, drug loading, antibacterial, etc. However, there are only a few reports on the application of rosin in food packaging. It is worth noting that the unique hydrogenated phenanthrene ring structure of rosin can enhance the thermal stability, hydrophobicity and antibacterial properties of food packaging. More importantly, rosin has a wide range of sources, good biocompatibility, and can be degraded in nature. These advantages are conducive to the application of rosin in food packaging. However, previous reviews focused on resins, silicone rubbers and surfactants. In this review we will focus on the application of rosin in food packaging.

Preparation and Properties of Rosin-based Anthraquinone Fluorescent Waterborne Polyurethane

Fluorescent polyurethane has been widely used as fluorescent probes and switches due to its diverse structure and properties, but most of them are solvent-based and synthesized from petroleum-based products. A new type of rosin-based anthraquinone fluorescent waterborne polyurethane (WPU-DAAQ) with good and stable fluorescence properties was synthesized by reacting rosin modified ester (RAG) as a diol and 2, 6-diaminoanthraquinone (DAAQ) as a fluorescent agent with diisocyanate. The structure of WPU-DAAQ was characterized by Fourier transform infrared spectroscopy, UV-vis absorption spectroscopy, and hydrogen magnetic resonance spectroscopy. The fluorescence properties, water resistance, and solvent resistance of WPU-DAAQ were tested. The results showed that DAAQ was successfully grafted onto the polyurethane molecular chain. The fluorescence intensity of WPU-DAAQ increases and then decreases with increasing excitation wavelengths, and increases with the increase of solvent ether content, and is significantly enhanced compared to DAAQ. The dispersion stability was good with the increase of DAAQ. The introduction of DAAQ into polyurethane improved the thermal stability, hydrophobicity, and solvent resistance of WPU-DAAQ. Therefore, WPU-DAAQ is a new type of fluorescent waterborne polyurethane with stable dispersion properties, good fluorescent properties, heat resistance and water resistance.

From rosin to novel bio-based silicone rubber: a review

Rosin is a characteristic natural renewable resource. In view of the unique hydrogenated phenanthrene ring skeleton structure of rosin, it can be designed and synthesized to modify silicone rubber for improving its mechanical properties, thermal stability, and other properties. In this paper, the research progress of silicone rubber modified by rosin and its derivatives is reviewed, including internal or surface modification of room temperature or high temperature vulcanized silicone rubber. The different chemical modifications and polymerization pathways to obtain bio-based silicone rubber (e.g. rosin-based silicone cross-linking agent, filler compound rosin-based silicone cross-linking agent, rosin-based polymer, and rosin quaternary ammonium salt bifunctional antibacterial coating) are discussed and its research prospect is reviewed. Overall, the present review article will provide a quantitative experimental basis for rosin to produce bio-renewable multifunctional silicone rubber to increase our level of understanding of the behavior of this important class of silicone rubber and other similar bio-based polymers.

Preparation and pH Detection Performance of Rosin-Based Fluorescent Polyurethane Microspheres

Rosin-based fluorescent polyurethane emulsion (FPU) was prepared using isophorone diisocyanate, ester of acrylic rosin and glycidyl methacrylate, 1,5-dihydroxy naphthalene (1,5-DN), and 1,4-butanediol as the raw materials. Then, rosin-based fluorescent polyurethane microspheres (FPUMs) were successfully prepared by suspension polymerization method using FPU as the main material, azodiisobutyronitrile as the initiator, and gelatin as the dispersant. FPUMs were characterized by Fourier transform infrared spectra, thermogravimetric analysis, optical microscopy, scanning electron microscopy and fluorescence spectra, and the response performance of FPUMs to pH was studied. The results showed that FPUMs were successfully prepared. With the increase of the level of 1,5-DN, the particle size of FPUMs increased gradually, and the fluorescence intensity increased first and then decreased. When the level of 1,5-DN was 3 wt.%, the average particle size was 49.3 μm, the particle distribution index (PDI) was 1.05, and the fluorescence intensity was the largest (3662 a.u.). The fluorescence intensity of FPUMs increased linearly with the decrease of pH, which can be used for pH detection in solution. Furthermore, the FPUMs exhibited good thermal stability, anti-interference and recoverability.

Fast and Reversible Photoresponsive Self-Assembly Behavior of Rosin-Based Amphiphilic Polymers

Designing stimulus-responsive amphiphilic polymers with a fast photoresponsive self-assembly behavior remains a challenge. Two series of rosin-terminated and azobenzene-terminated amphiphilic polymers (PAM_n and PMA_n) with fast and reversible photoresponsive properties were prepared using rosin-based azobenzene groups and polyethylene glycol, respectively. Under 5-10 s of UV irradiation, the polymers showed trans-to-cis isomerization and reached a photosteady state. For the PAM_n polymer, the absorbance of the absorption peak at 325 nm recovered to more than 95% of the initial value under visible light for 5-10 s, whereas that of the PMA_n polymer recovered completely. Notably, the PAM_n and PMA_n polymers initially self-assembled to vesicles or spherical micelles, and various morphological changes were achieved by manipulating UV irradiation time, with the initial morphology again recovered under dark conditions or visible-light irradiation. Remarkably, vesicles of the PAM₃₄ and PMA₃₄ polymers presented an intermediate open-vesicle state before being completely deformed under UV irradiation because of the existence of a π-π interaction. Finally, the ability of PAM₃₄ and PMA₃₄ polymer vesicles to perform the controlled release and reversible loading of a fluorescent probe was evaluated.