Increased environmental and health concerns over the use of plastic packaging or fluorine-containing coatings,in combination with increased market demand for products with a longer shelf life,make bio-based materials one of the most important research candidates for alternative paper packaging materials for oil resistance.These bio-based materials have excellent oxygen and oil barriers,which are critical for food packaging.Moreover,they are biodegradable,naturally renewable,and safe.In this artical,two main groups of bio-based oil repellents for paper food packaging,including polysaccharide-based biopolymers and protein-based biopolymers,are enumerated,and the advantages and weaknesses of bio-based oil repellents are discussed,and effective solutions are proposed.Finally,research status and prospects on the development of bio-based oil-resistant coatings for the food packaging industry are presented.
The covers of booklets and books in folk documents primarily serve to protect the pages. Owing to long-term storage limitations, a considerable number of book covers have suffered varying degrees of damage. Following the principles of restoration, a comparative analysis and restoration of folk document covers were conducted, selecting four different types of carriers from the Taihang Mountain Documents, ranging from the Qing dynasty to the Republican Era. These carriers included hemp, mulberry bark, and machine-made paper, and cotton blue cloth. Each cover type was matched with an appropriate restoration paper, and different methods were employed during the restoration process. Through restoration, the previously damaged document covers can continue to fulfill their role in protecting the books, thereby extending the lifespan of these four folk documents.
The earliest description of Cai Lun is that of an inventor of papermaking,which is included in historical books such as Dong Guan Han Ji and The Book of the Later Han;later,in his hometown,he was also inked by scholars because of some monuments about him,or the authors used his experience to express their own emotions.Recently,Cai Lun's image has been clarified in textbooks,literary works,and urban civilization construction and is no longer considered merely a pioneer of papermaking.The development of his historical and literary image derives not only from the need for academic research but also the need to establish the Chinese nationalism and patriotism and promote traditional culture.
Power consumption is the energy source of the impact on fibers or pulp during low-consistency(LC)pulp refining,and the strength of refining affects refining quality and efficiency.The pulp properties,operating parameters,and bar parameters of the refiner plates are important parameters affecting refining efficiency,which can be defined as the ratio of net to total refining power.In this study,LC refining trials for pulps with different consistencies and fiber lengths were conducted using five isometric straight-bar plates with different bar angles to explore the influences of the plate bar angle and pulp properties on the no-load power,impact capacity on fibers and refining efficiency.It was found that the no-load power of the LC refining process decreased with an increase in the plate bar angle while increased when pulp with higher consistency was refined under the same refining conditions.However,the effect of pulp consistency on the no-load power can be neglected when refining is conducted using plates with larger bar angles.Meanwhile,a critical bar angle for straight-bar plates in LC refining may exist,which has the strongest impact on the pulp and highest refining efficiency under the same refining conditions.In addition,the impact capacity of the plate on the pulp and refining efficiency in LC refining can be enhanced by appropriately increasing the pulp consistency and average fiber length when the bar angle of the refiner plate with a sector angle of 40° is less than 30°.Therefore,the efficiency and power consumption of the LC refining process can be adjusted by optimizing the pulp consistency and bar parameters of the refining plates.
Waterborne coatings often delaminate and settle during long-term storage,requiring the addition of thickeners.The effects of nanofibrillated cellulose(NFC)and the commonly used thickener,hydroxyethyl cellulose(HEC),on the storage stability of waterborne coatings were compared in this study.The morphology of NFC was characterized using infrared spectroscopy(FT-IR)and scanning electron microscopy(SEM).The rotational viscosity and rheological properties of the waterborne coatings with NFC and HEC were tested.Stationary settling experiments were also conducted at different temperatures to compare the difference of NFC and HEC on improving the storage stability of the waterborne coatings.The results showed that the waterborne coating with NFC exhibited pseudoplastic fluid characteristics;a small addition of NFC can achieve the same improvement effect on the storage stability of waterborne coatings as HEC.Further,the improvement effect of NFC was not affected by temperature.The waterborne coating with NFC still exhibited good storage stability at high temperatures,which was significantly superior to that of HEC.Therefore,NFC is a feasible agent for improving the prolonged storage stability and warming-induced delamination of waterborne coatings.
