Biodegradationofpoly-e-caprolactone/poly-b-hydroxybutyrateblend F.LaCara a, *, B. Immirzi b ,E.Ionata a , A. Mazzella a , S. Portofino b , G. Orsello b ,P.P.DePrisco a a Istituto di Biochimica delle Proteine, CNR, Via P. Castellino 111, 80131 Naples, Italy b Istituto di Chimica e Tecnologia dei Polimeri, CNR, Comprensorio Olivetti, Via Campi Flegrei, 35, 80078 Pozzuoli (NA), Italy Received 29 May 2002; received in revised form 19 July 2002; accepted 23 July 2002 Abstract Poly-e-caprolactone (PCL), poly-b-hydroxybutyrate (PHB) and one of their blends have been incubated in presence of some microbialconsortiaisolatedfromplastic-contaminatedenvironments.Intheconditionsusedinthiswork,bothpurePCLandPHB samples were degraded with strong erosion of the amorphous zones. The PCL/PHB 70/30 blend showed, after only 20 days of incubation,thatspheresofPCLwereborderingwithspherulitesofPHBindicatingcompletedegradation.Thecrystallinitycontent of homopolymers and blend were investigated at different degradation times: whilst PCL crystallinity remains constant, both PHB and the blend PHB-phase crystallinity increased. Data from differential scanning calorimetry are well fitted with those obtained by scanning electron microscopy, gel permeation chromatography and weight loss analysis. # 2002 Published by Elsevier Science Ltd. Keywords: Poly-e-caprolactone; Poly-b-hydroxybutyrate; Blend; Biodegradability 1. Introduction A remarkable characteristic of polyesters like poly-b- hydroxybutyrate (PHB) and poly-e-caprolactone (PCL) is their biodegradability in the environment. Films and fibres of these polymers can be degraded in soil, sludge, or seawater. Under optimum conditions the degrada- tion is extremely fast. Some microorganisms, such as bacteria and fungi, have been demonstrated to degrade a wide variety of plastics [1,2]. The mechanism involves extracellular depolymerases [3,4] that hydrolyse PHB and its copolymers, in the vicinity of the cells, into dimers and/or monomers. These resulting products are absorbed and used as nutrients for the microorganisms [5,6]. On the other hand PCL is a biocompatible polyester that is degraded by many microorganisms and in particular by the mould Pullularia pullulans [7]. In previous work we prepared blends of PHB and PCL to be used in biomedical field [8–10]. PHB is thermoplastic polyester produced by bacterial fermen- tation [11] with characteristics similar to poly- propylene. PCL is also a biodegradable polyester, produced synthetically, with a low glass transition temperature (T g ) and melting temperature (T m )[12].To balance the properties of these polyesters we prepared reactive blends by using peroxides as compatibilizing agents. In this paper we report on the biodegradation of homopolymers treated with peroxide and a single blend prepared mechanically with the aim of obtaining more information on the biodegradation rates of new materi- als for potential biotechnological applications. 2. Materials and methods 2.1. Polymers Poly-e-caprolactone (PCL), trademark CAPA 650, with a reported Mw of 55000 was kindly supplied by Solvay. Poly-b-hydroxybutyrate (PHB) was kindly sup- plied by ICI (England) and was reported to be a high molecularweightpolymer,withMwof790000. Dicumylperoxide (DCPO) (Polyscience) and chlor- obenzene (Labscan) were used as received. All the other reagents used were of analytical grade. 0141-3910/02/$ - see front matter # 2002 Published by Elsevier Science Ltd. PII: S0141-3910(02)00236-7 Polymer Degradation and Stability 79 (2003) 37–43 www.elsevier.com/locate/polydegstab * Corresponding author. Tel./fax: +39-081-613-2293. E-mail address: lacara@dafne.ibpe.na.cnr.it (F. La Cara).