​​4 things to know about the humidity of the paper packaging

Understand the humidity of paper packaging

Paper moisture is the hygroscopic property of paper. Water absorbence changes the mechanical properties of paper, causing cellulose fibers to plasticize, making the link between the fibers loose and weakened. The moisture level in carton paper also changes the absorption and reflection of infrared and microwave bands.

In addition, humidity also affects the quality of paper packaging, leading to the impact on the printing and processing of finished products. Typically, newly made carton or paper usually has lower humidity than the ambient humidity.
 
Each type of packaging paper has a certain moisture content. The difference in humidity in the paper varies from 2% - 12% depending on the content of steam, the amount of powder used, the grinding level and chemicals used in the manufacturing process.

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The role of the humidity index in printing paper packaging

Because humidity affects the quality of printing in packaging, most packaging businesses have to apply many methods to regulate the balance, contributing to improving the quality of paper as cartons in offset printing.

Specifically, the humidity index will greatly determine the shape and quality of paper boxes and cartons. According to the research of printing experts, the speed of dry paper is half as fast when it is soaked in water. When equilibrium is reached, the rate of change will slow down.
 
If the paper rolls are stored in high humidity conditions for 6 months, there will be about 12cm of paper moist with the outside environment causing wavy edges of the paperboard to make cartons.
 
Abnormal changes in humidity will cause the paper to warp and wavy, since some individual fibers on a certain part of the paper swell more than others. When the paper moisture content of packaging is in the range of 5% - 6%, the damage level will be highest. The pulp of the box, offset printing carton shows how the paper withstands the pressure until it is torn. When the humidity of paper fluctuates above 18%, the value of damage level will decrease in the range of approximately 10%.
 

Method of determining humidity of paper packaging

Currently, the optimal method to help determine the humidity of paper packaging is the drying method in laboratory. This method is applicable to most corrugated carton paper, rigid carton, which does not contain volatile substances at the specified temperature of the test method.

A number of equipment necessary to test the humidity of packaging products, including: scales, sample containers, weighing cups, weighing boxes, ovens, etc. In order for the measurement to be carried out quickly and accurately, these items must meet certain standards.
 
In particular, it is worth noting that the sample of paper boxes and cartons participating in the test must meet the standards of TCVN 3649: 2000. The sample is torn into small pieces with a minimum mass of 1g. At the time of sampling, the test piece should weigh at least 50 g and shred or fold the pieces into a weighing box.

When tested, the weighing boxes were washed, numbered, opened and placed in an oven, dried at 105 ° C ± 2 ° C for 1 hour to determine absolute dryness. Continue the same procedure until the test piece has a constant mass, which is considered when the difference between two successive weighings is not greater than 0.1% of the original mass.

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Maintaining humidity to preserve paper boxes and cartons

Typically, businesses often use the method of regulating paper status to control paper moisture as packaging. This is the moisture-recovery process for paper, aiming to reduce paper deformations during storage and use. Conditioning paper carton packaging is a method of preserving paper in an environment with stable humidity. This environment will cause the humidity of the paper to increase, corresponding to the equilibrium of the surrounding environment, the fibers become soft, thus releasing the stresses inside the paper. This is a condition for reducing paper deformation during storage.
 
Controlling the humidity of paper boxes and cartons is an important issue to improve the quality and limit the deformation of paper in the production process. Therefore, paper packaging companies need to invest and study the hygroscopic properties of the packaging to have an appropriate preservation method.

Khang Thành - The packaging manufacturer in Vietnam specializes in producing paper bags, carton box, carton offset, labels, hangtag, books, calendar, POSM and so on.