Physico-Mechanical Characteristics of Some EPDM/Plasticized PVC Blends

Summary: In this study were prepared blends based on ethylene propylene terpolymer rubber (EPDM) and plasticized poly (vinyl chloride) (PVC). These blends are immiscible and need to be compatibilized. The following compatibilization methods were used: (1) addition of a compatibilization agent; there were used: maleinized EPDM, maleinized polyethylene (PE), chlorinated polyethylene (CPE) and maleinized polypropylene (PP); chlorinated polyethylene has proved to be the most efficient; the amount of the added CPE giving the best physico-mechanical characteristics was of 7,5 parts to 100 polymer parts; (2) reactive compatibilization, using crosslinked copolymer formation strategy; three different crosslinking systems were used: (a) common method with sulphur and accelerators, (b) crosslinking with benzoyl peroxide and trimethylpropane trimethacrylate (TMPT DL 75), (c) vulcanization with phenol resin and tin chloride. The best physico-mechanical characteristics were obtained with the EPDM/plasticized PVC blends crosslinked with 8 phr phenol resin. Such types of polymer blends can be processed by methods specific for plastics, removing thus vulcanization operation required in case of elastomers. These blends can be used in the manufacture of hoses, gaskets, footwear constituents etc.     

IR laser ablative decomposition of poly(vinyl acetate) loaded with Fe and Cu particles

Pulsed IR laser-induced decomposition of poly(vinyl acetate) (PVAC) loaded with nanometer-sized Cu and micrometer-sized Fe particles results in the formation of gaseous products and deposition of polar crosslinked polymer films which contain metal (Cu and Fe) particles. The main volatile products are hydrocarbons, carbon oxides (CO and CO₂), molecular hydrogen and acetic acid. The deposited polymer films were characterized by FTIR, UV and XP spectra and by electron microscopy and thermogravimetry. They contain reactive conjugated CC bonds and ca. 50% of the initially present acetate groups. Residual reactivity of the CC bonds results in polymer crosslinking and decrease in solubility. The deposited, crosslinked PVAC-based films containing metal particles are less thermally stable than similar films not containing these particles. The reported process reveals feasible ablation of metal particles when embedded in a polymer and makes it possible to fabricate films of metal/polymer composites in which metal particles are completely protected by the polymer.     

Hydrophilic Films Based on Blends of Poly(acrylic acid) and Poly(2‐hydroxyethyl vinyl ether): Thermal,Mechanical, and Morphological Characterization

Hydrophilic films based on blends of poly(acrylic acid) and poly(2‐hydroxyethyl vinyl ether) were prepared by casting. The characterization of the films was performed by differential scanning calorimetry (DSC), dynamic mechanical thermal analysis (DMTA), and scanning electron microscopy (SEM). It was shown that an increase of poly(2‐hydroxyethyl vinyl ether) content in the blends considerably decreases the glass transition temperature of the samples. The films containing 10 and 20 mol‐% of poly(2‐hydroxyethyl vinyl ether) show behavior of polymers in the glassy state, but a further increase of nonionic polymer content in the blend (30–50 mol‐%) provides the mechanical properties typical of a rubbery state. The content of water traces in the films has a significant effect on the mechanical properties of the materials.

Normalized DSC thermograms of PAA:PHEVE films. [PAA]:[PHEVE] = 90:10 (1), 80:20 (2), 70:30 (3), 60:40 (4), 50:50 mol‐% (5).     

Poly(silylenemethylene)‐based polymer blends. III. Synthesis and properties of polymer blends containing siloxane‐crosslinked poly(silylenemethylene)s

Soft–hard binary polymer blends consisting of amorphous poly(silylene methylene)s (PSMs) and crystalline poly(diphenylsilylenemethylene) were prepared by both melt processing at 360 °C and in situ polymerization at 300 °C. Linear and siloxane‐crosslinked PSMs were used as amorphous components for the purpose of determining how the crosslinks affected the interactions between the component polymers. Differential scanning calorimetry and dynamic mechanical analysis indirectly suggested that discernable differences between the blends containing linear and crosslinked PSMs were attributable to the degree of interactions between the amorphous and crystalline components. The morphological differences between these blends were studied with transmission electron microscopy. The dispersion phase was smaller in the blends containing crosslinked PSM than that in the blends containing linear PSM. This directly indicated that a larger interaction between the amorphous and crystalline phases was obtained by the introduction of crosslinks because of the smaller viscosity difference between the phases and a larger degree of polymer chain entanglement. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 257–263, 2003     

Crosslinkable poly(p‐phenylenevinylene) derivative

To simplify the fabrication of multilayer light‐emitting diodes, we prepared a p‐phenylenevinylene‐based polymer capped with crosslinkable styrene through a Wittig reaction. Insoluble poly(p‐phenylenevinylene) derivative (PPVD) films were prepared by a thermal treatment. The photoluminescence and ultraviolet–visible (UV–vis) absorbance of crosslinked films and noncrosslinked films were studied. We also studied the solvent resistance of crosslinked PPV films with UV–vis absorption spectra and atomic force microscopy. Double‐layer devices using crosslinked PPVD as an emitting layer, 2‐(4‐tert‐butylphenyl)‐5‐phenyl‐1,3,4‐oxadiazole (PBD) in poly(methyl methacrylate) as an electron‐transporting layer, and calcium as a cathode were fabricated. A maximum luminance efficiency of 0.70 cd/A and a maximum brightness of 740 cd/m² at 16 V were demonstrated. A 12‐fold improvement in the luminance efficiency with respect to that of single‐layer devices was realized. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 2124–2129, 2004     

Fabrication of Silver Nanoparticles in Hydrogel Networks

Summary: This paper describes a simple and facile approach to fabricate well dispersed silver nanoparticles (AgNPs) in poly[N‐isopropylacrylamide‐co‐(sodium acrylate)] hydrogels. The silver nanoparticles formed are spherical in shape with a narrow size distribution in the hydrogel networks in which the nanoparticles are stabilized by the polymer network. Uniformly dispersed silver nanoparticles were obtained with poly[N‐isopropylacrylamide‐co‐[sodium acrylate)] hydrogels, whereas a poly(N‐isopropylacrylamide)/poly(sodium acrylate) IPN gel showed aggregated nanoparticles. It is demonstrated that the hydrogel network structure determines the size and shape of the nanoparticles. These particles are more stable in the gel networks compared to other reduction methods. The hydrogel/silver nanohybrids were well characterized by XRD, UV‐vis spectrometry, scanning electron microscopy and transmission electron microscopy.

Schematic representation of the preparation of Ag nanoparticles in hydrogel networks.     

IR laser ablation of poly(vinyl chloride): Formation of monomer and deposition of nanofibres of chlorinated polyhydrocarbon

IR laser-induced ablation of poly(vinyl chloride) was examined under different irradiation conditions and its volatile and solid products were characterized by mass, infrared, UV and X-ray photoelectron spectroscopy, electron microscopy and thermogravimetry. It is demonstrated that the major component among the volatile products is monomeric vinyl chloride and that the process causes deposition of Cl-containing polymeric films. The proportion between the volatile and solid products as well as the nature of the deposited films at different laser fluences have been examined. We show that the deposited films incorporate less Cl atoms than poly(vinyl chloride) and that they initially contain conjugated CC bonds and incorporate nano-sized fibre and necklace features. The process represents the first example of thermal degradation of poly(vinyl chloride) into monomer and makes it possible to fabricate crosslinked Cl-containing intractable polymer films.     

Investigation of swelling and network parameters of poly(ethylene glycol)-crosslinked poly(methyl vinyl ether-co-maleic acid) hydrogels

The influence of poly(ethylene glycol) (PEG) plasticiser content and molecular weight on the physicochemical properties of films cast from aqueous blends of poly(methyl vinyl ether-co-maleic acid) was investigated using thermal analysis, swelling studies, scanning electron microscopy (SEM) and attenuated total reflectance (ATR)-Fourier transform infrared (FTIR) spectroscopy. FTIR spectroscopy revealed a shift of the CO peak from 1708 to 1731 cm⁻¹, indicating that an esterification reaction had occurred upon heating, thus producing crosslinked films. Higher molecular weight PEGs (10,000 and 1000 Da, respectively), having greater chain length, producing hydrogel networks with lower crosslink densities and higher average molecular weight between two consecutive crosslinks. Accordingly, such materials exhibited higher swelling rates. Hydrogels crosslinked with a low molecular weight PEG (PEG 200) showed rigid networks with high crosslink densities and, therefore, lower swelling rates. Polymer:plasticizer ratio alteration did not yield any discernable patterns, regardless of the method of analysis. The polymer-water interaction parameter (χ) increased with increases in the crosslink density. SEM studies showed that porosity of the crosslinked films increased with increasing PEG MW, confirming what had been observed with swelling studies and thermal analysis, that the crosslink density must be decreased as the M_w of the crosslinker is increased. Hydrogels containing PMVE/MA/PEG 10,000 could be used for rapid delivery of drug, due to their low crosslink density. Moderately crosslinked PMVE/MA/PEG 1000 hydrogels or highly crosslinked PMVE/MA/PEG 200 systems could then be used in controlling the drug delivery rates. We are currently evaluating these systems, both alone and in combination, for use in sustained release drug delivery devices.     

Characterisation of Hyaluronic Acid Blends Modified by Poly(N-Vinylpyrrolidone)

The viscosity behaviour and physical properties of blends containing hyaluronic acid (HA) and poly(N-vinylpyrrolidone) (PVP) were studied by the viscometric technique, steady shear tests, tensile tests and infrared spectroscopy. Viscometric and rheological measurements were carried out using blends of HA/PVP with different HA weight fractions (0, 0.2, 0.5, 0.8 and 1). The polymer films and HA/PVP blend films were prepared using the solution casting method. The study of HA blends by viscometry showed that HA/PVP was miscible with the exception of the blend with high HA content. HA and its blends showed a shear-thinning flow behaviour. The non-Newtonian indices (n) of HA/PVP blends were calculated by the Ostwald–de Waele equation, indicating a shear-thinning effect in which pseudoplasticity increased with increasing HA contents. Mechanical properties, such as tensile strength and elongation at the break, were higher for HA/PVP films with w_HA = 0.5 compared to those with higher HA contents. The elongation at the break of HA/PVP blend films displayed a pronounced increase compared to HA films. Moreover, infrared analysis confirmed the existence of interactions between HA and PVP. The blending of HA with PVP generated films with elasticity and better properties than homopolymer films.     

紫外光交联可降解聚对二氧环己酮/聚乙二醇薄膜制备与表征

以2,2-二甲氧基-2-苯基苯乙酮(DMPA)为引发剂,将四臂端丙烯酸酯聚对二氧环己酮(PPDO-4AC)和聚乙二醇双丙烯酸酯(PEG-DA)经紫外光照射制得PPDO/PEG交联薄膜.研究了光照时间和DMPA用量对PPDO/PEG交联薄膜凝胶含量的影响.DSC研究表明共聚物中两组分的相容性较好,Tg随着共聚物中PEG链...     

Improvement of compatibility,mechanical, thermal and dielectric properties of poly(lactic acid) and poly(butylene adipate-co-terephthalate) blends and their composites with porous clay heterostructures from mixed surfactant systems

In this study, nanocomposite poly(lactic acid) and poly(butylene adipate-co-terephthalate) (PLA/PBAT) blends were prepared through polymer blending in the presence of multi-functional epoxy as a compatibilizer that could react with epoxy group and terminated end group of two phases to increase interfacial adhesion between PLA and PBAT and improve the toughness of PLA. The effects of porous clay heterostructure from mixed CTAB:CTAC surfactant in the mole ratio of 1:2 (B1C2-PCH) were also investigated. The elongation at break of the blends reached 38%, which was eight times that of neat PLA. The cryo-fractured surface demonstrated the interfacial adhesion caused by the interaction of the epoxy group of the reactive compatibilizer with the terminal carboxyl and hydroxyl groups of PLA and PBAT. Moreover, PBAT reduced the crystallization rate and percent crystallinity of the PLA matrix and further decreased when compatibilizer was used. Alternatively, B1C2-PCH accelerated the heterogeneous nucleation and crystallization of the nanocomposite films. After adding small amount of B1C2-PCH, the nanocomposite films demonstrated excellent dielectric properties. Therefore, the improvement of PLA/PBAT nanocomposite blends are capable to be further developed as polymeric capacitor films.     

Immiscibility,upper critical solution temperature,and miscibility in blends of poly(vinyl ether)s with polyacrylics: Effects of pendant groups

Various phase behavior of blends of poly(vinyl ether)s with homologous acrylic polymers (polymethacrylates or polyacrylates) were examined using differential scanning calorimetry, optical microscopy (OM), and Fourier‐transformed infrared spectroscopy. Effects of varying the pendant groups of either of constituent polymers on the phase behavior of the blends were analyzed. A series of interestingly different phase behavior in the blends has been revealed in that as the pendant group in the acrylic polymer series gets longer, polymethacrylate/poly(vinyl methyl ether) (PVME) blends exhibit immiscibility, upper critical solution temperature (UCST), and miscibility, respectively. This study found that the true phase behavior of poly(propyl methacrylate)/PVME [and poly(isopropyl methacrylate)/PVME)] blend systems, though immiscible at ambient, actually displayed a rare UCST upon heating to higher temperatures. Similarly, as the methyl pendant group in PVE is lengthened to ethyl (i.e., PVME replaced by PVEE), phase behavior of its blends with series of polymethacrylates or polyacrylates changes correspondingly. Analyses and quantitative comparisons on four series of blends of PVE/acrylic polymer were performed to thoroughly understand the effects of pendant groups in either polyethers (PVE's) or acrylic polymers on the phase behavior of the blends of these two constituents. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 1521–1534, 2007     

Phase behavior,crystallization, and morphology in thermosetting blends of a biodegradable poly(ethylene glycol)‐type epoxy resin and poly(ϵ‐caprolactone)

Thermosetting blends of a biodegradable poly(ethylene glycol)‐type epoxy resin (PEG‐ER) and poly(?‐caprolactone) (PCL) were prepared via an in situ curing reaction of poly(ethylene glycol) diglycidyl ether (PEGDGE) and maleic anhydride (MAH) in the presence of PCL. The miscibility, phase behavior, crystallization, and morphology of these blends were investigated. The uncured PCL/PEGDGE blends were miscible, mainly because of the entropic contribution, as the molecular weight of PEGDGE was very low. The crystallization and melting behavior of both PCL and the poly(ethylene glycol) (PEG) segment of PEGDGE were less affected in the uncured PCL/PEGDGE blends because of the very close glass‐transition temperatures of PCL and PEGDGE. However, the cured PCL/PEG‐ER blends were immiscible and exhibited two separate glass transitions, as revealed by differential scanning calorimetry and dynamic mechanical analysis. There existed two phases in the cured PCL/PEG‐ER blends, that is, a PCL‐rich phase and a PEG‐ER crosslinked phase composed of an MAH‐cured PEGDGE network. The crystallization of PCL was slightly enhanced in the cured blends because of the phase‐separated nature; meanwhile, the PEG segment was highly restricted in the crosslinked network and was noncrystallizable in the cured blends. The phase structure and morphology of the cured PCL/PEG‐ER blends were examined with scanning electron microscopy; a variety of phase morphologies were observed that depended on the blend composition. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 2833–2843, 2004     

Poly(3,4-ethylenedioxythiophene) Heterogeneity: A Differential Cyclic Voltabsorptometry Study

A voltabsorptometry study of the redox behavior of poly(3,4-ethylenedioxythiophene) films in tetrabutylammonium tetrafluoroborate solutions in acetonitrile shows the polymer to exhibit heterogeneous properties when both reduced and oxidized. The measurements are taken at characteristic wavelengths selected on the basis of stationary absorption spectra. The reduced polymer's heterogeneity is explained under the assumption that the polymer contains simultaneously linear ( = 530 nm) and spiral ( = 660 nm) structures. The formation of two oxidized polymer states is proved experimentally. Both states presumably result from strong ( = 880 nm) and weak ( = 1050 nm) interactions between the anion and the positively charged polymer chain. The oxidized 880-nm state is shown to arise from the 660-nm state, whereas the 1050-nm state forms of the 530-nm state.     

Poly(ethylene oxide)/poly(methyl methacrylate) (semi-)interpenetrating polymer networks: Synthesis and phase diagrams

Interpenetrating polymer networks (IPNs) of poly(ethylene oxide) (PEO) and poly(methyl methacrylate) (PMMA) were prepared by simultaneous network formation. The PEO network was produced by acid-catlayzed self-condensation of α,ω-bis(triethoxysilane)-terminated PEO in the presence of small amounts of water. The PMMA network was formed by free radical polymerization of MAA in the presence of divinylbenzene as crosslinker. The reaction conditions were adjusted to obtain similar crosslinking kinetics for both reactions. An attempt was made to construct a phase diagram of the IPNs by measuring the composition of the IPNs at the moment of the appearance of the phase separation, as indicated by the onset of turbidity. This composition could be determined because the siloxane crosslinks of the PEO network could be hydrolyzed in aqueous NaOH with the formation of linear, soluble PEO chains. The phase diagram was compared with phase diagrams of blends of linear polymers and of semi-IPNs (crosslinked PMMA and linear PEO), obtained under similar conditions, i.e. polymerization of MMA in the presence of varying amounts of PEO. It was observed that the form of the phase diagrams of the linear polymers is similar to that of the IPNs, but is quite different from that of the semi-IPNs. Thus, homogeneous transparent materials containing up to 60% of PEO could be prepared in the blends and the IPNs, but in the semi-IPNs, phase separation occurred with PEO contents as low as 10%.     

Crosslinked poly(ethylene oxide) containing siloxanes fabricated through thiol‐ene photochemistry

Homogenous amphiphilic crosslinked polymer films comprising of poly(ethylene oxide) and polysiloxane were synthesized utilizing thiol‐ene “ click ” photochemistry. A systematic variation in polymer composition was Carried out to obtain high quality films with varied amount of siloxane and poly(ethylene oxide). These films showed improved gas separation performance with high gas permeabilities with good CO₂/N₂ selectivity. Furthermore, the resulting films were also tested for its biocompatibility, as a carrier media which allow human adult mesenchymal stem cells to retain their capacity for osteoblastic differentiation after transplantation. The obtained crosslinked films were characterized using differential scanning calorimetry, dynamic mechanical analysis, thermogravimetric analysis, FTIR, Raman‐IR , and small angle X‐ray scattering. The synthesis ease and commercial availability of the starting materials suggests that these new crosslinked polymer networks could find applications in wide range of applications. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 1548–1557     

Linear and four‐armed poly(l‐lactide)‐block‐poly(d‐lactide) copolymers and their stereocomplexation with poly(lactide)s

Linear and four‐armed poly(l ‐lactide)‐block‐poly(d ‐lactide) (PLLA‐b‐PDLA) block copolymers are synthesized by ring‐opening polymerization of d ‐lactide on the end hydroxyl of linear and four‐armed PLLA prepolymers. DSC results indicate that the melting temperature and melting enthalpies of poly (lactide) stereocomplex in the copolymers are obviously lower than corresponding linear and four‐armed PLLA/PDLA blends. Compared with the four‐armed PLLA‐b‐PDLA copolymer, the similar linear PLLA‐b‐PDLA shows higher melting temperature (212.3 °C) and larger melting enthalpy (70.6 J g^?1). After these copolymers blend with additional neat PLAs, DSC, and WAXD results show that the stereocomplex formation between free PLA molecular chain and enantiomeric PLA block is the major stereocomplex formation. In the linear copolymer/linear PLA blends, the stereocomplex crystallites (sc) as well as homochiral crystallites (hc) form in the copolymer/PLA cast films. However, in the four‐armed copolymer/linear PLA blends, both sc and hc develop in the four‐armed PLLA‐b‐PDLA/PDLA specimen, which means that the stereocomplexation mainly forms between free PDLA molecule and the inside PLLA block, and the outside PDLA block could form some microcrystallites. Although the melting enthalpies of stereocomplexes in the blends are smaller than that of neat copolymers, only two‐thirds of the molecular chains participate in the stereocomplex formation, and the crystallization efficiency strengthens. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2014 , 52, 1560–1567     

Characteristics and degradation of hybrid composite films prepared from PVA,starch and lignocellulosics

A research cooperation between USDA and the University of Pisa led to the development of several composite blends of poly(vinyl alcohol) (PVA) and lignocellulosic fibers. The cast films were prepared by blending orange fibers (OR-fibers) and PVA with and without cornstarch to yield flexible and cohesive films. To improve properties, films were also prepared by crosslinking PVA, starch and OR-fibers with hexamethoxymethylmelamine (HMMM). Films were evaluated for their thermal stability, water permeability and biodegradation. Thermal gravimetric analyses indicated the potential usefulness of such blends in several thermoplastic applications. Films were permeable to water, and retained the moisture content in the soil while retaining their integrity. Films generally biodegraded within 30 days in compost, achieving between 50-80% mineralization. Both neat PVA and blends that had been crosslinked showed comparatively slow degradation. A possible stimulating effect of lingocellulosic fillers on the biodegradation of PVA in blends has been observed.     

Effect of inert diluent segment on the miscibility behavior of poly(vinylphenol) with poly(acetoxystyrene) blends

Polymer blends of poly(vinylphenol) (PVPh) and poly(styrene‐co‐vinylphenol) with poly(p‐acetoxystyrene) (PAS) were prepared by solution casting from tetrahydrofuran solution. The thermal properties and hydrogen bonding of the blends were investigated by differential scanning calorimetry (DSC) and Fourier transform infrared spectroscopy. Although hydrogen bonding existed between the PVPh and PAS segments, the experimental results indicated that PVPh is immiscible with PAS as shown by the existence of two glass‐transition temperatures over the entire composition range by DSC. This phenomenon is attributed to the strong self‐association of PVPh, intramolecular screening, and functional group accessibility effects of the PVPh/PAS blend system. However, the incorporation of an inert diluent moiety such as styrene into the PVPh chain renders the modified polymer to be miscible with PAS. Copolymers containing between 16 and 51 mol % vinylphenol were fully miscible with PAS according to DSC studies. These observed results were caused by the reduction of the strong self‐association of PVPh and the increase of the interassociation between PVPh and PAS segments with the incorporation of styrene on the PVPh chain. According to the Painter‐Coleman association model, the interassociation equilibrium constant of PVPh/PAS blends was determined by a model compound and polymer blend. Good correlation between these two methods was obtained after considering the intramolecular screening and functional group accessibility effect in the polymer blend. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 1661–1672, 2002     

Reactive surfactants in heterophase polymerization

The mechanism for the formation of polymer particles in the dispersion polymerization of methyl methacrylate and styrene in alcohol-water mixtures has been investigated. Methacrylic based poly(ethylene oxide) macromonomers and poly(vinyl-pyrrolidone) have been used as steric stabilizers. Dynamic light scattering as well as transmission electron microscopy have been applied to determine the evolution of the average particle size at the beginning of the polymerization. Stable nuclei from 80 to 400 nm in diameter size were detected. The nucleation process was quite rapid and completed within less thanca. 0.1% monomer conversion. The experimental results are compared with those predicted by the multibin kinetics model for coalescence developed by Paine [(1990) Macromolecules 23: 3109].A series of publication from the EU program Human Capital and Mobility (CHRX CT 93-0159)