Copolymerization of benzyl methacrylate and a methacrylate bearing benzophenoxy and hydroxyl side groups: Monomer reactivity ratios,thermal studies and dielectric measurements

Statistical copolymers of 2-hydroxy-3-benzophenoxy propyl methacrylate (HBPPMA) and benzyl methacrylate (BzMA) in different feed ratios were synthesized by free radical copolymerization method at 60 °C in presence of AIBN initiator. The compositions of copolymer were estimated from ¹H-NMR technique. The monomer reactivity ratios of HBPPMA and BzMA were calculated as r₁ (r_HBPPMA)=0.51±0.076 and r₂ (r_BzMA)=1.07±0.140 for Kelen-Tüdos method, and was estimated as r₁=0.37±0.0006 and r₂=0.64±0.0485 according to Fineman Ross equation. The average values estimated from the two methods showed that monomer reactivity ratio of benzyl methacrylate was a slightly high in comparison to HBPPMA. The copolymer system showed an azeotropic point, which is equal to M _BzMA =m _BzMA =0.43. DSC measurements showed that the T_g’s of poly(HBPPMA) and poly(BzMA) were 84 °C and 73 °C, respectively. The T_g in the copolymer system decreased with increase in benzyl methacrylate content. The decomposition temperature of poly(BzMA) and poly(HBPPMA) occurs in a single stage at about 207 °C and 260 °C, respectively. Those of HBPPMA-BzMA copolymer systems are between decomposition temperatures of two homopolymers. The dielectric constant, dielectric loss factor and electrical conductivity were investigated depend on the frequency of the copolymers. The highest dielectric constants depending on all the studied frequencies were recorded for the poly(HBPPMA) and the copolymer containing the highest HBPPMA unit. The dielectric constant for P(HBPPMA) and P(BzMA) at 1 kHz are 6.56 and 3.22, respectively. Also, those of copolymer systems were estimated between these two values. Similarly, poly(HBPPMA) and copolymers, which are prepared under the same conditions show the dissipation factor and conductivity as well.     

Numerical analysis of injection molding for the Syringe Barrel with optimum design and processing condition

The numerical analysis was performed to predict the potential problem, often occurring during the manufacturing process of the disposable medical device of a great volume. The cavity filling analyses were performed for the new design of the 3cc Syringe Barrel using polypropylene(PP1), and a new nucleated polypropylene(PP2) material for better clarity. These analyses have been performed for different processing conditions as well as various wall thickness designs for both materials. With the nucleated material, only the original wall thickness design has been studied at two different processing conditions for comparison purpose. This study was conducted to investigate the optimum part design and processing condition for two different materials. The most desirable design was selected with Design 3 for material utilization and reduced flow stresses by comparing the field results. The new nucleated polypropylene provided slightly better product quality and processing.     

Application of silver nanoparticles as an antibacterial mordant in wool natural dyeing: Synthesis,antibacterial activity,and color characteristics

Madder is a natural colorant which is commonly applied with metal salts as a mordant to improve its affinity to fibers and color fastness. Madder produces an insoluble complex or lake in the presence of metal ions on mordanted fabric. In this study, wool fabric was pretreated with AgNPs (silver nanoparticles) as a mordant, then dyed with madder. The wool fabric samples were examined by scanning electron microscopy (SEM) and their colorimetric characteristics were evaluated. The formation of spherical silver nanoparticle was confirmed using UV-Visible spectroscopy, SEM images, and elemental analysis. The average size of synthesized silver nanoparticles on the surface of wool fibers is around 73 nm. The dyed wool samples were pretreated with different concentration of Ag⁺ ions or AgNPs, which showed higher color strength value compared to untreated dyed wool fabric. This pretreatment also presented good antibacterial activity.     

Investigation of mechanical properties of developed antimicrobial PPsuture/Ag nanocomposite

In order to prevent surgical complications due to microbial infections, we have developed polypropylene suture grafted with silver nanoparticles (PPsuture/Ag nanocomposite) by a simple immersion procedure. Physical and mechanical properties of developed suture are investigated. Suture surface characteristics are examined by scanning electron microscopy (SEM) imaging and atomic force microscopy (AFM). Silver content on suture surface was determined by Inductively coupled plasma atomic emission spectroscopy (ICP-AES). The mechanical properties of developed antibacterial PP suture/Ag were studied. We note that proposed silver coating method has not affected mechanical performances of suture. Antimicrobial performances of PP suture/Ag nanocomposites against S. aureus and E. coli colonies were also investigated.     

Thermal,swelling and stability kinetics of chitosan based semi-interpenetrating network hydrogels

The present study is focused on studying the swelling kinetics, thermal and aqueous stabilities, and determination of various forms of water in the chitosan (CS) and polyacrylonitrile (PAN) blend and semi-interpenetrating polymer network (sIPN). CS/PAN blend hydrogel films were prepared by solution casting technique. The blend film with optimum swelling properties was selected for the synthesis of sIPN. CS in the blend was crosslinked with the vapors of Glutaraldehyde (GTA) to prepare sIPN. The fabricated CS/PAN blend and sIPN hydrogels films were characterized with Fourier transform infrared (FTIR), thermal gravimetric analysis (TGA) and field emission scanning electron microscope (FESEM). The kinetics of swelling, bound and unbound waters and aqueous stability were determined experimentally. FESEM showed good miscibility between CS and PAN, FTIR showed no chemical interaction between CS and PAN; however, it did show a doublet for the sIPN, TGA showed improved thermal stability and swelling kinetic followed second order kinetics. The degree of swelling of the sIPN hydrogels samples at room temperature varied from ~2200 % (with a fair degree of stability (~30 %)) to ~1000 % (with high degree of aqueous stability (43 %)) with increase in the crosslinking time. The calculated unbound water (W_UB) max., for the blend was 52.3 % whereas for the bound (W_B) the max., was 41.9 %. However, for sIPN hydrogel films, the W_UB water decreased (max. 21.0 %) where as the W_B increased (max. 52.0 %). The decrease in W_UB and increase in the W_B is attributed to the formation of a compact structure and increase in the contact area between the water and polymers in sIPN hydrogels due to the induction of new water contacting point in these hydrogel films, respectively.     

Preparation of PHEMA/nHAP nanocomposites via <Emphasis Type="Italic">in situ</Emphasis> polymerization in supercritical carbon dioxide for biomedical applications

Poly(2-hydroxyethylmethacrylate) (PHEMA)/hydroxyapatite (HAP) nanocomposites were synthesized through a new route involving nano-sized HAP (nHAP) particles or modified nHAP mixed with monomer 2-hydroxyethylmethacrylate via in situ polymerization in supercritical carbon dioxide (scCO₂). Fourier-transform infrared spectroscopy showed phosphate peak increased with nHAP content in composite. X-ray diffraction patterns of PHEMA/nHAP revealed the presence of crystallized nHAP. Thermogravimetric analysis showed that the ultimate nHAP content in PHEMA/nHAP composites is consistent with its initial amount. Scanning electron microscopy revealed that nanocomposite particles are much smaller than PHEMA particles. PHEMA/nHAP composites with average diameter of approximately 600 nm were obtained in scCO₂ with 94 % yield. Mechanical properties of PHEMA/nHAP nanocomposites were better than those of PHEMA, and compressive modulus and strength of composites with 30 wt.% nHAP were 193 and 29 MPa, respectively. Nanocomposite adsorption toward bovine serum albumin was evaluated, and results indicated that analyte adsorption amount can reach up to 282 mg/g.     

The grafting of recycled polyol from waste polyurethane foam onto new polyurethane and its impact on shape recovery and water vapor permeation

Recycled polyols from waste polyurethane (PU) foams were grafted onto PU to improve the properties such as tensile strength, shape recovery, low-temperature flexibility, and water compatibility. The recycled polyol was either purified by column chromatography before grafting or was used directly for grafting. The soft segment melting temperature of PU did not notably increase with the addition of polyol, whereas the glass transition temperature increased with increased polyol content. The tensile strength sharply increased at low polyol content and decreased at high polyol content, while the strain at break did not significantly change with an increase in polyol content. The shape recovery at 10 oC notably improved compared with unmodified PU and remained high after four cyclic tests. Polyol-grafted PU demonstrated better lowtemperature flexibility and reduced the water vapor permeability of PU membranes. Overall, grafting recycled polyol onto PU significantly improved the tensile stress, shape recovery, and low-temperature flexibility of PU.     

Synthesis and characterization of a novel charring agent and its application in intumescent flame retardant polyethylene system

A novel charring agent poly(pentaerythritol spirocyclic phosphorusoxy spirocyclic diethanolamine borate) (PPSPSDB) was synthesized successfully with diethanolamine borate (DEAB) and spirocyclic pentaerythritol bisphosphorate disphosphoryl chloride (SPDPC), which was combined with ammonium polyphosphate (APP) to endow linear low-density polyethylene (LLDPE) with flame retardance. The structure of PPSPSDB was characterized by FTIR and 1H-NMR. The study of thermal stability of various LLDPE composites showed that PPSPSDB/APP system could effectively improve the thermal degradation and thermal-oxidative stability of the char residues, and PE3 containing 30 wt% APP/ PPSPSDB with a 2 weight ratio left the highest amount of char residue at 800 oC. The results of flammability revealed that PE3 had the best combination property; the limited oxygen index value was 29.6, and vertical burning reached UL-94 V-0 rating, and the tensile strength and notched impact strength were 11.853 MPa and 28.8 kJ/m2 respectively. The investigation of structure and morphology of char residue indicated that the compact foaming char layer, as a good barrier against the transmission of heat and volatiles, was formed for PE3 during combustion.     

An investigation on the comparison of wet spinning and electrospinning: Experimentation and simulation

Polysulfonamide (PSA) has been widely used in many fields because of its excellent thermodynamic properties. In this study, PSA fibers were prepared separately via two different spinning ways, including conventional wet spinning and electrospinning. Fluid motion of wet spinning and electrostatic field of electrospinning were modeled using finite element analysis to investigate the spinning process. The properties of fabricated PSA fibers were characterized systematically by scanning electron microscope (SEM), fourier transform infrared spectrometer (FTIR), X-ray diffraction (XRD), thermal gravity analysis (TGA) and electronic strength tester. Based on the simulation and theoretical analysis of spinning process, it was found that the extruding force of the wet spinning is larger than that of the electrospinning. The larger extruding force makes the alignment of macromolecules inside fiber relatively uniform, and a higher proportion of crystallization happens. Accordingly, the mechanical properties and thermal stability of PSA fibers could be improved due to a higher proportion of crystallization. The experimental results of mechanical strength and TG test are coincided with the simulation results. PSA fiber prepared by wet spinning has better thermal stability and mechanical properties than that fabricated by electrospinning.     

Electrical properties of graphene/waterborne polyurethane composite films

Graphene is classified as a carbon-based material. Structurally, graphene is made up of carbon-based two-dimensional atomic crystals and a one atom thick planar sheet of sp²-bonded carbon atoms. This sort of arrangement in graphene makes it a unique material with exceptional mechanical, physicochemical, thermal, electrical, optical, and biomedical properties. Methods for graphene-based fabric production mainly use graphene-based materials such as graphene (G), graphene oxide (GO), and reduced graphene oxide (rGO) coated on fabric or yarn. Waterborne polyurethane (WPU) is one of the most rapidly developing and active branches of polyurethane chemistry. More and more attention is being paid to graphene-coated fabrics owing to their low temperature flexibility, the presence of zero or very few VOCs (volatile organic compounds), water resistance, pH stability, superior solvent resistance, excellent weathering resistance, and desirable chemical and mechanical properties. It is used as a coating agent or adhesive for fibers, textiles, and leather. Also, graphene-containing materials have been used to enhance the properties of WPU. In this study, graphene/WPU composite solution and film was prepared to conduct basic research for developing electrical heating textiles which is not harmful to the human body, flexible and excellent in electrical properties. Graphene/WPU composite solutions were prepared with a graphene content of 0, 2, 4, 8, and 16 wt%, and graphene/WPU film was prepared with solution casting method. The graphene contents were analyzed for their surface morphology, electrical properties, and electrical heating properties.