Nondestructive testing of defects in adhesive joints

A Study of mechanical properties of flax-g-poly(MA) reinforced phenol-
formaldehyde composites
Susheel Kalia 1* , B.S. Kaith 2 , Sanjeev Sharma 1 , and Bandna Bhardwaj 1
1 Department of Chemistry, Singhania University, Pacheri Bari, Jhunjhunu – 333 515 (Rajasthan)
India
2 Department of Chemistry, Dr. B.R. Ambedkar National Institute of Technology (Deemed
University), Jalandhar - 144 011, Panjab, India
* E-mail: susheel_kalia@yahoo.com, susheel.kalia@gmail.com
Abstract
In the present paper, we report the preparation of graft copolymers of flax fibers with methyl
acrylate (MA) using Fenton’s reagent (FAS-H2O2) as redox system. Synthesized flax-g-poly(MA)
was characterized with FTIR, TGA/DTA, scanning electron microscopy (SEM), and X-ray
diffraction (XRD) techniques. Composites were prepared using flax-g-poly(MA) as a
reinforcement and phenol-formaldehyde (PF) as the binding material. Mechanical properties of
phenol-formaldehyde composites were compared and it has been found that composites
reinforced with flax-g-poly(MA) showed improvement in mechanical properties. Composites
reinforced with flax-g-poly(MA) showed better tensile strength (235 N) and compressive strength
(814 N) in comparison to composites reinforced with original flax fiber which showed lesser
tensile strength (162 N) and compressive strength (372 N). Composites reinforced with flax-gpoly(MA)
shows the improved MOR, MOE, and SP.
Key Words: Fiber, Flax-g-poly(MA), Composites, Mechanical Properties.
Introduction
The renewed interest in the natural fiber has resulted in a large number of modifications in
order to bring it at par with and even superior to synthetic fibers. A rebirth in the application of
natural fibers as reinforcing agent is occurring mainly in the automobile and packing industries.
Advantage of indigenous natural fiber in their applications in the preparation of composites over
synthetic fibers has been reported by Paramasivam and Kalam [1]. Flax fiber is a better
reinforcing material for composites due to ecological and environmental merits and the attractive
mechanical properties. Flax fiber is considered to be one of the strongest fibers among the natural
fibers. Mechanical properties of polymers such as tensile strength, impact-strength, and
extensibility have a direct correlation with the percentage grafting (Pg). On grafting crystal lattice
of the polymer is disrupted but the strength of the material may act to reinforce the structure [2,
3]. However, if crystallinity is not disturbed on grafting, then continuous increase in strength can
be obtained with increase in Pg [4]. Most of the cellulosic fibers possess both crystalline and
amorphous regions. The X-ray pattern of crystalline polymers show both sharp features
associated with regions of three-dimensional order and more diffused features characteristics of
molecularly disordered substances like liquid. The occurrence of both types of features in the
fibers indicates that ordered and disordered regions co-exist in crystalline polymers. Lower
crystallinity means higher amorphous regions, which are more accessible to chemicals and water
[5]. Methyl acrylate was graft copolymerized onto cellulose in alkaline aqueous solution using
1