Low Viscosity Polypropylene Research Articles

Slippery membrane surface tuning with polypropylene coating to treat real aquaculture wastewater in membrane distillation

Surging growth of aquaculture industry has alarmed the public when the wastewater discharged had an adverse effect on the environment. This current study is a pioneer in the use of membrane distillation (MD) to treat real aquaculture wastewater. In addition to excellent hydrophobicity, the slippery surface of membrane used for MD is another key factor that enhances the performance of MD. The slippery surface of the membrane was tuned by layering high-viscosity and low-viscosity polypropylene (PP) polymers on the electrospun membrane by solvent-exchanged method. While the high-viscosity PP coating (PP/HV) rendered the membrane surface slippery, the low-viscosity PP coating (PP/LV) caused the fish farm wastewater to have stick-slip movement on the membrane surface. In the long-term 70-hour direct contact membrane distillation (DCMD) separation, PP/HV and PP/LV membranes can perfectly eliminate the undesirable components in the fish farm wastewater. The PP/HV membrane has registered a flux of 19.1 kg/m2·h, while the flux of PP/LV membrane was only 7.3 kg/m2·h. The PP/HV membrane also showed excellent anti-scaling properties in relative to the PP/LV membrane. This is because the PP/HV membrane promotes effortless gliding of the feed water along the surface of the membrane, while the surface of the PP/LV membrane has a static water boundary. Therefore, it can be concluded that the application of MD using the membrane coated with high-viscosity PP polymer is a feasible technology for the treatment of aquaculture wastewater.

Influence of formulation on morphology and rheology of polypropylene/polyamide blends filled with nanoclay mineral particles

The effect of formulation on the morphological and rheological properties of clay polypropylene/polyamide 12 nanocomposites is investigated. Two clay minerals, organically modified montmorillonite and synthetic talc, and two polypropylenes matrices, a low viscosity polypropylene and a high viscosity polypropylene, are used. The higher polypropylene matrix viscosity strongly influences the interfacial coverage of polyamide nodules, by slowing down the migration of fillers from polypropylene matrix to polyamide nodules. The nature of clay minerals as well as the polypropylene matrix viscosity is shown to influence the change from nodular to non-nodular morphology of nanocomposites. A comparative study of the viscoelastic properties of montmorillonite or synthetic talc high viscosity polypropylene/polyamide 12 nanocomposites is performed through the use of Palierne's model. Surprisingly, the results show that a developed montmorillonite interphase behaves like a weakly developed synthetic talc interphase suggesting that the nature and structure of clay particles located at the interface play a key role in interphase viscoelastic properties.

Effect of Maleic Anhydride Modification on the Mechanical Properties of a Highly Filled Glass Fibre Reinforced, Low-Viscosity Polypropylene for Injection Moulding

<p class="1Body">Short glass fibre reinforcement is one of the most important measures to improve the mechanical properties of injection moulded parts. The need for increasing performance leads to high fibre contents which is a critical fact due to the contrasting behaviour of strength, stiffness and impact properties. In this study a high-fluidity polypropylene (PP) is compounded with short glass fibres up to 70 weight percent and comparatively investigated with the adding of maleic anhydride (MAH) as compatibilizer. Due to the high fluidity of the PP, which ensures a good embedding of the fibres, the tensile modulus increases up to 65 weight percent, tensile strength up to 50 weight percent of glass fibre content. Adding the MAH increases strength and impact properties, while the tensile modulus only shows an improvement at high fibre content. The influence of the compatibilizer effect diminishes at higher fibre contents, especially for the impact strength which could so far not be clarified exactly. Reasons could be the reduction of fibre length at higher fibre contents and the increasing influence of the brittle fibre component. With the adding of MAH the contrasting behaviour of the impact properties in comparison to strength and stiffness can be reduced and the optimum over all mechanical properties can be shifted to higher fibre contents.</p>

Effect of Maleic Anhydride Modification on the Mechanical Properties of a Highly Filled Glass Fibre Reinforced, Low-Viscosity Polypropylene for Injection Moulding

<p class="1Body">Short glass fibre reinforcement is one of the most important measures to improve the mechanical properties of injection moulded parts. The need for increasing performance leads to high fibre contents which is a critical fact due to the contrasting behaviour of strength, stiffness and impact properties. In this study a high-fluidity polypropylene (PP) is compounded with short glass fibres up to 70 weight percent and comparatively investigated with the adding of maleic anhydride (MAH) as compatibilizer. Due to the high fluidity of the PP, which ensures a good embedding of the fibres, the tensile modulus increases up to 65 weight percent, tensile strength up to 50 weight percent of glass fibre content. Adding the MAH increases strength and impact properties, while the tensile modulus only shows an improvement at high fibre content. The influence of the compatibilizer effect diminishes at higher fibre contents, especially for the impact strength which could so far not be clarified exactly. Reasons could be the reduction of fibre length at higher fibre contents and the increasing influence of the brittle fibre component. With the adding of MAH the contrasting behaviour of the impact properties in comparison to strength and stiffness can be reduced and the optimum over all mechanical properties can be shifted to higher fibre contents.</p>

The effect of sample weight in thermogravimetric analysis of low viscosity polypropylene in air atmosphere

Low viscosity polypropylene is a new group of homopolymers for the manufacture of melt-blown nonwovens. The thermooxidative degradation of isotactic polypropylene was studied. Experiments using varied sample size and flow rates were undertaken to determine possible effects of these experimental parameters on the low viscosity thermo-oxidation process. It was found that the results of thermogravimetric analysis (temperature of 50%) of low viscosity polypropylene samples very strongly depend on the weight of the sample. The influence of gas flow conditions, sample pan geometry and sample melt flow rates parameters on the results of thermogravimetric analysis has not been observed.

Development of Porous Electrode Gas Diffusion Layers for Proton Exchange Membrane Fuel Cells

The aim of this work was to develop a porous film structure for an electrode gas diffusion layer (GDL) used for proton exchange membrane fuel cells (PEMFCs). This film was made from a matrix composed of two immiscible polymers filled with a mixture of electrically conductive materials fabricated via a twin-screw extrusion process followed by selective extraction of one of the two polymers. The matrix consisted of low-viscosity polypropylene and polystyrene (PS) and the conductive additives were composed of high specific surface area carbon black and synthetic flake graphite. The conductive blends were first compounded in a corotating twin-screw extruder and subsequently extruded through a flexible film die to obtain a GDL film of around 500μm having high electronic conductivity. The PS phase was then extracted with tetrahydrofuran (THF) solvent and a film of controlled porosity was generated. The morphology of the GDL porous structure was then analyzed by scanning electron microscopy. GDL porosity characterization was done by both Brunauer–Emmett–Teller (BET) and mercury-intrusion porosimeter. The effects of PS concentration and extraction time with THF on GDL porosity were also studied. Pore-size distribution obtained by BET and mercury-intrusion porosimetry revealed that the GDL structure is composed by both mesopores and macropores. Mesopores represent more than 60% of the total pore volume inside the GDL film.

The influence of matrix viscosity and composition on the morphology, rheology, and mechanical properties of thermoplastic elastomer nanocomposites based on EPDM/PP

AbstractThe morphological and rheological properties of thermoplastic elastomer nanocomposites (TPE nanocomposites) were studied using different viscosities of polypropylene (PP) and ethylene‐propylene‐diene monomer (EPDM) rubber content (20, 40, 60 wt%). The components, namely EPDM, PP, Cloisite 15A, and maleic anhydride‐modified PP as compatibilizer, were compounded by a one‐step melt mixing process in a laboratory internal mixer. The structure of the nanocomposites was characterized with X‐ray diffraction, scanning electron microscopy, transmission electron microscopy, and rheometry in small amplitude oscillatory shear. The distribution state of the clay between the two phases (PP and EPDM) was found to be dependent on the viscosity ratio of PP to EPDM. In the nanocomposites prepared based on low viscosity PP (LVP) and EPDM, the clay was mostly dispersed into the PP phase and the size of the dispersed rubber particles decreased in comparison with unfilled but otherwise similar blends. However, the dispersed elastomer droplet size in the high viscosity PP (HVP) blends containing 40 and 60% EPDM increased with the introduction of the clay. For TPE nanocomposites, the dependence of the storage modulus (G′) on angular frequency (ω) followed a clear nonterminal behavior. The increase in the storage modulus and the decrease in the terminal zone slope of the elastic modulus curve were found to be larger in the LVP nanocomposite in comparison with the HVP sample. The yield stress of nanoclay‐filled blends prepared with LVP increased more than that of HVP samples. The tensile modulus improved for all nanocomposites but a higher percentage of increase was observed in the case of LVP samples. POLYM. COMPOS., 2008. © 2008 Society of Plastics Engineers

Effect of interlayer structure, matrix viscosity and composition of a functionaiized polymer on the phase structure of polypropylene‐montmorillonite nanocomposites

AbstractPolypropylene (PP)‐clay composites were prepared by melt mixing in an intensive mixer. Three grades of PPs with different melt viscosities were employed to investigate mixing characteristics and phase structure of the composites with various clays that belong to organically modified montmorillonite (org‐MMT). Depending on the matrix viscosity and nature of the organic layer in MMT, significant variations In the phase structure of the composites were found. In addition to the simple combination of PP and clay, various functionalized PPs were also incorporated in an attempt to enhance thermodynamic interaction between the org‐MMT and PP matrix. Major interest was focused on the effect of varying thermodynamic affinity between the components, on the phase evolution and mechanical properties of the composites. Within the available range of maleic anhydride (MA) content in PP, it was found that optimum content of the functional group exists, which balances favorable interaction with org MMT and tolerable homogeneity with PP matrix. Along with keeping the optimum MA content, it was also important to use a low viscosity PP matrix to achieve a mere random array of layered silicates. The observed phase structure was interpreted by using a model based on self consistent field theory.

Morphology and mechanical properties of direct injection molded polypropylene/thermotropic copolyester blends

AbstractBlends of two grades of polypropylene (PP) with thermotropic copolyester (Rodrun) contents of up to 40% were obtained by direct injection molding at different processing temperatures. In the skin of the molded specimens rather long fibers were seen in blends with low‐viscosity PP, whereas sheets were found when the high‐viscosity PP was the matrix. In the core, the viscosity of the matrix played a more relevant role than the viscosity ratio on the orientation level of the dispersed Rodrun phase. The better mechanical properties of the blends with the low viscosity PP are attributed to the morphology change of the dispersed phase from sheets to fibers when the viscosity of the matrix decreased.

高分子材料 ポリプロピレン‐ポリテトラフルオロエチレンブレンド系の溶融特性と発泡特性

Polypropylene (PP) has a wide range of application because of its high stiffness and high heat resistance. PP is, however, not suitable for extrusion foaming process, because the cells of PP have low resistance to rupture during expansion.In order to give good processability to PP under extrusion foaming, PP is blended with polytetrafluoroethylene (PTFE). PTFE turns into many thin fibers during the mixing process, and these fibers may increase the resistance to rupture. Various samples of the blends were prepared by using three PP's with different viscosity values (melt index=0.4, 7.0 and 20) and various amounts of PTFE. As the indicators of the processability, the melt tension and the crystallization temperature of the blends were measured. The melt tension of the blends increased with PTFE content. The crystallization temperature also increased with PTFE content, especially when the PP with high viscosity was used.The extrusion foaming process of these blends was studied by using a tandem extruder. It was found that the blends of low viscosity PP can be successfully made into foamed products. The expansion ratio of the products increased with PTFE content. However, the size of the cells in the foamed products had a wide distribution, and the volume fraction of the closed cells decreased with PTFE content. These problems of wide cell size distribution and low content of closed cell may be caused by the inhomogeneous distribution of PTFE fibers in the PP matrix.