Thermoplastic Corn Starch Research Articles

Wplyw nanonapelniacza polimerowego o budowie rdzen-otoczka na strukture oraz wlasciwosci mieszaniny polilaktydu i termoplastycznej skrobi kukurydzianej

Wplyw nanonapelniacza polimerowego o budowie rdzen-otoczka na strukture oraz wlasciwosci mieszaniny polilaktydu i termoplastycznej skrobi kukurydzianej

Effect of corn starch content in thermoplastic starch/low‐density polyethylene blends on their mechanical and flow properties

AbstractThe aim of this work is to prepare low‐density polyethylene (LDPE)/thermoplastic corn starch (TPCS) compounds containing the highest amount of starch for biodegradable applications. It is intended to increase concentration of corn starch into LDPE without affecting basic required mechanical properties of LDPE plastics for disposable products. LDPE/TPCS blends containing different contents of TPCS (0–40 wt %) and a constant amount of LDPE grafted maleic anhydride [PE‐g‐MA (3 wt %)] are prepared using a single‐screw extruder. The prepared blends are evaluated for their mechanical, flow, and water absorption properties. Scanning electron micrographs of the samples show improvement in dispersion of the starch particles in LDPE matrix in the presence of PE‐g‐MA as a compatibilizer. The Young's modulus and impact strength properties reduce by increasing corn starch content in TPCS. The ultimate tensile strength and elongation at break of the samples show that the blends with 25 wt % TPCS have the required mechanical properties to produce plastic packaging products, as evidenced by ASTM D 4976‐04. The results of rheological tests indicate that as shear rate increases, the apparent viscosity of the blends decreases (shear thinning). The addition of starch to LDPE also decreases the melt flow index values of the samples. The water absorption of the samples increases with increasing starch concentrations at a constant time of water immersion. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012

Film processability and properties of polycaprolactone/thermoplastic starch blends

AbstractIn this work, the processing and properties of blown films prepared from thermoplastic corn starch (TPS) and polycaprolactone (PCL) were studied, in particular at high TPS content. The influence of processing parameters and material moisture content on the tensile properties was also studied. The results show that final film properties are mainly controlled by the draw ratio, blow‐up ratio and PCL concentration in the blends. The results also show that PCL/TPS films are less hydrophilic as PCL content increases. Finally, it was found that a very narrow processing window exists for this blend. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011.

Thermoplastic corn starch reinforced with cotton cellulose nanofibers

AbstractThis work evaluates the use of cotton cellulose nanofibers (CCN) as a reinforcing agent to prepare thermoplastic corn starch (TPS) matrix plasticized with 30 wt % of glycerol. The nanocomposites were filled with 0.5–5.0 wt % of CCN on a dry‐starch basis. The dried nanofibers were resuspended through the use of an ultrasonicator and then introduced in the fixed water formulation for obtaining TPS. The nanocomposites were compounded in a corotating twin‐screw extruder. Scanning transmission electron microscopy (STEM), field emission gun (FEG), X‐ray diffraction (XRD) and thermogravimetric analysis (TGA), in air atmosphere, were used to characterize nanofibers, neat TPS, and nanocomposites. The results showed that the nanofibers had needlelike structure with an average length of about 135 ± 50 nm and an average diameter of about 14 ± 4 nm. The addition of CCN was effective to enhance the mechanical properties of neat TPS in compositions above 2.5 wt %, although some agglomeration could be observed. The resulting nanocomposites showed good structural stability, because the amylopectin transcrystallization phenomena on the surface of nanofibers had not occurred. Only a slight decrease in the crystallinity index and a minor increase in the water absorption in relation to neat TPS were observed. An increase in the thermal stability of TPS nanocomposites with respect to neat TPS was verified, but it was independent of the CCN content. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011

Poly (butylensuccinate co-adipate)-thermoplastic starch nanocomposite blends

Nanocomposites based on blends of thermoplastic corn starch (TPS), plasticized with glycerol, and poly (butylensuccinate co-adipate) (PBAS) were prepared using sodium montmorillonite and organomodified montmorillonite. X-ray diffraction and scanning electron microscopy were used to study the clay dispersion. The effects of PBAS and clay type content on mechanical properties were evaluated. TPS/PBAS/organic modified montmorillonite shows an exfoliated nanocomposite structure and a notable increase of the modulus.

Thermoplastic corn starch/clay hybrids: Effect of clay type and content on physical properties

Thermoplastic corn starch (TPS) hybrids, plasticized with glycerol and reinforced with two types of clay (sodium montmorillonite and Cloisite ® 30B), were prepared by melt-extrusion. Scanning electron microscopy was used to visualize extrudates morphology. The effects of clay content and of glycerol content on the physical properties of extrudates were evaluated. As determined by contact angle measurements and X-ray diffraction, the increase in glycerol content led to materials with higher hydrophilicity, and higher B-type crystallinity. Addition of clay resulted in hybrid materials with improved properties in relation to TPS alone, even after conditioning at a high relative humidity for 90 days. X-ray diffraction was also used to evaluate clay intercalation within the polymeric matrix, before and after conditioning. Soil burial biodegradation tests, carried out for TPS alone and for TPS/Cloisite 30B hybrids, and followed by weight loss measurements, revealed that biodegradation was enhanced for the hybrid materials in comparison with TPS.

The plasticizing effect of alginate on the thermoplastic starch/glycerin blends

Corn starch and corn starch–alginate (5–15%) blends plasticized with 35% glycerin were prepared, water was intentionally excluded from the formulations. Torque rheometry measurements were carried out during the processing of the blends in a batch counterrotating twin screw mixer. A progressive decrease in the plasticization energy of the blends was observed as the alginate content was increased, with a 5-fold decrease for the blend with the higher alginate content (15%). The steady state torque of the plasticized melted blends also showed a decrease as alginate content was increased; with a drastic drop occurring for the formulation with higher alginate content. After mixing, test specimens for mechanical, thermal and microstructural testing were made by compression molding. A decrease in the elastic properties and an increase in elongation at break and impact resistance was observed when alginate content was increased in the blends. The transition of the materials towards a more viscous behavior, as alginate content was increased, was confirmed by differential scan calorimetric analysis. For the corn starch–alginate blends glass transitions were detected in the temperature range −60 to −90 °C. Scanning electron microscopy was used to examine the morphology of cryofractured surfaces of the molded test specimens. A reduction of the granular crystalline structures typical of corn starch was observed as alginate content was increased in the blends. The experimental evidence presented in this work indicates that, when water is excluded from thermoplastic corn starch preparation, alginate acts synergistically with glycerin increasing the degree and efficiency of the plasticization process.

High mechanical performance MMT-urea and formamide-plasticized thermoplastic cornstarch biodegradable nanocomposites

Biodegradable nanocomposites have been successfully fabricated from the thermoplastic cornstarch (TPCS) and activated-montmorillonite (MMT) by melt-intercalation. TPCS was plasticized with novel plasticizers urea and formamide, and the activated-montmorillonites were obtained using citric acid as the activated solvent. Compared with urea and formamide-plasticized thermoplastic cornstarch (UFTPCS), the mechanical properties of nanocomposites were very good. The thermal analysis was investigated by Differential Scanning Calorimetry (DSC). The effect of water content on the mechanical properties of nanocomposites was studied. Dynamic Mechanical Thermal Analysis (DMTA) was also carried out. The structure and morphology of biodegradable nanocomposites were characterized by wide-angle X-ray diffraction (WAXD), scanning electron microscope (SEM) and transmission electron microscope (TEM). It was revealed that UFTPCS were intercalated into the layers of MMT successfully, and layers of MMT were fully exfoliated and so formed the exfoliated nanocomposites with MMT. This manufacturing process is simple and environmentally friendly.

Structure and properties of thermoplastic corn starch/montmorillonite biodegradable composites

Abstract“Green” composites were successfully prepared from the thermoplastic cornstarch (TPCS) and activated‐montmorillonite (MMT) by the method of blend extrusion. The thermoplastic cornstarch was plasticized with novel plasticizers urea and ethanolamine, and the activated‐montmorillonites were obtained using ethanolamine as the activated solvent. The structure and morphology of “Green” composites were characterized by wide‐angle X‐ray diffraction (WAXD), scanning electron microscope (SEM), and transmission electron microscope (TEM). SEM and TEM images indicated that the composites presented reticulating fiber structure after being cooled by liquid nitrogen. The exfoliated MMT sheets in the composites acted as the inhomogeneous nucleation effect. The melting urea was crystaled over on the MMT sheets in the inducement of ethanolamine, and the column‐shape crystal whisker overlapped together. Comparing with normal temperature, the mechanical properties of composites evidently improved after being cooled by liquid nitrogen, which was proved by the mechanical testing. The thermal stability and water‐resistance of the composites also were studied in this paper. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 99: 170–176, 2006

Effect of chitin addition on injection‐molded thermoplastic corn starch

AbstractA new type of biodegradable starch‐based composites was prepared by injection‐molding using glycerol and water as plasticizers. Chitin flakes, obtained from shells of Penaeusschmitti, were used as reinforcing phase. The effect of chitin content on the structural and tensile properties of the composite samples was examined after conditioning at 28°C and 80% relative humidity for 30 days. In general, chitin incorporation into the starch matrix resulted in materials with higher modulus and decreased elongation at break. Wide‐angle X‐ray diffraction and differential scanning calorimetry evidenced a significant decrease in crystallinity in the composite samples in relation to the unfilled starch material. Contact angle measurements revealed that the addition of chitin contributes to the improvement of water resistance of the composite samples when compared to injection molded starch alone. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 2706–2713, 2004

Redução da hidrofilicidade de filmes biodegradáveis à base de amido por meio de polimerização por plasma

Devido ao baixo custo de produção e excelente biodegradabilidade, o amido constitui-se em matéria-prima promissora para a produção de plásticos biodegradáveis. No entanto, a grande hidrofilicidade dos filmes à base de amido representa uma séria limitação tecnológica à sua comercialização, uma vez que as propriedades dos filmes são afetadas pela variação da umidade relativa do ar durante a sua estocagem ou o seu uso. Neste trabalho, filmes de amido termoplástico foram recobertos com uma fina camada protetora polimérica gerada por intermédio da tecnologia de plasma frio. 1-Buteno e 1,3-butadieno foram utilizados como monômeros para a polimerização por plasma. Os filmes recobertos apresentaram uma redução de até 80% na absorção de água e aumento do ângulo de contato em relação à água. Estes resultados indicaram uma redução significativa na natureza hidrofílica do material à base de amido após o recobrimento.

Biodegradable compositions by reactive processing of aliphatic polyester/polysaccharide blends

AbstractCommercially available biodegradable aliphatic polyesters, i.e., high molecular weight poly(ϵ‐caprolactone) (PCL) and polylactide (PLA), were melt blended with a well‐known natural and biodegradable polysaccharide: starch either as corn starch granules or as thermoplastic corn starch after plasticization with glycerol. Conventional melt blending yielded compositions with poor mechanical performances as a result of lack of interfacial adhesion between the rather hydrophobic polyester matrix and the highly hydrophilic and moisture sensitive starch phase. Interface compatibilization was achieved via two different strategies depending on the nature of the polyester chains. In case of PLA/starch compositions, PLA chains were grafted with maleic anhydride through a free radical reaction conducted by reactive extrusion. The maleic anhydride‐grafted PLA chains (MAG‐PLA) allowed for reinforcing the interfacial adhesion with granular starch as attested by TEM of cryofracture surface. As far as PCL/starch blends were concerned, the compatibilization was achieved via the interfacial localization of amphiphilic graft copolymers formed by grafting of PCL chains onto a polysaccharide backbone such as dextran. The PCL‐grafted polysaccharide copolymers were synthesized by controlled ring‐opening polymerization of ϵ‐caprolactone proceeding via a coordination‐insertion mechanism. These compatibilized PCL/starch compositions displayed much improved mechanical properties as determined by tensile testing as well as a much more rapid biodegradation as measured by composting testing.