LITERATURE REVIEW

2

CHAPTER 1

INTRODUCTION

Electrospinning is a renowned technique for generation of polymeric nanofibres that has very large suface area to volume ratio. Nanofibres obtained from electrospinning, has diverse applications in nanocomposites such as scaffolding, biomedical and drug delivery system.

Polyvinyl Alcohol (PVA) is a water soluble polyhydroxy polymer, which has good mechanical properties, chemical resistance and biological properties. PVA can be cross linked with biopolymers to improve mechanical properties and anti-water solubility. PVA has been electrospun into nanofibres with diameters ranging from 100nm to 1000 nm. Studies showed that lower concentration of the solution will form fibres with beads and with increment in solution concentration, the form changed from beaded fibre to smooth and uniform fibres.

Calcium alginate is an anionic linear polysaccharide extracted from brown seaweed. It is composed of 1-4 -L-Guluronic acid and -D-Mannuronic acid. Calcium alginate is biodegradable and has a broad application in the field of textiles, food and biomedical application. The alginates which are capable of forming firmer structure with calcium ions are known as calcium alginates which form stronger gels on wound surface compared to that of sodium alginate.

Wound healing will start from predictable sequence of events that has a cascade effect until the wound is bridged by a scar tissue. In any case, it is accepted that rapid wound healing occurs in the moist environment and present wound care products provide these conditions.

Many wound dressing materials are available and they are being investigated. The use of hydrogel will provide a rapid wound healing by creating a moist wound surface that reduces the buildup of necrotic tissue. Sodium alginate and polyvinyl alcohol based hydrogel showed an improved healing rate of artificial wounds in rats. Alginates are highly absorbent and gel forming agents which has haemostatic properties. In contact with the wound surface, the wound exudates convert calcium into sodium salt, forms gel, and gets absorbed by the body. The latter facilitates the removal of alginate dressing by dissolution.

Electrospinning of pure alginate solution is not possible. For polyvinyl alcohol, continuous fibres were successfully electrospun from PVA solutions of 7, 8 and 9%. Blended solutions of polyvinyl alcohol and sodium alginate have been electrospun into nanofibers of which sodium alginate having 2 wt%, and polyvinyl alcohol having 7, 8 and 9 wt%. PVA and sodium alginate solutions were blended in the ratios of 100:0, 70:30, 50:50 and 30:70. The results also show that, uniform nanofibres were generated, when polyvinyl alcohol proportion in the blend was increased. The maximum concentration of sodium alginate electrospun was ~4 wt%. Electrospinning of polymer blends have combined properties of individual polymer. For example, poor mechanical performance of biopolymer is overcome by including a synthetic polymer that has good mechanical properties, biodegradability and biocompatibility. There have been studies about calcium alginate hydrogels which shows poor mechanical properties, but, there was no report regarding the blend of calcium alginate and PVA found in the literature.

The results were analyzed into two parts. The first part has the examination of PVA and calcium alginate blend. The second part has the rate of wound healing on the wound surface.

The results were analyzed into two parts. The first part has the examination of PVA and calcium alginate blend.

CHAPTER 3MATERIALS AND METHODS

The details on the materials used and the methods followed in the present study are explained below.

3.1

MATERIALS

In the present work, flax braided fabric is the reinforcement material and epoxy resin is used as a matrix material. The flax yarn of 44 linen count has been used for reinforcement development and room temperature epoxy resin has been used as matrix material. The resin specifications are given below.

Epoxy resin

- Araldite LY556

Hardener

- XY 51

Curing temperature

- Room Temperature

Density of epoxy resin

- 1.11 g / cm3

Density hardener

- 0.98 g / cm3

Mixing ratio (resin: hardener)

- 2:1

LY 556 Epoxy is based on bishphenol A and epichloro hydrin. XY 51polymide based hardener was used. Initial stage of resin and hardener is liquid state. When resin is added to hardener it becomes rigid and reaches solvent free thermoset stage due to chemical reaction between resin and hardener.

3.2METHODS

3.2.1 Production of Reinforcement Material

The flax braided fabric samples were produced using 44 linen count yarn, which were procured in the market. Flax braided perform was produced in LS 3

FS 14

LS 2

LS 1.5

LS 2

FS 13

38 mm

23 mm

33 mm

27 mm

LS 2

20 mm

LS 2

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LS 2

LS 2

20 mm

50 mm

38 mm

23 mm

27 mm

50 mm

LS 2

LS 3