Polycaprolactone crystallization

The morphology of spin-cast film, thickness of 180 nm, from polycaprolactone shows many spherulitic structures with fibrillar nanostructures formed of lamellae lying edge on (about 10 nm thick) and areas with lamellar sheets lying flat on. Different crystalline structures are found when the sample is melted and crystallized as a function of temperature. These two studies reinforce the complex inner relationship between physical treatment and nanostructure. 

There is a large body of patent literature and a growing amount of scientific literature on blends of polycarbonate with various crystallizable polyesters. The latter would include poly (ethylene terephthalate), poly-(butylene terephthalate), polycaprolactone, and certain copolyesters derived from mixtures of terephthalic acid and isophthalic acid co-reacted with 1,4-cyclohexanedimethanol (79, 80, 81,82). As shown recently, some of these mixtures form miscible blends although the polyester possesses the possibility of crystallizing. The number of patents on such systems indicates a degree of commercial interest. 

Crystallization can take place whenever the polymer is at a T above T. At 25° C, polycaprolactone is above Tg and so it may crystallize. On the other hand, polyfethylene terephthalate) can be quenched to 25°C at various rates resulting in various degrees of crystallinity which will not change as long as the temperature does not exceed Tg. So this polymer will be more suitable for the biodegradabOity study. 

Figure 5-6. (a) Dependence of T on p for mixtures of polymethyl methacrylate with diethyl phthalate. Comparison of experimental results with equation (5-8). Parameters found were ctjctp = 2.32, Tgd = -57 °C, Tgp = 104 °C.f [After F. N. Kelley and F. Bueche, J. Polym. Sci., 50 549 (1961)] (b) Variation of Tg for a miscible polymer blend of polycaprolactone (PCL) and poly(styrene-co-acrylonitrile) (SAN), with a description of the data using the Gordon-Taylor relationship, equation (5-27). The two points at low SAN content have a higher-than-expected Tg because of crystallization of the PCL. [After S-C. Chiu and T. G. Smith, J. Appl. Polym. Sci., 29,1797 (1984). Copyright 1984, Wiley Periodicals, Inc., a Wiley Company.]... 

Polycaprolactones possess good low-temperature impact strength for paintable body panels, good fuel and oil resistance, and hydrolytic stability for seals, gaskets, and belting. Polycaprolactones have fast crystallization rates, high crystallinity, and are generally easily processed into complex parts. 

Chang Peter R., Ai Fujin, Chen Yun, Dufresne Alain, and Huang Jin. Effects of starch nano-crystal-graft-polycaprolactone on mechanical properties of waterborne polyurethane-based nanocomposites. J. Appl. Polym. Sci. Ill no. 2 (2009) 619-627. 

Crystallization in BCP where one or more of the segments are crystallizable can and does occur. A particularly interesting early study was of polycaprolactone/ polyoxyethylene triblock copolymers PCL-PEO-PCL. Where one of the components constitutes a distinct majority, that one crystallizes (Perret and Skoulios 1972a),... 

Balsamo V, Muller AJ, Stadler R (1998) Antinucleation effect of the polyethylene block on the polycaprolactone block in ABC triblock copolymers. Macromolecules 31(22) 7756-7763 Balsamo V, de Navarro CU, Gil G (2003) Microphase separation vs crystallization in polystyrene-b-polybutadiene-b-poly(epsilon-caprolactone) ABC triblock copolymers. Macromolecules 36... 

Shabana HM, Olley RH, Bassett DC, Zachmann H-G (1996) On crystallization and phase separation phenomena in PEN/PHBA copolyesters. J Macromol Sci Phys B35 691-708 Shabana HM, Olley RH, Bassett DC, Jungnickel BJ (2000) Phase separation induced by crystallization in blends of polycaprolactone and polystyrene an investigation by etching and electron microscopy. Polymer 41 5513-5523... 

Figure 4 Transmission electron micrographs of polystyrene-block-polybutadiene-block-polycaprolactone (S-B-Cl), stained with OSO4. B appears dark. Cl appears light, and S appears grey, (a) Top view onto the cylindrical domains (b) side view onto the cylindrical domains (c) scheme of the morphology (d) scheme of the distortion of round cylinders into cylinders with edges by the crystallization of the Cl-core. (From Ref. 43, Copyright 1999 American Chemical Society.)...

It should be pointed out that two-dimensional matching can also be found occasionally in polymer epitaxial systems, even though very seldom. For example, when crystallizing polycaprolactone (PCL) on the oriented PE substrate, based on the almost identical orthorhombic unit cells of PCL with parameters a = 0.747, = 0.498, and c=1.705nm and PE... 

Aliphatic polyesters have crystaUine melting points lower than polyethylene. Polycaprolactone has a melting point of 50 °C. Placing phenyl rings in the backbone increases both and Tg significantly. Poly(ethylene terephthalate) with = 265 C and Tg = 65 °C and polyfbutylene terephthalate) with T = 210 °C and Tg = 35 C are both commercial thermoplastics (Formula 1.8). Closely related to these polymers is poly(bisphenol-A carbonate) (Formula 1.9) with Tg = 150 °C. This polymer usually does not crystallize. 

Figure 12.14 presents the values of the inverse of the half-crystallization time, I/Tsoo/, as a function of reported by Muller et al. [133] for a PLLA-6-PE and a corresponding homopolymer. The results clearly indicate that the PLLA block within the copolymer crystallizes at much slower rates than homo-PLLA when similar crystallization temperatures are considered by extrapolation. Such a decrease in the overall crystallization rate of the PLLA block within the copolymer (and the higher supercooling needed for crystallization) is considered responsible for the coincident crystallization effect that can be observed when the PLLA-6-PE diblock copolymer is cooled down from the melt at rates larger than 2°C/min. A similar effect has also been reported by Muller et al. for weakly segregated poly (p-dioxanone) -6-polycaprolactone diblock copolymers [135,136]. 

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