Abstract: Tea is a product that is easy to absorb moisture. Its packaging should have strong moisture resistance, so enterprises should strengthen the detection of moisture resistance of tea packaging. In this paper, Labthink blue light W3/031 water vapor transmission rate tester is used to test the water vapor barrier performance of tea aluminum-plated composite film packaging , and the basic process of the test and the applicable scope and equipment parameters of the test equipment are introduced. Enterprises provide reference when selecting relevant testing solutions and equipment.
Key words: tea , soft plastic packaging, moisture resistance, moisture resistance, water vapor barrier performance, weighing method, water vapor transmission rate, water vapor transmission rate tester
1 , meaning
Tea originated in China and has a history of more than 6,000 years. Tea contains catechins, cholestyrene, caffeine, inositol , folic acid, pantothenic acid and other ingredients to enhance human health. Tea leaves are generally in the form of soft plastic packaging or cans, and the packaging should have high moisture resistance and aroma retention.
The tea itself is easy to absorb moisture. If the tea is stored in a high-humidity environment for a long time, and the moisture resistance of the package is poor, the tea is prone to moisture absorption and mildew, and the fragrance is lost. In order to prevent the above problems in the storage and circulation of tea, enterprises should strengthen the regular inspection of the moisture resistance of tea packaging. This paper introduces the detection scheme of moisture-proof performance of tea soft plastic packaging, and helps tea production enterprises to identify the barrier properties of tea packaging to the outside water vapor, so as to screen out the packaging materials with superior moisture resistance.
2 , reference standard
At present, the domestic test methods for water vapor transmission rate of soft plastic packaging include weighing method ( cup method ) , electrolysis method, humidity method and infrared method sensor. The standard methods can be referred to as GB 1037-1988 . Sheet water vapor permeability test method Cup method, GB/T 21529-2008 "Determination of water vapor transmission rate of plastic film and sheet - Electrolytic sensor method", GB/T 30412-2013 "Determination of water vapor transmission rate of plastic film and sheet Humidity Sensor Method, GB/T 26253-2010 Determination of Water Vapor Transmission Rate of Plastic Films and Sheets Infrared detector method. The standard referenced in this paper is GB 1037-1988 based on the weighing method .
3 , test samples
The tea provided by a company is packaged in a soft-coated aluminum-plated composite film.
4 , testing equipment
The testing equipment used in this paper is the Labthink Blue Light W3/031 Water Vapor Transmission Rate Tester independently developed by Jinan Languang Electromechanical Technology Co., Ltd.
4.1 Test principle
Weighing method test principle: During the test, the sample is clamped in the moisture permeable cup, and a certain humidity difference is formed on both sides of the sample. The water vapor will pass through the sample from the high wet side to the low humidity under the action of the humidity difference. Side permeation, by measuring the change in the weight of the moisture permeable cup over time, the parameters such as the water vapor transmission rate of the sample can be determined.
4.2 Scope of application
(1) This equipment is suitable for testing the water vapor transmission rate of films, sheets, paper, cardboard, textiles, non-woven fabrics and other materials.
Film type: various plastic film, plastic composite film, paper-plastic composite film, geomembrane, co-extruded film, aluminized film, aluminum foil, aluminum-plastic composite film, waterproof and breathable film and other film-like materials.
Sheets: sheet materials such as PP , PVC sheet, PVDC sheet, nylon sheet, etc.
(2) This equipment can also be extended to the test of the cupping method of the sample and the water vapor transmission rate test of the liquid crystal display film, the solar backing plate, the sterile protective film, the cosmetic mask and the like.
(3) This equipment meets many national and international standards, such as GB 1037 , GB/T 16928 , ISO 2528 , ASTM E96 , ASTM D1653 , TAPPI T464 , DIN 53122-1 , JIS Z0208 , YBB00092003, etc.
4.3 Equipment parameters
l  The test range of the device is 0.1 ~ 10000 g / m 2 · 24h , and the resolution is 0.01 g / m 2 · 24h .
l  The temperature range of the device is 15 °C ~ 55 °C , temperature control accuracy is ±0.1 °C , humidity control range is 10%RH ~ 98%RH , humidity control accuracy is ±1%RH .
l  The device is equipped with three moisture permeable cups, and the three moisture permeable cups can be tested independently.
l  The system adopts an intermittent weighing method that meets the standard requirements, and ensures a constant humidity difference inside and outside the moisture permeable cup through the standard purge wind speed.
l  The device provides two quick calibration methods for standard film and standard weight to ensure the accuracy and versatility of the test data.
l  The equipment supports the test results comparison. The user sets the standard value and error range before the test starts. After the test is completed, the system automatically judges whether the test results are within the standard error range and intuitively informs the user.
l  Support Lystem TM laboratory data sharing system, test data and device information can be reported simply by setting and operation, and easy to realize centralized and systematic management of laboratory test data.
5 , the test process
(1) Three pieces of a sample having a diameter of 74 mm were cut out from the surface of the sample .
(2) The sample is separately clamped in three moisture permeable cups, and then placed on the moisture permeable cup holder inside the device, and the test chamber door is closed.
(3) Set the sample name, sample thickness, test temperature, test humidity and other parameters, click the " Start Test " option.
(4) After the test is over, the instrument automatically calculates and displays the test results.
6 , test results
The water vapor transmission rates tested in this paper were: 0.234 g/(m 2 ·24h) , 0.302 g/(m 2 · 24h) , 0.293 g/(m 2 · 24h) .
7 , conclusion
In order to avoid the occurrence of deliquescent and mildew in the tea, the manufacturer should use packaging materials with low water vapor transmission rate. The W3/031 water vapor transmission rate tester is a professional water vapor transmission rate for film testing. The test instrument has simple operation, high test accuracy and good repeatability, and can truly reflect the moisture resistance of the packaging material.
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