Synthesis,properties, and biodegradability of three-branched copolyamide (4/6)

Previous studies on polyamide 4, excellent properties, functionalities, and biodegradation in natural condition have been shown. In this study, three-branched (star-shaped) copolyamides constituted of polyamide 4 and polyamide 6 constitutional unit were synthesized by anionic ring-opening copolymerization of 2-pyrrolidone with ε-caprolactam. The thermal and mechanical properties and the biodegradability of the obtained copolyamides have been systematically investigated. The weight-average molecular weight of the copolyamides was as high as tens of thousands (M_w 10–80 × 10³ g/mol). The composition of the copolyamides was approximately in accord with the monomer feed ratio, thereby being controllable. The thermal and mechanical properties changed readily as the composition was varied (T_m 146–266°C, ΔH_m 10–70 J/g, T_d 278–369°C, tensile strength 28–64 MPa, elongation at break 80–750%). The copolyamide having 2-pyrrolidone unit of 96–51 mol% exhibited biodegradability by an activated sludge. The biodegradation of the copolyamide proceeded uniformly without disproportion in constitutional unit.     

Factorial optimization of the effects of melt‐spinning conditions on biodegradable as‐spun aliphatic–aromatic copolyester fibers. III. Diameter,tensile properties,and thermal shrinkage

To model the melt‐spinning process of biodegradable as‐spun linear aliphatic–aromatic copolyester fibers, a fraction factorial experimental design and appropriate statistical analysis for the 32 screening trials involving five control parameters were used. Because of their central role in the production processes and end use textiles, it is important to simulate the mechanical and thermal shrinkage properties of AAC fibers. Concise statistical models of fiber behavior are based on factorial experimental design data. Process's data are collected, analyzed, and mathematical models created to predict the diameter, tenacity, elongation at break, modulus, and thermal shrinkage of the spun fiber in terms of random variables and their associated probability distributions. The theoretical regression models obtained form the main source code in the enhanced forecasting program, which presents the melt‐spinning process of aromatic–aliphatic copolyester fibers. Factorial statistical approaches, based on over indicated region levels of melt‐spinning process parameters, are given in terms of assumptions and theory to produce biodegradable, environmentally friendly fibers for different applications. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Mechanical properties and biodegradability of green composites based on biodegradable polyesters and lyocell fabric

Green composites composed of regenerated cellulose (lyocell) fabric and biodegradable polyesters [poly(3‐hydroxybutyrate‐co‐3‐hydroxyvarelate) (PHBV), poly(butylene succinate) (PBS), and poly(lactic acid) (PLA)] were prepared by compression‐molding method. The tensile moduli and strength of all the biodegradable polyester/lyocell composites increased with increasing fiber content. When the obtained PLA/lyocell composites were annealed at 100°C for 3 h, the tensile strength and moduli were lowered despite the increase of degree of crystallization of the PLA component. The SEM observation of the composites revealed that the surface of the annealed composite has many cracks caused by the shrinkage of the PLA adhered to lyocell fabric. Multilayered PLA/lyocell laminate composites showed considerably higher Izod impact strength than PLA. As a result of the soil viral test, although the order of higher weight loss for the single substance was lyocell > PHBV > PBS > PLA, the biodegradability of the green composites did not reflect the order of a single substance because of the structural defect of the composite. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 3857–3863, 2004     

Synthesis,characterization, and properties of biodegradable poly(butylene succinate) modified with imide dihydric alcohol

A series of high molecular weight poly (butylene succinate) and its copolyester containing rigid imide units were synthesized in this article. The chemical structure and composition of the copolyesters were determined by ¹H NMR spectroscopy and Fourier transform infrared spectroscope (FT‐IR). The thermal properties, crystallization behavior and mechanical properties of polymers were investigated using differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), wide‐angle X‐ray diffraction (WAXD) and mechanical testing. The enzymatic degradation was investigated using pancreatic lipase solution. The results showed that the melting temperature (T_m) of the copolyester decreased with the increment in pyromellitic imide unit content. However, the thermal degradation temperature (5% decomposition temperature) changed little. Meanwhile, the enzymatic degradation rate of poly (butylene succinate) was enhanced. The mechanical properties showed that the tensile strength had a trend of decrease, but the elongation at break was improved with the increment in imide units. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40807.     

Radiation degradation and stability of PBAT: copolymer of aromatic and aliphatic esters

Effect of the exposure of poly(butylene adipate‐co‐terephthalate) (PBAT) to ionizing radiation was studied by means of EPR and diffuse reflection spectroscopy, GC, and gel permeation chromatography. In addition, the influence of radiation‐induced processes on mechanical and rheological properties for the doses in the range 0–200 kGy was investigated. The macroscopic consequences of PBAT irradiation included: crosslinking, chain cleavage, and oxidation, which led to the significant modification of physicochemical features. The crosslinking process occurred even under cryogenic conditions and was confirmed by reduction in melt flow index (MFI), increase in viscosity, and weight‐average molecular weight with increasing dose. Material degradation during long‐term storage was accompanied by deterioration of mechanical properties, increase in MFI, and viscosity reduction. Oxidation of the copolyester had a chain character and increased over time, especially in the case of irradiated PBAT. Despite the presence of aromatic rings dissipating energy, the material is susceptible to ionizing radiation. The regions containing terephthalates are involved in the aging processes; the appropriate mechanisms have been proposed. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46682.     

Enhanced mechanical and thermal properties of biodegradable poly(butylene succinate‐co‐adipate)/graphene oxide nanocomposites via in situ polymerization

Poly(butylene succinate‐co‐butylene adipate) (PBSA)/graphene oxide (GO) nanocomposites were synthesized via in situ polymerization for the first time. Atomic force microscopy demonstrated the achievement of a single layer of GO, and transmission electron microscopy proved the homogeneous distribution of GO in the PBSA matrix. Fourier transform infrared spectroscopy results showed the successful grafting of PBSA chains onto GO. With the incorporation of 1 wt % GO, the tensile strength and flexural modulus of the PBSA were enhanced by 50 and 27%, respectively. The thermal properties characterized by differential scanning calorimetry and thermogravimetric analysis showed increases in the melting temperatures, crystallization temperatures, and thermal stability. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 4075–4080, 2013     

Mechanical and biodegradation properties of bamboo fiber-reinforced starch/polypropylene biodegradable composites

Bamboo fiber (BF)-reinforced starch/polypropylene (PP) composites were prepared by extrusion and injection molding methods. The mechanical and thermal properties and water absorption were evaluated by different methods. Moreover, composite samples were subjected to biodegradation through soil burial test and microbes medium degradation. Different stages of biodegradation were investigated by weight loss, attenuated total reflection Fourier transformed infrared spectroscopy, differential scanning calorimeter, and scanning electron microscope. It was found that contents of BF and starch resin had a significant influence on the properties of the composites. With more content of BF, the composite exhibited a better flexural property and biodegradation. A distinct decrease of weight loss and mechanical properties indicated the degradation caused by the microbes. After biodegradation, thermal stability of the composites decreased while the crystallinity of PP increased. The results prove that the composites more easily tend to be degraded and assimilated by microbes. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 137, 48694.     

Effects of spinning speed and heat treatment on the mechanical properties and biodegradability of poly(lactic acid) fibers

We undertook this study to suggest the optimal spinning process conditions that provide a proper range of tenacity and biodegradability in textile fibers. The effect of melt‐spinning speed and heat treatment on the mechanical properties and biodegradability of poly(lactic acid) (PLA) fibers were investigated. PLA was spun at a high spinning speed of 2000–4000 m/min, and each specimen was heat‐treated. Mechanical properties were estimated by measurement of the breaking stress, and the degree of crystallinity was evaluated with wide‐angle X‐ray scattering. Biodegradability was estimated from the decreases in breaking stress, weight loss, and degree of crystallinity after soil burial. The results of the experiment reveal that heat treatment of the PLA fibers increased the breaking stress and crystallinity. With increasing spinning speed, breaking stress and crystallinity also increased. An increase in spinning speed was more effective than an increase in heat treatment for enhancing the breaking stress within the range of this study. From the soil burial test, it was revealed that an increase in spinning speed and heat treatment decreased the biodegradability of the fibers. X‐ray analysis of the soil‐buried fibers showed that fibers with higher crystallinities began to degrade more slowly. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 3099–3104, 2007     

Mechanical and thermal flow properties of wood flour–biodegradable polymer composites

Wood flour (WF)–polycaprolactone (PCL) and polybutylenesuccinate–butylenecarbonate (PBSC) composites were prepared by knead processing. The effects of a compatibilizer on the tensile and thermal flow properties of the composites were investigated. PCL‐graft‐maleic anhydride (PCL‐g‐MA) was used as a compatibilizer. Tensile properties were improved by adding PCL‐g‐MA to both composites. The tensile strength and Young's modulus were increased from 13 to 27 MPa and 581 to 1011 MPa in WF–PCL (50/50, w/w) composites, respectively, and from 17 to 28 MPa and 814 to 1007 Mpa in WF–PBSC (50/50, w/w) composites, respectively, with the addition of 5% PCL‐g‐MA. Elongation at break increased from 4 to 7% and from 3 to 6% in the WF–PCL and the WF–PBSC composites, respectively. Tensile strength was further increased with increasing WF content in the presence of PCL‐g‐MA. Thermal flow temperature and melt viscosity of the composites were increased, and water absorption and thickness swelling were improved with the addition of PCL‐g‐MA. It was found from the burial test that all composites were more than 40% degraded within 6 weeks, and there was no considerable difference in degradation between composites with PCL‐g‐MA and those without. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 1900–1905, 2003     

Effect on thermal,mechanical, and biodegradable properties of plasma-treated fish scale powder/linear low-density polyethylene polymer composite films

In the present work, we report the effect of low-temperature plasma treatment on thermal, mechanical, and biodegradable properties of polymer composite blown films prepared from carp fish scale powder (CFSP) and linear low-density polyethylene (LLDPE). The CFSP was melt compounded with LLDPE using a filament extruder to prepare 1, 2, and 3 wt.% of CFSP in LLDPE polymer composite filaments. These filaments were further pelletized and extruded into blown films. The blown films extruded with 1, 2, and 3 wt.% of CFSP in LLDPE were tested for thermal and mechanical properties. It was observed that the tensile strength decreased with the increased loading content of CFSP, and 1% CFSP/LLDPE exhibited the highest tensile strength. To study the effect of low-temperature plasma treatment, 1% CFSP/LLDP polymer composite with high tensile strength was plasma treated with O₂ and SF₆ gas before blow film extrusion. The 1% CFSP/LLDPE/SF₆-extruded blown films showed increased thermal decomposition, crystallinity, tensile strength, and modulus. This may be due to the effect of crosslinking by the plasma treatment. The maximum thermal decomposition rate, crystallinity %, tensile strength, and modulus obtained for 1% CFSP/LLDPE/SF₆ film were 500.02°C, 35.79, 6.32 MPa, and 0.023 GPa, respectively. Furthermore, the biodegradability study on CFSP/LLDPE films buried in natural soil for 90 days was analyzed using x-ray fluorescence. The study showed an increase in phosphorus and calcium mass percent in the soil. This is due to the decomposition of the hydroxyapatite present in the CFSP/LLDPE biocomposite.     

Ethynyl aromatic siliconhybridized resin: Synthesis,characterizations, and thermal properties

A novel silicon‐containing resin (ESA resin) was successfully synthesized by the condensation reaction of lithium arylacetylide with chlorosilane in high yields. The resin was characterized by the techniques of FTIR, ¹H‐NMR, ²⁹Si‐NMR, and gel permeation chromatography. Thermal cure process was monitored by DSC and FTIR methods. This resin could melt at around 100°C and thermally cured at 200–250°C with low exothermal enthalpy. Owing to the high aryl groups containing and the complete crosslinking of ethynyl groups, the cured ESA resin exhibited excellent thermal stability and high char yield. The decomposition temperature $T_{d_5}$ of the cured resin was at 510°C, and the residue yield at 900°C was 82.9% in N₂. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Effect of different compatibilizers on the mechanical and thermal properties of starch/polypropylene blends

Starch was treated with three kinds of compatibilizers (coupling agents or modifying agents), KH‐550, KH‐570, and glycerin monostearate. Blends of polypropylene (PP) and treated starch were prepared by a twin‐screw extruder. The effects of the starch before and after treatments and the kinds and contents of the compatibilizers on the mechanical and thermal properties of the PP/starch blends were investigated in this study. We found that the mechanical properties (tensile strength, impact strength, and elongation at break) of the blends were obviously improved with increasing content of different kinds of compatibilizers. Meanwhile, the most significant improvement in the mechanical properties was obtained in the samples containing just a 1 wt % loading of compatibilizers, and KH‐570 had the best improved effects among the different kinds of compatibilizers. The results of thermogravimetric analysis demonstrate that to some extent, the thermal stability of the PP/starch blends was improved after the addition of compatibilizers. Scanning electron microscopy showed that the dispersion of starch in the PP matrix and adhesion between the starch and PP matrix were obviously improved after the addition of compatibilizers. KH‐570 not only had the best improved effects among the coupling agents but also still acted as a similar plasticizer. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43332.     

Investigation of melting behaviors and crystallinity of linear polyamide with high‐aliphatic content

The melting behaviors and crystal structures of a long alkyl chain polyamide and nylon 18 18, were investigated under annealing and isothermal crystallization conditions. Nylon 18 18 showed multiple melting peaks in differential scanning calorimetry (DSC) thermograms depending on thermal history of the samples. The origin of the multiple melting peaks may be a result of a melting and recrystallization mechanism during DSC scans. Wide‐angle X‐ray diffraction patterns showed two new diffraction peaks, which appeared at 0.44 and 0.37 nm, and are characteristic peaks of α‐form (triclinic structure) of even–even nylons with increasing annealing temperature. The intensities of these peaks increased, and they split further apart, with elevated annealing temperatures. The solid‐state ¹⁵N CP/MAS NMR spectra of the nylon 18 18 samples that had been quenched and annealed also confirmed the α‐crystalline form. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Effect of the aggregation structure on the thermal shrinkage of polyacrylonitrile fibers during the heat-treatment process

Secondary thermal shrinkage or chemical shrinkage involved in the thermal shrinkage of polyacrylonitrile (PAN) fibers was not only associated with the cyclization degree but also the thermal mobility of molecular chains in the aggregation structures during crosslinking. In this study, the cyclization process was monitored with differential scanning calorimetry and IR spectroscopy. The evolution of aggregation structures throughout cyclization and variations in the secondary shrinkage for the PAN fibers were characterized with wide-angle X-ray diffraction and thermal mechanical analysis, respectively. The results show that with increasing temperature, the cyclization degree increased; the cyclization occurred first in amorphous regions and then extended to the crystalline regions. Correspondingly, the secondary shrinkage also increased and could be separated into two stages: those of the amorphous and crystalline phases. The shrinkage of the crystalline regions was much bigger than that of the amorphous regions. For fibers with different aggregation structures, the crystallinity affected the cyclization degree in the amorphous and crystalline regions and resulted in the difference in total shrinkage. Furthermore, because the unoriented molecular chains in both the amorphous and crystalline regions shrank more after cyclization, the shrinkage of both regions was primarily decided by the level of orientated molecular chains participating in the cyclization. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Non‐catalyst synthesis and thermal behaviors of three‐arm star aliphatic polycarbonates

Three‐arm star aliphatic polycarbonates (TMP‐PDTCs) were successfully synthesized via the ring‐opening polymerization of 2,2‐dimethyl trimethylene carbonate (DTC) initiated by trimethylolpropane (TMP) in the absence of catalysts. The structure of TMP‐PDTCs was characterized by Fourier transform infrared (FTIR) spectroscopy, nuclear magnetic resonance (NMR) spectroscopy, and gel permeation chromatography (GPC). The effects of reaction temperature, time, and the DTC/TMP molar feed ratio on the non‐catalyst polymerization were investigated. The thermal behaviors of TMP‐PDTCs were measured by differential scanning calorimetry (DSC). © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41998.     

Mechanical and thermal properties of poly(butylene succinate)/poly(3‐hydroxybutyrate‐co‐3‐hydroxyvalerate) biodegradable blends

Biodegradable polymer blends of poly(butylene succinate) (PBS) and poly(3‐hydroxybutyrate‐co‐3‐hydroxyvalerate) (PHBV) were prepared with different compositions. The mechanical properties of the blends were studied through tensile testing and dynamic mechanical thermal analysis. The dependence of the elastic modulus and strength data on the blend composition was modeled on the basis of the equivalent box model. The fitting parameters indicated complete immiscibility between PBS and PHBV and a moderate adhesion level between them. The immiscibility of the parent phases was also evidenced by scanning electron observation of the prepared blends. The thermal properties of the blends were studied through differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). The DSC results showed an enhancement of the crystallization behavior of PBS after it was blended with PHBV, whereas the thermal stability of PBS was reduced in the blends, as shown by the TGA thermograms. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42815.     

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.     

Mechanical and thermal properties of EVA blended with biodegradable ethyl cellulose

In this study, biodegradable blend of Poly (Ethylene‐co‐Vinyl Acetate) (EVA) and Ethyl Cellulose (EC) were prepared. Ethylene vinyl alcohol (EVOH) copolymer was used as an interfacial compatibilizer to enhance adhesion between EVA and EC. The melt blended compatibilized biocomposites were examined for mechanical and thermal properties as per the ASTM standards. It has been found that the EC has a reinforcing effect on EVA leading to enhanced tensile strength and also impart biodegradability. Thus, a high loading of 50% EC could be added without compromising much on the mechanical properties. Analysis of the tensile data using predictive theories showed an enhanced interaction of the dispersed phase (EC) and the matrix (EVA). The compatibilizing effects of EVOH on these blends were confirmed by the significant improvement in the mechanical properties comparable with neat EVA as also observed by SEM microscopy. The TGA thermograms exhibits two‐stage degradation and as EC content increases, the onset temperature for thermal degradation reduces. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Biodegradable Poly(butylene adipate-co-terephthalate) composites reinforced with bio-based nanochitin: Preparation,enhanced mechanical and thermal properties

The accumulation of nonbiodegradable petrochemical-based polymers in the environment motivates the development and use of low-cost, eco-friendly, and biodegradable polymers. A series of biodegradable poly(butylene adipate-co-terephthalate) composites reinforced by sustainably sourced nanochitin were successfully prepared using melt blending and compression molding methods. Structural, thermal, and mechanical characterizations of poly(butylene adipate-co-terephthalate) (PBAT)/nanochitin composites were performed. SEM revealed that the nanochitin was uniformly dispersed throughout the PBAT matrix at low contents (<2 wt %), while DSC analyses revealed a corresponding increase in the crystallinity (32.6% enhancement) of the PBAT matrix. The tensile strength and elongation at break of the PBAT/nanochitin composite containing 0.5 wt % nanochitin were higher by 82.5 and 64.2%, respectively, compared with pristine PBAT. The Chitin-0.5 composite also showed improved thermal stability compared with PBAT (the char yield improved by 8%) due to the uniform dispersion of nanochitin in the PBAT matrix. The enhanced performance of the PBAT/nanochitin composites, prepared without an added compatibilizer, informs the development of improved biodegradable PBAT-based polymers. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48485.