热塑性塑料中流变性能检测方案(流变仪)

智能文字提取功能测试中

Ansprechpartner： Dr. Frank Clemens， Telefon： +41 (0)1 823 48 21；E-mail： frank.clemens@empa.ch Preparation and RheologicalInvestigations on ThermoplasticZrO2 Pastes F. Clemens， R. Corbari， T. Graule； EMPA， Section High Performance Ceramics，CH-8600 Dubendorf， Switzerland Introduction Thin ceramic tubes with a wall thickness less than300 um are interesting for various applications， forexample as protective layer for a plastic shaft， filterstructures， thermowells， and heat exchangers. Ad-vantages are higher wear and lower filtration resist-ance， or faster heat transfer. For producing such tubes， water based duroplas-tic or thermoplastic binder systems can be used.The main problem with water-based binders is thecollapsing of the tubes after extrusion. Extruded duroplastic compounds cannot be recy-cled whereas thermoplastic binders can be recy-cled and do not collapse after extrusion. To optimize the ceramic thermoplastic compoundfor the tube production， ZrO2 powder， Hostamontand polyethylene were mixed in different percent-age by volume. ExperimentalProcedure First， fine zirconia powder (TZ-3YE， Tosoh EuropeB.V.) was kneaded in a torque rheometer mixer(Rheomix 600， Gebr. Haake GmbH) with Hostamont(EK 583， Clariant GmbH) and LDPE (Elf-AtochemAG). After kneading， the torque was measuredthree times with 5 rpm， at 160℃. The material wasfed in a screw extruder (Rheomex 202， Gebr.Haake) and characterized by capillary rheometry at160°C. Tubes were produced with the screw extru-der and a die (da =6.7 mm，dj=6.2mm). Figure 1 shows zirconia powder， plastic compoundand a sintered ceramic tube. Fig. 1： Material in different process stages CompoundPreparation Figure 2 shows the results of the kneading processfor different compounds. Rising the amount of ZrO2 powder， the torqueincreases， and getting a steady state takes alonger time. Table 1 presents the color and the consistencyafter kneading. In the compounds with more than50 vol.-% ZrO2 powder the color changed aftermixing because of abrasion. vol.-%ZrO2 color cold consistency 45 beige plastic paste 47 beige plastic paste 50 beige plastic granulate 52 grey plastic granulate 54 grey plastic granulate Tab. 1：Compound properties after kneading Torque RheometerTest Internal mixers used by industry as well as torquerheometers are designed to create as much turbu-lent flow as possible to provide optimum mixing forheterogeneous compounds. Torque rheometersare not designed to define the absolute viscosity ofthe compounds， but it makes a good sense toapply a certain rotor speed and to measure thereactionary torque on the rotors. Two batches for alldifferent compounds were kneaded. After knead-ing， the torque was measured three times with 5rpm， at 160 C， for all compounds. For a stableprocess the torque should always be the same.Figure 3 shows the result of the test. Fig. 3： Torque for different compounds (5 rpm， 160℃) Fig. 4： Comparison of the coefficient of variation The lowest coefficient of variation between twocharges was reached with a compound of 50 vol.-%ZrO2 powder. CapillaryRheometry Test For heterogeneous material it is very difficult todefine the absolute viscosity， because the homo-geneity can change during the test. Therefore， onlythe pressure between the different compounds iscompared. All compounds， except 54 vol.-% ZrO2，could be extruded. Figure 5 shows the pressureduring the tests with the different compounds. Fig. 5： Pressure for different compounds during the test(20 rpm，at 160 ℃) The compound with 50 vol.-% ZrO2 is the mosthomogenous material. Tube Production Tubes were produced with all compounds. Table 2shows some visual properties seen after extrusion. vol.-%Zro2 roundness Tab. 2： Visual properties after extrusion In Figure 6 sintered tubes with a wall thickness of200 pm are depict. Fig.6： Tubes after sintering Conclusions With the compound having 50 vol.-% ZrO2 the bestresults concerning homogeneity of pastes and ex-trudability were reached. Table 3 shows the results. pressure torque rheometer testcapillary rheometry testtube production reproducible batches stable pressure beige color stable process Tab. 3： Results of compound 50 vol.-% ZrO2