Biopol mechanical properties

Tests by Gatenholm et al. [8,10] on PHB-HV copolymers containing cellulose fibers (for example, the tradenamed Biopol) show that the mechanical properties of these systems are determined by the fiber and the fiber matrix interface on the one hand, and on the other hand by the composition of the matrix, that is, of HV proportion in the matrix. At an increased proportion of HV, the stiffness of the composite is reduced up to 30%, whereas elongation at break increases until about 60%. 

Poly[3-hydroxybutyrate] was the first PHA to be produced on an industrial scale, but its brittle nature, its poor mechanical properties and its high production cost limited its application potential. In the early 1990s, Imperial Chemical Industries [ICI] started the production of poly[3-hydroxybutyrate-co-3-hydroxyvalerate] [P3HB3HV] under the trade name Biopol . This material showed lower degrees of crystallinity and superior mechanical properties. Later on, the production of Biopol was continued by Monsanto and subsequently followed up by Metabolix. PHAs were originally intended as bio-based alternatives for polyolefins used in plastic containers, films and bottles. Despite the large interest in PHAs, their application remains, however, limited due to their narrow processing window [84, 85]. 

P(3HB-co-3HV) is commerdally known as Biopol , and the processing of P(3HB-co-3HV) fiber was improved by adding some nudeating agent to enhance the crystallization rate. Ohura et reported the relationship between mechanical properties and biodegradability of P(3HB-co-14%-3HV) fiber... 

Importantly, it has been stated that permeability of the seed coat may be affected by the mechanical properties of the cuticle (Ma et al., 2004 Zeng et al., 2005). The mechanical properties of a material are influenced by the pol)nners that are present in the material (i.e. their chemical composition, molecular arrangement, and interadion of the molecules) along with temperature and moisture content (Hoseney, 1994). As noted, the glass transition temperature (Tg) is a pol3mier science concept that has been applied to food science research for studying the material properties of biopol)nners (Brent et al., 1997 Perdon et al., 2000). 

Extensive work was conducted for microbial production of PHB and PHBV. Accumulated experience has led to the industrial production of PHB by Chemie Linz AG/Austria in the 1980s, using the bacterial stiaia Alcaligenes latus. However, the poor mechanical properties and weak processibility limited development of PHB as an environmentally friendly packaging material. PHBV was subsequently developed by Zeneca/UK (then ICI or Imperial Chemical Industries Co. Ltd), using Wautersia eutropha as a production strain. PHBV had improved properties over PHB (Table 2.1) and ICI developed PHBV with the Trade name of BIOPOL. 

The idea of treating jute fibres with different additives to enhance the properties of hot-pressed Biopol composites was examined by Khan et al. (1999). As in a number of other research studies, Biopol , a PHBV originally developed by ICI but now owned by Metabolix Inc of the US, was the chosen polymer matrix. Jute was used in the form of a fabric combined with sheets of polymer film. Fibre treatments included 2-ethyl hexyl acrylate (3%), 7-methacryloxypropyltrimethoxysilane (2%) and trimethoxyvinylsilane (0.5%). These treatments were effective in improving composite mechanical properties by up to 80% over and above those properties obtained when using untreated fibre. 

Asrar J and Grays K (2002), Biodegradable polymer (Biopol ) , in Doi Y and Steinbuchel A, Biopolymers Volume 4, Weinheim, Wiley-VCH Verlag, pp. 53-90. Avella M, La Rota G, Martuscelli E, Raimo M, Sadocco P, Elegir G and Riva R (2000a), Poly(3-hydroxybutyrate-co-3-hydroxyvalerate) and wheat straw fibre composites thermal, mechanical properties and biodegradation behaviour , J Mat Sci, 35 (4), 829-836. 

Khan M A, Idriss Ali K M, Hinrichsen G, Kopp C and Kropke, S (1999), Study on physical mechanical properties of Biopol-jute composite , Polym - Plast Technol Eng, 38 (1), 99-112. 

Poly((R)-3-hydroxybutyrate-co-(R)-3-hydroxyvalerate) (P(3HB-co-3HV)) has been produced commercially under the trade name of Biopol. Due to isodimorphism (Fischera et al, 2004), the mechanical properties of this copolymer are similar to that of PHB. Therefore, copolymers of 3HB and 3-hydroxyhexanoate (3HH) (Doi et al, 1995) have been produced which show high elongation at break, but low tensile strength. To increase the strength, cold-drawing and copolymerization has been proposed (Fischera et al, 2004) and the degradation has been examined (Cao et al, 1999). 

Khan, M. A, Kopp, C., and Hinrichsen, G. (2001] Effect of vinyl and silicon monomers on mechanical and degradation properties of biodegradable jute-biopol composite, J. Reinforc. Plast Compos, 20, 1414-1429. 

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