Elsevier

European Polymer Journal

Volume 41, Issue 9, September 2005, Pages 2171-2175
European Polymer Journal

Study on the reaction kinetics between PBT and epoxy by a novel rheological method

https://doi.org/10.1016/j.eurpolymj.2005.03.009Get rights and content

Abstract

In the present study, the reaction kinetics of polybutylene terephthalate (PBT) and epoxy system was studied by a novel rheological method. The reaction process was determined by rheological test and the results showed that there were three stages in the reaction between PBT and epoxy, which were reaction-controlling stage (stage I), reaction-stagnation stage (stage II) and diffusion-controlling stage (stage III). In addition, the stage I was selected to study the reaction kinetics by the rheological method. The results showed that the reaction between PBT and epoxy could be classified as a pseudo-first-order reaction due to the excessive amount of epoxy group. Furthermore, the reaction apparent activation energy of the stage I determined by the rheological method was 143 kJ/mol. To confirm these results, the reaction kinetics was also evaluated by the endgroup determination method, and the results showed that the reaction could also be classified as a pseudo-first-order reaction. Moreover, the apparent activation energy of the reaction was 116 kJ/mol, which was similar to that of the value obtained by the rheological method.

Introduction

Polybutylene terephthalate (PBT) is well known as a commercial thermoplastic material with various applications because of its some special properties, such as thermal resistance and chemical resistance. However, a number of problems limit its extensive application. The most important one is that the product made of the PBT has poor impact strength due to its brittleness. Many methods have been tried to solve this problem. One of the most effective and feasible methods is to blend it with other tough polymers, which is often called polymer–polymer alloying technique. However, the incompatibility between the PBT and the tough polymer is still a problem when using this method to obtain improved impact strength. In order to improve compatibility of the immiscible blends, reactive compatibilizers were selectively applied in many studies [1], [2], [3], [4], [5], [6], [7], [8], [9], [10], [11] because they could react with each polymer phase. Among these reactive compatibilizers, epoxy resin was usually chosen for PBT blend systems since it is commercially available.

In recent years, the compatibility of epoxy in blends of PBT and other components has been studied in some previous literatures [6], [7], [8], [9], [10], [11]. However, most of these studies just focused on the improvement of physical properties of the blend systems and the compatibility of two polymer phases. Few studies were reported on the examination of the reaction kinetics between PBT and epoxy, which was probably due to the complexity of the reaction and restricted methods for monitoring the process of the reaction.

Reaction kinetics of many other systems has been studied in previous literatures. Recently, Oyama et al. [12], [13] investigated reaction kinetics of the reactive PA6/PSU-MAH blends with a planar interface and Kim et al. [14] evaluated the reaction kinetics in the reactive polymer–polymer (PS-COOH/PMMA-GMA) planar interface through determining the complex viscosity (η*) of the system. All of these results suggested that the reaction kinetics might be evaluated by the rheological method as the temporal changes of rheological properties, which were related to the amount of in situ formed graft (or block) copolymers for a reactive blend, could be monitored.

Therefore, in the present study, the epoxy resin was chosen to react with PBT and the reaction kinetics of PBT/epoxy planar interface was evaluated by the rheological method. In order to confirm the results determined by the rheological method, the endgroup determination method was used to investigate the reaction kinetics of the system [15].

Section snippets

Materials

Polybutylene terephthalate (PBT), 1097A (density:1.31 ± 0.02 g/cm3; intrinsic viscosity:0.97 ± 0.02 cm3/g; melting point:222–226 °C), is a natural grade product from Nantong Synthetic Materials Co. Ltd., China and the content of carboxylic acid in it is 0.06 mol/kg. The epoxy resin, E51 (low molecular weight), was obtained from Shanghai Resin Factory Co. Ltd. and its epoxy value is 5.1 mol/kg.

Rheological analysis

For rheological analysis, PBT plates were prepared by hot compression molding method under 10 Mpa at 230 °C for 5 

Reaction evolution measured by rheological test

The changes of complex viscosity (η*) of the PBT/epoxy system as a function of time at 230 °C are shown in Fig. 1. It can be seen from the Fig. 1 that the process of the PBT/epoxy system could be divided into three different stages. η* increased within short time during the stage I and then maintained at a steady value showed in stage II (1500 s < t < 2500 s). After that, η* increased slowly again during the stage III. However, there was almost no change in η* of PBT/paraffin system during the whole

Conclusions

In the present study, the reaction kinetics of polybutylene terephthalate (PBT) and epoxy were studied by the rheological method. The results showed that the reaction between PBT and epoxy could be classified as a pseudo-first-order reaction due to the excessive amount of epoxy group and the reaction apparent activation energy of the stage I determined by the rheological method was 143 kJ/mol. Evaluated by the endgroup determination method, the reaction kinetics of this system was found to be

Acknowledgement

This work was supported by research grants (NSFC No.50390090) from the National Nature Science Foundation of China.

References (20)

  • P. Martin et al.

    Reactive compatibilization of blends of polybutyleneterephthalate with epoxide-containing rubber

    The effect of the concentrations in reactive functions Polymer

    (2003)
  • P. Martin et al.

    Particle-in-particle morphology in reactively compatibilized poly(butylene terephthalate)/epoxide-containing rubber blends

    Polymer

    (2004)
  • S.C. Jana et al.

    Compatibilization of PBT-PPE blends using low molecular weight epoxy

    Polymer

    (2001)
  • H. Yang et al.

    Morphology and thermal and mechanical properties of PBT/HIPS and PBT/HIPS-G-GMA blends

    J Appl Polym Sci

    (2002)
  • P. Martin et al.

    Complex processing–morphology interrelationships during the reactive compatibilization of blends of poly(butylene terephthalate) with epoxide-containing rubber

    J Appl Polym Sci

    (2004)
  • E. Lievana et al.

    Impact modification of PA-6 and PBT by epoxy-functionalized rubbers

    Macromol Symp

    (2003)
  • A. Arostegui et al.

    Compatibilization of a poly(butylenes terephthalate)/poly(ethylene octene) copolymer blends with different amounts of an epoxy resin

    J Appl Polym Sci

    (2004)
  • D. Dharaiya et al.

    A study of the use of phenoxy resins as compatibilizers of polyamide (PA6) and polybutylene terephthalate (PBT)

    Polym Eng Sci

    (2003)
  • K. Chiou et al.

    Reactive Compatibilization of polyamide-6 (PA 6)/polybutylene Terephthalate (PBT) blends by a multifunctional epoxy resin

    J Polym Sci B: Polym Phys

    (2000)
  • Y. Shieh et al.

    Reactive compatibilization of PP/PBT blends by a mixture of PP-g-MA and epoxy resin

    J Appl Polym Sci

    (2001)
There are more references available in the full text version of this article.

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