Novel polylactide/triticale straw biocomposites: Processing,formulation, and properties

This article aims to the development of polylactide (PLA)/triticale straw biocomposites with focus on the relationship between triticale straw content, additive presence, processing, and final properties. Prior to melt compounding, the triticale straw used in this study was chopped using the paper process to produce triticale particles that were further pelletized to assure a consistent feed rate into the extrusion line. PLA/triticale straw biocomposites were obtained for different triticale contents from 10 up to 40%vol, without and with maleic anhydride grafted polylactide (PLA‐g‐MA) as a coupling agent. As a supplementary additive, a PLA‐specific branching agent was used in some selected formulations to minimize the reduction in PLA's molecular weight. The biocomposites were characterized in terms of rheology, thermal properties, morphology, mechanical properties (tensile, flexural, and impact), and recyclability. The PLA‐g‐MA increased the tensile strength of biocomposites by 10%, whereas boosted the tensile modulus about 2.5 times at 40%vol triticale content. For the same formulation, the flexural strength was raised by 15% and flexural modulus was doubled. However, a combination of PLA‐g‐MA and branching agent proved to be the best approach to enhance PLA/triticale straw mechanical properties. When 20%vol of triticale was used as reinforcement, the presence of branching agent increased the flexural strength about 25%. The results demonstrate that the triticale straw processed in this way could offer a similar reinforcement capability as the cellulosic fibers based on the agricultural and forestry resources and can be easily recycled without losing its mechanical properties. It has a good potential in the biocomposites field with promising applications in construction, common goods, and transportation industries. POLYM. ENG. SCI., 54:446–458, 2014. © 2013 Society of Plastics Engineers     

Processing and characterization of waste leather based polycaprolactone biocomposites

Waste leather buff (WLB) filled polycaprolactone (PCL) composites were prepared by twin‐screw extrusion varying the WLB content from 2% to 40%. These composites were extensively characterized by several techniques in order to establish micro and macroscopic properties. Addition of WLB resulted in improvement of tensile modulus of neat PCL and reduction in percentage crystallinity of PCL matrix was observed with increase in WLB content. Interfacial adhesion and dispersion of WLB on PCL matrix was investigated using Scanning Electron Microscope. Percentage of water uptake increased with increase in concentration of WLB in the composite. These biodegradable composites could be used to develop low cost materials suitable for applications in footwear industry, for making bags, suitcases, etc., eliminating the environmental issues arising from WLB generated from tanneries in leather industry. POLYM. COMPOS., 38:2889–2897, 2017. © 2015 Society of Plastics Engineers     

In vitro properties of nano-hydroxyapatite/chitosan biocomposites

In vitro behavior of the composites was performed in simulated body fluid (SBF) to induce the formation of bone-like apatite layer onto their surfaces and its enhancement in the presence of citric acid (CA). The results proved the mineralization of calcium (Ca²⁺) and phosphorus (P) ions onto the composites which contain high chitosan concentration especially after longer time of immersion. The degradation data decreased with increase chitosan content especially C2 composites (containing 30% chitosan) and highly decreased in the presence of CA which increased binding strength through the composite. The swelling % increased with increase of chitosan content in HA composite but it decreased with CA addition as increase of interaction between three matrices. The Fourier Transformed Infrared Spectroscopy (FT-IR) and Scanning Electron Microscope (SEM-EDAX) confirmed the formation of bone-like apatite layer on the surface of the composites especially these containing CA. These biocomposites have unique in vitro properties for bone substitute's applications in the future.     

Polypropylene and potato starch biocomposites: Physicomechanical and thermal properties

To determine the possibility of using starch as biodegradable filler in the thermoplastic polymer matrix, starch‐filled polypropylene (PP) composites were prepared by extrusion of PP resin with 5, 10, 15, and 20 wt % of potato starch in corotating twin‐screw extruder. The extruded strands were cut into pellets and injection molded to make test specimens. These specimens were tested for physicomechanical properties such as tensile and flexural properties, Izod impact strength, density, and water absorption. These PP composites were further characterized by melt flow index (MFI), vicat softening point (VSP), differential scanning calorimetry (DSC), and thermogravimetric analysis (TGA) techniques. It was found that, with increase in starch content, tensile modulus, flexural strength, and flexural modulus of the PP composites increased along with the increase in moisture, water absorption, and density, while retaining the VSP; but, tensile strength and elongation, impact strength, hardness, and MFI of the PP composites also decreased. DSC analysis of the PP composite revealed the reduction in melting temperature, heat of fusion, and percentage of crystallization of PP with increase in starch content. Similarly, TGA traces display enhanced thermal degradability for PP as starch content increases. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Effect of processing conditions on mechanical and viscoelastic properties of biocomposites

To study the effects of processing conditions on the viscoelastic and mechanical properties of biodegradable composites, we prepared several composites based on sisal fibers and biodegradable polymers. The effects of processing conditions such as the speed of rotation, temperature, and time of mixing were investigated. The mechanical and viscoelastic properties of these composites were affected by the processing conditions. This was principally due to the modification of the initial aspect ratio of the natural fibers as a result of the shear stresses that developed in the mixer during the compounding. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 1637–1642, 2003     

Effect of core–shell acrylate rubber particles on the thermomechanical and physical properties of biocomposites from polylactic acid and olive solid waste

Biocomposites from polylactic acid (PLA) and olive solid waste (OSW) were melt‐blended with core–shell acrylate rubber particles (ACR) in order to enhance the thermal stability upon melt processing and the mechanical performances of these biocomposites, thereby expanding their area of application. Dynamic mechanical analysis indicated that the ACR particles imparted more flexibility to the PLA/OSW biocomposites and thermal analysis showed that the incorporation of ACR significantly restrained the ability of the PLA chains to crystallize. The values of complex viscosity and storage modulus were significantly increased with the introduction of ACR. These results could be assigned to the entanglements between the PLA chains and those of the ACR shell, giving rise to a physical network that limited the segmental mobility of PLA and induced a high melt elasticity. Mechanical tests revealed that the elongation at break and the impact strength of the biocomposites were considerably improved. Moreover, morphological observations showed a clear adhesion enhancement between the PLA matrix and the OSW fillers in the presence of the ACR additive. POLYM. ENG. SCI., 58:894–902, 2018. © 2017 Society of Plastics Engineers     

Hybrid biocomposites with enhanced thermal and mechanical properties for structural applications

The current work focuses on enhancing the mechanical and thermal properties of sisal fiber reinforced composites that were previously used in developing interior automotive trims. In order to extend their use in other structural applications, two hybrid biocomposites with the combination of sisal (SF) and glass fiber (GF)‐SF20/GF10 and SF10/GF20 were blended with polypropylene via extrusion and injection molding process. Critical material properties such as density, fogging, acoustic, mechanical, thermal, and rheological properties were evaluated and results were analyzed using ANOVA. Hybridization of SF and GF enhanced flexural strength and thermal properties of the biocomposites by 33 and 19%, respectively, while no significant change in acoustic, impact and rheological properties were observed. The properties of the hybrid biocomposites were compared with the material specification of a battery tray and it was found that these hybrid biocomposites could be better alternative materials in structural applications. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42452.     

Processing and characterization of jute fiber reinforced hybrid biocomposites based on polylactide/polycaprolactone blends

The main focus of this work is to develop biocomposites with improved stiffness and toughness. For this purpose, hybrid biocomposites composed of surface modified jute fiber and varying weight fractions of polylactide (PLA) and polycaprolactone (PCL) are fabricated by hot pressing of solvent impregnated prepregs. Mechanical, thermal (DSC), viscoelastic properties and biodegradation of the developed biocomposites were evaluated. Surface modification of the jute fiber resulted in improvement of tensile strength and modulus and reduction in impact toughness along with vibration damping capacity. The addition of biodegradable resin PCL to PLA matrix leads to recovery of the impact toughness and damping capacity of the biocomposites, without much sacrifice in stiffness and strength. Hybrid biocomposite with 10 wt% PCL attained an optimum balance between stiffness and toughness. In addition, PCL also accelerated the biodegradation rate of the composites. POLYM. COMPOS., 2012. © 2011 Society of Plastics Engineers     

Preparation and properties of rice husk‐filled plasticized wheat gluten biocomposites

Rice husk (RH) reinforced wheat gluten/glycerol (Gly/Glut) and rice husk (R) reinforced wheat gluten‐glycerol/chitosan‐polyethylene glycol (Gly/Glut‐CP) biocomposites with varying rice husk loading were prepared. Morphological, thermal, and mechanical properties of the biocomposites were investigated by scanning electron microscope, thermogravimetric analyzer, and tensile testing machine, respectively. Water absorption properties and surface functional groups of the biocomposite films were determined by weight measurement and attentuated total reflectance Fourier transform infrared spectroscopy, respectively. The results were discussed in terms of chitosan‐polyethylene glycol (CP) and rice husk content. Although CP and 1‐g rice husk addition decreased maximum degradation temperature of Gly/Glut film, adding of more rice husk did not considerably change the maximum degradation temperature. As a result of adding CP, the tensile strength of Gly/Glut film was increased by about 183%, whereas tensile modulus was decreased by about 34%. POLYM. ENG. SCI., 54:1477–1483, 2014. © 2013 Society of Plastics Engineers     

Thermal and thermomechanical properties of biocomposites made from modified recycled cellulose and recycled polypropylene

Residual cellulose fibers from the paper industry have been used as reinforcements in recycled polypropylene (PP) composites. The main obstacle to obtaining good properties with this biocomposite is deficiencies in the compatibility between the nonpolar matrices and the polar cellulose fibers used as reinforcements. The aim of this work was to improve the compatibilization between these cellulose fibers and the PP matrix with four different methods: modification by the addition of polypropylene–maleic anhydride copolymer (PPgMA) during the process of blending, preblending modification of the cellulose with a solution of PPgMA, modification of cellulose by silanes (vinyltrimethoxysilane), and acetylation of cellulose. Blends with all of the differently modified celluloses were prepared with the cellulose content varied up to 40%, and then all of the blends were subjected to thermal (differential scanning calorimetry and thermogravimetric analysis) and thermomechanical (dynamic mechanical thermal analysis) analyses. The results showed that the addition of cellulose fibers improved the thermomechanical behavior of the PP, increasing the value of the log of the dynamic modulus, and affected the thermal and thermooxidative behavior. Moreover, an advantage of the use of a recycled PP containing a small quantity of ethyl vinyl acetate (EVA) as a prime material in the composition was the enhancement of mechanical properties. The use of these methods for the modification of cellulose led to more desirable thermal and thermooxidative stabilities. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 2353–2360, 2003     

Mechanical and thermal properties of biocomposites from poly(lactic acid) and DDGS

Distillers dried grains with solubles (DDGS), an ethanol industry coproduct, is used mainly as a low‐value feedstuff. Poly(lactic acid) (PLA) is a leading biodegradable polymer, but its applications are limited by its relatively high cost. In this study, low‐cost, high‐performance biodegradable composites were prepared through thermal compounding of DDGS and PLA with methylene diphenyl diisocyanate (MDI) as a coupling agent. Mechanical, morphological, and thermal properties of the composites were studied. The coupling mechanism of MDI in the PLA/DDGS system was confirmed via Fourier‐transform infrared spectra. The PLA/20% DDGS composite with 1% MDI showed tensile strength (77 MPa) similar to that of pure PLA, but its Young's modulus was 25% higher than that of pure PLA. With MDI, strong interfacial adhesion was established between the PLA matrix and DDGS particles, and the porosity of the composites decreased dramatically. Crystallinity of PLA in the composites was higher than that in pure PLA. Composites with MDI had higher storage moduli at room temperature than pure PLA. This novel application of DDGS for biocomposites has significantly higher economic value than its traditional use as a feedstuff. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Synthesis and properties of soy hull‐reinforced biocomposites from conjugated soybean oil

The tensile and flexural properties of new thermosetting composites made by the free radical polymerization of a conjugated soybean oil (CSO)‐based resin reinforced with soy hulls have been determined for various resin compositions. The effects of reinforcement particle size and filler/resin ratio have been assessed. The thermal stability of the new materials has been determined by thermogravimetric analysis and the wt % of oil incorporation has been calculated after Soxhlet extraction (the extracts have been identified by ¹H‐NMR spectroscopy). The resin consists initially of 50 wt % CSO and varying amounts of divinylbenzene (DVB; 5–15 wt %), dicyclopentadiene (DCPD; 0–10 wt %), and n‐butyl methacrylate (BMA; 25–35 wt %). Two soy hull particle sizes have been tested (<177 and <425 μm) and two different filler/resin ratios have been compared (50 : 50 and 60 : 40). An appropriate cure sequence has been established by differential scanning calorimetry (DSC) analysis. The results show a decrease in the properties whenever DVB or BMA is substituted by DCPD. Also, larger particle sizes and higher filler/resin ratios are found to have a negative effect on the tensile properties of the new materials. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Graphene sulphonic acid/chitosan nano biocomposites with tunable mechanical and conductivity properties

Nanocomposites of chitosan are produced using graphene sulphonic acid (SG) at five different compositions and are designated as SG0.5, SG0.75, SG1, SG3 and SG5; the numbers indicate weight percent of SG. The TEM & AFM micrographs indicate that the SG sheets are in exfoliated state. The thermal stability and the storage modulus of the composites increase with increasing SG concentration showing a maximum increase (202%) for SG5 sample. The stresses at break and Young’s modulus have increased with increasing SG content. SG5 shows the highest increase of both tensile strength and Young’s modulus of 290 ± 7% and 200 ± 7%, respectively. Analysis of the Young’s modulus data suggests that SG sheets are randomly distributed and at ≥1 wt% concentration they are unidirectionally oriented parallel to the film. The system exhibits percolation threshold of 0.49 wt% SG and it attains maximum conductivity of 0.13 S m^?1 at 1.6 wt% SG.     

Biodegradability and mechanical properties of agro‐flour–filled polybutylene succinate biocomposites

The objective of this study was the production of rice husk flour (RHF) and wood flour (WF) filled polybutylene succinate (PBS) biocomposites as alternatives to cellulosic material filled conventional plastic (polyolefins) composites. PBS is one of the biodegradable polymers, made from the condensation reaction of 1,4‐butanediol and succinic acid that can be naturally degraded in the natural environment. We compared the mechanical properties between conventional plastics and agro‐flour–filled PBS biocomposites. We evaluated the biodegradability and mechanical properties of agro‐flour–filled PBS biocomposites according to the content and filler particle size of agro‐flour. As the agro‐flour loading was increased, the tensile and impact strength of the biocomposites decreased. As the filler particle size decreased, the tensile strength of the biocomposites increased but the impact strength decreased. The addition of agro‐flour to PBS produced a more rapid decrease in the tensile strength, notched Izod impact strength, and percentage weight loss of the biocomposites during the natural soil burial test. These results support the application of biocomposites as environmentally friendly materials. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 1513–1521, 2005     

Spark plasma sintering to restrict sintering reactions and enhance properties of hydroxyapatite–mullite biocomposites

Herein, we demonstrate how spark plasma sintering (SPS) can be useful in restricting the sintering reactions and faster densification in Hydroxyapatite–Mullite system, which otherwise shows extensive sintering reactions during conventional pressureless sintering, as reported in a recent study [Nath et al. J. Am. Ceram. Soc. 93 (2010) 1639–1649]. The microstructure of SPSed Hydroxyapatite (HAp)-20 wt% mullite composites was characterized by submicron sized HAp and equiaxed mullite grains. Another important result has been the achievement of higher hardness of 7 GPa, which is much higher than pressureless sintered composites. The cell culture study including cellular viability using MTT analysis establishes good cytocompatibility of SPSed composites.     

Effective mechanical properties of polyvinylalcohol biocomposites with reinforcement of date palm leaf fibers

Polyvinylalcohol/date palm leaf fiber (PVA/DPL) biocomposites were prepared by the melt mixing fabrication technique with various proportions of fibers. DPL fibers were chemically modified with the purpose of improving the dispersion and better compatibility with PVA matrix. Different chemical processes of modification were adopted and the tensile strengths of both treated and untreated fibers were compared. It was noticed that the tensile strength of acrylic acid treated fiber was optimum in comparison to other methods. The interaction of DPL fibers with PVA matrix were studied by Fourier transforms infrared spectroscopy (FTIR). Field emission scanning electron microscope (FESEM) was used to study the morphology of biocomposites. The tensile strength, Young's modulus, elongation at break, flexural strength, and impact strength of PVA/DPL biocomposites were investigated and compared with that of virgin PVA matrix. It was found that the above properties were first increased with fiber loading and then decreased. The optimum properties were obtained at 28 wt% of DPL fiber. The storage modulus and tan delta values of PVA/DPL biocomposites were analyzed. The thermal properties of biocomposites were also studied through the results of thermogravimetric (TGA). POLYM. COMPOS., 34:959–966, 2013. © 2013 Society of Plastics Engineers     

Preparation and morphological,thermal, and physicomechanical properties of polypropylene‐potato peel biocomposites

Potato peel powder (POPL), which is biodegradable, has been used as filler material in polypropylene (PP) matrix in varying concentration from 10 to 40% by weight to prepare biocomposites and investigated water absorption, physicomechanical and thermal properties. Scanning electron microscopy and X‐ray diffraction has been used for morphological characterization and crystallization studies. Flexural modulus of biocomposites increased by 40% compared with neat PP at 30% loading of POPL. Flexural strength also increased with increasing filler loading. Tensile strength of biocomposites has been observed to be comparable with neat PP up to 20% filler loading and increase in tensile modulus up to 40% was seen in biocomposites with 20% filler loading. Impact strength of biocomposites up to 20% filler loading was found to be at par with neat PP. Use of MA‐g‐PP compatibilizer in the biocomposites yielded better physico‐mechanical and thermal properties than biocomposites without compatibilizer. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42445.     

Cardanol biocomposites reinforced with jute fiber: Microstructure,biodegradability, and mechanical properties

This work aims at studying the preparation and characterization of composites of phenolic resin (matrix) based on cashew nut shell liquid, reinforced by natural jute fibers. The fibers were chemically modified using alkaline treatment with solutions of NaOH (5 and 10%) and bleached with sodium hypochlorite NaClO/H₂0 (1:1) at 60–75°C. The microstructure was investigated by Scanning Electron Microscopy to observe the fiber surface after the treatment. As a result, there was an improvement in the thermal stability of the fiber, which was verified by Thermogravimetric Analysis. The jute fiber composites showed an improvement in their mechanical properties due to chemical treatment with 5% NaOH. Their biodegradability level depended on the employed alkali solution concentration. This study is important to evaluate the application of the fibers as renewable materials. POLYM. COMPOS., 31:1928–1937, 2010. © 2010 Society of Plastics Engineers.     

Processing and physical properties of Al2O3/aluminum alloy composites

Porous aluminum oxide (Al₂O₃) preforms were formed by sintering in air at 1200 °C for 2 h. A356, 6061, and 1050 aluminum alloys were infiltrated into the preforms by squeeze casting in order to fabricate Al₂O₃/A356, Al₂O₃/6061, and Al₂O₃/1050 composites, respectively, with different volumes of aluminum alloy content. The content of aluminum alloy in the composites was 10–40% by volume. The resistivity of Al₂O₃/A356, Al₂O₃/6061, and Al₂O₃/1050 composites decreased dramatically from 6.41 × 10¹² to 9.77 × 10⁻⁴, 7.28 × 10⁻⁴, and 6.24 × 10⁻⁴ Ω m, respectively, the four-points bending strength increased from 397 to 443, 435.1, 407.2 MPa, respectively, and the deviations were smaller than 2%. From SEM microstructural analysis and TEM bright field images, the pore volume fraction and the relative density of the composites were the most important factors that affected the physical and mechanical properties. The ceramic phase and alloy phase in Al₂O₃/aluminum alloy composites were found to be homogenized and uniformly distributed using electrical and mechanical properties analysis, microstructure analysis, and image analysis.