Polyesterification Kinetics Research Articles

Kinetika Reaksi Poliesterifikasi Hidrolisat Shellac dan Anhidrida Ftalat Ditinjau Dari Reaktivitas Gugus Hidroksil

This research presents polyesterification kinetics for shellac hydrolizate-phtalic anhydride. The polyesterification kinetics is proposed by assuming that the reaction  in ideal system, whereas the reactivity of the OH groups are considered different. Polyesterification was started from purification of shelllac by hydrolisis process. Hydrolisis was done by dissolving seedlac into NaOH solution and acidification with HCl. Polyesterification was conducted by reacting shellac hydrolizate with phtalic anhydride. Both of these materials were reacted in a three necked flask under vacuum condition. The reaction was conducted in temperature range of 130-170 0 C and samples were taken every 30 minutes for a total of 5 hours, to determine the COOH concentration by titration. The investigation of reaction kinetic showed that reaction model  could describe the kinetic of polyesterification shellac hydrolizate-phthalic anhydride, especially for temperature below 150 0 C. The reaction rate constants were obtained as follows: k 1 = 19.7 e (-3802.82/T) g/mgek.menit k 2 = 29.4 e (-4062.30/T) g/mgek.menit

Palm Oleic Acid Based Alkyds: Effect of the Fatty Acid Content on the Polyesterification Kinetics

The kinetic behavior of polyesterification of the alkyd resins synthesized using glycerol and phthalic anhydride modified with oleic acid from the palm oil at temperatures between 120 and 240 °C was studied. Three alkyds having oleic acid contents of 28, 40, and 65% were prepared by employing fatty acid method. The extent of the polyesterification reaction and average degree of polymerization were monitored by determining the acid number of the aliquot of the reaction mixture at various intervals of time and by measuring the volume of water evolved. Kinetic studies revealed that initial reaction rates followed a second-order kinetics up to certain limit and thereafter deviations were observed. The extent of reaction varied from 77.4 to 86.3% before deviation for all the three samples and exhibited a considerable degree of conversion. The second-order rate constants calculated from the linear part were found to be of the order of 10−5 g (mg KOH)−1 min−1. Molecular weight of the alkyd samples was determined by GPC; number average molecular weight of the alkyds ranged from 980 to 2,070.

Polyesterification kinetics of complex mixtures in semibatch reactors

A systematic stoichiometric and kinetic model was developed for the acid-catalysed polyesterification of unsaturated dicarboxylic acids and mixtures of dicarboxylic acids. The model was based on a rigorous treatment of the functional groups and their reactions: esterification, cis–trans isomerization and double-bond saturation through Ordelt reaction. The model was applied on the polyesterification of maleic and phthalic acids with ethylene glycol, propylene glycol, diethylene glycol and dipropylene glycol in a semi-batch reactor at 160–195°C. Kinetic and thermodynamic parameters included in the model were estimated with non-linear regression. It was found that important simplifications can be introduced: the rate constants of the different esterification and isomerization reactions can be set equal, whereas it was necessary to treat the different double-bond saturation reactions with individual rate constants. A comparison of model predictions with experimental data revealed that the proposed kinetic treatment is relevant for polyesterification of complex mixtures.

How to Take the Removal of Condensation Water into Account in Polyesterification Kinetics?

In previous polyesterification reactions, the concentrations of reactants and catalyst (if present) were all expressed in moles per kilogram. In most cases, the progress of reaction was followed by the titration of acid groups. Consequently, the removal of condensation water is bound to affect the concentrations of reactants and catalyst. In this paper, a new general kinetic equation has been derived, which takes this effect due to the removal of condensation water into consideration more accurately. The unit of moll - 1 , who replaced the unit of mol kg - 1 , is led into the calculation of acid concentration and the derivation of the general polyesterification kinetic equation for the first time. Its adoption can finally eliminate the error due to the change of the density of reaction system while adopting the unit of mol kg - 1 .

Chemical kinetics of a two component phase segregated system. A simple rate model

Considerable research has been performed on polymeric systems that exhibit liquid crystalline or mesthmorphic behavior. The principal reason for this effort was that these materials might be developed as ultrahigh strength materials. Jackson and Kuhfuss from Tennessee Eastman demonstrated that liquid crystalline behavior existed in copolymers based on poly(ethylene terephthalate) (PET) and para-hydroxy benzoic acid (ABA). However, intricate details pertaining to the polyesterification kinetics have remained unexamined. Structural elucidations have generated conflicting data for the system. The 13C NMR 16 and high-temperature X-ray diffraction indicate a random behavior of PET and oxybenzoate. Thermal analyses have implied an inclination towards nonrandom assembly. Similarly, optical and electron microscopy examinations, coupled with data from X-ray and conventional electron microscopy endorse the existence of ordered domains of lamellar 4-oxybenzoate blocks in the PET/80 ABA copolyester. The cooling of a biphasic melt is known to trigger a biphasic structure [4]. Transesterification reactions between poly(ethylene terephthalate) PET, and acetoxybenzoic acid (ABA) were conducted using the melt polymerization technique to understand the transesterification kinetics of a phase segregated system. The transesterification kinetics of two compositions PET 20/80 (ABA) and PET 10/90 (ABA) have been studied at 260, 275, 290 and 305°C using dibutyl tinoxide (0.1 mole percent) as a catalyst. Then the homopolymerization of acetoxy benzoic acid was studied at similar temperatures and catalyst concentration. Few assumptions were made to simplify the kinetic analysis. 1. (1) ABA homopolymerises to form acetic acid and higher oligomers. The oligomers add on to a PET chain to give a copolymer or PET/ABA, the product of interest. 2. (2) The reaction between PET and ABA proceeds in a heterogeneous two-phase system consisting of a ABA rich and poor phase. The reaction sequence would be: (i) ABA reacts with itself to form oligomers of varying chain length and (ii) The subsequent addition of the oligomers onto the PET chain. The reaction sequence is assumed to be valid for ABA rich and poor phase. Both the reactions are assumed to be second order with respect to the reactants. Moles of acetic acid found experimentally are computed using a standard procedure. The rate constant κ is determined. The role of the catalyst is also evaluated.

Kinetic Model for the Homogeneously Catalyzed Polyesterification of Dicarboxylic Acids with Diols

A generally applicable stoichiometric and kinetic model was developed for the polyesterification of unsaturated dicarboxylic acid with diols in the presence of a homogeneous acid catalyst. The model also incorporates, besides the esterification, the cis-trans isomerization and the double-bond saturation reactions. Rate equations based on plausible mechanistic reaction steps were derived, and the parameters of the rate equations were determined with nonlinear regression analysis using the polyesterification of maleic acid with propylene glycol at 150-190 °C as a demonstration system. Comparisons of the model predictions with the experimental data showed that the approach is useful in predicting the polyesterification kinetics and the product distribution.

Models for Polyesterification Kinetics. III. Preliminary Studies on the Catalysis by Titanium(IV) Tetraalkoxides

Abstract The catalytic behavior of tetrabutoxytitanium in polyesterification between diacids and diols is studied with the help of two model reactions. One is the esterification between two mono-functional oligomers. The second is the reaction of 1-octa-decanol with octadecanoic acid either in octadecanyl octadecano-ate or in an excess of octadecanol. The behavior of this catalyst is complex since it depends on the reaction medium. A decrease of the vacuum and an increase of the acid concentration lead to poor catalytic efficiency which is also observed when the reaction is carried out in a hydrophilic medium such as polyoxy-ethylene. When the alcohol is in excess, the catalyst is much more efficient and experimental results fit with a zero overall order, although deviations are observed at the highest conversions. The existence of a complex between carboxyl groups and titanium is postulated.

Models for Polyesterification Kinetics. II. Esterification Kinetics in Nonpolar Medium

Abstract In order to examine the influence of the polarity of the reaction medium on the polyesterification mechanism, the kinetics of the reaction of 1-octadecanol with octadecanoic acid in octadecanyl octadecanoate is studied with and without p-toluenesulfonic acid catalyst. Without added catalyst the overall order is 2.5 and the orders in acid and in alcohol are 1.5 and 1, respectively. The mechanism consists of an autocatalysis by the acid and involves a nonnegligible dissociation of ion pairs. This differs from the observation made in more polar media. With added p-toluenesulfonic acid, the reaction is first order in alcohol, acid, and catalyst. Activation entropy is the same both for catalyzed and noncatalyzed reactions. The catalytic effect is due to a large decrease of activation enthalpy.

Models for polyesterification kinetics. I. Esterfication kinetics in polar medium

AbstractThe kinetics of the reaction of 1‐octadecanol with octadecanoic acid and w‐carboxy polyxyethylene with w‐hydroxy polyoxyethylene in the absence of a cataylst were studied as models of polyesterification. Both rreactions are third order. Order two in acid and one in alcohol have been experimentally established by studies of nonstoichiometric systems. These results are not in agreement with recent work related to polyesterification kinetics. The mechanism involves autocatalysis by the acid and the presence of nondissociated ion pairs. Activation enthalpies and entropies are given.

Has the elimination of water to be taken into account in polyesterification kinetics?

Various kinetic calculation methods taking the elimination of water into consideration or not, are reviewed and commented.