Band 35, Heft 3

During xerographic printing processes, the electric charge properties of the paper surface are essential to obtain effective toner transfer and high image quality. Surface and volume resistance are indispensable to the accumulation of the surface charge and different resistance values generate different electrical fields with optical drum, and have a significant effect on toner transfer efficiency. In this paper, surface sizing was investigated to improve the surface properties for better toner transfer and image quality. Styrene acrylate emulsion (SAE) latex was successfully synthesized and fully characterized with a Fourier transform infrared (FT-IR) spectrometer, a laser particle analyzer and a scanning electron microscope (SEM). The results showed that under the conditions of emulsifier dosage at 3 wt%, initiator concentration at 0.5 wt% and the reaction temperature at 80°C, the monomer conversion can reach 80%. The effects of various factors including initiator dosage, emulsifier dosage and monomer ratio on the sizing performance were studied. The effects of different ratios of SAE to starch on surface and volume resistance of paper were also systematically investigated. The differences in electric properties of various paper samples were quantified and their influence on paper-toner adhesion and print quality was clarified. Relationships between electrical properties of paper and paper-toner adhesion force, and thus print quality were established. Strategies to improve printing performance through effective control of paper electrical properties were also developed. It is concluded that the best printing quality and toner adhesion were achieved when the ratio of SAE to starch is between 1:10 and 2:10.

A series of UV-cured electromagnetic shielding composites (UV-EMSC) containing different content of graphene oxide (GO) were prepared with oligomer, acrylate active diluents and different photoinitiators (Darocur 1173, Irgacure 184 or Irgacure 651). To fabricate conductive oligomer with low resistivity, polyurethane-acrylate (PUA) was used as the polymer matrix to help construct two-dimensional conductive networks consisting of GO. For forming conductive network structure, the surface functional groups (-OH, -COOH) of GO served as slightly conductive particles bonded with -NCO from the chain of polyurethane. The UV-EMSC exhibited a low resistivity of approximately 402 Ω·cm and an outstanding enhanced electrical conductivity of 249 mS/m at a GO content of 0.0200%. The effects of different photoinitiators on the properties of UV-cured films were investigated. The results indicate that the prepared UV-EMSC has great potential applications in different regions, such as in coatings of electronic, electrical, communications, plastic coatings and wood finishes.

Grafting polymerization is a valuable method for the modification of the chemical and physical properties of polymer surfaces. In this paper, the grafting of cationic vinyl monomer with quaternary ammonium groups, i.e., methacryloxyethyltrimethyl ammonium chloride (DMC), onto the isotactic polypropylene (iPP) granule was performed by the suspension solid-state grafting process. The technique offers new opportunities in modification of polyolefins, which has advantages of being solventless and having a lower process temperature. The grafted PP [PP-g-(St-co-DMC)] was systematically characterized by using various analytic tools including Fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). The FTIR spectra of the grafted iPP confirmed that DMC was successfully grafted onto the iPP backbone. The results of TGA and the hydrophilicity measurement indicated that the thermal stability of the grafted iPP was enhanced remarkably, and the hydrophilicity was also enhanced due to the addition of hydrophilic quaternary ammonium groups. Furthermore, the mechanical properties effect of PP-g-(St-co-DMC) on PP/poly(vinyl chloride) (PVC) blends was investigated. The measurements of tensile strength and impact strength indicated that the PP-g-(St-co-DMC) could remarkably enhance compatibility of PP/PVC blends. The tensile strength and the impact strength of PP/PVC blends with a concentration of PP-g-(St-co-DMC) at 4% (wt) increased up to 19.15% and 74.48%, respectively.

Thin films of chitosan acetate (CSA)-copper (II) [Cu (II)] complex were prepared by mixing Cu (II) oxide (CuO) nanoparticles in acetic acid solution of chitosan and the casting method. The changes in chemical structure of modified chitosan were confirmed by UV-Vis spectroscopy. Fourier transform infrared (FTIR) spectroscopy was applied to monitor thermal degradation processes occurring in chitosan and its composites with Cu. The changes in concentration of chitosan functional groups were observed. On a base of the kinetic constants of group thermal degradation at various temperatures, the activation energies for various groups were calculated. It was found that the presence of Cu (II) ions accelerates the thermal degradation of chitosan acetate. The higher the Cu (II) content was in the CSA matrix, the lower was the activation energy.

Three novel soluble copolymers of poly(3-penthylthiophene) [P(3PT)] and poly(3-phosphate diethyl 3-thienylmethyl) [P(3FT)] of different molar ratios of co-mers (3:1, 1:1 and 1:3) have been chemically synthesised. The final copolymers were obtained by functionalisation of poly(3-penthylthiophene-co-3-bromomethylthiophene) [P(3PT-co-3BT)] copolymers, because P(3FT) monomer does not couple in position 2-5′ of the copolymers. The structure and physical-chemical properties of resulting polymer was investigated by nuclear magnetic resonance (NMR), Fourier transform infrared spectroscopy (FTIR), visible and ultraviolet spectroscopy (UV-Vis), photoluminescence and direct current (DC) measurements. By changing the molar ratios of monomers during synthesis we can “tailor” the photoemission of resulting copolymers. The room temperature conductivity distinctly increases after doping by electrons’ acceptor. The polymers studied are good candidates for potential commercial applications.

Methyl methacrylate-co-glycidyl methacrylate copolymers (MMA-co-GMA) were prepared to compatibilize the poly(butylene terephthalate) (PBT) and polycarbonate (PC) blends. The chemical reactions between the PBT and the epoxy groups and the good miscibility between the PC and the poly(methyl methacrylate) (PMMA) phase were responsible for the excellent compatibilization effect of the MMA-co-GMA copolymers. The MMA-co-GMA copolymers decreased the melting and crystallization temperature of the PBT phase in the PBT/PC blends. Dynamic mechanical analysis result showed that the exchange reactions were inhibited due to the compatibilization reactions owing to the consumption of the carboxyl/hydroxyl end groups of the PBT phase. MMA-co-GMA copolymers decreased the phase domain size of the PBT/PC blends, and with the increase in GMA content in the MMA-co-GMA copolymers, the blends changed from a double continuous phase to a single continuous phase structure. Tensile test indicated that the yield stress, elongation at break and elastic modulus of the PBT/PC blends increased due to the addition of MMA-co-GMA. The impact strength of the blends changed unnoticeably.

Because of extraordinary physical, chemical and mechanical properties, graphene nanosheets (GNS) are suitable fillers for optimizing the properties of different polymers. In this research, the effect of GNS content (up to 1 wt.%) on tensile and flexural properties, morphology of fracture surface, and toughening mechanism of epoxy were investigated. Results of mechanical tests showed a peak for tensile and flexural strength of samples with 0.1 wt.% GNS such that the tensile and flexural strength improved by 13% and 3.3%, respectively. The Young’s modulus and flexural modulus increased linearly with GNS content, although the behavior of the Young’s modulus was more remarkable. Morphological investigations confirmed this behavior because the GNS dispersion in the epoxy matrix was uniform at lower contents and agglomerated at higher contents. Finally, microscopical observation showed that the major toughening mechanism of graphene-epoxy nanocomposites was crack path deflection, which changed the mirror fracture surface of the pure epoxy to rough surface.

A novel combination of thermal bonding and in-mold assembly technology was created to produce microfluidic chips out of polymethylmethacrylate (PMMA), which is named “in-mold bonding technology”. In-mold bonding experiments of microfluidic chips were carried out to investigate the influences of bonding process parameters on the deformation and bonding strength of microchannels. The results show that bonding temperature has the greatest impact on the deformation of microchannels, while bonding pressure and bonding time have more influence on deformation in height than in top width. Considering the bonding strength, the bonding temperature and the bonding pressure have more impact than the bonding time. The time is crucial for the sealing of the chips. By setting the bonding parameters reasonably, the microchannel deformation is <10%, while the bonding strength of the chips is 350 kPa. The production cycle of the chip is reduced to <5 min.

Sheath-core type bicomponent melt-spun fibers were produced by extruding the melts of low-isotacticity polypropylene (LPP) as the core component and the blend of LPP and high-isotacticity PP (IPP) as the sheath component. IPP content in the sheath was changed from 8 wt% to 40 wt% while sheath/core composition was varied from 50/50 to 10/90. Accordingly overall IPP content was kept constant at 4 wt%. Even though the overall IPP content was intact, bicomponent fibers with lower contraction ratio after spinning, higher elastic recovery and slightly higher modulus and strength were obtained by increasing the IPP content in the sheath and decreasing the sheath layer composition, i.e., localizing the IPP to the region near the surface in the fiber cross-section. Structure analysis of the as-spun fibers suggested the suppression of crystallization of LPP in the sheath by blending IPP. By contrast, enhancement of molecular orientation and crystallization of the sheath component were found to occur by localizing the IPP to the region near the fiber surface. It was speculated that this behavior was caused by the kinematic mutual interaction of the sheath and core components in the melt spinning process.

The microbial degradation of elastomers synthesized through the cationic polymerization reaction of linseed oil, styrene, and divinylbenzene was investigated by using the Alkaliphilus oremlandii OhILAs strain. In Fourier transform infrared (FTIR) analysis, the bound oil content in the elastomers was found to vary from 29.63 to 45.5 wt%, whereas the percentage of unreacted oil in the elastomers were in the range of 12.9–38 wt%. In 1 H nuclear magnetic resonance spectrum analysis, the unreacted oil and unreacted aromatic components in the elastomers were obtained in the ranges of 13.2–39 wt% and 6.8–16 wt%, respectively. The amount of unreacted oil in the elastomers enhanced the percentage of biodegradation, which varied from 26 to 51 wt%. The biodegradation of elastomers was also confirmed by FTIR and scanning electron micrograph analyses.