Greaseproof Property Of Paper Coated And Fabricated By Sodium Alginate And Polylactic Acid

Grease proof paper is a kind of paper that resists the permeation of fat.It is used for packing oily food or articles,which requires non-toxic,good anti-grease performance and does not corrode the packaged articles.With the development of food delivery industry in recent years,the demand for food wrapping paper has increased dramatically.The traditional method was through film covering on the surface of base paper or coating with fluorinated compounds to achieve oil barrier,but the film will lose oil barrier once broken and harmful migration to human health.Due to the low surface tension of the oil,it is usually difficult to make the solid surface oleophobic.In this paper,two kinds of sodium alginate biopolymer-based oil-proof paper were prepared by coating method,the factors both the permeability and surface energy affecting oil resistance were discussed.Secondly,polylactic acid thin films with rough microporous structure were constructed by breath figure method and the rough structure was constructed on the base paper,and the wettability and wetting model of microporous surface were discussed.Firstly,the effect of air permeability on sodium alginate/carboxymethyl coated paper was discussed.The results showed that when the coating weight increased from0.5 g/m~2 to 3.0 g/m~2,the coating thickness increased,the air permeability of the paper decreased,and the oil resistant grade increased.When the coating weight exceeds 1.9g/m~2,the air permeability reaches the measurement limit 0.265 mL/min,and the oil proof grade of coated paper reached Kit 9.Secondly,the effect of surface energy on oil resistance of sodium alginate/propylene glycol alginate(SA/PGA)coated paper was discussed.It was found that with the increase of PGA ratio,the surface energy decreased and the oil resistance increased.But for the coatings with high surface energy(SA/PGA=1:0),the proportion of polar components is higher than that of other samples,and the oil resistant grade is 7.Therefore,the large polar component of high surface energy can significantly improve the oil resistance.In addition,the tensile strength and elongation at break of the coated paper were improved obviously.Polylactic acid(PLA)thin films with honeycomb microporous structure were fabricated by breath figure method,and the anti-wetting property of the surface was discussed.Firstly,the effects of temperature,reaction time,casting volume,solvent,polymer concentration and humidity on the oil wettability of microporous films were investigated.The results showed that when the temperature was 27.8?,the reaction time was 10 min,the casting amount was 20?L,the concentration was 50 mg/mL,the maximum contact angle of PLA/D microporous films at the humidity 58%RH was89.9°;and the maximum contact angle of PLA/C films at the humidity 84%RH was96.4°.Secondly,the microporous film is compounded with the base paper,and the oil proof grade of both coated paper reached 12.And the wettability of paper surface was also improved,the contact angle of coated filter paper was 88.8°,and that of coated handsheets was 97.7°.Finally,the wetting law of microporous surface is studied.By constructing different microstructures,adding microcrystalline cellulose and surfactants,it was shown that the smaller the conformational entropy was,the more uniform and orderly the surface was.At the same time,with the increase of the hole depth and roughness,the contact angle can be larger on the surface of the microporous film,and the moist resistance can be improved obviously.The relationship between the contact angle and the surface roughness of the microporous film showed a positive correlation.The wetting state of the PLA microporous film surface was transformed from the intermediate type of coexistance to the Cassie model.