In the recent years, biodegradable aliphatic polyesters-based composite materials have attracted substantial interest, primarily due to their sustainable production, use and end-life. This chapter discusses the preparation, characterisation, and properties of nanoclay-containing composites of biodegradable poly(butylene succinate) (PBS) and poly[(butylene succinate)-co-adipate] (PBSA). Various nanocomposite structures arising from the incorporation of layered silicate particles, both pristine and organically modified, into the neat PBS and PBSA matrices is critically reviewed. Good dispersion of the layered silicates, especially the organically modified layered silicates, tends to result in an improvement in a number of properties of the final nanocomposites: storage modulus, tensile modulus, gas barrier properties, degradability, and thermal stability, when compared with the neat polymers. L. Avérous and E. Pollet (eds.), Environmental Silicate Nano-Biocomposites, Green Energy and Technology, DOI: 10.1007/978-1-4471-4108-2_7, Ó Springer-Verlag London 2012 165 166 V. Ojijo and S. S. Ray
Synthesis, Structure and Properties of PBS and PBSAPBS is a biodegradable aliphatic thermoplastic polyester which has a melting point of around 90-120°C and a glass transition temperature which lies between -45 and -5°C [25][26][27][28][29][30]. It is produced through condensation polymerization of a glycol, 1, 4-butanediol and an aliphatic dicarboxylic acid, succinic acid [25-27, 29, 31, 32]. The unit chemical structure of PBS is as shown in Fig. 7.1. However, due to the relatively low molecular weight, which makes it weak and brittle, chain extenders are to be used to increase its molecular weight [26,33]. In their patent, Kawasaki and Kawakura [33] described the use of, among other chain extenders, hexamethylene diisocyanate (OCN-C 6 H 12 -NCO), in a coupling reaction between the polyester prepolymers. Each PBS chain consisted of 0.1-5 parts by weight of diisocyanate with 100 parts of aliphatic polyester prepolymer having a number average molecular weight of at least 5000. Relatively higher molecular weight chains were then achieved through the urethane bonds derived from the diisocyanate. Apart from being strong, PBS has many interesting properties: biodegradability; melt processability; thermal and chemical resistance [2,26,34]. Their mechanical properties such as elongation at break and tensile strength are comparable with those of PP and LDPE while their crystallization behaviour is similar to that of polyethylene with well formed lamellar morphologies [30]. Because of its excellent processability, PBS can be processed in the field of textile into: melt blown; multifilament; monofilament; nonwoven; flat and split yarn and in the field of plastics into: injection moulded products; film; paper laminate; sheet and tape [26]. However, even though it has some excellent properties, which suggest potential applications, some of its other properties such as softness, gas barrier properties, etc. are frequently not adequate for a w...
