Nondestructive testing of defects in adhesive joints

Uncompatibilized and reactively compatibilized ternary polymer blends
of PA6/PP/ABS: Morphological investigation
Biswajit Panda *, Arup R. Bhattacharyya # and Ajit R. Kulkarni #
Department of Metallurgical Engineering and Materials Science, Indian Institute of Technology
Bombay, Powai, Mumbai-400076, India
E-mail: arupranjan@iitb.ac.in ajit.kulkarni@iitb.ac.in
Abstract
Morphological investigation was carried out for melt mixed ternary polymer blends of polyamide
6(PA6)/ polypropylene (PP)/ acrylonitrile butadiene styrene (ABS) in order to understand the role
of compatibilizer in morphological developments. Uncompatibilized 80/10/10 PA6/PP/ABS
blends exhibited matrix- dispersed droplet type morphology in which the dispersed phases (PP &
ABS) were found to exhibit core-shell type of morphology. The difference in morphology type
may be due to the difference in surface free energy between the matrix and one of the dispersed
phases. Eventually it was found that “core-shell” type of morphology changed to “co-continuous”
type on increasing the concentration of PP and ABS in the ternary blends. In this context, styrene
maleic anhydride co-polymer was found to act as a compatibilizer in PA6/PP/ABS ternary blends,
manifesting in finer domain size of the dispersed phase.
Introduction
Multicomponent polymer blends consist of three or more immiscible polymers are a new
interesting area in the field of polymer blends. A variety of phase morphology has been observed
which directly influence the whole set of properties [1-2]. Three factors have been found to
influence the morphological developments in immiscible multicomponent polymer blends viz.
thermodynamic properties of the blends such as interfacial tensions of the constituent polymers
[3], melt viscosity of the constituent polymers [4] and elasticity of the constituent polymers [5].
Hobbs et al. [6] explained the morphological phenomenon in ternary polymer blends on the basis
of spreading co-efficient by modifying Harkin’s equation, in which two dissimilar phases were
dispersed in the third phase (matrix). If p, q and r are the three polymers of a ternary blend system
and if p is the matrix, then the spreading co-efficient, λrq is given as
λrq = σqp – σrp - σqr (1)
where λij is defined as the spreading co-efficient for i and j and σij is the interfacial tension
between i and j. If λrq is positive then q becomes the core encapsulated by r. Both r and q will
disperse separately when both λrq and λqr are negative. Based on the spreading co-efficient sign
four types of morphologies can be observed [7].
In the present work the morphological investigation has been carried out for PA6/PP/ABS blends
and the influence of a reactive compatibilizer on the morphological developments has been
investigated. Core-shell type of morphological observation in 80/10/10 PA6/PP/ABS has been
analyzed with the help of spreading co-efficient and interfacial energy. 40/30/30 PA6/PP/ABS
blends show co-continuous morphology. In this context morphological investigation has also
been carried out for these blends in presence of styrene maleic anhydride copolymer (SMA) in
order to understand the role of SMA as a compatibilizer.