Field performance on lettuce crops of poly(butylene adipate-co-terephthalate)/polylactic acid as alternative biodegradable composites mulching films

This work developed biodegradable poly(butylene adipate-co-terephthalate)/polylactic acid (PBAT/PLA) composites with different fillers to improve their physicochemical properties and biodegradability. The films were tested considering mechanical, morphological, thermal, crystalline, biodegradability, and ecotoxicity tests. Mechanical and morphological results indicated that the fillers' nature influences mechanical performance; all composites showed high-tensile strength (~30 MPa) than the pristine films (~12 MPa). The use of both fillers resulted in an interface, improving the matrix compatibility, reflecting in good thermal performance, low-water absorption, and high hydrophobicity. The WA (water absorption) and hydrophobicity are essential to maintain the crop's moisture since the water lost through plant transpiration will be condensed and returned to the soil. Films showed biodegradability and absence of toxicity, which allows the substitution of polyethylene commodity films as mulching films. Biodegradation and ecotoxicity tests indicate that the developed films are beneficial for lettuce crops and contribute to the development of seedlings.     

Biodegradation of 3D-printed polylactic acid milliprojections under physiological conditions

The degradation of 3D-printed polylactic acid (PLA) milliprojections of different molecular weights and crystallinity was studied under physiological conditions for a few months. The motivation of the work was to investigate the use of such printed materials as a potential release device in a transdermal patch. Upon being subjecting to a degradation environment, the remnant milliprojections were investigated in terms of weight loss and change in molecular weight. The critical molecular weights of the polymers were found to be between 8,000 g/mol and 13,000 g/mol. Among the polymers examined, the amorphous PLA had the fastest rate of degradation, losing almost half of its weight at the end of the study. Differential scanning calorimetry analysis further showed that the onset of degradation was favored in the amorphous regions of the polymers while scanning electron microscopy (SEM) findings suggest enhanced hydrolysis due to greater exposure caused by the increased porosity and crack formation upon reaching the critical molecular weight. Gel permeation chromatography (GPC) showed the emergence of multimodal molecular weight distribution during degradation indicating the fragmentation in the polymer bulk. The results of SEM and GPC analysis suggest that bulk erosion was the main mechanism of degradation of the 3D-printed models.     

Preparation and characterization of graphene‐agar and graphene oxide‐agar composites

Biodegradable counterparts of petro plastics for packaging applications are highly desired due to environmental considerations. Agar can be a potential material due to its availability and biodegradability. However, moderate mechanical strength and thermal stability, in addition to poor resistance against water, needs to be addressed before agar can be commercially implemented as packaging material. As a step toward this objective, graphene oxide (GO) and reduced GO (RGO) were incorporated in agar and were solution casted in the form of films. The tensile strength was increased by 118.4% and 69.4% at 2% GO and 2% RGO loading, respectively. Higher interfacial bonding between GO and agar compared to that of RGO and agar was attributed for the observed mechanical properties. Resistance to swelling and hydrophobicity (contact angle) of the composite were improved as well when compared to pure agar. The tensile strength and the contact angle values were however, decreased after the addition of 2% GO and 2% RGO. The morphological investigation showed that the formation of pores at higher concentration of reinforcement was the contributing factor for the decrease in tensile strength. No significant change in thermal properties was observed. The transmittance value was reduced to 0% after the incorporation of GO and RGO. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45085.     

Biodegradable porous polylactic acid film as a separator for supercapacitors

A porous polylactic acid (PLA) film was investigated as a separator for supercapacitors (SCs) and compared with commercial separators, for example, NKK-MPF30AC and Celgard 2400. The porous PLA film was fabricated via a facile phase inversion method, and the cross-sectional scanning electron microscope images of the PLA separator film exhibited highly porous interconnected morphology for ion diffusion. The surface modification of separators was performed by radio frequency (RF) air plasma to improve wettability. The plasma modification enhanced the water uptake and swelling properties of the separators and decreased the water contact angles of PLA and Celgard 2400 films. The mechanical and dielectric properties of separators were also studied. The ionic conductivities of RF-PLA in 1 M H₂SO₄ and 1 M Na₂SO₄ were found to be 1.1 × 10⁻¹ S/cm and 0.6 × 10⁻² S/cm at room temperature, respectively. The electrochemical impedance spectroscopy of the RF-PLA SCs showed the lowest solution resistance and internal resistance.     

Effect of glassy carbon addition and photodegradation on the biodegradation in aqueous medium of poly (3-hydroxybutyrate-co-3-hydroxyvalerate)/glassy carbon green composites

The use of biodegradable polymers is an interesting way to reduce the polymeric waste accumulation in the environment. However, the addition of fillers to biodegradable polymer matrices may decrease their biodegradability. Glassy carbon (GC) is a promising carbon material that can be employed as a filler in the production of antistatic packaging utilized to protect electronic components. The use of a biodegradable polymeric matrix such as poly (3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) can be an excellent alternative for the preparation of green composites to be used in these packages. This work aims to evaluate the effect of the GC addition and the GC particle size on the biodegradability of the PHBV matrix, as well as to study the result of the employment of a previous photodegradation treatment on the biodegradation in aqueous medium of PHBV/GC composites. Scanning electron microscopy, residual weight measurement (%) and surface roughness showed that GC does not interfere negatively with PHBV biodegradability. Differential scanning calorimetry analysis and residual weight measurement permitted to suggest that the increase in the crystallinity degree of PHBV and PHBV/GC samples occasioned by the ultraviolet radiation hindered the water and enzyme access to the bulk of the materials, decreasing the biodegradability.     

Preparation and characterization of antistatic packaging for electronic components based on poly(lactic acid)/carbon black composites

Poly(lactic acid) (PLA) is a biodegradable aliphatic polymer obtained from renewable sources; its main application is in the packaging sector. Electronic components require the use of antistatic packaging that prevents damage and electric shock. As PLA has no conductive characteristics, it requires the addition of allotropic carbon forms such as conductive carbon black to make the polymer less resistive as the dissipative material and making it suitable for the manufacture of antistatic packaging. In this study, PLA was melt blended with 5, 10, and 15 wt % of carbon black. The composites were prepared using a high-speed mixer. Samples were characterized by Izod impact resistance tests, scanning electron microscopy, thermal properties, electrical characterization, and biodegradation tests in garden soil. The addition of carbon black in the PLA matrix increases the temperature of degradation and decreases the crystallinity degree and the impact resistance of the composites. However, carbon black is a great option to increase the electrical conductivity of PLA. The addition of carbon black in PLA makes the composite less resistive and suitable for use as antistatic packaging for the transportation and storage of electronic components. Furthermore, this composite does not cause damage to the environment as the carbon black does not interfere in the degradation mechanism of PLA. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47273.     

Effects of molecular weight and grafted maleic anhydride of functionalized polylactic acid used in reactive compatibilized binary and ternary blends of polylactic acid and thermoplastic cassava starch

Polylactic acid (PLA) was reactively functionalized with maleic anhydride (MA) and 2,5‐bis(tert‐butylperoxy)?2,5‐dimethylhexane (Luperox 101 or L101) using a twin screw extruder (TSE). The effects of functionality (grafted MA level) and/or number average molecular weight of functionalized PLA (PLA‐g‐MA) as the reactive polymer pairs (binary blends) and reactive compatibilizer (ternary blends) were investigated. Due to the dominant side reaction during melt free radical grafting, polymer degradation or chain scission, PLA‐g‐MA having a higher grafted MA had lower molecular weights and intrinsic viscosity as well as broader molecular weight distribution values. The thermal, physical, mechanical, and morphological properties of binary blends produced by using the TSE and injection molding at a ratio of 70 wt % PLA‐g‐MA and 30 wt % thermoplastic cassava starch (TPCS) were analyzed. The reactive blends having grafted MA more than 0.4 wt % had poor tensile strength and elongation at break. Similar trends in morphology and tensile properties were observed in the reactive ternary blends. The use of PLA‐g‐MA strongly impacted the elongation at break but not the modulus or tensile strength. An increase of PLA‐g‐MA's number average molecular weight ( or M_n) improved the tensile properties of the blends. The reactive ternary blend having 0.1 wt % grafted MA on PLA and PLA‐g‐MA basis and PLA‐g‐MA's M_n of 45 kDa offered the highest elongation at break. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42230.     

Modification and extrusion coating of polylactic acid films

Polyethylene (PE) extrusion coating on paper substrates are the traditional packing material for coffee cups and take‐out food containers. It is difficult to recycle the PE/paper laminates and the thin polymer films remain in landfills after the decomposition of their paper substrates. Disposal of plastic materials is causing serious effects on our environment and wildlife. Demand for compostable or biodegradable plastic packaging products is increasing because of consumer pressure and legislation. Biodegradable polylactic acid (PLA) is regarded as one of the most promising biopolymers with a large market potential, but its applications are limited by poor thermal stability, mechanical properties and processibility. We utilize modified gelatin as additives to improve PLA's performance without compromizing the biomass origin and compostable properties of the material. Extrusion coating, or extrusion casting, of polylactic acid (PLA) films onto paper substrates to form PLA/paper laminates was achieved by modification of the polymer with a plant or animal gelatin. Various paper substrates with thin PLA coatings were prepared using a conventional extrusion coating equipment for the fabrication of take‐out food containers and coffee cups. Melt rheology of PLA and adhesion of the resulting thin film were greatly improved in the presence of a small amount of gelatin in the polymer matrices. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42472.     

Enhanced biodegradation and processability of biodegradable package from poly(lactic acid)/poly(butylene succinate)/rice-husk green composites

This work aims to study the possibility to process PLA/PBS/RH green composites into hexagonal plant-pots employing a large-scale industrial operation using injection molding. Green composites based on poly(lactic acid) (PLA), poly(butylene succinate) (PBS), and rice husk (RH) with various RH contents (10–30%wt.) were produced successfully using a twin-screw extruder. The compatibility of RH-matrix was improved by chemical surface modifications using a coupling agent. RH was analyzed as an effective filler for PLA to develop green composites with low cost, high biodegradability, improved processability, and comparable mechanical properties as unfilled PLA. With increasing RH content, tensile modulus of the composites increased gradually. The addition of PBS, at PLA/PBS ratio of 60/40, improved the elongation at break and impact strength of PLARH30 by 55% and 7.1%, respectively. The suitable processing temperatures for PLA decreased from 220–230°C to 170–180°C when 30%wt. RH was composited into PLA matrix and were further reduced when PBS was applied. After biodegradation via either enzymatic degradation or hydrolysis, surface erosion with a large number of voids, mass loss, and the substantial decrease in tensile strength of all the composites were observed. In addition, the biodegradation of the composites has been improved by the addition of either RH or PBS.     

Hydrolytic degradation of biobased poly(butylene succinate‐co‐furandicarboxylate) and poly(butylene adipate‐co‐furandicarboxylate) copolyesters under mild conditions

It is indispensable to investigate hydrolytic degradation behavior to develop novel (bio)degradable polyesters. Biobased and biodegradable copolyesters poly(butylene adipate‐co ‐butylene furandicarboxylate) (PBAF) and poly(butylene succinate‐co ‐butylene furandicarboxylate) (PBSF) with BF molar fraction (?_BF) between 40 and 60% were synthesized in this study. The hydrolytic degradation of film samples was conducted in a pH 7.0 PBS buffer solution at 25 °C. Slight mass loss (1–2%) but significant decrease in intrinsic viscosity (35–44%) was observed after 22 weeks. The apparent hydrolytic degradation rate decreased with increasing ?_BF and initial crystallinity. Meanwhile, PBAFs degraded slightly faster than PBSFs with the same composition. The ?_BF and crystallinity increased slowly with degradation time, suggesting the aliphatic moiety and the amorphous region are more susceptible to hydrolysis. And high enough tensile properties were retained after hydrolysis degradation, indicating PBAF and PBSF copolyesters are hydrolytically degradable, with tunable hydrolytic degradation rate and good balance between hydrolytic degradability and durability. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134 , 44674.     

Environmental usefulness of PLA/PEG blends for controlled-release systems of soil-applied herbicides

Blends consisting of biodegradable polylactide (PLA) and poly(ethylene glycol) (PEG) were investigated for their usefulness as an environmentally friendly herbicide formulation with prolonged activity. The aim of this study was to evaluate the release rate of selected soil-applied herbicides from the PLA/PEG blend containing PEG of various molecular weights and to assess the phytotoxicity of the PEGs according to OECD 208 guidelines. The release rate of immobilized herbicides was correlated with degradation of the blends used. The progress of PLA/PEG blend degradation in water, soil, and activated sludge was estimated by sample weight loss, changes in blend composition, and microscopic observations of the blend surfaces during the experiment. The proposed formulation of the immobilized herbicide in a blend consisting of slowly biodegradable PLA and water-soluble PEG provides the possibility to release the herbicides for a relatively long time, for approximately six months, which is a demand of weed management. The effect of PEGs on plant growth and development was dependent on both their concentration and molecular weight. With a higher concentration in soil and a higher molecular weight of PEG, a more harmful effect on plants was noticed. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47856.     

Development of biodegradable natural rubber latex composites by employing corn derivative bio-fillers

This study aims to investigate the viability of employing corn-based fillers (powdered corn grain [CG], corn flour [CF] and cornstarch [CS]) to improve the biodegradability of natural rubber latex (NRL) composites by varying filler loading from 0 to 50 phr. Notable variation in both physical and mechanical properties were observed for the different filler types, with CG-filled NRL demonstrating the better adhesion with NRL. Thus, CG-filled composites were selected for investigation of biodegradability. Increased CG loading in NRL compounds enhanced biodegradation; with over 70% degradation observed for 50 phr CG loading upon 15 weeks of soil burial. However, the trade-off between mechanical properties and biodegradability limits the CG loading in the NRL matrix to 20 phr for manufacturing NRL-based products. It was observed that NRL with CG filler loading of 20 phr conforms to the ASTM D3578 standard for manufacturing rubber gloves; with 50% biodegradation upon 15 weeks of soil burial.     

Sustainable biodegradable coffee grounds filler and its effect on the hydrophobicity,mechanical and thermal properties of biodegradable PBAT composites

Poly(butylene adipate‐co‐terephthalate) (PBAT) and coffee grounds (CG) wastes are biodegradable materials. The high cost of PBAT restricts its marketability; the lignocellulosic CG were used as a reinforcing agent for PBAT. Thus, the present work focuses mainly on the preparation and characterization of bio‐based PBAT composites filled with CG bio‐additives with affordable cost, and with potential use in a variety of eco‐friendly fields such as packaging, biomedical devices, and composting. The PBAT polymer was melt blended with various contents of CG powder using twin screw extrusion. The compatibility and dispersion state of investigated biocomposites in presence or absence of PEG as plasticizer were investigated by using scanning electron microscopy (SEM) and X‐ray diffraction (XRD). The effect of the addition of PEG on PBAT/CG was characterized by differential scanning calorimetry (DSC), tensile properties, contact angle measurements, and thermogravimetric analysis. The chemical interaction between hydroxyl groups of CG particles and PEG plasticizer was achieved by these techniques. A pyrolysis kinetic model was proposed to identify the kinetic parameters of the thermal degradation of PBAT and CG powder. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44498.     

Preparation and analysis of poly(l-lactic acid) composites with oligo(d-lactic acid)-grafted cellulose

α-Cellulose extracted from jute fiber was grafted with oligo( d -lactic acid) (ODLA) via a graft polycondensation reaction in the presence of para-toluene sulfonic acid and potassium persulfate in toluene at 130 °C for 9 h under 380 mmHg. ODLA was synthesized by the ring-opening polymerization of d -lactides in the presence of stannous octoate (0.03 wt % lactide) and d -lactic acid at 140 °C for 10 h. Composites of poly( l -lactic acid) (PLLA) with the ODLA-grafted α-cellulose were prepared by the solution-mixing and film-casting methods. The grafting of ODLA onto α-cellulose was confirmed by Fourier transform infrared (FTIR) spectroscopy and scanning electron microscopy (SEM). The analysis of the composites was performed with FTIR spectroscopy, SEM, wide-angle X-ray diffraction, and thermogravimetric analysis. The distribution of the grafted α-cellulose in the composites was uniform and showed better compatibility with PLLA through intermolecular hydrogen bonding. Only homocrystalline structures of PLLA were present in the composites, and the thermal stability increased with increasing percentage of grafted α-cellulose. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47424.     

Poly(lactic acid)/starch composites: Effect of microstructure and morphology of starch granules on performance

Starches used to develop biodegradable composites belong to different botanical sources that exhibit different microstructures and morphologies. This results in confused relationship and no comparison of data for applications. In this work, the most popular ten different starches were used as model materials to investigate the relationship between starch microstructure and the performance of poly(lactic acid) (PLA)/starch composites. It was found that: (a) composites filled with either well‐sized (small‐sized and non‐agglomerated) starch granules or those containing high amylose content (G‐50 and G‐80) improves the reinforcing ability of PLA, with least reduction in deformation; (b) aggregation tendency of small‐sized starch granules can be controlled using surface modification approach that not only reduces the phase‐separation between starch and PLA but also improves the dispersion; and (c) no discernible relationship exists between the starches, from different botanical sources, and the thermal performance of PLA/starch composites. The results provide practical guidelines to develop starch‐based biodegradable composites for commercial applications. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45504.     

In situ chemically crosslinked chitosan membrane by adipic acid

Adipic acid, which is nontoxic, was used to dissolve chitosan. The chitosan/adipic acid solution was used to prepare chitosan membrane. After being heated at 80–100°C, the membrane was in situ chemically crosslinked by adipic acid, as verified by Fourier transform infrared and wide‐angle X‐ray diffractometer analysis. The crosslinked membrane did not collapse even without treatment in alkaline solution. In addition, the in situ crosslinking reaction was studied. The crosslinking degree (CLD) was quantitatively calculated based on the mass of water produced. The results showed that CLD was positively related to both heating temperature and time. Results of kinetic of crosslinking reaction suggested that the amidation was in agreement with the first‐order rate equation and that the temperature effect could be described with the Arrhenius equation. The results of weight loss of chitosan membrane in phosphate‐buffered solution (pH = 7.4) indicated that the best water resistance of chitosan membrane was obtained at 90°C. In brief, a straightforward, nontoxic, environment‐friendly, and economical chemically crosslinking approach has been developed for chitosan materials. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Thermo-responsive shape memory properties based on polylactic acid and styrene-butadiene-styrene block copolymer

This study aims to compare thermal, mechanical, and shape memory behavior of polylactic acid (PLA) blended with different structures of styrene-butadiene-styrene block copolymer (SBS), namely linear SBS (L-SBS), and radial SBS (R-SBS). The amount of L-SBS and R-SBS added was varied between 10 and 70 wt%, and the blending process was carried out using an internal mixer at 180°C before the shaping process by the compression molding. An improvement in the degree of crystallinity was observed across the entire composition range with less pronounced transition temperature change. Tensile strength and modulus of PLA/L-SBS blends were higher than PLA/R-SBS blends across all composition ranges. The results also revealed that the shape fixing ratio (R_f) and recovery ratio (R_r) of PLA/L-SBS were higher than PLA/R-SBS, with PLA70/SBS30 showed the best shape memory behavior. The morphology characteristics of the blend were also examined with the scanning electron microscope.     

Effect of dicumyl peroxide on biodegradable poly(lactic acid)/functionalized gum arabic based films

Blending of poly (lactic acid) (PLA)/functionalized gum arabic (FG) in presence of dicumyl peroxide (DCP) presents a simple process to produce film using melt extrusion (recycle time ~ 4 min, screw speed ~60 rpm) at 180°C with tailored characteristics. The FTIR investigation shows that the confirmation of grafting of PLA chains on FG through formation of new C─C linkage. Properties of fabricated films such as morphological, mechanical, UV barrier and contact angle are examined to develop film with improved interfacial interaction, increased toughness, UV–C blocking effect (~95%) and hydrophobicity (~14%). Polarized optical microscopy (POM) studies reveal that PLA/1FG with and without DCP has more crystal density as compared to PLA at 120°C. This melt extrusion permits straightforward, feasible bionanocomposite film and has great potential as a modification with DCP assists to overcome particular drawbacks of FG.     

Degradation studies during water absorption,aerobic biodegradation,and soil burial of biobased thermoplastic starch from agricultural waste/polypropylene blends

Thermoplastic starch (TPS) from agricultural waste consisting of different amylose/amylopectin ratios was blended with polypropylene (PP) for degradation studies. The agricultural waste material was obtained from seeds and tubers with low starch contents of ～50%. Non‐Fickian behavior was observed for the water absorption test, and water uptake increased with increases in amylopectin content. The biodegradation was assessed based on the extent of carbon conversion, and was found to be dependent on the water absorption behavior and molecular structure of the starch component. Outdoor soil burial showed greater weight loss and deterioration in tensile properties compared to indoor soil burial. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Fully bio‐based polyesters derived from 2,5‐furandicarboxylic acid (2,5‐FDCA) and dodecanedioic acid (DDCA): From semicrystalline thermoplastic to amorphous elastomer

A serials of fully bio‐based poly(ethylene dodecanedioate‐2,5‐furandicarboxylate) (PEDF) were synthesized from Dodecanedioic acid (DDCA), 2,5‐Furandicarboxylic acid (2,5‐FDCA), and ethylene glycol through a two‐step procedure consisted of transesterification and polycondensation. After their chemical structures were confirmed by Nuclear Magnetic Resonance and Fourier Transform Infrared Spectroscopy, their thermal, mechanical, and biodegradation properties were investigated in detail. Results showed that the chemical composition of PEDFs could be easily controlled by the feeding mole ratio of DDCA to FDCA and they possessed the characteristic of random copolyester with the intrinsic viscosity ranged from 0.82 to 1.2 dL/g. With the varied mole ratio of DDCA to FDCA, PEDFs could be changed from semicrystalline thermoplastic to the completely amorphous elastomer, indicated by the elongation at break ranged from 4 for poly(ethylene 2,5‐furandicarboxylate) to 1500% for amorphous PEDF‐40. The amorphous PEDF‐30 and PEDF‐40 showed satisfactory shape recovery after cyclic tensile test, which was the typical behavior for elastomer. Enzymatic degradation test indicated that all the PEDFs were biodegradable and the degradation rate was heavily affected by their chemical compositions. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46076.