Chemical evaluation of composites natural rubber/carbon black/leather tannery projected to antistatic flooring

In this study the composites which are commonly called NR/CB/Leather were developed in order to apply them as antistatic flooring and coating. They were developed using vulcanized natural rubber, carbon black to add an electric conduction property and industrial leather waste. The leather industrial waste was micronized and added to the rubber matrix in proportions of 60 and 80 phr using an opened mixing cylinder according to ASTM D 3182 standard. The composites were exposed to the sanitizing agents, (i) bleach and (ii) disinfectant, aiming to simulate a real cleaning context, and to meet the health standards of the Brazilian Ministry of health. Physical‐chemical and microbiological evaluations were carried out to determine the structural and chemical stabilities of the composites. After this, low water absorption level (<1.5%), immobilization and low chromium oxide level (<1.5), pH within the neutrality rate and an excellent resistance to microbiological contamination were identified for the composites. Thus, from a physical‐chemical perspective, the composites NR/CB/Leather displayed suitable properties and potential for application as antistatic flooring and coatings. Besides using leather industrial waste in their production, their manufacture can boost this industrial sector economically and, consequently, promote a reduction in environmental impact. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43618.     

Heat-responsive shape memory Eucommia ulmoides gum composites reinforced by zinc dimethacrylate

With the renewability, functionality, and biocompatibility of Eucommia ulmoides gum (EUG), shape memory polymers fabricated from EUG present the potential application in biomedical devices and sensors. In this study, heat-responsive shape memory composites were developed and reinforced by zinc dimethacrylate (ZDMA). ZDMA particles were in situ polymerized and uniformly dispersed in the EUG, showing strong interfacial interactions with EUG. The obviously improved tensile strength and storage modulus in the elastic state are attributed to the reinforcement of poly-ZDMA particles. The switching temperature of EUG/ZDMA composites changed from 50 to 29°C through altering the dicumyl peroxide and ZDMA loading. The EUG/ZDMA composites exhibited high shape fixity of 95% and shape recovery of 90%, which favors theirs biomedical applications.     

Poly(lactic acid) biocomposites reinforced with ultrafine bamboo‐char: Morphology,mechanical, thermal,and water absorption properties

In this study, ultrafine bamboo‐char (BC) was introduced into poly(lactic acid) (PLA) matrix to improve mechanical and thermal properties of PLA based biodegradable composites. PLA/BC biocomposites were fabricated with different BC contents by weight. Uniform dispersion of BC in the PLA matrix and good interaction via physical and chemical interfacial interlocks were achieved. The maximum tensile strength and tensile modulus values of 14.03 MPa and 557.74 MPa were obtained when 30% BC was used. Impact strength of the biocomposite with 30% BC was increased by 160%, compared to that of pure PLA. DSC analysis illustrated that PLA/BC biocomposites had a better thermal property. Crystallization temperature decreased and maximal crystallinity of 30.30% was observed with 30% BC load. We did not notice significant thermal degradation differences between biocomposites with different BC loadings from TGA. Better water resistance was obtained with the addition of BC. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43425.     

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.     

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.     

Morphology,mechanical, and physical properties of wet-spun cellulose acetate fiber in different solvent-coagulant systems and in-situ crosslinked environment

Wet spinning is a popular fiber manufacturing process where the effects of solvent and coagulant on the wet-spun fiber are significant. In this study, we have explored the effect of solvent-coagulant interaction and in-situ crosslinking on the wet-spun cellulose acetate (CA) fiber. Investigation on 12 different solvent-coagulant systems revealed that variation in the systems resulted in significant variance in morphology and mechanical property of the fiber. Remarkable increase in mechanical property was observed after in-situ crosslinking with citric acid and polyethylene glycol (PEG). Inclusion of sodium hypophosphite (NaH₂PO₂) as catalyst further increased tensile modulus (~407%) and crystallinity index (~46%) compared to CA fiber crosslinked with only citric acid. It was established that fiber from CA-DMSO solution crosslinked with 10% citric acid and 10% PEG extruded in ethanol showed the highest tensile modulus (~30 MPa). This in-depth study found an appropriate combination of solvent-coagulant for forming stable CA fiber, with the addition of crosslinkers and catalyst further increasing the strength and usability of the fiber.     

Green composites of poly(3‐hydroxybutyrate) and curaua fibers: Morphology and physical,thermal, and mechanical properties

In this article, we report the morphology and thermal, mechanical and physical properties of poly(3‐hydroxybutyrate) (PHB)/curaua composites containing triethyl citrate (TEC) as the plasticizer. The composites were prepared by mechanical mixing using pristine and chemically treated fibers (10 wt %) and TEC (30 wt %) and characterized by differential scanning calorimetry, dynamic mechanical analysis, X‐ray diffraction, small angle X‐ray scattering, polarized optical microscopy, scanning electron microscopy, tensile tests, impact resistance test, thermodilatometry, and thermal conductivity measurements. The curaua fibers acted as nucleating agent and strongly influenced the morphology of the crystalline phase of PHB, increasing the lamella thickness, decreasing the crystal size and inducing spherulite–axialite transition. These characteristics of the PHB crystalline phase determined all the properties of the composites. The tensile properties of the composites were comparable with those of neat PHB, while the impact resistance of composites was comparable with that of plasticized PHB. The higher heat capacity and thermal expansion coefficient and the lower thermal conductivity of the composites compared with neat PHB reflect the morphological changes in the PHB crystalline phase. The strategy of developing a green polymeric material from ecofriendly components exhibiting a good balance of properties by combining curaua fibers, TEC, and PHB was successful. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44676.     

Fabrication and characterization of sucrose palmitate reinforced poly(lactic acid) bionanocomposite films

Environmental issues concerning petroleum‐based polymers have begun a growing emphasis to utilize sustainable poly(lactic acid) (PLA) based packaging. However, PLA has its own limitations such as brittleness, high gas permeabilities and slow crystallization rate. With the aim to alleviate these limitations, we made a maiden effort to use a food additive, sucrose palmitate (SP) as eco‐friendly filler for fabrication of PLA based bionanocomposites. FTIR analysis elucidated the presence of hydrogen bonding and intermolecular interaction between PLA and reinforcement. Ordered orientation of the SP in the PLA matrix visualized by TEM analysis revealed uniform dispersion of SP filler into PLA matrix. DSC and XRD results confirmed that the incorporated bio‐filler acted as a nucleating agent and thus partially contributed towards the crystallinity of PLA‐SP bionanocomposites. Enhancement in the tensile strength and elongation at break up to 83 and 56% respectively is obtained. The best positive influence for the oxygen barrier was confirmed for the PLA‐SP bionanocomposite film where the reduction in oxygen permeability by 69% is achieved in comparison to pure PLA. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41320.     

The mechanical properties of β‐Si3N4 whiskers‐reinforced dental resin composites

The surface‐modified β‐Si₃N₄ whiskers were used as inorganic fillers to reinforce dental resin (Bis‐GMA/TEGDMA) matrix with filler level ranging from 0 to 60 wt %. The experimental results indicated that the fracture strength of the composites increased from 79.85 to 139.8 MPa with increasing the whiskers loading. The compressive strength, elastic modulus, and rockwell hardness all increased monotonously with increasing filler level. Furthermore, thermal cycling did not decrease the fracture strength of the composites. Moreover, the composites showed good biocompatibility to support MG63 cells adhesion and proliferation. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40692.     

Borassus powder-reinforced poly(lactic acid) composites with improved crystallization and mechanical properties

This article reports on the development of biocomposites based on polylactic acid (PLA) and borassus powder. Borassus powder was treated with alkali to remove hemicelluloses and lignin. The treated borassus improved the homogeneous mixing with PLA and increased the crystallinity of PLA. Dispersibility of the borassus was studied by scanning electron microscopy (SEM) and X-ray MicroCT. PLA/borassus composites were prepared by melt mixing of PLA with 5, 10, and 15 wt % treated/untreated borassus. Composites were examined for mechanical properties and crystallization. Composites showed enhanced tensile strength compared to neat PLA. The PLA/treated borassus powder composites displayed higher crystallinity than PLA. The isothermal cold crystallization study showed increase in the crystallization rate of PLA in the presence of treated borassus. The spherulitic growth was studied using polarized optical microscopy. The enhanced performance of the PLA-borassus composites was observed in the presence of borassus. This study demonstrates that the PLA-borassus composites show great promise for bioplastics applications. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47440.     

Processing and thermal properties of composites based on recycled PET,sisal fibers,and renewable plasticizers

This investigation focuses on the preparation of bio‐based composites from recycled poly (ethylene terephthalate) (PET) and sisal fibers (3 cm, 15 wt %), via thermopressing process. Plasticizers derived from renewable raw materials are used, namely, glycerol, tributyl citrate (TBC) and castor oil (CO), to decrease the melting point of the recycled PET (T_m ∼ 265°C), which is sufficiently high to initiate the thermal decomposition of the lignocellulosic fiber. All used materials are characterized by thermogravimetric analysis and differential scanning calorimetry, and the composites are also characterized via dynamic mechanical thermal analysis. The storage modulus (30°C) and the tan δ peak values of CT [PET/sisal/TBC] indicate that TBC also acts as a compatibilizing agent at the interface fiber/PET, as well as a plasticizer. To compare different processing methods, rheometry/thermopressing and compression molding are used to prepare the recycled PET/sisal/glycerol/CO composites. These two different methods of processing show no significant influence on the thermal properties of these composites. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40386.     

Mechanical,thermal, and barrier properties of nanocomposites based on poly(butylene succinate)/thermoplastic starch blends containing different types of clay

Nanocomposites based on blends of poly(butylene succinate) (PBS) and thermoplastic cassava starch (TPS) were prepared using a two‐roll mill and compression molding, respectively. Two different types of clay, namely sodium montmorillonite (CloisiteNa) and the organo‐modified MMT (Cloisite30B) were used. The morphological and mechanical properties of the nanocomposite materials were determined by using XRD technique and a tensile test, respectively. Thermal properties of the composite were also examined by dynamic mechanical thermal analysis and thermal gravimetric techniques. Barrier properties of the nanocomposites were determined using oxygen transmission rate (OTR) and water vapor transmission rate (WVTR) tests. From the results, it was found that by adding 5 pph of the clay, the tensile modulus and the thermal properties of the blend containing high TPS (75 wt %) changed significantly. The effects were also dependent on the type of clay used. The use of Cloisite30B led to a nanocomposite with a higher tensile modulus value, whereas the use of CloisiteNa slightly enhanced the thermal stability of the material. OTR and WVTR values of the blend composites containing high PBS ratio (75 wt %) also decreased when compared to those of the neat PBS/TPS blend. XRD patterns of the nanocomposites suggested some intercalation and exfoliation of the clays in the polymer matrix. The above effects are discussed in the light of different interaction between clays and the polymers. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 1114‐1123, 2013     

Aging behavior and mechanism of bio‐based engineering polyester elastomer nanocomposites

Bio‐based elastomers used in industry have attracted much attention. We prepared bio‐based engineering polyester elastomer (BEE) nanocomposites by mixing bio‐based engineering polyester elastomers with carbon (CB). The CB/BEE nanocomposites were exposed to an artificial weathering environment for different time periods. Both its aging behavior changes and aging mechanism were investigated in this article. The tensile strength retention rates were each above 90% after aging at 100°C and 125°C for 72 h. CB/BEE nanocomposites exhibited good anti‐aging properties. Furthermore, the chemical changes were detected by Fourier transform infrared spectroscopy and differential scanning calorimetry. The crosslink density changes during aging of BEE were determined as well. A plausible aging mechanism of BEE was proposed. It can be concluded that the thermal oxidation process gives priority to further crosslinking in the initial period of aging. As the aging time increases, chain scission becomes the dominant element in the subsequent thermal oxidation process. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40862.     

Estimation of the biobased carbon content of polypropylene resin in composites on the basis of the carbon 14 concentration

The aim of this study was to estimate a procedure for the biobased carbon content of polypropylene (PP) resin isolated from composites containing additives or fillers on the basis of the carbon 14 concentration ratio, as measured by accelerated mass spectrometry (AMS). To reliably estimate the biobased carbon content of plastics, additives and fillers in the composites had to be removed because they often contain significant amounts of biobased carbon. To obtain specimens with purity suitable for estimation, an isolation procedure for PP from the composites was devised. The dissolution of the composites in 1,2,3,4‐tetrahydronaphthalene at 150°C, followed by immediate centrifugation of the hot solution, yielded PP as semicrystalline precipitates by allowing the hot solution to cool during centrifugation. The recovery of the resin through the scooping off of the precipitates was typically 90%. This simple procedure provided a suitable specimen for the estimation of biobased carbon content by AMS on the basis of ASTM D 6866. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2014 , 131, 39978.     

Studies on chain extension of a novel bio‐based engineering elastomer using 4,4‐diphenyl methane diisocyanate as a chain extender

A novel hydroxyl‐terminated bio‐based engineering elastomer (BEE) was synthesized from four bio‐based monomers by adding excess diol. Then the BEE was chain extended in Haake torque rheometer with 4,4‐diphenyl methane diisocyanate (MDI) as chain extender. The molar ratio of NCO/OH, reaction temperature and reaction time of the chain‐extension reaction were studied, and the optimum condition was determined by the gel permeation chromatography (GPC), soxhlet extraction, and fourier transform infrared spectroscopy (FTIR) results. After chain extension, (i) the number‐average molecular weight of BEE became about 3.5 times of the original BEE, (ii) the thermal stability was improved and the crystallization rate was lower, (iii) and the mechanical properties were significantly improved with nano‐SiO₂ as reinforcing filler. The chain‐extended BEE would have potential wide applications in engineering field. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40756.     

Synthesis of a novel organosoluble,biocompatible, and antibacterial chitosan derivative for biomedical applications

Electrospun materials have a number of applications in the tissue engineering field. However, the limited solubility of chitosan (CS), especially in organic solvents, makes its electrospinning with other synthetic organosoluble polymers impossible. In this article, we report the synthesis of a novel organosoluble derivative of CS through the application of a simple synthetic methodology. CS was reacted with 1,3‐diethyl‐2‐thiobarbituric acid (DETBA) with triethylorthoformate in the presence of methanol and acetic acid (4:1). The functional groups in the synthesized materials were confirmed by Fourier transform infrared and solid‐state NMR spectroscopy, whereas X‐ray diffraction revealed the level of crystallinity. The CS derivative (CS–DETBA) was tested for its cytotoxic effects on human gastric adenocarcinoma AGS cells and was found to be nontoxic. The prepared derivative showed a much enhanced inhibitory effect on the growth of three bacterial strains, Escherichia coli, Pseudomonas aeruginosa, and Staphylococcus aureus, over that of CS itself. Overall, CS–DETBA showed good solubility in a range of organic solvents, such as dimethyl sulfoxide and N,N‐dimethylformamide, and was blended with polycaprolactone (PCL) to form films and electrospun nanofibers. The morphologies of the synthesized materials were analyzed by field emission scanning electron microscopy, and the fiber diameter was 360 nm under optimum conditions. This study demonstrated that the CS–DETBA–PCL blend could be a potential material for tissue engineering and biomedical applications. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 45905.     

Effect of the molecular weight on the plasticization properties of poly(hexane succinate) in poly(vinyl chloride) blends

Blends of poly(vinyl chloride) (PVC) and poly(hexane succinate) (PHS) with various molecular weights were analyzed with respect to their mechanical properties, durability, and thermal stability. We found that the molecular weight of PHS played an important role in the plasticizing process, and the single glass-transition temperature (T _g) of the PVC blends measured by dynamic mechanical analysis supported the complete miscibility between PHS and PVC. The plasticizing efficiency of PHS increased as the molecular weight increased; this reflected the gradually increasing elongation at break and the decreased T _g of the PVC blend. Meanwhile, the higher molecular weight of PHS also improved the resistance of migration and thermal stability but decreased the biodegradability of the PVC blends; this was due to the strong intermolecular interactions between PHS and PVC. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47081.     

On the use of ball milling to develop PHBV–graphene nanocomposites (I)—Morphology,thermal properties,and thermal stability

In the first part of this work, novel nanocomposites based on poly (3‐hydroxybutyrate co‐3‐hydroxyvalerate) (PHBV) and functionalized graphene nanosheets (FGS) were prepared through ball milling. As revealed by morphological characterization, this blending methodology was able to allow proper nanofiller dispersion and distribution into the matrix. Thermal properties were studied under non‐isothermal and isothermal conditions and the addition of FGS into PHBV matrix, although no changes in crystallization mechanism were observed, it modified the crystallization kinetics leading to increased crystallinity. Thermal stability analysis revealed that FGS affected the mechanism of oxidative thermal degradation and had no effect on thermal degradation by pyrolysis. Furthermore, an analysis of isothermal degradation kinetics showed that FGS speeded up the degradation rate. The Sestak‐Berggren model was used as a model to explain the isothermal degradation behavior of the obtained materials in good agreement with the experimental data. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42101.     

Synthesis and characterization of novel natural rubber based cationic waterborne polyurethane—Effect of emulsifier and diol class chain extender

Novel cationic waterborne polyurethanes (cWPU) were synthesized by step‐growth polymerization of hydroxyl telechelic natural rubber, molecular weight of 2800 g mol^?1, toluene‐2,4‐diisocyanate, N‐methyl diethanolamine (NMDEA) as an emulsifier. The chemical structure of cWPU was confirmed by ¹H‐nuclear magnetic resonance and Fourier transform infrared spectroscopy. The amounts of NMDEA and ethylene glycol under isocyanate (NCO) index of 100 on the properties of cWPU were studied. It was found that cWPU was stable under the concentration of NMDEA more than 1.50 mol and the particle sizes decreased with increasing of NMDEA content. Also, contact angle shows more hydrophilic materials by increasing of NMDEA. Extended cWPU was found in two ranges of nano size. Chain extender has strongly affected cWPU film formation, increasing of mechanical properties, and thermal properties. In addition, stress–strain curve and scanning electron microscopy image shows the change of behavior from soft elastic to ductile plastic by adding ethylene glycol. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 45715.     

Improvement of water barrier properties of soybean protein isolate films by poly(3-hydroxybutyrate) thin coating

The aim of this work was to study the preparation of bilayer films formed by soy protein isolate (SPI) and polyhydroxybutyrate (PHB). This was done using the lowest possible concentration of PHB to improve the functionality of SPI films as food packaging or for agricultural uses, specially reducing their water vapor permeability (WVP). SPI films are environmentally friendly since they are biodegradable and come from renewable sources but they are brittle and have high water permeability. Even for the lowest concentration analyzed, PHB managed to form a homogeneous layer that successfully covered up the SPI film surface. All bilayers films showed a significant reduction of WVP of SPI films, and those with the highest PHB content showed the highest elastic Young's modulus and mechanical strength while maintaining a good elongation and low T_g value, similar to that of SPI. Despite of their hydrophobicity differences, a good adherence of both layers was achieved, which allowed to improve the mechanical and barrier properties of the SPI coated films with respect to films formed by both biopolymers separately. The combination of both SPI and PHB seems to be a good alternative to prepare a biodegradable material taking advantages of the best properties of each component.