the grease based on a polymethylethylsiloxane fluid with a yield point of 1600 Pa at 20~ (determined in K-2 apparatus), we observed a sharper change in the flow point than in the case of greases based on the chlorinated organosilicon fluid or the perfluoropolyether, with respective yield pints of 110 and 90 Pa. This means that the flow point is influenced by the type Of dispersion medium and also by the rheologicalproperties of the grease; this is important in evaluating the rheological properties of greases at low temperatures by means of thermomechanical methods of analysis.
TEMPERATUREDEPENDENCE OF DISSIPATIVE PROPERTIES OF ASPHALTS V. I. Khrapko, A. N. Bodan, and O. M. Taranenko
UDC 665.775:628.517.4:534.883.5
The use of asphalts in damping (sound-deadening) metal surfaces is based on the property of viscoelastic materials whereby they absorb mechanical vibrations at temperatures above the glass transition temperature [i]. It has been established that asphalt, when it is present as the binder in a sound-deadening composition, absorbs up to 50% of the vibrational energy [2], the level of absorption depending on the vibrational frequency [3]. The temperature dependence of the dissipative properties of asphalts has not been studied previously. Because of the need for reducing the vibration of surfaces at temperatures that may vary from -60 ~ to +90~ a study has been made of the damping capability of asphaltic materials within this range of temperatures. The characteristics of the asphalts that were investigated are shown in Table I. Samples i, 4 and 8-11 were obtained by oxidation of vacuum resids, samples 2 and 3 by vacuum distillation, and samples 5-7 by compounding. The dissipative properties were rated on the basis of the mechanical vibration loss factor n (mechanical loss angle tangent), which was determined from the width of the resonance curve [4] in an acoustic unit with a heating and cooling chamber that could be regulated for operation at temperatures from -60 ~ to +90 ~ Each asphalt sample, in the heated form, was applied to a 250 • 15 • i mmsteel plate in an amount of 30% of the weight of the plate, for a length of 200 ~ ; this gave an asphalt layer TABLE 1 Needle .... penetra!Temperature "o~ ,
Sample
NO.
Asphalt grade
sol- break~ten- ing m= ling point ~ o ~point ~ ~]
~,
-,4
u
.,4~.
o%
I(R&B)
Paving asphalts (GOST* 22245-76) 1 BND .-130/200 2 BN-130/200 8 BN-~O/90 4 BND-60/90
39 43 46 48
--23 --17
--8 --22
262 268 307 249
192 143 61 88
46 22 9 29
65 994 96 I015 100. 1012 100 1005
Structural asphalts (GOST* 6617-76) 5 6 7 8 9 I0 11
BN -70/30
BN-70/30 BNI-90/10 BN:-90/10 BN-90/10 BN-90/10
76 82 93 93 103 103
--21 --23 --3 -[-4 -}-7 -~II
.285 258 242 280 270 272
36 36 16 7 6 5
TU 38 UkrSSR% 201-193-78 Asphalt/tar 136 -[-23 276 2 sottening agent
8 7 4 " ----
--
993
3,2 3,3 1,0 1,5 1,5 1,0
1020 1013 1024 1022 1028
0
1033
*All Union State Standard. % Specification of the Ukranian SSR. All-Union Scientific-Research and Design Institute of the Petroleum Refining and Petro--/chemical Industry (VNllPKneftekhim). Translated from Khimiya i Tekhnologiya Topliv i Masel, No. 12, pp. 22-24, December, 1985. 0009-3092/85/1112-O635509.50
9 1986 Plenum Publishing Corporation
635
0,80
-
~
,,
g~
o,zo
=
71,
' I #:.,,.1/)<
:4'7Y_,0 .! }o'!0 o %~
Fig.
1.
Loss factor
n as a function
of
temperature t for structural asphalts. Continuous curves are for 1000 Hz, d~shed curves for 150 Hz. Curve numbers correspond to sample numbers in Tables 1 and 2. TABLE 2 --
__.. I_____Glas------~T
Acoustic indexes inte
Sa~ p le
tlon temperatur.e (tD,
No. -o
--55
al of
~ tional iloss iature .~ temperatures (t,--tl). I fre- Itac- l?f max-] of effective ~ [ quency, I n'~ I i mum I damping I dz ~ ' [ " Id~P - ] (~ ~_ o.o5),
~
150 1000 150 1000 150 1500
oC
0,085 0,26 0,21 0,12 0,54
--4 from--25to 10 + 3 from--40 to 12 +10 from--50 to 26 +4 from--28to 10 +18 from--6 to 35 +22 from--lO to 40
51 58 59 53 57
2
--49
3
--36
4
--49
150
0,09
+3
from--26to 16
52
5
--52
1000 150
0,12 0,135
+6 --1
--46
0,26 0,095
+3 +4
54 51 85
.6
I000 150
from--24 to 20 from--41 to 37 from--52to 4
from--20to 28
80
I000
0,09
+8
1000 150 I000 180
0,058 0,142 0,16 0,07
+18 +14 +19 +!0
om---46to 26 fr : ,6-2 16--20 from --6 to 26 0--46 from--ISto 21
81 84 52 84 59 52
I000
0,59 0,068 0,085 0,09 0,19
+8 from--37to 53 +30 13--36
50
150 !000 180 ,1000
+32
I0--80
54
+22 +29
6--80 2--88
82 89
,
-84
8
--40
9
--42
I0
--22
!1
--30
160
0,28
0,068 +20
53
82
thickness of 2 mm. After cooling the asphalt (2 h), the platewas set in the heating and cooling chamber and clamped by one end (the asphalt-free end) in a vertical position; the plate was chilled to -60~ and held for i h at that temperature, after which it was warmed up slowly at a rate of 0.15-0.2~ The loss factor was determined while raising the temperature to 60-90~ the softening point of the asphalt) at resonance frequencies of 100-2000 Hz, being performed every 1.5-2~ In Fig. i we show the temperature dependence vibration loss factor at resonance frequencies of 150 and i000 Hz for paving
636
(depending on the determination of the mechanical and structural
asphalts. The temperature dependences of the dissipative properties si~ow major differences from one asphalt to the other. However, there is one common feature for all of the samples - the presence of a region of maximum dissipation of energy, in which the loss factor passes through a maximum. Some asphalts give two maximum values of the loss factor (samples 3 and 9), indicatingtemperaturerelated extremal phase transitions in th structure of the asphalts [5] (the same as in polymers [i]) and a complete analogy between the mechanisms of energy absorption by asphalts and by polymers. Materials for which the loss factor is greater than 0.05 are effective dissipative materials [6]. Within the region of maximum damping temperatures that was investigated, the loss factors were high for most of the asphalts, as high as 0.26-0.54 for some of the samples; in certain cases, these values are higher than the values for polymeric materials (Table 2). Thus, for samples 3 and 9, the respective loss coefficients are 0.54 and 0.52, in comparison with values no higher than 0.25-0.3 for the polymeric materials Antivibrit-2, VM-2, and SVM-73 [6]; this difference can be explained by the specificity of colloidal structure of the asphalts
[5]. The width of the temperature interval for effective damping, in which ~I0.0S, is an important characteristic of damping materials; for the asphalts, the width of this temperature interval is generally 35-55~ but for certain samples (6 and 9) at a frequency of I000 Hz, the width is 70-90~ This is of great practical interest, since the width of this interval for polymers is usually 50-70~ [i, 6]. When we compare the data from the acoustic tests (Fig. i) with the properties of the asphalts (Table i), we cannot find any consistent influence of the asphalt quality indexes on the loss factor or the width of the temperature interval for effective damping. The difference between the temperature for maximum damping and the softening point of the asphalt varies from 24 ~ to I07~ indicating that it is completely invalid to define the interval of temperatures for maximum damping on the basis of the softening point. The other quality indexes (needle penetration, breaking point) are likewise unrelated to the loss factor. From the theory of absorption of mechanical vibrations by viscoelastic substances, it follows that the maximum damping is manifested at temperatures above the glass transition temperatures of the particular substance. For the asphalts we have investigated, this difference amounts to 50-59~ at a frequency of I000 Hz (see Table 2), regardless of the grade of asphalt, the original raw material, or the product manufacturing technology. This means that the glass transition temperature for asphalts can serve as one of the indexes determining the interval of temperatures for maximum damping. It has been confirmed that the asphalt quality indexes that are generally accepted commercially do not characterize the dissipative properties of the asphalts [2, 3]. In many cases, asphaltic materials have a broader range of temperatures for effective damping than do polymeric vibration-adsorbing materials such as Antivibrit-2, VM-2, and SVM-73. Residual products from vacu~n distillation (such as samples 2 and 3) and structural asphalts from high-resin crudes (samples 8 and 9) can be recommended as effective damping materials for a broad range of temperatures. They can also be used as binders in compositions applied in the damping of metal surfaces. LITERATURE CITED i.
2.
3.
4. 5. 6.
I. I. Perepechko, Acoustic Test Methods for Polymers [in Russian], Khimiya, Moscow (1973). V. I. Khrapko, A. N. Bodan, O. S. Kachmar, et al., in: Vibration-Absorbing Materials and Coatings, and Their Application in Industry, A. S. Nikiforov, ed. [in Russian], Znanie, Leningrad (1976). A. N. Bodan, V. I. Khrapko, and V. A. Bykov, Khim. Tekhnol. Topl. Masel, No. i, 26-27 (1984). A. S. Nikiforov and S. V. Budrin, Propagation and Absorption of Sonic Vibrations in Ships [in Russian], Sudostroenie, Leningrad (1968). Z. I. Syunyaev, Physical Mechanics of Petroleum Disperse Systems [in Russian], MINKh i GP im. I. M. Gubkina, Moscow (1981). A. S. Nikiforov, ed., New Vibration-Absorbing Materials and Coatings and Their Application in Industry [in Russian], Znanie, Lenigrad (1980).
637
