The Physico-chemicals Analyzes of Copolymer Paratone 8900 Used as Viscosity Improvers for SAE 10 W-40 mineral Oil IOANA STANCIU

Paratone 8900 is used as automotive for as viscosity improvers for multi-grade oils. In this study we established the physico-chemical analyses vized of a copolymer Paratone 8900 used as viscosity improvers for SAE 10W-40 mineral oil was: spectroscopy FTIR, thermo-gravimetric differential thermal analysis (TG-DTA), and the differential scanning calorimetry (DSC). The curve DSC evaluates the glass transition temperature. The thermogrames TG and DTA to evaluates their heat resistance of copolymer Paratone 8900. The kinetic parameters of copolymer Paratone 8900 were determination a method of multilinear regression analysis.

The chemical structure of copolymer Paratone 8900 was determined using spectroscopy FTIR.The differential scanning calorimetry is widely used in the study copolymer Paratone 8900.For the polymer chemist, DSC is a handy tool for studying curing processes, which allows the fine tuning of polymer properties.The cross-linking of polymer molecules that occurs in the occurring process is exothermic, resulting in a positive peak in the DSC curve that usually appears soon after the glass transition 4-6 .The DSC used a determination the glass transition temperature of copolymer Paratone 8900 6-10 .
The object of the present paper is the determination chemical structure using spectroscopy FTIR, glass transition temperature using differential scanning calorimetry (DSC), heat resistance and kinetic parameters using thermogravimetric differential thermal analysis (TG-DTA) for a Paratone 8900 copolymer -recommended as viscosity improvers for multi-grade oils.The thermogrames TG and DTA to evaluates their heat resistance of copolymer Paratone 8900.The kinetic parameters of copolymer Paratone 8900 were determination a method of multilinear regression analysis.

The following copolymer was used as: poly(ethylene-co-propylene) (Exxon Chemical)trade name Paratone 8900
Average molecular weight of Paratone 8900 was determined by GPC using a GILSON.The copolymer Paratone 8900 were average molecular weight 1.12 x 10 5 g • mol -1 and number average molecular weight 4.73 x 10 4 g • mol -1 .Their ratio, which can be taken as a measure of copolymer polydispersity, is 2.36.FTIR spectra of copolymer measurement using FT-IR GX Perkin Elmer spectrophotometer in the range of 4000 to 500cm -1 , with a resolution of 4cm -1 .
The curve TG and DTA were determined using DSC DuPont 2000.The experiments were performed in water atmosphere, operated in range 40-600 o C and a heating rate 20 o C • min -1 .
A method of multilinear regression analysis (MLRA) of the kinetic equation was chosen for the simultaneous evaluation of the activation energy, frequency factor and reaction order from a DTA curve.Using a computer simulation program, several DTA curves were obtained, provided with different Gaussian errors, starting from the evaluated kinetic parameters.Since the dependent variable varies within maximum one order of magnitude, constant absolute errors simulate best the naturally occurring spread of experimental data.

RESULTS AND DISCUSSION
Figure 1 present spectre FTIR of a copolymer Paratone 8900.The characteristic absorption bands of a copolymer appeared at 2923.14, 1461.08,1376.62 and 696.06 cm -1 .The significant bands, their wavenumbers and the corresponding functional groups are show in Table 1.
First, the intensity of the absorption band at 2923.14 cm -1 associated with the CH 2 asymmetric stretch [9] had decreased significantly after ages.
The second significant observation about the aged IR spectra is decomposition of the C-CH 3 bond with an asymmetric bend at 1461.08 cm -1 .The third major observation is in the intensity of the C-CH 3 bond with a symmetric bend around wave number 1376.62 cm -1 .A similar reduction was also observed for the out-of-plane CH bend absorbtion at wavenumber 696.06 cm -1 .where α is the conversion, t the time and T the absolute temperature.Arrhenius equation is generally used for the dependences of rate constant k(T) on the absolute temperature: A is the frequency factor, E the activation energy and R the molar gas constant.
The conversion function is dependent on the assumed reaction mechanism.Various from of this function have been published [3][4][5].In this work the following from of the conversion function was used: where n is the reaction order with respect to reactant, describing best our experimental data.Inserting equations ( 2) and (3) in equation ( 1), the kinetic equation in the following form is obtained: Under non-isothermal conditions the explicit temporal dependence in equation ( 4) is eliminated through the transformation: dα/dt = (A/β)e -E/RT f(α) ... (5) where α = dT/dt is the heating rate.
From experimental TGA the weight of temperature can be also determined using for following equation: where m is the reaction order.
Starting from experimental DTA curve, the kinetic parameters (E, A, n and m) were evaluated by a multilinear regression method, using the linearized from of equation (6).
Table 2 shows the values of kinetic parameters for the thermic descomposition of poly (ethylene-co-propylene) at 20 0 C min -1 heating rate, obtained by multilinear regression.
The negative value obtained for activation energy of the thermic decomposition with equation ( 4) has not a physical sense, which means that the kinetic function is not adequate for is description.
The value that is higger than one reaction order can be explained through average molecular polydispersity, can guide to such stoechiometry.
The mechanism thermic degradation of a copolymer poly (ethylene-co-propylene) is: 1.
In the temperature range 0-270 o C of copolymer is stable thermic, 2.
In the temperature range 262 and 400 o C of degradation thermic with elimination propylene.3.In the 400 and 520 o C the contiuue degradation with elimination ethylene.
The spectre IR of a copolymer Paratone 8900: CH 3 , CH 2 and CH aliphatic band.The copolymer was the glass transition temperatures -54.2 o C and at 53.40 o C. The temperature initial of a thermic decomposition is 262 0 C and temperature final 520 o C. The composition copolymer of Paratone 8900 is: 54.85 % propylene and 42.99 % ethylene and 1.465 % other aliphatic compounds.The copolymer Paratone 8900 as having a bit lower glass transition temperature and higher heat resistance.