CO2 permeameter

CO2 permeameter

CarboPack BTCan be used to test the permeability of carbon dioxide, such as the permeation of carbon dioxide in carbonated beveragesPETBottle body or cork (natural or synthetic), Glass bottle lids for sparkling wine or beverages, etc.CarboPack BTtestCO TRIt is non-destructive and fast. Usually, a test only costs less than1Hours, unlike other conventional methods that require weeks or even months.

CarboPack BTIt can measure trace penetration through packaging materials (with better detection limits in the market), as well as visible leaks such as breakage or welding errors.

Using a non dispersive infrared gas sensor and a dual wavelength infrared detection subsystem, the sensitivity of * has been achieved through constant temperature control and pressure compensation. Due to this and the electronic board,CarboPack BTCan be tested at higher relative humidity valuesCO2TR(optional item)Through this method, we can measure and evaluate the effect of humidity on the carbon dioxide permeability of materials or coatings used in bottle production under conditions as close to reality as possible.

CarboPack BTEquipped with a heating and cooling control system that can verify the performance of the barrier layer as a function of temperature. All functions are controlled by software.

In today's plastic packaging application field, gas containing packaging has emerged as a rising force, gradually showing more functionality.

One form is modified atmosphere packaging, which involves filling a sealed package with gases such as CO2 and N2 to regulate the gas composition inside the package, thereby suppressing physical, chemical, and physiological reactions that can cause deterioration in the quality of the contents (especially food). CO2 is an important gas component in modified atmosphere packaging, and its prominent role is its efficient antibacterial effect. Due to the ability of CO2 to penetrate bacterial cells, it can cause a decrease in intracellular pH and enzyme activity, thus inhibiting cell proliferation. In addition, CO2 is low toxic and has little impact on food sensory quality, so it has antiseptic and mildew proof effects on fish, seafood, fresh fruits and vegetables, baked Dim sum, etc.

The second form is carbonated beverage packaging. Carbonated beverages are made by increasing pressure during processing to dissolve CO2 in sugar water. CO2 carbonates when it contacts with the liquid, producing sour taste, blending the flavor of the beverage and forming a stimulating taste, giving the carbonated beverage * a foam appearance. The carbonation of CO2 reduces the pH value of the liquid, creates an acidic environment, and is beneficial for inhibiting microbial growth, playing a role in antibacterial and anti-corrosion.

Gas loss mechanism and penetration testing methods

For the two types of products with gas packaging mentioned above, maintaining the amount of CO2 gas is a prerequisite for achieving their packaging function and product characteristics, which has important practical significance for the quality preservation and flavor preservation of the contents. But from a practical perspective, 'loss' is inevitable. According to years of research by Jinan Languang on the infiltration mechanism of packaging plastics and plastic containers, there are mainly two ways of loss:

1. Micro level - Penetration

For gas containing packaging, the concentration of CO2 inside the packaging is significantly higher than on the outside. Under the effect of the concentration difference, the gas on the high-pressure side will adsorb and dissolve onto the plastic material, where it will diffuse and desorb from the other side. This process is known as the permeation and loss of CO2. The penetration rate mainly depends on the barrier properties, thickness, and environmental temperature and humidity of the packaging plastic.

2. Macro level - Leakage

This mainly refers to the sealing of the packaging edge or bottle mouth. If the quality of the edge sealing is poor, the bottle cap is not tightened, or there are defects in the thread design of the bottle mouth and cap, resulting in poor sealing of the edge or bottle mouth, gas is easily leaked through the gaps.

At the macro level, leaks often exhibit rapid and significant loss characteristics, making them easy to observe and therefore easy to prevent and control. However, gas loss at the microscopic level is a slow and long-term process that is not easily detected, which is often an important cause of quality deterioration of the contents during their shelf life.

Therefore, for packaging suppliers, a product performance control system should be established to pre inspect the barrier properties of materials used for gas containing packaging, adjust the process in a timely manner, and provide packaging materials that meet the requirements of the user. For end users of packaging materials mainly in the form of gas containing packaging, the CO2 permeation performance of packaging materials, as well as the permeation barrier performance of other conventional gases such as N2, O2, and air, should be tested and studied, and included in the content quality control system to judge the applicability of the barrier performance of self-produced or supplied packaging materials, and also serve as an effective data source for evaluating and screening suppliers.

At present, the testing of CO2 permeability of plastic materials mainly refers to GB/T1038-2000 "Test Method for Gas Permeability of Plastic Film and Thin Film: Differential Pressure Method". The principle is to separate the low-pressure chamber from the high-pressure chamber using plastic film or thin sheet. The high-pressure chamber is filled with a test gas of about 105 Pa, and the volume of the low-pressure chamber is known. After sealing the sample, use a vacuum pump to draw the air inside the low-pressure chamber to near zero. By measuring the pressure increment △ p in the low-pressure chamber with a pressure gauge, the amount of gas that passes through the membrane (sheet) from the high-pressure chamber to the low-pressure chamber as a function of time can be determined, but the initial stage of gas permeation velocity changing with time should be excluded. The gas permeation rate is calculated according to the following formula:

Qg=(ΔP/Δt)×(T0/P0T)×(24/(P1-P2))

In the formula, Qg represents the gas permeability of the material, measured in cm3/m2 · d · Pa;

(Δ P/Δ t) - the arithmetic mean of the gas pressure changes in the low-pressure chamber per unit time during stable permeation, measured in Pa/h;

V - Low voltage chamber volume, in cm3;

S - the test area of the specimen, measured in square meters;

T - Test temperature, K;

P1-P2- pressure difference on both sides of the sample, in Pa;

T0- Temperature under standard conditions (273.15K);

P0- pressure under standard conditions (1.0133 × 105Pa).

Test Cases and Analysis

The author selected PP and PET materials of equal thickness and tested their CO2 and N2 permeation rates at different temperatures using a gas permeameter according to the above testing principles. On the one hand, the instrument's barrier testing method was visualized, and on the other hand, the differences in CO2 and N2 permeation rates of different materials, as well as the influence of temperature on them, were displayed. Taking this as an example, provide relevant method guidance for testing and research in this field for upstream and downstream enterprises of packaging materials.

The instrument used for testing is the VAC-V2 differential pressure gas permeameter from Jinan Languang. This equipment is specialized in testing the gas permeability, permeability coefficient, solubility coefficient, and diffusion coefficient of various thin film and sheet samples at various temperatures; Suitable for testing the permeability of various gases, such as O2, CO2, N2, helium, and air; The testing range is 0.05~50000cm3/(m2 · 24h · 0.1MPa), and the vacuum resolution can reach 0.1Pa; the temperature control range is 5 ℃~95 ℃, and the temperature control accuracy is ± 0.1 ℃; The humidity control range is 0% RH, 2% RH~98.5% RH, and 100% RH, with a humidity control accuracy of ± 1% RH. There are three independent test chambers that can simultaneously test three identical or different samples.

During testing, according to standards and instrument requirements, place the pre processed sample between the upper and lower testing chambers and clamp it tightly. Firstly, perform vacuum treatment on the low-pressure chamber (lower chamber), and then evacuate the entire system. When the specified vacuum degree is reached, close the lower chamber of the test, fill the high-pressure chamber (upper chamber) with a certain pressure of test gas, and ensure that a constant pressure difference (adjustable) is formed on both sides of the sample. In this way, gas will permeate from the high-pressure side to the low-pressure side under the action of pressure gradient. By monitoring and processing the pressure inside the low-pressure side, various barrier parameters of the tested sample can be obtained.

Jinan Languang Differential Pressure Gas Permeation Instrument

VAC-V2 differential pressure gas permeameter from Jinan Languang

Differential pressure method for thin film gas permeation testing

Differential pressure method for thin film gas permeation testing

The test results are shown in Table 1. From the material perspective, the N2 and CO2 permeability of PET film with the same area and thickness is significantly lower than that of PP film. From the perspective of permeation gas, the permeation of N2 by both materials is much lower than that of CO2, because the size and shape of gas molecules affect the diffusion of gas within the material. The size of molecules can be represented by the dynamic diameter of gas molecules, as shown in Table 2. In general, the smaller the dynamic diameter of a molecule, the easier it is to diffuse in the polymer.

CO2 permeameter