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Derivatives/starch Blends (starch + blend)
Selected AbstractsCreep behavior of biocomposites based on sisal fiber reinforced cellulose derivatives/starch blendsPOLYMER COMPOSITES, Issue 3 2004Vera A. Alvarez Biodegradable composites based on cellulose derivatives/starch blends reinforced with sisal short fibers were fabricated by injection molding. Results of short-term flexural creep tests are reported to investigate the time-dependence behavior of the composites. Fiber content and temperature effects are also considered, taking into account various methods and equations. At short times, a creep power law is employed. A master curve with the Arrhenius model is used to determine the creep resistance at longer times and different temperatures. Good fitting of the experimental results with the four-parameter model is reported, leading to a relationship between the observed creep behavior and the composite morphology. The addition of sisal fibers to the polymeric matrix promotes a significant improvement of the composite creep resistance. Polym. Compos. 25:280,288, 2004. © 2004 Society of Plastics Engineers. [source] Dissolution and Enzymatic Degradation Studies Before and After Artificial Ageing of Silk- or Linen-Reinforced Gelatin Laminates, 1MACROMOLECULAR MATERIALS & ENGINEERING, Issue 5 2003M. Boyanova Abstract In an attempt to overcome the poor mechanical properties of native, i.e., untreated gelatin, laminates based on gelatin and gelatin/starch blend reinforced with fabrics (linen or silk) were prepared by melt pressing. The mechanical properties of fresh and artificially aged samples were reported previously. In the present series of two consecutive papers we present data concerning the dissolution and biodegradation of these laminates. A two-step procedure for treatment of the laminates was used. The first step is treatment with an aqueous buffer solution, the second with a buffered solution of the enzyme subtilisin. The time-course of the absorbance at 280 nm of the "washing" solutions was followed. A number of kinetic characteristics was determined and discussed with respect to laminate composition and their treatments. In the present Part 1 about the environmental behavior of these new biodegradable materials, the non-enzymatic solubilization in water and buffer solution (i.e., simple dissolution) of fresh and artificially aged samples is described. The dissolution process was followed spectrophotometrically as well as by the weight losses. It was found that gelatin-based silk- or linen-reinforced laminates were subject to dissolution, similarly to the gelatin and gelatin-based materials studied in previous works. In addition, it was established that the thermal treatment of the laminates during their melt pressing leads to postcondensation reactions and crosslinking of the gelatin macromolecules. Similar reactions occur between the matrix and the reinforcing element silk, thus improving their mutual adhesion. Decreased gelatin dissolution ability was observed after the thermal treatment, in the presence of reinforced fabrics and upon "additional" crosslinking with methylenedi(p -phenyl) diisocyanate. The untreated gelatin is the only one that dissolves completely in water. The artificially aged samples tend to dissolve better than the respective fresh samples due to degradation processes during aging. [source] Influence of melt drawing on the morphology of one- and two-step processed LDPE/thermoplastic starch blendsADVANCES IN POLYMER TECHNOLOGY, Issue 4 2003F. J. Rodriguez-Gonzalez Abstract In this study the morphology of LDPE/TPS blends prepared by a one-step extrusion process is compared to that obtained by reprocessing of the original blends. The influence of composition and melt drawing is examined. A novel methodology based on the form factor of the dispersed particle was used to estimate the equivalent spherical particle size of dispersed thermoplastic starch (TPS). This approach allows for the quantitative comparison of average dispersed phase particles regardless of their shape. Blends prepared in the one-step extrusion process show increased levels of anisotropy as a consequence of a combination of coalescence and particle deformation during melt drawing. Reprocessed materials demonstrate morphologies that are highly stable to a wide range of hot stretch ratio conditions. The TPS particles of reprocessed blends show no coalescence and a low degree of deformation. This phenomenon is explained by plasticizer evaporation resulting from the second processing step. The TPS is transformed from a highly deformable phase to one resembling a partially cross-linked material. These data indicate that the one-step processing of LDPE/TPS blends can be used to generate a wide range of highly elongated morphological structures. A two-step approach, analogous to typical compounding and shaping operations and involving controlled glycerol removal in the second step can be used to prepare a wide range of highly stable, more isotropic, dispersed particle morphologies. © 2003 Wiley Periodicals, Inc. Adv Polym Techn 22: 297,305, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/adv.10057 [source] Effect of epoxy functionalized compatibilizer on the mechanical properties of low-density polyethylene/plasticized tapioca starch blendsPOLYMER INTERNATIONAL, Issue 12 2001N Sailaja Abstract A series of low-density polyethylene (LDPE) blends with varying proportions of plasticized tapioca starch have been used for the study of their mechanical properties. A functionalized epoxy resin, namely, poly(ethylene- co -glycidyl methacrylate) has been used as the compatibilizer. The impact and tensile properties have been measured by standard ASTM methods. The mechanical properties are seen to improve significantly with the addition of the epoxy compatibilizer, approaching values close to those of virgin LDPE. The scanning electron micrographs of the compatibilized blends show ductile failure which evidently contribute to improved mechanical properties. © 2001 Society of Chemical Industry [source] Effect of poly(acrylic acid)-g-PCL microstructure on the mechanical properties of starch/PCL blend compatibilized with poly(acrylic acid)-g-PCLPOLYMER ENGINEERING & SCIENCE, Issue 3 2001Chang-Hyeon Kim Poly(acrylic acid)-g-polycaprolactone (PAA-g-PCL) graft copolymer was synthesized and starch/PCL blends compatibilized with PAA-g-PCL were prepared. The mechanical properties of the starch/PCL blends compatibilized with various PAA-g-PCLs that have different graft degrees and graft lengths were investigated. As the graft degree of the PAA-g-PCLs that have the same graft length increased, the modulus and the strength of the blends decreased. However, the elongation at break and the tensile toughness of the blends showed a maximum at a certain graft degree (10.8 mol%) owing to the better compatibilizing effect compared to the low (3.9 mol%) and the high (23.4 mol%) graft degree of PAA-g-PCL. It was also found that the modulus and the strength of the blends increased with the increase of graft length of the PAA-g-PCLs that have the same graft degree (,11 mol%). However, the blend compatibilized with the short graft length (M.W. of PCL graft: 530) exhibited the highest value of the elongation at break and the tensile toughness. This result is attributed to the self-crystallization of PAA-g-PCL in the blend that has longer PCL grafts. [source] Improving the Processing Ability and Mechanical Strength of Starch/Poly(vinyl alcohol) Blends through Plasma and Acid ModificationMACROMOLECULAR SYMPOSIA, Issue 1 2008Sung-Yeng Yang Abstract Summary: In this study, maleic anhydride (MA), and citric acid (CA) used as the processing additive and plasma treatment to improve the processing ability and mechanical strength of biodegradable starch/poly (vinyl alcohol) (PVA) blends were studied. The melt flow index (MFI) of starch/ glycerol/PVA (300g/60g/80g) blend was increased from 2.3g/10min to 32.7g/10min by adding 3g of MA and to 130 g/10min by adding MA and plasma treatment. The tensile strength of starch/glycerol/PVA blend increased from 3.48 to 6.21 MPa by adding 1.5g of MA and 1.5g of CA, while it increased to 6.26 MPa by plasma treatment. Esterification reaction which was evidenced by FTIR has been showed to improve the compatibility between starch and PVA when MA was dissolved into glycerol and glycerol grafted onto plasma pretreatment PVA. Thermogravimetric analysis (TGA) and scanning electron microscopy (SEM) imaging were used to study the morphology of extruded blends. [source] Study of pseudo-multilayer structures based on starch-polycaprolactone extruded blendsPOLYMER ENGINEERING & SCIENCE, Issue 6 2009Laurent Bélard This article is focused on the analysis of the structure-process relationships of biodegradable materials. It is mainly focused on the analysis of phase separation phenomenon occurring during the extrusion of plasticized starch/polycaprolactone blends, in a slit die. Rheological characterizations are carried out, in-line in an instrumented slit die at the exit of the extruder and, out-line with different rheometers. In certain conditions, a pseudo-multilayer structure can be generated with a polyester rich skin. Then, Electron Spectroscopy for Chemical Analysis (ESCA) and Fourier Transformed Infrared Attenuated Total Reflectance (FTIR-ATR) analyses are conducted to evaluate semi-quantitatively the polyester surface enrichment. In the range of available shear rates, the phase separation is mainly driven by the molecular weight of polycaprolactone, linked to its molten state viscosity. Three zones of surface enrichment, dependent on the molecular weights, are identified. Above 60,000 g·mol,1, no surface enrichment could be detected; below 37,000 g·mol,1, the phase separation occurs with no dependence on the processing conditions; between these two limits, the phase separation depends on both, the formulation and the processing conditions. A correlation between the rheological measurements and the phase separation is given. A predictive criterion based on the viscous behavior of the blend is established. POLYM. ENG. SCI., 2009. © 2009 Society of Plastics Engineers [source] | ||||||||||