Miscibility and Biodegradability of Poly(Butylene Succinate)/Poly(Butylene Terephthalate) Blends

As one of the biodegradable polymers, the blend of poly(butylene succinate) and poly(butylene terephthalate) is dealt with in this study. In our previous work, it was demonstrated that PBS and PBT are immiscible not only from the changes of T _g but also from logG–log G plots. It is expected that the biodegradability of the blends could be improved by enhancing the miscibility. We tried to induce the transesterification reaction between two polyesters with various time intervals to enhance the miscibility of the blends. The extent of transesterification reaction was examined by ¹H-NMR. We utilized a dynamic mechanical thermal analyzer and a rotational rheometer to investigate the changes in miscibility. We also verified the biodegradability of PBS/PBT blends after the transesterification reaction by the composting method.     

Mechanical, Thermal and Water Absorption Properties of Kenaf-Fiber-Based Polypropylene and Poly(Butylene Succinate) Composites

The use of composites made from non-biodegradable conventional plastic materials (e.g., polypropylene, PP) is creating global environmental concern. Biodegradable plastics such as poly(butylene succinate) (PBS) are sought after to reduce plastic waste accumulation. Unfortunately, these types of plastics are very costly; therefore, natural lignocellulosic fibers are incorporated to reduce the cost. Kenaf fibers are also incorporated into PP and PBS for reinforcing purposes and they have low densities, high specific properties and renewable sourcing. However without good compatibilization, the interfacial adhesion between the matrix and the fibers is poor due to differences in polarity between the two materials. Maleic anhydride-grafted compatibilizers may be introduced into the system to improve the matrix-fiber interactions. The overall mechanical, thermal and water absorption properties of PP and PBS composites prepared with 30 vol.% short kenaf fibers (KFs) using a twin-screw extruder were being investigated in this study. The flexural properties for both types of composites were enhanced by the addition of compatibilizer, with improvements of 56 and 16 % in flexural strength for the PP/KF and PBS/KF composites, respectively. Good matrix-fiber adhesion was also observed by scanning electron microscopy. However, the thermal stability of the PBS/KF composites was lower than that of the PP/KF composites. This result was confirmed by both DSC and TGA thermal analysis tests. The water absorption at equilibrium of a PBS composite filled with KFs is inherently lower than of a PP/KF composite because the water molecules more readily penetrate the PP composites through existing voids between the fibers and the matrix. Based on this research, it can be concluded that PBS/KF composites are good candidates for replacing PP/KF composites in applications whereby biodegradability is essential and no extreme thermal and moisture exposures are required.     

Effect of Poly(l-Lactide) and Poly(Butylene Succinate) on the Growth of Red Pepper and Tomato

Seeds of red pepper and tomato were sowed and cultivated in a soil blended with powdery poly(l-lactide) (PLLA), and poly(butylene succinate) (PBS). PBS depressed the growth of the two plants significantly even at a concentration as low as 5%, whereas PLLA up to 35% affected negligibly or even boosted the growth of the two plants. pH and number of microbial cells in the soil after 80 days of cultivation were almost the same independently whether the soil was blended with the two polymers or not. In contrast, the molecular weight of PBS decreased much faster than that of PLLA. Because succinic acid and 1,4-butane diol, from which PBS was synthesized, exhibited toxicity to both plant and animal cells to retard the germination rate of young radish seeds and to deform the morphology of HeLa cells significantly [1], the monomers and the oligomers produced from the PBS degradation should have a detrimental influence on the growth of the two plants.     

Starch, Poly(lactic acid), and Poly(vinyl alcohol) Blends

Research on biodegradable materials has been stimulated due to concern regarding the persistence of plastic wastes. Blending starch with poly(lactic acid) (PLA) is one of the most promising efforts because starch is an abundant and cheap biopolymer and PLA is biodegradable with good mechanical properties. Poly(vinyl alcohol) (PVOH) contains unhydrolytic residual groups of poly(vinyl acetate) and also has good compatibility with starch. It was added to a starch and PLA blend (50:50, w/w) to enhance compatibility and improve mechanical properties. PVOH (M_W 6,000) at 10%, 20%, 30%, 40%, 50% (by weight) based on the total weight of starch and PLA, and 30% PVOH at various molecular weights (M_W 6,000, 25,000, 78,000, and 125,000 dalton) were added to starch/PLA blends. PVOH interacted with starch. At proportions greater than 30%, PVOH form a continuous phase with starch. Tensile strength of the starch/PLA blends increased as PVOH concentration increased up to 40% and decreased as PVOH molecular weight increased. The increasing molecular weight of PVOH slightly affected water absorption, but increasing PVOH concentration to 40% or 50% increased water absorption. Effects of moisture content on the starch/PLA/PVOH blend also were explored. The blend containing gelatinized starch had higher tensile strength. However, gelatinized starch also resulted in increased water absorption.     

Radiation Crosslinking of Poly(Butylene Succinate) in the Presence of Inorganic Material and Its Biodegradability

Three kinds of poly(butylene succinate)s (PBS) with different molecular weight were irradiated with electron beams in the presence of inorganic material. Fourteen kinds of inorganic materials were used in this work. The presence of inorganic material inside cross-linked PBS samples enhances the yield of gel formation. The heat stabilities of PBS samples were checked; it was found that silicon dioxide and carbon black significantly improve these properties. Enzymatic and soil burial tests were performed; the presence of these inorganic materials in cross-linked PBS accelerates the rate of biodegradation.     

Blends of Poly (Butylene Adipate-Co-Terephthalate) and Thermoplastic Whey Protein Isolate: A Compatibilization Study

Journal of Polymers and the Environment - This work assesses the influence of the plasticizer polyethylene glycol (PEG) on the compatibilization of poly (butylene adipate-co-terephthalate) (PBAT)...     

Processing and Characterization of Short-Fiber Reinforced Jute/Poly Butylene Succinate Biodegradable Composites: The Effect of Weld-Line

Fabrication of complex injection molded parts often involves the use of multiple gates. In such situations, polymer melts from different gates meld to form the molded part (weld line). This paper reports on the fabrication and characterization of the mechanical and morphological properties of short fiber reinforced jute/poly butylene succinate (PBS) biodegradable composites. The effect of a dual gated mold in the fabrication of welded specimens was a key focus of the investigation. It was observed that incorporation of jute fiber (10 wt%) conferred drastic changes on the stress–strain properties of the matrix as the elongation at break (EB), dropped from 160% in the matrix to just 10% in the composite. The tensile strength of the composite was lower than that of the matrix. However, it is noteworthy that the tensile modulus of the composite increased. Bending test also revealed that both bending strength and modulus increased with the incorporation of jute. Morphological studies of the tensile fracture surface using SEM revealed two types of failure mode. Ductile failure was indicated by plastic deformation at the initiation of fracture followed by brittle failure. The good interfacial bonding indicated between jute and PBS was attributed to positive interaction between the two polar polymers. A comparison of the non-weld and weld-line samples revealed that the weld-line composites have better mechanical integrity than the corresponding polymer matrix with weld line. The results also revealed that elongation at break and toughness are most sensitive to the presence of the weld-line whereas flexural properties are least sensitive.     

Natural Weathering of Kenaf Bast Fibre-Filled Poly(Butylene Succinate) Composites: Effect of Fibre Loading and Compatibiliser Addition

Natural weathering was performed on poly(butylene succinate) (PBS) and its kenaf bast fibre (KBF) filled composites by exposing the specimens to a tropical climate for a period of 6 months (max–min temperature: 31.5–23.9 °C; relative humidity: 78.9%). The aim of this study was to investigate the effects of KBF loading and the addition of maleated PBS compatibiliser (PBSgMA) on the performance of the composites under natural weathering. As expected, the flexural properties of both the uncompatibilised and compatibilised composites dropped with increasing exposure time. The weathered specimens were also assessed by colour change analysis, FTIR spectroscopy analysis and SEM examination. The total colour change, ΔE _ab , of both the uncompatibilised and compatibilised composites increased with weathering time. FTIR spectroscopy analysis confirmed the presence of oxidation products such as hydroxyl, carbonyl and vinyl species in the weathered uncompatibilised and compatibilised composites. SEM examination revealed the presence of surface defects such as cracking, tiny holes and degraded fibre, which explain the poor performance of the composites upon weathering.     

Effect of Poly(dioxolane) as Compatibilizer in Poly(ɛ-caprolactone)/Tapioca Starch Blends

The influence of poly(dioxolane) (PDXL), a poly(ethylene oxide-alt-methylene oxide), as compatibilizer on poly(ɛ-caprolactone) (PCL)/tapioca starch (TS) blends was studied. In order to facilitate blending; PCL, PDXL and TS must be blended together directly; so that PDXL is partially adhered at the TS surface as shown by scanning electron microscopy. The molecular weight effect of PDXL on the PCL/TS blends showed that mechanical properties of PCL/TS/PDXL blends from low molecular weight (M _n=10,000) and high molecular weight (M _n=200,000) PDXL were rather dependent on TS content. The enzymatic degradability of PCL/TS/PDXL blends using α-amylase increased as the TS content increased but was independent on the dispersion of tapioca starch in the PCL matrix.     

Poly(Ethylene Glycol) as a Compatibilizer for Poly(Lactic Acid)/Thermoplastic Starch Blends

A new route to prepare poly(lactic acid) (PLA)/thermoplastic starch (TPS) blends is described in this work using poly(ethylene glycol) (PEG), a non-toxic polymer, as a compatibilizer. The influence of PEG on the morphology and properties of PLA/TPS blends was studied. The blends were processed using a twin-screw micro-compounder and a micro-injector. The morphologies were analyzed by scanning and transmission electron microscopies and the material properties were evaluated by dynamic-mechanical, differential scanning calorimetry, thermogravimetric analysis and mechanical tests. PLA/TPS blends presented large TPS phase size distribution and low adhesion between phases which was responsible for the lower elastic modulus of this blend when compared to pure PLA. The addition of PEG resulted in the increase of PLA crystallization, due to its plasticizing effect, and improvement of the interfacial interaction between TPS and PLA matrix. Results show that incorporation of PEG increased the impact strength of the ternary blend and that the elastic modulus remained similar to the PLA/TPS blend.     

Structural and Thermal Properties of Starch Plasticized with Glycerol/Urea Mixture

Journal of Polymers and the Environment - The paper presents the results of research on the influence of used plasticizing system on the structural and thermal properties of thermoplastic starch...     

Fungal Degradation of Poly(Butylene Adipate-Co-Terephthalate) in Soil and in Compost

The present work mainly dedicated to fungal degradation of poly(butylene adipate-co-terephthalate) [PBAT], to enclose the role of fungi in a real process of biodegradation, the degree of degradation, and to understand the kinetics of PBAT biodegradation. Respirometer tests were realized in soil at 30 °C, and in compost at 30 and 58 °C. Results have shown that temperature is one of the essential parameters governing the fungal degradation of PBAT. Moreover, the final rates of PBAT biodegradation in an inoculated compost with fungi and in a real compost were found comparable, which means that the selected fungi were efficient as much as a mixture of bacteria and fungi. The curves of PBAT biodegradation were modeled by Hill sigmoid. Fungal degradation was completed by investigating the physical and the chemical properties of the polymer during the process of degradation using several analytical methods such as matrix assisted laser desorption ionization-time of fly spectroscopy, size exclusion chromatography, and differential scanning calorimetry. These experiments led to a better understanding of the various stages of fungal degradation of PBAT: hydrolysis as well as mineralization. Furthermore, the analysis of metabolizing products was investigated also.     

Biodegradable Blends Based on Starch and Poly(Lactic Acid): Comparison of Different Strategies and Estimate of Compatibilization

Finding plastic substitutes based on sustainability, especially for short-term packaging and disposable applications has aroused scientific interest for many years. Starch may be a substitute for petroleum based plastics but it shows severe limitations due to its water sensitivity and rather low mechanical properties. To overcome these weaknesses and to maintain the material biodegradability, one option is to blend plasticized starch with another biodegradable polymer. To improve both the compatibility between the main phases and the performance of the final blend, different compatibilization strategies are reported in literature. However, the relative efficiency of each strategy is not widely reported. This paper presents three different strategies: in situ (i) formation of urethane linkages; (ii) coupling with peroxide between starch and PLA, and (iiii) the addition of PLA-grafted amylose (A-g-PLA) which has been elaborated ex situ and carefully analyzed before blending. This study compares the effect of each compatibilization strategy by investigating mechanical and thermal properties of each blend. Compatibilizing behavior of the A-g-PLA is demonstrated, with a significant increase (up to 60%) in tensile strength of starch/PLA blend with no decrease in elongation at failure.     

Rheology,Morphology, Crystallization Behaviors,Mechanical and Thermal Properties of Poly(lactic acid)/Polypropylene/Maleic Anhydride-Grafted Polypropylene Blends

The rheologies, morphologies, crystallization behaviors, mechanical and thermal properties of poly(lactic acid) (PLA)/polypropylene (PP) blends and PLA/PP/maleic anhydride-grafted PP (MAPP) blends were investigated. The results showed that the complex viscosities of PLA/PP blends were between those of neat PLA and neat PP, and MAPP had a thinning effect on those of the blends. PLA/PP blends exhibited the distinct phase separation morphologies due to the limited partial miscibility of the blend components. MAPP slightly improved the miscibility between PLA and PP. Both the cold crystallization of PLA component and melt crystallization of PP component were enhanced, probably because PLA and PP were reciprocal nucleating agents. The tensile strength and flexural modulus decreased, while the tensile strain at break and heat deflection temperature (HDT) increased with the increasing PP content. MAPP had the positive effects on the notched impact strength and HDT of PLA-rich blends and also increased the flexural modulus of the binary blends. The thermal stability of the blend was improved by PP, and the incorporation of MAPP further enhanced the thermal stability.     

A Study of Dynamic Mechanical and Thermal Behavior of Starch/Poly(vinylalcohol) Based Films

Starch/Poly(vinylalcohol) blends in two different ratios (60:40 and 50:50) were prepared with glycerol as a plasticizer. Films were cast by a solution casting method. One set of films were filled with 10 wt% of bentonite clay and another set of films were crosslinked with epichlorohydrin in an alkaline medium. The prepared film samples were characterized with dynamic mechanical analysis (DMA) and thermogravimetric analysis (TGA). The presence of clay and crosslinking with epichlorohydrin was found to have considerable effect on the dynamic mechanical properties and thermal stability of the films. Intercomponent H-bonding between starch, Poly(vinylalcohol) and glycerol enhanced the thermal stability of the films. But incorporation of clay and crosslinking with epichlorohydrin enhanced the steric crowding and lowered the thermal stability of the films.     

Spectral Characterization of Four Kinds of Biodegradable Plastics: Poly (Lactic Acid), Poly (Butylenes Adipate-Co-Terephthalate), Poly (Hydroxybutyrate-Co-Hydroxyvalerate) and Poly (Butylenes Succinate) with FTIR and Raman Spectroscopy

Fourier transform infrared microscope and confocal Raman spectroscope were employed in this study to investigate four kinds of biodegradable plastics: poly(lactic acid),poly(butylenes adipate-co-terephthalate), poly(butylenes succinate) and poly(hydroxybutyrate-co-hydroxyvalerate), which are used more and more popularly in everyday life but can not be identified easily with other instruments. Infrared and Raman spectra of the plastics were tentatively interpreted. The indicative peaks to characterize the four polymers were also summarized. The result in this study can help the forensic scientists discriminate the plastics accurately when they occurred as trace evidences in cases, it also offers the producer and environment scientists an effective, non-invasive and fast method to characterize and identify these four polymers.     

Grafting of Glycidyl Methacrylate onto Poly(lactide) and Properties of PLA/Starch Blends Compatibilized by the Grafted Copolymer

Poly(lactide)-graft-glycidyl methacrylate (PLA-g-GMA) copolymer was prepared by grafting GMA onto PLA in a batch mixer using benzoyl peroxide as an initiator. The graft content was determined with the ¹H-NMR spectroscopy by calculating the relative area of the characteristic peaks of PLA and GMA. The result shows that the graft content increases from 1.8 to 11.0 wt% as the GMA concentration in the feed varies from 5 to 20 wt%. The PLA/starch blends were prepared by the PLA-g-GMA copolymer as a compatibilizer, and the structure and properties of PLA/starch blends with or without the PLA-g-GMA copolymer were characterized by SEM, DSC, tensile test and medium resistance test. The result shows that the PLA/starch blends without the PLA-g-GMA copolymer show a poor interfacial adhesion and the starch granules are clearly observed, nevertheless the starch granules are better dispersed and covered by PLA when the PLA-g-GMA copolymer as a compatibilizer. The mechanical properties of the PLA/starch blends with the PLA-g-GMA copolymer are obviously improved, such as tensile strength at break increasing from 18.6 ± 3.8 MPa to 29.3 ± 5.8 MPa, tensile modulus from 510 ± 62 MPa to 901 ± 62 MPa and elongation at break from 1.8 ± 0.4 % to 3.4 ± 0.6 %, respectively, for without the PLA-g-GMA copolymer. In addition, the medium resistance of PLA/starch blends with the PLA-g-GMA copolymer was much better than PLA/starch blends.     

Biodegradable Poly(butylene succinate) and Poly(butylene adipate-co-terephthalate) Blends: Reactive Extrusion and Performance Evaluation

Two biodegradable polyesters, poly(butylene adipate-co-terephthalate) (PBAT) and poly(butylene succinate) (PBS) were melt-compounded in a twin screw extruder to fabricate a novel PBS/PBAT blend. The compatibility of the blend was attributed to the transesterification reaction that was confirmed by Fourier transform infrared spectroscopy. The Gibbs free energy equation was applied to explain the miscibility of the resulting blend. Dynamic mechanical analysis of the blends exhibits an intermediate tanδ peak compared to the individual components which suggests that the blend achieved compatibility. One of the key findings is that the tensile strength of the optimized blend is higher than each of the blended partner. Rheological properties revealed a strong shear-thinning tendency of the blend by the addition of PBAT into PBS. The phase morphology of the blends was observed through scanning electron microscopy, which revealed that phase separation occurred in the blends. The spherulite growth in the blends was highly influenced by the crystallization temperature and composition. In addition, the presence of a dispersed amorphous phase was found to be a hindrance to the spherulite growth, which was confirmed by polarizing optical microscopy. Furthermore, the increased crystallization ability of PBAT in the blend systems gives the blend a balanced thermal resistance property.     

Thermal Degradation and Kinetic Parameters of Polyester and Poly(Lactic Acid) Blends Used in Shopping Bags in Brazil

In this work, synthetic polyester and poly(lactic acid) blends used as biodegradable shopping plastic bags were studied, together with control samples of polyethylene containing pro-oxidant catalysts (called “oxidegradable bags” in the market). Samples of these materials were weighed and buried in simulated soil for 3 months, and then studied by Thermal Analysis including a non-isothermal kinetic analysis. It was observed that although there was no significant mass loss in the period of the ageing, the activation energies for the thermal decomposition processes were substantially reduced for the biodegradable samples, but not for the oxidegradable ones.