What are the test requirements for printing paper standards?

Different kinds of paper need to have performance indexes suitable for their main uses. According to different uses, the following performances are tested by special instruments according to standards.

Physical performance index

① Quantification: weight per square meter in g/m2. For example, the basis weight of paper for cultural printing is generally 32 ~ 80g/m2, and that of paperboard is generally 200 ~ 400g/m2.

② Thickness: the thickness measured directly between two measuring plates under the pressure of 100kPa, in millimeters (mm). ..

③ compactness: indicates the compactness of paper structure, and the weight of paper per cubic centimeter is expressed in g/cm3. The same amount of paper, the paper with large thickness is loose.

④ Porosity and air permeability: Generally, paper contains 70% porosity. Air permeability refers to the amount of air per minute or the time for a certain amount of air to penetrate a certain area of paper under a certain vacuum degree, which is expressed in ml/min or s/ 100ml respectively.

⑤ Shrinkage rate: the relative change of paper size after soaking in water or humidifying or dehumidifying at different temperatures, expressed as the percentage increase or decrease of the size relative to the original sample size. Offset printing paper requires higher expansion rate.

⑥ Strength: Some specific values reflected when the paper is subjected to external force and reaches the failure point. Mainly including tensile strength, elongation at break, bursting strength, folding endurance, tear strength and rigidity. Various strength indexes are particularly important for packaging paper.

Optical performance index

(1) whiteness: the reflectivity of white or nearly white paper surface to blue light, expressed as a percentage relative to the reflectivity of standard magnesium oxide board.

(2) Opacity: It is expressed as the percentage of the reflectivity of a single sample on a "completely absorbed" black pad and the reflectivity of several completely opaque samples.

③ Transparency: the degree to which light passes through the paper. It is expressed by the maximum number of layers of ink lines that the sample can see clearly. Optical performance index is very important for printing paper and tracing.

Chemical property index

① Moisture: The paper contains the weight of water that can evaporate at 100 ~ 105℃, expressed as a percentage of the paper weight.

(2) Ash: the percentage of the weight of burnt paper residue in the weight of paper sample.

(3) pH value: the pH value of the water extract of the paper sample after soaking in distilled water at 95 ~ 100℃ 1 hour. These chemical indexes have great influence on the printing adaptability (stability in high-speed printing environment) of paper.

Surface performance

① Sizing degree (water resistance): It is very important for writing paper that the surface of paper can prevent ink from permeating and diffusing during writing. Dip a duckbill pen in special ink and draw a line on the paper, which is expressed by the maximum width (mm) of the non-diffusion and non-permeability line.

② Smoothness: The time required for a certain volume of air to pass through the gap between the sample surface and the glass surface under a certain vacuum and pressure, expressed in seconds.

③ Surface strength: In order to prevent paper from falling off and pasting, offset printing paper requires good surface strength. The number of wax rod stages from pressing paper with wax rod to drawing fiber can also be expressed by measuring drawing speed with printing instrument. What drawing paper and tracing paper tested was its friction resistance, and it was a test of paper surface tissue bonding strength.