| PE is an important source of flexible packaging materials. It can be seen everywhere in ourdaily life and industrial production because of its high quality and low price. It occupies themajority of market resources. Because of PVC film, poison milk powder, waste plastic drinkingbucket, disposable foam boxes and other series of events, food safety caused by food packagingmaterials should not be underestimated. At present, the widely used soluble ink in ester andpolyurethane adhesive in the enterprise are the important source of residual solvent.And the useof water-based ink and composite technology without solvent are difficult to be promoted. In thispaper, in order to meet the packaging and printing performance, we only change themicrostructure of LDPE to reduce the residual solvent. It avoids the complicated productionprocess and saves the cost of production.Composite material obtained from nano-SiO2with LDPE in different proportions was takenas the objective of this research. The crystallization, free volume, mechanical properties, thermalstability and barrier property of composite material were analyzed. The influence of Ethyl acetateon the isothermal adsorption dynamics of modified low density polyethylene films was analyzed.Firstly, the experiment discovered nano-SiO2dispersed uniformly in modified film bymelt blending preparation. And it formed strong interfacial bonding with the substrate. Itimproved the mechanical properties, composite strength, ink adhesion of modified LDPE.When the content of nano-SiO2is0.21%, the mechanical properties was the best.In addition, itpromoted heterogeneous nucleation, the crystallization of LDPE and grained refinement.Melting temperature, glass transition temperature and the initial decomposition temperature ofLDPE was rising. The comprehensive properties of the composite material were improved.Secondly, the positron annihilation test results showed that the nano-SiO2makes the freevolume of LDPE decrease. As this, small molecular oxygen diffused in more fine segment spacethrough LDPE’s micro pore more slowly. The decrease of free volume fraction resulted in thereduction of oxygen.To further explore the mechanism of residual solvent, the solubility parameter analysis ofpolymer and solvent molecules found that nano-SiO2improved the solubility parameters ofLDPE, increased its polarity and decreased the compatibility with the weak polar solvent. At lastit reduced the residual solvent in film. Residual solvent from ink: residual ethanol decreased by6%-25%, residual acetone decreased by1%-27%, residual ethyl acetate decreased by22%-42%,residual toluene decreased by18%-84%. Residual solvent from adhesive: residual ethanoldecreased by27%-36%, residual acetone decreased by7%-17%, residual ethyl acetatedecreased by30%-33%, residual toluene decreased by12%-30%. The modifier greatly reducedthe residual ethyl acetate, toluene. Especially for toluene, which was up to84%. Finally, adopting impregnating-weighing method to analyze the influence of ethyl acetateon the isothermal adsorption dynamics of modified low density polyethylene films. Lagergrenfirst-order model and the second-order model could analyze the ethyl acetate adsorptionprocess. The determination coefficients of the second-order model were more than0.999,indicating that the second-order model could describe the ethyl acetate adsorption process moresuccessfully.The ethyl acetate in modified low density polyethylene film adsorption processincluded multilayer adsorption at first and chemical adsorption later.The study providedtheoretical guidance for the reduction of residual solvent.In this study, the modified LDPE by using self-made nano-SiO2could maintain or improvethe original performance. And the residual solvent was greatly reduced. Besides, the preparationtechnique was simple and suitable for industrial production.It had provided the powerfulsafeguard for food safety. |
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