Processing Of Polymer Composites Research Articles

Developments of Graphene-based Polymer Composites Processing Based on Novel Methods for Innovative Applications in Newborn Technologies

Graphene has been used in industrial application according to its unique properties especially to prepare graphene-based composites. Because of combining characterization of both materials in these composites, they would exhibit significant improvement in structural performance and multifunctional properties. Herein, we review various assembly methods for incorporating graphene filler to polymer matrix in order to achieve the best performance and properties by using the lowest amount of filler as much as possible. In addition, the effect of these techniques to enhance dispersion of garphene in different polymer matrix is investigated to get optimum of filler amount, plus exploring application of graphene-based composites in variety of fields such as electronic devices, sensors and even biomedical concerns is mentioned by this review.

Sea coral-derived cuttlebone reinforced epoxy composites: Characterization and tensile properties evaluation with mathematical models

Using sea coral as a new bio-mass in processing of particle-filled polymer composites is very promising in the field of structural applications. In this study, waste cuttlebone was used as a filler material in epoxy composites. In general, cuttlebone particles derived from crushing and sieving were in aragonite polymorph form. In the present study, calcite polymorph form was obtained after heat treatment of cuttlebone particles at 400℃. Presence of polymorph form, elemental composition and thermal stability were confirmed with different characterization techniques. Composites were prepared with aragonite and calcite polymorph form cuttlebone particles and commercially available calcium carbonate as reinforcement in epoxy matrix. Tensile tests were carried out to determine the composites strength and compared with predefined theoretical models. Heat-treated cuttlebone reinforced epoxy composites showed higher tensile properties and better interaction between filler and matrix than other composites.

Effects of Daniella oliveri Wood Flour Characteristics on the Processing and Functional Properties of Wood Polymer Composites

The effects of particle sizes/distribution and contents on the processing, changes in microstructure and functional properties of wood polymer composites (WPCs) prepared from virgin high-density polyethylene (vHDPE) and sodium hydroxide (NaOH) treated Daniella oliveri wood flour via compression molding have been explored. Findings from this study suggested that an appropriate choice of wood flour characteristics could improve the interactions between the wood flour and the vHDPE matrix by eliminating incomplete wetting, segregation, and agglomeration of wood flour particles during processing while enhancing mechanical and thermal properties of the composites. Properties of the WPCs were optimized when wood flour of particle sizes/distribution and contents of +210–300 µm and 35 wt%, respectively, were blended with vHDPE matrix.

Investigating thiol-epoxy composites for semiconductor die attach adhesives

ABSTRACTIn this study, thiol-epoxy polymer composites are explored as candidates for high-temperature die attach applications. We present a polymer composite processing technique for die attach adhesives with low cure-stress. Lap shear samples of both a polymer adhesive and current industry adhesives were subjected to tensile testing and die shear strength was compared. At 260 °C, the candidate polymer adhesive exhibited a die shear strength of 0.500 MPa in comparison with 1.35 MPa and 0.258 MPa for two control adhesives. While samples showed less variation in properties in die shear strength between room temperature and 260 °C, the absolute die shear strength values were inferior to commercial adhesives at both room and elevated temperatures. We hypothesize that low cure stress networks, such as the thiol-epoxies presented, provide a compelling choice to engineer new die attach adhesives, but realize that further network refining is needed including the addition of adhesion promoters and other additives, a task better suited to industrial research with a focus in properties optimization.

Simultaneous electrical and rheological measurements on melts of conductive polymer composites under elongation

The structure development in conductive polymer composites during deformation is a topic of great interest as the structure of conductive particle pathways governs electrical properties of the composite. In this paper simultaneous electrical and rheological measurements in elongation are introduced for the first time using a modified Münstedt tensile rheometer. Such kind of experiment can help in understanding the relationships between processing and properties of conductive polymer composites. The first results presented were obtained on polystyrene containing 4 vol.% of carbon black at the temperature of 150 °C. Similar to the shear, the conductivity development under elongation is given by a competition of flow-induced destruction and build-up of particle structures and it is considerably influenced by the strain rate applied.

Low-temperature baroplastic processing of graphene-based polymer composites by pressure-induced flow

Two-stage emulsion polymerization was employed to synthesize nanoparticles consisting of a low glass transition temperature core of poly(n-butyl acrylate) (PBA) and a glassy poly(methyl methylacrylate) (PMMA) shell. Incorporation of graphene oxide (GO) into the PBA-PMMA latex produced GO/PBA-PMMA composites after demulsification and graphene/PBA-PMMA composites after chemical reduction of GO. The as-prepared powdery materials were processed into thin films by compression molding at room temperature as the result of a pressure-induced mixing mechanism of microphase-separated baroplastics. The presence of oxygen-containing groups for GO sheets contributed to better dispersion and stronger interface with the matrix, thereby showing greater reinforcement efficiency toward polymers compared to graphene sheets. In addition, both Young's modulus and yield strength for all materials increased with applied pressure and processing time due to better flowability, processability and cohesion at higher pressure and longer time. Low-temperature processing under pressure is of significance for energy conservation, recyclability and environmental protection during plastic processing.

Numerical simulation and design optimisation of an integrally-heated tool for composite manufacturing

Tooling design is crucial for the production of cost-effective and durable composite products. As part of the current search for cost reduction, integrally-heated tooling is one of the technologies available for ‘out-of-autoclave’ processing of advanced thermoset polymer composites. Despite their advantages, integrally-heated tools can suffer from uneven distribution of temperature, variability in heat flow rate and inconsistency in heating/cooling time. This research, therefore, investigates a number of design variables such as shape and layout of heating channels in order to improve the thermal performance of an integrally-heated tool. Design of Experiments (DoE) has been carried out using Taguchi’s Orthogonal Array (OA) method to set several combinations of design parameters. Each of these design combinations has been evaluated through numerical simulation to investigate heating time and mould surface temperature variation. The simulation results suggest that the layout of the channels and their separation play a vital role in the thermal performance. Signal-to-Noise (S/N) ratio and analysis of variance (ANOVA) have been applied to the results obtained to identify the optimal design combination of the integrally-heated tool. Statistical analysis reveals that the heating performance of an integrally-heated tool can be significantly improved when the channels’ layout is parallel. The shape of the channels has negligible effect and the distance between the channels should be determined based on the production requirement.

Effect of size and content of mesoscopic fillers on the polymerization induced viscoelastic phase separation

Fillers have great impact on the phase separation process and material properties of multi-component heterogeneous polymer composites. In this article, we have investigated the effect of surface affinity, size and content of mesoscopic fillers on the polymerization induced viscoelastic phase separation of thermoplastic modified thermosets by using optical microscopy, time-resolved light scattering, and dynamic mechanical analyses. Nanosized mesoscopic silica type fillers, both surface treated and untreated, showed significant enhancement effect on the viscoelastic phase separation of polyethersulfone modified epoxy resins with dynamic asymmetry, which resulted in a clear decrease of characteristic length scale of phase structure and an increase of relaxation time of phase separation. With increase of filler size from nanoscale to micron-size, the “enhanced viscoelastic effect” of fillers at the same content diminished quickly as both the phase evolution process and the size of phase structure shifted to those of blends without fillers. While increase of the content of fillers showed an enlarged enhancement effect on viscoelastic phase separation. Glass transition temperatures of filled blends with various filler contents and sizes obtained from dynamic mechanical study were consistent with the phase separation study.

Chemical treatments of coir pith: Morphology, chemical composition, thermal and water retention behavior

Coir pith is one of the most abundant agro waste found in the southern coastal regions of India, where the economy and livehood of people are largely dependent on the coconut industry. Many technologies have been developed successfully for the alternate use of coir pith. However the application of coir pith as fillers in polymer composite is limited. The major drawback of coir pith as filler in polymer is its low adhesion with the matrix and high water sorption and retention behavior. The present work is a part of research work carried out in our laboratory to modify the morphology and chemical properties of pith to make it better filler in the processing of polymer composites. Coir pith was subjected to mercerization followed by different types of chemical treatment. The products were analyzed in detail using FTIR, XRD, optical microscope, AFM and SEM. The chemical treatment resulted in increased density, thermal stability and reduced water retention behavior.

Thermorheological Properties and Thermal Stability of Polyethylene/Wood Composites

The thermal stability, flame retardancy, thermorheological, and mechanical properties of polyethylene/wood flour (PE/WF) composites were characterized. By time–temperature superposition treatment, addition of WF was found to lead to a complexity in the thermorheological behaviors in low-density PE/wood composites. However, high-density PE/wood counterparts showed no obvious thermorheological complexity. The effects of WF and ammonium polyphosphate contents on the thermorheological behavior and thermal stability were also studied. The current work should be of practical significance for the optimization of wood/plastic composite) formulae, as well as for further investigations on correlations between processing and performance of polymer composites.

Reliable optimisation control of a reactive polymer composite moulding process using ant colony optimisation and bootstrap aggregated neural networks

This paper presents a study on the optimisation control of a reactive polymer composite moulding process using ant colony optimisation and bootstrap aggregated neural networks. In order to overcome the difficulties in developing accurate mechanistic models for reactive polymer composite moulding processes, neural network models are developed from process operation data. Bootstrap aggregated neural networks are used to enhance model prediction accuracy and reliability. Ant colony optimisation is able to cope with optimisation problems with multiple local optima and is able to find the global optimum. Ant colony optimisation is used in this study to find the optimal curing temperature profile. In order to enhance the reliability of the optimisation control policy, model prediction confidence bound offered by bootstrap aggregated neural networks is incorporated in the optimisation objective function so that unreliable predictions are penalised. The proposed method is tested on a simulated reactive polymer composite moulding process.

Improvement of carbon nanotube dispersion in thermoplastic composites using a three roll mill at elevated temperatures

The paper reports the effect of using of a three roll mill as additional dispersion step after twin-screw melt extrusion of nanocomposites containing thermoplastic polymers and multiwalled carbon nanotubes. The three roll milling technology was adapted to elevated temperatures of up to 180 °C and examples are shown for its use in processing of different pre-compounded thermoplastic polymer composites based on polypropylene, polycaprolactone and ethylene–vinyl acetate. The aim is to enhance the state of dispersion achieved by the previous melt extrusion step. In particular, depending on the state of dispersion before three roll milling and the adapted conditions, like number of runs and gap sizes, a reduction of number and size of remaining primary nanotube agglomerates was found. This was studied using light microscopy. The resulting improvements in mechanical properties were assessed and could be attributed to the improved dispersion. In some cases agglomerate free samples could be achieved after the three roll milling process.

An angled robotic dual-nozzle electrospinning set-up for preparing PU/PA6 composite fibers

This paper presents the design and development of a robust electrospinning set-up for the processing of polymer composites at the nanoscale. A robotic-controlled movable dual-nozzle (keeping the rotating collector at a fixed position) set-up with two power supplies is presented for nanocomposite electrospinning. We studied the effect of different angles between two nozzles on the physicochemical properties of composite PU/PA6 electrospun mats obtained from this electrospining set-up. Scanning electron microscopy (SEM) images of the mats indicated that the diameter of the nanofibers and their evenness was affected by the angle between the nozzles. The effect of angle (between the nozzles) on the mechanical strength of the composite mats was also evaluated. The hybrid mat obtained from the dual- nozzle system was found to be mechanically stronger than the individual fibrous mat. Furthermore, the mechanical strength of the composite mat could be increased by decreasing the angle between the tips of the nozzles.

Fabrication and applications of cellulose nanoparticle‐based polymer composites

AbstractThe impressive mechanical properties, reinforcing capability, abundance, low weight, low filler load requirements, and biodegradable nature of nanoparticles from bioresources such as cellulose, make it an ideal candidate for the development of green polymer nanocomposites. Significant amount of research in this area is primarily focused on the extraction, qualitative surface modification, and evaluation of mechanical performance after filling in polymer matrixes at different ratios. The extreme agglomeration tendency, hydrophilic nature, difficult dispersion in many organic solvents of cellulose nanoparticles are the challenging obstacles when fabrication of such nanocomposites is concerned. Traditional processing of polymer composites mainly through extrusion and melt compounding, is not easily possible in case of cellulose nanocomposites due to higher possibility of poor dispersion and degradation of nanofibers. Therefore, issues related to the fabrication of nanofiber‐based products and their application appears to be one of the most important areas in order to enhance their competitiveness with other nanoparticles. This review is aimed to summarize the recent accomplishments and issues involving the use of cellulose nanoparticles in the development of new polymeric materials. POLYM. ENG. SCI., 2013. © 2012 Society of Plastics Engineers

Preliminary Study on Injection Molding Process of Single Polymer Composites

An approach of preparing single polymer composites (SPCs) by injection molding was demonstrated. Polypropylene (PP) was used as a model system to investigate this method. The thermal properties of PP granules and PP fibers were analyzed by Differential Scanning Calorimeter (DSC) to determine the processing temperatures. The flexural test of PP SPCs showed that the flexural strength was obviously improved compared to the non-reinforced PP. The results also indicated that the injection pressure, holding pressure and nozzle temperature greatly affect the flexural strength of PP SPCs. The microstructure observation showed no gaps between fibers and the matrix by using Scanning Electron Microscopy (SEM). The matrix melt was able to penetrate into fiber webs and the two materials had good interfacial compatibility.

Applying Computational Analysis in Studies of Resin Transfer Moulding

Resin Transfer Moulding (RTM) as it is most known process in the Resin Injections family, is an extensively studied and used processing method. This process is used to manufacture advanced composite materials made of fibres embedded in a thermoset polymer matrix. Fibre reinforcement in RTM processing of polymer composites is considered as a fibrous porous medium regarding its infiltration by the polymer resin. In this sense, the present work aims the computational analysis of a fluid in a porous media for a RTM composite moulding by using the ANSYS CFX® commercial software. In order to validate the numerical study of the fluid flow in a known RTM system, experiments was carried out in laboratory to characterize the fluid (vegetal oil) flowing into the porous media (0/90 glass fibre woven), were pressure and fibre volume fraction have been fixed. The numerical simulation provides information about volume fraction, pressure and velocity distribution of the phases (resin and air) inside the porous media. The predicted results were compared with the experimental data and its has shown a solid relationship between them.

Iterative Learning Control of a Reactive Polymer Composite Moulding Process

This paper presents an iterative learning control strategy for a reactive polymer composite moulding process using batch-wise linearised models that are identified from process operational data. In rapid thermal moulding processes, the degree of cure is controlled by the applied mould temperature. Due to the model plant mismatches and the presence of unknown disturbances, a pre-set (off-line optimised) moulding temperature profile would not always lead to the desired degree of cure. The repetitive nature of batch moulding process allow the information of the previous batch (or cycle) being used to enhance the operation of the current batch through iterative learning control. The control policy updating is calculated by solving an optimisation problem using a model linearised around a reference batch. In order to cope with process nonlinearities, process variations, and disturbances, the reference batch is taken as the immediate previous batch and the model is re-identified from the updated historical batch data using principal component regression. The proposed method is tested on a simulated reactive polymer composite moulding process.

Thermal properties of modified banana trunk fibers

Thermal decomposition of an agrowaste, namely banana trunk fibers (BTF) were investigated by thermogravimetry (TG) and derivative thermogravimetry (DTG) up to 900 °C at different heating rates (from 5 to 100 °C/min). The BTF was subjected to modification by means of various known chemical methods (mercerization, acetylation, peroxide treatment, esterification, and sulfuric acid treatment). Various degradation models, such as the Kissinger, Friedman, and Flynn–Wall–Ozawa were used to determine the apparent activation energy. The obtained apparent activation energy values (149–210 kJ/mol) allow in developing a simplified approach to understand the thermal decomposition behavior of natural fibers as a function of polymer composite processing.

Determination of Binding Energy and Solubility Parameters for Functionalized Gold Nanoparticles by Molecular Dynamics Simulation

The binding energy, density, and solubility of functionalized gold nanoparticles in a vacuum are computed using molecular dynamics simulations. Numerous parameters including surface coverage fraction, functional group (-CH(3), -OH, -NH(2)), and nanoparticle orientation are considered. The analysis includes computation of minimum interparticle binding distances and energies and an analysis of mechanisms that may contribute to changes in system potential energy. A number of interesting trends and results are observed, such as increasing binding distance with higher terminal group electronegativity and a minimum particle-particle binding energy (solubility parameter) based upon surface coverage. These results provide a fundamental understanding of ligand-coated nanoparticle interactions required for the design and processing of high-density polymer composites. The computational model and results are presented as support for these conclusions.

Processing of single polymer composites with undercooled polymer melt

An approach of applying undercooled polymer melt to prepare single polymer composites (SPCs) was investigated. The fibers were introduced into the liquid matrix at a temperature well below the matrix melting temperature. The method was demonstrated using polypropylene (PP) as an example. The degree of supercooling of PP was determined by differential scanning calorimetry and rheological measurement. The processing temperature window was determined to be from 125°C to 150°C, within which PP SPCs were successfully prepared by compression molding. The crystalline orientation of PP fibers was characterized by X-ray diffraction, and no significant change was found before and after compression molding. The SPC molded at 150°C containing 50% by weight of PP fabric achieved tensile strengths of approximately 220 and 180MPa in the weft and wrap directions, much higher than the value of 30MPa for the non-reinforced PP. The effect of processing temperature on tensile strength of PP SPCs was also investigated. The results showed that, as the processing temperature decreased, the tensile strength decreased in both weft and warp directions. This reduction in tensile strength was correlated with the increased viscosity of the matrix and consequently poor wetting of the PP fabric at reduced processing temperature.