Thermoplastic Natural Rubber Research Articles

Mechanical properties and dynamic mechanical analysis of thermoplastic‐natural‐rubber‐reinforced short carbon fiber and kenaf fiber hybrid composites

AbstractThe hybridization of thermoplastic natural rubber based on carbon fiber (CF) and kenaf fiber (KF) was investigated for its mechanical and thermal properties. Hybrid composites were fabricated with a melt‐blending method in an internal mixer. Samples with overall fiber contents of 5, 10, 15, and 20 vol % were subjected to flexural testing, and samples with up to 30% fiber content were subjected to impact testing. For flexural testing, generally, the strength and modulus increased up to 15 vol % and then declined. However, for impact testing, higher fiber contents resulted in an increment in strength in both treated and untreated composites. Thermal analysis was carried out by means of dynamic mechanical analysis on composites with 15 vol % fiber content with fractions of CF to KF of 100/0, 70/30, 50/50, 30/70, and 0/100. Generally, the storage modulus, loss modulus, and tan δ for the untreated hybrid composite were more consistent and better than those of the treated hybrid composites. The glass‐transition temperature of the treated hybrid composite was slightly lower than that of the untreated composite, which indicated poor damping properties. A scanning electron micrograph of the fracture surface of the treated hybrid composite gave insight into the damping characteristics. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008

Essential Work of Fracture and Acoustic Emission Study on TPNR Composites Reinforced by Kenaf Fiber

Kenaf fiber (KF) based thermoplastic natural rubber (TPNR) composite was produced by melt blending with polypropylene (PP). Kenaf fiber (15% by volume) and TPNR were mixed in as Haake 600p internal mixer. The fracture behavior of the TPNR matrix and of TPNR—kenaf (with and without maleic anhydride grafted polypropylene, MAPP) composites was evaluated using the essential work of fracture (EWF) method and double edge notched tensile (DENT) specimens. Various ligament lengths were employed ranging from 4 to 12 mm. The strain rate was fixed at 2 mm/min. The specific work of fracture (we) and plastic work (βwp) showed the highest energy for TPNR that corresponds to its ductility and allows the application of the EWF approach. It was found that the presence of kenaf fibers and MAPP reduced the toughness of TPNR and changed the ductile fracture to brittle behavior. SEM observation revealed that energy absorption mechanisms include matrix deformation, fiber pullout, and fiber breakage. Acoustic emission (AE) was employed to analyze the failure processes further. The signals emitted by composites were substantially higher than that of the TPNR matrix, reflecting that also the failure mechanisms were affected by the fibers incorporated.

Mechanical and Fracture Toughness Behavior of TPNR Nanocomposites

Thermoplastic natural rubber (TPNR) nanocomposites containing organophilic layered silicates were prepared by melt blending method at 180°C using internal mixer (Haake 600P). The aim of this study is to determine the influence of the organoclay filler on the mechanical and fracture properties. In this study, two mixing methods were employed to incorporate filler into matrix, namely the direct (DM) and indirect (IDM) method. The mechanical properties of TPNR nanocomposites were studied using tensile, flexural, and impact tests. The tensile and flexural tests revealed that the optimum loading of organoclay was at 4 wt% using the indirect method of mixing. Plane stress fracture toughness of thermoplastic natural rubber (TPNR) nanocomposite was determined by the essential work of fracture (EWF) concept using tensile-loaded deeply double-edge notched (DDEN-T) specimens. The EWF measurements indicated that the specific essential work of fracture (we) decreased in the presence of nanoclay. Nevertheless, these TPNR nanocomposites met the basic requirement of the EWF concept of full ligament yielding, which was marked by a load drop in the force—displacement curves of the DDEN-T specimens.

Effect of Nickel–Cobalt–Zinc Ferrite Filler on Magnetic and Thermal Properties of Thermoplastic Natural Rubber Composites

A sample of Ni0.25Co0.25Zn0.5Fe2O4 ferrite was prepared by a double-staged sintering method in air. Thermoplastic natural rubber (TPNR) was prepared by melt blending of natural rubber (NR), liquid natural rubber (LNR), and high density polyethylene (HDPE) in an internal mixer Brabender Plasticorder PL 2000. Magnetic polymer composites were prepared from the ferrite and TPNR matrix using the same melt blending method at 135°C with mixing rate of 50 r.p.m. for 12 min. The fillers were varied from 5 to 30 weight percent. A uniform dispersion of the filler in the matrix was confirmed by thermogravimetric analysis (TGA). The density of the composites was determined using densitometer MD 200S. Magnetic properties were studied using a vibrating sample magnetometer (VSM) at room temperature (25°C). The results show that magnetization (M), saturation magnetization (MS), remanent magnetization (MR), initial susceptibility (χi) and initial permeability (μi) increase with increasing filler content at all compositions. The composites can be classified as soft magnetic materials as their coercivities are in the range of 30–36 Oe. The differential scanning calorimetric (DSC) results indicate that the glass transition temperature (Tg) and the melting point (Tm) of all the composites are independent of the filler content. The thermal conductivity of the composites was found to be in the range of 0.26 to 0.52 W m−1 K−1.

Composite of Aramid Fibre-Thermoplastic Natural Rubber: Effect of Processing Parameters and Compatibiliser

Composites have been prepared by melt blending thermoplastic natural rubber (TPNR) with aramid fibres in an internal mixer for various mixing times, at various temperatures and rotor speeds. The optimum processing parameters were 12 minutes, 155 °C and 50 rpm. The compatibilising effects of polyethylene-graft-maleic anhydride (PE-g-MA) on the composites were examined at concentrations from 0–14%. The tensile strength increased from 12.6 MPa to 15.7 MPa and modulus from 113 MPa to 136 MPa in the presence of 12% PE-g-MA. The impact strength also increased considerably. The compatibiliser also caused the storage modulus, E' to increase but a reduction in the tan delta peak. Scanning electron microscopy of the fractured surfaces revealed that strong interfaces were formed on addition of the compatibiliser.

Tensile and Impact Properties of Thermoplastic Natural Rubber Reinforced Short Glass Fiber and Empty Fruit Bunch Hybrid Composites

Thermoplastic natural rubber (TPNR) hybrid composite with short glass fiber (GF) and empty fruit bunch (EFB) fiber were prepared via the melt blending method using an internal mixer type Thermo Haake 600p. The TPNR were prepared from natural rubber (NR), liquid natural rubber (LNR) and polypropylene (PP) thermoplastic, with a ratio of 20:10:70. The hybrid composites were prepared at various ratios of GF/EFB with 20% volume fraction. Premixture was performed before the material was discharged into the machine. The study also focused on the effect of fiber (glass and EFB) treatment using silane and maleic anhydride grafted polypropylene (MAgPP) as a coupling agent. In general, composite that contains 10% EFB/10% glass fiber gave an optimum tensile and impact strength for treated and untreated hybrid composites. Tensile properties increase with addition of a coupling agent because of the existence of adherence as shown in the scanning electron microscopy (SEM) micrograph. Further addition of EFB exceeding 10% reduced the Young's modulus and impact strength. However, the hardness increases with the addition of EFB fiber for the untreated composite and decreases for the treated composite.

Effect of Extrusion Rate and Fiber Loading on Mechanical Properties of Twaron Fiber-thermoplastic Natural Rubber (TPNR) Composites

Mechanical behavior of short Twaron fiber thermoplastic natural rubber (TPNR) has been studied with respect to fiber loading and extrusion rates. The composites are prepared at two different compositions of NR/LLDPE matrixes i.e., 60/40 and 40/60. Twaron fibers are varied from 0 to 25% in the composites. The temperature profile for extrusion is 140, 145, 150, and 155°C for feeding zone, melting zone, mixing zone, and die respectively with the extrusion rate of 30, 50, 80, and 100 rpm. It has been found that the tensile strength, Young’s modulus, and impact strength increases with fiber loading, but the strain at break decreases. The optimum fiber loading in the system is found to be 20% in both blends. However, there is no effect of extrusion rate on the strength of composite observed.

Effect of Nickel-Cobalt-Zinc Ferrite Filler on Electrical and Mechanical Properties of Thermoplastic Natural Rubber Composites

ABSTRACT Thermoplastic natural rubber (TPNR) as polymer matrix was prepared by the melt blending method. Nickel-cobalt-zinc (NiCoZn) ferrite as a filler was prepared by the double-stage sintering method in air. The filler was incorporated in the polymer matrix using a Brabender internal mixer. The filler content was varied from 0 to 30 wt.%. The morphological study of the fractured surface using a scanning electron microscope (SEM) shows the effects of strain. The X-ray diffraction (XRD) indicates the coexistence of both the ferrite and thermoplastic. Electrical properties were studied using a high frequency response analyzer (HFRA) at room temperature (298°K). The results show that resistivity (ρ) decreases, but the dielectric constant increases, with increasing filler content. The resistivity and dielectric constant for all the composites are in the range of 8.9 × 106–9.7 × 105 Ωm and 33–72, respectively. A sharp change in both quantities around 15 wt.% filler content is interpreted as due to the transition from a dispersed system to an attached system. The tensile study shows that the elongation at break point and the tensile strength of the composite at room temperature decrease with increasing filler content. The hardness of the samples decreases with increasing filler content.

Effects of fiber composition andgraft-copoly(ethylene/maleic anhydride) on thermoplastic natural rubber composites reinforced by aramid fiber

Thermoplastic natural rubber (TPNR) composites of natural rubber and high-density polyethylene at a ratio of 70/30 were prepared by melt blending with aramid fibers using an internal mixer. The fiber loadings were varied from 0 to 30% for systems with and without graft-copoly(ethylene/maleic anhydride) (PE-g-MA) as a compatibilizer to study the variation of mechanical and dynamic mechanical properties. The tensile strength, modulus, hardness, and storage modulus improved with fiber loadings for both systems. The interaction between the matrix and fiber had also improved with the addition of PE-g-MA. Nevertheless, different behavior was observed in tan δ peak. The tan δ peak decreased with the increment of Twaron composition in the system with PE-g-MA and increased in the system without PE-g-MA. The results showed the importance of PE-g-MA in the system in improving the mechanical properties of Twaron–TPNR composite. POLYM. COMPOS., 27:395–401, 2006. © 2006 Society of Plastics Engineers

Rheological and thermal properties of thermoplastic natural rubbers based on poly(methyl methacrylate)/epoxidized‐natural‐rubber blends

AbstractEpoxidized natural rubbers (ENRs) with epoxide levels of 10, 20, 30, 40, and 50 mol % were prepared. The ENRs were later blended with poly(methyl methacrylate) (PMMA) with various blend formulations. The mixing torque of the blends was observed. The torque increased as the PMMA contents and epoxide molar percentage increased in the ENR molecules. Furthermore, the shear stress and shear viscosity of the polymer blends in the molten state increased as the ENR content and epoxide molar percentage increased in the ENR molecules. Chemical interactions between polar groups in the ENR and PMMA molecules might be the reason for the increases in the torque, shear stress, and viscosity. All the ENR/PMMA blends exhibited shear‐thinning behavior. This was observed as a decrease in the shear viscosity with an increase in the shear rate. The power‐law index of the blends decreased as the ENR contents and epoxide molar percentage increased in the ENR molecules. However, the consistency index (or zero shear viscosity) increased as the ENR contents and epoxide molar percentage increased. A two‐phase morphology was observed with scanning electron microscopy. The small domains of the minor components were dispersed in the major phase. For the determination of blend compatibility, two distinct glass‐transition‐temperature (Tg) peaks from the tan δ/temperature curves were found. Shifts in Tg to a higher temperature for the elastomeric phase and to a lower temperature for the PMMA phase were observed. Therefore, the ENR/PMMA blends could be described as partly miscible blends. According to the thermogravimetry results, the decomposition temperatures of the blends increased as the levels of ENR and the epoxide molar percentage increased. The chemical interactions between the different phases of the blends could be the reason for the increase. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 3561–3572, 2004

DYNAMICALLY VULCANIZED THERMOPLASTIC ELASTOMER BLENDS OF NATURAL RUBBER AND POLYPROPYLENE

Dynamic vulcanization of a soft grade of thermoplastic natural rubber (TPNR) was carried out using several concentrations of Hexamethylene N, N′ bis (tert-butyl peroxy carbamate) (HBTP). The blends were melt mixed in a Brabender plasticorder. The effectiveness of dynamic vulcanization was investigated using the Brabender plastograms, swelling index measurements, rheological behavior by means of a capillary rheometer, dynamic mechanical properties, and tensile testing. It was found that varying the HBTP concentration had a great influence on the rheological behavior as well as the dynamic and tensile properties of the material. The increase of HBTP dosage resulted in an increase of the extent of crosslinking and caused an increase of the elastic modulus and a reduction of the loss modulus. The ultimate tensile strength and elongation at break also increased with increasing HBTP loading. The rheograms indicated that the blends exhibit a pseudoplastic behavior.

Effect of mape on the mechanical properties of rubber wood fiber/thermoplastic natural rubber composites

AbstractRubber wood fiber/reinforced thermoplastic natural rubber (RWF/TPNR) composites were prepared. A blend of natural rubber with high‐density polyethylene was prepared by melt blending the materials in the internal mixer of Brabender Plasticorder machine. RWF and TPNR were mixed with different fractions of fiber (0, 5, 10, 20, and 30%) in the internal mixer. To investigate the influence of coupling agent on the mechanical properties, concentrations of maleic anhydride polyethylene (MAPE) were employed in the composites. The mechanical properties and morphology of composite material were characterized with tensile machine and scanning electron microscope, respectively. The results showed that the addition of MAPE has a positive effect on the tensile strength and Young's modulus while the maximum strain was reduced. SEM micrographs showed good adhesion between RWF and TPNR when the coupling agent was applied. © 2004 Wiley Periodicals, Inc. Adv Polym Techn 23: 18–23, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/adv.10070

Mechanical Properties of Kenaf–Thermoplastic Natural Rubber Composites

Kenaf–thermoplastic natural rubber (Kenaf–TPNR) composites were developed and evaluated in this study. The kenaf was blended with TPNR and maleic anhydride-grafted polypropylene (MAPP) as a compatibilizer in an internal mixer (Brabender). The mechanical properties of the composites were investigated by tensile, impact, flexural, and morphologic properties by scanning electron microscope (SEM). The incorporation of the kenaf fiber into the TPNR matrix resulted in an improvement in the tensile strength and Young's modulus. However, the maximum strain and impact strength decreased with increased filler loading. The better performance was attributed to the addition of MAPP due to improvements in the wetting of the filler surface. The addition of MAPP produced composites with improved tensile strength, Young's modulus, and flexural stiffness. SEM was employed to investigate the fiber surface, fiber pullout, and fiber–matrix interaction of composites.

Performance of Rubberwood Fiber–Thermoplastic Natural Rubber Composites

Rubberwood fiber–thermoplastic natural rubber (RWF–TPNR) composites were prepared and evaluated in this study. The RWFs were supplied in the form of thermomechanical pulp (TMP) from the Hume Fiberbord Company in Malaysia. The fibers were screened to 0.5–1 mm sizes and blended with TPNR and maleic anhydride–grafted polypropylene (MAPP) as a compatibilizer in the internal mixer of Brabender Plasticorder machine. The mechanical, thermal properties and morphology of the composites were investigated by tensile, impact, flexural, thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), and scanning electron microscope (SEM). The results showed that the tensile strength and Young's modulus increased, while tensile strain and impact strength decreased with increasing of fiber loading. Thermogravimetric analysis showed an increasing degradation temperature of the samples with RWF. On the other hand, SEM micrographs showed good adherence between fibers and matrix with the presence of MAPP.

Effects of Natural Rubber on Microwave Absorption Characteristics of Some Li–Ni–Zn Ferrite–Thermoplastic Natural Rubber Composites

A microwave (Li0.5Fe0.5)0.4Ni0.3Zn0.3Fe2O4 (LNZ) ferrite was prepared by a conventional sintering method in air. Thermoplastic natural rubber (TPNR) was prepared from polypropylene (PP) and natural rubber (NR) in the ratios of 80:20, 70:30, 60:40, 50:50 and 40:60 with liquid natural rubber as a compatibilizer by a melt blending technique. LNZ ferrite-TPNR composites with 20 wt% ferrite filler were prepared using a Brabender plasticorder internal mixer. The microwave electromagnetic properties of the composites were studied in the frequency range of 0.3–13.5 GHz using a microwave vector network analyzer (MVNA). The real and imaginary components of the relative complex dielectric permittivity (εr*=εr′-jεr′′) and magnetic permeability (µr*=µr′-jµr′′) were calculated from the measured complex scattering parameters (S11* and S12*) using the Nicolson–Ross model. The dielectric and magnetic properties were found to depend on the NR and PP content in the composites. The minimum reflection loss (RL) under the matching conditions increases with increasing NR content.

Electromagnetic and absorption properties of some microwave absorbers

Electromagnetic properties of a thermoplastic natural rubber (TPNR), a lithium–nickel–zinc (Li–Ni–Zn) ferrite and a TPNR–ferrite composite subjected to transverse electromagnetic (TEM) wave propagation were investigated. The incorporation of the ferrite into the matrix of the TPNR was found to reduce the dielectric loss but the magnetic loss increased. The absorption characteristics of all the samples subjected to a normal incidence of TEM wave were investigated based on a model of a single-layered plane wave absorber backed by a perfect conductor. It is evident from a computer simulation that the ferrite is a narrowband absorber, whereas the polymeric samples show broadband absorption characteristics. Minimal reflection of the microwave power or matching condition occurs when the thickness of the absorbers approximates an odd number multiple of a quarter of the propagating wavelength. This is discussed as due to cancellation of the incident and reflected waves at the surface of the absorbers. The Li–Ni–Zn ferrite exhibits another matching condition at low frequency when the magnitude of the complex relative dielectric permittivity (εr*) equals that of the complex relative magnetic permeability (μr*). The specular absorber method provides a simple theoretical graphic aid for determining the absorption characteristics and the location of the matching conditions in the frequency domain. The result for the ferrite sample was tested and confirmed directly from terminated one-port measurements.

Effects of processing parameters and graft-copoly(propylene/maleic anhydride) on mechanical properties of thermoplastic natural rubber composites reinforced with wood fibres

Composites have been prepared by melt blending thermoplastic natural rubber (TPNR) with wood fibre in a Plasticorder mixer at various mixing temperatures, rates of rotation, and mixing times. The TPNR was a blend of polypropylene, natural rubber, and liquid natural rubber at a PP/NR/LNR ratio of 60:30:10,which was compounded using an internal mixer.Composites containing wood fibre fractions of 0, 10, 20, and 30 wt-%, and graft-copoly(propylene/maleic anhydride) (MAPP) at concentrations from 0 to 10% were subjected to tensile tests. The compatibiliser increased the tensile strength and Young's modulus, but reduced the strain. Scanning electron microscopy of the fracture surfaces revealed that strong interfaces were formed on addition of MAPP.

Thermal performance of thermoplastic natural rubber solar collector

The paper presents the thermal performance of a solar collector with TPNR (thermoplastic natural rubber) tubing as the absorber plate. A commercial blend of TPNR (dynamically vulcanised natural rubber—DVNR 9011) was used as the absorber plate which was of the parallel type and satisfies the test conditions indicated by the standard GB 4271-84. The values of the thermal performance parameters F R( τα) and F R U L were 0.72 and 9.67, respectively. A domestic hot water thermosyphon solar collector system with a vertical tank was used for performance monitoring. The thermosyphon hot water system is capable of producing temperature output up to 65 °C for a typical day of 550 W/m 2. For monitoring purposes, two methods were used. In the first method, the storage tank was filled up with water the night before the test and the temperature readings were recorded for the next day’s test. The end-of-the-day temperature rise in the storage tank and the accumulated total solar radiation values were also noted over the same period. The test were repeated under varied environmental conditions that covers low and high radiation intensities. A temperature rise of 15 °C in the storage tank was obtained for this system at an accumulated solar radiation of 4.5 kW h/m 2. In the second method, the temperature readings without draw-off or draining of the hot water from the storage tank were recorded for 6 days and a temperature of more than 60 °C can be achieved by the storage tank. Hence, this system has the potential to be used as domestic thermosyphon hot water system.

Radiation crosslinked thermoplastics natural rubber (TPNR) foams

Thermoplastic natural rubber is gaining wider interest and like other thermoplastic elastomers, offers the processibility of thermoplastic as well as functional performances and properties of conventional thermoset rubbers. This paper describes an evaluation made of the suitability of foaming blends of natural rubber and EVA using chemical blowing agents. Crosslinking was achieved by exposing the TPNR to electron beam irradiation (EB) at 20, 30, 40, 60, 80, 100, 120, 150 and 200 kGy doses. The relationships between foam density and concentration of blowing agent as well as foaming parameters such as time and temperature were evaluated.

Mathematical modelling of thermoplastic natural rubber melt flow in a double feed extrusion system

A mathematical model for investigating the melt flow behaviour of thermoplastic natural rubber (TPNR) in a double feed system of a single-screw reciprocating injection unit using a specially written software is presented. The model enabled the prediction of processing parameters in the feed and main extruders, from which the optimum conditions for processing TPNR were obtained. The introduction of the double feed system also contributed to better mixing in the main extruder.