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Foaming polyolefi ns | technical paper


Table 1: The DOE set-up Name


Material Cell-Stabilizer


Stabilisation level Nucleating agent Isobutane


Abbreviation Mat


Stab stlev Nuc Iso


Unit


Type


% % %


grouped closely around the line and spread equally over the whole range. Contour plots give a graphical overview of the


studied response as a function of the variables. Figures 6, 7 and 8 are contour plots visualizing the behaviour of density, corrugation and cell-size of the experimental foam-sheets.


Densities achievable with LDPE 2202UMS can be


lower than the densities obtained using a more typical PE grade, however the grade is more sensitive to parameter settings. Model inaccuracy and less perfect laboratory settings give values differing from practical achievements.


Figure 4: Observed vs predicted plot and coeffi cient plot of the property density showing the relative contributions of each factor including interactions


Qualitative Qualitative Quantitative Quantitative Quantitative


Use


Controlled Constant Controlled Controlled Controlled


Settings


2102TX00; 2202UMS Stearamide 1 to 3


0,5 to 4 6 to 13


Table 2: Statistical key fi gures for density, number of waves and cell size R2 R2 Adj. Q2 RSD N DF 0.94 0.92 0.80 0.78 0.83 0.80


Log (density t0 waves


cell size )


0.89 0.049 0.71 4.02 0.76 0.35


This model shows the UMS grade to be better performing in terms of corrugation with fewer waves. The total area where wave-less sheets can be produced is larger. Also here model inaccuracy needs to be taken into account, as with the normal grade a few spots without waves could also be produced.


32 24 32 27 32 27


Figure 5: Coeffi cient plot for cell size and waves showing the relative contributions of each factor including interactions


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January 2013 | COMPOUNDING WORLD 47





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