Apparatus for determining dynamic characteristics of polymers by the forced resonance vibration method

1356

A. I. Bm~Gi~rsxII and Yu. V. ZELEN'EV

e x t r a p o l a t i o n can be used [6, 7] to determine the relative concontratiou of N]~ groups 0.5 hr after the beginning of the reaction, c ~ and b~ (Table 2). Values of c ~ and bl being known, relative values of ¢~H a n d consequently, C~Hl were derived since the value of ( o ~ ~ - c ~ , ) is known from the kinetic curve (Fig. 1) at zero time. Results confirm t h a t fSr P E I of M > 2000 the content of p r i m a r y amino-groups is practically equal to the content o f t e r t i a r y amino-groups, independent of the m e t h o d of preparing the polymer. F o r polymers with M > 2000 the percentage of p r i m a r y amino-groups becomes considerably greater t h a n t h a t of t e r t i a r y amino-groups as a result of terminal p r i m a r y amino-groups. Thus, a fairly accurate a n d accessible chromatographic method was developed for t h e q u a n t i t a t i v e determination of t e r t i a r y nitrogen in P E I , this m e t h o d being based on cyanethylation. The authors are grateful to D. S. Zhuk for his constant a t t e n t i o n and discussing results. Translated by E. SEM.ERE REFERENCES

1. P. A. GEMBITSKII, D. S. Z H U K and V. A. KARGIN, Polietilenamin (Polyethylene amine). Izd. "Iqauka", 1971 2. C. D. DICK a n d G. E. HAM, Polymer Preprints 1O: 729, 1969 3. G. M. LUKOVKIN, V. M. P S H E Z H E T S K I I and G. A. MURTAZAYEVA, Europ. Polymer J. 9: 559, 1973 4. S. I. OBTEMPERANSKAYA and N. D. I(HOE, Zh. analit, khimii 24: 1588, 1969 5. D. KENDALL (Ed.), P r i k l a d n a y a i n f r a k r a s n a y a spektroscopiya (Applied I R Spectroscopy). Izd. "lYlir", 1970 6. G. M A R K and G. REI(HI~IITS, K i n e t i k a v analiticheskoi khimii (Kinetics in Analytical Chemistry). Izd. "]Kir", 1972 7. J. GORDON HANNA and SIDNEY SIGGIA, J. Polymer Sei. 56: 277, 1962

APPARATUS FOR DETERMINING DYNAMIC CHARACTERISTICS OF POLYMERS BY THE FORCED RESONANCE VIBRATION METHOD* A . I . BRAGINSKII a n d Y u . V. ZEr,E~EV 1~. K. K r u p s k a y a Regional Pedagogical Institute, Moscow

(Received 10 January 1974) A method and a p p a r a t u s are described for determining Young's d y n a m i c modulus and the mechanical loss faotor of polymer materials over a wide range of temperature. The layout of the apparatus, methods of measuring dynamic characteristics of polymers are described and experimental results obtained with a polymer composition prepared from epoxy resin a n d "Getinaks". * Vysokomol. soyed. A17: No. 5, 1179-1181, 1975.

Apparatus for determining dynamic characteristics of polymers

1357

W m ~ studying properties of polymer materials it is important to measure dynamic characteristics which determine vibratory energy scattering in the polymer material; the logarithmic decremdnt of a t t e n u a t i o n of vibration ti, the coefficient of mechanical loss t a n $ etc. for the measurement of which various methods are used [1-3]. 2

3

II

I

-i ~ct. 1. Layout of device used for determining dynamic characteristics of polymers. I n the apparatus in question tau g a n d the dynamic modulus of elasticity E are determined by a method of forced resonance vibration as follows. Flexural vibrations are set up in a sample held in a bracket. The resonant vibration frequency of the sample is obtained b y changing the master frequency, the width of the resonance curve being measured at the level of 0.7 of the vibration amplitude of the sample with a resonance of zlf,.~ u n d e r conditions of a constant t r a n s m i t t i n g force and then t a n 5 and E are calculated from t h e formulae ~fo.~

tan 8= - -

]

E=

39pf'l" h~

- - ,

(1)

(2)

where 3' is resonant frequency, p, density of the polymer; l, length of the bracket to the point of fixing, era and h, thickness of the sample, cm. I t should be noted t h a t formula (2) is valid for the first form of vibrations (harmonic) of the sample held in a bracket. A diagrammatic layout of the apparatus is shown in Fig. 1. Vibrations of the sample a r e induced and amplitude measured by a non-contact electromagnetic method. Sample 2 held with a bracket in equipment 11 is placed with its free end between two coils of electromagnet 12. Current is transmitted to the coil from oscillator 8. Driving voltage frequency is controlled b y frequency meter 9 with an accuracy of ±0-01%. Vibrations are recorded b y a n electromagnetic telephone system 3, joined to electronic voltmeter 10. I n contrast to reed type apparatus now used to study relaxation processes in polymers, the apparatus proposed enables simultaneous measurement to be made of dynamic characteristics of five samples. Figure 2 shows the variation of E and t a n g for two materials. Another distinctive feature of the apparatus a n d methods described is t h a t for all the five samples a temperature field constant in time is established with a high degree of accuracy during the measurements. Accuracy and reliability of temperature measurement can be increased by using four

1358

A.I.

:BI~A(}INSKII and Yu. V. ZELENEV

chromel-copel thermocouples, the hot ends of which are introduced into control sample 5 evenly situated longitudinally. A control sample is placed in the direct proximity of polymer samples tested. Readings of thermocouples are obtained with an 1%-308 7 potentiometer. Measurements are carried out at the moment, when the indications of all thermocouples are the same. The cold junction of the thermocouple is placed in ultrathermostat 6. W i t h this method of control and temperature measurement the error is not more than =E0.25 °. Testing the linearity of the o s c i ll a t o r - act i v at o r - d at a unit-recording system shows t h a t the system is linear over the entire range of variation of the output signal of the generator and of operating frequencies. 3, q tne/cm z 10m -

/0 8

/07

i

17"3

0I -60

I

,

0

GO

7~°C

FIG. 2. Temperature re]ationships of E (a) and J (b) for an epoxy compound (1) and Getinaks (2). The average non-linear distortions of the output signal of the telephone do not exceed 1-85~o. When testing lincarity the I~IhVP quenched steel sample of 180 X 20 X 0-5 m m was fastened in one of the channels of the apparatus. The relation between the vibration amplit u d e of the sample at the data unit level and the output signal of the generator was then recorded. Measurements were made at 20 ° at frequencies of 20-200 c/s, o11 changing the signal of activation from 0 to 60 V. The levels of non-linear distortions were recorded at the same time by measurement with a device connected to the input of the recording voltmeter. Considerable experience of the operation of this apparatus leads us to conclude t h a t the time of measurement is considerably reduced by using it and the reliability of results of testing homogeneous samples and accuracy of t em p er at u r e measurement of samples are increased. Translated by E. SEMERE

REFERENCES

1. V. M. CHERNYSHEV, Sb. Problemy prochnosti v mashinostroycnii (Problems of Strength in Mechanical Engineering). 1%ostov, 1962 2. Yu. V. ZELENEV, S. K. ABRAMOV, B. S. KHODYREV and Yu. V. YEFREMUSHKIN Mekhanika polimerov, 152, 1972 3. R. PLANKETT, Measurement of Damping, l~ew York, 1964