Band 33, Heft 2

The rheological behavior of epoxy resin filled with glass hollow microspheres was studied using three types of microspheres with different particle size distributions. The shear-rate dependence on viscosity, as well as relative apparent viscosity, of the suspensions was investigated at different microsphere filler loadings. The change in relative viscosity with different types of microsphere loads was also investigated using the established semi empirical model to estimate the critical filler load. It was found that the critical filler load for all suspensions tested depends mostly on the filler size distribution, neither on the average filler size nor on the specific surface area of the filler.

Blends between Novatein thermoplastic protein and polylactic acid (PLA) have been prepared by reactive extrusion using itaconic anhydride grafted PLA. At equal proportions of Novatein and PLA, the absence of a compatibilizer formed a dispersed phase morphology of Novatein in PLA and the incorporation of compatibilizer formed a co-continuous morphology. Incorporating PLA in Novatein can improve the tensile strength of Novatein by 42% and the impact strength by 36% at an equal proportion blend (50/50) in the presence of a compatibilizer. Thermal analysis revealed that 50/50 was the phase inversion point, above and below this composition the material behaved similarly. The effect of compatibilizer was evident in wide-angle X-ray scattering. In the absence of compatibilizer three phases were detected: crystalline Novatein, amorphous Novatein, and amorphous PLA phases. With compatibilizer, the blend was moving towards two phases: crystalline Novatein, and an amorphous blend of Novatein and PLA. Itaconic anhydride grafted PLA improved miscibility between Novatein and PLA, and its use can potentially lead to the production of Novatein/PLA foams.

The crystallization behavior and mechanical properties were investigated by mixing the traditional α-form nucleating agent (sodium benzoate, SB) and commercialized β-form nucleating agent (TMB-5) in isotactic polypropylene (iPP). Mechanical properties were evaluated by universal testing machines. X-ray diffraction (XRD) and differential scanning calorimetry (DSC) were conducted to illustrate the crystallization behavior. Polarized optical microscopy (POM) was adopted to observe the crystal morphologies. The experimental results show that the weight ratio of two types of nucleating agents determines the final crystal structure and mechanical properties of iPP. When the weight ratio of [SB] : [TMB-5] is 4 : 1, the impact strength and flexural modulus of iPP reach a maximum value. Compared with the single component β-form nucleating agent, the compound nucleating agent exhibits significant synergistic effect and shows better mechanical properties. It is expected that this new nucleation system will have potential industrial applications.

An extensive experimental and theoretical study has been performed on screw filling in starve fed/flood fed single screw extruders. The effect of screw speed, flow rate (level of starvation) and die geometry has been investigated. A “screw pulling-out” technique was used in the study. The solid conveying, melting positions, the extent of starvation, and the fully filled regions were observed. It was seen that filling of the screw increases with an increase of the flow rate at a fixed screw speed, and decreases with an increase of the screw speed at a fixed flow rate. The screw filling is strongly dependent on the die geometry and increases with an increase of the resistance of the die. The pressure was also measured, and it was observed that it considerably decreases with starvation. Mechanism of screw filling has been discussed. The simulations and experiments were performed for low density polyethylene (LDPE) and high density polyethylene (HDPE) at various operating conditions, both for starve fed and flood fed extrusion. Fill factor, pressure, temperature and melting profiles have been computed and validated experimentally. All the experimental observations were consistent with the simulations.

Mechanical properties of Novatein thermoplastic protein compounded at different extrusion temperatures and processing water contents have been examined in a factorial experiment. Thermoplastic proteins are moisture sensitive and can be prone to thermal degradation during processing. Processing water was varied between 30 and 45 parts per hundred parts bloodmeal while the extrusion temperature was varied between 120 and 150 °C to identify a processing window suitable for process scale up. To resolve any effects processing water had on protein-protein interactions from its plasticising effect, injection molded specimens were mechanically tested both as molded and after conditioning at controlled temperature and humidity. Despite all conditioned samples having approximately the same moisture content, mechanical properties were different. Tensile strength and modulus decreased with increasing processing water at the same equilibrium moisture content. DMA and WAXS suggested this was due to changes in chain mobility within the amorphous phase of the material, rather than conformational change towards a more ordered state. Properties of unconditioned specimens were mostly dependent on the plasticising effect of different amounts of processing water remaining in the material after injection molding. Extrusion temperature had very little effect on mechanical properties, suggesting that Novatein is robust enough to handle some temperature variations during processes such as injection molding.

HZMMA is a zinc salt of unsaturated carboxylic acids with a single hydroxyl group. The chemical behavior and morphological changes of the HZMMA were investigated by Fourier Transformed Infra Red spectroscopy (FTIR), thermal gravimetry (TGA), Scanning electron microscopy (SEM) and X-ray diffractometry (XRD). The experimental results showed that it was possible for HZMMA to be used as a reactive enhancer to prepare ionic polymers/polyurethane composites. A series of ionic polymer/polyurethane were prepared by poly (tetramethylene glycol) (PTMG), toluene diisocyanate (TDI) and self-made chain extenders which consisted of Dimethylthio toluene diamine (DMTDA), Dicumyl Peroxide (DCP) and HZMMA by prepolymerization. The effect of the content of HZMMA on the structure and properties of the composites were studied by DMA, TGA, XRD. The results indicated that HZMMA had formed poly-HZMMA particles by peroxide-induced dynamic vulcanization and the degree of micro phase separation of polyurethane were improved when the content of HZMMA was suitable. The poly-HZMMA particles improved the maximum decomposition temperature of the soft segment and the storage modulus of polyurethane. When the mass fraction of HZMMA and DCP were at 2 ‰, the maximum in the mechanical properties of the ionic polymers/polyether polyurethane composites was achieved.

This article proposes a first of its kind manufacturing route to fabricate thermoplastic based functionally graded materials (FGMs). FGMs and homogeneous composites are fabricated by means of an especially designed mold and a punch. The punch acts as an integral rotating member of the mold and has a cavity where the material is filled to produce the desired samples. The punch rotates at 1 800 min −1 for two minutes to create deliberate segregation of fibers towards the periphery of the punch cavity. Polypropylene filled with 15 wt% and 30 wt% glass fibers is used to fabricate FGMs and homogeneous composites. Unfilled Polypropylene is also fabricated for comparative study. Gradation in FGM is verified by scanning electron microscopy (SEM) analysis and Shore D hardness measured in four different zones of the fabricated specimens. Gradation in FGM is also verified by ignition loss test method. It is observed from SEM that fibers tend to conglomerate towards the circumference due to inherent effects of centrifugal force. The hardness of FGMs is found to be high as compared to homogeneous composites. This route shows a promising potential for fabrication of thermoplastics based FGMs which otherwise are difficult to make because of their rapid solidifying characteristics.

One of the largest challenges in production using melt-based processes is the manufacturing of precise parts. Especially due to high differences in temperature of the produced parts while processing, shrinkage cannot be avoided, since the processing material is typically heated up, molded and cooled down. In injection molding, the molten plastic is loaded by high variations in temperature and pressure while being processed. The gradients can lead to a significant change of the local specific volume, shrinkage potential and inner stresses, which can result in part warpage. In order to increase the precision of the manufactured parts, the shrinkage potential has to be homogenised to achieve an even shrinkage and therefore minimise part warpage. In this work, the approach for homogenisation of the shrinkage potential is a homogenisation of the specific volume and density respectively. Pursuing the goal of a homogeneous distribution of the specific volume leads to manipulation of the influencing factors namely temperature and pressure. The impact of temperature and pressure changes on the specific volume can further be quantitatively described by the material specific pvT-data. Based on geometric restrictions, a manipulation of the local pressure inside the cavity in most cases is impossible. However, on the other hand, a local control of the temperature is possible using highly dynamic tempering techniques. Based on this line of arguments, the paper describes the development of a highly segmented dynamic temperature control in injection molding to locally influence the mold and part temperature. Thereby, the specific volume of the part will be locally adjusted to reduce warpage as well as to compensate process variations occurring by changing material properties or varying ambient conditions. Due to the nature of thermal processes a special control strategy has to be developed to enable accurate temperature control, which is able to compensate slow thermal reaction in a highly dynamic process.

The long-chain branched ethylene-tetrafluoroethylene copolymer (B-ETFE) was synthesized by radical polymerization using ethylene, tetrafluoroethylene, termonomer, and a very small amount of divinyl monomer. We studied melt rheology under shear and elongational flow, and foamability for B-ETFE, comparing with conventional linear ETFE. Addition of a small amount of the divinyl monomer had a considerable impact on the melt rheology of ETFE and its blends. The observed non-linear elongational behavior and emergence of long relaxation time components can be explained by long-chain branching in the modified ETFE. B-ETFE and its blends showed excellent foaming processability: uniform and smaller cell sizes and much higher cell number densities than those of linear ETFE. To the best of our knowledge, this is the first report of the enhancement of the melt rheology of ETFE from the viewpoint of modification of its molecular architecture.

Nanocomposites of polymethylmethacrylate (PMMA) and CdSe were fabricated by a casting technique. The result showed that CdSe@PMMA can be used in white and green light emitting devices. 0.01CdSe@PMMA exhibits monochromatic green color emission with the highest fluorescent quantum yield and lowest optical band gap value, while CdSe@PMMA with other ratios shows a multicolor emission. The band-edge emits in the vicinity of 280 – 296 nm but a more stable intensive green color emission at 553 nm is found for 0.01CdSe@PMMA. The change in E g (4.18 to 4.4) eV values is due to the interaction between the PMMA polymer and CdSe.

The crystallization behavior of a newly developed polyvinyl alcohol with 1,2-diol side-chains (DPVA) was investigated for different 1,2-diol side-chain, magnesium acetate, and sodium acetate contents. Crystallization by stepwise cooling, isothermal and non-isothermal crystallization (the actual cooling process in melt molding) experiments were conducted. Upon crystallization analysis by stepwise cooling, the end surface energy of DPVA increased as the 1,2-diol side-chain content was increased. The isothermal crystallization process exhibited longer half crystallization times at high 1,2-diol side-chain and magnesium acetate contents. Upon Kissinger analysis of the non-isothermal crystallization results, the effect of the acetate salts was found to be smaller than that for isothermal crystallization, while the smaller number of repeating units in the lamellar structure, reflecting a higher side-chain 1,2-diol content, resulted in a smaller activation energy for DPVA crystallization. In addition, analyses by the Ozawa method and the Kissinger Plot suggested possible changes in the mode and dimension of the crystal growth of DPVA.

The present work reports the empirical findings of the effects of mean particle size and weight percentage of CaCO 3 on selected rheological characteristics of filled LDPE. The experimental results indicated that the two parameters studied had noticeable influence on the selected rheological properties of LDPE. Studies on the slip velocity and critical shear stress based on Mooney analysis revealed that the designed benefits brought by the incorporation of additives (such as CaCO 3 ) into a polymer (such as LDPE) may not be justified by their possible adverse effects. It is also shown in this report that melt index and apparent viscosity of the selected polymer systems were well correlated with mean particle size of CaCO 3 and its weight percentage.

The fountain flow effect in a mold cavity results in molecular orientation that is likely to create flow-induced residual stresses, warpage of finished products, and excessive shrinkage, thus making it difficult to guarantee high precision control. This study uses a gas counter pressure technique to inhibit fountain flow and employs a visualization mold design to observe the influence of counter pressure on melt flow behavior, in order to discuss the impact of the counter pressure mechanism on the fountain flow. The visualization mold designed herein and the clip cavity help to test the counter pressure mechanism in injection molding, while the observed particles and high-speed camera assist in observing the influence of fluid flow behavior and counter pressure on the fountain flow effect. The study observes and tracks the flow trajectory of particles in the melt, with findings showing that the closer the flow line of the melt is to the mold wall, the shorter the offset distance will be to the outward flip. Moreover, the closer to the center, the longer the offset distance of the outward flip meaning that it flips outwards in the melt-front nearby the center line and stays on the mold wall surface to form a new frozen layer. The melt-front length changes under different counter pressures and different mold temperatures. The front length changes present the inhibitory effect of counter pressure on the fountain flow, which is more apparent at the far gate than at the near gate. The melt-front lengths of the counter pressure of 0 bar at mold temperatures of 40 °C and 20 °C increase 1.5% and 4.7%, respectively, meaning that the thicker the frozen layer, the more apparent the fountain effect.

Recycling of plastics is becoming more important nowadays due to the increasing amount of waste that is generated worldwide. Post-consumer plastics have a large volume and their harmful effects must be considered. From this perspective, the option of recycling post-consumer plastics has become more and more necessary. The main objective of this research is the selective separation of polypropylene (PP) and high density polyethylene (HDPE). On this basis, various flotation parameters were tested on virgin plastics and optimized conditions were applied to post-consumer plastics. PP particles with a purity of 96.30% were obtained with a recovery rate of 97.4% in virgin polymer separation, while HDPE particles were obtained as the sunken product with 97.38% purity and a recovery rate of 96.3%. Besides, almost all PP and HDPE particles were selectively separated with the highest recovery rates when using 500 g/t calcium lignosulfonate (CLs) as a plasticizer in post-consumer polymer separation. Moreover, water reuse was investigated to determine the recovery and economy of plasticizer without adding extra water during the experiment. Therefore, it can be concluded that this process is environmentally friendly in terms of PP and HDPE recycling and reuse of process water.

This work presents a new design procedure for improving the flow distribution in complex profile extrusion dies. The proposed approach is based on open source software and aims to motivate both academics and industrials to consider numerical methodologies in their future developments. A new solver was implemented in OpenFOAM computational library in order to model the steady non-isothermal flow of inelastic fluids. The developed code was verified with the Method of Manufactured Solutions. The capability of the proposed design procedure was experimentally assessed with an industrial case study, and the results obtained suggest that the computational based design aid is an excellent alternative to the usual experimental trial-and-error procedure used in industry.

An industrial fibreglass winding process is employed to apply graphene based sizing (0.2 wt% graphene concentration) on fibreglass surface. Both SEM and Raman spectroscopy characterization have proved that the coating of graphene on fibreglass surface is homogeneous and that the roughness of the fibreglass surface was improved. Long fiberglass-graphene reinforced PA66 pellets are successfully prepared through a pultrusion process. LGF-graphene-PA66 composites are produced following an injection molding process. Thermal conductivity was found to increase from 0.23 W/m · K −1 to 0.67 W/m · K −1 when compared with samples without graphene coating. The tensile strength of LGF-graphene-PA66 is 196 MPa while that of LGF-PA66 is 173 MPa. Tensile modulus is also found to increase to 13.5 GPa from 10.6 GPa after graphene coating. This new graphene coating process is a good method to produce high performance composites.