Volume 32, Issue 1

The effect of carbon nanotubes (CNTs) on the capillary extrusion behavior of low-density polyethylene (PE) was investigated. From the linear viscoelasticity and the morphology observation, it was found that the CNTs were well dispersed throughout the PE matrix and our system belonged to the semi-dilute regime. The strain hardening, which quantifies the extension of the PE chain, decreased by presence of CNTs in the uniaxial elongational deformation. In contrast, the normal stress difference was almost unaffected by CNTs in the shear deformation. The capillary extrusion behavior revealed that swell ratio decreased with increasing the CNT content although melt fracture was promoted. We summarize that the suppression of swell and promotion of melt fracture are attributable to the orientation of CNTs.

The Mullins effect during uniaxial compression tests, together with its reversibility of the styrene-butadiene rubber (SBR)/carbon black (CB) vulcanizate and ethylene-vinyl acetate copolymer (EVA)/SBR/CB thermoplastic vulcanizate (TPV) were investigated systematically. The experimental results indicated that the Mullins effect could be observed during the cyclic uniaxial compression tests and accompanied with stress softening, residual deformation accumulation and hysteresis. The reversibility of the Mullins effect showed a temperature-dependence feature and was enhanced with increasing temperature. The morphology study showed that the SBR particles with average diameter of 10–20 μm were dispersed evenly in the etched surface of EVA/SBR/CB TPV.

A series of bio-based hybrid thermosets composed of maleinated acrylated epoxidized palm oil (MAEPO) and vinyl ester resin (VE) were produced using free radical-induced crosslinking. The amount of petroleum-based resin which was replaced by bio-resin (MAEPO) was varied from 5 to 20 wt%. The structure of the polymer systems was investigated by scanning electron microscopy and dynamic mechanical analysis. The mechanical properties of the VE/MAEPO resins were studied using tensile, flexural and impact tests. The result obtained from structural analysis revealed that for the polymer hybrids with up to 20 wt% bio-resin content, there is good compatibility between MAEPO and VE as no phase separation was observed for these systems. The prepared eco-friendly bio-based thermosetting resins exhibit remarkable improvement in toughness parameters, such as ductility and impact strength, thereby showing potential for use in composites and nanocomposites applications.

We report the impact of grafting glycidyl methacrylate (GMA) at different degrees onto isotactic polybutene-1 (iPB-1) on the crystallization process. The study of the crystal form transition using FTIR and X-ray Diffraction (XRD) revealed that the conversion degree from form II to form I of the grafted iPB-1 (iPB-g-GMA) was higher than that of iPB-1 under the same experimental conditions and increased with increasing grafting degree. The spherulitic size of iPB-g-GMA was smaller compared to iPB-1 at the same amplification factor in Polarized Optical Microscopy (POM). The kinetic parameters of the non-isothermal crystallization process have been determined based on Differential Scanning Calorimetry (DSC) experiments and the Ozawa and Mo equation. The results showed that the crystallization rate of iPB-g-GMA was higher than that of iPB-1. The activation energy for the non-isothermal crystallization process of iPB-g-GMA (with a grafting degree of 1.54%) was lower than that of iPB-1, which further illustrated that grafting GMA on iPB-1 accelerated the crystallization rate.

Micro and nano structures have unique properties such as large specific surface area, high porosity and smaller diameter size. They have several potential applications in textile industries, filtration systems and biomedicine. Common methods employed for fabrication of nanofibers include electrospinning, force spinning, biocomponent spinning and melt blowing. Flashing provides an easy method to produce discrete fibers from higher molecular weight polymers. Its production rate is also high compared to conventional methods, making it an attractive technique. Experiments were performed using the flashing method in which a polymer is dissolved in a suitable solvent at supercritical conditions of temperature and pressure. Then, the formed homogeneous solution was extruded through a nozzle at high speed into a zone of substantially lower temperature and pressure. Polyethylene terephthalate was used as the polymer while dichloromethane and Freon 12 were the solvents. By changing various parameters in the experiment, a variety of structures such as micro scale fibers, spheres, porous structures as well as condensed irregular structures were obtained. Further, ESEM, cryo FEG SEM and porosity measurements were carried out on the samples obtained to study their external and internal structures. We have identified morphological phase space of this system so that the microstructure can be tuned to the desired state based on process parameters.

Polymer composites comprising sulfonated poly(ether ether ketone) (SPEEK) and 10 to 50 wt% of Poly(trimellitic anhydride chloride-co-4,4′-methylenedianiline) (PTCMA) were prepared by solution casting. The effects of PTCMA concentrations on morphological, thermal and transport properties (water uptake, methanol permeability, ion exchange capacity and proton conductivity) were investigated. A morphological analysis revealed an homogenous dense microstructure for all the composites. Also, transport property tests revealed that the water uptake, methanol permeability and ion exchange capacity were enhanced by the addition of PTCMA whereas proton conductivity deteriorated. As shown by a thermogravimetric analysis, the difference between the thermal properties of the pure SPEEK and the composites was insignificant. Overall, the composites were observed to display a better global performance in terms of transport properties than pure SPEEK.

This paper deals with investigations of rotational molding of LLDPE – Fumed Silica (FS) nano composites. The investigations were conducted at an industrial scale using a three arm biaxial rotational molding machine by carefully monitoring the Internal Air Temperature (IAT) within the mold. The effect of 4% FS on powder flow quality (dry flow and bulk density), melt flow quality (Melt Flow Index (MFI), static mechanical properties (tensile strength, modulus, toughness, flexural strength and impact strength) as well as dynamic mechanical properties (storage and loss modulus), along with creep and relaxation were investigated. Morphological studies were conducted to correlate the above findings with the dispersion of the nano particles within the LLDPE matrix.

In this work a novel methodology to balance the flow distribution in complex extrusion dies is proposed. For this purpose, the profile cross section geometry is divided into simpler geometries (L and T shaped profiles), which are balanced with a surrogate model obtained by a detailed numerical study. The numerical simulations are performed considering the non-isothermal flow of Bird-Carreau inelastic fluids, and the numerical computations are performed with a solver implemented in OpenFOAM computational library. The proposed methodology is assessed with some case studies.

Polypropylene (PP)/ethylene propylene diene monomer (EPDM)/ graphene nanosheets (GNs) were compounded by a two-step melt mixing process via an internal mixer (brabender plasticorder). The effect of GNs, graphene oxide (GOSs) and graphene oxide functionalized with PP chains (PP-g-GOSs) on various blend properties were investigated. Wide X-ray diffraction (WAXD) patterns and transmission electron microscopy (TEM) images of the prepared nanocomposites revealed that the nanofillers were mostly dispersed into the PP phase and the dispersion state of GNs was improved with functionalization of graphene. SEM photomicrographs indicated that rubber droplets were distributed in the PP phase and a reduction of the dispersed EPDM droplet size was observed most likely due to increase in the viscosity of the PP-phase during melt mixing. The effects of nanofillers on thermal, mechanical and rheological properties were reported, and the obtained results were discussed in terms of morphology, state of dispersion and distribution of the nanofillers within the PP matrix. As for the mechanical properties, an improvement of 56% in tensile modulus and 48% in tensile strength, while 72% reduction in elongation at break was observed. The DMTA results revealed that the nanocomposites based on PP-g-GOSs had lower damping behavior and the intensity of the loss factor decreased by increasing the GNs content. These results indicate the presence of a strong interfacial interaction between the nanoplatelets and the polymer matrix.

When a material volume consisting of an uncured rubber matrix reinforced with two non-parallel sets of embedded reinforcement wires or cords is subjected to large deformations, pantographing may occur. In other words, the angles between reinforcement wires change. We introduce a simple phenomenological fluid model suitable for the numerical prediction of pantographing, as can be encountered in industrial processes such as the manufacturing of rubber tires or reinforced hoses. The reinforced material is described with an orthotropic continuous fluid model. Here the reinforcement wires or cords are accounted for by the orthotropy, whose direction is locally affected by the deformation undergone by the matrix, and is updated accordingly. The model is subsequently applied to the simulation of a sagging experiment, where the role of pantographing is illustrated.

Polyamide 12 (PA-12) test plates were injection molded using different melt temperatures and the influence on mechanical properties was investigated using quasi-static tensile and instrumented impact behavior in two conditioned states: dried, and following accelerated moisture intake. Energy absorption in tension is strongly dependent on process temperature (variations up to 99%) and additional variation (around 18%) was evident when testing at different conditioning states. Under high-velocity loading, the total impact energy varied by up to 8.70% and 9.05%, when systematic changes were made to process melt temperature and at moisture content, respectively, with all samples failing ductile. Differential Scanning Calorimetry (DSC) was used to characterise the unique endothermic melting behavior of molded PA-12 samples, by linking different process histories to the respective mechanical properties. With focus on the first heating curve progression, significant changes within the endothermic melting region were pointed out and quantified by using MatLab (software), proving DSC as a reliable testing tool for post-production analysis with increased practical implications regarding quality control as well as failure analysis. Findings for the initial heating curve progression were explained by studying the re-crystallisation peak values during cooling phase and obtained data for the second heating.

The effect of the maleic anhydride grafted styrene-ethylene/butylene-styrene (SEBS-g-MA) block copolymer on the properties of thermoplastic polyurethane (TPU) and polypropylene (PP) blends were studied. TPU/PP and TPU/PP/SEBS-g-MA blends with different weight ratios were prepared in a twin-screw extruder. The thermal properties of the blends were investigated via differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). The morphological structure of the blends as well as the effect of SEBS-g-MA block copolymer on the reduction of domain size and particle dispersion were investigated via scanning electron microscopy (SEM). The results from the uncompatibilized blends clearly indicated immiscibility of TPU and PP resulting in undesirable properties. The thermal properties of TPU/PP blends were improved by compatibilization with SEBS-g-MA. Addition of the SEBS-g-MA block copolymer resulted in a finer dispersion of the minor phase and clearly improved interfacial adhesion.

This work is concerned with the extrusion blow molding of polymeric blends containing thermotropic liquid crystalline polymer (TLCP) and high density polyethylene (HDPE), using a single screw extruder. The TLCP is synthesized from terephthalic acid, 4-hydroxybenzoic acid, hydroquinone and hydroquinone derivatives, the melting point of which is 280 °C. Because the TLCP is usually processed at much higher temperatures than HDPE, the thermal stability of HDPE at elevated temperature is evaluated. It is shown that HDPE is relatively stable in the processing temperature range of the TLCP used in this work (260 to 300 °C). Bottles are successfully produced from the blends containing 10, 20 and 50 wt% TLCP. The TLCP/HDPE blend bottles exhibit enhanced modulus relative to pure HDPE. However, the improvement in tensile strength is marginal. At 10 and 20 wt% TLCP contents, the TLCP phase exists as platelets aligning along the machine direction, while a co-continuous morphology is observed for the blend containing 50 wt% TLCP. To further enhance the mechanical properties of the blends, the preliminary effectiveness of maleic anhydride grafted HDPE (MA-g-HDPE) as a compatibilizer is studied. The injection molded ternary blends of TLCP/HDPE/MA-g-HDPE have demonstrated superior mechanical properties over the binary TLCP/HDPE blends, which suggests MA-g-HDPE as a potential compatibilizer for developing high performance TLCP/HDPE containers with enhanced mechanical properties.

Poly(L-lactide) (PLLA)/poly(D-lactide) (PDLA)/nanoclay nanocomposites with nanoclay contents ranging from 1% to 8% w/w were prepared by melt blending using an internal mixer. Wide-angle X-ray diffraction (XRD) and differential scanning calorimetry (DSC) results confirmed that complete stereocomplex polylactide (PLA) crystallites without any homocrystallites were produced when equal amounts of PLLA and PLDA were mixed. The nanoclay in the stereocomplex polylactide nanocomposites acted as a nucleating agent that significantly enhanced stereocomplex crystallization, resulting in smaller and finer spherulites. Compared to neat PLLA, the melting temperature of the stereocomplex polylactide and its nanocomposites was about 55°C higher. The crystallization temperature of the stereocomplex nanocomposites was also 16°C and 55°C higher than that of the stereocomplex PLA and neat PLLA, respectively. These significant increases in transition temperatures improved the thermal stability of the stereocomplex nanocomposites compared to regular polylactide, which was confirmed by thermogravimetric analysis (TGA). The TGA results also showed that increasing nanoclay content increased the thermal stability of the stereocomplex nanocomposites. Finally, XRD and transmission electron microscopy showed an intercalation nanoclay basal spacing of 3.22 nm in the stereocomplex nanocomposites; a slight increase from the 1.86 nm basal spacing in the as-received nanoclay.

Polypropylene/organoclay nanocomposites were prepared by melt-mixing in a twin-screw extruder. Polypropylene grafted with maleic anhydride was used as compatibilizer. The evolution of the microstructure along the screw profile was characterized through dead-stop experiments. In order to quantify the multi-scale dispersion state of the nanocomposites, different techniques have been used: scanning electronic microscopy (SEM) to observe the large remaining aggregates, X-Ray diffraction measurements to characterize the intercalation state by measuring the interlamellar distance, and finally rheological characterizations in the molten state to assess the dispersion state at the nanoscale. The effects of low barrel temperatures and high matrix viscosity were tested, in order to improve exfoliation by an increase in shear stresses.

The results have been achieved by adjusting the structure to improve the performance of micro injection molded isotactic polypropylene products. Annealing was adopted to optimize the performance of isotactic polypropylene micro injection molded gears. It was found that the annealing temperature shows greater influence on the crystalline structure of the micro injection molded gears than annealing time. The layer mechanical properties were greatly improved after annealing, about 1.7-fold for modulus and 1.9-fold for hardness of the micro injection molded gears relative to the unannealed sample. This is due to the fact the state of molecular chain aggregation tends to be consistent after high temperature annealing in the micro injection molded isotactic polypropylene gear sample.