PN-Ⅱ Flat Viscosity Instrument Instruction Manual

I. Overview:

The parallel (row) plate viscometer is mainly used to measure the flow characteristics of ink. This is an instrument based on the principle of ink flow between two parallel plates.

A certain amount of ink (0.5 cm3) is placed between two parallel plates placed horizontally, so that the upper plate (115 grams, made of transparent material) with a certain mass falls freely on a fixed height horizontally and presses on the ink On, the ink spreads outward, and the relationship between the spreading diameter and time is measured until the maximum diameter at which the ink no longer spreads. Taking the logarithm of time t lg t as the abscissa and the spreading diameter d as the ordinate, a characteristic curve representing the ink flow characteristics can be obtained to a certain extent. The surface of the lower plate is engraved with many circles of different diameters, allowing the ink spreading to be observed and recorded. Usually read at 10 seconds, 60 seconds and 100 seconds where the edge of the ink is - the number of turns, and the maximum diameter at which the ink is no longer spreading.

Four parameters of the ink can be measured with a parallel plate viscometer, namely apparent viscosity, yield value, slope and intercept.

1. Apparent viscosity

PN-Ⅱ Plate Viscometer Instruction Manual with Figure 1

In the formula: η—apparent viscosity (Pascal seconds)

t — time of measurement (seconds)

r — radius of spread at time t (cm)

s — the slope of the characteristic curve, which is equal to the difference between the spread diameter (mm) at 100 seconds and 10 seconds

2. Yield value

The pressure on the unit area of the ink between the two plates decreases with time (because the weight of the upper plate is fixed, and the area of the ink increases with time), when the shear stress decreases to be equal to the yield stress of the ink, the ink will no longer spread , the spreading diameter of the ink reaches the maximum. It can be seen that there is a functional relationship between the yield stress S0 of the ink and the maximum spreading diameter dm of the ink measured by a flat viscometer. The value of yield stress can be obtained from the formula of rheological theory

PN-Ⅱ Plate Viscometer Instruction Manual with Figure 2

In the formula: S0 - Yield stress (N/mm2)

dm — ink maximum spread diameter (cm)

But usually its value is not calculated, and its yield value is expressed by the maximum diameter dm. There is also a practice of using the spreading diameter at 30 minutes as the maximum spreading diameter.

3. Slope and Intercept

The slope is a characteristic parameter representing the ink drawing length. The bigger the slope, the longer the ink thread, and vice versa. The intercept is related to the concentration of the ink, the larger the intercept, the thinner (softer) the ink, and vice versa, the thicker (harder) the ink.

There is a linear relationship between the ink spread diameter d measured by a flat viscometer and the logarithm of time lg t, and the slope and intercept of the straight line can be obtained:

PN-Ⅱ Plate Viscometer Instruction Manual with Figure 3

In the formula: s—slope

I—intercept (mm)

d10—ink spreading diameter at 10 seconds (mm)

d100—Ink spreading diameter at 100 seconds (mm)

The spread diameter d60 at 60 seconds is called the fluidity value.

2. Operation and use (see outline drawing for details)

1. Clean the ink filling hole and the upper and lower parallel plates (1 and 12) of the instrument and make them dry.

2. Adjust the three adjustment screws (8), and confirm the level of the instrument by the level bubble (9).

3. Properly rotate the guide post (2) to raise the upper parallel plate (1) and fix it, and pull the handle (7).

4. Put the ink into the ink filling hole in the middle of the lower parallel plate, the ink surface is even with the surface of the lower parallel plate, and be careful not to produce air bubbles and gaps. The upper parallel plate can be taken off when loading ink, and then put back on the guide post after being installed.

5. Push the handle (7) upwards and start the chronograph at the same time. The ink is pushed to the center of the lower parallel plate, and the upper parallel plate will fall horizontally at the same time.

6. Read the spread diameter (in millimeters) of the ink at 10 seconds, 60 seconds, and 100 seconds.

7. Read the maximum spread diameter of the ink in millimeters.

8. Calculate according to the above formula, get the measurement data and make a record.

9. Precautions: The experiment should be carried out under constant temperature conditions, the temperature is 25°C±1°C, and the humidity is 65%±5%.

3. Use and maintenance

After the instrument is used, it is cleaned and placed in the box to place it securely without bumping. The instrument should be placed upright, and the upper parallel plate (plexiglass plate) is placed on the lower parallel plate to prevent deformation. The upper parallel plate should be replaced if it is uneven for a long time or the weight is insufficient (115g±2g).

If it is found that the upper end surface of the central shaft (4) is not on the same plane as the lower parallel plate (12) after it bounces up, it should be adjusted. Unscrew the small column (5) and insert it into the hole at the lower end of the central shaft; loosen the set screw of the adjusting nut (6), and adjust the adjusting nut properly so that the upper end of the central shaft and the lower parallel plate are on the same plane; lock Tighten the set screw of the adjusting nut and put the column back in place.