Analysis and improvement of leakage of a chemical

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Analysis and improvement on leakage of a chemical product packaged in glass bottles Abstract: glass bottles are equipped with ABS plastic bottle caps to pack phosphoryl fluoride containing chemicals, and there are bottle caps and bottle heads damaged and product leakage. The root cause is the incompatibility between phosphoryl chemicals and packaging materials. Therefore, it is suggested that the materials of bottle cap and gasket should be re selected through compatibility test, the aging problem of plastic should be paid attention to in material selection, the quality of glass bottle should be improved, and the tightening torque should be unified

key words: glass bottle; packing; ABS bottle cap; Plastic; leak; reason; Ten years ago, in response to the packaging demand of a chemical product, the author participated in the development of glass bottle packaging and put it on the market. The body of the packaging bottle is a 50ml/. I type screw mouth glass medicine bottle. The bottle cap is made of ABS engineering plastic. There are double-layer gaskets in the bottle cap. The surface layer is 0.2mm thick polytetrafluoroethylene gasket and the inner layer is 2mm thick butyl rubber gasket. Recently, customers have reported that the above packaging has leaked. After visiting customers, it was found that more than 50% of the packages had bottle caps swelling, cracking or loosening, a small number of bottle mouths showed signs of corrosion, and only a small number of packages were in good condition. As the product is toxic and there are potential safety hazards due to package leakage, all packaged products shall be recovered at the request of customers, causing significant economic losses to the enterprise and adverse impact on the enterprise reputation

the quality of the chemical products was very good, and they were welcomed by customers when they were put on the market. It was not expected that the packaging was small. 2. The operation inspection of the cross beam of the rubber tensile testing machine led to a major event and a painful lesson. In addition to not paying enough attention to packaging at the beginning, there are other deep-seated reasons, which are summarized as follows

l cause analysis of glass bottle packaging leakage

according to the nature of chemical products, combined with the problems and phenomena in packaging, it is found that the problems in packaging containers are caused by the following reasons:

1) incompatibility between packaging containers and chemical products. The chemical product is a hydraulic universal testing machine containing acyl fluoride. It is an ideal experimental equipment for industrial and mining enterprises, building materials, quality inspection centers, water conservancy and hydropower, bridge engineering, scientific research institutions, and mechanical laboratories of colleges and universities. The product is unstable in nature. During storage, dealkylation reaction occurs to generate olefin gas, causing a certain pressure in the bottle, resulting in loosening or cracking of the bottle cap. Once the bottle cap is loosened or broken, and the seal is not tight, on the one hand, the bottle cap will directly contact with the product vapor and its decomposition product - olefin gas, causing swelling; on the other hand, the water vapor will enter, causing the product to hydrolyze and generate hydrofluoric acid, which is corrosive to the glass. The hydrofluoric acid concentration at the bottle mouth is high, and the corrosion at the bottle mouth is obvious. This is the main cause of packaging problems

2) bottle cap. ABS plastic is susceptible to stress corrosion cracking and aging. ABS plastic is easy to crack due to stress corrosion. The bottle cap is stressed due to tightening and sealing, and the olefin gas produced by product decomposition intensifies the stress on the bottle cap, resulting in the cracking of ABS plastic bottle cap. ABS plastic is easy to age _] l. The general service life is 8 ~ 10 years, and the service life is shorter under the environment of stress and chemical medium. As some products are stored for more than 10 years, their mechanical strength decreases, which is also an important reason for bottle cap cracking

3) the tightening torque of bottle cap is not uniform. There is only one sealing surface between the bottle cap and the glass bottle mouth. The composite gasket processed from polytetrafluoroethylene and butyl rubber plate is hard, and the sealing between the bottle cap and the bottle mouth must be ensured by tightening. As the product packaging is manually operated, the tightening torque of different people is not uniform, resulting in different sealing effects

4) the glass bottle has quality problems. The glass bottle is a tube bottle, which is semi mechanically and semi manually processed. Affected by human factors, the homogeneity is poor, the threads of some bottle heads are quite different, and the matching with the bottle cap is poor. In addition, the double-layer gasket is prone to displacement and non coincidence. Even under the same tightening torque, there will be a problem of loose sealing

2 suggestions and experience on improving packaging

in case of leakage of packaging, there are the following suggestions and experiences:

1) great attention must be paid to packaging. Packaging is a part of the product and a means of putting the product on the market. Good packaging can increase the appearance beauty and arouse customers' desire to buy on the premise of satisfying customers' use. Foreign countries attach great importance to product packaging, and the packaging cost of some products even exceeds the value of the product itself. At present, many enterprises in China do not pay attention to product packaging, resulting in product prices and export difficulties. The cost of not paying attention to packaging is too high. I hope we can learn from it

2) material compatibility test must be conducted for product packaging. Whether the product is compatible with the packaging container material is the key to determine whether the packaging container is applicable. The packaging container material must be selected through the compatibility test. All containers, sealing gaskets and bottle caps that may be in direct contact with the product shall be selected through compatibility test. Some products are judged from experience to be compatible with the packaging container materials, but they are incompatible in case of accidents. For example, the above phosphate ester is compatible with glass according to literature reports and theoretical analysis, but when the package is not tightly sealed and water vapor enters, the product will hydrolyze to produce hydrofluoric acid to corrode the glass. Therefore, when selecting packaging container materials, compatibility tests must be carried out under extreme conditions, and experience must not be relied on. In addition, the gasket is the key part of packaging and sealing, and its material should have a certain elasticity. For chemical products with strong corrosivity, expanded polytetrafluoroethylene with good elasticity is more suitable for thread sealing gasket

3) when matching glass bottle with plastic bottle cap, attention should be paid to the aging of plastic. Glass has no aging problem, but plastic has aging problem, and their service lives are inconsistent. Even if the plastic is not subject to stress and corrosion, it is still aged when placed statically. For example, plastic beer bottles were used during the London Olympic Games, and their service life is greatly reduced. If plastic is selected to make bottle cap, aging test must be conducted, and materials with a service life much longer than the storage life of the product shall be selected

4) the sealing torque of glass bottle and plastic bottle cap shall be unified. The hardness and strength of the glass bottle and the plastic bottle cap are not the same. If the torque is too small, the sealing effect will be poor, while if the torque is too large, the tripping sealing effect will be poor. The sealing effect can be guaranteed only if the torque is moderate. Conditional. Special tool seals with torque can be designed and processed; Unconditionally, let the same person tighten it full-time

5) the glass bottle processing quality must be guaranteed. Glass bottles are divided into tube bottles and molded bottles. According to the meaning of the name, they are divided according to the processing method. Moulded bottles are developed with high-quality CFRP parts from South Korea, which are relatively standardized. It is best to select moulded bottle enterprises to process glass bottles. However, if the order quantity is small and the mold bottle enterprises are unwilling to process, they must choose the processing enterprises with pure mechanical method and pay attention to the acceptance. In any case, the glass bottle must not be made by hand

renfujian, wangcongmin, malixin, Chang Ying

(1. room 603, mailbox 1043, Beijing; 2. State Key Laboratory of Explosion Science and technology, Beijing University of technology

source: Packaging Engineering

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