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The nutshell waste streams (pine nut shells (PNS), walnut shells (WNS), and almond shells (ANS)) were effectively converted into biocarbon materials employing slow pyrolysis in a fixed bed horizontal reactor at 500 and 900 °C with a 10 °C min−1heating rate and 60 min holding time. The acquired biocarbon materials were then characterized to understand the influence of pyrolysis temperature on their ash content, elemental composition, thermal stability, graphitic content, functionality, surface morphology, and electrical conductivity. The obtained results established that the pyrolysis temperature has a leading impact on the yield and physicochemical properties of biocarbon. Increasing the pyrolysis temperature of PNS, WNS, and ANS from 500 to 900 °C, respectively, decreases the biocarbon yields from 32, 28, and 28 wt.% to 28, 24, and 25 wt.%. Furthermore, the increasing pyrolysis temperature increases the carbon content and purity of PNS, WNS, and ANS biocarbon due to the elimination of oxygen. Thus, the electrical conductivity of PNS, WNS, and ANS biocarbon acquired at 900 °C was significantly higher than 500 °C. Overall, it can be surmised that biocarbon prepared at a higher temperature is preferable for material applications due to its greater characteristics.

Graphical abstract:

•Lemon peel was converted to porous carbon via chemical activation at 800 °C.•Activation with KOH and alum exhibited higher BET surface area of 2143 m2/g.•Distribution of micropores in activated carbons significantly affected CO2adsorption.•KOH activation improved micropore distribution, enhancing CO2adsorption to 4.56 mmol/g.

This article assesses the performance of a biobased carbon as a nucleator using common techniques to stimulate poly(lactic acid) crystallization and enhance the thermal stability of PLA during injection molding. The combination of a biodegradable plasticizer, poly(ethylene glycol) (PEG), along with biobased carbon-rich pyrolyzed biomass char residue and an industrially available microcrystalline talc, were tested for nucleating agent capabilities at additions of 10 wt%. Differential scanning calorimetry (DSC) data demonstrated that the inclusion of the plasticizer could increase the PLA crystalline content with further improvements when nucleating agent was present. With a higher mold temperature, the PLA crystallinity surpassed 40% for the multicomponent formulations. The thermomechanical properties including heat deflection temperature exhibited performance above 100 °C, while the coefficient of thermal expansion was lowered. Optical analysis of the crystal structure showed increased crystallization rate with plasticizer and nucleating agents. The mechanical properties and morphology characteristics are also presented.

•A novel, adsorption based route for CO2utilization and CO2capture is proposed.•Individual and mutual effect of KOH and CO2on pine sawdust activation was tested.•Maximum BET surface area of 2216 m2/g was achieved.•Highest CO2adsorption capacity of 6.35 mmol/g at 0 °C/1 bar was measured.•CO2/N2selectivity was found to be within 10-19.

Biocomposites from poly(butylene succinate) (PBS) and perennial grass (miscanthus fibers) were successfully prepared by extrusion and injection molding methods with different fiber loadings. The tensile strength of uncompatibilized PBS/miscanthus composites was much lower compared to that of neat PBS. Unlike tensile strength, the flexural and impact strengths were significantly enhanced after incorporation of miscanthus fibers into the PBS matrix. The enhanced flexural strength was attributed to the reinforcing effect of miscathus fibers. The fiber pull-out mechanism is likely responsible for the observed impact strength improvement. Addition of 5 wt % maleic anhydride (MAH) grafted PBS (MAH-g-PBS) into PBS composites showed a significant improvement in tensile and flexural strength compared to the corresponding uncompatibilized composites and neat matrix. For example, the PBS composites with 50 wt % miscanthus fiber and 5 wt % MAH-g-PBS resulted in 22, 139, and 47% improvements in tensile, flexural, and impact strength compared to neat PBS. These improvements were attributed to the enhanced interfacial interaction between the components, as confirmed by adhesion parameter values and by surface morphological analysis. The load-bearing capacity of the compatibilized and uncompatibilized PBS/miscanthus composites was analyzed using a mathematical model. Overall, this study provides an option for preparing a sustainable biocomposite with superior mechanical and thermo-mechanical properties.

Poly(lactic acid) (PLA), one of the widely studied renewable resource based biopolymers, has yet to gain a strong commercial standpoint because of certain property limitations. This work is a successful attempt in achieving PLA biocomposites that showed concurrent improvements in impact strength and heat deflection temperature (HDT). Biocomposites were fabricated from a super toughened ternary blend of PLA, poly(ether-b-amide) elastomeric copolymer and ethylene-methyl acrylate-glycidyl methacrylate and miscanthus fibers. The effects of varying the processing parameters and addition of various nucleating agents were investigated. Crystallinity was controlled by optimizing the mold temperature and cycle time of the injection process. With the addition of 1 wt % aromatic sulfonate derivative (Lak-301) as a nucleating agent at a mold temperature of 110 °C, PLA biocomposites exhibited dramatic reduction in crystallization half time to 1.3 min with crystallinity content of 42%. Mechanical and thermal properties assessment for these biocomposites revealed a 4-fold increase in impact strength compared to neat PLA. The HDT of PLA biocomposites increased to 85 °C from 55 °C compared to neat PLA. Crystallization behavior was studied in detail using differential scanning calorimetry and was supported with observations from wide-angle X-ray diffraction profiles and polarized optical microscopy. The presence of a nucleating agent did not alter the crystal structure of PLA; however, a significant difference in spherulite size, crystallization rate and content was observed. Fracture surface morphology and distribution of nucleating agent in the PLA biocomposites were investigated through scanning electron microscopy.

Multiphase blends of poly(lactic acid) (PLA), ethylene-methyl acrylate-glycidyl methacrylate (EMA-GMA) terpolymer, and a series of renewable poly(ether-b-amide) elastomeric copolymer (PEBA) were fabricated through reactive melt blending in an effort to improve the toughness of the PLA. Supertoughened PLA blend showing impact strength of ∼500 J/m with partial break impact behavior was achieved at an optimized blending ratio of 70 wt % PLA, 20 wt % EMA-GMA, and 10 wt % PEBA. Miscibility and thermal behavior of the binary blends PLA/PEBA and PLA/EMA-GMA, and the multiphase blends were also investigated through differential scanning calorimetric (DSC) and dynamic mechanical analysis (DMA). Phase morphology and fracture surface morphology of the blends were studied through scanning electron microscopy (SEM) and atomic force microscopy (AFM) to understand the strong corelation between the morphology and its significant effect on imparting tremendous improvement in toughness. A unique “multiple stacked structure” with partial encapsulation of EMA-GMA and PEBA minor phases was observed for the PLA/EMA-GMA/PEBA (70/20/10) revealing the importance of particular blend composition in enhancing the toughness. Toughening mechanism behind the supertoughened PLA blends have been established by studying the impact fractured surface morphology at different zones of fracture. Synergistic effect of good interfacial adhesion and interfacial cavitations followed by massive shear yielding of the matrix was believed to contribute to the enormous toughening effect observed in these multiphase blends.

Lignocellulosic composites have attracted interest from both academia and industry due to their beneficial environmental and sustainability attributes. The lignocellulosic industry has seen remarkable improvements in the development of composites for high performance applications. Both biodegradable as well as non-biodegradable polymers are used in the design and engineering of lignocellulosic composites. Biodegradability studies of lignocellulosic composites in soil and composting environments help in planning their end-life management. Biodegradability tests are complex and dependent on the environment in which the testing is carried out. Due to this, standards have been developed by international agencies such as the American Society for Testing and Materials (ASTM) and International Organization for Standardization (ISO) to adopt and test plastic materials in both composting and soil environments. The first part of this intended review article deals with the classification of lignocellulosic composites, biodegradation and composting concepts, biodegradability testing standards, and factors affecting biodegradation. A comparative analysis of ASTM and ISO biodegradability standards in terms of testing methodology and results interpretation is provided. A special focus is given to the biodegradation mechanisms found in polymers and their composites. The second part of this review article is devoted to biodegradation studies of lignocellulosic composites under composting conditions and soil environments. The effect of filler type, environmental conditions, and compatibilization on the biodegradation of lignocellulosic composites is discussed in detail. Also, a special section on the biodegradability of lignin-based materials is given.

This study investigated the use of potassium persulfate (KPS) as an initiator for the grafting of methyl methacrylate (MMA) onto softwood kraft lignin. Ammonium iron (II) sulfate hexahydrate was used as a catalyst to overcome the inherent inhibition of lignin to free radical grafting and to make lignin copolymer under mild conditions using an aqueous medium. The influence of temperature, initiator concentration, time of reaction and monomer concentration on percentage of grafting were studied. A maximum of 31% grafting was achieved at 55°C. Graft copolymer was identified from the Fourier transform infrared (FTIR) spectrum by the new absorption peak at 1723 cm-1and the reduction of intensity of the band around 3350 cm-1. The reduction of glass transition temperature (Tg), surface morphology and higher decomposition temperature of grafted lignin support the grafting of MMA on lignin. The grafted chains increased the surface area of lignin.

A ternary blend of entirely biodegradable polymers, namely polylactide (PLA), poly(3-hydroxybutyrate-co-hydroxyvalerate) (PHBV), and poly(butylene succinate) (PBS), was first melt-compounded in an effort to prepare novel fully biodegradable materials with an excellent balance of properties. The miscibility, morphology, thermal behavior, mechanical properties, and thermal resistance of the blends were investigated. DMA analysis revealed that PHBV and PLA showed some limited miscibility with each other, but PBS is immiscible with PLA or PHBV. Minor phase-separated structure was observed from SEM for all the blends composition except PHBV/PLA/PBS 60/30/10 blend, which formed a typical mixture of core–shell morphology. The morphologies were verified by analysis of the spreading coefficients. Excellent stiffness–toughness balance was achieved by ternary blends of PLA, PHBV, and PBS. Significant enhancement of the toughness and flexibility of PLA was achieved by the incorporation of PBS and PHBV without sacrificing the strength apparently. Both the stiffness and toughness were improved for PHBV in the ternary blends with PHBV as matrix. The crystallization of the PLA and PBS were enhanced by presence of PHBV in the blends, while the crystallization of PHBV was confined by PLA and PBS phases. Moreover, the thermal resistances and melt flow properties of the materials were also studied by analysis of the heat deflection temperature (HDT) and melt flow index (MFI) value in the work.

A synergistic effect of simultaneous plasticization and destructurization of soy protein in melt extrusion is studied using soy meal, glycerol, and urea. The combined effect of plasticization and destructurization yields thermoplastic soy meal (TSM) that is capable of chemical interactions with biodegradable polyesters. Melt‐compounded blends of TSM with biodegradable polyesters give new ductile bioplastics. The observed improvement in the properties of these blends might be due to two reason; the high elasticity of the destructured soy meal and the compatibility between the polyesters used. The synergistic effect of unfolding and destructurization of the protein by urea leads to high mobility in the protein chains of the soy meal.

A blend composition of poly(3‐hydroxybutyrate‐co‐valerate) and polylactide is used as a bioplastic matrix and reinforced with soy hull to engineer novel green composites. A comparative study with soy‐hull‐reinforced polypropylene composite system is performed. A compatibilizer is used to engineer the novel class of green composites with a balanced stiffness and toughness performance with the target to substitute PP‐based composites. The flexural and impact strength along with hydrophobicity of compatibilized composites are improved significantly over the noncompatibilized counterpart. The fiber/matrix interaction is investigated by SEM. These green composites have the potential to substitute PP‐based composites in some applications.

Biodegradable green composites from distiller's dried grains with solubles (DDGS), a major coproduct of the corn ethanol industry, and a polyhydroxy(butyrate‐co‐valerate) (PHBV)‐based bioplastic were successfully produced. Green surface treatment of DDGS was performed and thermogravimetric analysis showed noticeable improvement in the degradation onset temperature of DDGS from 140 to 235 °C; this was a key point during melt processing of the composite. Utilizing compatibilizer improved the adhesion between DDGS and the matrix, which was observed by scanning electron microscopy. The green composite containing treated and compatibilized DDGS showed an enhanced modulus (by about 28% from 1.77 to 2.26 GPa) and an improved heat deflection temperature (by about 21% from 109 to 132 °C) compared to the polymeric matrix, while having tensile and flexural strengths equal to or greater than the respective properties of the matrix.

Blends of plasticized soy protein isolate (PSPI) and poly(butylenes succinate) (PBS) were prepared in a 70:30 wt.‐% ratio via co‐rotation (CR) and counter‐rotation (CTR) twin‐screw extrusion. The novelty in this research suggests that CTR extrusion provides enhanced interfacial adhesion, tensile elongation and prolonged onset (Tonset) and end (Tend) thermal degradation temperatures. The average tensile strain at break showed to be ≈40% higher for PSPI‐CTR material and ≈55% higher for PBS:PSPI‐CTR (70:30) blends. Both Tonsetand Tendfor CTR processed PBS:PSPI(70:30) and PSPI were ≈10 °C greater than those of CR. These results suggest that the enhanced shear rate and radial motion associated with CTR allows for better destructurization and blending of PSPI within the PBS matrix, resulting in enhanced structural integrity due to the formation of possible amide and ester linkages. Scanning electron microscopy (SEM) provides further support based on evidence of reduced voids on the surface of all CTR blends

The effects of process engineering in the fabrication of PHBV, PLA and their blends prepared by melt blending are studied. The elongation of an optimized blend can be improved by 148 and 250% over the virgin PHBV and PLA polymers, respectively. DSC shows that the two polymers are immiscible in blends of any composition. The crystallinity of PHBV is hindered by the presence of PLA. UV‐Vis demonstrates the opacity of the blend with incorporation of PHBV to the PLA phase. The observed tensile modulus of the optimized sample is compared with theoretical values from the rule of mixtures. Gordon‐Taylor's equation is applied on the glass transition temperatures for theoretical modeling to explain the miscibility of the polymers.

In this study, the use of PLA‐g‐MA is investigated as a potential method for improving interfacial adhesion between agricultural residues and PLA, with the goal of enhancing mechanical properties. Compatibilization was achieved by using PLA‐g‐MA prepared via reactive extrusion. Green renewable and compatibilized PLA/wheat straw composites were extruded and injection‐molded. Addition of 3 and 5 phr PLA‐g‐MA to the composites resulted in significant improvements in tensile strength (20%) and flexural strength (14%) of the composites, matching that of the neat polymer. The observed improvement in strength was attributed to the good interfacial adhesion between the fiber and matrix.

Bare and carbon coated nanorods were synthesized by modified polyol and resin coating processes to enhance their conductivity as well as their electrochemical properties. X-ray diffraction, Fourier transform infrared, scanning electron microscope, and transmission electron microscope results confirmed crystalline phase, structure, and uniform coating of carbon over nanorods, respectively. Raman spectra of carbon coated nanorods showed two bands (D and G bands) due to the presence of carbon, which was not observed in the bare nanorods. Conductivity and mobility results showed more than 2 orders of magnitude enhancement of electronic conductivity in the carbon coated nanorods compared to the bare one and it is attributed to the presence of carbon over nanorods. CR2032-type lithium ion coin cells were fabricated using bare and carbon coated nanorods and characterized by measuring charge-discharge cycles between 2.9 and at room temperature. Both cells exhibit high capacity and good cyclability. The improved capacity was attributed to a one dimensional electron transport pathway in nanorods. Further improvement in the capacity, up to at (25%), was also achieved in the carbon coated nanorods synthesized using modified polyol and resin coating processes.

Natural fiber reinforced polymer composites are lightweight, economical and available in a variety of forms. They have low densities, comparable material properties, high molding flexibility and are environmentally friendly, making them a conceivable alternative to traditional fillers like mica, calcium carbonate and glass. By modifying either the resin system or the natural fiber, biocomposites can be designed for different applications ranging from products of commodity to aerospace, examples including electroactive papers, fuel cell membranes, controlled drug release mechanisms and biosensors. This review aims to analyze the advancement in the application of cellulose based materials in different sectors with a discussion of fundamental research in these areas.

The influence of talc loading on phase morphology of PLAPCLtalc composites and improvement in resulting properties are reported. Talcbased composites of PLAPCL blends were prepared by melt blending. SEM analysis demonstrates that PLA appears as discrete domain phase, while PCL acts as a bulk phase in the blend. Talc addition decreases PLA domain sizes and voids in the matrix. This results in significant improvement of oxygen and water vapor barrier properties of composite by 33 and 25, respectively, at 3 wt. talc loading. DSC shows that talc acted as nucleating agent for PCL phase in the composite and improves its crystallinity. Various theoretical models based on dispersion and filler geometry are used to predict the tensile modulus and oxygen permeability.

Polylactic acid (PLA) based biocomposite films, reinforced with different loadings of organoclay, were prepared by solution casting method. Four different loadings of clay was done, 2, 5, 10 and 15 weight% with respect to the matrix. These biocomposite films were characterized by mechanical characterization, scanning electron microscopy (SEM) moisture diffusivity property at 93% RH. Both the mechanical and the visco-elastic property of these films were measured by nano indentation technique. Mechanical property by nano indentation analysis revealed an idea about the extent of clay dispersion in the matrix. The amount of clay loading and its dispersion significantly affected the mechanical as well as the Visco-elastic behavior of the biocomposite films. The morphology of the films were observed with the help of SEM.

PHA-based extruded films were developed by blending PHAs with thermoplastic starch using extensive process engineering based on structureproperty correlations. Starch was destructurized and plasticized followed by meltblending with PHA and PBAT. Dynamic mechanical analysis coupled with Gibbs free energy values indicated that the starch plastic was performing the role of a dual compatibilizer in between the PHA and the PBAT phases in the blend. Aging, an inherent problem with starchbased materials and PHAbased materials, was effectively reduced by limiting the moisture uptake of the starch component, hindering the leaching of glycerol and inhibiting the secondary crystallization of the PHA component in the films.

Vulcanized blends from soy meal and natural rubber were successfully processed through semi-pilot scale extrusion, roll milling and compression‐molding. Blends containing about 50 wt.‐% of soy meal are elastic and water resistant, compared with the brittle and hydrophilic soy meal. The natural rubber component was well embedded into the soy meal matrix, indicating the existence of an interaction between them. The glass transition temperature of the rubber component in the blends increased due to the existence of this interaction. Calcium sulfate, as a compatibilizer, was a physical cross‐linker to the proteins in the soy meal and in the rubber. The morphological analysis of the soy meal and natural rubber blend through scanning electron microscopy revealed a partial compatibility of the blend. The blends containing near 50 wt.‐% of inexpensive soy meal have potential for various applications.

Starch/poly(vinyl alcohol) films plasticized with glycerol were prepared by a solution-casting method and were used as the matrix material for making jute‐fabric‐reinforced starch‐based composites. Four sets of composites were prepared with a variation in the matrix composition, all having 40 wt.‐% jute fabric as the reinforcement. The mechanical properties were superior in the case of the matrices containing a higher amount of starch. DMA was done to investigate the nature of bonding at the interface. The fracture surfaces were examined by SEM. Intimate bonding of the jute fibers with the matrix was evident. The clay‐filled matrices displayed a flat crack surface without any plastic deformation.

Summary: Vinylester resin matrix composites were fabricated with 1, 3, 5 and 10 wt.-% loadings of organoclay. The composite samples were subjected to various characterization techniques like X‐ray diffraction, flexural testing, dynamic mechanical analysis, thermogravimetric analysis, and scanning electron microscopy. The clay samples as well as the clay–resin composites were investigated by X‐ray diffraction. From the shift in the peak positions and the change in d‐spacing values, it was evident that there was intercalation in the 10 wt.‐% composites, whereas exfoliation occurred in the 1, 3, and 5 wt.‐% composites. The flexural strength and the breaking energy of all the composites were decreased compared with the unfilled resin, but there was an increase in flexural modulus value by 13%. From the dynamic mechanical analysis of the 3 and the 5 wt.‐% composites, it was observed that the loss modulus value was higher in the 3 wt.‐% composites, but the glass transition temperature was slightly higher in the 5 wt.‐% composites. Thermal degradation behavior was also improved in the 5 wt.‐% composites compared with the 3 wt.‐% composites.Fracture surface of 3 wt.-% clay filled vinylester resin matrix composite in different magnifications.

Talc-filled composites of a bacterial polyester, i.e., poly(3-hydroxybutyrate-co-3-hydroxyvalerate), PHBV, were prepared by extrusion followed by an injection molding process. The effects of the talc weight content (15−50 wt %) on various mechanical and thermomechanical properties of the PHBV-based composites were studied. The tensile and flexural moduli of PHBV-based composites were improved by 70 and 166%, respectively, when reinforced with a talc content of 50 wt %. Theoretical predictions were used to compare the experimental tensile modulus values of talc-filled PHBV composites. Comparison of the experimental results with theoretical predictions predominantly favored a spherical geometry of the talc particles in the PHBV matrix rather than a platy morphology. The storage modulus (E‘) and heat deflection temperature (HDT) of the PHBV-based composites were found to increase when the composites were reinforced with talc particles. The coefficient of linear thermal expansion (CLTE) of PHBV was reduced by 56% for the composite reinforced with a talc content of 50 wt %. The filler orientation, filler dispersion, and filler−matrix adhesion were investigated by scanning electron microscopy (SEM).

Bioplastics from soy protein and biodegradable polyester amide with plasticizers including glycerol, d-sorbitol, and blends of these two have been made using extrusion and injection molding. The thermal properties, mechanical properties, and morphologies of the soy-based bioplastics were evaluated with a dynamic mechanical analyzer (DMA), a united testing system (UTS), and an environmental scanning electron microscope (ESEM). The influence of plasticizers on the physical properties of the soy-based bioplastics was determined. It was found that sorbitol-plasticized soy-based bioplastic (SSBP) had a higher tensile modulus and tensile strength than glycerol-plasticized soy-based bioplastic (GSBP). GSBP had the highest impact strength, whereas SSBP had the highest thermal stability. The mixed plasticized soy-based bioplastic (MSBP) that was obtained using a mixture of glycerol and d-sorbitol showed an intermediate range of tensile modulus and tensile strength values in comparison to those of SSBP and GSBP. The ESEM results suggested that SSBP had brittle fracture features, whereas GSBP had local ductile fracture features, which is consistent with the results obtained for the mechanical properties. The glass transition temperatures from DMA measurements of the soy protein and polyester amide in the soy-based bioplastics differed from those of the neat components. Using Fox equation calculations, this was interpreted as compatibility between the soy protein and polyester amide, which causes thermal and mechanical changes in different soy-based bioplastics.