Figure 1-4 Compression set of nitrile samples induced with chrome-plated pressure plates perASTM D395 to 20 % strain ( left and center ). Specimen thickness change was measured after 22hours at 125 ° F in a laboratory furnace ( right ).

spacer shims . Bolts were used to apply the compressive load to the platens . Once the samples were engaged in the compression rig the entire rig was placed in a 51.7 ° C ( 125 ° F ) furnace ( Blue M ) for 22 hours . Sample thickness was measured before and after compression set testing to compute changes in relaxed height and to determine the percent of plastic deformation to original compressive deformation ( Compression Set ) CB by :

Where to is the original sample thickness after the oil immersion conditions , but prior to compression set testing , ti is the final sample thickness after the compression set conditions , and tn is the spacer thickness .

Figure 1-5 to 1-8 present the results of testing done with different biodiesel blend levels . Figure 1- 5 shows the tensile strength results . Averages of three area measurements were used for each specimen . Results of tensile strength are reported as a function of the oil immersion

The Desmond • Albany , NY

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Shane Sweet Executive Director shane . sweet @ nypropane . com 802.558.6101

Amanda Stevens amanda . stevens @ nypropane . com 518.383.3823 www . nypropane . com protocol and do not illustrate a clear trend with biodiesel level . In all cases the elastomer easily retained greater than 60 % of the unexposed tensile strength . 1-10 Figure 1-6 shows the results for the hardness measurements . There is a slight trend toward greater hardness retention with increasing biodiesel level in the blend but these results also show no concern about biodiesel interaction .

Figures 1-9 through 1-12 present the results of the studies with B-100 with elevated acid number . Figure 1-9 shows the impact of elevated acid number on tensile strength . Using the criterion in UL 157 , a tensile strength of less than 10.5 MPa would be under the 60 % of the unexposed sample tensile strength . Samples exposed in biodiesel with a TAN of 2 or greater would not be considered an acceptable outcome .

As shown in Figure 1-10 , the impact of acid number on hardness is not very significant and a trend is not apparent . Figure 1-11 shows a clear increase in compression set with increasing acid number . UL 157 does not set a limit on either of these parameters , however . Figure 1-12 , volume swell shows a strong increase in this parameter with acid number . At an acid number of 2 the limit of 25 % swell in UL 157 has been reached .

DISCUSSION

Conventional elastomer impact testing under the UL 157 procedure is by soaking the fuel for a total of 70 hours at room temperature (~ 73 ° F ). For this testing , much higher temperatures ( 125 ° F ) and much longer soak times ( 670 hours ) were used . For biodiesel / heating oil blends meeting current ASTM standards the results presented above show no significant changes in the properties measured with biodiesel blend levels to 100 % for the specific elastomer evaluated relative to the base fuel oil . This elastomer , which is used in current and legacy oil burner pump shaft seals , was selected as a critically important seal component representative of elastomers generally used in oil-fired heating systems .

The results with biodiesel / heating oil blends meeting today ’ s ASTM standards , do not provide a cause for concern about biodiesel use in these systems . With the

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