Melt Pressing Research Articles

Carbon nanofiber/poly(vinylidene fluoride-hexafluoro propylene) composite films: The crystal structure and thermal properties with various drawing temperatures

Carbon nanofiber (CNF)/polyvinylidene fluoride-hexafluoro propylene (PVDF-HFP) composite film was prepared by solution casting and melt pressing. The resultant 2 % CNF/PVDF-HFP composite films were uniaxially drawn at 50 °C, 75 °C, and 100 °C, respectively. In the SEM images, the morphology of drawn CNF/PVDF-HFP composite film confirmed the orientation of the CNF and the polymer matrix. The WAXD results showed the coexistence crystal phase of PVDF-HFP. The drawn CNF/PVDF-HFP composite film demonstrates improved electrical properties. The DSC thermogram results indicated no change in the melting temperature but slightly increased crystallinity with increasing drawing temperature. Dynamic mechanical analysis and tensile test showed an improvement in the storage modulus and stress at a drawing temperature of 75 °C.

Synthesis and characterization of a renewable polyester containing oxabicyclic dicarboxylate derived from furfural

Techniques using biomass-based materials have become important to reduce the impacts of global warming and the depletion of petroleum resources. Changing biomass from edible to inedible is essential to solve global food issues. Furan derivatives are ideal chemicals for green chemistry because they are produced from inedible biomass resources. Here, we report the preparation of a biomass-based oxabicyclic dicarboxylic anhydride derived from furan derivatives and its polymerization with several α,ω-diols to polyoxabicyclates. 1H NMR spectra and MALDI-TOF MS measurements verified the chemical structure of the polyoxabicyclates. Polyoxabicyclates prepared using 1,3-propanediol or 1,4-butanediol could be moulded into elastic films by melt pressing. Tensile strength testing of the films indicated that they were highly elastic. Furthermore, the films had good transparency in the visible region.

나일론 4 공중합물 소재의 구조와 물성(III) -나일론 4 함량의 영향-

The effects of annealing on the fine structure and moisture regain of nylon 4 copolymer films were investigated in terms of the content of nylon 4. Nylon 6-ran-nylon 4 (50/50), (30/70), and (0/100) films were prepared using melt pressing and solution casting methods, respectively. The (N6-ran-N4) copolymer films were annealed in a silicon oil bath at 50, 75, 100, 125 and , and the properties of resultant film were examined by WAXD, DSC, DMTA and moisture regain. The crystal structure in (N6-ran-N4)(50/50) and (30/70) films with increasing annealing temperature was very similar to the gamma phase of nylon 6. The thermal property of (N6-ran-N4)(50/50) and (30/70) films annealed under high temperature exhibit an increase in melting temperature and enthlapy. The result of the tan behavior of (N6-ran-N4)(0/100) film was confirmed to the appearance of two transition peaks. The moisture regain of (N6-ran-N4) copolymer films, except in the case of (N6-ranN4)(30/70) films, decreased when the annealing temperature was increased.

Directed Self-Assembly of Metallosupramolecular Polymers at the Polymer-Polymer Interface.

Directed self-assembly of a metallosupramolecular polymer is achieved at the interface between two polymer films by simple melt pressing. Blends of a 2,6-bis(N-methylbenzimidazolyl)pyridine (MeBip) side-chain functionalized polystyrene in a polystyrene matrix and Zn(NTf2)2 in a poly(methyl methacrylate) matrix were pressed together above the Tg of the matrix polymers resulting in diffusion of the components and subsequent self-assembly of the metallosupramolecular polymer at the polymer-polymer interface. The formation of the metallosupramolecular polymer was monitored by spectroscopy and microscopy and it was found that the interfacial self-assembly occurs at the processing temperatures (ca. 210 °C) within 5 min. It was further shown that this materials system resulted in robust films that exhibited a new emergent property, namely, phosphorescence, which is not exhibited by any of the individual components nor the metallosupramolecular polymer itself.

Morphology, thermal, and dynamic mechanical properties of poly(lactic acid)/sisal whisker nanocomposites

AbstractSisal whiskers were used as biobased nanofillers to prepare poly(lactic acid) (PLA)‐based nanocomposites. The whiskers were prepared from sisal fibers via sulfuric acid hydrolysis. Freeze drying of the aqueous whisker suspension was carried out to obtain loosely packed dry sisal whiskers. The nanocomposites were prepared by melt mixing, followed by hot melt pressing. The effect of the freeze drying of the nanofibers, the treatments of the samples with maleic anhydride (MA)/dicumyl peroxide (DCP) and with DCP, and the premixing of the powdered components on the dispersion of the whiskers in the PLA matrix and on the morphology, as well as the thermal and dynamic mechanical properties, of the resultant nanocomposites were investigated. Transmission electron microscopy micrographs show that the acid hydrolysis has led to separation of the whiskers, which had an approximate length and diameter of 195 and 15 nm, respectively. The TEM images of the nanocomposites show similar dispersion of the whiskers in the PLA matrix, whether untreated or MA/DCP or DCP treated. It was found that the crystallization behavior of the PLA matrix changed somewhat depending on whether the samples were treated or not. The thermogravimetric analysis results show a slight decrease in the thermal stabilities of the untreated and the MA/DCP‐treated nanocomposite samples compared to that of the neat PLA, whereas the DCP treatment slightly improved the thermal stability of the nanocomposites. The storage modulus of the nanocomposites increased over the investigated temperature region, and the incorporation of sisal whiskers reduced the intensity of the glass transition at 67°C. POLYM. COMPOS., 2012. © 2012 Society of Plastics Engineers

Effects of raw materials and process parameters on the physical and mechanical properties of flat pressed WPC panels

For the production of WPC, the flat pressing technology can be considered as an alternative to common techniques, particularly when manufacturing large-dimensioned panels. The aim of the present study was to identify and analyze the main influencing parameters on sheets made of wood flour (WF) imbedded in a polypropylene matrix. Test panels were made to measure the effects of panel density, polymer melt flow rate (MFR), WF content, coupling agent, WF size and press temperature on water absorption (WA), thickness swelling (TS), internal bond strength, MOE and MOR. Density, WF content and MFR were identified as main influencing parameters. The increase of density typically leads to an improvement of properties. Lower WF contents cause reduced WA and TS, while the MOE seems to have a maximum at a WF level of 50–70%, depending on raw material used. As an explanation for improving properties when using a high-MFR polymer, a better distribution on the wood surface is hypothesized.

Ferroelectric and Electrical Properties of Potassium Nitrate Thin Composite Layers

The ferroelectric and electrical properties of potassium nitrate (KNO3): polyvinylidene fluoride (PVDF) composite layers prepared by melt press method have been studied. The stability of ferroelectric phase (phase –III) of potassium nitrate (KNO3) in the composite layers at room temperature have been analyzed. The temperature dependence of ferroelectric hysteresis loop (P-E) characteristics have been investigated in the composite layers. The electrical conductivity (σ) and dielectric behaviour of composite layers have been characterized. The conductivity and dielectric variation with temperature during heating and cooling modes has been found to provide the knowledge of phase transition in the composite. The capacitance –-voltage (C-V) and conductance - voltage (G-V) characteristics clearly show the ferroelectric butterfly loop, which is attributed to the features of ferroelectricity in the composite layers at room temperature. The coexistence of ferroelectric phase (phase III) with paraelectric phase (phase II) has also been observed at room temperature in the composite layers during dielectric and conductivity measurements.

Modification of surface properties of polypropylene films by blending with poly(ethylene-b-ethylene oxide) and its application

The possibility of improving the interfacial adhesion between polypropylene (PP) and polyamide layers (PA) has been investigated by means of addition of commercially available amphiphilic poly(ethylene-b-ethylene oxide) (P(E-b-EO)) block copolymers. These block copolymers were added to the PP matrix polymer in a twin screw extruder as integral additive. The change in surface properties of PP films upon incorporating P(E-b-EO) was investigated in model studies of blends prepared by casting PP/P(E-b-EO) solutions in 1,2-dichlorobenzene onto glass and Teflon Petri dishes, by melt pressing of PP/P(E-b-EO) blends between Teflon foils and glass substrates, or by melt extrusion of PP/P(E-b-EO) mixtures. The surfaces of the blend films were analyzed by attenuated total reflection Fourier transform infrared spectroscopy and water contact angle measurements. It was shown that an enrichment of the block copolymer at the surface of the blend depends highly on the conditions of film preparation and is driven by reducing the interfacial energy between the blend and the contacting medium. Effects of shear rate and residence time during normal processing conditions were also revealed. Blown film experiments with PP/P(E-b-EO) blends and PA were carried out for evaluating the effect of the integral P(E-b-EO) additive on the interfacial adhesion.

Hydroxyapatite nanorod-reinforced biodegradable poly(l-lactic acid) composites for bone plate applications

Novel PLLA composite fibers containing hydroxyapatite (HAp) nanorods with or without surface lactic acid grafting were produced by extrusion for use as reinforcements in PLLA-based bone plates. Fibers containing 0-50% (w/w) HAp nanorods, aligned parallel to fiber axis, were extruded. Lactic acid surface grafting of HAp nanorods (lacHAp) improved the tensile properties of composites fibers better than the non-grafted ones (nHAp). Best tensile modulus values of 2.59, 2.49, and 4.12 GPa were obtained for loadings (w/w) with 30% lacHAp, 10% nHAp, and 50% amorphous HAp nanoparticles, respectively. Bone plates reinforced with parallel rows of these composite fibers were molded by melt pressing. The best compressive properties for plates were obtained with nHAp reinforcement (1.31 GPa Young's Modulus, 110.3 MPa compressive strength). In vitro testing with osteoblasts showed good cellular attachment and spreading on composite fibers. In situ degradation tests revealed faster degradation rates with increasing HAp content. To our knowledge, this is the first study containing calcium phosphate-polymer nanocomposite fibers for reinforcement of a biodegradable bone plate or other such implants and this biomimetic design was concluded to have potential for production of polymer-based biodegradable bone plates even for load bearing applications.

Single-Component Polymer Composites

Noncovalently bonded crystalline inclusion compounds (ICs) have been formed by threading host cyclic starches, cyclodextrins (CDs), onto guest nylon-6 (N-6) chains. N-6 was coalesced from N-6-α-CD-IC crystals by appropriate removal of the host α-CD. When added at low concentrations, the coalesced N-6 serves as an effective self-nucleating agent for the bulk crystallization of N-6 from the melt. Film sandwiches consisting of two layers of as-received, and one layer each of as-received and self-nucleated N-6 were produced by melt pressing. DSC and tensile tests were conducted on these films. As-received and self-nucleated films have their own characteristic crystallization behaviors, and the film sandwich composed of one layer each of as-received and self-nucleated N-6 show a combination of the component melt-crystallization DSC peaks, indicating that both films maintain their characteristic structures and properties even after melt-processing them into a sandwich composite. This result clearly shows that we have a composite and not a single phase material and is supported by SEM images of the composite sandwich cross section. Furthermore, when compared to the film sandwich made with two layers of as-received N-6 film, the composite as-received/self-nucleated film sandwich shows superior mechanical properties.

Structure and properties of phase change materials based on HDPE, soft Fischer‐Tropsch paraffin wax, and wood flour

AbstractPhase‐change materials based on high density polyethylene (HDPE), soft Fischer‐Tropsch paraffin wax (M3), and alkali‐treated wood flour (WF) were investigated. The blend and composite samples were prepared by melt mixing using a Brabender Plastograph, followed by melt pressing. They were characterized in terms of their morphology, as well as thermal, mechanical, thermo‐mechanical, and water absorption properties. Although SEM micrographs showed some evidence of intimate contact between the WF particles and the HDPE matrix as a result of alkali treatment, poor filler dispersion, and interfacial adhesion were also observed. Partial immiscibility of the HDPE and the M3 wax was noticed, with the WF particles covered by wax. There was plasticization of the HDPE matrix by the wax, as well as partial cocrystallization, inhomogeneity and uneven wax dispersion in the polymer matrix. The HDPE/WF/M3 wax composites were more homogeneous than the blends. The presence of wax reduced the thermal stability of the blends and composites. Both the presence of M3 wax and WF influenced the viscoelastic behavior of HDPE. The HDPE/M3 wax blends showed an increase in the interfacial amorphous content as the wax content increases, which resulted in the appearance of a β‐relaxation peak. The presence of M3 wax in HDPE reduced the mechanical properties of the blends. For the composites these properties varied with WF content. An increase in wax content resulted to a decrease in water uptake by the composites, probably because the wax covered the WF particles and penetrated the pores in these particles. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010

On the unusual solvent retention and the effect on the gas transport in perfluorinated Hyflon AD ® membranes

Dense membranes of Hyflon AD 60X were prepared by the solvent evaporation method and by melt pressing. The diffusion coefficient, solubility and permeability of the membranes were measured for six permanent gases using time lag and steady state permeation measurements. The thermal properties were determined by Differential Scanning Calorimetry (DSC) and the solvent content was measured gravimetrically and was estimated by the Fox equation. It was found that unusually strong solvent retention in the solution-cast membrane leads to considerable plasticization of the polymer, to possible foam formation upon drying and, most important, to significant changes in the permeation properties. The residual solvent increases the diffusion coefficient and permeability of the larger gas species up to almost one order of magnitude, and it reduces the permselectivity. For most gas species the solubility is about two times higher in the solvent-free melt-pressed film than in the solution-cast film. The relation between the residual solvent and the membrane properties is discussed.

Dissolution and Enzymatic Degradation Studies Before and After Artificial Ageing of Silk‐ or Linen‐Reinforced Gelatin Laminates, 2

AbstractBiodegradable laminates based on gelatin and on gelatin/starch blend reinforced with fabrics (silk or linen) were prepared by melt pressing. Due to crosslinking during the thermal treatment and in some cases, to additional crosslinking with methylenedi(p‐phenyl) diisocyanate, the fresh and artificially aged samples demonstrated improved mechanical properties, as reported previously. In Part 1 of this study on the environmental behavior of these new laminated composites, the simple dissolution in a buffer solution or water of fresh and artificially aged samples was considered. During this treatment soluble, i.e., uncrosslinked molecules were removed leaving a product resulting from addition reactions and consequent crosslinking. These processes take place during the melt pressing at 180 °C and cause a decreased solubility of gelatin. The present Part 2 deals with the enzymatic treatment of the same samples. We have implicitly shown that the gelatin moiety of the laminates undergoes proteolysis and that this process depends on the laminate composition. At the end of the treatment the enzymatic buffer solution contains only peptides and virtually no high‐molecular gelatin. The degrees of degradation vs. time dependencies differ for water and enzymatic treatment of the samples, indicating different processes in either treatment. The time‐course curves of the enzymatic treatment of different laminates and the kinetic parameters derived therefrom were analyzed. Thereby the effect of many factors on the accessibility of the gelatin moiety to proteolysis was shown. These factors are: temperature treatment, artificial ageing, the nature of the reinforcing fabrics, the “additional” crosslinking with methylenedi(p‐phenyl) diisocyanate, etc. The gelatin‐linen laminate is the most sensitive to crosslinking. There is a tendency that the crosslinking smears the differences in the time‐course of the absorption behavior curves of the different samples.Degree of degradation, β′, (related to only the gelatin) vs. time, t, for laminates: (a) uncrosslinked gelatin‐linen; (b) crosslinked gelatin‐linen; (c) uncrosslinked gelatin‐silk; (d) crosslinked gelatin‐silk.magnified imageDegree of degradation, β′, (related to only the gelatin) vs. time, t, for laminates: (a) uncrosslinked gelatin‐linen; (b) crosslinked gelatin‐linen; (c) uncrosslinked gelatin‐silk; (d) crosslinked gelatin‐silk.

Dissolution and Enzymatic Degradation Studies Before and After Artificial Ageing of Silk‐ or Linen‐Reinforced Gelatin Laminates, 1

AbstractIn an attempt to overcome the poor mechanical properties of native, i.e., untreated gelatin, laminates based on gelatin and gelatin/starch blend reinforced with fabrics (linen or silk) were prepared by melt pressing. The mechanical properties of fresh and artificially aged samples were reported previously. In the present series of two consecutive papers we present data concerning the dissolution and biodegradation of these laminates. A two‐step procedure for treatment of the laminates was used. The first step is treatment with an aqueous buffer solution, the second with a buffered solution of the enzyme subtilisin. The time‐course of the absorbance at 280 nm of the “washing” solutions was followed. A number of kinetic characteristics was determined and discussed with respect to laminate composition and their treatments. In the present Part 1 about the environmental behavior of these new biodegradable materials, the non‐enzymatic solubilization in water and buffer solution (i.e., simple dissolution) of fresh and artificially aged samples is described. The dissolution process was followed spectrophotometrically as well as by the weight losses. It was found that gelatin‐based silk‐ or linen‐reinforced laminates were subject to dissolution, similarly to the gelatin and gelatin‐based materials studied in previous works. In addition, it was established that the thermal treatment of the laminates during their melt pressing leads to postcondensation reactions and crosslinking of the gelatin macromolecules. Similar reactions occur between the matrix and the reinforcing element silk, thus improving their mutual adhesion. Decreased gelatin dissolution ability was observed after the thermal treatment, in the presence of reinforced fabrics and upon “additional” crosslinking with methylenedi(p‐phenyl) diisocyanate. The untreated gelatin is the only one that dissolves completely in water. The artificially aged samples tend to dissolve better than the respective fresh samples due to degradation processes during aging. magnified image

Study on the structure of nylon 6 films iodinated before forming. I. Comparison with the film iodinated after forming

To examine the possibility of applying the iodination of nylon 6 to forming, a new type of nylon 6–iodine complex films iodinated before forming (IBF film) and the old type of films iodinated after forming (IAF film) were prepared and their structures were investigated and compared with each other. The IBF films from iodinated nylon 6 powders could be obtained by a melt press at 185°C, which is much lower than the melt-press temperature of pure nylon 6 (250°C). It was ascertained that the structure of IAF films is similar to that reported by Lee et al. but the structure of IBF films is very different. The distinctive features of the IBF films compared with the IAF films are as follows: The IBF films have no excess iodine molecules (I2) to form a complex with nylon 6 chains because those molecules in the iodinated powders have been evaporated through the melt press. The IBF films have a practically amorphous structure but only a few crystalline portions with a relaxed state which may have been created with iodide-ion-free segments of nylon 6 molecules through the procedure of film forming. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 1138–1144, 2003

Relaxation behavior of poly(ethylene terephthalate)/poly(ethylene naphthalene 2,6‐dicarboxylate) blends prepared by cryogenic blending

AbstractA method including cryogenic grinding, melt pressing from the molten state, and quenching was used to prepare blends of poly(ethylene terephthalate) (PET) and poly(ethylene naphthalene 2,6‐dicarboxylate) (PEN) in which the two phases were highly dispersed. The effect of melt‐pressing times on the thermal properties and relaxation behavior of PET/PEN films were characterized with differential scanning calorimetry and dielectric spectroscopy. For short melt‐pressing times, two glass‐transition, two crystallization, and two melting peaks were observed, indicating the presence of PET‐rich and PEN‐rich phases in these blends. Longer melt‐pressing times revealed a single glass transition and a single α‐relaxation process, showing that PET–PEN block copolymers were likely to be formed during the melt pressing. The experimental findings were examined in terms of the transesterification reactions between the blend components, as revealed by 1H NMR measurements. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 2570–2578, 2002

Synthesis and Characterization of PMMA Nanocomposites by Suspension and Emulsion Polymerization

PMMA-layered silicate nanocomposites were prepared by in-situ suspension polymerization and emulsion polymerization. For the suspension polymerization, the silicate layers were dispersed individually in water, and we speculate that they are adsorbed on the surface of monomer droplets. For the emulsion polymerization, the nanocomposite was obtained by adding an aqueous dispersion of layered silicate into the polymer emulsion. Wide-angle X-ray diffraction (WAXD) and atom force microscopy (AFM) were used to characterize the structures of the nanocomposites. Analysis of samples from emulsion and suspension polymerization was consistent with an exfoliated structure; after melt pressing, WAXD analysis indicated that both intercalated and exfoliated structures were observed. The exfoliated structure was preserved when organic modifiers that produced tethered polymer chains were used. Compared to a PMMA macrocomposite, the nanocomposites prepared by these methods display glass transition temperatures that are up to 15 °C higher and thermal degradation temperatures that are up to 60 °C higher.

Synthesis and Structure−Property Relationships of Soluble Rigid−Flexible Copolyethers Containing Blue and Yellow Light Emitting Units

A series of new rigid−flexible copolyethers containing blue- and yellow-emitting conjugated segments have been synthesized. The thermal, mechanical, and optical properties of the polymers are controlled by the type of the comonomers, their ratio at the preparation stage, and the length of the flexible spacer, as well as the structure of the blue monomer in the main chain. The polyethers were characterized by viscosimetry, thermal and mechanical analysis, NMR, and UV−vis and luminescence spectroscopy. The polymers obtained are soluble in common solvents, form free-standing films either from solution casting or after melt pressing, and show good mechanical properties. Regardless of the excitation wavelength, the polyethers show bright-yellow photoluminescence in solution, suggesting energy transfer from the blue to the yellow unit. In the solid state, the luminescence behavior is controlled by the monomer structure, the molar percentage of the comonomers, the length of the flexible spacer, and the excitatio...

Phase behavior of poly(ether urethane)‐nylon 6 block copolymer

AbstractPoly(ether urethane) (PEU)‐Nylon 6 block copolymer film prepared via melt pressing and subsequent quenching in liquid nitrogen exhibited a one‐phase structure due to the specific interaction between urethane groups in the PEU block and the amide groups in Nylon 6 block through hydrogen bonding. Contrary to this, the solvent cast film showed a microphase separated structure which had risen from the poor solubility characteristics of the PEU block in the solvent. However, by heat treatment, the mutual miscibility of the block copolymer increased as a result of the hydrogen bonding formation. The block copolymer and Nylon 6 binary blend showed that these two polymers are compatible over the entire composition range mainly due to the specific interactions between the urethane and the amide groups in the blend through hydrogen bonding. The block copolymer in the ternary blend which consists of polyrethane (PU), Nylon 6, and the block copolymer prepared by melt extrusion was soluble in either of the PU and Nylon 6 homopolymers, inducing a homogenizing effect. © 1994 John Wiley & Sons, Inc.

Synthesis and characterization of poly(ether urethane)‐nylon 6 block copolymer

Abstractpoly(ether urethane) (PEU) prepolymer terminated with isocyanate at both ends was prepared by controlling the mol ratio of poly(tetramethylene glycol) and methane diphenyl‐4,4'‐diisocyanate. Using this prepolymer as an activator, the anionic polymerization of ϵ‐ caprolactam was carried out to obtain PEU‐nylon 6 block copolymer. The phase structure of the block copolymers was characterized on the basis of molecular interaction. The results of dynamic mechanical and thermal analyses revealed that the block copolymer films prepared via melt pressing and subsequent quenching had a one‐phase structure. The equilibrium melting temperatures determined by a Hoffman‐Weeks plot showed that the two blocks are miscible in the melt state. N‐Trifluoroacetylation of the block copolymer led to the conclusion that this miscible behavior is due mainly to the specific interaction between urethane groups in PEU block and amide groups in nylon 6 block through hydrogen bonding. © 1993 John Wiley & Sons, Inc.