Melt Flow Properties Research Articles

Polyamide 66 nanocomposites based on organoclays treated with thermally stable phosphonium salts

AbstractPurification of bentonite clays and their modification with two thermally stable (alkyl and aryl) phosphonium organic salts were investigated. The organoclays were subsequently melt compounded with Polyamide 66 (PA66), with and without the use of an elastomeric compatibilizer. The morphology, melt flow, thermal stability, and mechanical properties of the binary and ternary nanocomposites were studied. The bentonite clay was purified by sedimentation, resulting in higher cation exchange capacity and thermal stability in comparison with unpurified clay. These were then used in the synthesis of two thermally stable organoclays by replacing the interlayer sodium cations with two (alkyl and aryl) phosphonium surfactant cations to circumvent the problem of low temperature decomposition of quaternary ammonium organoclays usually used in polymer nanocomposites. The organoclay with aliphatic groups showed more compatibility with PA66 in comparison with the organoclay with aromatic groups. Thus, the use of organoclay with aliphatic groups resulted in nanocomposites with higher tensile strength, higher modulus, higher elongation at break, and higher impact strength in comparison with the nanocomposites produced from the organoclay with aromatic groups. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013

Rheological behavior of chlorosulfonated polyethylene composites: Effect of filler and plasticizer

AbstractThe rheological properties of chlorosulfonated polyethylene (CSM) loaded with conductive carbon black filler were measured using capillary rheometer at three different temperatures (110, 120, and 130°C) and four different shear rates (12.26, 24.52, 61.3, and 122.6 s−1). The effect of filler and plasticizer [dioctyl phthalate (DOP)] loading on melt flow properties of CSM was also studied. The viscosities of all samples decrease with shear rate indicating their pseudoplastic or shear thinning nature. The higher shear viscosity is observed for the CSM loaded with higher filler content, which may be due to inhibition of the polymer chain motion by the filler particles. With increasing filler loading the extrudate swell clearly decreased, which is attributed to the limitation of the elastic recovery of the polymer chains by filler particulates. Further, the reduction in die‐swell ratio with increase in plasticizer loading indicates a reduction in melt elasticity compared with the composite containing no DOP. The dependence of shear viscosity on temperature obeyed the Arrhenius–Eyring expression, and the activation energy (Eγ) decreased with increasing shear rate. Extrudate swell is a non‐linear function of shear rate. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012

Tailoring the ionic association and microstructure of ionomers with various metal salts

AbstractIn this work, we investigated the effects of metal stearate salts on the structure, morphology, and properties of poly(ethylene–acrylic acid) neutralized by zinc salts (PI). The samples were characterized in detail with spectroscopic [Fourier transform infrared (FTIR) spectroscopy], microscopic (hot‐stage optical microscopy), thermal [thermogravimetric analysis, modulated differential scanning calorimetry, and dynamic mechanical analysis], mechanical, and scattering (small‐angle neutron scattering and small‐angle X‐ray scattering) techniques. The melt rheological properties of the samples were also investigated. The structure of the ionic domains was determined by the type of cations and the salt proportion (FTIR). The predominant interaction was found to exist between the metal stearate and the ionic group. Na+ cation exhibited a unique behavior, whereas Zn2+ showed a coordinated structure and, hence, properties. The ionic groups in the Na and Zn stearate systems existed as multiplets and clusters, but multiplets were the main structure in the Al salt system. The salts acted as plasticizers above their melting points (mp's) but as fillers below their mp's. The melt flow properties of PI were significantly affected by the metal cation and salt proportion and were improved greatly by the introduction of the salts. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012

In Silico Molecular Design, Synthesis, Characterization, and Rheology of Dendritically Branched Polymers: Closing the Design Loop.

It has been a long held ambition of both industry and academia to understand the relationship between the often complex molecular architecture of polymer chains and their melt flow properties, with the goal of building robust theoretical models to predict their rheology. The established key to this is the use of well-defined, model polymers, homogeneous in chain length and architecture. We describe here for the first time, the in silico design, synthesis, and characterization of an architecturally complex, branched polymer with the optimal rheological properties for such structure-property correlation studies. Moreover, we demonstrate unequivocally the need for accurate characterization using temperature gradient interaction chromatography (TGIC), which reveals the presence of heterogeneities in the molecular structure that are undetectable by size exclusion chromatography (SEC). Experimental rheology exposes the rich pattern of relaxation dynamics associated with branched polymers, but the ultimate test is, of course, did the theoretical (design) model accurately predict the rheological properties of the synthesized model branched polymer? Rarely, if ever before, has such a combination of theory, synthesis, characterization, and analysis resulted in a "yes", expressed without doubt or qualification.

Preparation of polystyrene colloid particles armored by clay platelets via dispersion polymerization

Polystyrene colloid particles armored by Montmorillonite clay (MMT) were prepared by free-radical polymerization in dispersion. MMT was pre-modified with cationic amphiphilic block copolymer of poly(styrene-b-2-hydroxyethyl acrylate) (PS-b-PHEA), and the obtained (PS-b-PHEA)-MMT modified clay was used as stabilizer in dispersion polymerization. The impact of (PS-b-PHEA)-MMT loading on the particle size, the monomer conversion, and on the molecular weight were investigated. The main objective of this paper was to use the clay platelets as stabilizers in dispersion polymerization, and as nanofiller to improve some polymer properties such as thermal stability, thermo-mechanical and melt flow properties. Transmission electron microscopy (TEM) showed that colloid PS particles with MMT layers at the surface (i.e. armored particles) were obtained, and the particles sizes were found to be in the micrometer size range and stable dispersion were obtained for clay loadings up to 5wt%. Small angle X-ray diffractions (XRD) and TEM revealed that polymer-clay nanocomposites (PCNs) with partially exfoliated structures were obtained for low clay loading, while intercalated structures were obtained at higher clay loading. All PCNs were found to be more thermally stable than neat polymer as were determined by TGA. Furthermore, an increase in the storage modulus and the Tg of the PCNs was found and greatly correlated to the clay loading.

Thermal Analyses of Blends of Hyperbranched Linear Low-density Polyethylene (LLDPE) with High-density Polyethylene and LLDPE Prepared by Dissolving Method

Blends of high-density polyethylene (HDPE), moderate and hyper-branched LLDPEs (LLDPE and HbPE, respectively) have attained widespread commercial applications, though the understanding of the mechanical and melt-flow properties of such blends has been handicapped by the absence of a consensus concerning the degrees of mixing of the components. Moreover, usually the blends are obtained by melt blending, which may not ensure the initial homogeneity of the components. In our work the mixtures were prepared by dissolving the conventional LLDPE having branching content 7.2 wt% with HbPE with comonomer content 17.8 wt% in xylene at 130 °C and stirring for 2 hours. The same procedure was applied for the blending of HDPE with HbPE. After dissolving the mixtures were cooled in liquid nitrogen and after that freeze dried in vacuum line. The ratio of components in the blends was varied. Differential scanning calorimetry has been used to investigate the miscibility and thermal behavior of the blends. For this purpose isothermal and non-isothermal treatment of prepared blends were conducted. By preliminary study the double melting peaks in non-isothermal endotherms have been observed in all the studied blends. The presence of two peaks in DSC scan can be attributed to the formation of separated crystals from both the high density/linear low density and highly branched components. However, certain limited degree of co-crystallization is detected in all the LLDPE/HbPE blends and HDPE/HbPE blend rich in HbPE component.http://dx.doi.org/10.5755/j01.ms.17.3.589

Experimental and numerical analysis of the temperature distribution of injection molded products using protruding microprobes

Injection molding has been one of the most important polymer processing methods for manufacturing plastic parts. In the process, the temperature is an important parameter that influences process features such as cycle times, crystallization rates, degree of crystallinity, melt flow properties, and molded product qualities. This study aims to, experimentally and numerically, examine the three-dimensional temperature distribution along the melt flow path of injection molded parts. A special experimental set-up, which includes an injection mold equipped with protruding microprobes for guiding embedded thermocouples, was designed and built to measure the temperature field along the flow path, i.e., inside the runner and the cavity, of injection molded products. The experimental results suggested that the disturbance induced by the probes remained negligible and precise temperature profiles could be measured at various positions inside the cavity. A significant increase of melt temperature was found to result from the viscous dissipation of the polymeric materials in the runner. Additionally, a commercially available code was employed to simulate and predict the temperature variation in injection molded parts. It was shown that the numerical simulation predicted better the temperature distributions inside the cavity than those along the runner.

Melt-compounded nanocomposites of titanium dioxide atomic-layer-deposition-coated polyamide and polystyrene powders

Polyamide and polystyrene particles were coated with titanium dioxide films by atomic layer deposition (ALD) and then melt-compounded to form polymer nanocomposites. The rheological properties of the ALD-created nanocomposite materials were characterized with a melt flow indexer, a melt flow spiral mould, and a rotational rheometer. The results suggest that the melt flow properties of polyamide nanocomposites were markedly better than those of pure polyamide and polystyrene nanocomposites. Such behavior was shown to originate in an uncontrollable decrease in the polyamide molecular weight, likely affected by a high thin-film impurity content, as shown in gel permeation chromatography (GPC) and scanning electron microscope (SEM) equipped with an energy-dispersive spectrometer. Transmission electron microscope image showed that a thin film grew on both studied polymer particles, and that subsequent melt-compounding was successful, producing well dispersed ribbon-like titanium dioxide with the titanium dioxide filler content ranging from 0.06 to 1.12wt%. Even though we used nanofillers with a high aspect ratio, they had only a minor effect on the tensile and flexural properties of the polystyrene nanocomposites. The mechanical behavior of polyamide nanocomposites was more complex because of the molecular weight degradation. Our approach here to form polymeric nanocomposites is one way to tailor ceramic nanofillers and form homogenous polymer nanocomposites with minimal work-related risks in handling powder form nanofillers. However, further research is needed to gauge the commercial potential of ALD-created nanocomposite materials.

Processing stability of polypropylene impact-copolymer during multiple extrusion – Effect of polymerization technology

Three commercially available polypropylene impact-copolymers (ICPP) produced by Innovene (INN), Spheripol (SPH) and Unipol (UNI) technologies were subjected to multiple extrusion using a twin-screw extruder W&P ZSK25 at 220 °C. Processing stability and changes in properties induced by extrusion were investigated. The materials were of similar MFR ∼6 dg/min, similar ethylene contents ∼7.5 wt. % and the same type and level 1200 ppm of phenol/phosphite stabilizer system was used. Ranking INN < UNI < SPH in processing and long-term (LTHA) stabilities observed was primarily related to the reactivity of catalyst residues rather than to other factors, such as contents of ethylene, quantity of extractables, EPR phase composition, levels of ash or individual elements in it. The mechanically demanding multiple extrusion conditions and consequently different extent of processing degradation, however, induced only minimum changes in morphology and impact strength of the solid ICPP matrix. Thus, regardless of changes in melt-flow properties induced by extrusions, all the three grades even after 5th extrusion at 220 °C exhibited Charpy notched impact strength at 23 °C only minimally changed.

Renewable Resource-Based Composites of Acorn Powder and Polylactide Bio-Plastic: Preparation and Properties Evaluation

Renewable resource-based composites were prepared with acorn powder and Thermoplastic resin poly(lactic acid) (PLA) by twin-screw extrusion followed by injection molding processing or hot-compression molding processing. The study of the composites microstructure showed poor adhesion between acorn powder and PLA matrix. The hygroscopicity, mechanical properties and melt flow property of composites were promising even though the composites had a 70 wt% content of acorn powder. Silane coupling agent, 4,4′-Methylenebis (phenyl isocyanate) and PLA grafted with maleic anhydride did not show obvious effect on mechanical properties of composites. The impact resistance strength of reinforced composites with steel fiber webs were improved greatly in comparison with those having no steel fiber webs. Thermal properties results of DSC and DMA showed that the presence of acorn powder significantly affected the crystallinity, crystallization temperature (Tc), glass transition temperature (Tg) and melting temperature (Tm) of PLA matrix. The study results proved that composites had superior mechanical properties, enough to partially replace the conventional thermoplastic plastics.

Plasticization of poly(arylene ether nitrile) by the melt blending of phthalonitrile prepolymer: A rheological, mechanical, and thermal study

AbstractPoly(arylene ether nitrile) (PEN)/phthalonitrile prepolymer (PNP) blends were prepared via a melt‐mixing process. The melt flow properties, compatibility, and thermal and mechanical properties were characterized by dynamic rheological testing, dynamic mechanical analysis, tensile testing, thermal analysis, and fracture surface morphology observation. The melt‐mixed PEN/PNP blends displayed excellent melt flow properties during processing. When the PNP content in PEN was increased, the viscosity of the blends decreased considerably. Compared with that of pure PEN, the dynamic complex viscosity of the PEN/PNP blend with an 11% addition of PNP dropped sharply from 7000 to 2000 Pa s at 350°C and a frequency of 10 Hz. The dynamic mechanical analysis and differential scanning calorimetry results showed good compatibility between PEN and PNP. Observations of the morphology of the fractured surfaces revealed better component dispersion in which PNP was dissolved in the PEN matrix. Importantly for further commercial applications, the blending materials maintained the characteristic thermal and thermooxidative stability and mechanical properties of PEN. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010

Research on the Polymer Ultrasonic Plastification

Melt flow properties in micro cavity play an important role in the micro injection molding (MIM). Based on the point view of improving the melting plastification quality, this study focus on solving the problem of melt filling difficulty in micro cavity of MIM by introducing the ultrasonic vibration field into the polymer plastification process. This paper studied the polymer’s ultrasonic plasitfication process by Theoretical analysis and Polymer ultrasonic plastification experiment.

Biosynthesis of polylactic acid and its copolymers using evolved propionate CoA transferase and PHA synthase

For the synthesis of polylactic acid (PLA) and its copolymers by one-step fermentation process, heterologous pathways involving Clostridium propionicum propionate CoA transferase (Pct(Cp)) and Pseudomonas sp. MBEL 6-19 polyhydroxyalkanoate (PHA) synthase 1 (PhaC1(Ps6-19)) were introduced into Escherichia coli for the generation of lactyl-CoA endogenously and incorporation of lactyl-CoA into the polymer, respectively. Since the wild-type PhaC1(Ps6-19) did not efficiently accept lactyl-CoA as a substrate, site directed mutagenesis as well as saturation mutagenesis were performed to improve the enzyme. The wild-type Pct(Cp) was not able to efficiently convert lactate to lactyl-CoA and was found to exert inhibitory effect on cell growth, random mutagenesis by error-prone PCR was carried out. By employing engineered PhaC1(Ps6-19) and Pct(Cp), poly(3-hydroxybutyrate-co-lactate), P(3HB-co-LA), containing 20-49 mol% lactate could be produced up to 62 wt% from glucose and 3HB. By controlling the 3HB concentration in the medium, PLA homopolymer and P(3HB-co-LA) containing lactate as a major monomer unit could be synthesized. Also, P(3HB-co-LA) copolymers containing various lactate fractions could be produced from glucose alone by introducing the Cupriavidus necator beta-ketothiolase and acetoacetyl-CoA reductase genes. Fed-batch cultures were performed to produce P(3HB-co-LA) copolymers having 9-64 mol% of lactate, and their molecular weights, thermal properties, and melt flow properties were determined.

Research into Melt Flow Properties of Polypropylene/Diatomite Composites

Polypropylene (PP) filled with diatomite particles was manufactured using a twinscrew extruder. Melt volume flow rate (MVR) is an important parameter for characterization of flow properties of polymer. The MVR of the PP/diatomite composites was measured by means of a melt flow rate instrument to investigate the effects of die diameter and extrusion conditions (temperature 210—230°C, load 5.0—12.5 kg) on the melt flow properties of the composite systems. The results showed that the MVR of the composites increased as a quadratic function with the increase of the die diameter, while it decreased with increase of particle size; the MVR was a linear function of temperature when the die diameter and load was constant; and the MVR was also a quadratic function of the die diameter when load and temperature were fixed. In addition, the effects of load, temperature, and particle size on the MVR was enhanced with an increase in the die diameter.

Melt Rheology during Extrusion of Polypropylene Composites Filled with Diatomite Particles

The melt volume flow rate (MVR) is an important parameter for characterization of flow properties of polymer. The MVR of the polypropylene composites filled with diatomite particles was measured by means of a MVR instrument to investigate the effects of the filler content, particle size and extrusion conditions (temperature 210—230°C, load 5.0—12.5 kg) on the melt flow properties of the composite systems. The results showed that the MVR of the composites increased as a quadratic function with the increase of load, while decreased nonlinearly with the increase of filler particle diameter. The MVR was a linear function of temperature. The MVR decreased quickly when the filler volume fraction (φf) was &lt;5%, and then reduced slightly with an increase of φf. In addition, the melt shear flow obeyed roughly power law under the experimental conditions, and the influence of particle size on the temperature sensitivity of the melt shear viscosity is insignificant at low filler concentration.

In-situ temperature measurements in the depths of injection molded parts

Injection molding has been the most widely used polymer processing method for manufacturing plastic parts. In the process, the temperature is an important parameter that influences process features such as cycle times, crystallization rates, degree of crystallinity, melt flow properties and molded product qualities. This report proposed a special experimental set-up, which includes an injection mold equipped with tubular needles for guiding embedded thermocouples, to measure the temperature field inside the cavity. It was found that the disturbance induced by the probes remained negligible and precise temperature profiles could be measured at various positions inside the cavity. Viscous dissipation of the polymeric materials in the runners resulted in a significant increase of melt temperature. Additionally, a transient heat transfer finite element model was proposed to simulate and predict the temperature variation in injection molded products. It was shown that the numerical prediction coincided satisfactorily with the measured temperature data.

Melt Flow and Mechanical Properties of Silica/Perfluoropolymer Nanocomposites Fabricated by Direct Melt-Compounding without Surface Modification on Nano-Silica

The authors have previously developed a novel method for the fabrication of silica/perfluoropolymer nanocomposites, wherein nano-sized silica particles without surface modification were dispersed uniformly through breakdown of loosely packed agglomerates of silica nanoparticles with low fracture strength in a polymer melt during direct melt-compounding. The method consists of two stages; the first stage involves preparation of the loose silica agglomerate, and the second stage involves melt-compounding of a completely hydrophobic perfluoropolymer, PFA (poly(tetrafluoroethylene-co-perfluoropropylvinylether)), with the loose silica agglomerates. By using this simple method without any lipophilic treatment of the silica surfaces, silica nanoparticles with a primary diameter of 190 nm could be dispersed uniformly into the PFA matrix. The main purpose of the present study is to evaluate the melt flow and tensile properties of silica/PFA nanocomposites fabricated by the above method. In order to elucidate the effects of the size of the dispersed silica in the PFA matrix on the properties of the composites, silica/PFA composite samples exhibiting the dispersion of larger-sized silica particle-clusters were fabricated as negative controls of the silica dispersion state. The results obtained under the present experimental conditions showed that the size of the dispersed silica in the PFA matrix exerts a strong influence on the ultimate tensile properties, such as tensile strength and elongation at break, and the melt flow rate (MFR) of the composite materials. The MFR of the silica/PFA nanocomposite became higher than that of the pure PFA without silica addition, although the MFR of the PFA composites containing larger silica particle-clusters became much lower than that of the pure PFA. Furthermore, uniform dispersion of isolated silica nanoparticles was found to improve not only the Young's modulus but also the ultimate tensile properties of the composite.

Melt Flow Instabilities of Wood Polymer Composites

Melt flow instabilities during extrusion of wood polymer composites (WPC) containing 30–60 wt% wood flour (WF) have been investigated. The research emphasized elucidation of the extrudate surface tearing mechanism and its relation to wall slip. This interesting phenomenon has been known in the WPC industry for years; however, it has not received much research interest. It was observed that increasing the wood flour loading up to 50 wt% aggravated the surface tearing; however, addition of 60 wt% wood flour completely eliminated the surface defect due to strong wall slip and plug flow. It was also found that addition of lubricants and increasing the shear rate significantly improved the surface appearance of the filled compounds. Molecular weight and molecular weight distribution of the polymer matrix influence the melt flow properties of the composites. The significance of the entrance pressure measurement and its usefulness for quantitative assessment of filler–matrix interactions in composite materials is also demonstrated in this paper.

The Effect of Melt Vibration on Polystyrene Melt Flowing Behavior During Extrusion

Vibration extrusion (VE) is achieved by superimposing a mechanical vibration on the flowing melt during extrusion. The effect of melt vibration on the melt flow behavior of polystyrene (PS) was studied. The melt flow behavior during conventional extrusion (CE) was studied for comparison. With the application of the melt vibration technology, the melt flow behavior of PS was greatly improved. The melt viscosity during the VE strongly depends on the vibration frequency and vibration amplitude. Extruded at constant vibration amplitude, the melt viscosity decreases sharply with increasing vibration frequency and also does so for increasing vibration amplitude when extruded at a constant vibration frequency. The improved melt flow property is explained in terms of shear-thinning criteria. The effect of melt vibration on the melt flow behavior is also related to the melt temperature and extrusion pressure; the greatest decease in viscosity is obtained at low temperature and low extrusion pressure.

Effect of silica type and concentrations on the physical properties of EPDM cured by γ -irradiation

This paper reports the results of studies on the thermal and electrical properties of gamma radiation cured composites based on ethylene propylene dieyne rubber (EPDM) reinforced with different concentrations of micro- and nano-silica. The effect of gamma irradiation in the presence of ethylene glycol dimethacrylate (EGDM) as radiation sensitizer on melt flow properties of EPDM was also studied. Thermogravimetric studies of the composites show that the degradation of vulcanizates is controlled mainly by the silica type and its concentration. Increasing the amount of micro- or nano-silica in the vulcanizate decreases the maximum rate of decomposition of the major degradation step compared with that of the unfilled-cured one. The micro- and nano-composites exhibited remarkable heat resistance properties compared with that of the pure EPDM as the filler dispersion of silica inhibited the thermal degradation of the polymeric matrix, which led to the micro and nano-composites showing great improvement in thermal stability. A considerable change in decomposition rate is observed by increasing filler loading from 10 to 39 phr. The dielectric properties of such composites are affected by the silica type and concentration. The dielectric constant and ac-conductivity for all composites were found to increase with increasing silica loading, which is mainly due to the interfacial polarization. The ac-conductivity values of silica/EPDM composites exhibit a strong frequency dependence with both fillers used. The conductance and dielectric constant values have been fitted using a conduction model for all samples.