Influence of thermoplastic starch plasticized with biodiesel glycerol on thermal properties of pp blends

Plastics have been used in short-life products, which have presented harmful consequences for the nature, because of the low degradation rate reached by the most common polyolefins. This work evaluates the mechanical and thermal properties of pure iPP, plasticized starch (TPS) with biodiesel (TPS_Bio) or commercial (TPS_Com) glycerols, and their blends (iPP/TPS_Plas). The addition of TPS_Plas caused an increasing on the cristallinity of iPP, mainly for the compositions 90/10 and 80/20, probably due to morphological alterations such as crosslinking, that may have modified the molecular arrangement of the iPP in the presence of glycerol.     

Influence of various starch types on PCL/starch blends anaerobic biodegradation

Research concentrated on the biodegradable capability of PCL blends with various types of starch in an anaerobic aqueous environment of mesophilic sludge from a municipal wastewater treatment plant. For blend preparation, use was made of a native starch Meritena from maize, another from Waxy – a genetically modified type of maize, as well as Gel Instant, a gelatinized starch, and an amaranth starch. Additional PCL/starch blends were prepared from the same starch types, but these were initially plasticized with glycerol. The biodegradability tests were supplemented with thermo gravimetric analysis (TGA), and differential scanning calorimetry (DSC); morphology was identified using scanning electron microscopy (SEM), plus mechanical properties were also tested. While mixtures of PCL with starches plasticized with glycerol exhibited improved mechanical properties and a higher degree of biodegradation in the anaerobic environment, mixtures of PCL with pure forms of starch were ascertained as rather resistant to the anaerobic aqueous environment. TGA and DSC analysis confirmed the removal of starch and glycerol from the PCL matrix. SEM then proved these results through the absence of starch grains in the samples following anaerobic biodegradation.     

Phase morphology of iPP/aPS/SEP blends

Supermolecular structure and phase morphology of the ternary isotactic polypropylene/atactic polystyrene/poly(styrene-b-ethylene-co-propylene) (iPP/aPS/SEP) compression molded blends with 100/0, 90/10, 70/30, and 50/50 iPP/aPS weight ratios and with different amounts of added SEP compatibilizer were studied by optical microscopy (OM), scanning electron microscopy (SEM), transmission electron microscopy (TEM), small-angle X-ray scattering (SAXS) and wide-angle X-ray diffraction (WAXD). SEP significantly reduced the size of dispersed aPS particles that enabled better spherulitization in the iPP matrix. Furthermore, iPP spherulites in ternary blends with 90/10 iPP/aPS weight ratio became larger in comparison with the pure iPP. TEM revealed that the SEP formed continuous interface layer around the dispersed aPS particles even when only 2.5 wt.% of SEP was added. Particle size distribution was distinctly bimodal. When the SEP content was increased to 10 wt.%, joining together smaller and bigger aPS and SEP particles formed dispersed aggregates. Additionally, both amorphous components (aPS and SEP) influenced crystallization process of iPP matrix and so modified, to some extent, its final supermolecular structure. SEP compatibilizer did not significantly affect crystallite orientation. The increase of crystallite sizes, which was more affected by the addition of aPS than by the addition of SEP, seemed to be influenced by the solidification effect rather than by the phase morphology of the blends.     

Effect of PHB on the properties of biodegradable PLA blends

Blends of biodegradable polymers polylactic acid/thermoplastic starch/polyhydroxybutyrate (PLA/TPS/PHB) were prepared using a twin-screw extruder. The TPS content was constant (50 %) and the PHB content in the blends was gradually changed from 0 mass % to 20 mass %. TPS was prepared by melting, where a mixture of native starch, water and glycerol was fed into the twinscrew extruder. Average temperature of extrusion was 180°C and the concentration of glycerol was 40 mass %. Influence of the PHB concentration in the blend and that of the processing technology on the mechanical and rheological properties of the PLA/PHB composition containing TPS were studied. Mechanical properties were measured 24 h after the film and monofilament preparation and also after the specific storage time to study the effect of storage on the properties. The results indicate that differences in morphology strongly influence the mechanical properties of the studied materials with identical material composition.     

A Mixed Plasticizer for the Preparation of Thermoplastic Starch

In this paper, formamide was firstly used as plasticizer to prepare thermoplastic starch (TPS), which could suppress the retrogradation of TPS by X-ray diffractometry (XRD) and show a good flexibility, but was weaker than conventional glycerol-plasticized TPS (GPTPS). When urea was introduced into plasticizer, both the retrogradation and mechanical properties were ameliorated. The tensile stress, strain and energy break of TPS plasticized by urea (wt. 20%) and formamide (wt.10%), respectively, reached 4.83 MPa, 104.6 % and 2.17 N-m (Newton-meter) after it had been stored at relative humidity (RH) 30% for one week.     

Phase morphology and mechanical properties of iPP/SEP blends

The effects of the addition of diblock copolymer poly(styrene‐b‐ethylene‐co‐propylene) (SEP) to isotactic polypropylene (iPP) on the morphology and mechanical properties were investigated. Phase morphologies of iPP/SEP blends up to a 70/30 weight ratio, prepared in Brabender Plasticoder, were studied with optical microscopy, scanning electron microscopy, transmission electron microscopy, and wide‐angle X‐ray diffraction. The addition of 2.5 wt % SEP caused a nucleation effect (by decreasing the crystallite and spherulite size) and randomization of the crystallites. With further SEP addition, the crystallite and spherulite size increased because of prolonged solidification and crystallization and achieved the maximum in the 80/20 iPP/SEP blend. This maximum was a result of the appearance of β spherulites and the presence of mixed α spherulites in the 80/20 iPP/SEP blend. Dispersed SEP particles were irregular and elongated clusters consisting of oval and spherical core–shell microdomains or SEP micelles. SEP clusters accommodated their shapes to interlamellar and interspherulitic regions, which enabled a well‐developed spherulitization even in the 70/30 iPP/SEP blend. The addition of SEP decreased the yield stress, elongation at yield, and Young's modulus but significantly improved the notched impact strength with respect to the strength of pure iPP at room temperature. Some theoretical models for the determination of Young's modulus of iPP/SEP blends were applied for a comparison with the experimental results. The experimental line was closest to the Takayanagi series model. © 2001 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 39: 566–580, 2001     

Structure and properties of degradable polyolefin-starch blends

The structure, mechanical properties and susceptibility to degradation of blends of low density polyethylene (PE) or isotactic polypropylene (PP) and glycerol plasticized starch (GS) was investigated. Monoethers of glycerol and fatty alcohols (GA) and in some cases epoxidized rubbers (ER) were used as compatibilizers for the investigated systems. It was found that mechanical properties and ageing susceptibility of blends depend strongly on their composition, i.e. the content of plasticized starch in the blend and the content of glycerol in the starch. In some cases an increased susceptibility to biodegradation during soil or fungus ageing not only of the starch phase but also of the polymer phase was observed. The susceptibility of these systems to accelerated artificial weathering was also investigated.     

尿素和甲酰胺塑化热塑性淀粉

用甲酰胺和尿素作为塑化剂制备了热塑性淀粉 (TPS) .扫描电镜显示甲酰胺和尿素混合物可以使淀粉塑化 ,形成均一的连续相 ;根据FT IR谱图可以确定 ,与甘油相比 ,甲酰胺可以使热塑性淀粉体系在保存时更稳定 ,各基团的化学环境变化更小 ,这是由于甲酰胺可以和淀粉羟基形成更稳定的氢键 .X ray衍射说明甲酰胺和尿素 (重量比为 10 % 2 0 % )作为混合塑化剂可以有效抑制淀粉的回生 ,同时防止尿素结晶析出 .在RH=33%的湿度环境保存 1周 ,这种热塑性淀粉有良好的拉伸强度、伸长率和断裂能 ,分别达到 4 83MPa ,10 4 6 %和 2 17N·m .水含量对热塑性淀粉的力学性能的影响也被研究 .另外 ,热失重实验和吸水实验说明这种热塑性淀粉的热稳定性和耐水性也要优于常用的甘油塑化热塑性淀粉     

Preparation,characterization and performances of biodegradable thermoplastic starch

A biodegradable thermoplastic starch (TPS) was successfully prepared from plasticizer ethanolamine and native cornstarch. The hydrogen bonding interaction between starch and ethanolamine was investigated using Fourier transform infrared (FT‐IR). When the ethanolamine mass content was 30%, after the ethanolamine‐plasticized thermoplastic starch (ETPS) was stored at RH 50% for 14 days, the mechanical testing showed that the maximum tensile stress of the ETPS reached 5.98 MPa, the tensile strain reached 106.52%, Young's modulus increased from 38.14 MPa of glycerol‐plasticized thermoplastic starch (GTPS) to 75.32 MPa of ETPS, and the breaking energy increased from 1.921 N·m to 2.305 N·m, which indicated that the mechanical properties of ETPS evidently excelled those of the GTPS. The effects of water contents on the mechanical properties of ETPS and GTPS were studied. A differential scanning calorimetry (DSC) analysis revealed that the low‐temperature transition and the glass transition temperature (T_g) of the ETPS were ?58 and 22°C respectively, which were lower than that of the GTPS. The ETPS effectively restrained the re‐crystallization of traditional GTPS, which was proved by the X‐ray diffraction (XRD). The scanning electron microscopy (SEM) images presented that ethanolamine made starch uniform. Copyright © 2007 John Wiley & Sons, Ltd.     

Interactions and partitioning of diluents/plasticizers in hydroxypropyl methylcellulose and polyvinyl alcohol homopolymers and blends. Part II: Glycerol

The interactions and partitioning of glycerol in polyvinyl alcohol (PVA), hydroxypropyl methylcellulose (HPMC) and their blends has been studied by means of torsional braid analysis (TBA). Glycerol was shown to be a more efficient plasticizer for PVA than HPMC in agreement with solubility parameter prediction. Kelley-Bueche-type equations were fitted to the experimentalTg data and initial slopes yielded an interaction parameter,Kø, between glycerol and the two polymers. Incorporation of glycerol in PVA/HPMC blends did not alter the incompatibility of the two polymers and plasticized both phases. The compositions of the two plasticized phases were calculated from Kelley-Bueche expressions fitted to the experimental data, enabling determination of the glycerol partition coefficients into the two phases. In blends with 20–60% PVA, glycerol partitioned selectively into the PVA-rich phase whereas in the system with 80% PVA, glycerol partitioned selectively into the HPMC-rich inclusions.     

Poly(lactic acid)/coplasticized thermoplastic starch blend: Effect of plasticizer migration on rheological and mechanical properties

Polylactic acid (PLA) and thermoplastic starch (TPS) are known as bio‐based and biodegradable thermoplastic polymers that can be used in different applications owing to their inherent physical and mechanical properties. In order to reduce the higher costs of PLA and tuning its physical and mechanical properties suitable for short life packaging applications, blending of PLA with the TPS, more economical biodegradable polymer, has been considered in academic and industrial researches. However, melt blending of PLA with TPS without compatibilization process caused some drawbacks such as coarsening morphology and declining mechanical properties and ductility because of thermodynamic immiscibility, which may restrict its usage in packaging applications. Subsequently, our approach in this research is compatibilization of PLA/TPS blends by utilization of primary well tuning of TPS formulation with a combination of sorbitol and glycerol plasticizers. In this work, the wide composition range of melt mixed PLA/TPS blends was prepared using a laboratory twin screw extruder. The effects of microstructure on the rheological and mechanical properties of PLA/TPS blends were studied using different methods such as scanning electron microscopy (SEM) images, contact angle, oscillatory shear rheological measurements, and tensile and impact strength mechanical tests. The rheological and mechanical properties were interpreted according to the morphological features and considering the possibility of plasticizer migration from TPS to PLA phase during melt blending. Reduction in complex viscosity and storage modulus of PLA matrix samples indicates the improved melt processability of blends. Finally, in comparison with mechanical results reported in literature, our simple approach yielded the blends with elastic modulus and ductility comparable with those of chemically compatibilized PLA/TPS blends.     

Blends of isotactic polypropylene and natural terpene resins. I. Phase structure,thermal, and dynamic‐mechanical properties

This article discusses the influence of two natural terpene resins (NTR), poly(α‐pinene) (PαP A115) and poly(d‐limonene) (PL C115), on morphology, miscibility, thermal, and dynamic‐mechanical properties of their blends with isotactic polypropylene (iPP). The NTR have interesting physical and chemical properties, and they are approved for food contact application. From the results of differential scanning calorimetry and dynamic‐mechanical thermal analysis it was deduced that both the resins were completely miscible with the amorphous iPP up to the composition investigated here (70/30 wt %). Scanning electron microscopy (SEM) analysis instead showed that the 70/30 iPP/PαP A115 blend and 80/20 and 70/30 iPP/PL C115 blends contained very small domains homogeneously distributed into the matrix. It is hypothesized that the domains are likely formed by the terpene‐rich phase, and the matrix by the iPP‐rich phase (besides the crystallized iPP phase). The iPP‐rich phase and the NTR‐rich phase would have the glass transition temperatures so close that they cannot be resolved by DSC and DMTA. Finally, for the iPP/PαP A115 system an upper critical solution temperature (UCST) is proposed. © 1999 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 37: 867–878, 1999     

Moisture‐resistant and strength retention properties of supercritical CO2‐processed thermoplastic starch modified by polyvinyl alcohol with varying degrees of polymerization

The ease of melt‐processing, moisture‐resistance, and tensile retention properties of scCO₂ and polyvinyl alcohol (PVA)–modified thermoplastic starch (scCO₂TPS_xPVA^a_y) materials were explored in this investigation. These characteristics were considerably improved by PVA modification particularly with decreasing PVA degree of polymerization (DP). The intensities of O―H stretching bands of scCO₂TPS_xPVA^a_y were considerably larger, and peak location of O―H stretching bands were significantly smaller than those of the corresponding TPS_xPVA^a_y and reduced gradually with the decrease in PVA's DP. The ΔH of melting and diffraction peaks of V_h‐type crystals for conditioned TPS_xPVA^a_y and scCO₂TPS_xPVA^a_y were considerably smaller than those of corresponding TPS and TPS_xPVA^a_y aged for the same time period and gradually reduced in intensity with decreasing PVA's DP. Possible reasons accounting for the considerably improved melt processing, moisture resistance, tensile retention, and retrogradation of scCO₂TPS_xPVA^a_y with decreasing PVA's DP are proposed.     

微生物合成的β-羟基丁酸酯与β-羟基己酸酯共聚物/聚乳酸共混材料(PHBHHx/PLA)的力学性能与生物降解性研究

通过熔融共混法制备了聚乳酸/微生物产β-羟基丁酸酯与β-羟基己酸共聚物的共混物(PLA/PHBHHx)。采用拉伸力学试验研究了共混物的力学性能。通过土壤悬浊培养降解法和扫描电子显微镜(SEM)分析对共混材料的生物降解性能进行了研究。实验结果表明,随着PHBHHx含量的增加,共混物的拉伸强度和杨氏模量降低,而生物降解速率却显著提高。但是,在175h之前,重量组成比为20/80的共混物降解速率比纯PHBHHx还要快。综合分析表明,共混材料PLA/PHBHHx的重量比为20/80时,具有优良的力学性能和生物降解性。     

微生物合成的β-羟基丁酸酯与β-羟基已酸酯共聚物/聚乳酸共混材料(PHBHHx/PLA)的力学性能与生物降解性研究

通过熔融共混法制备了聚乳酸/微生物产β-羟基丁酸酯与β-羟基己酸共聚物的共混物(PLA/PHBHHx).采用拉伸力学试验研究了共混物的力学性能.通过土壤悬浊培养降解法和扫描电子显微镜(SEM)分析对共混材料的生物降解性能进行了研究.实验结果表明,随着PHBHHx含量的增加,共混物的拉伸强度和杨氏模量降低,而生物降解速率却显著提高.但是,在175h之前,重量组成比为20/80的共混物降解速率比纯PHBHHx还要快.综合分析表明,共混材料PLA/PHBHHx的重量比为20/80时,具有优良的力学性能和生物降解性.     

Blends of starch with ethylene vinyl alcohol copolymers: effect of water,glycerol, and amino acids as plasticizers

Blends of thermoplastic starch with poly(ethylene‐co‐vinyl alcohol) copolymer (EVOH) were melt extruded with water/glycerol as plasticizer and a series of amino acid additives. The biggest factor in end‐use mechanical properties proved to be the relative humidity (RH) during storage. Plasticized starch‐EVOH blends stored at 0 and 50% RH changed significantly over time, with, for example, the tensile strength (TS) of the glycerol‐plasticized blend increasing from 4.7 to 26.3 MPa over 8 weeks when maintained at 0% RH. In contrast, the TS of this same sample stored at 75% RH remained unchanged for 8 weeks. Amino acids provided relatively minor, but significant changes in mechanical properties with time. Based on TS, elongation‐to‐break, and modulus, it may be concluded that β‐alanine, sarcosine, and L ‐proline were more effective than glycerol at maintaining strong flexible blends. Increases in crystallinity and changes in morphology with time, as described by modulated DSC were correlated to these changes in mechanical properties. Published in 2007 by John Wiley & Sons, Ltd.     

Thermoplastic starch and glutaraldehyde modified thermoplastic starch foams prepared using supercritical carbon dioxide fluid as a blowing agent

Supercritical carbon dioxide (scCO₂) processed thermoplastic starch (scCO₂^aTPS), cellulose nanofiber (CNF) modified scCO₂^aTPS (scCO₂^aTPS₁₀₀CNF_0.02) and glutaraldehyde (GA) modified scCO₂^aTPS₁₀₀CNF_0.02 (scCO₂^aTPS₁₀₀CNF_0.02GA_x) foams were prepared for the first time using scCO₂ as a blowing agent during their foaming processes. The expansion ratio, cell density, moisture resistance, and compressive strength (σ_c) retention properties of each foam series were considerably improved with increasing scCO₂ pressure during the foaming processes. The expansion ratios and cell densities of each scCO₂^aTPS₁₀₀CNF_0.02GA_x foam series were increased considerably to a maximum value, as the GA content approached an optimum value. The optimal scCO₂¹¹TPS₁₀₀CNF_0.02GA_1.6 foam material exhibited a high expansion ratio and cell density at approximately 50 and approximately 8 × 10⁸ cells/cm³, respectively. Compared with corresponding aged scCO₂^aTPS and scCO₂^aTPS₁₀₀CNF_0.02 foam specimens, considerably better moisture resistance and σ_c retention properties were observed for scCO₂^aTPS₁₀₀CNF_0.02GA_x foam specimens, when they were modified with the corresponding optimum GA content. The moisture resistance and σ_c retention for optimal prepared scCO₂⁷TPS₁₀₀CNF_0.02GA_0.4, scCO₂⁹TPS₁₀₀CNF_0.02GA_0.8 and scCO₂¹¹TPS₁₀₀CNF_0.02GA_1.6 foam materials improved further with increasing scCO₂ pressure. Possible reasons accounting for the highly expansion ratio, moisture resistance, and σ_c retention properties for scCO₂^aTPS₁₀₀CNF_0.02GA_x foams are presented.     

New approach on the development of plasticized polylactide (PLA): Grafting of poly(ethylene glycol) (PEG) via reactive extrusion

In this work, new ways of plasticizing polylactide (PLA) with low molecular poly(ethylene glycol) (PEG) were developed to improve the ductility of PLA while maintaining the plasticizer content at maximum 20 wt.% PLA. To this end, a reactive blending of anhydride-grafted PLA (MAG-PLA) copolymer with PEG, with chains terminated with hydroxyl groups, was performed. During the melt-processing, a fraction of PEG was grafted into the anhydride-functionalized PLA chains. The role of the grafted fraction was to improve the compatibility between PLA and PEG. Reactive extrusion and melt-blending of neat and modified PLA with PEG did not induce any dramatic drop of PLA molecular weight. The in situ reactive grafting of PEG into the modified PLA in PLA/PEG blends showed a clear effect on the thermal properties of PLA. It was demonstrated by DSC that the mobility gained by PLA chains in the plasticized blends yielded crystallization. The grafting of a fraction of PEG into PLA did not affect this process. However, DSC results obtained after the second heating showed an interesting effect on the T_g when 20 wt.% PEG were melt blended with neat PLA or 10 wt.% MAG-PLA. In the latter case, the T_g displayed by the reactive blend was shifted to even lower temperatures at around 14 °C, while the T_g of neat PLA and PLA blended with 20 wt.% PEG was around 60 and 23 °C, respectively. Regarding viscoelastic and viscoplastic properties, the presence of MAG-PLA does not significantly influence the behavior of plasticized PLA. Indeed, with or without MAG-PLA, elastic modulus and yield stress decrease, while ultimate strain increases with the addition of PEG into PLA.     

Barrier and mechanical properties of modified starches

The study addressed starch-based coatings on paper and fabrics. Coated materials and free starch films containing different amounts of a well-established plasticizer (glycerol) or potential plasticizer (mainly polyols) were tested with respect to water vapour permeance (WVPe), water vapour permeability (WVP), glass transition temperature (T_g), and mechanical strength (tensile tests). Both normal and high- amylose potato starch were used. These starches were modified by (a) oxidation, (b) oxidation and hydroxypropylation or (c) oxidation and hydrophobically modified by reaction with octenyl- or alkenyl-substituted succinic acid anhydride. Free films of hydroxypropylated high-amylose potato starch showed a lower WVP than did the corresponding starches based on regular potato starch. The WVP of the hydrophobically modified regular potato starches was substantially higher than that of films of the corresponding hydroxypropylated starches. The expected hydrophobic effect of the succinic acid anhydrides in terms of a reduced WVP could not be observed. When glycerol was used as a plasticizer, about 30 parts (by wt.) per hundred parts of starch were needed in order to reduce the T_g and to cause observable changes in the mechanical properties of the free films.     

Polystyrene/thermoplastic starch blends with different plasticizers

Conventional plastics has a large impact in increasing the environment’s pollution. That’s why the interest has turned towards novel partially and completely biodegradable polymers. In this work, blends of polystyrene and thermoplastic starch with glycerol and Buriti (Mauritia flexuosa L.) oil as plasticizers were prepared. Samples were analyzed using TG/DTG and DSC techniques. The TG results indicated that the blends with Buriti oil are thermally more stable than those with glycerol. The DSC analysis that Buriti oil provides a higher degree of plasticization of PS, compared to the blends plasticized using glycerol under the studied conditions.