CS247823B1 - Microprobe for plastics thermal testing - Google Patents

Abstract

The invention relates to a chemical apparatus laboratories for rapid implementation plastic semimicroanalysis wt. The device is made of hollow metal a needle with three electric wires in the center conductors firmly connected to the tip needles, for example by welding, two of them j "are connected on the opposite side via the controller voltage to the source and remaining to form together with a thermoelectric needle connected to a millivolt meter.

Description

The present invention relates to a microprocessor for the thermal testing of plastics, which makes it possible to determine, from an unknown plastic, the approximate softening or melting point, the degradation temperature and the type of plastic from the degradation products.

So far, the detection of presence, respectively. Type of plastic in different apparatus and equipment carried out by analytical methods after sampling. This method is always largely destructive. In addition, complex devices capable of processing small quantities of material are known, but their operation is economically highly demanding.

These disadvantages are overcome by the hollow needle micro-probe for thermal testing of plastics according to the invention. SUMMARY OF THE INVENTION The hollow center of the needle comprises three electrical conductors which are rigidly conductively connected to the needle tip, for example by welding, two of these electrical conductors being connected via a controller to a voltage source and the third electrical conductor forming a thermocouple with the needle. connected to the millivoltmeter.

Advantageously, the lower portion of the hollow needle is widened to accommodate the needle in the holder and filled with a high temperature sealant that protects the conductors from overheating while firmly anchoring them in the needle, thereby reducing the risk of oxide rubbing on the conductor surface and shorting between the conductors.

In a preferred embodiment of the invention, the electrical conductors are formed from a constant, since the oxide formed on the surface of the conductors insulates them against the needle walls and the thermocouple formed has optimal parameters.

The micro-probe according to the invention allows a rapid evaluation of an unknown plastic, namely whether it is a thermoplastic or a thermoset, a softening point or a soft spot. the melting temperature, the temperature at which the plastic degrades, and the properties of the degradation products can be judged by the type of plastic. The probe is portable, allows testing without sampling, ie non-destructively, and economically inexpensive.

BRIEF DESCRIPTION OF THE DRAWINGS The invention is explained in more detail below by way of example with reference to the accompanying drawing, in which: FIG.

The micro probe consists of a hollow steel needle 8 which is expanded at one end into a carrier part 2. The carrier part 2 of the steel needle 4 is filled with a high-temperature sealant 4 and serves to clamp the steel needle 4 in a holder (not shown). Three electric conductors 5, 8, 8 pass through the hollow center of the steel jejle. In the described embodiment, the electrical conductors 5, 6, 6 are made of constantane and from the walls of the steel needle and are not insulated by an oxide layer on their surface.

The electrical conductors 6, 7, 7 are welded to the tip 6 of the steel needle 6. Two of the electrical conductors 5 and 7 are connected via a regulator to a voltage source and serve to heat the heating of the steel needle tip 6. The electric conductor 6 forms, together with a steel needle 4, a Fe-Ko thermocouple connected to a millivoltmeter 6 whose scale is calibrated in ° C within the appropriate range.

FIG. 2 is a block diagram of a micro probe electrical system.

The voltage source 8 for heating the steel needle 8 provides an alternating voltage of the order of volts, which is led through the regulator 10 to the electrical conductors 5, 6 in the steel needle. The regulator 60 is controlled by a signal from a DC millivoltmeter 9 which is connected to a Fe-Ko thermocouple, ie, to the weld at the tip of the steel needle 6. A transformer is used as the voltage source 6 in the particular embodiment described, and a relay controller 10 is used.

The microprocessor according to the invention operates as follows: after connecting the probe to a voltage source, the probe tip 3 is brought into contact with the test plastic and the temperature of the tip 3 is gradually raised until the mass melts in its vicinity.

On the DC millivolt meter 3, calibrated in ° C, the approximate softening point is read. melting plastic. Then, a small amount of plastic is picked up on the tip of the steel needle and the temperature of the tip 3 rises sharply. The result of the thermal reaction of the plastic is visually determined and the type of plastic is judged from its properties.

The invention can be used in laboratories of industrial companies for rapid preliminary orientation semi-microanalysis of plastics, possibly also as a thermometer.

Claims (3)

Microscope for thermally testing plastics, consisting of a hollow metal needle, characterized in that the hollow center of the needle (1) comprises three electrical conductors (5, 6, 7) which are rigidly conductively connected, eg by welding, to the tip (3). (needles), wherein two of these electrical conductors (5, 7) are connected to a power supply (8) via a regulator (9) and one electrical conductor (6) forms together with a needle (1) a thermocouple connected to a millivoltmeter (9) /. 2. The micro probe according to claim 1, characterized in that the lower carrier part (2) of the needle (1) is expanded and filled with a high-temperature sealant (4). 3. The micro-probe according to claim 1 or 2, characterized in that the electrical conductors (5, 6, 7) are formed of a constantane.