Inspection method of plaster

The quality requirements of the plaster: the plaster should be oily and delicate, bright, moderately old, spread evenly, without fins, and can be pasted on the skin without moving after heating

(1) Softening point inspection

1.

(1) The method of measuring the softening point of plaster is used to measure the temperature of the plaster when it is heated and softened under specified conditions, that is, the temperature at which the plaster drops 25mm due to heat as measured according to the following method

(2) This method is applicable to the softening point determination of black plaster and white plaster

2.

(1) Apparatus: Softening point tester

(2) Preparation of the sample ring: take the test sample and spread it in a constant temperature box at about 75℃ and soften it by slight heat (about 1 to 3 minutes), take it out, scrape off the paste, weigh 2 aliquots, 1.

(3) Softening point measurement: According to the plaster softening point measurement method (General Rule 2102), place the two sample rings in the support plate ring on the support, install the steel ball positioner, and install the support in the beaker containing water Place the two steel balls at the bottom of the beaker at the same time, and make the liquid level flush with the circular marking on the support pillar.

(4) Comparison: If the difference between the two temperatures is greater than or equal to 1.

3.

(1) The glycerin coated on the tin foil paper should not see any droplets, and the excess part should be wiped off with cotton or filter paper

(2) In order to avoid bubbles in the paste in the sample ring during the melting process, there should be a gap between the filled paste and the inner wall of the sample ring

(3) The paste with a higher softening point is not easy to soften under the conditions of sample ring preparation, and the softening temperature or the softening time can be appropriately increased

(4) The heating rate has a great influence on the test results and must be strictly controlled

(5) After the test, the remaining paste on the steel ball, sample ring and support can be ultrasonically cleaned with turpentine or gasoline and dried in time for later use

4.

5.
Records and calculations

(1) Record the model of the instrument and the sampling amount of the paste
.

(2) Record the two measured temperatures and their difference and calculate the average value
.

(2) Weight difference check

1.
Brief description This method is applicable to the weight difference inspection of plaster.
In the production of plaster, due to the flow of plaster, spreading and other processes, as well as equipment and operation, etc.
, the weight difference of plaster may be affected
.
The purpose of this inspection is to control the consistency of the weight of each sheet and ensure the accuracy of the dosage
.

2.
Method of operation

(1) Take 5 test samples and weigh the total weight of each
.

(2) Measure the area of ​​the back of each piece, cut out the unit area (cm²) of the back of the mount, weigh it, and calculate the weight of the back of the mount
.
The total weight of each sheet minus the weight of the back mounted is the weight of the plaster
.

3.
Matters needing attention

(1) During operation, avoid direct contact with the paste surface with your hands
.

(2) The test products should be numbered separately to ensure that the total weight of each piece corresponds to the area of ​​the back of the mount
.

(3) When the shape of the mounting back is irregular, the test product can be processed into a regular shape before weighing the total weight, but the loss of paste should be avoided
.

4.
Results and Judgment Take 5 test samples, according to the limits specified in Table 15-21, the weight of each plaster is compared with the labeled weight, and none of them exceeds the weight difference limit, and it should be judged as conforming to the regulations
.
If the weight difference limit is exceeded, it will be judged as non-compliance
.

Table 15-21 Examination of plaster weight difference limit

5.
Records and calculations

(1) Record the model of the analytical balance
.

(2) Record the total weight of each plaster (mounting back + plaster weight) and the backing area of ​​each piece of plaster to be tested
.

(3) Record the unit area and weight of the cut back
.

(4) According to the weight of the unit mounted back and the area of ​​the mounted back of each test product, the weight of the mounted back is calculated, and the total weight minus the weight of the mounted back is the plaster weight
.

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