Melt Mixing Method Research Articles

A Simple Approach to Control the Physical and Chemical Features of Custom-Synthesized N-Doped Carbon Nanotubes and the Extent of Their Network Formation in Polymers: The Importance of Catalyst to Substrate Ratio

This study intends to reveal the significance of the catalyst to substrate ratio (C/S) on the structural and electrical features of the carbon nanotubes and their polymeric nanocomposites. Here, nitrogen-doped carbon nanotube (N-MWNT) was synthesized via a chemical vapor deposition (CVD) method using three ratios (by weight) of iron (Fe) catalyst to aluminum oxide (Al2O3) substrate, i.e.,1/9, 1/4, and 2/3, by changing the Fe concentration, i.e., 10, 20, and 40 wt.% Fe. Therefore, the synthesized N-MWNT are labelled as (N-MWNTs)10, (N-MWNTs)20, and (N-MWNTs)40. TEM, XPS, Raman spectroscopy, and TGA characterizations revealed that C/S ratio has a significant impact on the physical and chemical properties of the nanotubes. For instance, by increasing the Fe catalyst from 10 to 40 wt.%, carbon purity increased from 60 to 90 wt.% and the length of the nanotubes increased from 1.2 to 2.6 µm. Interestingly, regarding nanotube morphology, at the highest C/S ratio, the N-MWNTs displayed an open-channel structure, while at the lowest catalyst concentration the nanotubes featured a bamboo-like structure. Afterwards, the network characteristics of the N-MWNTs in a polyvinylidene fluoride (PVDF) matrix were studied using imaging techniques, AC electrical conductivity, and linear and nonlinear rheological measurements. The nanocomposites were prepared via a melt-mixing method at various loadings of the synthesized N-MWNTs. The rheological results confirmed that (N-MWNTs)10, at 0.5–2.0 wt.%, did not form any substantial network through the PVDF matrix, thereby exhibiting an electrically insulative behavior, even at a higher concentration of 3.0 wt.%. Although the optical microscopy, TEM, and rheological results confirmed that both (N-MWNTs)20 and (N-MWNTs)40 established a continuous 3D network within the PVDF matrix, (N-MWNTs)40/PVDF nanocomposites exhibited approximately one order of magnitude higher electrical conductivity. The higher electrical conductivity of (N-MWNTs)40/PVDF nanocomposites is attributed to the intrinsic chemical features of (N-MWNTs)40, such as nitrogen content and nitrogen bonding types.

Effect of Polyethylene Structure on the Properties of Carbon Nanotube/Polyethylene Composites

The influence of polyethylene (PE) molecular structure on multi-walled carbon nanotubes (MWCNT)/PE composites processing behavior and their thermal, rheological and electrical properties were investigated. Two different types of PE of almost the same viscosity were investigated; namely, high-density polyethylene (HDPE) and low-density polyethylene (LDPE). Nanocomposites filled with up to 10 wt.% MWCNT were prepared by the conventional melt-mixing method. The MWCNT exhibited better dispersion in HDPE than in LDPE. The crystallinity of the HDPE marginally increased with the addition of the MWCNT, while no significant influence of the MWCNT on the LDPE crystallinity was observed. The AC electrical conductivity of both the HDPE and LDPE nanocomposites were almost the same. Thus, we concluded that there is no significant effect of the PE structure on the formation of the MWCNT networks.

The study On Mechanical Properties of HDPE Hybrid Polymer based Hybrid Composites

Polymer and their composites are used in many engineering applications as an alternate of metals, because of the parameters such as low cost, light weight and durability. Hybridization is a process of mixing two or more similar or dissimilar materials. It increases the performance and efficiency. In this study investigation has been made on mechanical properties of HDPE polymer based hybrid composites fabricated from the effect of various synthetic fibers (SGF ,PTFE,SCF), synthetic fillers(Silica, hydroxyapatite, zirconia) by melt mixing method using twin screw extruder followed by injection molding technique. The mechanical properties of the samples such as tensile test, flexural test were measured by universal testing machine. And the impact test was performed on Izod impact testing machine. The results show that the tensile strength of hybrid composite TR-4 sample increases compared to other composites. Flexural strength of sample TR-6 shows highest flexural strength comparted to others. The impact strength increases when the filler materials 2% of zirconia and 2% of hydroxyapatite are added to composite material i.e. is TR-6 sample.

Quantifying morphological and mechanical properties of thermoplastics elastomers by selective localization of nanofillers with different geometries

Potential role of nanofiller in deciding their localization in polypropylene (PP)-natural rubber (NR) blend system is evaluated using experimental techniques followed by authentication using various theoretical approaches. Thermoplastic elastomers (TPEs) of PP-NR blend-based nanocomposites with Cloisite 15A and titanium dioxide (TiO2) were prepared by melt mixing method, using Haake rheocord-90. In pre-fixed blend composition of 70-30 (PP-NR), selective localization of nanofiller was determined by transmission electron microscopy (TEM), and quantified by Harmonic mean theoretical studies. Correlation length (ξclay) and average length of the clay layers (Lclay) measured for the dispersion of nanoclay. The dispersion efficiency of Cloisite 15A and TiO2 in blend matrix were determined by X-ray diffraction (XRD) studies. Mechanical properties of blend nanocomposites were examined by varying the nanofiller loading and compared with theoretical approaches such as Kerner, Guth, Halpin-Tsai, Einstein and Quemada models. It was found that irrespective of the geometry, the fillers migrated to the PP phase leading to significant changes in morphological development (size reduction of dispersed phase) and increased mechanical properties of 70-30 (PP-NR) neat blend. Nevertheless, it is very important to mention that at higher loading the layers of Cloisite 15A are found to penetrate partially into the NR phase due to the anisotropic nature of the clay platelets.

Layered Double Hydroxide (MgFeAl-LDH)-Based Polypropylene (PP) Nanocomposite: Mechanical Properties and Thermal Degradation.

This work analyzes the thermal degradation and mechanical properties of iron (Fe)-containing MgAl layered double hydroxide (LDH)-based polypropylene (PP) nanocomposite. Ternary metal (MgFeAl) LDHs were prepared using the urea hydrolysis method, and Fe was used in two different concentrations (5 and 10 mol%). Nanocomposites containing MgFeAl-LDH and PP were prepared using the melt mixing method by a small-scale compounder. Three different loadings of LDHs were used in PP (2.5, 5, and 7.5 wt%). Rheological properties were determined by rheometer, and flammability was studied using the limiting oxygen index (LOI) and UL94 (V and HB). Color parameters (L*, a*, b*) and opacity of PP nanocomposites were measured with a spectrophotometer. Mechanical properties were analyzed with a universal testing machine (UTM) and Charpy impact test. The thermal behavior of MgFeAl-LDH/PP nanocomposites was studied using differential scanning calorimeter (DSC) and thermogravimetric analysis (TGA). The morphology of LDH/PP nanocomposites was analyzed with a scanning electron microscope (SEM). A decrease in melt viscosity and increase in burning rate were observed in the case of iron (Fe)-based PP nanocomposites. A decrease in mechanical properties interpreted as increased catalytic degradation was also observed in iron (Fe)-containing PP nanocomposites. Such types of LDH/PP nanocomposites can be useful where faster degradation or faster recycling of polymer nanocomposites is required because of environmental issues.

Study on Abrasion Wear behaviour of Hybrid Composites using dimensional Analysis and Wear Models

The prediction of abrasive wear behavior of Glass-Basalt (GB) and Glass -Carbon (GC) hybrid composites in two body wear mode using dimensional analysis has been presented. The blend (PA66/PTFE) in 80/20 wt. % proportion was used as the base material. The individual effect of glass fibers and carbon fibers (10 wt. % each) were also studied and compared. Melt mix method using twin screw extrusion and injection molding process were used for developing hybrid composites. The mathematical model to predict the wear loss has been developed using dimensional analysis for the aforesaid hybrid composites and evaluated through justification using experimentally determined wear loss. Further, the wear behavior due to two body abrasion of hybrid composites is justified using abrasive wear models. It is noticed that developed mathematical model and wear models agrees with the abrasion wear behavior of composites studied. It is noticed that Ratner -Lancaster factor (σε) was used as one variable for the abrasion wear model. It is proved that specific wear rate is indirectly proportional to the wear resistance. Furthermore, the individual effect of short fibers is compared with GB and GC hybrid composites. It is proved that hybrid composites exhibited the better wear resistance.

Mechanical Properties of Composite Materials from Waste Poly(ethylene terephthalate) Reinforced with Glass Fibers and Waste Window Glass

After primary uses of the plastic product, most developing countries like Ethiopia are facing a shortage of postconsumer disposal waste sites and it became a very serious problem on environmental pollution due to its nonbiodegradable nature. For this reason, regenerating and using the waste product as resources and reducing environmental pollutions are a great opportunity. This research is aimed at the manufacturing of composite materials from waste poly(ethylene terephthalate) (PET) bottles reinforced with glass fibers and filled with waste glass powder for floor tile applications. The tile composites were prepared by the melt-mixing method followed by compression molding. The effect of filler, fiber, and PET matrix loading on the composite was investigated using their tensile, compression, and flexural strength tests. The sample was characterized using a universal testing machine. PerkinElmer FTIR instrument was also used. For this, eleven samples prepared by varying the glass fiber weight % from 0 to 10, PET matrix weight % from 70 to 85, and glass powder filler weight % from 5 to 20. The measurement results of the composite were maximum tensile strength (81.625 MPa) and flexural strength (1067.59 MPa) recorded at 10%weight of glass fiber, 85% weight of PET matrix, and 5%weight of window glass filler. The maximum compressive strength is 1876.14 MPa at 10% weight glass fiber, 70 wt% PET matrix, and 20 wt% window glass filler. Based on this, the tensile strength and flexural strength increased with increased weight % of glass fiber and decreased with increased window glass filler. The FTIR spectrum shows some of the groups that have been removed from the recycled PET; this explains the brittleness of the recycled PET as compared to the waste bottle PET. The microstructure was uniformly distributed, and the material became opaque, probably because the decrease in chain length improves chain packing, increasing the crystallinity degree and crystal size.

Effect of fiber loading on mechanical, physical behavior of thermoplastic blend composites

The short fiber reinforced hybrid thermoplastic blend composites is most widely used in aerospace & automobile industries. Individual fibres and their hybrid effect on mechanical characterisation are the focus of this article. The materials used for the study are Polyamide66 (PA66), Polypropylene (PP), Short glass fibers (SGF) and Short basalt fibers (SBF). The material system used for the study are Blend (PA66/PP), Blend/SGF, Blend/SBF and Blend/SGF/SBF. Melt mix method with twin screw extruder is used to manufacture composite material systems. ASTM standards were used to evaluate the composites physical and mechanical properties, such as hardness, density, tensile, flexure, and impact strength. The experimental data indicated that the mechanical properties particularly tensile and flexural strength enhanced significantly by the insertion of short fibers into thermoplastic blend. Further the impact properties reduced due the brittle nature of the fibers in the blend composites. The density as well as the hardness of the short fiber reinforced composites increases with respect to the blend. The failure mechanism of the composites due the mechanical characterization is observed through the SEM pictures.

Micro fillers effect on two body abrasive wear behavior of Polyamide 66, Polyamide 6 blend based composites

The effect of hybrid micro fillers on two body abrasive wear of PA66/PA6 blend based composites was investigated. Three composites: Blend (PA66/PA6) (80/20 wt%), Blend/10 wt% PTFE and Blend/10 wt% PTFE/5 wt% MoS2 were considered for the investigation. These micro composites were prepared by using melt mix method using twin screw extrusion technique. The two-body abrasion wear behavior of these micro composites was investigated using 180 grit SiC abrasion paper in a multipass condition as per ASTM G99 standard under the influence of variable abrasion load at a constant velocity of 0.5 m/s. It is found from the experimentation that the volumetric wear loss is totally dependent on abrading load. Further, it is found that Blend/PTFE composites exhibited good abrasion wear behaviour due to excellent Ratner-Lancaster (σε) factor. Micro ploughing and micro cutting were noticed during the morphological study through SEM images. Among the micro composites studied, Blend/10 wt% PTFE exhibited better abrasive wear resistance compared to other composites.

Exploring the three body abrasive wear behavior of glass – Carbon thermoplastic hybrid composites

The interaction effect of abrasive particles on three body abrasion wear behavior of Glass – Carbon thermoplastic hybrid composites was investigated. The blend (PA66/PTFE) (80/20 wt%), Blend/Short glass fiber (SGF), Blend/Short Carbon fiber (SCF), Blend/10 wt% SGF/10 wt% SCF (GC) were the material systems considered for the study. The melt mix method with the help twin screw extruder and injection molding were the methods used for processing and development of hybrid composites. The experimentation was conducted for 20 N and 30 N using varying distance at a constant velocity of 2.5 m/s in accordance with ASTM G65 method. The unique observation has been made from the fiber filled composites. The three body abrasion wear behavior has been effectively improved due to fiber reinforcement. The individual fibers have their own contribution in developing the abrasion resistance. The hardness and ultimate tensile strength of the composites have supported the wear resistance. Further, the Ratner – Lancaster factor (σε) of composites played the significant role in enhancing the wear behavior under three body mode. SCF filled composites exhibited better wear behavior than SGF filled ones. The hybridization effect of both SGF and SCF effectively improved the abrasion wear resistance of GC hybrid composites. The high crystallanity, hardness and hardness ratio between polymer and rubber wheel helped in improving the abrasion wear behavior of hybrid composites. The morphology of the abraded surfaces were studied using SEM images.

Phenol functionalized high‐density polyethylene as compatibilizer of high‐density polyethylene/graphene nanocomposites toward enhanced mechanical and interfacial adhesion

AbstractIn this work, the methodology to obtain high‐density polyethylene (HDPE) and graphene (G) nanocomposites using phenol‐modified graphene and phenol‐modified HDPE as compatibilizer obtained from the reaction of malleated polyethylene (HDPE‐g‐MA) with phenol, is described. Six different methods were used to obtain these composites, resulting from the combination of melt and solution mixing with three different procedures to functionalize either graphene or HDPE‐g‐MA with phenol. Nanocomposites were characterized by Fourier transform infrared (FTIR), scanning electron microscopy (SEM), wide angle X‐ray diffraction (WAXD), dynamic mechanic analysis (DMA) and tensile properties. The FTIR results evidenced the occurrence of an esterification reaction between HDPE‐g‐MA and phenol groups serving as compatibilizer. The SEM and WAXD results showed that the addition of this compatibilizer agent had a positive effect on graphene dispersion, which promoted greater stiffness in these composite materials, presenting higher storage modulus. In addition, a noticeable enhancement in dimensional stability at high temperatures was observed according to Tan Delta measurements. These results indicated a good interfacial adhesion between graphene and the polymer matrix by using this compatibilizer agent. It was observed that the composites obtained by solution mixing method showed better performance and stronger interfacial adhesions than the composites produced by melt mixing methods. The use of this phenol modified HDPE compatibilizer offers a new option to enhance the final performance of HDPE/graphene composites with better mechanical and thermal properties to be used in materials for various applications, such as automotive industry, electrical and electronics, construction, aerospace, and other engineering applications.

Potential of natural fibers in the modification of mechanical behavior of polypropylene hybrid composites

The effect of natural fiber loading on Mechanical characteristics of Polypropylene based hybrid composites is reported. Four composite systems were considered for investigation: Neat Polypropylene (PP), PP/5 wt% sisal fiber/5 wt% Ramie fiber (PP/10), PP/10 wt% sisal fiber/10 wt% Ramie fiber (PP/20) and PP/15 wt% sisal fiber/15 wt% Ramie fiber (PP/30). The hybrid composites were processed and developed by melt mix method with the help of Twin screw extrusion and injection molding. The mechanical response of hybrid composites was investigated through tensile behaviour, flexural behavior and impact behaviour in accordance with ASTM method at room temperature. It was found from the experimented results that the individual fibers had their own sole impact on mechanical properties of Polypropylene natural composites. It was revealed that the hybrid fiber loading has promoted the mechanical behaviour of PP based fibrous composites. It was found that tensile strength and flexural strength of PP/30 hybrid composites was enhanced by 11% and 52% over neat PP as an effect of inclusion of natural fibers. This is because of the enhancement of modulus of PP/30 composites. Further, the significant surface interaction of natural fibers with the matrix made hybrid composites to exhibit good mechanical properties. The reinforcement of effect of hybrid fibers totally decreased the impact strength. It was noticed that the impact strength of PP/30 composites was same as that of neat PP. The SEM photographs exhibits the morphology of fractured surfaces. Among the hybrid composites studied, PP/30 hybrid composites exhibited the better mechanical behavior.

Barrier Properties and Hydrophobicity of Biodegradable Poly(lactic acid) Composites Reinforced with Recycled Chinese Spirits Distiller's Grains.

Adding natural biomass to poly(lactic acid) (PLA) as a reinforcing filler is a way to change the properties of PLA. This paper is about preparing PLA/biomass composites by physically melting and blending Chinese Spirits distiller’s grains (CSDG) biomass and PLA to optimize the composite performance. Composites of modified PLA (MPLA) with varying amounts of CSDG were also prepared by the melt-mixing method, and unmodified PLA/CSDG composites were used as a control group for comparative analysis. The functional groups of MPLA enhanced the compatibility between the polymer substrate and CSDG. The composite water vapor/oxygen barrier and mechanical properties were studied. It was found that the barrier and mechanical properties of MPLA/CSDG composites were significantly improved. SEM was adopted to examine the tensile section structure of the composites, and the compatibility between the filler and the matrix was analyzed. An appropriate amount of CSDG had a better dispersibility in the matrix, and it further improved the interfacial bonding force, which in turn improved the composite mechanical properties. X-ray diffraction, thermogravimetric analysis, and differential scanning calorimetry were conducted to determine the crystalline properties and to analyze the stability of the composites. It was found that the CSDG content had a significant effect on the crystallinity. Barrier and biodegradation mechanisms were also discussed.

Effect of thermoplastic polyurethane elastomer on the properties of polybutylene terephthalate matrix flame retardant composites

Using brominated polystyrene (BPS) as flame retardant, Sb2O3 nanoparticles (nano-Sb2O3) as synergistic flame retardant, polybutylene terephthalate (PBT) as matrix and thermoplastic polyurethane elasticity (TPU) as a toughening component, TPU/nano-Sb2O3-BPS-PBT flame retardant composites were obtained by ball milling dispersion and melt-mixing methods. The mechanical and flame retardant properties of the TPU/nano-Sb2O3-BPS-PBT composites were studied by DSC, tensile, impact and limiting oxygen index (LOI) test. The results show that the TPU can enhance the toughness of the TPU/nano-Sb2O3-BPS-PBT flame retardant composites. With increasing of the mass fraction of TPU, the notched impact strength of the TPU/nano-Sb2O3-BPS-PBT flame retardant composites increases. Furthermore, when the mass fraction of TPU is 9wt%, its impact strength increases by 137% and the elongation at break increases by 340% compared with those of pure PBT, but its tensile strength decreases. The tensile strength of the composites is greater than that of pure PBT when the mass fraction of TPU is 3wt%, which its impact strength is 52% higher than that of the pure PBT. The TPU/nano-Sb2O3-BPS-PBT flame retardant composites reach flame-resistant grade and the composites show superior comprehensive performance.

An experimental study on multiwalled carbon nanotube nanocomposite piezoresistivity considering the filler agglomeration effects

AbstractPiezoresistive strain sensing of multiwalled carbon nanotube (CNT)‐reinforced polymer nanocomposites considering the effect of agglomeration is experimentally investigated. Thermoplastic polyurethane is used as composite matrix with melt mixing method for fabricating the nanocomposite. The electrical resistance of the nanocomposite specimens is measured by a designed electrical circuit in conductivity and piezoresistivity tests. The electrical resistance of the nanocomposite decreases by a nonlinear relation when CNT is added up to 1.5 wt% and has an inverse behavior after this weight fraction. Comparison between scanning electron microscope images of the nanocomposite specimen fracture surfaces shows that the CNT agglomeration is the reason for decreasing the nanocomposite electrical properties. Also, decrease of the mechanical properties of the nanocomposite in higher filler content than 1.5 wt%, confirms the agglomeration effects. In addition, it is illustrated that the CNT agglomeration decreases strain sensing in the nanocomposite. Moreover, different piezoresistive behaviors of the nanocomposite in low and large strains are explained, according to the piezoresistivity mechanisms. Change of the piezoresistivity mechanism type, causes a nonlinear growth of the nanocomposite electrical resistance, in large strain.

Structure and Properties of Polyoxymethylene/Silver/Maleic Anhydride-Grafted Polyolefin Elastomer Ternary Nanocomposites.

In the present study, silver (Ag) nanoparticles and maleic anhydride-grafted polyolefin elastomer (MAH-g-POE) were used as enhancement additives to improve the performance of the polyoxymethylene (POM) homopolymer. Specifically, the POM/Ag/MAH-g-POE ternary nanocomposites with varying Ag nanoparticles and MAH-g-POE contents were prepared by a melt mixing method. The effects of the additives on the microstructure, thermal stability, crystallization behavior, mechanical properties, and dynamic mechanical thermal properties of the ternary nanocomposites were studied. It was found that the MAH-g-POE played a role in the bridging of the Ag nanoparticles and POM matrix and improved the interfacial adhesion between the Ag nanoparticles and POM matrix, owing to the good compatibility between Ag/MAH-g-POE and the POM matrix. Moreover, it was found that the combined addition of Ag nanoparticles and MAH-g-POE significantly enhanced the thermal stability, crystallization properties, and mechanical properties of the POM/Ag/MAH-g-POE ternary nanocomposites. When the Ag/MAH-g-POE content was 1 wt.%, the tensile strength reached the maximum value of 54.78 MPa. In addition, when the Ag/MAH-g-POE content increased to 15wt.%, the elongation at break reached the maximum value of 64.02%. However, when the Ag/MAH-g-POE content further increased to 20 wt.%, the elongation at break decreased again, which could be attributed to the aggregation of excessive Ag nanoparticles forming local defects in the POM/Ag/MAH-g-POE ternary nanocomposites. Furthermore, when the Ag/MAH-g-POE content was 20 wt.%, the maximum decomposition temperature of POM/Ag/MAH-g-POE ternary nanocomposites was 398.22 °C, which was 71.39 °C higher than that of pure POM. However, compared with POM, the storage modulus of POM/Ag/MAH-g-POE ternary nanocomposites decreased with the Ag/MAH-g-POE content, because the MAH-g-POE elastomer could reduce the rigidity of POM.

Effect of the selective localization of carbon nanotubes and phase domain in immiscible blends on tunable microwave dielectric properties

In recent years, the immiscible polymer blend system has attracted much attention as the matrix of nanocomposites. Herein, from the perspective of dynamics, the control of the carbon nanotubes (CNTs) migration aided with the interface of polystyrene (PS) and poly (methyl methacrylate) (PMMA) blends was achieved through a facile melt mixing method. Thus, we revealed a comprehensive relationship between several typical CNTs migrating scenarios and the microwave dielectric properties of their nanocomposites. Based on the unique morphologies and phase domain structures of the immiscible matrix, we further investigated the multiple microwave dielectric relaxation processes and shed new light on the relation between relaxation peak position and the phase domain size distribution. Moreover, by integrating the CNTs interface localization control with the matrix co-continuous structure construction, we found that the interface promotes double percolation effect to achieve conductive percolation at low CNTs loading (~1.06 vol%). Overall, the present study provides a unique nanocomposite material design symphonizing both functional fillers dispersion and location as well as the matrix architecture optimization for microwave applications.

LDPE:PLA and LDPE:PLA:OMMT polymer composites: Preparation, characterization, and its biodegradation using Bacillus species isolated from dumping yard

AbstractThe focus of the present research is on the biodegradation of low density polyethylene (LDPE):polylactic acid (PLA) and LDPE:PLA:organo modified montmorillonite (OMMT) polymer nanocomposites. PLA was synthesized using the polycondensation method. The surface modification of nanomaterials is affected by various factors such as modifying agent, dispersion medium, and the dispersion of nanoparticles. Ultrasound cavitation technique improves the better dispersion of MMT in reaction mixture and enhances the interaction rate of a modifying agent with clay layered structure. A mixture of aminopropyltriethoxysilane and octadecyl amine was used for the surface modification of MMT. Polymer nanocomposite was prepared using the melt mixing method and used further for the biodegradation study. The mesophilic bacterium isolated from the dumping yard, identified by the 16rRNA technique, was capable of biodegradation of LDPE:PLA and LDPE:PLA:OMMT polymer nanocomposites. Isolated bacterial AP1 is 96.05% identical to the current MCCC1A02146 strain of Bacillus albus. After 50 days of incubation, the polymer nanocomposite sheet was characterized using Fourier transform infrared, X‐ray powder diffractometer, UV–Visible spectroscopy, Field Emission Scanning Electron Microscope (FESEM), etc. Further, LDPE:PLA30% (17.5%) and LDPE:PLA30%:OMMT4.5phr (19.20%), shows maximum percentage degradation. It has been observed that the addition of OMMT contributes to an enhancement in the polymer nanocomposite degradation because it has a large d‐spacing gap that is (21 Å) that enables the water to penetrate in the polymer matrix and increases the growth of bacteria within the polymer matrix. The highest change in biomass and change in extracellular protein content was found to be (39.11 mg/L and OD 0.38) LDPE:PLA30%:OMMT4.5phr composites. In addition, the mechanical properties decrease effectively after the incubation period, for LDPE:PLA 30% and LDPE:PLA30%:OMMT4.5phr.

Designing self-crosslinkable ternary blends using epoxidized natural rubber (ENR)/poly(ethylene-co-acrylic acid)(EAA)/poly(ε-caprolactone) (PCL) demonstrating triple-shape memory behavior

The aim of this work is developing a facile and versatile route for preparing chemically crosslinked triple-shape memory polymers (SMPs). Hence, epoxidized natural rubber(ENR)/poly(ethylene-co-acrylic acid)(EAA)/poly(ε-caprolactone) (PCL) ternary blends were fabricated using the facile melt-mixing method. Interestingly, it was observed that the resultant ternary blends could self-crosslink during molding at high temperature without need for any crosslinking agents. Differential scanning calorimeter (DSC) and dynamic mechanical analyzer (DMA) analyses revealed that all of the ternary blends have two well-separated thermal transitions (Tm, PCL and Tm, EAA) and, as a result, they exhibited triple-SM behavior. Moreover, the mechanical properties as well as shape memory effect of ternary blends were improved with carboxylation of PCL. The developed ternary blends can be considered as a promising SM material in many in-vivo and aerospace applications.

Effect of ion-crosslinking on supercritical CO2 foaming behavior and foam properties of EVA/ZnO composites

How to realize the recycling of materials is an important topic for polymer materials, especially crosslinked polymers. In this work, by means of the reaction of zinc oxide (ZnO) and maleic anhydride group, ethylene-vinyl acetate copolymer (EVA)/ZnO composites with reversible ion-crosslinking structure were prepared by melt mixing method. The gel content and the degree of ion crosslinking in EVA were tracked using the THF extraction method. The presence of ion-crosslinking structure strongly affected the foaming behavior of EVA composites in supercritical CO2 (sc-CO2) molding foaming process. The influence of the ion crosslinking on the structure and properties of EVA foams was studied by means of SEM and compression set test etc. The results showed that the appropriate degree of ion-crosslinking was beneficial to increase the volume expansion rate and cell density of the obtained foams, and reduce the average cell diameter and compression set of the foams. The obtained EVA composite foams showed good resilience and melt-reprocessing performance. However, too high ion-crosslinking degree severely limited the growth of cells due to the difficulty of molecular chain movement. At the same time, the excessive ZnO in the matrix had an adverse effect on the compression set of EVA foam.