Thermoplastic Blends Research Articles

A review of thermoplastic composites for bipolar plate applications

SUMMARY Bipolar plates are responsible for functions of vital importance to the long-term performance of fuel cells. They play crucial roles in water and gas management, mechanical strength and electrical conductivity. It also significantly contributes to the volume, weight and cost of fuel cell stacks. The properties of bipolar plates are affected by the materials and processes used in the manufacturing of the plates. The objective of this article is to review the use of thermoplastic materials as polymer matrices in bipolar plate applications. Conductive composites consisting of different types and blends of thermoplastic polymers are detailed discussed. The effects of filler types and processing conditions are given. Several thermoplastic blends consisting of carbon black, carbon nanotube and graphite are evaluated. The dispersion of conductive fillers, in particular, polymer composites and polymer blend composites is also given. Copyright © 2013 John Wiley & Sons, Ltd.

Thermoplastic vulcanizates from post consumer computer plastics/nitrile rubber blends by dynamic vulcanization

Due to depletion of natural resources and increasing greenhouse emissions, new technologies for the transformation of waste polymers into valuable materials represent one of our greatest current needs. Acrylonitrile–butadiene–styrene terpolymer (ABS) is one of the most widely used engineering plastics and is used as outer casing for electronic equipment. Nitrile rubber (NBR) is used in many applications that demand oil resistance. In an attempt to explore whether these materials can be successfully recycled, we prepared blends of scrap computer plastics (SCP) based on ABS with NBR and waste NBR powder (w-NBR), and investigated their mechanical properties and recyclability. Specifically, we assessed the effect of dynamic vulcanization and replacement of virgin NBR with w-NBR on the properties of 60/40, 70/30, and 80/20 NBR/SCP blends. These blends exhibited thermoplastic elastomeric behavior. The thermoplastic elastomeric blends showed excellent swelling resistance to standard lubricant oil (namely, IRM 903 oil).

Super toughening of the poly(l-lactide)/thermoplastic polyurethane blends by carbon nanotubes

Carbon nanotubes (CNTs) were introduced into the poly(L-lactide)/thermoplastic polyurethane (PLLA/TPU) blend to prepare the ternary nanocomposites. The results showed that CNTs selectively localized in the TPU phase, leading to a morphological change from the sea-island morphology to the quasi-cocontinuous morphology. The high content of the CNTs induced the formation of the percolated network structure. Consequently, super toughened PLLA/TPU/CNTs nanocomposites were prepared successfully. More apparent cavitation of the TPU phase and the intensified local plastic deformation of the PLLA matrix under the impact load were observed on the impact-fractured surface of the ternary nanocomposites. This was believed to be the main toughening mechanisms for the ternary nanocomposites. After being annealed, besides the morphological change of the nanocomposites, PLLA matrix also exhibited a large number of crystalline structures. Furthermore, the impact toughness of the ternary nanocomposites was enhanced further.

Study the Effect of Recycled Tire Rubber on the Mechanical and Rheological Properties of TPV (HDPE/Recycled Tire Rubber)

Thermoplastic elastomeric blends prepared from blending of (10%, 20%, 30%, 40% and 50 wt%) high density polyethylene(HDPE) and (10%, 20%, 30%, 40% and 50 wt%) ground rubber tire (TPV-R). The blends prepared contain (HDPE)/polybutadiene (TPV-V). The two blends were successfully prepared through a dynamic vulcanization process, involving dicumyl peroxide (3%) as vulcanizing agent. The data of the mechanical (tensile strength at yield, %elongation and young modulus) and rheological properties (shear stress, shear rate, viscosity, flow behavior index and activation energy of melt flow) of the TPV-V and TPV-R showed that there was comparable results between the two blends.

Effect of an organoclay on the reaction-induced phase-separation in a dynamically asymmetric epoxy/PCL system

The addition of layered silicates can significantly affect the phase behaviour of both immiscible thermoplastic blends and partially miscible thermoset systems that undergo reaction-induced phase separation (RIPS) during curing. This study focuses on the phase behaviour of polycaprolactone (PCL)/epoxy in the presence of organically modified montmoril- lonite (oMMT). Due to the high dynamic asymmetry caused by the differences in the molecular weights and viscosities of the PCL and the uncured epoxy, the critical point is localised at low PCL concentrations, as indicated by the pseudophase diagram. The addition of oMMT to the system led to the marked shift of the critical point towards higher concentrations of PCL, with an increase in the oMMT content occurring as a consequence of the preferential localisation of the clay in the epoxy phase, making this phase more dynamically slow. Significant changes in morphology, including phase inversion of the PCL/epoxy systems caused by the presence of oMMT, were recorded for PCL concentrations ranging from 10 to 30%.

Effect of organomodified montmorillonite concentration on tensile and flow properties of low-density polyethylene–thermoplastic corn starch blends

In this study, low-density polyethylene (LDPE)–thermoplastic corn starch blends containing various amounts of organomodified montmorillonite (OMMT, 0.5–3 part per hundred (phr) resins) were prepared using a twin screw extruder. A 3-wt% LDPE-grafted maleic anhydride was used as a compatibilizer. The tensile, flow and water absorption properties of all the samples were measured by means of standard methods. Intercalated structures were achieved in all the samples, based on the x-ray diffraction and transmission electron microscopic results. Increasing levels of clay also led to the higher gallery distance of silicate layers (i.e. 32.5–34.5 Å). Furthermore, increment in ultimate tensile strength (UTS) and Young’s modulus ( E) as well as decrement in elongation at break ( ∊b) were obtained with increase in clay loading. The sample containing 1 phr nanoparticles showed 20% and 63% increase in UTS and E when compared with the reference sample, respectively. However, ∊b of this sample decreased by 17%. In addition, the flow property measurements indicated that as shear rate and the clay content increased, the apparent viscosity of all the samples decreased and increased, respectively. Finally, the presence of OMMT led to decrease in the melt flow index (MFI) of the samples. The MFI values also decreased with increasing the OMMT concentration. It is believed that the samples prepared in this work may biodegrade after exposure to the environment.

Multivariate Analysis of Micro-Raman Spectra of Thermoplastic Polyurethane Blends Using Principal Component Analysis and Principal Component Regression

Probing the specific hydrogen-bonding behavior of thermoplastic polyurethane (TPU) blends using vibrational spectroscopies remains the sin qua non for understanding the link between hydrogen-bonding and phase-segregation behavior. However, current literature holds to more traditional univariate approaches when studying the morphologically interesting normal molecular vibrations of TPUs. In the present study, multivariate analysis, including principal component analysis (PCA) and principal component regression (PCR), is used to scrutinize the relevant Raman bands acquired from a binary mixture of analogous TPU copolymer blends. Considering the near identical behavior of selected spectral regions, PCA was capable of isolating linear and nonlinear composition-dependent trends on PC-scores plots. From here, the PC scores, extracted from wavelengths comprising the carbonyl stretching region (1681-1764 cm(-1)), CH(2) deformations (1380-1500 cm(-1)), aromatic stretch from the hard segment (1617 cm(-1)), and amide II mixed band (1540 cm(-1)), were used to explicitly predict the mole fraction of hard segment present in each blend using PCR. Spectral preprocessing, wavelength selection, and variable scaling were major factors in PCR accurately predicting the weight fraction of each copolymer in spite of the clearly evident, blend-specific spectroscopic behavior.

Bio-based materials for high-end electronics applications

During the past decade, a shift of focus onto greener alternatives to petroleum-based plastics has spurred the development of bio-based resins for plastic development. This has led to a positive marketing image for companies making the switch to resins from renewable resources. This shift of focus is further reinforced by corporations, which are committed to a reduction in their greenhouse gas emissions and product environmental footprints. Here, we present a perspective on the use of renewable materials in durable goods applications and the challenges and advantages associated with the use of renewable materials. Replacement of petroleum-based acoustic foam with that derived from sustainable resources and qualification of thermoplastic polylactic acid blends for enclosure covers has been demonstrated. The technical details of the materials development required for use in durable goods, and their characterization is also discussed.

Modelling of the Formation of Gradient Dispersed Structures in Blends of Thermoplastics and Thermosetting Plastics

The results of investigating the phase structure of the diffusion zones formed during the dissolution of particles and films of thermoplastics in a thermosetting matrix and their curing are set out. Concentration distribution profiles are plotted, diffusion coefficients are calculated, and micrographs of the phase structure of the diffusion zone during the chemical reaction of curing are obtained.

The effect of γ‐Irradiation and reactive extrusion on the structure and properties of polycarbonate and starch blends: A work oriented to the recycling of thermoplastic wastes

AbstractPolymer materials with improved properties can be obtained through polymer blends. As a polymer mixture is generally immiscible and incompatible, it is necessary to develop new methods to improve the interfacial adhesion. In this study, polycarbonate‐based extruded thermoplastic were developed by blending polycarbonate with thermoplastic starch using extensive process engineering based on structure–property correlations. Starch was destructurized and plasticized followed by melt‐blending with polycarbonate. The optimal conditions for processing of the thermoplastics blends were found to be 230°C, 2 min of processing time, and 3–6 wt % of glycerol. The effect of γ‐irradiation on the fabrication of the blend was studied. Changes in structure, morphology, and properties resulting from γ‐exposure in the range 0–150 kGy were investigated. Electron spin resonance results revealed that numerous radicals remained trapped in the materials after irradiation even after a long time enabling reactions between starch and polycarbonate. Results obtained from tensile test, differential scanning calorimetry, and dynamic mechanical analysis revealed the relatively good affinity between the two components after blending in a micro‐extruder. Irradiated blends are thermally more stable than those non‐irradiated. Mechanical tests also showed that the efficiency of the irradiation depended greatly on the dose applied to the initial materials. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013

Sustainable bioderived polymeric materials and thermoplastic blends made from floating aquatic macrophytes such as “duckweed”

AbstractWhile plastics offer many conveniences to modern consumers, they represent unsustainable practices that hinder economic growth and environmental stability. Therefore, the production of biodegradable plastic from alternative feedstocks is investigated to replace conventional plastics in packaging and short‐term use markets. Duckweed represents a feedstock that elicits high biomass productivity, plus a wastewater remediation potential. To establish duckweed's potential for plastic production this study investigates the stability and thermal characteristics of plasticized and blended duckweed polymers. Duckweed biomass milled to 250 μm was plasticized using glycerol and compression molded into plastic samples. Results indicated a 3 : 1 ratio of duckweed to glycerol produced the best polymer stability. This ratio was then used to develop blends which demonstrated dispersion in biobased or polyethylene (PE) phase, except for 50% Biobased/50% PE where phase continuity was observed. Furthermore, surface morphology indicated limited homogeneity in blends and increased PE was correlated to temperature stability of biobased phase. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci. 2013

Wplyw nanonapelniacza polimerowego o budowie rdzen-otoczka na strukture oraz wlasciwosci mieszaniny polilaktydu i termoplastycznej skrobi kukurydzianej

Wplyw nanonapelniacza polimerowego o budowie rdzen-otoczka na strukture oraz wlasciwosci mieszaniny polilaktydu i termoplastycznej skrobi kukurydzianej

Rheological and morphological properties of reactively compatibilized thermoplastic olefin (TPO) blends

Thermoplastic olefin blends of polypropylene (PP) and ethylene octene copolymers (EC) were reactively compatibilized by means of functional reactive compounds capable of forming copolymers at the interface. For this purpose, amine functional groups were first incorporated into a PP in a solution reaction. The aminated PP was then used as the reactive compatibilizer during melt mixing. Linear viscoelastic measurements showed that the compatibilized blends feature the characteristics of materials in the sol–gel transition, with a power-law behavior for the dynamic moduli at low frequencies. The gel-like behavior was more pronounced in the blend with a high level of compatibilizer (10 wt. %). At high frequencies, however, the dynamic properties of all the blends investigated (compatibilized and noncompatibilized) were identical, suggesting that the bulk properties of the blends were not changed by the reactive compatibilization. The presence of a network structure was also confirmed by microscopic observations. A large transient viscosity with a significant and broad overshoot was observed for the compatibilized blends at low shear rate. In addition, the stress of the compatibilized blends relaxed over a much longer time as compared to the noncompatibilized system. The ability of different linear viscoelastic models in predicting the linear viscoelastic behavior of the compatibilized blends was also examined.

Preparation of modified starch‐grafted poly(lactic acid) and a study on compatibilizing efficacy of the copolymers in poly(lactic acid)/thermoplastic starch blends

AbstractThis study has concerned preparation of polylactic acid grafted with maleated thermoplastic starch (PLA‐g‐MTPS) and a study on compatibilizing efficacy of the above copolymers in PLA/thermoplastic starch (TPS) blends. The PLA‐g‐MTPS copolymers were prepared by two‐step reaction. First, maleated thermoplastic starch (MTPS) was prepared by reacting cassava starch with glycerol and maleic anhydride (MA). Second, the MTPS was grafted onto PLA molecules using peroxide as an initiator. Chemical structures of the products were characterized by using Fourier transform infrared spectroscopy and 1H‐NMR techniques, whereas the acid numbers of the copolymers were determined by titration. Thermal characteristic of the copolymer was also characterized by using dynamic mechanical thermal analysis. In total, 5 wt % of the graft copolymer was blended with PLA and TPS in a twin screw extruder. Mechanical, rheological, and morphological properties of the blends were evaluated via tensile test, melt flow index test, and scanning electron microscopy, respectively. It was found that mechanical properties of the blends depended on starch content and type of the PLA‐g‐MTPS. When the PLA‐g‐MTPS was prepared at low amount (0.25 pph) of peroxide, the mechanical properties of the blend was improved remarkably as compared to those of the normal blend and/or the blend containing different compatibilizers. Compatibilizing efficacy of the above copolymers became more obvious when the thermoplastic starch (TPS) blending ratio was increased. The above results were ascribed in the light of change in the viscosity and morphology of the blends. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012

EFFECT OF MALEIC ANHYDRIDE ON KENAF DUST FILLED POLYCAPROLACTONE/THERMOPLASTIC SAGO STARCH COMPOSITES

The utilization of biodegradable polymers for various applications has been restricted mainly by its high cost. This report aims to study the water absorption and mechanical properties of kenaf dust-filled polycaprolactone/thermoplastic sago starch biodegradable composites as a function of filler loading and treatment with maleic anhydride. While water absorption in untreated biocomposites increased as a function of filler loading, treated biocomposites resulted in weight loss, whereby low molecular weight substances were dissolved into the aging medium. The kenaf dust imparts reinforcing effects on the biocomposites, resulting in improved mechanical properties. This is further attested by morphological studies in which kenaf dust was well dispersed in the polycaprolactone/ thermoplastic sago starch blend matrix. The addition of maleic anhydride into the polycaprolactone/thermoplastic sago starch blend resulted in a homogeneous mixture. At low filler loading, strain at break of the maleated polycaprolactone/thermoplastic sago starch blend increased at the expense of tensile strength and modulus. This is most likely due to the excessive dicumyl peroxide content, which caused chain scission of the polycaprolactone backbone. Tensile strength and modulus improved only when high filler loading was employed.

Thermoplastic starch blends: A review of recent works

The aim of this review is to discuss the recent developments in thermoplastic starch blends. Starch has been considered as an excellent candidate to partially substitute synthetic polymer in packaging, agricultural mulch and other low-cost applications. Recently, the starch granules were plasticized using different plasticizers under heating and shearing, giving rise to a continues phase in the form of a viscous melt which can be processed using traditional plastic processing techniques, such as injection molding and extrusion. This kind of starch composites is called thermoplastic starch. Unfortunately, thermoplastic starch presents some drawbacks, such as low degradation temperatures, which make it difficult to process, poor mechanical properties and high water susceptibility. Much work has been carried out to overcome these drawbacks, including the combination of thermoplastic starch with other polymers, aiming at lowering the cost and enhancing the biodegradability of the final product.

Dynamically Vulcanized Cis-1,3-Butadiene Rubber/Ethylene-Vinyl Acetate Copolymer/High- Impact Polystyrene Blends Compatibilized by Styrene-Butadiene-Styrene Block Copolymer

Compatibilized Cis-1,3-butadiene rubber (BR)/ethylene-vinyl acetate copolymer (EVA)/high-impact polystyrene (HIPS) thermoplastic blend vulcanizates (TPVs) were prepared by dynamic vulcanization, with TPVs being compatibilized by styrene-butadiene-styrene (SBS) block copolymer. The effects of SBS compatibilizer on mechanical, dynamic mechanical, and morphological properties of TPVs were investigated systematically. Experimental results indicated that the dynamically vulcanized BR/HIPS blends did not show an elastomeric behavior when the BR/HIPS blend ratio ranged from 30:70 to 70:30. However, the dynamically vulcanized BR/EVA/HIPS blends compatibilized with SBS showed obvious elastomeric behavior; thus SBS had a good compatibilization effect on BR/EVA/HIPS TPVs. The fractured surface morphology of compatibilized BR/EVA/HIPS TPV was relatively smooth, the interface interaction was strong, and there was no obvious micro-phase separation. BR particles were dispersed evenly in the etched surfaces of BR/EVA/SBS/HIPS TPV. A rubber process analyzer revealed that the storage modulus decreased significantly with increasing strain and the incorporation of compatibilizer SBS in TPVs weakened the Payne effect; the loss modulus showed a pronounced peak and tanδ increased continuously with increasing strain.

Thermoplastic elastomers-based natural rubber and thermoplastic polyurethane blends

Thermoplastic elastomers based on the blends of thermoplastic polyurethane (TPU) and natural rubber were prepared by a simple blend technique. The influence of the two different types of natural rubber (i.e., unmodified natural rubber (NR) and epoxidized natural rubber (ENR)) on properties of the blends was investigated. The main aim of this study was to improve heat resistance and damping properties, and also to prepare the TPU material with low hardness by blending with various amounts of natural rubber. It was found that the TPU/ENR blends exhibited superior modulus, hardness, shear viscosity, stress relaxation behavior and heat-resistant properties compared to the blends with TPU and unmodified NR. This was attributed to higher chemical interaction between the polar functional groups of ENR and TPU by improving the interfacial adhesion. It was also found that the ENR/TPU blends exhibited finer grain morphology than the blends with unmodified NR. Furthermore, lower tension set, damping factor (Tan δ) and hardness, but higher degradation temperature, were observed in natural rubber/TPU blends compared to pure TPU. This proves the formation of TPU material with high heat resistance, low hardness and better damping properties. However, the blends with higher proportion of natural rubber exhibited lower tensile strength and elongation at break.

Preparation and studying properties of polybutene‐1/thermoplastic starch blends

AbstractStarch as an inexpensive and renewable source has been used as a filler for environmental friendly plastics for about two decades. In this study, glycerol was used as a plasticizer for starch to enhance the dispersion and the interfacial affinity in thermoplastic starch (TPS)/polybutene‐1(PB‐1) blend. PB‐1 was melt blended with TPS using a single screw extrusion process and molded using injection molding process to investigate the rheological and mechanical properties of these blends. Rheological properties were studied using a capillary rheometer, and the Bagley's correction was performed. Mechanical analysis (stress–strain curves) was performed using Testometric M350‐10 kN. The rheological properties showed that the melt viscosity of the blend is less than that of PB‐1, and the flow activation energy at a constant shear stress of the blend increases with increasing glycerol content in the blend. The mechanical experiments showed that both stress and strain at break of the blends are less than that of PB‐1, whereas the Young's modulus of the most blends is higher than that of PB‐1 which confirms the filling role of TPS in the blend. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012

Optimization of tensile properties thermoplastic blends from soy and biodegradable polyesters: Taguchi design of experiments approach

Soy meal-based biodegradable blends were prepared by melt extrusion process. The effects of denaturants, i.e., urea and sodium sulfite and plasticizer (glycerol) and polyester type (polybutylene succinate, polycaprolactone, polybutylene adipate terephthalate) on tensile strength and elongation at break were investigated using a Taguchi experimental design approach. The results showed that the sodium sulfite had little or no effect on final properties of the blends. Also, biodegradable polyester type had significant effect on the tensile strength and elongation at break of the blends prepared. The predicted values and experimental were found to be in tune with each other. The chemical structure and morphology of the optimum sample was probed by FT-IR spectroscopy and scanning electron microscopy (SEM). Also, the results provided an insight into how important the plasticization and destructurization of soy protein to obtain the blends with desired mechanical properties.