Development of phase morphology in immiscible poly(styrene‐co‐acrylonitrile)/poly(butylene terephthalate) nanoblends: Mechanical properties and effect of the compatibilizer

Nanoblends were obtained from poly(styrene‐co‐acrylonitrile) (SAN) as a matrix, and poly(butylene terephthalate) (PBT) was used as a nanodispersed phase. Compatibilized SAN/PBT blends were prepared by reactive extrusion, and the PBT concentrations ranged between 3 and 30 wt %. Nanoblends were obtained for up to 10 wt % PBT concentrations in the presence of the compatibilizer. With 20 and 30 wt % PBT, the extruded material presented a droplet dispersed phase. The same blends were subjected to an injection‐molding process, which provided a cocontinuous phase morphology. The influence of the concentration of the dispersed phase and the type of morphology on the mechanical behavior of tensile test, flexural test, impact test, and deflection temperature of the blends was analyzed. The results show an important reduction in the particle size of the dispersed phase, which was due to the presence of the compatibilizer. Furthermore, the type of morphology and an excess of compatibilizer exerted a stronger influence on the mechanical properties than the particle size of the dispersed phase. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45030.     

Mechanical properties of poly(ethylene terephthalate) nanofiber three‐dimensional structure prepared by CO2 laser supersonic drawing

CO₂‐laser supersonic drawing method can produce bulky fluffy poly(ethylene terephthalate) (PET) nanofibers (NFs) by only irradiating CO₂‐laser to as‐spun PET fibers in the supersonic air jet. Cylindrical PET NF three‐dimensional structure (NF‐3DS) was fabricated by compression‐molding the obtained fluffy PET NFs using the cylindrical metal mold. NF‐3DS mold was completely disordered 3DS without a laminated structure because NFs were disorderly packed in the metal mold. The porosity of NF‐3DS can be changed by varying the filling weight of NF into the metal mold, and the highest porosity was 95.4%. The shape recovery ratio after 50% uniaxial compression in the height of NF‐3DS increases as the porosity increases, and NF‐3DS with a porosity of 95.4% had a shape recovery ratio of 98.1%. NF‐3DS with a desired shape will be produced if the metal mold can be prepared. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 45763.     

Rheological and crystallization enhancement in polyphenylenesulfide and polyetheretherketone POSS nanocomposites

Polyhedral oligomeric silsesquioxane (POSS) additives have been shown to increase melt‐flow and crystallization in thermoplastics. In this study, the effect of incorporation of trisilanolphenyl‐POSS molecules in polyphenylenesulfide (PPS) and polyetheretherketone (PEEK) on rheology, crystallization kinetics, and thermal and mechanical properties was evaluated. Parallel plate rheometry revealed a reduction in the viscosity of PPS and PEEK with the addition of POSS. The magnitude and concentration dependence of rheological modification were shown to depend on the polymer structure and POSS solubility. Isothermal crystallization kinetics were analyzed using the Avrami model and it was found that the addition of POSS accelerated the crystallization rate of PPS blends with no significant effect on PEEK blends. Interestingly, no statistical difference in degradation temperature, tensile modulus, or tensile strength of PPS or PEEK blends was observed. The findings indicate the potential for improvements in melt viscosity and crystallization of high temperature thermoplastics with tailored POSS/polymer interactions. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44462.     

Development of biodegradable composites with treated and compatibilized lignocellulosic fibers

The aliphatic polyester Bionolle 3020 was combined with lignocellulosic fibers, namely, flax, hemp, and wood, to produce biodegradable composite materials. The effect of two fiber surface treatments, acetylation and propionylation, and the addition of maleic anhydride (MA)‐grafted Bionolle 3001 as a compatibilizer on the fiber/matrix interfacial adhesion was studied. The compatibilizer was synthesized through a MA grafting reaction in the presence of dicumyl peroxide as an initiator. The composites' mechanical properties, water absorption, fracture morphology (scanning electron microscopy), and biodegradation were evaluated. Both the fiber treatments and the compatibilizer incorporation significantly improved the composites' tensile strength, whereas an important reduction in the water absorption was found with the addition of treated fibers. Moreover, fiber incorporation into the matrix increased its biodegradation rate. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 4703–4710, 2006     

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.     

Crystallization and thermomechanical properties of PLA composites: Effects of additive types and heat treatment

This research work has concerned a study on thermomechanical and crystallization properties of poly(lactic acid) (PLA) composites containing three different types of additives; namely: kenaf fiber (20 pph), Cloisite30B nanoclay (5 pph), and hexagonal boron nitrile (h‐BN; 5 pph). The composites were prepared using a twin screw extruder before molding. Crystallization behaviors of the various composites were also examined using a differential scanning calorimetry. By adding the additives, tensile modulus of the polymer composites increased, whereas their tensile strength and elongation values decreased as compared to those of the neat PLA. Heat distortion temperature (HDT) values of the materials slightly increased, for about 3–5°C. However, after annealing at 100°C, HDT values of the fabricated PLA composites rapidly increased with annealing time before reaching a plateau after 10 min. The HDT values of above 120°C were achieved when 20 pph kenaf fiber was used as an additive. The above results were in a good agreement with DSC thermograms of the composites, indicating that percentage crystallinity of the materials increased on annealing and crystallization rate of the PLA/kenaf system was the highest. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Selective localization of organophilic clay Cloisite 30B in biodegradable poly(lactic acid)/poly(3-hydroxybutyrate) blends

The influence of selective localization of the nanoclay Cloisite 30B on the morphological, thermal and thermo-mechanical properties of biodegradable poly(lactic acid)/poly(hydroxybutyrate) blends was evaluated in this work. For this, different compounds were obtained by adding the filler in a single phase or mixed with the two matrices simultaneously by melting processing. The simultaneous processing leads to a better dispersion of nanoparticles on the blend and generates a more homogeneous polymer interface, but the properties do not increase in relation to those that were processed in separate steps. For the blends obtained in separated steps, the polymeric domains and, consequently, the superficial tension between phases are better controlled by a nanolayer. Thus, the results obtained in this work indicate that better control of the polymeric interfaces can generate a more significant effect on the thermal and thermo-mechanical properties of nanostructured blends than just a good dispersion of the fillers.     

Creep resistance of linear low density polyethylene/carbonaceous hybrid nanocomposites: Experiments and modeling

In the present work, the creep response of nanocomposites based on metallocene linear low density polyethylene (mLLDPE), reinforced with three types of carbonaceous nanofillers, namely carbon nanotubes (CNTs), graphene oxide (GO) platelets, and carbon nanofibers (CNFs) was experimentally studied. The effect of the nanofiller loading and the hybrid character of nanocomposites on the creep resistance of the nanocompsites was analyzed. In all cases, the creep resistance of the nanocomposites examined has been postulated. To support these results, creep has been modeled by a power creep law, while the creep- recovery modeling was achieved by a viscoelastic model. The implementation of the viscoelastic model has been made by assuming that the nanocomposite's structure can be represented by a physical network, with the dispersed nanofillers participating in the molecular rearrangements, which take place upon the imposition of stress. The time dependent constitutive equation involves a relaxation function, based on a Gaussian type distribution function, associated with the energy barriers that molecular segments need to overcome, for transitions to occur. It was found that creep-recovery strain could be accurately captured with the same set of parameters, whereas the number of required model parameters was quite lower than that in the widely known viscoelastic models.     

Overmolded polylactide/jute-mat eco-composites: A new method to enhance the properties of natural fiber biodegradable composites

Environmentally friendly, biodegradable composites were prepared via overmolding of poly(lactic acid) (PLA) onto PLA/jute-mat, named as “ecosheets,” reinforced continuous fiber composite sheets. Film stacking procedure was used to prepare ecosheets via using a hot-press. The fiber orientation was changed as −45°/+45° and 0°/0°. −45°/+45° orientation exhibited higher properties as compared to 0°/0° for ecosheets; therefore, this construction was used to produce overmolded composites (OMCs). The mechanical tests showed that flexural modulus and strength of OMCs were improved in comparison to neat PLA. The dynamic mechanical analysis exhibited that the thermomechanical resistance of PLA was enhanced for OMCs. Scanning electron microscopy investigation showed that the jute/PLA interphase needs to be improved to further increase the properties. It was concluded that one of the biggest advantages of this novel technique was the increase of mechanical properties of PLA without altering the density. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 137, 48692.     

Isothermal crystallization kinetics of poly(lactic acid)/synthetic mica nanocomposites

The isothermal crystallization kinetics of PLA/fluoromica nanocomposites was studied. Three types of synthetic mica at three concentrations (2.5, 5.0, and 7.5 wt % mica) were used and the effect of these micas on the crystallization and thermal properties of PLA was investigated by differential scanning calorimetry (DSC). The Avrami and Hoffman‐Weeks equations were used to describe the isothermal crystallization kinetics and melting behavior. Addition of these micas to the PLA matrix increased the crystallization rate, and this effect depended on the mica type and concentration. While the nonmodified Somasif ME‐100 exerted the smallest effect, the effect observed for the organically modified Somasif MPE was the most pronounced. The lower half‐time of crystallization t_1/2 was around 3 min for the PLA/Somasif MPE nanocomposites containing 7.5 wt % of filler at 90°C, which is about 16 min below that found for neat PLA. The equilibrium melting temperature ( ) of PLA were estimated for these systems, showing an increase in the composites and an increase with increasing loading, except for PLA/Somasif MPE, in which the increase of the mica content decreased about 5°C. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40322.     

Reactive compatibilization of PLA/TPU blends with a diisocyanate

This study focuses on the compatibilization of poly(lactic acid) (PLA)/thermoplastic polyurethane (TPU) blends by using 1,4 phenylene diisocyanate (PDI) for the first time, as the compatibilizer. Because of the potential interactions of diisocyanates with ? OH/? COOH, they are useful for reactive processing of PLA/TPU blends in the melt processing. To have insight on the reactively compatibilized structure of PLA/TPU blends, phase morphologies are observed by means of scanning electron microscopy. The mechanical, thermal, and rheological responses of the blends are investigated. The observations are that the brittle behavior of PLA changes to ductile with the addition of TPUs. The addition of PDI improves the tensile properties of the blends. The compatibilization action of PDI is monitored with DMA and rheological experiments. Cross‐over in the G′ and G″ curves of compatibilized blends indicates the relaxation of branches formed in the presence of PDI. The dispersed phase size of TPU decreases in PLA in the presence of PDI due to the improved compatibility. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40251.     

Flame resistant properties of LDPE/PLA blends containing halogen-free flame retardant

In this study, mixing petroleum-based low-density polyethylene (LDPE) with biodegradable poly(lactic acid) (PLA) is used as polymer matrix. Boron compounds, metal hydroxides, melamine (MLM), ammonium polyphosphate (APP), and pentaerythritol (PER) were used as reinforcement materials to improve flame resistance of polymer matrix. The composite materials were characterized by Fourier transform infrared spectroscopy, limiting oxygen index (LOI), thermogravimetric analysis, mechanical test, and scanning electron microscopy analyses. The LOI analysis showed that for samples, which included MLM, APP, and PER, the LOI values were dramatically improved. Especially, the LOI value of sample Q (LDPE80/PLA20/APP30/PER15/MLM15/ZB3) was enhanced about 95.17% compared to polymer mixing. © 2020 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48960.     

Development and characteristics of biodegradable Aloe‐gel/egg white films

The use of synthetic nonbiodegradable polymers has led to environmental damage. This has encouraged the interest to the development of new renewable and biodegradable matrices. The potential of egg white (EW) protein for the development of bioplastic materials has been published. However, the mixture of EW with Aloe‐gel (AG) for film formation has not been documented. In this study, films with different EW and AG combinations are manufactured and their properties are analyzed. In general, the AG/EW films are homogeneous, smooth, with no pores and with cumulus of protein on the surface with better extensibility, plasticity, and low tensile strength. In addition, they are yellow colored, UV‐light blocker, with high solubility (2.2 times) and high Water Vapor Permeability (4.17 times) compared with the control (EW film). The AG/EW films showed higher percentage of soluble protein and antibacterial activity than the control. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 44067.     

Isothermal melt crystallization and performance evaluation of polylactide/thermoplastic polyester blends with multi‐functional epoxy

A multi‐functional epoxy (ADR) was used to improve compatibilization of poly(lactic acid) (PLA)/ thermoplastic polyester elastomer (TPEE) blends. Influence of ADR on isothermal melt crystallization of the blends was investigated. The results show that isothermal melt crystallization rate of the samples increases with ADR loading. It can be attributed to a nucleation enhancement resulted from an increase of molecular weight and melt viscosity created by the chain extension/branched process of PLA in the presence of ADR. In addition, the maximum crystallinity of the samples shows a decrease with increasing ADR loading because of the chain extended and branched reaction. Quenched and crystallized samples were fabricated using compression molding under different cooling conditions in‐mold. Effects of crystallinity and ADR on mechanical performances of the PLA/TPEE sample were investigated. With increasing the crystallinity, the PLA/TPEE sample shows a marked enhancement in heat resistance. However, the tensile ductility of the crystallized PLA/TPEE sample drastically decreases due to the formation of firm crystal crosslinking and the incompatibility between PLA and TPEE. It is notable that the tensile ductility of the crystallized samples is improved with the introduction of ADR owing to its reactive compatibilization effect. Finally, the crystallized PLA/TPEE/ADR samples with improved heat resistance and relative higher ductility are obtained. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46343.     

Improvement of microstructures and properties of poly(lactic acid)/poly(ε‐caprolactone) blends compatibilized with polyoxymethylene

Incompatibility of poly(lactic acid)/poly(?‐caprolactone) (PLA/PCL) (80:20) and (70:30) blends were modified by incorporation of a small amount of polyoxymethylene (POM) (≤3 phr). Impact of POM on microstructures and tensile property of the blends were investigated. It is found that the introduction of POM into the PLA/PCL blends significantly improves their tensile property. With increasing POM loading from zero to 3 phr, elongation at break increases from 93.2% for the PLA/PCL (70:30) sample to 334.8% for the PLA/PCL/POM (70:30:3) sample. A size reduction in PCL domains and reinforcement in interfacial adhesion with increasing POM loading are confirmed by SEM observations. The compatibilization effect of POM on PLA/PCL blends can be attributed to hydrogen bonding between methylene groups of POM and carbonyl groups of PLA and PCL. In addition, nonisothermal and isothermal crystallization behaviors of PLA/PCL/POM (70:30:x) samples were investigated by using differential scanning calorimetry and wide angle X‐ray diffraction measurements. The results indicate that the crystallization dynamic of PLA matrix increases with POM loadings. It can be attributed to the fact that POM crystals have a nucleating effect on PLA. While crystallization temperature is 100 °C, crystallization half‐time can reduce from 9.4 to 2.0 min with increasing POM loading from zero to 3 phr. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46536.     

Elaboration and characterization of bioblends based on PVC/PLA

With the aim to develop new biomaterials (bioblends) to be used in the field of waste elimination, this contribution focuses on the elaboration and characterization of new materials based on poly (vinyl chloride) (PVC) and poly (lactic acid) (PLA). The bioblends based on PVC/PLA were prepared by melt mixing in the absence and presence of maleic anhydride (MAH). The binary blends were first characterized in terms of thermal (glass transition temperature) and mechanical properties (tensile and micro‐hardness). Their thermal stability was investigated by thermogravimetric analysis (TGA). The results showed that this pair of polymers is not miscible and exhibited lower properties than those of the separated polymers. The in situ compatibilization was then performed using MAH and dicumyl peroxide (DCP) as an initiator. The presence of MAH enhanced the processability of the bioblends by decreasing the temperature of mixing. The properties of subsequent PVC/PLA bioblends were investigated through tensile and micro‐hardness testing, thermal analysis (DSC and TGA), and SEM. From the mechanical results, high level of compatibility was found when introducing MAH. The TGA studies indicated that the incorporation of PLA in PVC (matrix) increased thermal stability of the bioblend. Microscopic observations revealed uniformly dispersed PLA in the PVC matrix, confirming that phase separation has disappeared in the presence of MAH. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40045.     

Electrospinning core‐shell nanofibers for interfacial toughening and self‐healing of carbon‐fiber/epoxy composites

This article reports a novel hybrid multiscale carbon‐fiber/epoxy composite reinforced with self‐healing core‐shell nanofibers at interfaces. The ultrathin self‐healing fibers were fabricated by means of coelectrospinning, in which liquid dicyclopentadiene (DCPD) as the healing agent was enwrapped into polyacrylonitrile (PAN) to form core‐shell DCPD/PAN nanofibers. These core‐shell nanofibers were incorporated at interfaces of neighboring carbon‐fiber fabrics prior to resin infusion and formed into ultrathin self‐healing interlayers after resin infusion and curing. The core‐shell DCPD/PAN fibers are expected to function to self‐repair the interfacial damages in composite laminates, e.g., delamination. Wet layup, followed by vacuum‐assisted resin transfer molding (VARTM) technique, was used to process the proof‐of‐concept hybrid multiscale self‐healing composite. Three‐point bending test was utilized to evaluate the self‐healing effect of the core‐shell nanofibers on the flexural stiffness of the composite laminate after predamage failure. Experimental results indicate that the flexural stiffness of such novel self‐healing composite after predamage failure can be completely recovered by the self‐healing nanofiber interlayers. Scanning electron microscope (SEM) was utilized for fractographical analysis of the failed samples. SEM micrographs clearly evidenced the release of healing agent at laminate interfaces and the toughening and self‐healing mechanisms of the core‐shell nanofibers. This study expects a family of novel high‐strength, lightweight structural polymer composites with self‐healing function for potential use in aerospace and aeronautical structures, sports utilities, etc. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Drying biodegradable poly(hydroxybutyrate‐co‐3‐hydroxyvalerate) gels in the elongated state to improve their mechanical properties

Polyhydroxyalkanoates are a class of biodegradable polymers that may be used more as environmentally friendly materials if their mechanical properties can be improved. We approached this goal by modifying poly(3‐hydroxybutyrate‐co‐3‐hydroxyvalerate) with a well‐established processing technique involving crosslinking the polymer chains and then drying a swollen gel of the network under uniaxial strain. The mechanical properties of the resulting oriented films were determined in continuous extension as a function of the degree of crosslinking and the extent of strain during the drying process. Crosslinking invariably improved the toughness. Similarly, the subsequent orientation of the process generally increased the toughness as well, but in some cases, a reduction in the extensibility offset the increase in the ultimate stress at break and yielded reduced values of the toughness. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 95: 1519–1523, 2005