Adhesive Bond Properties of Ethyl-2-cyanoacrylate Modified with Poly(methylmethacrylate)

The mechanical properties of the adhesively bonded joints with ethyl-2-cyanoacrylate and ethyl-2-cyanoacrylate modified with poly(methylmethacrylate) were determined. The modifier lowers tensile stiffness, increases deformability and relaxation of the adhesive bond and improves impact resistance. A morphological structure similar to an interpenetrating network system is suggested which arises from the rapid polymerization of the solvent. The results obtained may be helpful for the design of joints with cyanoacrylate bonding.     

Surface Properties for Blended Films of Poly(methylmethacrylate) and Terpolymers Composed of Methylmethacrylate, Methoxypoly(ethyleneglycol-methacrylate) and Poly(dimethylsiloxanemethacrylate)

Terpolymers composed of methylmethacrylate (MMA), poly(dimethylsiloxanemethacrylate) (PDMSMA) and methoxypoly(ethyleneglycolmethacrylate) (MPEGMA), which have blood compatibility, were blended with poly(methylmethacrylate) (PMMA) in order to improve their mechanical properties. It was expected that low surface free energy components such as the poly(dimethylsiloxane) (PDMS) and methoxy groups of terpolymer would predominate at the blend surface. The adsorptions of PDMS to the blended surfaces were confirmed via X-ray photoelectron spectroscopy (XPS). A large contact angle hysteresis was observed for the blended films via a dynamic contact angle. Advancing contact angles for blended films showed the same values as that of the silicone. The receding contact angles for those blends incorporating PDMSMA-rich terpolymer showed high values and decreased with hot water treatment, while MPEGMA-rich terpolymer blended films exhibited low values and maintained those values after hot water treatment. Adhesion tension relaxations for these blended films were also observed. These phenomena were interpreted to be caused by the reorganization of a hydrophobic segment to the polymer surface or hydrophilic segment to the water/polymer interface so as to decrease the surface or interfacial tension, respectively. Although the mechanical properties slightly decreased with blending of these terpolymers, the blended films could be applied for various practical uses.     

Thermal,Mechanical and Chemical Properties of Hydrophilic Poly(vinyl alcohol) Film Improved by Hydrophobic Poly(propylene glycol)

A series of poly(vinyl alcohol)/poly(propylene glycol) (PVA/PPG) blend films with different PPG contents were prepared by casting the polymer blend solutions. Structure and morphologies of the PVA/PPG blend films were studied by Fourier transform infrared spectroscopy (FT-IR) and scanning electron microscopy (SEM). Thermal, mechanical, and chemical properties of PVA/PPG blend films were investigated by differential scanning calorimeter (DSC), thermogravimetric analysis (TGA), tensile strength tests, and other physical methods. It was revealed that the introduction of PPG could exert marked effects on the morphology and the properties of PVA film.     

Morphology and Dielectric Properties of Polyhydroxybutyrate (PHB)/Poly(methylmethacrylate)(PMMA) Blends with Some Antimicrobial Applications

Poly(3-hydroxy)butyrate (PHB) is a microbial polyester, which provides the advantages of biodegradability and biocompatibility but it is brittle and has low abilities for some chemical modifications. To overcome such problems reactive blending was done with a glassy acrylic polymer, poly(methylmethacrylate) (PMMA) with different compositions. The dielectric response of PHB/PMMA blend with different compositions were investigated as a function of frequency and at different temperatures. The results revealed the existence of single a-relaxation process indicating the miscibility of amorphous fractions of PHB and PMMA. Also the morphological study of such blends doesn't show macro phase separation of PMMA on the surface scan which may be attributed to the compatibility in melt between PHB and PMMA particles in the PHB matrix. The biological activity of such investigated systems against some pathogenic microorganisms was found to increase by increasing the amount of PMMA in the blend     

Studies of Deformed Poly(Methyl Methacrylate) Using Positron Annihilation Lifetime Spectroscopy

Abstract

Structural rearrangements in glassy PMMA on polymer plastic deformation and recovery of residual plastic deformation in glassy state were studied by positron annihilation lifetime spectroscopy. Uniaxial compression was shown to be accompanied by a decrease in concentration of free volume microregions in disordered polymer regions, which were characterized by low packing density. Recovery of residual deformation at elevated temperatures but below glass transition point T_g proceeds without any noticeable changes in fractional content of free volume both in disordered and ordered polymer regions. The advantages of positron annihilation lifetime spectroscopy for studying microstructure and structural rearrangements in polymers were discussed.     

High breakdown strength and low loss of polystyrene-block-poly(methyl methacrylate)/Poly(vinylidene fluoride) composites for energy storage application

Poly(vinylidene fluoride) (PVDF) composite films were prepared by introducing polystyrene-block-poly(methyl methacrylate) (PS-b-PMMA) into PVDF matrix. Uniform dispersion and good compatibility of PS-b-PMMA in matrix were observed, which was helpful for high breakdown strength (E_b). The composite film with 9 wt% PS-b-PMMA showed the maximum E_b of 522 kV/mm and the high discharged energy density (U_e) of 10.1 J/cm³, which were 1.7 times and 2.6 times higher than pure PVDF, respectively. Besides, a charged-discharged efficiency (η) of 88% was much higher than pure PVDF at 300 kV/mm, which was beneficial to energy storage.     

Miscibility enhancement on the immiscible binary blend of poly(vinyl acetate) and poly(vinyl pyrrolidone) with bisphenol A

The miscibility behavior and hydrogen bonding of ternary blends of bisphenol A (BPA)/poly(vinyl acetate) (PVAc)/poly(vinyl pyrrolidone) (PVP) were investigated by using differential scanning calorimetry and Fourier transform infrared spectroscopy (FTIR). The BPA is miscible with both PVAc and PVP based on the observed single T_g over the entire composition range. FTIR was used to study the hydrogen-bonding interaction between the hydroxyl group of BPA and the carbonyl group of PVAc and PVP at various compositions. Furthermore, the addition of BPA is able to enhance the miscibility of the immiscible PVAc/PVP binary blend and eventually transforms into miscible blend with single T_g, when a sufficiently quantity of the BPA is present due to the significant Δχ and the ΔK effect.     

Heat Resistant and Mechanical Properties of Biodegradable Poly(Lactic Acid)/Poly(Butylene Succinate) Blends Crosslinked by Polyaryl Polymethylene Isocyanate

This work focus on improving the heat resistant and mechanical properties of poly(lactic acid)/poly(butylene succinate) (PLA/PBS) blends using appropriate contents of polyaryl polymethylene isocyanate (PAPI). Some crosslinked structures were formed according to the gel fraction and rheological results, and the crosslinked structures played the role of nucleation site for the blends. And the Vicat softening temperature of the blends gradually increased with increasing PAPI content. Moreover, the addition of PAPI in the PLA/PBS blends produced a few PLA-PBS copolymers which acted as a compatibilizer and enhanced the interfacial adhesion. Thus, the mechanical properties of PLA were significantly improved.     

Electron spin resonance and optical studies of poly(methylmethacrylate) doped with CuCl2

Poly(methyl methacrylate) doped with CuCl₂ was prepared and its electron spin resonance (ESR) spectra and optical properties were studied. The ESR spectra can be accounted for by the presence of two radicals: R_a and R_b. FTIR spectroscopy reveals that there is no main difference of the spectra due to the addition of CuCl₂. The structural modifications are identified by investigating the doping level dependence of the peak heights of certain IR absorption peaks. The optical absorption, transmittance, and reflectance measurements were performed for prepared samples. The doping level (W) dependence on the g‐factor (g), asymmetry factor (A), peak‐to‐peak separation (ΔH_pp), spin concentration (N), optical energy gap (E_opt), Urbach energy (E_u), refractive index (n), average oscillator wavelength (λ_o), and average oscillator strength (S_o) were estimated. It was found that these parameters are changed with doping level. These changes suggest high sensitivity of these films to doping that would suggest the applicability in magnetic and/or optical devices. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Gelatin/Poly(ethylene oxide) Blend Films with Compositional Gradient: Fabrication and Characterization

In this study, novel protein/biodegradable polymer blend biomaterials‐gelatin/poly(ethylene oxide) blend films with compositional gradients were successfully fabricated by a dissolution/diffusion method. Two kinds of compositional gradient films, which were different in gradient structure, were prepared. The compositional gradient structure in the films was characterized by polarized optic microscopy, ATR‐FTIR, and trans‐FT‐IR mapping measurement. In addition, the mechanical properties of the gradient films were characterized with reference to their gradient structure. It is found that the compositional gradient films have better mechanical properties than the pure gelatin film. These protein/biodegradable polymer compositional gradient films have a potential for many biomedical applications.

     

Thermal Property and Hydrogen Bonding in Blends of Poly(vinylphenol) and Poly(hydroxylether of Bisphenol A)

The thermal property and hydrogen bonding in polymer blends of poly(vinylphenol) (PVPh) and poly(hydroxylether of bisphenol A) (phenoxy) were investigated by differential scanning calorimetry (DSC), Fourier transform infrared spectroscopy (FTIR) and solid-state nuclear magnetic resonance (NMR). This PVPh/phenoxy blend shows single composition-dependent glass transition temperature over the entire compositions, indicating that the hydrogen bonding exists between the hydroxyl of PVPh and hydroxyl of phenoxy. The negative T _g deviation of the PVPh/phenoxy blend indicates the strong intermolecular hydrogen-bonding interaction. The inter-association constant for the PVPh/phenoxy blend is significantly higher than self-association constants of PVPh and phenoxy, revealing that the tendency toward hydrogen bonding between PVPh and phenoxy is more favorable than the intra-hydrogen bonding of the PVPh and phenoxy in the blend.     

Isothermal and Dynamic Thermogravimetric Degradation of Rigid and Plasticized Poly(Vinyl Chloride)/Poly(Methyl Methacrylate) Blends

The thermal degradation of rigid and plasticized poly(vinyl chloride) (PVC)/poly (methyl methacrylate) (PMMA) blends was investigated by means of isothermal and dynamic thermogravimetric analysis in a flowing atmosphere of air. For that purpose, blends of variable composition from 0 to 100 wt% were prepared in the presence (15, 30 and 50 wt%) and in the absence of di-(2-ethyl hexyl) phthalate (DEHP) as plasticizer. The thermal degradation of the blends was investigated by isothermal thermogravimetry at 180°C during 120 min. It was found that the main processes are the dehydrochlorination of PVC and depolymerization of PMMA. The dynamic thermogravimetric experiments were carried out in the temperature range of 30 ? 550°C. The results showed that the thermal degradation of rigid and plasticized PVC/PMMA blends in this broad range of temperatures is a three-step process and that PMMA exerted a stabilizing effect on the thermal degradation of PVC during the first step by reducing the dehydrochlorination.     

聚碳酸酯对聚偏氟乙烯结构和结晶行为的影响

通过熔融共混法制备聚偏氟乙烯/聚碳酸酯（PVDF/PC）共混物,采用X线衍射仪（XRD）和差示扫描量热仪（DSC）表征共混物的结构、熔融和结晶行为.考察不同聚碳酸酯含量对聚偏氟乙烯晶体结构、熔点以及晶体完善程度等的影响.同时通过Avram i方程和结晶速率系数的研究,探讨PC对PVDF非等温结晶动力学的影响.研究结果表明：PC的掺杂没有改变PVDF的晶体结构,但是高PC质量分数（70%以上）却不利于PVDF晶体的生成;随着PC质量分数的增加,生成的PVDF晶体完善程度逐渐降低;当PC质量分数在70%以下时,PC起到类似成核剂作用,提高PVDF结晶速率.     

Mechanical and Transport Properties of Poly(ethyleneterephthalate) Films with Reference to Sulphur Mustard

Influence of sulphur mustard (SM), a chemical warfare agent, on mechanical and transport properties of poly(ethyleneterephthalate) (PET) films was investigated. The objective of the study was to assess the agent–substrate interaction. SM induces changes in PET in that the elongation as well as strength of SM-exposed films decreases considerably. The reduction in percentage elongation at break is very significant, perhaps because of the antiplasticizing effect of SM on PET. The breakthrough time (BTT) of SM is higher for the film, which showed greater resistance to amine etching. The critical dissolution time measurement substantiates the data on mechanical behaviour of SM-exposed films. © of SCI.     

Integration of PDA Chemistry and Surface‐Initiated ATRP to Prepare Poly(methyl methacrylate)‐Grafted Carbon Nanotubes and Its Effect on Poly(vinylidene fluoride)–Carbon Nanotube Composite Properties

Poly(methyl methacrylate)‐grafted carbon nanotubes (PMMA@MWCNTs) are nondestructively prepared via the integration of mussel‐inspired polydopamine (PDA) chemistry and the surface‐initiated atom transfer radical polymerization (ATRP) method. The structures and properties of the poly(vinylidene fluoride)‐based (PVDF‐based) nanocomposites filled with pristine MWCNTs and PMMA@MWCNTs are investigated. The results show that the encapsulation of PMMA on the MWCNTs surface not only improves the dispersibility of MWCNTs in the PVDF matrix but also enhances the interfacial interaction between MWCNTs and PVDF. The addition of PMMA@MWCNTs nanofillers to PVDF can effectively induce the crystal structure of PVDF to transform from the α‐phase to the β/γ ‐phase, and nearly 100% β/γ ‐phase PVDF formed when the nanofiller loading is higher than 5 wt%. Compared with the MWCNTs/PVDF composites, the PMMA@MWCNTs/PVDF composites exhibit obvious improvement in the percolation threshold because the PMMA shells hinder the direct contact of the MWCNTs. Moreover, the loss tangent of the PMMA@MWCNTs/PVDF composites is effectively suppressed due to the reduced leakage current in the composites and the enhanced interfacial strength between the nanofiller and the matrix.     

Recyclability Studies on Poly(lactic acid)/Poly(butylene succinate-co-adipate) (PLA/PBSA) Biobased and Biodegradable Films

Poly(lactic acid)/poly(butylene succinate-co-adipate) (PLA/PBSA) blends are found promising for film packaging applications because of their flexibility, resistance, and compostability. Industrially extruded granules and films based on PLA and containing different amounts of PBSA are reprocessed through mini-extrusion, to simulate recycling, and tested in terms of their melt flow rate as a function of PBSA content. Moreover, pure PLA commercial granules and the film produced extruding the PLA/PBSA 60/40 blend are reprocessed several times by injection molding and characterized in terms of melt flow rate, mechanical properties, thermal properties, and color as a function of injection molding cycles. The variation in melt fluidity and thermo-mechanical properties is negligible up to 3 injection molding cycles for both pure PLA granules and PLA/PBSA blend. In the case of blend the change in color (yellowing and darkening) is more evident and slight local compositional change in injection molded items can be evidenced as well as a slight decrease in PBS crystallinity as a function of injection molding cycles. Nevertheless, in applications where these aspects are not critical, these materials can be recycled by extrusion or injection molding before being composted, thus prolonging their life cycle and storing carbon in them as longer as possible.     

Quantifying Structural and Solid‐State Viscoelastic Properties of Poly(propylene) (PP)/Poly(oxymethylene) (POM) Blend Films

In this study, isotactic poly(propylene) (PP)/poly(oxymethylene) (POM) blend films, including of POM as minor phase in the range of 10–30 wt%, are prepared in a twin screw extruder equipped with a slit‐die and cast film haul‐off unit. It is found that the blend films show characteristic immiscible matrix‐droplet morphology. Short‐term uniaxial tensile creep behaviors of films imply that the introducing of POM significantly improves the elastic modulus and decreases the total creep strain of PP/POM blends. Creep tests are also performed at various temperatures and long‐term deformations of samples are predicted by applying of time‐temperature superposition principle and the Findley model. It is found that the presence of POM domains into PP matrix enhances the creep resistance of PP especially at high temperatures. It is concluded that the PP‐rich PP/POM blend films show much lower short and long‐term creep strains compared to PP.

     

Gold‐Nanoparticle‐ and Gold‐Nanoshell‐Induced Polymorphism in Poly(vinylidene fluoride)

PVDF nanocomposites are prepared through solution mixing of Au‐NPs or Au‐NSs with PVDF. The novel optical properties of Au‐NPs and ‐NSs are retained as confirmed from UV‐Vis spectra. Analysis of resulting nanocomposites by FT‐IR, XRD, and DSC shows an obvious polymorphism change from α‐ to β‐form compared to PVDF prepared under the same conditions. The β‐polymorph seems to be more prominent with higher concentration of Au‐NPs (0.5%) and even more so with Au‐NSs. Thermogravimetric analysis shows that both nanocomposites have better resistance toward thermal degradation. Combination of novel optical properties of Au‐NPs or Au‐NSs with induced ferroelectric‐active β‐polymorph in PVDF can lead to new design of optical, piezoelectric devices.

     

Crystallization behavior and hydrophilicity of poly(vinylidene fluoride)/poly(methyl methacrylate)/poly(vinyl pyrrolidone) ternary blends

Ternary blends composed of matrix polymer poly(vinylidene fluoride) (PVDF) with different proportions of poly(methyl methacrylate) (PMMA)/poly(vinyl pyrrolidone) (PVP) blends were prepared by melt mixing. The miscibility, crystallization behavior, mechanical properties and hydrophilicity of the ternary blends have been investigated. The high compatibility of PVDF/PMMA/PVP ternary blends is induced by strong interactions between the carbonyl groups of the PMMA/PVP blend and the CF₂ or CH₂ group of PVDF. According to the Fourier transform infrared and wide‐angle X‐ray difffraction analyses, the introduction of PMMA does not change the crystalline state (i.e. α phase) of PVDF. By contrast, the addition of PVP in the blends favors the transformation of the crystalline state of PVDF from non‐polar α to polar β phase. Moreover, the crystallinity of the PVDF/PMMA/PVP ternary blends also decreases compared with neat PVDF. Through mechanical analysis, the elongation at break of the blends significantly increases to more than six times that of neat PVDF. This confirms that the addition of the PMMA/PVP blend enhances the toughness of PVDF. Besides, the hydrophilicity of PVDF is remarkably improved by blending with PMMA/PVP; in particular when the content of PVP reaches 30 wt%, the water contact angle displays its lowest value which decreased from 91.4° to 51.0°. Copyright © 2011 Society of Chemical Industry     

Structure and piezoelectric properties of poly(vinylidene fluoride) studied by density functional theory

The internal rotation, geometry, energy, vibrational spectra, dipole moments and molecular polarizabilities of poly(vinylidene fluoride) (PVDF) of α- and β-chain models were studied by density functional theory at B3PW91/6-31G(d) level. The effects of chain lengths and monomer inversion defects on the electric properties and vibrational spectra were examined. The results show that the tgtg′ conformation angle between g and g′ is about 55° and the ttt conformation is a slightly distorted all-trans alternating planar zigzag with ±175° repeating motif. The average distance between adjacent monomer units in the β-PVDF is 2.567 Å. The energy difference between the α- and β-chains is about 10 kJ/mol per monomer unit. The dipole moment will be affected by chain curvature (with a radius of about 30.0 Å for ideal β-chain) and by defect concentration other than localization. The chain lengths and defects will not significantly affect the mean polarizability. The calculations indicated that there are some additional characteristic vibrational modes that may help identification of the α- and β-phase PVDF.