| After the reform and opening up,especially in recent years,with the rapid development of China's construction,people's desire for a high-quality life has gradually increased,and people have started to pay more and more attention to the green health and pollution-free food.The function of packaging is to protect food from contamination and avoid damage.These functions are absolutely related to the strength of its own heat seal.Therefore,how to improve the heat sealing performance of packaging materials is the focus of functional packaging research.At present,most of the packaging materials on the market are made of resin film,and the advantages and disadvantages between resins are obvious,so most resins are restricted in development.Therefore,resin infusion is one of the most common ways to improve the performance of packaging materials.The resins are formed by intermixing and blending to achieve rapid improvement in performance,so as to make up for the shortcomings by combining their respective advantages.Therefore,resin fusion can not only improve its heat-sealing temperature zone,but also enhance its mechanical and sealing properties.The so-called green packaging is to optimize the packaging performance without adding preservatives,so as to maximize the protection of green food?the preservative part of the packaging will migrate to the food surface?.The possibility of additives and preservatives migrating from packaging materials to food is reduced as much as possible,bringing new guarantees for food safety and green.The theme substrate resins currently selected for packaging materials in the market are generally polyethylene?PE?,polystyrene?PS?,and polypropylene?PP?.However,the melting points of these three resins differ greatly,and a single resin film cannot achieve good heat-sealing performance at the same time.In order to solve the practical problem in this life,a film that can be heat-sealed with polyethylene,polystyrene,and polypropylene at the same time is prepared in this paper.The test in this paper is based on the theory of resin fusion.The basic resin material used in this study was linear low density polyethylene?LLDPE?,mixed with polystyrene?PS?,polypropylene?PP?,metallocene polyethylene?m PE?,and ethylene-vinyl acetate copolymer?EVA?.And the film formation after intermixing and blending,the heat sealing temperature zone and physical properties of these five resins after being cast into films when blended at different ratios were studied,and they were separately compared with blank polyethylene?PE?and polybenzene.Ethylene?PS?and polypropylene?PP?films were heat-sealed at different temperatures,and their heat-sealing properties were tested to study the preparation of a film that can be heat-sealed simultaneously with PP,PS,and PE.The resin is mixed in proportions?after the pre-experimental experiments,set to 5 ratios?,and after thorough stirring,it is gradually added to a twin-screw extruder that has been heated to the specified temperature to prepare a master batch.The master batch is added to a casting machine to prepare a film.The prepared film was tested for basic properties,including optical properties,mechanical properties,barrier properties,micro-electron microscopy scanning,heat-sealing performance,and heat-sealing micro-scanning surface,etc.,and its melting point was measured using differential scanning calorimetry.Finally,vacuum-cooked cooked chicken breasts made with films made at different ratios were stored at room temperature,and the effect of the film on the preservation of food packaging was examined to test the heat-sealing strength and sealing effect of the film.The main conclusions are as follows:?1?Four kinds of resins,linear low density polyethylene?LLDPE?/polypropylene?PP?/polystyrene?PS?/metallocene polyethylene?m PE?,are blended into the surface of the film after being blended in different proportions.Smoothness and crystallinity do not have much effect,no porosity and agglomeration occur,compact and dense structure,and good barrier properties,so it has practical application value.After the four resins are blended to make a film,the mechanical properties,barrier properties,thermal stability,and heat-sealing properties of the film have been significantly improved compared to blank linear low-density polyethylene.The temperature range of the heat seal is 120-180?,which is relatively improved.And they can be heat-sealed with PE,PP and PS,and have certain heat-sealing strength.When the linear low density polyethylene?LLDPE?/polypropylene?PP?/polystyrene?PS?/metallocene polyethylene?m PE?ratio is 70:20:5:5?Group B?,the overall performance of the film is relatively Good,can be used as the cover film of PP,PE and PS containers;?2?The ethylene-vinyl acetate copolymer resin is mixed with a linear low-density polyethylene resin according to a certain ratio,and the purpose is to improve the heat-sealing strength of the film and extend the heat-sealing temperature zone of the film.The addition of ethylene-vinyl acetate copolymer will inevitably affect the original structure of the resin.However,the surface smoothness and crystallinity of the film after blending did not have much effect.There were no pores and agglomerations,the structure was compact and dense,and the barrier properties were good.According to the research in the article,it can be seen that the ethylene-vinyl acetate copolymer resin makes the film heat seal The performance has been greatly improved;and the barrier properties of the ethylene-vinyl acetate copolymer/linear low-density polyethylene film have also changed accordingly.This is of practical application value;the elongation at break and mechanical strength increase with the amount of addition.Increases with the increase of;the light transmittance,oxygen,and water vapor transmission volume change with different proportions.When heat-sealed with a blank PE film,a blank PP film,and a blank PS film,it also exhibits strong heat-sealing strength,and the heat-sealing temperature range is 100 to 180?.So practical value.When the modified linear low-density polyethylene masterbatch is added in an amount of 5%?group E?,the film performance is relatively good;?3?Use differential scanning calorimetry?DSC?to measure the melting point of the film when the amount of modified linear low-density polyethylene masterbatch is5%,to calculate its true and effective heat-sealing temperature zone.Through differential scanning calorimetry,it can be concluded that the melting point of the same sample measured by DSC is generally lower than other melting points.There are many factors that affect DSC results,so through orthogonal experiments,the best experimental parameter can be determined as A1B1C1,that is,the heating rate is1?·min-1;the sample amount is 1.5mg;the atmospheric flow rate is 10?·min-1.The melting point of group E film determined by the best experimental parameters increased from 124.621?of the original blank LLDPE film to 152.157?,and the effective heat-sealing temperature should not be lower than the melting point of the material.It can be concluded from the summary that the true and effective heat-sealing temperature of group E films is 139.081?180?;?4?The measurement results of various indicators show that when the addition amount of modified linear low-density polyethylene masterbatch is 5%,the film has the best preservation effect.Without any additives,the heat-sealing strength effect is the most effective.good.When stored at room temperature,the shelf life of cooked chicken breast samples can still be extended to 6 days,and the number of bacterial colonies in cooked chicken breast samples is 4(lg?CFU/g?of cooked meat food specified in GB2726-2016.Because the heat-sealing strength of the film during storage can effectively block the infiltration of moisture and oxygen in the air,thereby inhibiting the growth and reproduction of microorganisms in the packaging bag and ensuring its quality.The results of various test indicators show that the E group film has good sealing performance and has practical application value;?5?The theoretical content of the data analysis after experimental research in this article,although it does have some practical reference value,but in fact there are still some defects,such as the addition of ethylene-vinyl acetate copolymer resin in the experiment Only a few relative gradient experiments have been performed,and all actual conditions may not be covered.Therefore,suppose that the experimental results are to be put into actual production and life.The conclusions of the above experiments do not judge the film well based on the current data.Whether the heat-sealing temperature range and heat-sealing strength have improved has yet to be further analyzed by experimental research results. |
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