Presentation on theme: "DSC GELATION MEASUREMENT : INFLUENCE OF PIPE FORMULATION ON RESULT"— Presentation transcript:
1 DSC GELATION MEASUREMENT : INFLUENCE OF PIPE FORMULATION ON RESULT Joël FumireResearch & Technology SBU VinylsSão Paulo, 2005
2 Introduction Considering the fact that … The level of gelation of PVC determines the mechanical properties of the finished itemThe level of gelation has a significant influence on subsequent processing (biorientation or corrugation)A few methods exist since a long time : MCT, SEM homogeneity, short die melt rheology, etc… none of them was considered as totally satisfactory.
3 Introduction Considering the fact that … The measurement by DSC method seems to realise a good compromise between accuracy, universal application and costBut : some authors found limitations to the application of the method related to the composition of the itemTHIS IS THE REASON FOR OUR INVESTIGATION
4 DSC measurement Apparatus : DSC TA 2920 from TA Instruments Operating instruction : 20 mg of sample in Al capsule,Heating speed : 20°K/min measurement range : 50 to 220 °C (conventionnally)
5 DSC measurementEndotherm A is the endotherm after Tg and up to the minimum at Tm (processing temperature)Endotherm B is taken from this Tm up to 220 °C (conventionnaly)Gelation level is calculated as : G = A / (A + B)mWDSC3.504.004.505.005.506.006.507.007.50Heat FlowBATgB-onsetA-onset30507090110130150170190210230Temperature
6 DSC measurement This method is not yet an international standard Standardisation group ISO TC138/SC5/WG2 is working on this topic with designation : ISO 18373The operation instruction adopted in this work is close to the existing draft
7 Parameters The main parameters investigated are : Type of stabilisation (Pb, Ca-Zn, Sn)Amount of fillerPresence of impact modifierLevel of lubricant
8 The main target is not : The main target is : Parameters to assess the effect of additives to promote gelationThe main target is :To check if some additives affect the DSC thermogram (shape or amplitute of endotherm)
9 Evolution of gelationGelation as measured by the DSC method (transformation of crystallites) appears rather late compared to a standard plastograph gelation test.Degree of gelation versus plasticising time10203040506070246812Time (min)Torque (Nm)60%55%
10 Sample preparationThe formulation is of the pipe-type, i.e. low level of additives but highly lubricated and the samples are gelified on a 2-roll millTable 112345678PVC K66100Solid tin one-packLead one-pack2.4Ca-Zn one-pack2.8Liquid tin stab.0.8Internal lubricant0.30.6LubricantCC filler1530Acryl Impact modif.TiO2 pigment0.25C pigment0.025CharacteristicLeadAcryl.Ca-Zn réf.lubricantfiller 15filler 30Liqu-TinTin-O.P.
11 Parameters (1st serie) Was milled at 180°C DSC -Tm140150160170180190200LeadAcryl.Ca-Znréf.lubricantfiller 15filler 30Liqu-TinTin-O.P.Effect of formulation on gelation level40%50%60%70%80%90%LeadAcryl.Ca-Zn réf.lubricantfiller 15filler 30Liqu-TinTin-O.P.DSC - Gelation level
12 Sample preparation Table 2 PVC Solid Tin O.P. Lead stab. Ca-Zn stab. CharacteristicTable 2PVCSolid Tin O.P.Lead stab.Ca-Zn stab.Liqu. TinInt. Lubr.Lubric.CC fillerCC coarse fillerPrecip. Fillerpigment11002.40.630.250.0252.80.3645728Leadfiller 6intern.coarsefillerPrecip.CCTin OP.tin+coarse f.
13 Parameters (2nd serie) All milled at 180°C Tm Gelation 140 150 160 170 190200PbFiller 6Intern. LubricCoarse fillerPCCTintin+c.f.All milled at 180°C40%50%60%70%80%90%GelationPbFiller 6Intern. LubricCoarse fillerPCCTintin+c.f.
14 ParametersThe variants of additives did generally not introduce a different shape of endothermOnly the ox-PE wax (lubricant) introduced an additional peak at 130 °C
15 Parameters Relation between B onset and gelation 100%2nd seriesR² =90%80%70%60%50%40%170175180185190195200B onset (°C)
16 ParametersThe processing temperaure can be checked with good accuracy but on these small machines this value is not totally correlated with the gelation levelThe shape of the endotherm was generally not affected by the composition (except by PE-wax)The sample with Pb stabilisation shows higher endotherms than the averageFor the sample with modifier and highly lubricated the energy/g of the endotherm was lower than the average
17 Elongation at rupture measured at 100°C in a tensile test Alternative methodAnother method was extensively used within our company to assess the level of gelation of window profiles :Elongation at rupture measured at 100°C in a tensile testElongations measured are in the range 200% (bad gelation) to 300% (good gelation) or higher (too strong gelation)
18 Alternative method Correlation is rather satisfactory DSC could lead to a lack of precision in high gelationsElongation at 100°C is also a precise method but the measurement is more labor intensive and equipment is more expensive.420y = e0.0147x370R² =320270220170120405060708090100
19 ConclusionsNormal levels of additives have no adverse affects on the measurement with this standard procedure (even with high levels of fillers)In some cases, the processing temperature is not a reliable way of expressing the gelation levelThe method is correctly correlated with other methods of assessing the gelation levelThe method appears to be enough robust to be used as quality control of extrusion
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