II dr. III dr. II ing. III ing. Lucreþiu Pãtrăºcanu nr. Pentru abonamente, contactaþi redacþia revistei. When the mixture solution cooled down toambient temperature, NH4 2CO 3superfine powderwas added into above eco slim avests reales. After stirring foranoth er 2 hours, the bubbles in the blended solutionwere removed using vacuum pump.
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Secondly, afterdegassing, the resulting solution eco slim avests reales cast onto aplane glass model using a glass bar. The cast filmwas placed at ambient temperature for 2 minutes,and then immersed into water at room temperaturefor 3 minutes.
And then the model was taken out ofwater and dried in the air for about 5 hours. After steamtreatment, the films were stored in ventilation environmentfor at least one week before measurements. Membrane characters measurementsThe surface morphology of the films was investigatedusing a scanning electron microscope Hitachi, modelS at 20 kV with gold powder coating on the samples.
The cross-sectional fracture surfaces of thespecimen were obtained by cooling in liquid nitrogenfollowed by breaking. Differential scanning calorimetry DSC was carriedout using a F1. In the first scanning, the sample was kept at0°C for 10 minutes and heated to °C, then keptthis temperature for 10 minutes.
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In the second scanning,the sample was cool down to 0°C and the secondscan was recorded. Dimensions of the specimen used were mm ×× 28 mm by size. Measurements of five tests wereaveraged for each sample.
Bending length of the membrane was measuredaccording to ISO inclined plane method. Test procedures of abrasion resistance were carriedout with Rotary Platform Abraser Abrader.
The pressureloaded on specimen was g. Operating speedwas maintained at 3 rpm. The rotor revolutionwas recorded when the surface of the specimenappeared a hole.
Measurements of five tests wereaveraged for each specimen. The cupwas placed right side up and the tested side of membranecontacted with the air in the cup.
From figure 1 a, it can be seenthat membrane surface was smooth and compacted. Figure 1 b showed the sub-layer structure of the mem -brane. It was observed that in the sublayer round orhexagon pores as beehive stand side by side for acertain distribution. Observed from the cross sectiona b CFig. SEM photos of the membrane:a — surface × ; b — sub-layer × ; c — cross-section eco slim avests reales industria textila˘, vol.
The porous membrane was composed of two sections:compacted surface and porous sublayer.
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Thesmooth surface could provide the membrane withmost of strength and good protection to prevent leakingof working materials. Porous sublayer was thesupporting structure of the whole membrane and providedthe room which working materials filled with. Inthe sublayer PEG was divided into small unit by a lotof pores and lost the flowability even at high temperature. In addition, flexible hand of the membrane alsorooted in the porous sublayer structure.
The enthalpies of the positive process and thereverse process are close, and the temperaturedecides the direction, which indicates that the porousmembrane is a transition reversible latent storagematerial. Moisture regain of porous phase changemembrane with different PEG contentthe heating direction; but T on2, T end2and T p2diminishin the cooling direction.
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Moreover it is observed that there is a big differencein their transition states. Moisture regain of the membraneMoisture adsorption of the membrane resulted fromhydrophilic groups of PEG and surface absorption ofporous membrane. The relationship between moistureregain and PEG content is shown in figure 5. Itwas observed that the moisture regain almostincreased linearly with the increase of PEG content.
It was due to high content of PEG in the membrane. PEG occupied most of surface area and filled part ofpores. Thus moisture absorption was mainly relatedto hydrophilic groups of PEG. Tensile properties of the membraneMechanical properties of the kaiser pierdere în greutate sacramento with differentPEG content are presented in table 2.
It shows thatas PEG mass percentage increased, breakingstrength, breaking elongation and initial modulus ofthe membrane decreased obviously. The addition ofPEG blocked the aggregation of PU macromoleculeduring film formation and occupied some space, whichmade membrane structure became loose.
After mem -brane formation, when the membrane was drawn,the crystallization and adhesion of PEG wouldrestrain the extension of PU macromolecule, whichreduced macromolecule amounts loaded at the sametime and thus increased non-simultaneous breakageof the membrane. As a result, breaking strength andextension and initial modulus of the membranedecreased to some extent.
The tensile properties of the membraneformed of different DMF content are shown in table 3. It indicated that tensile strength, breaking elongationand initial modulus of the membrane decreased withthe increase of DMF content in solution.
The increaseof solvent weight ratio affected the aggregation ofPU macromolecule, and after DMF volatizing, biggerpores were formed in the film. As a result, the lateralbonding of the membrane was weakened and me -chanical properties were decreased.
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Therefore DMFcontent in film-forming solution should not be too high. Bending rigidity of the membraneBending length is an index of bending rigidity andthey are positive interrelated. As figure 6 showing,bending length of the membrane with different PEGcontent decreased gradually as testing temperatureincreased. As environment temperature increased, phase changematerial PEG became soft gradually until it changedto liquid state from solid state.
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Thus the change oftemperature produced huge effects on PEG morphologyand rigidity. Correspondingly membrane flexibilitydepended on environmental temperature largely.
Figure 6 also shows that the relationship betweenbending length and PEG content was complex anddepended on testing temperature largely. It can beobserved that membrane bending length increasedwith the increase of PEG percentage at 10°C, butdecreased at 50°C. It was mainly due to phasechange behavior of PEG. Bending length of the membrane underdifferent temperatureFig. The relationship between abrasion resistanceand PEG contentFig.
And thus eco slim avests reales lower temperature PEGcontent addition resulted in the increase of membranebending rigidity. However, when ambient temperaturereached above transit point about 30°C ,the whole membrane became very soft and was easyto bend.
While around transit point both porositystructure and phase change behavior of PEG playedimportant roles on bending rigidity of the membrane. Bending length of the membrane formed with f differentDMF content is shown in figure 7.
Obviously thebending length decreased with the increase of DMFcontent. The increase of solvent DMF resulted in theincrease of the porosity and the decrease of the initialmodulus of the membrane. Thus the bending rigid -ity and bending length of the membrane decreased. Abrasion resistance of the membraneAbrasion resistance measurement results of themembrane with different PEG content are shown infigure 8.
It is observed that the abrasion resistancedecreases as PEG content increases.
It is mainly due to the increase ofPEG content resulting in the dramatic reduction ofmechan ical properties including breaking strengthand elongation, initial modulus and lateral bondedstrength. Thus the surface layer of the film was wornout and tore more easily.
When PEG content reachedhigher percentage, PEG formed continuous phase inthe membrane, and thus slowed down the reductiontendency of modalități dovedite științifice de a arde grăsime resistance.
Figure 9 shows the effects of DMF content on abrasionproperties of the membrane. The results aresimilar to the effects of PEG content.
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The increase ofDMF content leads to the breakdown of mechanicalproperties. Moisture permeability of the membraneThe membrane is made of carrier material PU porousmembrane and work material PEG. The first hasmoisture permeability function through micro poreand the latter has moisture permeability functionthrough hydrophilic groups. Thus the membrane hasdual moisture permeability function.
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As table 4 showing, with the increase of PEG, moisturepermeability of the membrane increased gradually.