In this study, high hoop tensile strength and toughness polypropylene random copolymer (PPR) pipes were successfully prepared through rotation extrusion and synergistic effect of self-assembling nucleating agent (TMB-5) and crystallization promoter (isotactic polypropylene, iPP). The result indicated low temperature toughness of PPR pipes could be improved by incorporating TMB-5 and iPP, as the result of highly improved PPR crystallization capability and abundant β-form crystal production. Both molecular chains and anisotropic crystallites deviated off the axial direction due to the hoop stress generated by rotation extrusion, leading to increased hoop orientation and pronouncing enhancement in hoop strength. Accordingly, the hoop tensile strength and impact strength of the modified PPR pipe reached 28.9MPa and 5.7kJ/m2, increased by 126% and 43% compared to the convention-extruded PPR pipe. POLYM. ENG. SCI., 56:866–873, 2016. © 2016 Society of Plastics Engineers
This article is the first study on the microinjection molding and the effects of the microprocessing parameters on the crystallization and orientation of polyoxymethylene/poly(ethylene oxide) (POM/PEO) blend, which has better toughness and self-lubricity compared with the neat POM and therefore is a better candidate material for making microparts like microgears with higher performances. The crystalline and phase morphologies were investigated by polarized light microscope (PLM), differential scanning calorimeter (DSC) and scanning electron microscope (SEM). The crystalline orientation of the microparts was evaluated by two-dimensional wide-angle X-ray diffraction (2D-WAXD) and Herman's orientation function. The experimental results showed that both POM and POM/PEO microparts prepared by microinjection molding exhibited three distinct layers, i.e., skin layer, shear layer and core layer, while the latter had thicker shear layer but thinner skin layer and core layer. PEO was well dispersed in POM matrix. The spherulite size, the melting point as well as the crystallinity of POM in the POM/PEO blend decreased due to the interference of PEO in the crystallization of POM. A shish-kebab structure was observed in the shear layers of the POM/PEO microparts. The effects of processing parameters on the thicknesses of different layers of the POM/PEO microparts were investigated. With increase of the injection speed or decrease of the mold temperature, the skin layer and the core layer became thicker, while the shear layer and the oriented region became thinner. However, the influence of the injection pressure was not obvious. Also, the processing parameters affected the crystalline orientation of the POM/PEO microparts. With increase of the injection speed or decrease of the mold temperature, the orientation function f decreased, indicating a lower degree of orientation. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 40538.
Poly(vinyl alcohol)/melamine phosphate composites (PVA/MP) as a novel halogen-free, flame-retardant foam matrix were prepared through thermal processing, and then their thermal stability and flame retardancy were investigated by thermo-gravimetric analysis, micro-scale combustion calorimeter, cone calorimeter, vertical burning test, and limiting oxygen index (LOI) test. It was found that the thermal stability and combustion properties of the PVA/MP composites could be influenced by the addition of MP. Compared with the control PVA sample (B-PVA), in the PVA/MP (75/25) composites, the temperature at 5% mass loss (T5%) decreased about 10°C, the residual chars at 600°C increased by nearly 27%, the temperature at the maximum peak heat release rate (TP) shifted from 292°C to 452°C, and the total heat released and the heat release capacity (HRC) decreased by 28% and 14%, respectively. Moreover, the PVA/MP composites could reach LOI value up to 35% and UL94 classification V-0, showing good flame retardancy. At the same time, both Fourier transform infrared and X-ray photoelectron spectroscopy spectra of the residual chars from the PVA/MP composites demonstrated that the catalytic effect of MP on the dehydration and decarboxylation reactions of PVA, and the chemical reactivity of MP during the chars-forming reactions could be used to account for the changed thermal stability and flame retardancy of the PVA/MP composites. Copyright © 2012 John Wiley & Sons, Ltd.
Highly filled poly(vinyl alcohol) (PVA) composites, PVA/talc and PVA/CaCO3, were successfully prepared through melt-processing technology without use of coupling agents or compatibilizers. Morphology analysis showed that both of the two fillers well dispersed in PVA matrix. Differently, the flaky talc obviously oriented, while the particulate CaCO3 was randomly scattered in PVA matrix. Rheological analysis showed that the two filled systems exhibited a common shear-thinning phenomenon, confirming their pseudoplastic nature. Compared with the particulate CaCO3, the flaky talc exhibited a closer arrangement in the composite, resulting in a lower threshold filler content to form the network structure. Therefore, PVA/talc composite showed higher melt viscosity and lower extrudate-swell ratio. The orientation of the flaky talc particles in the system also resulted in the higher melting and heat-deflection temperatures, as well as a greater reinforcement effect on the composite, but a lower elongation at break. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 3050–3057, 2013
The drawability of melt-spun poly(vinyl alcohol) (PVA) fibers and its structure evolution during hot-drawing process were studied by differential scanning calorimetry (DSC), two dimensional X-ray diffraction (2-D WAXD) and dynamic mechanical analysis (DMA). The results showed that the water content of PVA fibers should be controlled before hot-drawing and the proper drying condition was drying at 200°C for 3 min. PVA fibers with excellent mechanical properties could be obtained by drawing at 200°C and 100 mm/min. The melt point and crystallinity of PVA fibers increased with the draw ratio increasing. The 2-D WAXD patterns of PVA fibers changed from circular scattering pattern to sharp diffraction point, confirming the change of PVA fibers from random orientation to high degree orientation. Accordingly, the tensile strength of PVA fibers enhanced by hot-drawing, reaching 1.85 GPa when the draw ratio was 16. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012
A novel rotation extrusion processing system was self-designed to prepare high-performance polyethylene (PE) pipes. In this study, during the extrusion of the PE pipes at a high mandrel rotation speed, compressed air, as a cooling medium, was introduced through their interior to achieve the quick cooling of the inner wall and the effects of the inner wall cooling rate on the microstructure and mechanical properties of the obtained PE pipes were investigated. The experimental results showed that in contrast to conventional extrusion, the molecular orientation deviated from the axial direction under a high mandrel rotation speed and was fixed by the inner wall cooling; with increasing cooling rate, the orientation degree also increased. On the other hand, cooling promoted the augmentation of spherulites. So when the cooling rate reached a certain high point, the effect of cooling on the formation of spherulites was stronger than that on the fixation of the orientation. A much higher cooling rate decreased the orientation degree, which was closely related to the performance of the PE pipe. As a result, there was an optimal cooling rate of the inner wall during the rotation extrusion for better performance of the PE pipe. When the cooling rate was 1.5°C/s, the hoop strength of the PE pipe produced by the novel extrusion method increased from the original 24.1 MPa up to 37.1 MPa without a decrease in the axial strength, and the pipe's crack initiation time increased from 27 to 70 h. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011
In this article, macromolecular charring agent linear novolac (NA) was served as a synergist with nitrogen-phosphorous flame retardant melamine polyphosphate (MPP) for the flame-resistance of wollastonite (WT) filled polyamide 66 (PA66). The investigations showed that MPP/NA system possessed obvious synergistic effects by increasing the charring rate and amount, therefore, showing much higher flame retardancy than the filled PA66 flame retarded with MPP alone. The corresponding char layer structure of MPP/WT/PA66 and MPP/NA/WT/PA66 was investigated and their difference was analyzed. In addition, as a multifunctional additive, NA could act as a compatibilizer and lubricant in the system, and endowed the material with improved mechanical performance and processability. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010
In this study, natural rubber (NR) nanocomposites based on carbon black (CB) and two poly(ethylene glycol) (PEG)-modified clay hybrid filler were fabricated. The morphology and mechanical properties were studied. The dynamic properties of NR vulcanizates were investigated over a range of strain amplitude at two temperatures. It was found that NR with hybrid filler exhibits superior mechanical properties over that with CB as single phase filler. The hybrid filler causes a significant alteration in the dynamic properties of rubber. The Payne effect becomes more pronounced in rubber with modified clay. A decrease in loss factor (tanδ) was observed for rubber with hybrid filler also. The results revealed that the inclusion of nanoclay (NC) could induce a stronger and more developed filler network. Because of the anisotropy of the nanolayers, NC would depress the reconstruction of filler network, or lower the reformation rates when broken down under deformation, giving rise to lower tanδ value at broad temperature range as well as strain amplitude. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010
To improve the drawability of poly(vinyl alcohol) (PVA) thermal products, poly(ethylene oxide) (PEO), a special resin with good flexibility, excellent lubricity, and compatibility with many resins, was applied, and the Fourier transform infrared spectroscopy, dynamic mechanical analysis (DMA), differential scanning calorimetry (DSC), and wide-angle X-ray diffraction (WXRD) were adopted to study the hydrogen bonds, water states, thermal properties, crystal structure, and nonisothermal crystallization of modified PVA. It was found that PEO formed strong hydrogen bonds with water and PVA, thus weakened the intra- and inter-hydrogen bonds of PVA, changed the aggregation states of PVA chains, and decreased its melting point and crystallinity. Moreover, the interactions among PVA, water, and PEO retarded the water evaporation and made more water remain in the system to plasticize PVA. The existence of PEO also slowed down the melt crystallization process of PVA, however, increased the nucleation points of system, thus made more and smaller spherulites formed. The weakened crystallization capability of PVA and the lubrication of PEO made PVA chains to have more mobility under the outside force and obtain high mechanical properties. © 2010 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 48: 1946–1954, 2010
During the rotation extrusion of polyethylene (PE) pipes, with the rotating mandrel, compressed air as a cooling medium was introduced through their interior to achieve the quick cooling of the inner wall. The experimental results showed that the hoop stress exerted by mandrel rotation could promote the molecular orientation in the hoop direction; moreover, the introduction of compressed air could quicken its inner wall's cooling rate so as to slow down the relaxation of the oriented molecule and to reserve the orientation structure. Therefore, the hoop orientation degree increased with the increasing inner wall's cooling rate. As a result, the performance of the PE pipe was greatly enhanced. The hoop tensile strength of the PE pipe produced by the novel extrusion method increased from original 24.1 MPa up to 35 MPa; the pipe's crack initiation time increased from 27 to 60 h and the crack growth rate slowed down. POLYM. ENG. SCI., 50:1743–1750, 2010. © 2010 Society of Plastics Engineers
Poly(vinyl alcohol) (PVA) is an important water-soluble polymer. Its many applications (e.g., textile sizing, dispersants, and adhesives) greatly depend on its water solubility and particularly on its dissolution rate in water. In this study, urea, combined with methanol, was adopted to improve the water solubility of PVA. The structures, properties, and dissolving mechanism of the modified PVA were studied with Fourier transform infrared spectroscopy, NMR, laser light scattering, differential scanning calorimetry, and wide-angle X-ray diffraction. The results showed that through specific chemical reactions between PVA and urea in methanol, isocyanate and methyl carbamate groups were generated on the lateral chains of PVA. These large side groups could effectively expand PVA macromolecular chains and hence increase their intermolecular distance, weaken the intramolecular and intermolecular hydrogen bonds of PVA, change the aggregation structure of PVA, and decrease its lattice energy and crystallinity. In addition, the isocyanate groups on the PVA macromolecular chains strongly interacted with water. All these effects benefited the water solubility of PVA. Therefore, the dissolution rate of the modified PVA increased by 50% versus that of the neat PVA, and the quality of the modified PVA aqueous solution was improved quite a bit. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009
BACKGROUND: Water-plasticized poly(vinyl alcohol) has been obtained by thermal processing. Dehydration is the key process for controlling the structure and performance of the water-soluble polymer, and mass transfer is an important part of dehydration.
RESULTS: A simple new model of a hyperbolic-type function was developed to understand the mass transfer process of water-plasticized poly(vinyl alcohol) systems during isothermal dehydration. The model was verified by statistical tests. The physical parameters in the model were defined as the maximum weight loss fraction and characteristic time. The dehydration rate, the key physical parameter in mass transfer, was obtained from the differential equation of the model. By use of the model, the characteristics of dehydration of poly(vinyl alcohol) were determined: the complete mass transfer process can be divided into a fast mass transfer before a characteristic time (τ) and a slow mass transfer after τ, and dehydration temperatures can also be divided into two intervals by different activation energies. In addition, the dehydration rate is inversely proportional to the degree of crystallinity.
CONCLUSION: The results of the new model agree reasonably well with experimental results obtained by thermogravimetry and weighing. Poly(vinyl alcohol), as a water-soluble semicrystalline polymer, exhibits a particular mass transfer behavior during dehydration. Copyright © 2008 Society of Chemical Industry
This article reported a novel technology, solid state shear milling (S3M), to prepare poly(ethylene terephthalate)/Na+-montmorillonite nanocomposites using the pristine Na+-MMT without organic modification so as to avoid the problem that the organic modifiers, used for MMT treatment will decompose at high processing temperature of PET, and the structure and properties of the obtained samples were investigated. XRD and TEM analyses showed that Na+-MMT layers were partially delaminated and intercalated, and uniformly dispersed in the PET matrix when suffering from the strong three dimensional shearing forces of pan-milling. DSC analysis showed that Na+-MMT serves as a nucleating agent, increasing the crystallization rate as well as the crystallization temperature of PET. The properties such as thermal stability and tensile strength of the PET/Na+-MMT nanocomposites prepared by S3M got remarkably improved. Solid state shear milling (S3M) method was a simple and efficient method to get polymer/Na+-MMT nanocomposites with pretty good performances without organic modification of pristine Na+-MMT. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 807–817, 2008
In this paper, a novel intumescent system including MP as well as PER/TPU which acts as composite charring agent, is adopted to flame-retarded PP. The encapsulation of charring agent PER by TPU effectively avoids the reaction of PER with MP during the compounding with PP at high temperature and also prevents the leaching out of polar PER from nonpolar PP matrix, thus remarkably enhancing the stability and water-resistance of the intumescent system. PER and TPU have different but complementary charring mechanisms. So flame-retarded PP with MP/composite charring agent shows a much better charring performance and flame-retardancy than MP/PER flame-retarded PP. The experimental results show that the former can reach UL-94 V-0 rating at 1.6 mm thickness at 25 wt.-% flame retardant loading.
Melamine polyphosphate and thermal-plastic polyurethane (TPU)-encapsulated solid acid were applied for flame retardant glass fibers reinforced polyamide 6 (GFPA6). The introduction of TPU would change the interfacial property between glass fibers (GFs) and polyamide 6 (PA6), weakening the “candlewick effects” of GFs in PA6. Serving as a synergist, solid acid containing sulfur (CAS) played the role of a strong acid source, which could promote the system to form much more condensed and closed char layers. Macromolecular charring agent, TPU, was able to accelerate the charring process. In addition, TPU encapsulating on the unstable solid acid could isolate CAS from PA6 resin, preventing the chemical interaction between them, which would cause the degradation of material. This established technology provided an effective approach to prepare halogen-free flame retardant GFPA6 with UL94-1.6 mm V0 rating and good mechanical performance, showing a promise in the future commercial application. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007
Due to being halogen-free, non-toxic, non-erosive and environmentally friendly, melamine-based flame retardants are attracting more and more attention. As a melamine-based intumescent flame retardant, in this study the melamine salt of pentaerythritol phosphate (MPP) was prepared from melamine phosphate (MP) and pentaerythritol (PER). The reaction of MP with PER was then systematically investigated. The reaction product MPP was utilized to flame-retard polypropylene (PP). FT-IR, TGA and DSC were used to characterize MPP and also to investigate the reaction of MP and PER in depth. The experimental results show that MPP has good thermal stability and matched decomposition temperature with that of PP, making it suitable for flame retarding of PP. Also, MPP is melting-blendable due to its softening during the heating process. The structure of MPP at a MP:PER molar ratio of 2.0 was confirmed as the same to that of the product synthesized from phosphorus oxychloride, pentaerythritol and melamine. The reaction of MP with PER was greatly influenced by the MP:PER proportion, reaction temperature and reaction time, rather than the physical state of PER, and the reaction mechanism of MP with PER was proposed. The prepared flame-retarded polypropylene composite with 35 wt% intumescent flame-retardant MPP has a flame retarding level of 3.2 mm UL 94 V-0, tensile strength 27.0 MPa, Young's modulus 2442 MPa and Izod notched impact strength 3.8 kJ/m2. Copyright © 2007 John Wiley & Sons, Ltd.
In this study, ultrasonic irradiation and in situ emulsion polymerization were combined to prepare stable poly(methyl methacrylate-co-n-butyl acrylate) (P(MMA-BA))/carbon nanotubes (CNTs) composite emulsion, which solves the dispersion problem of CNTs in the latex. Two stages were adopted. In Stage I, ultrasonically initiated in situ emulsion polymerization was conducted to disperse CNTs and prepare the seed emulsion containing polymer coated CNTs. In Stage II, conventional in situ emulsion polymerization was conducted to further enhance the monomer conversion and solid content. The dispersion behavior of MWCNTs in aqueous solution under ultrasonic irradiation was investigated by spectrophotometry. The effects of CNTs content on the emulsion stability and mechanical properties of composite film were studied. The results suggest that in the composite emulsion the long CNTs with a diameter of 20–40 nm are separated and dispersed by the formed polymer latex nanoparticles with a size of 20–40 nm. The spherical polymer latex nanoparticles adhere to the wall of CNTs to form a structure like “grapes on the twig.” The smooth, uniform, and flexible polymer/CNTs composite films were prepared from the composite emulsion. The CNTs can be individually dispersed in P(MMA-BA)/CNTs composite film. Tensile tests suggest that with the increase in the CNTs content, the Young's modulus and the yield strength of the film increase. Only at 1 wt % CNTs, the Young's modulus increases from 124 to 289 MPa, and the yield strength is improved about ∼14%. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 3123–3130, 2006
A new method, solid state shear milling (S3M), was reported for realizing the exfoliation and layer expansion of vermiculite layer in solid state by using pan-mill equipment, which can exert fairly strong squeezing force and shearing force on milled materials. The mechanism was discussed. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 1806–1809, 2006
Ultrasonic irradiation is employed to assist the chemical oxidative polymerization of aniline in the presence of Fe3O4 nanoparticles in order to prepare a polyaniline (PANI)/Fe3O4 magnetic nanocomposite. In the chemical oxidative polymerization of aniline in the initially neutral medium, the optimum molar ratio of the oxidant ammonium persulfate to the monomer aniline is 2 : 1. The prepared PANI is in the emeraldine form and is doped by sulfate anions. Fe3O4 particles are encapsulated by PANI and dispersed well in PANI. Fe3O4 increases the doping level and decreases the crystallinity of PANI. The PANI/Fe3O4 nanocomposite possesses conductivity and magnetic properties. Increasing the Fe3O4 content increases the magnetization of the PANI/Fe3O4 composite but decreases its conductivity. © 2006 Wiley Periodicals Inc. J Appl Polym Sci 102: 2107–2111, 2006
Polyoxymethylene (POM) is an important plastic with very good properties. However, its poor impact strength limits its applications. Theoretical and experimental studies have confirmed that thermoplastic polyurethane (TPU) can effectively enhance the notched impact strength of POM. This paper reports that the notched impact strength of POM/TPU blends can be further improved when these blends are endowed with a fine morphology by changing the viscosity ratio of TPU to POM (P = ηTPU/ηPOM) during processing. The experimental results show that the viscosity of TPU is more sensitive to temperature than that of POM, and that the viscosity ratio P decreases with increasing temperature; also for quite a wide range of shear rate, P is close to 1 when the processing temperature (Tp) is around 190 °C. Accordingly, the phase structure of POM/TPU blends changes with P. The dispersed phase of TPU shows ellipsoidal morphology when P > 1 at Tp < 190 °C, filamental morphology when P ≈ 1 at Tp ≈ 190 °C and spheroidal morphology when P < 1 at Tp > 190 °C. The results suggest that the filamental morphology endows POM/TPU (90/10) blends with the highest notched impact strength (∼14 kJ m−2). Copyright © 2006 Society of Chemical Industry
Ultrasonically initiated miniemulsion polymerization of styrene was conducted in the presence of Fe3O4 nanoparticles. Stable polystyrene (PS)/Fe3O4 nanocomposite emulsions were prepared and magnetic PS/Fe3O4 composite particles were obtained through magnetic separation. The whole procedure comprised two steps. First, Fe3O4 nanoparticles were dispersed in the monomer phase with the aid of stabilizer Span-80. Second, miniemulsion polymerization of styrene in the presence of Fe3O4 nanoparticles was carried out under an ultrasonic field in the absence of a chemical initiator. The affecting factors, including stabilizer concentration, surfactant concentration, hexadecane concentration and the amount of Fe3O4, were systematically studied. Stabilizer concentration, surfactant concentration and hexadecane concentration strongly affected the formation of the coagulation. The least amount of coagulation was formed at 2.5 wt% Span-80 concentration. The addition of Fe3O4 nanoparticles drastically increased the polymerization rate owing to the fact that Fe3O4 nanoparticles increased the acoustic intensity and Fe2+ reacted with H2O2 to produce hydroxyl radicals and increase the number of radicals. The increase in cosurfactant concentration and power output also increased the polymerization rate. Copyright © 2005 Society of Chemical Industry
The polyamide-6 (PA6)/natural clay mineral nanocomposites were successfully prepared by solid-state shear milling method without any treatment of clay mineral and additives. PA6/clay mixture was pan-milled to produce PA6/clay compounding powder, using pan-mill equipment. The obtained powder as master batch was diluted with neat PA6 to prepare composites by a twin-screw extruder. The clay silicate layers were found to be partially exfoliated and dispersed homogeneously at nanometer level in PA6 matrix. The rheological measurements and mechanical properties of nanocomposites were characterized. The shear viscosities of nanocomposites were higher than that of pure PA6, and tensile strength and tensile modulus increased, but Izod impact strength decreased, with increasing concentration of clay. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 249–255, 2006
Summary: A new technique, ultrasonically initiated in situ emulsion polymerization, was employed to prepare intercalated polystyrene/Na+-MMT nanocomposites. FTIR, XRD, and TEM results confirm that the hydrophobic PS can easily intercalate into the galleries of hydrophilic montmorillonite via ultrasonically initiated in situ emulsion polymerization, taking advantages of the multi-effects of ultrasonic irradiation, such as dispersion, pulverization, activation, and initiation. Properly reducing SDS concentration is beneficial to widen the d-spacing between clay layers. However, the Na+-MMT amount has little effect on the d-spacing of nanocomposites. The glass transition temperature of nanocomposites increased as the percentage of clay increased, although the average molecular weight of PS decreased, and the decomposition temperature of the 1obtained nanocomposites moves to higher temperature.
Thermal blowing of poly(vinyl alcohol) (PVA) film was successfully realized based on molecular complexation. Ways to enhance the performance of the PVA blown films (drawing and surface crosslinking) were studied. The experimental results showed that water exists in PVA films in different states through hydrogen bonds with PVA and other modifiers and influences the drawability of PVA films, as well as the structure and properties of the stretched films. When the initial water content of the film was higher than 35.0%, the draw ratio of the PVA film was quite large because of the effects of the bound water with PVA, as well as the plasticization of free water. With the increase of the initial water content in PVA, the free water content and draw ratio of the films increased but the strength of the films decreased because of the higher residual water in the films. Surface crosslinking can improve the stretchability of PVA films because more water remains in the films and disrupts the hydrogen bonding of PVA. In addition, crosslinking enhances the mechanical properties of stretched PVA films. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 774–779, 2005
In this paper, polypropylene (PP)/organophilic montmorillonite (OMMT) nanocomposites were successfully prepared without any compatibilizers by solid-state shear compounding (S3C) using pan-mill equipment. X-ray diffraction (XRD) patterns show that the OMMT characteristic (001) peak at 2θ equal to 4.59 degrees disappeared for the milled OMMT and corresponding composites. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) photographs show that the thickness of pan-milled OMMT decreased from ca 100–200 nm to ca 30–50 nm, and OMMT was partly exfoliated in the PP matrix because the pan-type mill can exert fairly strong squeezing force in the normal direction and shearing force in both radial and tangential directions on milled materials. PP/OMMT nanocomposites at low OMMT loading have higher melting point, crystallization temperature, thermal degradation temperature and heat distortion temperature than those of neat PP. Moreover, addition of OMMT accelerates crystallization of PP significantly. S3C is a novel approach to prepare polymer/layered silicate nanocomposites with high performances at low filler loading. Copyright © 2004 Society of Chemical Industry
The intercalation and exfoliation of talc have been realized by solid-state shear compounding (S3C) using pan-mill equipment that can exert fairly strong shear forces and has multifunctions such as pulverizing, mixing, and activation on materials. The structural features of pan-mill also show prospective in delaminating layered minerals. The morphology and structure of talc were investigated by using transmission electron microscopy (TEM) and X-ray diffraction (XRD). The characteristic peaks of talc interlayer spacing disappeared in the XRD pattern of PP/talc composite prepared by S3C, however, still remained in the XRD pattern of PP/talc prepared by the conventional mixing method. TEM confirms the intercalated and exfoliated structure of talc, and the well dispersion of talc in the PP matrix after talc and PP were co-milled. S3C is a new approach to prepare polymer/layered inorganic filler nanocomposite and has characteristics such as a simple process that needs neither organic ligands nor solvent. POLYM. ENG. SCI. 45:451–457, 2005. © 2005 Society of Plastics Engineers.
A solid-state mechanochemical pulverization process, that is, pan milling, was used to prepare a polypropylene (PP)/carbon nanotube (CNT) composite powder. The composite powder was then melt-mixed with a twin-roll masticator to obtain a PP/CNT composite. The morphology of the PP/CNT powder and the PP/CNT composite was investigated. The crystallization and mechanical properties of the latter were also studied. After 20 milling cycles (ca. 60 min), the average diameter of PP/3 wt % CNT composite powder particles was a few micrometers. The length of the CNTs was reduced from a few micrometers to 0.4–0.5 μm. The CNTs became straighter and more uniform in length. The effects of incorporating the CNTs into PP were as follows: (1) the crystallization rate and temperature of PP increased, (2) a strong b-plane orientation of PP was induced, and (3) the Young's modulus and yield strength of PP increased. Interfacial adhesion between PP and the CNTs was improved by the mechanical action of the solid-state pulverization process used, which favored the dispersion of the CNTs into PP. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 378–386, 2004
Several modified poly(vinyl alcohol) (PVA) systems with various plasticizers were prepared and their melt-processing was successfully realized. This paper focuses on the study of the evaporation behaviour of water in these modified PVA systems, exploring its plasticizing mechanism by using differential scanning calorimetry. The evaporation characteristics of bulk water, water in aqueous solutions of the plasticizers, and the thermal properties of PVA were also studied. The experimental results show that water in aqueous solutions of glycerol and/or caprolactam evaporates at a lower temperature than bulk water, but water in the PVA/water system evaporates at a higher temperature, with a wider DSC peak due to the interaction between water and PVA. Incorporation of glycerol, caprolactam or their mixtures further strengthens the interactions between water and the other components, retarding water evaporation. During the processing, the less closely associated water has the plasticizing effect through molecule movement, while the strongly bound water, which breaks the intermolecular hydrogen bonding of PVA and decreases its intermolecular interaction, is more beneficial to the melt-processing of PVA. Copyright © 2003 Society of Chemical Industry
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