Biodegradable Polymer Blends Research Articles

Biodegradable polymer blends of poly(3-hydroxybutyrate) and hydroxyethyl cellulose acetate

The melting and crystallization behaviour and phase morphology of poly(3-hydroxybutyrate) (PHB) and hydroxyethyl cellulose acetate (HECA) blends prepared by casting films have been studied by differential scanning calorimetry (d.s.c.), Fourier transform infra-red ( FTi.r.), scanning electron microscopy and polarizing optical microscopy. The melting temperatures of PHB in the blends were independent of the blend composition with PHB contents above 20%. The melting enthalpy of the blends decreased with increase in the HECA component and was close to the additive value of the enthalpy of the two components. The glass transition temperatures of PHB in the blend were constant at about 8°C. No specific interaction between the two components was found by FTi.r. The crystallization of PHB in the blend was affected by the HECA component, especially in the PHB/HECA (20/80) blend. During the d.s.c. cooling run at a lower cooling rate, two separate transitions were found for PHB/HECA (80/20), (60/40) and (40/60) blends, which corresponded to the crystallization of PHB and the phase transition of HECA from an isotropic phase to a mesophase in the blends, respectively. The phase transformation of HECA from an isotropic phase to a mesophase was almost independent of the PHB component.

Biodegradable polymer blends of poly(3-hydroxybutyrate) and poly(DL-lactide)-co-poly(ethylene glycol)

The melting and crystallization behavior and phase morphology of poly(3-hydroxybutyrate) (PHB) and poly(DL-lactide)-co-poly(ethylene glycol) (PELA) blends were studied by DSC, SEM, and polarizing optical microscopy. The melting temperatures of PHB in the blends showed a slight shift, and the melting enthalpy of the blends decreased linearly with the increase of PELA content. The glass transition temperatures of PHB/PELA (60/40), (40/60), and (20/80) blends were found at about 30°C, close to that of the pure PELA component, during DSC heating runs for the original samples and samples after cooling from the melt at a rate of 20°C/min. After a DSC cooling run at a rate of 100°C/min, the blends showed glass transitions in the range of 10–30°C. Uniform distribution of two phases in the blends was observed by SEM. The crystallization of PHB in the blends from both the melt and the glassy state was affected by the PELA component. When crystallized from the melt during the DSC nonisothermal crystallization run at a rate of 20°C/min, the temperatures of crystallization decreased with the increase of PELA content. Compared with pure PHB, the cold crystallization peaks of PHB in the blends shifted to higher temperatures. Well-defined spherulites of PHB were found in both pure PHB and the blends with PHB content of 80 or 60%. The growth of spherulites of PHB in the blends was affected significantly by 60% PELA content. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 65: 1849–1856, 1997

Biodegradable polymer blends of poly(3-hydroxybutyrate) and starch acetate

The thermal behaviour and phase morphology of poly(3-hydroxybutyrate) (PHB) and starch acetate (SA) blends have been studied by differential scanning calorimetry, Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy and polarizing optical microscopy. PHB/SA blends were immiscible. The melting temperatures of PHB in the blends showed some shift with increase of SA content. The melting enthalpy of the PHB phase in the blend was close to the value for pure PHB. The glass transition temperatures of PHB in the blends remained constant at 9°C. The FTIR absorptions of hydroxyl groups of SA and carbonyl groups of PHB in the blends were found to be independent of the second component at 3470cm-1 and 1724cm-1, respectively. The crystallization of PHB was affected by the addition of the SA component both from the melt on cooling and from the glassy state on heating. The temperature and enthalpy of non-isothermal crystallization of PHB in the blends were much lower than those of pure PHB. The crystalline morphology of PHB crystallized from the melt under isothermal conditions varied with SA content. The cold crystallization peaks of PHB in the blends shifted to higher temperatures compared with that of pure PHB. ©1997 SCI

Biodegradable polymer blends of poly(3-hydroxybutyrate) and starch acetate

Biodegradable polymer blends of poly(3-hydroxybutyrate) and starch acetate

Biodegradable polymer blends of poly(3‐hydroxybutyrate) and starch acetate

The thermal behaviour and phase morphology of poly(3-hydroxybutyrate) (PHB) and starch acetate (SA) blends have been studied by differential scanning calorimetry, Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy and polarizing optical microscopy. PHB/SA blends were immiscible. The melting temperatures of PHB in the blends showed some shift with increase of SA content. The melting enthalpy of the PHB phase in the blend was close to the value for pure PHB. The glass transition temperatures of PHB in the blends remained constant at 9 degrees C. The FTIR absorptions of hydroxyl groups of SA and carbonyl groups of PHB in the blends were found to be independent of the second component at 3470 cm(-1) and 1724 cm(-1), respectively. The crystallization of PHB was affected by the addition of the SA component both from the melt on cooling and from the glassy state on heating. The temperature and enthalpy of non-isothermal crystallization of PHB in the blends were much lower than those of pure PHB. The crystalline morphology of PHB crystallized from the melt under isothermal conditions varied with SA content. The cold crystallization peaks of PHB in the blends shifted to higher temperatures compared with that of pure PHB.

Surface Analysis of Biodegradable Polymer Blends of Poly(sebacic anhydride) and Poly(dl-lactic acid)

The erosion behavior of blends of biodegradable polymers is determined by the chemical composition and the molecular organization of the surface of the material. Providing a comprehensive characterization of polymer blend surfaces requires a multi-instrumental approach, as no individual surface analysis technique can ascertain both the chemical and morphological nature of surfaces. In this study we have characterized the surfaces of immiscible and miscible blends of the biodegradable polymers poly(sebacic anhydride) (PSA) and poly(dl-lactic acid) (PLA) using the surface techniques of static secondary ion mass spectrometry (SSIMS), X-ray photoelectron spectroscopy (XPS), and atomic force microscopy (AFM). SSIMS and XPS have recorded the surface enrichment of all of the blends with the PLA component. For the immiscible blends, differential charging within the XPS spectra also provides evidence of phase separation. AFM data have contrasted the surface morphologies of the immiscible and miscible blends, and the use of in situ AFM techniques has enabled the effect of blend morphology on surface erosion to be visualized. For the immiscible systems, clear phase separation morphologies can be observed and at certain blend compositions the rapid loss of the PSA from the films results in the exposure of the PLA morphology. However, as the PLA content is increased, the surface enrichment effect results in the degradation behavior of the blend being dominated by the slow degrading PLA surface layer. For the miscible systems, the in situ AFM studies visualized a disintegration of the whole blend film without the exposure of a PLA morphology, indicating that the hydrolysis of the PSA component rendered the whole film unstable. The use of SIMS, XPS, and AFM, while highlighting the complexity of polymer blend surfaces, can provide a rapid analysis of the physicochemical phenomena underlying the organization of these systems and therefore should facilitate the application of such systems as biomaterials.

Processabilities and mechanical properties of surlyn‐treated starch/LDPE blends

AbstractThe esterification of the hydroxyl group of starch with DuPont Surlyn was considered as pretreatment method of starch before blending with polyolefins. In treating starch with Surlyn, two different raction conditions were taken to optimize reaction conditions. First, the esterification reaction was carried out in 110°C xylene with oleic acid as a catalyst. Second, the reaction out in a 90°C mixture of deionized water and xylene with ceric ammonium nitrate(CAN) as an initiator. Starch granules would be swollen above the gelatinization temperature in water. In both cases starch was midified by Surlyn to have good compatibility with low‐density polyethylene (LDPE). The mechanical and theological properties were examined for blends of the treated starch and LDPE. This system may be one of the biodegradable polymer blends that sufficiently retain properties as a packaging film.

Synthesis of a block copolymer of poly(3-hydroxybutyrate) and poly(ethylene glycol) and its application to biodegradable polymer blends

A block copolymer {P[(R,S)-HB-b-EG]} of atactic poly[(R,S)-3-hydroxybutyrate] {P[(R,S)-HB]} and poly(ethylene glycol) (PEG) was prepared by the ring-opening polymerization of β-butyrolactone in the presence of a macroinitiator (PEG/ZnEt2/H2O) which had been produced by the reaction of α,ω-dihydroxy PEG ( $$\overline M $$ n=3000) with ZnEt2/H2O (1/0.6) catalyst. The block copolymer ( $$\overline M $$ n=10,500, $$\overline M $$ w/ $$\overline M $$ n=1.2) was an A-B-A triblock copolymer comprising atactic P[(R,S)-HB] (A) and PEG (B) segments. The miscibility, physical properties, and biodegradability of binary blends of microbial poly[(R)-3-hydroxybutyrate] {P[(R)-HB]} with the block copolymer P[(R,S)-HB-b-EG] has been studied. The glass-transition temperature (T g) data showed that the P[(R)-HB]/P[(R,S)-HB-b-EG] blend was miscible in the amorphous state. The P[(R)-HB] film became flexible and tough by means of blending with P[(R,S)-HB-b-EG] block copolymer. The enzymatic degradation of blend films was carried out at 37°C and pH 7.4 in a 0.1M phosphate solution of an extracellular PHB depolymerase fromAlcaligenes faecalis. The enzymatic degradation took place solely on the surface of the blend films.