Oven-drying method: the Direct method

The oven-drying method adopts a system consisting mainly of a forced air drying chamber and a weighing device having a minimum sensitivity equal to ± 0.05% of the weight of the subsample.

By positioning the subsample of known weight (mainly set between 100 and 300 grams) in the aforesaid chamber, at a drying temperature equal to 105 ± 2 °C (with the exception of the silk samples being treated at 140 °C), it is dried until when the difference of weight between the results of two subsequent weighings, performed at a few minutes interval, is not higher than 0,05% of the subsample dry weight and as established for the single fibers type.

By comparing the weight of the sample before and after the drying, the moisture content absorbed by the fiber material is appreciated and the proportion of the dry mass of the whole product batch is calculated immediately, thus establishing the mass, through the specific conventional fiber regain (%), therefore is defined the commercial mass.

The trade in textile fiber materials with conditioned weight is not mandatory but it is an agreed opportunity between the parties and is useful especially if they are marketed with hygienic fibers of particular economic value. In fact, its consideration, in such cases, is established on the basis of the commercial mass, although the net weight is also indicated in the accounting documents.

The ovens used in the conditioning processes must be of a legal nature and subject to periodic check calibration as the humidity values thus detected clearly affect the price of the goods in the transactions.

Said this, instruments must have a capacity suitable for the weight of subsamples and of the tared can containing the fibers depending on their bulkyness too and must have a resolution of at least one hundredth of a gram, such that the slightest variations in weight are appreciated.

The drying ovens must also be placed in adequate environmental conditions, with particular attention to the temperature that, near the air inlet can become excessively high.



COMPARATIVE ANALYSES AND APPARELS SOLUTIONS


Since quite a long time, for the determination of the moisture content in textile materials are existing several solutions.

The question is:
What system should be used? It depends on the accuracy.

If only quick test needs to be done for getting a rough idea about the moisture content (MC%), then express testers can be used.

The Moisture Content (MC%) of textile fibres is one of the most important parameters.
It takes influence onto the processing behavior as well as on to the trading of the fibers especially.

Moisture on one hand is desired for the processing but not desired for the trading.

The prices for selling/purchasing fibers, for example Cotton material, are made on base of standard moisture content (around 7..7,5 %) or on base on dry sample material.

Anyway in both cases it is important to measure very accurate the moisture content.

Again the question is:
What system should be used then? It depends on the accuracy.

In case only of a small size of sample, then it should be measured to evaluate the moisture, then a high precision balance with infrared lamp is used although the risk to burn the fiber material is high and it could  cause an alteration of the original shape.
How does it works?
On the top of the weighing plate then is an infrared heating system located.
Then putting the sample on the weighing plate and start the measurement.
Then the moisture is going to evaporate and the loss of moisture is recorded too.

This time is the last:
What system should be used then? It depends on the accuracy.

The best solution for the accuracy of moisture content is the oven-drying method with suitable testing equipments:

A rapid drying oven is a testing equipment able to determine the moisture regain percentage in textile specimen within a very short time, with the biggest quantity of material and with the most precise results


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