Analysis of the properties of plastic composite pa

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Experimental analysis: the performance of plastic composite packaging materials

I. Introduction

the excellent characteristics of plastic composite packaging materials in food packaging in terms of fresh-keeping, flavor preservation and quality assurance are unmatched by other materials. The study of its material properties and application properties can further expand the scope of use, which is of great significance to the protection of product matching packaging

the following is a preliminary study and Discussion on the thermal properties of different plastic composites, which will further guide us to effectively and scientifically manufacture high-efficiency and special effect composites, and select composites correctly and scientifically

II. Experiment and result analysis

Experiment 1: measure the heat sealing temperature of the plastic film

after the plastic film is printed, it is required that the seal should have a certain strength and firmness in the process of bag making, be able to bear the pressure of a certain weight of the contents, ensure that the goods do not crack and leak in the process of circulation, and meet the requirements of commodity protection. Therefore, the firmness of heat sealing is one of the important indicators to evaluate the quality of commodity packaging. Heat sealing is to use external conditions (electric heating, high-frequency voltage, ultrasonic) to make the sealing part of the plastic film into a viscous flow state, and with the help of the pressure of the cutter, the upper and lower layers are fused into one with each other, which can maintain a certain strength after cooling

experimental method: due to the limitations of experimental conditions, this experiment can only use electric soldering iron heat sealing. But connect it to the voltage regulator. Use a voltage regulator to control the temperature of the electric soldering iron. Cut the spline to 20 × 100mm spline  place the spline on the glass plate  fold the plastic film in half  heat seal with an electric iron. During heat sealing, slowly adjust the voltage of the electric iron to make the temperature of the electric iron rise at a uniform speed. After the sealing is cooled, test its peel strength. The peel test method is to uncover a section by hand, clamp the peeled end with a spring scale, and fix the other end on the glass with a rubber strip. Record the value at full split. The heat sealing time is 0.5 seconds, and the heat sealing pressure is the same each time. Unit of stripping force (n)

experimental record

experimental curve

experimental results and analysis: from the above curve, it can be seen that:

1. LDPE and LLDPE have high stripping strength and excellent heat sealing performance. LLDPE has a wide sealing range, which is due to the improvement of its tensile capacity due to its own structural characteristics

2. The heat sealing temperature range of BOPP is very narrow, the peeling force is low, and its heat sealing performance is poor. The heat sealing performance of all parts of CPP fastening equipment is better than that of BOPP

3. compared with ony, NY, CPP and BOPP, the heat sealing performance of unstressed NY and PP is better than ony and BOPP. This may be due to the fact that after the molecules are oriented, ① its directional arrangement makes the bonding area between molecules small on the bonding, and the bonding fastness is low. If the molecules are arranged in disorder, the molecules can be in arbitrary contact with each other, and the arbitrary bonding fastness between the groups increases. ② from a physical point of view, the surface of the material after the molecules are oriented is firm and smooth, so it is difficult to form a cross penetration bond between the molecules during heat sealing

4. Pet, NY and ony have poor heat sealing performance, so this material cannot be used for the inner layer when making composite films

5. From the perspective of peel force and heat sealing temperature, the heat sealing strength increases with the increase of temperature in the first period of time. When it rises to a certain stage, it gradually decreases with the rise of temperature. The key factor here is that after the temperature is too high, the material is essentially destroyed, and the C and H molecular structures in it are decomposed or carbonized, resulting in poor bonding

Experiment 2: measure the heat resistance, cold resistance and ultraviolet transmission performance of plastic film

1 heat resistance and cold resistance experiment

due to the special requirements of food packaging for hygiene, some plastic packaging needs to be disinfected at high temperature, which requires a certain heat resistance of the film. Quick freezing packaging requires the film to have good low temperature resistance

experimental method: due to the limitation of the test condition that the displacement of the beam is obtained by measuring the output pulse number of the photoelectric encoder, only qualitative measurement method can be used in this experiment. After making the sample into a small bag, heat it in 100 ℃ water for 30 minutes, take it out, measure its puncture resistance, and then make qualitative comparison. This method is also used in the cold resistance experiment. The sample is made into a small bag and frozen in the refrigerator at 0 ℃ for 30 minutes. After taking it out, its puncture resistance is measured

2 UV resistant, sizzling and delicious? Br ultraviolet light can cause the plastic molecular chain to be destroyed by ultraviolet light, which reduces the strength of the film. In addition, the quality of greasy food packaging is easy to change due to ultraviolet radiation, and the discoloration phenomenon is easy to occur in the colored film or packaged yarn dyed fabric, so this kind of film is easy to choose the film with low ultraviolet transmittance

experimental method: due to the limitation of experimental conditions, the emission of CO2 and SO2 can be reduced by more than 64 million tons in China. In this experiment, only qualitative measurement methods can be used, and the instrument used is ultraviolet lamp. Put the spline under the ultraviolet lamp and observe its transmission

experimental records

experimental results and analysis:

1. Pet, my, ony, petvm, CPPVM have good heat and cold resistance  they are ideal substrates for making cooking bags and frozen packaging  LLDPE has better heat resistance than the general method sj/t11141 ⑵ 003 for LED display screen

2. CPP has poor performance in terms of heat resistance

3. In terms of UV transmittance, CPP, LLDPE, CPPVM and petvm have excellent UV resistance, while the others are poor. Therefore, composite films are mostly used in the packaging of fatty foods

the important reason for this is that the molecular structure of these polymers has a certain polarity, or can form hydrogen bonds, and the intermolecular force is strong. They are not pure C.H. very flexible polymers, and then form copolymers. Therefore, its heat resistance, cold resistance and UV resistance are excellent

III. conclusion

through the above experimental results and analysis, we can preliminarily draw the following conclusions:

1. In terms of heat sealing performance, the fastness of heat sealing is related to the molecular structure of the material and the orientation means of the material. The molecules of the material are relatively flexible, the heat sealing temperature is low, the material is easy to heat seal, and the molecules are disordered. During heat sealing, the molecules are easy to interact and combine, the molecular orientation, and the material is firm and smooth, During heat sealing, the molecules are not easy to interact and combine, and the heat sealing temperature is high, so it is not easy to heat seal

2. In terms of heat resistance, cold resistance and UV resistance, the molecular structure of the material has a certain polarity. If the intermolecular force is large or copolymers are formed, the performance of the material will be significantly improved, because their structure leads to their strong resistance to destruction

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