Analysis of sealing and pressure resistance of outdoor drinking water bag

Abstract: the application scope of outdoor drinking water bag is expanding day by day, correspondingly, the quality is also uneven At present, there is a lack of a perfect quality standard in this field to control the performance of outdoor drinking water bag In this paper, TPU water bag and EVA water bag are tested and analyzed from two aspects of sealing and pressure resistance It is found that the main reason for the performance difference of water bag is the heat sealing process, sealing process and material factors Key words: outdoor water bag, sealing, pressure resistance, TPU, EVA under the guidance of healthy life attitude, outdoor sports are more and more favored by people, thus promoting the professional development of outdoor sports, especially the specialization of sports equipment Among them, the outdoor drinking water system is constantly updated under the promotion of convenience and lightweight demand, which gives birth to the modern drinking water system represented by "outdoor drinking water bag" In the early stage of the birth of outdoor drinking water bag, the outdoor drinking water device is generally a simple animal skin bag, and then gradually developed into a metal or plastic container As a drinking water system used in outdoor sports, the defects of metal / plastic containers are obvious: first, the self weight is large and the capacity is limited Generally speaking, the general water capacity of metal / plastic containers is 0.5L ~ 2L, which is slightly insufficient to meet the water supplement requirements of medium and long-distance sports or high-intensity sports In terms of self weight, take 1.5L stainless steel kettle as an example, its net weight is about 500g (without water), which will bring extra load to the sportsman Although the self weight of plastic containers is light, there are hidden dangers in the safety and puncture resistance of plastic materials, which are not conducive to use in the complex and changeable natural environment 2、 It's not good for carrying Metal / plastic containers are usually equipped with single shoulder straps for shoulder or waist carrying, which is easy to cause mobility inconvenience And the stress part is concentrated at one point, which is also easy to cause fatigue accumulation 3、 It is also the least important point, that is, inconvenient drinking water Most metal / plastic containers are designed to be opened with screw cover, which is not suitable for some outdoor sports, such as riding, climbing, cross-country running, etc., which are unable or inconvenient to use the two hands to open the bottle of drinking water The above defects of metal / plastic containers provide space for the development of outdoor drinking water bags The basic configuration of outdoor drinking water bag includes bag body, water injection port and sealing cover, water outlet seat with self-locking device, water nozzle with self-locking device and water outlet pipe, as shown in Figure 1 At present, in addition to the basic configuration of water bags, there are backpack type water bags on the market It is equipped with backpack type wrapping system outside the water bag, which is easy to carry and has more protection The advantages of outdoor water bag are obvious: the self weight of 2.5L TPU water bag is lighter and larger, and the self weight range of 2.5L TPU water bag is 140-180g, which is more than 50% less than that of 1.5L stainless steel water bottle; the backpack design makes the water bag stick to the back with the least load-bearing capacity of human body, and the force is scattered, so it is not easy to generate fatigue, at the same time, it also has the cooling effect that the traditional water bottle does not have; in addition, the way of drinking water has changed significantly, The water can be drunk through the water spout containing the biting water pipe, which does not hinder the work of both hands, and is suitable for riding, climbing and other special sports Based on the above advantages, the water bag is not only popular in the outdoor field, but also extended to the military (separator) field It integrates multiple functions of water, pillow pad and backpack, and becomes an important part of modern combat equipment Fig 1 The outdoor water bag should be well sealed, pressure resistant and have high mechanical strength However, the current situation is that the rapid development of outdoor drinking water bags leads to uneven quality, which is mainly manifested in water leakage at the joint, rupture at the weak part of the bag under heavy pressure and a small number of puncture problems At present, there is no national standard for outdoor drinking water bag, the author refers to the relevant national standards of packaging film and packaging container, and tests the sealing and pressure resistance of two materials of outdoor drinking water bag Sealing performance: refer to GB / T 15171-94 test method for sealing performance of soft package The test instrument is mfy-01 sealing tester Pressure resistance: refer to GB / T 4857.4-2008 Basic test for packaging and transportation packages Part 4: compression and stacking test method by pressure testing machine The test instrument is i-boxtek 1700 carton compression tester 1 Sealing (1) generally, the whole heat sealing process is used for the edge sealing of water bag The high frequency electron tube of high frequency plastic welding machine vibrates and resonates the molecules inside the material, which causes the molecules to rearrange and generate heat energy, and to fuse again under a certain pressure This process does not use glue, safety and environmental protection, but we need to pay attention to the reasonable pressure and time of heat sealing If the pressure is too large and the time is too long, it is easy to cause the material at the edge to be pressed too thin and the strength to be weakened; otherwise, the sealing is not true and the ideal sealing strength can not be achieved In both cases, strong pressure leakage is easy to occur According to the provisions of GB / T 15171-94, place 10 samples (5 of two materials) into the vacuum chamber filled with water of the instrument in turn, close the sealing cover of the vacuum chamber to vacuumize internally, and the minimum vacuum degree of the vacuum chamber shall not be less than 90kpa During the observation, if there is no continuous bubble generation and no water infiltration during the unsealing inspection, the sample is qualified, otherwise it is unqualified See Table 1 for test results The results show that there are three and four leaks in TPU material and ten leaks in EVA material, and the leaking parts are the sealing cover and the sealing edge respectively It can be seen that compared with the surface of the capsule, the edge sealing of the water capsule and the connection of the accessories are more likely to leak, which can be attributed to two reasons: (2) the poor sealing of the connection between the water injection cover and the water injection port The structure of the water filling cover of the drinking water bag is shown in Figure 2, and the sealing effect is determined by the engagement of the thread and the silicon rubber ring Thread engagement refers to the number of thread turns from the first engagement point between the thread starting point of the screw cap and the thread starting point of the bottle mouth to the point where the sealing surface of the bottle mouth contacts the liner The larger the thread engagement area is, the better the positioning of the water injection cap is, the greater the effect of the fixed torque to keep the cap in place is, and the better the sealing is The silica gel ring plays the role of sealing the small uneven parts of the sealing surface of the water injection nozzle, so it should have enough elasticity and rigidity, and keep it The leakage of the joint between the water injection cover and the water injection port is mainly due to the design defects of the thread and the aging of the silicone rubber ring Figure 2 Structure of water injection cover of drinking water bag 2 Pressure resistance (1) the mechanical strength of TPU material, such as tensile strength, elongation at break, puncture strength, etc., is better than that of EVA material Under the external pressure, the pressure resistance of TPU is better TPU is a thermoplastic polyurethane elastomer, which is made of polyether / polyester diol, organic diisocyanate compound and chain extender by gradual addition polymerization The molecular chain of TPU is composed of soft chain segment and hard chain segment, polyether / polyester diol is composed of soft chain segment, isocyanate, chain extender and crosslinker are composed of hard chain segment [1] Among them, the elastomer polymerized by polyester polyol has high tensile strength, tear strength and puncture strength [2] because there are more polar ester groups in the polyester polyol molecules and the cohesive energy is large, which can form strong intramolecular hydrogen bond With the addition of chain extender, the proportion of hard chain segment increases, the density of hydrogen bond increases, the density of physical (separator) cross-linking increases, which strengthens the aggregation between rigid chain segments and improves a series of mechanical properties such as the tensile strength of TPU [3] EVA refers to ethylene vinyl acetate copolymer, which is formed by copolymerization of ethylene (E) and vinyl acetate (VA) Its performance is affected by VA content When VA content increases, such as more than 30%, the elasticity, tensile strength and impact resistance of EVA will be improved, otherwise the above performance will be weakened According to GB / T 4857.4-2008, the "crushing force test" in the instrument is selected Place the specimen in the center of the lower platen of the testing machine, and load the specimen downward with the upper platen at the speed of 10 mm / min until the maximum force measured by the specimen crushing is the test result, as shown in Table 2 By comparison, the average crushing force of TPU water bag is 7.079kn, and the average crushing force of EVA water bag is 5.064kn After the test, the crack positions of 10 specimens were observed, mainly edge sealing fracture and capsule fracture This reflects two problems: Taking the tensile strength as an example, the author cut 10 dumbbell shaped samples from 10 water bags of two materials, according to GB / T 528-1998 test method of tensile strength (equivalent to the meaning of "tensile strength" above) in "determination of tensile stress-strain performance of vulcanized rubber or thermoplastic rubber" has tested it, and the results are shown in Table 3 It can be seen that the tensile strength of TPU material is better than that of EVA material (2) for the specimen whose crushing fracture position is located in the edge sealing, the quality of the edge sealing has problems, which can be improved from the heat sealing process analyzed above It is concluded that the application scope of outdoor drinking water bag is expanding day by day, and the corresponding quality is also uneven At present, there is a lack of a perfect quality standard in this field to control the performance of outdoor drinking water bag In this paper, TPU and EVA water sachets, which are two kinds of water sachets at present, are tested from two aspects of tightness and pressure resistance, and the influencing factors are analyzed briefly, hoping to be helpful to the relevant enterprises Reference [1] Zhan Zhongxian, he Junling Study on the physical and crystalline properties of thermoplastic polyurethane elasticity [J] Elastomer, 2007,17 (4): 31-35 [2] Zhan Zhongxian, Zhu Changchun Factors affecting the physical properties of thermoplastic polyurethane elasticity [J] Polyurethane industry, 2005,20 (1): 17-20 [3] Han Hai (separator) Jun, Ding Xuejia, Zhang Lijuan Study on physical and rheological properties of thermoplastic polyurethane elasticity [J] Plastics industry, 2010,38 (4): 109-112