2019-11-25 18:17
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Sanding Paper substrate is the earliest material used for coated abrasives, and it is also the most easily available material. The abrasive tape with paper as the base material has a certain proportion in the early abrasive belt grinding application. Because the surface of the paper base is flat and compact, it is easy to make fine-grained abrasive belts, and it is still used in some precision grinding. The base paper used to make the abrasive belt and the coated abrasive is made of a particularly strong and elastic fiber. It is characterized by a flat surface of the substrate, a small elongation, a simple substrate treatment, and a relatively low production cost.

The specifications of the base paper are many, and their quality is mainly indicated by the following physical and mechanical performance indicators. The requirements for the abrasive tape and the coated abrasive tools for the base paper are also expressed by these indicators.

1) Quantification.

Also known as quantitative weight, the weight per square meter of paper, in g/m2. This is an important indicator for the application of abrasive base paper, which greatly affects other physical and mechanical properties of the paper substrate. Therefore, the coated abrasive base paper is also classified by volume. Depending on the basis weight of the base paper, the coated abrasive base paper can be generally divided into several grades A, B, C, D, E, F, etc. The A type is the lightest and the F type is the heaviest. Sheet sandpaper, water sandpaper generally uses light paper. Fine-grained paper with soft paper, good softness; coarse-grained sandpaper and abrasive belt with heavy paper, high strength,

2) Thickness.

The thickness of the pattern directly measured under a certain pressure, expressed in millimeters. The measurement was carried out on a paper thickness gauge with a measurement area of (2 ± 0.2) cm 2 and a pressure of (10.0 ± 1.0) N/cm 2 . Generally, the thickness of the paper is large and the strength is high, but if the thickness is not appropriately increased in order to increase the strength, the softness of the base paper is lowered. The thickness of the coated abrasive paper is generally 0.2 to 0.4 mm.

3) Tightness.

The weight per cubic centimeter of base paper, in g/cm3. When the quantity is the same, the tightness is large, the thickness is small, the paper structure is compact, the strength is large, but it is easy to break; on the contrary, if the tightness is small, the thickness is large, the paper structure is loose, soft, but also brings the amount of glue absorbed. The big disadvantage is that the tightness of the coated abrasive should be moderate. Tightness is calculated by quantification and thickness. If the relationship is as follows:

Tightness D = quantitative W / (thickness d × 1000)

4) Vertical and horizontal.

The direction parallel to the paper machine is called the longitudinal direction, and the direction perpendicular to it is called the lateral direction. Since many indicators are divided into vertical and horizontal directions, the vertical and horizontal directions of the paper must be clarified before testing.

5) Front and back.

The base paper is divided into two surfaces. The side of the base paper attached to the copper mesh of the paper machine is called the reverse side or the mesh side, and the other side is called the front side or the smooth side.

6) Tensile strength.

Indicates the maximum tension (N) the paper can withstand. It can be represented in three forms:

Absolute Tension Resistance (N) - Represented by the resin directly measured on the tensile strength tester according to the width of the specimen specified in the base paper standard.

Crack length (m) - the length of the paper that breaks due to its own weight, which is actually calculated as follows.

Crack length (m) = absolute tensile strength of the sample (g) / [sample width (m) × sample quantitative (g / m2)]

The tensile strength per unit cross-section (N/cm2) is calculated as follows:

Tension resistance at the unit interface (N/cm2) = absolute tensile strength of the specimen (N) / cross-sectional area of the specimen (cm2)

The tensile strength of the base paper used for the coated abrasive is a very important mechanical property index, which is very important for production and use.

7) Elongation.

Indicates the length of the paper when it receives tension until it breaks, expressed as a percentage of the length of the base paper sample. In general, the elongation of the base paper is small.

8) Breaking resistance.

The uniform, increased maximum pressure that the finger paper can withstand per unit area. The unit is N/cm2, which is “determined bursting resistance”, referred to as bursting resistance; the relative wear resistance is the bursting resistance of paper with absolute wear resistance converted to a basis weight of 100g/cm2, and the calculation formula is:

Relative burst strength (N/cm2) = bursting strength of the sample × 100 / quantification of the sample

Breaking resistance is a reflection of strength and brittleness in the world. The base paper used in coated abrasives should pay sufficient attention to the bursting resistance.

9) Tearness.

It refers to the force required to tear a pre-cut paper to a certain length, expressed in g, which is also an important mechanical performance indicator reflecting the strength and brittleness of the paper.

10) Fold resistance.

The number of times the finger paper can withstand a 180° reciprocation at a certain tension (to the break). It reflects the brittleness of the paper, that is, the ability to resist flexing. It depends mainly on the strength of the fiber itself, and is also closely related to the thickness and tightness.

11) Moisture.

Humidity is also referred to as the ratio of the weight of the base paper sample dried at 100~106 °C to the constant weight and the original weight of the sample, expressed as a percentage.

12) Ash.

Refers to the ratio of the weight of the residue after burning of the paper to the absolute weight of the sample, expressed as a percentage.

13) Fiber ratio.

It refers to the choice of pulp raw materials during papermaking, and the ratio of mixing of several pulp raw materials is called fiber ratio. Different papers have different performance requirements and different fiber ratios. Coated abrasive base papers are generally 100% unbleached kraft pulp.

14) Interlayer strength.

The sample is cut open with a sharp knife in advance, and the two ends of the cut are clamped by a tension machine to accurately measure the tensile force in units of N/mm. It is an important indicator for the application of abrasive paper, especially abrasive tape.

15) Breathability.

The gas permeability meter is used to measure the time (min/ml) of a certain amount of air passing through the base paper sample, or the air volume (ml/min) of the sample passing through the sample for a certain period of time. The gas permeability reflects to some extent the tightness of the base paper fibers and the permeability of the base paper.

16) Water absorption.

The water absorption tester is used to measure the water absorption amount of the sample at a certain time and a certain area, and the unit is g/m2. It also reflects the tightness and permeability of the base paper to a certain extent.

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