Basic performance testing of paper and board - quantification, tightness, bulk

This section introduces the basic performance tests of paper and paperboard, including test content such as basis weight, thickness, tightness, bulk, dimensional stability and uniformity .

Quantity, tightness, bulk

Quantitative paper and cardboard refers to the mass of paper and cardboard per square meter, in g/m2. Each kind of paper and cardboard has a certain quantitative standard. The physical properties of paper and cardboard, such as tensile strength, bursting strength, tear strength, etc., are all related to quantitative.

(1) Test equipment

Quantitative testing instruments include electronic balances and quadrant scales with a sensitivity of 0.0lg. Before the test, it is necessary to calibrate the instrument used to check the error between the standard value of the weight and the reading of the instrument. The difference should be within ±0.5%. When the mass changes by 0.2%, the electronic balance should respond.

(2) Test method

Before the test, samples should be taken according to the national standard GB 450, and the temperature and humidity pretreatment . Tested according to the national standard GB 451.2 "Determination of Quantitative Paper and Cardboard". Cut a 100mmX 100mm sample from the paper pattern, and the dimensional accuracy is 0.1mm. It can also cut 250mmX200mm samples, and the dimensional accuracy is 0.5mm. Calculate the area of the sample and take out the sample for weighing. If the paper sample is a coil paper with a width of less than 100mm, five samples with a length of 300mm should be cut according to the full width of the reel and weighed. At the same time, the long side and short side of the sample should be measured . 5mm, short side accuracy 0.1mm, and then calculate the area.

(3) calculation

① Quantification of paper and cardboard

Basic performance test of paper and paperboard - basis weight, tightness, bulk thickness with Figure 1

In the formula

G — quantitative, g/m2;

M - the mass of the sample stack, g;

A —area of sample stack, m2

a—the area of each sample, m2;

n - the number of layers of each stack of samples.

② Quantitative deviation of paper web

Basic performance test of paper and paperboard - basis weight, tightness, bulk thickness with Figure 2

In the formula

S ₁ —the deviation of paper web weight, %;

S2 _{— absolute deviation of}paper web weight, g/m2;

C _v —coefficient of variation of paper web weight, %;

Gmax — the maximum value of sample quantification, g/m2;

Gmin — the minimum value of sample quantification, g/m2;

G — the average value of sample weight, g/m2.

(4) tightness and bulk

Tightness refers to the mass of paper or cardboard per unit volume, and the unit is g/cm3. The tightness is calculated from the quantitative and thickness of paper or cardboard , namely:

Basic performance test of paper and paperboard - basis weight, tightness, bulk thickness with Figure 3

In the formula, D is tightness, g/cm3;

d - sample thickness, mm;

A certain amount of G , g/m2.

Bulk is the reciprocal of tightness, ie 1/D .

Tightness is directly proportional to bursting strength and tensile strength, and inversely proportional to tearing degree and air permeability.