Tensile properties,morphology, and biodegradability of blends of starch with various thermoplastics

In the present study, blends of starch with different thermoplastics were prepared by a melt blending technique. The tensile properties and morphology of the blends were measured. It was found that with increasing starch content in starch/ionomer blends, the tensile strength and modulus increase. But for starch/low‐density polyethylene (LDPE) and starch/aliphatic polyester (APES) blends, tensile strength and modulus decrease with increasing the starch loading. Elongation at break values of all the blend systems decrease with increasing starch loading. The scanning electron micrographs (SEM) support the findings of tensile properties. Better homogeneity is observed in starch/ionomer systems compared with that in starch/APES and starch/LDPE systems. Up to 50% starch content, the starch/ionomer blends appear as a single phase. The extent of phase interactions of starch/APES system lies in between the starch/LDPE and starch/ionomer systems. From the biodegradability studies of the blends it was found that, although the pure LDPE and ionomer are not biodegradable, the starch/LDPE and starch/ionomer blends are biodegradable with an appreciable rate. The rate of biodegradation of the starch/APES is very high as both the components are biodegradable. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 2907–2915, 2002     

Biodegradability,mechanical properties,melt flow index,and morphology of polypropylene/amylose/amylose‐ester blends

We blended polypropylene (PP) with amylose (AM) and/or dodecanoyl ester of amylose (DODAM) in an effort to make it biodegradable. The content of AM/DODAM was varied from 0 to 40% in the blends. The biodegradability, mechanical properties, melt flow indexes (MFIs), and morphologies of the blends were studied. Biodegradability increased with increases in AM/DODAM content. It was found to be dependent on DODAM content and was at a maximum in blends containing 40% AM + DODAM. Blends with no DODAM or 2.5% DODAM showed almost no adherence of the phases. Dispersion of AM improved in blends with 5% DODAM, and it showed satisfactory adherence to PP also. The tensile strength, elongation at break, and Izod impact strength decreased with increasing AM content. However, in blends with both AM and DODAM, all these properties, especially the elongation at break, showed improvements. The same trend was observed for MFI. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 1434–1442, 2002     

Effects of polyethylene‐grafted maleic anhydride (PE‐g‐MA) on thermal properties,morphology, and tensile properties of low‐density polyethylene (LDPE) and corn starch blends

The effects of polyethylene‐grafted maleic anhydride (PE‐g‐MA) on the thermal properties, morphology, and tensile properties of blends of low‐density polyethylene (LDPE) and corn starch were studied with a differential scanning calorimeter (DSC), scanning electron microscope (SEM), and Instron Universal Testing Machine, respectively. Corn starch–LDPE blends with different starch content and with or without the addition of PE‐g‐MA were prepared with a lab‐scale twin‐screw extruder. The crystallization temperature of LDPE–corn starch–PE‐g‐MA blends was similar to that of pure LDPE but higher than that of LDPE–corn starch blends. The interfacial properties between corn starch and LDPE were improved after PE‐g‐MA addition, as evidenced by the structure morphology revealed by SEM. The tensile strength and elongation at break of corn starch–LDPE–PE‐g‐MA blends were greater than those of LDPE–corn starch blends, and their differences became more pronounced at higher starch contents. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 2904–2911, 2003     

Novel biodegradable low-density polyethylene–poly(lactic acid)–starch ternary blends

The ternary powder blends based on low-density polyethylene (LDPE) and two polymers of natural origin poly(lactic acid) (PLA) and starch are obtained in a rotor disperser under conditions of shear deformations. The dependence of the final powder dispersity on the composition is explored. A comparative analysis of the mechanical properties of the ternary blends with those of the LDPE–PLA and PLA–starch binary blends previously obtained has revealed that the presence of two rigid polymers PLA and starch leads to an increase in the elastic modulus and a decrease in the tensile strength and elongation at break. In the study of the blend biodegradability, it is found that the presence of two polymers of natural origin in the system with a total mass fraction of 60% promotes intensive biodegradation.     

Effects of glycerol and PE‐g‐MA on morphology,thermal and tensile properties of LDPE and rice starch blends

The effects of glycerol and polyethylene‐grafted maleic anhydride (PE‐g‐MA) on the morphology, thermal properties, and tensile properties of low‐density polyethylene (LDPE) and rice starch blends were studied by scanning electron microscopy (SEM), differential scanning calorimetry, and the Instron Universal Testing Machine, respectively. Blends of LDPE/rice starch, LDPE/rice starch/glycerol, and LDPE/rice starch/glycerol/PE‐g‐MA with different starch contents were prepared by using a laboratory scale twin‐screw extruder. The distribution of rice starch in LDPE matrix became homogenous after the addition of glycerol. The interfacial adhesion between rice starch and LDPE was improved by the addition of PE‐g‐MA as demonstrated by SEM. The crystallization temperatures of LDPE/rice starch/glycerol blends and LDPE/rice starch/glycerol/PE‐g‐MA blends were similar to that of pure LDPE but higher than that of LDPE/rice starch blends. Both the tensile strength and the elongation at break followed the order of rice starch/LDPE/glycerol/PE‐g‐MA blends > rice starch/LDPE/glycerol > LDPE/rice starch blends. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 344–350, 2004     

Effect of cellulose nanofibers and acetylated cellulose nanofibers on the properties of low‐density polyethylene/thermoplastic starch blends

The aim of this study was to evaluate the effect of cellulose nanofibers (CNFs) and acetylated cellulose nanofibers (ACNFs) on the properties of low‐density polyethylene/thermoplastic starch/polyethylene‐grafted maleic anhydride (LDPE/TPS/PE‐g‐MA) blends. For this purpose, CNFs, isolated from wheat straw fibers, were first acetylated using acetic anhydride in order to modify their hydrophilicity. Afterwards, LDPE/TPS/PE‐g‐MA blends were reinforced using either CNFs or ACNFs at various concentrations (1–5 wt%) with a twin‐screw extruder. The mechanical results demonstrated that addition of ACNFs more significantly improved the ultimate tensile strength and Young's modulus of blends than addition of CNFs, albeit elongation at break of both reinforced blends decreased compared with the neat sample. Additionally, biodegradability and water absorption capacity of blends improved due to the incorporation of both nanofibers, these effects being more pronounced for CNF‐assisted blends than ACNF‐reinforced counterparts. © 2018 Society of Chemical Industry     

Preparation and characterization of LDPE/starch blends containing ethylene/vinyl acetate copolymer as compatibilizer

A series of LDPE blends with plasticized (PLST) and granular starch (FILST) were prepared. Ethylene/vinyl acetate (EVA) copolymer was used as a compatibilizer in three different amounts: 10, 25 and 50 wt% based on starch. The blends were studied by Fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), and thermogravimetric analysis (TGA). Second derivative IR spectra showed peak shifts similar to those observed in V-type starch complexes with ethylene/vinyl alcohol copolymers. The possibility for V-type complex formation is supported by the lower biodegradation rates of the blends containing higher amounts of EVA. Mechanical properties of the blends, especially elongation at break, were satisfactory even for blends containing high amounts of starch (20–30 wt%).     

Effect of propylation of starch with different degrees of substitution on the properties and characteristics of starch‐low density polyethylene blend films

Corn starch was modified by propylation and degree of substitution (DS) of four starch modifications were 0.61, 1.56, 2.27, and 2.51. Different films were prepared by blending native and propylated starch with low‐density polyethylene (LDPE). The mechanical properties, thermal properties, water absorption capacity, and biodegradability of the blend films varied with the quantity of starch as well as DS. Tensile strength, elongation, and melt flow index of propylated starch blend films were higher compared to the corresponding native starch blend film. These properties improved with increase in DS from 1.56 to 2.51. Propylated starch blend films were found thermally stable than native starch blend films. There was a decrease in water absorption capacity for the films containing propylated starch at high DS. Enzymatic and soil burial degradation results showed that biodegradability of starch‐LDPE films increased with the increase in the starch concentration but it decreased with increase in the DS. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011.     

Effect of Morphology on the Biodegradation of Thermoplastic Starch in LDPE/TPS Blends

In this study, thermoplastic starch (TPS) was mixed with low density polyethylene with different melt flow indexes in a one-step extrusion process to produce LDPE/TPS blends varied from 32% to 62% by weight of TPS. The influence of starch content and LDPE viscosity on morphology, biodegradation and tensile properties of LDPE/TPS blends were evaluated. Starch continuity and biodegradability were studied by hydrolytic, enzymatic and bacterial degradation. The LDPE viscosity had a considerable effect on the morphology and the connectivity of the starch particles. Evaluation of hydrolytic extraction showed that blends having TPS content above 50 wt% possessed a full connectivity. Studies of biodegradation indicated that the bacterial attack on starch resulted in weight loss of TPS of 92%, 39% and 22%, for PE1/TPS having 62% and 32% TPS, and PE2/TPS (31% TPS), respectively. Comparatively, the weight loss was more significant at 100%, 66% and 31% by hydrolytic extraction. Differences between these two techniques were discussed in terms of the accessibility of starch domains to microorganisms. Tensile properties (ε_b and E) decreased with increasing exposure time to activated sludge. Changes in tensile properties were highly dependent on the biodegradation rate. PE1/TPS blends having 32% starch remained ductile after 45 days of exposure to bacterial attack.     

Fabrication and characterisation of thermoplastic starch/poly(butylene succinate) blends with maleated poly(butylene succinate) as compatibiliser

Thermoplastic starch/poly(butylene succinate) (TPS/PBS), an entirely biodegradable polymer blend, was prepared by a two-step extrusion method. Maleic anhydride grafted PBS (rPBS) was successfully synthesised as an interfacial compatibiliser. The miscibility, morphology, thermal behaviour and mechanical properties of the TPS/PBS blends were investigated. The results demonstrated that the strength and elongation at break of TPS/PBS blends were greatly increased with the addition of rPBS in PBS blends due to improved interfacial miscibility. Better distribution and smaller phase domain were observed in the blends with higher content of compatibilisers. The water resistance was also enhanced by incorporation of rPBS. It was indicated that compatibilised TPS/PBS blends possessed a combination of good biodegradability, improved strength and high water resistance. TPS/PBS blend was expected to serve as a promising packing material.     

改性淀粉/LLDPE共混体系生物降解材料性能的研究

将自制接枝改性淀粉与LLDPE、玉米淀粉以及另外两种相容剂进行共混。通过对共混体系的形态结构、力学性能、流变性能、热性能以及对共混物薄膜的生物降解性能等的研究说明:复合相容剂MAH-g-PE+LA-g-starch的加入改善了淀粉和LLDPE的相容性,使得共混物体系具有适宜的拉伸强度及断裂伸长率;LLDPE/淀粉/(MAH-g-PE+LA-g-starch)共混物薄膜具有很好的生物降解性能。     

Biodegradable extruded starch blends

We prepared biodegradable extruded starch blends by first mixing starch with additives and then processing the mixture in an extruder. The mechanical properties, including tensile strength and elongation at break, solubility, biodegradability, rheological properties, molecular weight, and glass‐transition temperature of the extruded blends were studied. Glycerol and urea, to some extent, could both decrease the tensile strength and increase the percentage elongation at break because the former acts as a plasticizer and the latter can break down interactions among starch macromolecules. The extruded starch blends showed thermoplasticity, and their melts behaved as pseudoplastic liquids at a comparatively low shear rate. The biodegradability of the extruded starch was slightly higher than that of native starch. The molecular weight of starch displayed a decreasing tendency after extruding modification. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 627–635, 2003     

PPA在LLDPE/LDPE薄膜加工中的应用

本工作以ＬＬＤＰＥ／ＬＤＰＥ共混树脂为基料，添加氟弹性体ＰＰＡ加工改性剂，采用挤出吹塑成型加工薄膜制品．ＬＬＤＰＥ／ＬＤＰＥ＝１／２为空白．添加５００ＰＰＭ的ＰＰＡ后，共混物中ＬＬＤＰＥ为１／３时，挤出机电流下降，薄膜的透光率增加，雾度降低；ＬＬＤＰＥ含量为６０％时，挤出机电流未变而产量提高，薄膜的透光率和雾度变化不大；继续增加ＬＬＤＰＥ比例时，挤出机电流和薄膜雾度增加．薄膜的拉伸性质随ＬＬＤＰＥ比例增大而显著提高，且纵横向的取向性变小．     

Effect of thermal aging on the biodegradation of PCL,PHB‐V,and their blends with starch in soil compost

Different proportions of starch were blended with poly(β‐hydroxybutyrate)‐co‐poly(β‐hydroxyvalerate) (PHB‐V) or poly(ε‐caprolactone) (PCL) by extrusion, and the mechanical (maximum tensile strength, elongation at break and Young's modulus) and thermal properties (by differential scanning calorimetry) were determined. The biodegradability of the blends in soil compost was also assessed after thermal aging for 192, 425, and 600 h at different temperatures. The maximum tensile strength of the PCL50 blend (containing 50% starch) was 35% lower than that of PCL and that of the PHB‐V50 blend was 60% lower than that of PHB‐V without thermal aging. PHB‐V blends were more biodegradable than PCL blends. For the blends prepared, only the biodegradation of PHB‐V25 was affected by thermal aging. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 3539–3546, 2003     

Compatibilizing Effect of SEBS for Electrical Properties of LDPE/PS Blends

Summary: In the previous study, we observed compatibilizing effects of low density polyethylene (LDPE)/polystyrene (PS) with polystyrene‐block‐poly(ethylene‐co‐butylene)‐block‐polystyrene (SEBS), a triblock copolymer. Blends consisting of 70 wt.‐% LDPE and 30 wt.‐% PS were prepared with a SEBS concentration of up to 10 wt.‐%. This study examined the electrical properties such as the electrical breakdown, water tree length, permittivity and tan δ in the blends. The possibility of using these blends as insulating material substitutes for LDPE was investigated. The electrical breakdown strength reached a maximum of 66.67 kV/mm, which is superior to 50.27 kV/mm of the LDPE used as electrical insulators for cables. In addition, the water tree length decreased with increasing SEBS concentration. The water tree lengths of the blends containing SEBS were shorter than that of the LDPE. The permittivity of the blends was 2.28–2.48 F/m, and decreased with increasing SEBS concentration with the exception of S‐0. Tan δ of the blends increased smoothly with increasing SEBS content.

Breakdown strength , water tree length, permittivity and tan δ of the LDPE/PS/SEBS blends and raw materials.     

LDPE/starch blends compatibilized with PE-g-MA copolymers

In the present study, low-density polyethylene (LDPE) and plasticized starch (PLST) blends, containing different percentages of PLST, were prepared. In these blends, two different polyethylene/maleic anhydride graft (PE-g-MA) copolymers containing 0.4 and 0.8 mol % anhydride groups, respectively, were added as compatibilizers at 10 wt % PLST. The compatibilization reaction was followed by FTIR spectroscopy. The morphology of the blends was studied using scanning electron microscopy (SEM). It was found that as the amount of anhydride groups in the copolymers increases a finer dispersion of PLST in the LDPE matrix is achieved. This is reflected in the mechanical properties of the blends and especially in the tensile strength. The blends compatibilized with the PE-g-MA copolymer containing 0.8 mol % anhydride groups have a higher tensile strength, which in all blends, even in those containing 20 and 30 wt % PLST, is similar to that of pure LDPE. The biodegradation of the blends followed the exposure to activated sludge. It was found that the compatibilized blends have only a slightly lower biodegradation rate compared to the uncompatibilized blends. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 70: 1503–1521, 1998     

Biodegradation of low‐density polyethylene/thermoplastic starch foams before and after electron beam irradiation

Foamy low‐density polyethylene/plasticized starch (LDPE/PLST) blends at different compositions were produced in the presence of azodicarbonamide (ACA) compound as foaming agent. The LDPE/PLST blends before and after electron beam irradiation were investigated in terms of mechanical properties, bulk density, and structure morphology. Moreover, the biodegradability of these materials was evaluated by the soil burial test for 2 months, in which the buried sheets were also examined by scanning electron microscopy (SEM). The results showed that the increase of PLST content from 24 to 30% was accompanied by a decrease in the yield and break stresses of 10 and 20% for the unirradiated blends without the foaming agent, respectively. Further decrease in these mechanical parameters was observed after the foaming process. The bulk density, void fraction, cell size measurements as well as the examination by SEM illustrate clearly the cell growth of the foam structure. The soil burial test and SEM micrographs indicate the growth of microorganisms overall the blend sheets and that the blend was completely damaged after two months of burying. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

Mechanical properties and biodegradability of LDPE blends with fatty‐acid esters of amylose and starch

In the present article a series of low‐density polyethylene (LDPE) blends with different amounts of fatty esters of amylose and starch, were prepared in a Haake‐Buchler Reomixer. The tensile as well as the dynamic thermomechanical (DMTA) properties of the blends were measured. It was found that as the amount of the esters increases in the blends, the tensile strength and especially the elongation at break decrease nonlinearly. Scanning electron microscopy (SEM) was used to assess the interfacial adhesion between LDPE and the corresponding esters. The incompatibility of the blends was also verified with DMTA and differential scanning calorimetry (DSC). From the biodegradation studies of the blends during exposure in activated sludge, it was found that all esters are biodegradable, although to a much lesser degree compared to pure strach. The biodegradation rate of the composites is relatively small due to the low biodegradation rate of the pure esters. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 71: 1089–1100, 1999     

Use of poly(ethylene‐co‐vinyl alcohol) as compatibilizer in LDPE/thermoplastic tapioca starch blends

Poly(ethylene‐co‐vinyl alcohol) (EVOH) was used as a compatibilizer to make blends of low‐density polyethylene (LDPE) and plasticized starch (TS). The tensile properties and impact strength were measured and compared with those of neat LDPE. The morphology of the blend specimens, both fractured and unfractured, was observed by scanning electron microscopy. Comparison of the properties showed that the impact strength of the blend improves significantly by the addition of a compatibilizer even with a high TS loading of 40 and 50% (by weight). A high elongation at break almost matching that of neat polyethylene was also obtained. The blend morphology of the etched specimens revealed fine dispersion of the starch in the polyethylene matrix, while the fracture surface morphology clearly indicate that the failure of compatibilized blends occurs mainly by the ductile mode. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 3126–3134, 2002     

Biodegradability Studies on LDPE-Starch Blends Using Amylase-Producing Vibrios

Low-density polyethylene, (LDPE) was mixed with two grades of tapioca starch–low-grade and high-grade. Various compositions were prepared and mechanical and thermal studies performed. The biodegradability of these samples was checked using a culture medium containing Vibrios (an amylase-producing bacteria), which was isolated from a marine benthic environment. The soil burial test and reprocessability of these samples were checked. The studies on biodegradability show that these blends are partially biodegradable. These low-density polyethylene-starch blends are reprocessable without sacrificing much of their mechanical properties.