Crystallization and melting behaviors of maleated polyethylene and its composite with fibrous cellulose

The crystallization and melting behaviors of maleated polyethylene (MPE) and its composite with fibrous crystalline cellulose are investigated by differential scanning calorimetry. MPE exhibits a higher crystallization starting temperature, because of the interactions between maleic anhydride (MA) groups for nucleation, and lower melting and crystallization enthalpies, because of the intensive irregularity of MPE chains compared to unmaleated PE (UPE). Fibrous cellulose (FC) slightly facilitates the nucleation of MPE but causes no change in the transition enthalpies of MPE for crystallization and melting in UPE–FC and MPE–FC composites. The kinetics of crystallization show that the Avrami exponent depends on the content of MA groups and FC to a small extent and the activation energy is largely determined by the MA content, suggesting the irregularity and decreased mobility of MPE chains that is due to the interactions between the grafted MA groups in MPE and the FC composite. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 3292–3300, 2003     

Microstructure and mechanical properties of a polyethylene/polydimethylsiloxane composite prepared using supercritical carbon dioxide

A polymer composite of polyethylene (PE) and polydimethylsiloxane (PDMS) was prepared using supercritical carbon dioxide despite the two polymers usually being immiscible and possessing a phase‐separated morphology. This article reports in detail the preparation, microstructure, crystallinity, and mechanical properties of the resulting PE/PDMS composite. The formation mechanism of the PE/PDMS composite consisted of supercritical impregnation of an octamethylcyclotetrasiloxane (D4) monomer and an initiator into a PE substrate followed by in situ polymerization within the substrate. Differential scanning calorimetry, wide‐angle X‐ray diffraction, and small‐angle X‐ray scattering measurements showed that PE and PDMS were blended at the nanometer level. The PDMS generated in the amorphous region of PE did not affect its crystallinity. Dynamic viscoelastic analyses and tensile tests were used to measure the mechanical properties of the composites including storage and Young's modulus, fracture stress, and strain. These properties were found to depend on the composition of the composite. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Structure and properties of composites of polyethylene or maleated polyethylene and cellulose or cellulose esters

Composites of linear low‐density poly(ethylene‐co‐butene) (PE) or maleated linear low‐density poly (ethylene‐co‐butene) (M‐PE) and cellulose (CEL), cellulose acetate (CA), cellulose acetate propionate (CAP), or cellulose acetate butyrate (CAB) were prepared in an internal laboratory mixer with 20 wt % polysaccharide. The structure and properties of the composites were studied with tensile testing, dynamic mechanical thermal analysis, differential scanning calorimetry, extraction with a selective solvent, Raman spectroscopy, and X‐ray diffraction. Composites prepared with M‐PE presented yield stress and elongation values higher than those of composites prepared with PE, showing the compatibilizer effect of maleic anhydride. Dynamic mechanical thermal analysis performed for M‐PE–CEL, M‐PE–CA, M‐PE–CAP, and M‐PE–CAB composites showed one glass‐transition temperature (T_g) close to that observed for pure M‐PE, and for M‐PE–CAP, another T_g lower than that measured for the polysaccharide was observed, indicating partial mutual solubility. These findings were confirmed by the extraction of one phase with a selective solvent, gravimetry, and Raman spectroscopy. X‐ray diffraction showed that the addition of CEL, CA, CAP, or CAB had no influence on the lattice constants of PE or M‐PE, but the introduction of the reinforcing material increased the amorphous region. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103:402–411, 2007     

Rheological behavior and mechanical properties of sawdust/polyethylene composites

We have characterized the melt rheological behavior and the solid tensile properties of sawdust/polyethylene composites prepared in an internal mixer. Various concentrations (from 0 to 60 wt %) and three particle sizes have been tested, in presence of a coupling agent (maleic anhydride grafted polyethylene). In the molten state, for each particle size, a mastercurve of the complex viscosity as function of frequency can be plotted, using a shift factor depending on weight fraction. We show that the shift factors can be described by a Krieger‐Dougherty law, leading to a “universal” viscosity law of the Carreau‐Yasuda type. In the solid state, the presence of sawdust increases Young modulus in uniaxial elongation, mainly for small size particles, but reduces dramatically deformation at break and tensile strength. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Influence of maleated polypropylene on mechanical properties of composite made of viscose fiber and polypropylene

The purpose of this work was to study how viscose fiber behaves in polypropylene (PP) matrix when maleated polypropylene (MAPP) is used as a coupling agent. The influences of processing conditions on composite properties was of interest. Composites were characterized by FTIR and mechanical testing. The most notable result was the effect of the MAPP concentration on the tensile strength of the composites; the tensile strength increased from 40 to 69 MPa when MAPP was added in amounts up to 6 wt % of the fiber weight. The interaction between MAPP and fiber was confirmed with FTIR. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 87: 1895–1900, 2003     

Interfacial interaction,morphology, and tensile properties of a composite of highly crystalline cellulose and maleated polypropylene

A composite of highly crystalline cellulose was synthesized via a melt‐mixing method with maleic anhydride (MA)‐grafted polypropylene (PP), MAPP, which was prepared by melt‐mixing PP with 0.25–8.0 phr (part of reagent per hundred parts of PP) of MA, and the morphology and tensile properties were examined with respect to the interfacial interactions of MAPP and cellulose. The graft degree (G_d) of MAPP increases with an increase in the initial MA amount up to 2.5 phr, beyond which it decreases because of the remaining of more free MA monomers and/or the formation of more oligomers remaining in the matrix. The morphology and tensile properties of the composite are affected strongly by G_d as well as the presence of the free MA in the matrix. For the MAPP without any free MA, even the G_d value as small as 0.25–0.5 wt % yields a maximal tensile strength. The existence of free MA monomers in the MAPP decreases the tensile strength, probably because of interrupting the interactions of the grafted MA groups with the OH groups of cellulose. The tensile properties of the composite correlate with the interfacial adhesion as well as the dispersion of cellulose microfibers in the matrix, both of which are determined by the interactions of the OH groups on cellulose with the grafted MA groups. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 3830–3841, 2006     

Mechanical properties and applications for floor tiles of a composite from clay and maleated polyethylene

New composites were prepared from dried waste mud containing clay (Clay) and maleated polyethylene (MPE) by melt mixing. Scanning electron microscopy showed strong adhesion of MPE to Clay in the MPE–Clay composite, and this was probably due to the increased compatibility between MPE and Clay. With an increase in the Clay concentration to 60 wt %, the tensile strength of the MPE–Clay composite increased. Furthermore, the smaller elongation of the MPE–Clay composite indicated effective transfer of the high tensile strength of Clay to the MPE matrix through the strong adhesion between Clay and MPE. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 96: 1176–1182, 2005     

Enhanced atomic oxygen erosion resistance and mechanical properties of graphene/cellulose acetate composite films

The application of graphene (Gr) to enhance atomic oxygen (AO) erosion resistance and mechanical properties was demonstrated in this study. Gr‐reinforced cellulose acetate (CA) composite films were obtained by flattening with a glass rod, and the AO erosion resistance was investigated in a plasma‐type, ground‐based AO effect simulation facility. Significant improvements in the mechanical properties and AO erosion resistance were achieved at relatively low Gr contents. A 59 ± 7% decrease in the mass loss and a 12 ± 3% increase in the tensile strength were achieved by the addition of only 1 wt % Gr. Moreover, the layered structure of the fractured surfaces and the excellent mechanical properties illustrated the homogeneous dispersion of Gr in the CA matrix and the strong interactions between Gr and CA. Furthermore, Gr flakes served as shields to defend the underside of CA from AO erosion because of the specific two‐dimensional structure and outstanding AO erosion resistance. Therefore, this research provides a new and effective strategy for improving the mechanical strength and AO erosion resistance of polymer materials. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40292.     

Thermal,dielectric, and mechanical properties of SiC particles filled linear low‐density polyethylene composites

A thermally conductive linear low‐density polyethylene (LLDPE) composite with silicon carbide (SiC) as filler was prepared in a heat press molding. The SiC particles distributions were found to be rather uniform in matrix at both low and high filler content due to a powder mixing process employed. Differential scanning calorimeter results indicated that the SiC filler decreases the degree of crystallinity of LLDPE, and has no obvious influence on the melting temperature of LLDPE. Experimental results demonstrated that the LLDPE composites displays a high thermal conductivity of 1.48 Wm^?1 K^?1 and improved thermal stability at 55 wt % SiC content as compared to pure LLDPE. The surface treatment of SiC particles has a beneficial effect on improving the thermal conductivity. The dielectric constant and loss increased with SiC content, however, they still remained at relatively low levels (<10² Hz); whereas, the composites showed poorer mechanical properties as compared to pure LLDPE. In addition, combined use of small amount of alumina short fiber and SiC gave rise to improved overall properties of LLDPE composites. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Use of titanate to improve interfacial interaction and mechanical properties of polyethylene/artificial marble wastes composites

The resource utilization of artificial marble wastes (AMWs) is urgently needed for environmental protection as a large amount of artificial marble are used as construction material. Nevertheless, it still remains challenging to achieve high performance of AMWs-filled polymer composites due to their poor interfacial interaction with hydrophobic polyolefins. Here, the unsaturated resin residue on the surface of AMWs is employed to construct strong interfacial interaction with high-density polyethylene (HDPE) matrix to prepare mechanically robust polymeric composites by use of titanate coupling agent. The mechanical properties (with a tensile strength of 28.6 MPa and a flexural strength of 27.7 MPa) of the resulting composites are comparable to or even better than those of raw calcium carbonate-filled HDPE composites. This work will not only promote the recycling and reutilization of AMWs, but also provide a feasible way for value-added application of other polymeric wastes, such as waste printed circuit board, waste artificial turf, and so on.     

Preparation and properties of polyethylene terephthalate/polyethylene/near infrared reflective pigment composites

Polyethylene terephthalate/high density polyethylene (PET/HDPE) composites containing a near infrared reflective (NIR, nickel antimony titanium yellow rutile) pigment was prepared using ethylene‐glycidyl methacrylate‐vinyl acetate (EGMA‐VA) as a compatibilizer to increase the infrared reflection of PET/HDPE and limit the thermal heat accumulation in light of environmental and energy conservation concerns. HDPE was premixed with NIR to form N‐HDPE masterbatch. A good interfacial bonding between PET matrix and HDPE dispersed phase with the help of compatibilizer was confirmed through Fourier transform‐infrared spectra, scanning electron microscopy, and torque rheometer. For PET/N‐HDPE composites, the major X‐ray diffraction peaks and melting behaviors remained unchanged, indicating the limited alternation of crystalline structure for the composite systems with or without compatibilizer. The observed increment in the crystallization temperature of PET for the investigated PET/N‐HDPE composites was mainly due to the nucleation role of both inorganic NIR and HDPE. Tensile strength and elongation at break for compatibilized cases at various N‐HDPE contents conferred higher values than those of the corresponding counterparts without compatibilizer. Yet, Young's modulus for compatibilized systems was about 40% lower than that for systems without compatibilizer, attributed to the rubbery nature of EGMA‐VA. With the inclusion of NIR into HDPE to form PET/N‐HDPE composites with or without EGMA‐VA compatibilizer, the values of reflectance increased to a great degree. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40830.     

Reinforcement of maleated polyethylene/ground tire rubber thermoplastic elastomers using talc and wood flour

Maleated polyethylene (MAPE)/Ground tire rubber (GTR) thermoplastic elastomer with 50 vol % GTR was reinforced by incorporation of talc powder and wood flour. Scanning electron microscopy (SEM) reveals that maleated polyethylene (MAPE) has good compatibility with wood flour, but the adhesion with talc particles is weak. Tensile moduli of MAPE/GTR increase more significantly after inclusion of talc particles compared to wood flour. Prediction of the tensile modulus of hybrid MAPE/GTR/particle composites is successfully performed using a combination of Kerner and Halpin‐Tsai models. Elastic moduli are shown to depend strongly on both aspect ratio and level of particle dispersion in the matrix. Measurement of compression sets shows that elastic recovery of the compounds decreases after addition of solid particles. Samples having better particles/matrix compatibility show higher elastic recovery. Thermogravimetric analysis shows that inclusion of wood flour decreases thermal stability of compounds. Density and hardness of MAPE/GTR are also shown to increase after inclusion of particulate reinforcements. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40195.     

Melt miscibility and mechanical properties of metallocene linear low‐density polyethylene blends with high‐density polyethylene: influence of comonomer type

In this paper, the implications of melt miscibility on the thermal and mechanical properties of linear low‐density polyethylene (LLDPE)/high‐density polyethylene (HDPE) blends were assessed with respect to the influence of the comonomer type. The influence of the latter was examined by selecting one butene LLDPE and one octene LLDPE of very similar weight‐average molecular weight (M_w), molecular‐weight distribution (MWD) and branch content, keeping the comonomer type as the only primary molecular variable. Each of the two metallocene LLDPEs was melt‐blended with the same HDPE at 190 °C in a Haake melt‐blender. The rheological, thermal and mechanical properties were measured by the use of an ARES rheometer, differential scanning calorimeter and Instron machine, respectively. The rheological measurements, made over the linear viscoelastic range, suggested no significant influence of the branch type on the melt miscibility. The rheology results are in agreement with those obtained from previous transmission electron microscopy (TEM) and small‐angle neutron scattering (SANS) studies. The dynamic shear viscosity and total crystallinity of the metallocene (m)‐LLDPE blends with HDPE followed linear additivity. At small strains, the branch type has little or no influence on the melt miscibility and solid‐state properties of the blends. Even the large‐strain mechanical properties, such as tensile strength and elongation at break, were not influenced by the comonomer type. However, the ultimate tensile properties of the HDPE‐rich blends were poor. Incompatibility of the HDPE‐rich blends, as a result of the weak interfaces between the blend components, is suggested to develop at large strains. Copyright © 2005 Society of Chemical Industry     

Enhanced mechanical and thermal properties of nanodiamond reinforced low density polyethylene nanocomposites

In this study, the reinforcement effects of low-content hydrophilic nanodiamond (ND) on linear low-density polyethylene (PE) nanocomposites were investigated. ND was incorporated in PE via simple solution blending. The obtained PE/ND nanocomposites were characterized using scanning electron microscopy, ultraviolet–visible spectra, X-ray diffraction, tensile test, thermogravimetry, and differential scanning calorimetry. Generally, PE/ND nanocomposites with poor interfacial interaction cause large agglomerates, resulting in brittle and poor mechanical properties. Owing to the different natures of non-polar PE and polar ND, the higher the ND content, the larger the agglomerates formed in the nanocomposites. However, PE/ND nanocomposites show unique mechanical properties, that is, the Young's modulus, tensile strength, elongation at break, and toughness increased upon the incorporation of ND. The Young's modulus of the PE/ND nanocomposites exceeded the theoretical value calculated using the Halpin–Tsai model. In addition, the toughness increased by 18% at only 0.5 wt% ND loading. Furthermore, there was an increase in the thermal degradation temperature, melting temperature, and crystallization temperature.     

Mechanical and dynamical mechanical properties of chloroprene rubber and cellulose II composites

Vulcanized composites of chloroprene rubber (CR) with cellulose II (Cel II) as a filler were investigated. Cel II, obtained by the coagulation of cellulose xanthate, was incorporated in the rubber by the traditional method. The filler content varied from 0 to 30 phr. For comparison purposes, carbon black (CB)–CR composites were also studied. The CB amount varied from 0 to 45 phr. The mechanical and dynamic mechanical properties were determined, and the CR composite containing 20 phr of Cel II showed the best set of properties. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 2425–2430, 2004     

Preparation and properties of bacterial cellulose/graphene oxide composite films using dyeing method

In this study, bacterial cellulose (BC) hydrogels were cultured from a kombucha SCOBY starter. The scanning electron microscopy (SEM) results indicated that the dried BC exhibited an interpenetrating fibrous mat. The BC films harvested for 5, 10, and 15 days were 15–19, 14.4–24, and 30–31 μm thick, respectively. Then, BC/graphene oxide (GO) composite films were prepared via the exhaust dyeing method. GO sheets penetrated the BC matrix, resulting in the formation of a BC/GO composite, as revealed by the SEM analysis results. The mechanical properties of the composite films were investigated. Compared with virgin BC, the tensile strength of the composite films was higher, while the %E at break was lower, resulting in a significant increase in the Young's modulus. The X-ray diffraction results indicated that an increase in the dyeing time (0.5–2 h) gradually induced cellulose crystalline conformation, which in turn affected the swelling ability, mechanical properties, and electrical properties of the BC/GO composite films. After the reduction of GO to reduced GO (rGO), flexible conductive BC/rGO films were obtained, as confirmed by their resistivity values. Thus, flexible conductive composite films with excellent mechanical properties were successfully fabricated.     

Effects of rice straw fiber morphology and content on the mechanical and thermal properties of rice straw fiber‐high density polyethylene composites

Rice straw fiber‐high density polyethylene (HDPE) composites were prepared to investigate the effects of rice straw fiber morphology (rice straw refined fiber, rice straw pellet, rice straw strand), fiber content (20 and 40 wt %), and maleic anhydride polyethylene (MAPE) concentration (5 wt %) on the mechanical and thermal properties of the rice straw fiber‐HDPE composites in this study. Rice straw refined fiber exhibited more variability in length and width, and have a higher aspect ratio of 16.3. Compared to the composites filled of rice straw pellet, the composites made of the refined fiber and strand had a slightly higher tensile strength and lower tensile elongation at break. The tensile and flexural strength of the composites increased slightly with increasing rice straw fiber content up to 40 wt %, while the tensile elongation at break decreased. With addition MAPE, the composites filled with 20 wt % rice straw fiber showed an increase in tensile, flexural and impact strength and a decrease in tensile elongation at break. Differential scanning calorimetry showed that the fiber addition and morphology had no appreciable effect on the crystallization temperature of the composites but decreased the crystallinity. The scanning electron microscopy observation on the fracture surface of the composites indicated that introduction of MAPE to the system resulted in promotion in fiber dispersion, and an increase in interfacial bonding strength. Fiber breakage occurred significantly in the composites filled with refined fiber and strand after extruding and injection processing. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Preparation and characterization of composites of polyethylene with polypyrrole‐coated wollastonite

Composite sheets of polyethylene and polypyrrole‐coated wollastonite were prepared by extrusion and compression molding. Four compatibilizers were also evaluated, poly(ethylene‐co‐methyl acrylate) (EMA), maleated polyethylene (MAPE), poly(ethylene‐co‐vinyl alcohol) (EVOH), and poly(vinyl alcohol) (PVOH). The composite materials were characterized using X‐ray diffraction, thermogravimetric analysis, scanning electron microscopy (SEM), Raman spectroscopy, and mechanical properties determined by tensile tests. SEM micrographs showed that significantly improved interactions occurred between the PE matrix and polypyrrole‐coated wollastonite particles in the presence of EMA, MAPE, and EVOH. Raman spectroscopy confirmed that the polypyrrole coating on the wollastonite particles was not thermally degraded during melt processing. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Preparation of HDPE/SEBS‐g‐MAH and its effect on mechanical properties of HDPE/wood flour composites

In this article, high density polyethylene/styrene‐ethylene‐butylene‐styrene block copolymer blends (HDPE/SEBS) grafted by maleic anhydride (HDPE/SEBS‐g‐MAH), which is an effective compatibilizer for HDPE/wood flour composites was prepared by means of torque rheometer with different contents of maleic anhydride (MAH). The experimental results indicated that MAH indeed grafted on HDPE/SEBS by FTIR analysis and the torque increased with increasing the content of maleic anhydride and dicumyl peroxide (DCP). Styrene may increase the graft reaction rate of MAH and HDPE/SEBS. When HDPE/SEBS MAH was added to HDPE/wood flour composites, tensile strength and flexural strength of composites can reach 25.9 and 34.8 MPa in comparison of 16.5 and 23.8 MPa (without HDPE/SEBS‐g‐MAH), increasing by 157 and 146%, respectively. Due to incorporation of thermoplastic elastomer in HDPE/SEBS‐g‐MAH, the Notched Izod impact strength reached 5.08 kJ m^?2, increasing by 145% in comparison of system without compatibilizer. That HDPE/SEBS‐g‐MAH improved the compatibility was also conformed by dynamic mechanical measurement. Scanning electron micrographs provided evidence for strong adhesion between wood flour and HDPE matrix with addition of HDPE/SEBS‐g‐MAH. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

Physical wrapping of reduced graphene oxide sheets by polyethylene wax and its modification on the mechanical properties of polyethylene

A facile method to encapsulate the reduced graphene oxide (RGO) sheets physically with polyethylene (PE) wax was developed. The graphene oxide sheets were first wrapped with polyethylene wax, and reduced by hydrazine hydrate. The structure of the wrapped RGO was confirmed by means of Fourier transform infrared spectroscopy, X‐ray diffraction (XRD), and Raman spectroscopy. The PE wax‐wrapped RGO sheets were melt blended with PE to prepare PE/RGO nanocomposites. Transmission electron microscopy and XRD studies showed that this method could provide uniform dispersion of RGO sheets in the PE matrix. Scanning electron microscopy and Raman spectroscopy indicated that there was a strong interfacial interaction between the PE wax‐wrapped RGO sheets and PE matrix. Addition of 1 wt % RGO sheets in PE matrix led to a 48% increment in the yield stress and 118% increment in the Young's modulus, respectively. However, the elongation at break decreased with increasing RGO sheets loading content. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012