Crosslinking of Polymers

Chitosan film reinforced with nano-sized chitin whiskers and crosslinked using tannic acid was synthesized by the casting-vaporation method. The mechanical and physicochemical properties of several film samples (consisting of different ratio of chitin and tannic acid) were compared with neat chitosan. Tensile tests show that the addition of chitin improves the nanocomposite films mechanical properties up to 137% compared to neat chitosan, but this is slightly degraded when tannic acid is introduced. However, tannic acid and chitin whisker content greatly reduced moisture content by 294% and water solubility by 13%. Transmission electron microscopy (TEM) and Fourier-transform-infrared spectroscopy (FTIR) were used to investigate the morphology and molecular interaction of film. X-ray diffraction results indicated that the samples with chitin whiskers had a more rigid structure. The addition of tannic acid changed the structure into an anhydrous crystalline conformation when compared to neat chitosan film. (C) 2014 Elsevier Ltd. All rights reserved.

Dear readers,
If you like to have the full paper, please send an email request to [email protected]. We will email the paper to you. Thank You.

http://www.sciencedirect.com/science/article/pii/S0144861714008844 
http://www.ncbi.nlm.nih.gov/pubmed/25439908 
http://eprints.um.edu.my/11629/

Corn fibers and luffa peels were evaluated for removing toxic heavy metal ions and dissolved organic dyes from water. Fresh peels were pretreated to remove all soluble components before using them for extraction studies. Presence of eOH and eCO 2 H functional groups on the surface of the peels and rough morphologies were characterized using Fourier transform infrared spectroscopy and scanning electron microscopy investigations, respectively. Corn fibers and luffa peels showed maximum extraction effi-ciencies within the pH range of 4e10 and adsorption reached a steady state within 2e3 h. Prewashed corn fibers and luffa peals extracted 159 mg g À1 and 90 mg g À1 of alcian blue, 70 mg g À1 and 124 mg g À1 of methylene blue, 50 mg g À1 and 108 mg g À1 of neutral red as well as 35 mg g À1 and 40 mg g À1 of coomassie brilliant blue from water, respectively. Both materials did not show significant extraction affinity towards heavy metal ions such as Pb 2þ (1 mg g À1), Ni 2þ (4 mg g À1 for corn fiber and 12 mg g À1 for luffa peels), and chromate (3 mg g À1 for corn fibers and 6 mg g À1 for luffa peels) ions from water. The Langmuir and Freundlich isotherms were used to understand the adsorption process on the surface of the adsorbents. Langmuir isotherm model yielded the best fit for the data obtained in the study, indicating a monolayer adsorption of pollutants on the adsorbent surface. Both adsorbents can be regenerated at acidic pH and could be reused for up to five cycles without significant loss of efficiency. Our experimental results suggest that both natural materials are effective towards removing dissolved dyes from water.

In the current work, a comparative study of the influence of 3 wt. % montmorillonite nanoclay Nanomer® I.30E (MMT), 0.2 wt. % graphene nanoplatelets (GNP) and two binary systems; (a) 3 wt.
% MMT and 0.1 wt. % GNP; and (b) 3 wt. % MMT and 0.2 wt. % GNP on mechanical and viscoelastic properties, and thermal stability of SC-780 epoxy resin composite was investigated. Epoxy SC-780, a two-part diglycidyl ether of bisphenol A (DGEBA) resin system, was modified with
silane functionalized GNP and octadeclyamine modified MMT. Mechanical and viscoelastic properties were characterized using three-point flexure test and dynamic mechanical analysis (DMA) respectively and compared to that of unmodified composite counterpart. X-ray diffraction studies
conducted to investigate the dispersion of MMT, GNP and binary systems in epoxy resin nanocomposites showed good dispersion, leading to significant enhancement in material properties. Flexural strength and modulus increased by 14, 30, 40 and 29%; and, 40, 129, 146 and 150% for 0.2 wt. % GNP, 3 wt. % MMT, and binary systems (a) and (b) infused composite samples respectively. Similarly, storage modulus also increased by 7, 15, 16 and 8% in the order stated above respectively. On the other hand, there were no significant changes in glass transition temperature in all nanocomposites compared to unmodified control system. All nanocomposites showed enhanced thermal stability compared to unmodified epoxy composite.

As for nanofillers in general, the properties of carbon nanotube (CNT)-polymer composites depend strongly on the filler arrangement and the structure of the filler network. This article reviews our actual understanding of the relation between processing conditions, state of CNT dispersion and structure of the filler network on the one hand, and the resulting electrical, melt rheological and mechanical properties , on the other hand. The as-produced rather compact agglomerates of CNTs (initial agglomerates, >1 mm), whose structure can vary for different tube manufacturers, synthesis and/or purification conditions, have first to be well dispersed in the polymer matrix during the mixing step, before they can be arranged to a filler network with defined physical properties by forming secondary agglomerates. Influencing factors on the melt dispersion of initial agglomerates of multi-walled CNTs into individualized tubes are discussed in context of dispersion mechanisms, namely the melt infiltration into initial agglomerates, agglomerate rupture and nanotube erosion from agglomerate surfaces. The hierarchical morphology of filler arrangement resulting from secondary agglomeration processes has been found to be due to a competition of build-up and destruction for the actual melt temperature and the given external flow field forces. Related experimental results from in-line and laboratory experiments and a model approach for description of shear-induced properties are presented.

The global polymer industry needs the polymeric materials to be bio-compatible and bio degradable. For this purpose we have focused and worked on a biodegradable and environment friendly polyurethane polymer. In this work we have used dextrin (from corn starch) as the basic component which work as chain extender in the polymerization reaction. The isophorone diisocyante (IPDI) is reacted with polycaprolactone diol (PCL) in the first step. Bentonite nanoclay is also dispersed with this matrix to enhance the strength of the polymer. And in the final step chain extenders are added including dextrin and 1,4 BDO. The synthesized polymer is highly eco friendly and has good strength as compared to the older version.

Now a days, polylactic acid (PLA) and its derivatives are receiving significant attention due to its
versatile applications. The present study provides a deep insight on major structural and
functional properties of novel PLA-HA polymer synthesized by incorporating humic acid (HA)
in PLA. Topographical features of both pure and modified PLA have been studied using SEM
and AFM to analyze their comparative surface microstructures. Incorporation of HA was found
to enhance slightly the thermal stability profile of the polymer. However, reduction of Tg, Tm and
degree of crystallinity has also been noticed, which in turn resulted in enhanced ductility and
higher elongation at break. Moreover, improvement in radical scavenging properties, total
available phenolics (0.075 μmole GAE/g film) and water absorption capacity (90.65%) has been
observed which essentially suggested introduction as well as enhancement of several utility
features, originally absent in pure PLA. The study thus predicts multifaceted applications of
PLA-HA polymer, from industrial packaging to fabrication of biomedical devices depending on
its superior characteristics as compared to pure PLA.

Heat resistant conveyor belts are critical assets for a pelletizing plant because of the losses that their failures cause. Accordingly, the life cycle of these conveyor belts should be evaluated during work, in order to assist their maintenance, and, in this context, this study proposes the use of material characterization and thermal degradation of the conveyor belts components. The characterizations were performed in a comparative way between three different kinds of heat resistant conveyor belts supplied to a global mining company. The belts carcasses were characterized by FT-IR aiming at the polymers qualitative analysis. Similarly, the rubbers were characterized by the analysis of their pyrolyzed products by FT-IR and their crosslinks densities were evaluated by the use of the Flory-Rehner equation after the swelling of the rubbers, which helped to justify the belts behavior under thermal degradation, studied in a previous work. Using these results and data of mechanical properties variation according to time and process temperature, it was possible to establish the rate of damage done to each conveyor belt and, applying real process data, the belts performance during work could be evaluated.

Keywords: Conveyor belts. Synthetic fibers. EPDM. FT-IR. Flory-Rehner equation.

In this work, poly vinyl alcohol (PVA) membranes filled with and without molecular sieves are prepared by solution casting method. Later, they are chemically cross-linked with glutaraldehyde (GA). The resulting samples were investigated and characterized by various characterization techniques viz.; Contact Angle measurement (hydrophilicity measurement), Fourier Transform Infrared Spectroscopy (FTIR), X Ray Diffraction (XRD). The nanostructure of the resulting membranes was investigated by Scanning Electron Microscopy (SEM). The infrared spectra of the cross-linked PVA showed absorption bands of the acetal bridges resulted from the reaction of the GA with the OH groups from PVA. Also the FTIR spectroscopy and XRD was used to determine the crystallinity of the PVA film.. The results have showed an increase of hydrogel crystallinity with higher percentage of GA.

Ethylene-octene copolymer (EOC) was irradiated using electron beam irradiation at different dosages (30, 60, 90, and 120
kGy). Effect of irradiation dosage on thermal and mechanical properties was studied. When compared to low density polyethylene,
EOC exhibited higher degree of crosslinking reflected in increased gel content, higher elastic modulus (G0), and lower tan d obtained
by rheology measurement at 150
C. Crosslinking caused improvement in high-temperature creep and room temperature and also elevated
temperature elastic properties. Differential scanning calorimetry revealed that e-beam irradiation has caused a gradual reduction
in crystallinity and a presence of a fraction with higher melting temperature. In the case of EOC, as the extent of crosslinking
increased, stress at break showed an increasing trend whereas irradiation dosage had an inverse effect on elongation at break. Radiation
dosage has positive effect on thermal stability estimated by thermogravimetric analysis. After 30 min of thermal degradation at
220
C, slightly higher C=O peak for crosslinked sample was found by Fourier transform infrared spectroscopy while for room temperature
samples no C=O peak was detected.

A controlled release fertilizer systembased on phosphate bound-carboxymethyl starch-graft-polyacrylamide (PCMS-
g-PAM) has been prepared in order to deliver the phosphate fertilizer to the plant at a constant rate thereby.
This system aims to increase fertilizer phosphorus use efficiency (FPUE) and maintain a hydration level for the
plant at the same time. Two types of starch phosphate monoesters were prepared using mono-ammonium  (MAP) and di-ammonium phosphate (DAP). First, starch was converted to carboxymethyl starch and then was phosphorylated with mono-ammonium dihydrogen phosphate and di-ammonium dihydrogen phosphate.
After phosphorylation, the samples were grafted with acrylamide in the presence of methylene bisacrylamide as a crosslinking agent. The prepared systems of P-CMS-g-PAM were differently characterized by Fourier transformer infrared (FT-IR), thermogravimetric analysis (TGA), scanning electron microscope (SEM) and phosphorous analysis. The swelling behavior was investigated. The kinetics of grafting reaction were also studied. The release behavior of phosphate bound was studied at pH 7 and 25 °C. The mechanism of the phosphate release from P-CMS-g-PAM was examined using the Korsmeyer-Peppas model.

In this research, oxidized sucrose, a novel aldehyde-based green cross-linker, endowed starch films with substantial improvement in both tensile strength and elongation, whereas many other cross-linkers did not. Starch films are usually weak, brittle, and highly moisture sensitive, and thus have restricted industrial applications. Cross-linking is one of the most common methods to tackle these problems. However, most of the available cross-linkers are either toxic, expensive, or with low cross-linking efficiencies. Oxidized sucrose is a green cross-linker with multiple aldehyde groups per molecule to cross-link starch molecules via forming hemiacetals/acetals. The starch films cross-linked with oxidized sucrose had tensile strength and breaking elongation of 23 MPa and 60%, respectively, exceeding the cross-linking results of many other cross-linkers. Oxidized sucrose cross-linking also substantially increased the stability of starch films in both water and formic acid. With activation energy as low as 33.22 kJ mol −1 , the cross-linking, a pseudo-first-order reaction, could occur readily. Mild cross-linking using oxidized sucrose might provide an alternative to promote industrialization of starch-based products.

In the present work, the synthesis of k-carrageenan-crosslinked poly(acrylonitrile co-acrylamide) hydrogel through copolymerization of acrylonitrile and acrylamide. The optimum conditions for the synthesis of k-carrageenan-crosslinked poly(acrylonitrile co-acrylamide) hydrogel were determined by varying several parameters such as monomers, cross linker, initiator and reaction time. The structure and morphology of the synthesized hydrogel and the exposed hydrogel (containing Brilliant Green) were characterized by FT-IR and adsorption experiments were carried out using various adsorbent dosages. The adsorption kinetics results showed that the adsorption followed pseudo-second order, this implies that the adsorption of the dye took plase through chemisorption mechanism.

The method for chitosan (CS) covalent immobilization onto NH2-functionalized magnetite nanoparticles surface is presented. Covalent binding of CS to the magnetite surface proceeds using a free -CH2OH group of CS and a NH2-group of magnetite with epichlorohydrin (ECH) as a cross-linker. The obtained nanocomposites were functionalized by diethylenetriaminepentaacetic acid (DTPA)-groups. Composites were characterized by elemental analysis, FTIR, XPS and ASAP methods. The total content of organic phase (CS-DTPA) in the hybrid material, appreciated by thermogravimetric analysis (TGA), was 3.7%. Considering the atomic ratio between oxygen in CS and oxygen in ECH residue, the chemical structure of the hybrid material is proposed. The adsorption of Gd-DTPA and Gd3+ on the obtained nanocomposite was studied. The Freundlich isotherm fits all the experimental data better than the Langmuir adsorption.

Interpenetrating  network  (IPN)  blend  microspheres  of  poly(vinyl
alcohol) (PVA) and methyl cellulose (MC) were prepared to study
their controlled release (CR) characteristics of two drugs viz., watersoluble  losartan  potassium  (LK)  and  water-insoluble clopidogrel
bisulphate  (CB)  that  belong  to  the  class  of  antihypertensive  drugs.
Microspheres (dia = 1  µm) were prepared by  emulsion crosslinking
method using glutaraldehyde as the crosslinking agent. Drug-loaded
formulations  were  characterized  by  Fourier  transform  infrared
(FTIR) spectroscopy to investigate the chemical interactions of drugs
with the IPN matrix. The X-ray diffraction (XRD), scanning electron
microscopy  (SEM),  differential  scanning  calorimetry (DSC)  and
universal testing machine (UTM) were employed to characterize the
developed  formulations.  Equilibrium  swelling  of  the matrices  was
performed  in  pH  7.4  buffer  media,  while  the  in  vitro release  was
performed  in  both  pH  1.2  and  7.4  buffer  media  to  understand  the
release profiles of the drugs in simulated stomach as well as intestinal
conditions,  respectively.  The  in  vitro release  data  were  analyzed
using empirical equations to understand the mode oftransport.

Melt processable pseudointerpenetrating polymer networks (pseudo- or semi-IPNs) of silicones in thermoplastic matrices and methods of producing same are provided by vulcanizing the silicones within the matrices. The silicone component of the network is preferably the reaction product of a polymeric hydride group - containing silicone and a polymer containing at least one unsaturated group, preferably a vinyl group. The polymer containing unsaturated groups may be a silicone polymer also, or may be a non-silicone polymer such as a styrene, butadiene or urethane polymer or copolymer. Depending on certain parameters chain-extended (thermoplastic) or cross-linked (thermosetting) compositions are produced.

En esta investigación se obtiene un polímero biodegradable a partir del almidón de yuca al procesar mezclas de almidón modificado con glicerina y agua como plastificantes, utilizando un molino abierto y una extrusora de monohusillo. Las variables a controlar durante la extrusión son: perfil de temperatura, torque, y velocidad de rotación del husillo. Se evalúan características mecánicas y fisicoquímicas mediante ensayos de tensión, análisis térmicos de Calorimetría Diferencial de Barrido (DSC) y Análisis Termogravimétrico (TGA), Análisis Infrarrojo por Transformadas de Fourier (FTIR) y morfología.

PACS: 81.70.Pg, 87.85.J-

Poly(acrylamide-1-allyl-2-thiourea) hydrogels, Poly(AA-AT), were synthesized by gamma irradiation using 60Co g source in different irradiation dose and at different 1-allyl-2-thiourea content in the monomer mixture. For the characterization of the hydrogels, Fourier transform infrared spectrometer (FT-IR), thermogravimetric analyzer (TGA), elemental analyzer and the swellability of the hydrogels were used. It was noted that 1-allyl-2-thiourea in the synthesized hydrogels was increased by the increasing the content of the 1-allyl-2-thiourea in the irradiation monomer mixture and increasing the radiation dose for the hydrogel synthesis.

Nanocelluloses (NCs) have remarkable mechanical properties
and contain abundant surface functional groups that can be
modified or cross-linked with other materials. They have been
widely used as an environment-friendly reinforcing agent in
polymer composites. However, for applications that are carried
out in humid environments or aqueous suspensions, hydrophilicity
of NCs lower their mechanical integrity. Hence, cross-linking
techniques have been investigated in recent years for preparing
NC-based materials that are dimensionally stable under
humid or aqueous environments and have better physicochemical
properties. This Minireview examines the quickly
growing field of cross-linked NC-based materials, which have
many benefits including improved aqueous, structural, mechanical,
and thermal stability. In addition, the potential application
of cross-linked NC-based materials in adsorption of
heavy metal is discussed.

Conductive polymers, based on their redox state and dopant strength, exhibit a vast range of conductivity from metallic to insulator, mostly applied as semiconductors. In general, conductive polymers are not thermoformable; they are organic materials like insulatingpolymers. They can offer a high electrical conductivity, but do not necessarily reveal similar mechanical features in comparison with other commercially available materials. The electrical properties of PANI are to a large extent adjusted for specific usage. Since conducting polymers like PANI have backbones of adjacent sp2 hybridized carbon centers, they provide one valence electron on each center in a pz orbital orthogonal to the other three sigma bonds, which are combined with each other to a set of orbitals of wide delocalized molecules. The presence of highly mobile electrons in the delocalized state of a “doped” condition resulting from oxidation causes the removal of some of the delocalized electrons. As a result, the conjugated p-orbitals form a one-dimensional electronic band in assist, with electrons within such band becoming mobile when it is partially emptied. The band structures of a conductive polymer can be easily calculated with a tight-binding model based on the wave function set of isolated atom superposition. In principle, the reduction process is used for doping such materials for which unfilled bands are loaded by electrons. In practice, p-type semiconductors are commonly prepared by oxidative doping.

The styrene-butadiene-styrene (SBS) is a thermoplastic copolymer commonly used as pressure sensitive adhesive (PSA), due its they are highly flexible and elastics, that produce high cohesive strength that results in physical interactions caused by polystyrene (PS) blocks. However, SBS-based PSA's restrain their adhesion properties around their glass transition temperature (Tg), so it is necessary to add a crosslinking agent to increase their thermal resistance. Crosslinking is an important process in adhesives formulations, due that the mechanical properties of adhesive improve, but not enough information I published about the kinetic of that process. One of most studied crosslinking agent for adhesive formulations is dicumyl peroxide (DCP), which shows a good combination of physical and chemical properties to adhesive during crosslinking process. This report presents a crosslinking process using DCP as crosslinking agent. The study of kinetic parameters was determined by differential scanning calorimetry (DSC) in isothermal and dynamic conditions, from which the order of the crosslinking process reaction was found to be first order, according to the Kissinger and Ozawa models. The adhesive and cohesive strength was evaluated through the failure criterion between the bonds of the adhesive line using the single lap join method (SLP), showing that the best performance was that of the formulation made from resin Sylvalite RE100L and 0.81phr of DCP.

Melamine formaldehyde (MF) resin was synthesized by the reaction between melamine and formaldehyde under alkaline condition in tetrohydrofuran medium with 1:3 melamine to formaldehyde molar ratio. The synthesized resins were characterized by differential scanning calorimetry (DSC), Fourier transform infrared spectroscopy (FTIR) and thermal gravimetric analysis (TGA). Curing and reaction mechanism was studied by thermal and spectroscopic analysis. Two exothermic peaks were observed in the DSC analysis indicating a two-step crosslinking reaction process was correlated to TGA analysis. FTIR studies at different temperatures explained the two-stage curing mechanism which is concurring with the DSC data. At a temperature range of 140-160 1C, reversible demethylolation is dominating to the crosslinking reaction. At temperature 4160 1C, the crosslinking reaction dominates. On the basis of DSC and FTIR data, a possible crosslinking reaction route was derived and explained. The first stage of curing is the conversion of methylol groups to primary amine and the second stage is the crosslinking of methylol groups to the final product, methylene bridges. The thermal stability of the methylol groups, methylene bridges and the triazine ring, as well as the evaporation of effluents at different stages of curing, are also discussed based on combined TGA and DSC results.

A useful pectin-enriched fraction (PEF) extracted through high-power-ultrasound (HPUS) pretreatment and sodium carbonate was efficiently obtained from discarded carrots. Formerly, the effect of HPUS-power intensity and time (A: 40 min-2.08 W/cm2 ; B-E: 5–20 min ≈ 10 W/cm2 ) on carrot powder (CP) used for PEF-isolation, was investigated. Reducing carbohydrates-, cell-wall neutral sugars- (NS), uronic acids- (UA) of pectins, and protein releases increased with HPUS-energy. CP had antioxidant capacity, containing α- and β-carotene, lutein, αtocopherol. Only HPUS B-E treatments (≈10 W/cm2 ) were capable to produce matrix disruption, promoting polymers' release. CP pretreated through selected E-treatment (20 min; ≈10 W/cm2 ) followed by 0.1M-Na2CO3 (1 h-stirring) extracted the whole pectin content of CP (UA = 14.0%). PEFs were orange, with co-extracted antioxidants. More substituted (1.27 NS/UA ratio) three lower molecular weights' components of HPUS-PEF produced higher Newtonian viscosity before shear-thinning, and calcium-crosslinked gels with lower elastic modulus (G’ = 12Pa). Sustainable HPUS/Na2CO3 method isolated efficiently an antioxidants-carrying PEF useful as functional food additive.

In this study, both boron-doped and -undoped poly(vinyl alcohol)/ Calix[4]arene fibers were prepared by using an electrospinning technique. Obtained fibers were characterized by FT-IR, DSC, and SEM techniques. The DSC results show that the degradation of the boron-doped fibers started at much higher temperatures. This result indicates the addition of boron increased the thermal stability of the fibers. SEM pictures show that both of the fiber samples are nonbeaded with diameters ranging from 0.5 to 1 lm. The fiber diameters are not homogeneous and uniformly distributed for boronundoped samples.

Excessive water production is one of the biggest problems commonly found in the brown water-flood field. There are two treatments of water shut-off (WSO) in hydrocarbon wells. The mechanical WSO is a routine operation that is commonly carried out and is part of standard well work; meanwhile, the chemical WSO is a specific treatment. The study aims to identify the effect of polymer concentration, injection rate, and soaking time on the effectiveness of chemical WSO with cross-linked polymers in a specific field. The study proposes and analyses the optimization of this treatment in the 7E Sandstone field by utilizing a conceptual simulation model. Geographically, this field is located in the Central Sumatera basin. The field is a moderately homogenous sandstone. Last decade, the 7E field was associated with excessive water production issue, some mechanical WSO has been done to solve the problem, but less effective and inefficient. Hence chemical WSO job comes as a promising option to overcome this problem robustly. The cross-link polymer injection treatment is the action of blocking water from entering and reaching production wells by using a mixture of polymer, cross-linker, and water. A base case of the conceptual model has been developed, then over twenty injection scenarios wide-ranging based on polymer concentrations are implemented in the model. Each of these concentration schemes is simulated using different injection flow rates for the total injection volume of 2000 bbl. The injection rate sets at 1000 bbl/day for twice injection and 2000 bbl/day for one injection. Soaking time is settled for one, two, and three days to give time for generating gelatin. A comparison of water production before and after the WSO is used to investigate WSO effectivity. The simulation result mentions that the WSO implementation can decrease excess water from 385,143 bbl to 186,189 bbl.

Ethylene-octene copolymer (EOC) was
crosslinked by dicumyl peroxide (DCP) at various temperatures
(150–200
C). Six concentrations of DCP in range
0.2–0.7 wt % were investigated. cross-linking was studied
by rubber process analyzer (RPA) and by differential
scanning calorimetry (DSC). From RPA data analysis
real part modulus s’, tan d, and reaction rate were investigated
as a function of peroxide content and temperature.
The highest s’max and the lowest tan d were found
for 0.7% of DCP at 150
C. Chain scission was analyzed
by slope analysis of conversion ratio, X in times after
reaching the maximum. Less susceptible to chain scission
are temperatures in range 150–170
C and peroxide levels
0.2–0.5%. Heat of reaction was analyzed by DSC at
various heating rates (5–40
C min
1). It was found to be
exothermic. By projection to zero heating rate, the reaction
was found to start at 128
C with the maximum at
168
C.

The present study involves synthesis of polylactic
acid (PLA) using purified lactic acid from fermented broth
of Jackal jujube (Zizyphus oenophlia). A polyphenolic
compound, humic acid (HA) of biological origin was
incorporated to the PLA in order to reinforce the PLA
chain without compromising its biodegradability and biocompatibility.
Under optimized conditions of polymerization,
modified L-PLA yield improved up to 93%. The molecular
weight was found to be 6.4×105. Different physicochemical
properties of the polymer were explored for its further
application in different fields. Incorporation of intermolecular
bond between PLA and HA was confirmed by FT-IR
spectroscopy technique. Addition of HA not only reduced
the crystallinity of PLA, but also had increased flexibility
and elasticity to much greater extent. The results showed
that, apart from enhancing the physicochemical properties
of PLA, the process also had reduced the production cost
of the polymer, while mitigating the demands of
environmental protection agencies.

A series of antibacterial hydrogels were fabricated from an aqueous solution of AgNO 3 , gelatin and carboxymethyl chitosan (CM-chitosan) by radiation-induced reduction and crosslinking at ambient temperature. The nanosilver particles were in situ synthesized accompanying with the formation of gelatin/CM-chitosan hydrogel. Transmission Electron Microscope and UV-vis analysis have verified the formation and homogeneous distribution of nanosilver particles in the hydrogel matrix. The nanosilver/ gelatin/CM-chitosan hydrogels possessed interconnected porous structure, had a compressive modulus of 44 to 56 kPa, and could absorb 62 to 108 times of deionized water to its dry weight. Furthermore, the hydrogels were found to have sound antibacterial effect on Escherichia coli (E. coli), and their antibacterial ability could be significantly enhanced by the increasing of AgNO 3 content. The comprehensive results of this study suggest that nanosilver/gelatin/CM-chitosan hydrogels have potential as an antibacterial wound dressing.

A series of antibacterial hydrogels were fabricated from an aqueous solution of AgNO 3 , gelatin and carboxymethyl chitosan (CM-chitosan) by radiation-induced reduction and crosslinking at ambient temperature. The nanosilver particles were in situ synthesized accompanying with the formation of gelatin/CM-chitosan hydrogel. Transmission Electron Microscope and UV-vis analysis have verified the formation and homogeneous distribution of nanosilver particles in the hydrogel matrix. The nanosilver/ gelatin/CM-chitosan hydrogels possessed interconnected porous structure, had a compressive modulus of 44 to 56 kPa, and could absorb 62 to 108 times of deionized water to its dry weight. Furthermore, the hydrogels were found to have sound antibacterial effect on Escherichia coli (E. coli), and their antibacterial ability could be significantly enhanced by the increasing of AgNO 3 content. The comprehensive results of this study suggest that nanosilver/gelatin/CM-chitosan hydrogels have potential as an antibacterial wound dressing.

A facile synthetic strategy for preparing hydroxylated
polymethacrylate amphiphilic block copolymers
(PCzMMA-b-PBMMA, PFlMMA-b-PBMMA) incorporated with
primary and secondary hydroxyl groups and electroactive moieties
along the polymer backbone is reported. Full characterization,
structure-property relationship and self-assembly of these
polymers are discussed. Due to interplay of hydrophobic/
hydrophilic interactions, PCzMMA-b-PBMMA formed a layered
lattice and PFlMMA-b-PBMMA showed a vesicular morphology.
Electropolymerization of the electroactive units led to the
formation of cross-conjugated polymer network in solution and
in thin films. The network structure was characterized with a
range of spectroscopic techniques. Such highly processable
polymers may be of interest to applications in which a conducting
amphiphilic films with strong adhesion to various substrates
are required.

In this article, genipin cross-linked kappa-cararageenan/ hydroxyethyl cellulose hydrogels are prepared and the effect of cross-linking on hydrogels characteristics is investigated. Swelling and transform mechanism of both native and cross-linked gels in different pH is also studied. It is found that the concentration of genipin can affect the physical stability of gels. An optimum concentration of cross-linker that hydrogel molecular structure can be in its most stable form is also discussed. Native hydrogels exhibited more swelling in alkaline medium than acidic and neutral; however, by increasing the cross-linker concentration, the swelling ability in neutral medium increased so that genipin cross-linker hydrogels could swell in pH 7 more that pH 1.2 and 12. Fourier transform infrared spectroscopy (FTIR) is applied to study the formation of new bonding due to genipin reactions and explain hydrogels stability in various concentrations. Differential scanning calorimetry (DSC) measurements reveal that by increasing genipin, gels ability to hold water increases to some point and then decreases due to less structural stability. X-ray diffraction (XRD) and field emission scanning electron microscope (FESEM) test were performed to study the crystallinity changes and microstructure of hydrogels. Finally, power law model is applied to study the transform mechanism of hydrogels.

Ethylene–octene copolymer (EOC) was cross-linked by dicumyl peroxide (DCP) at various temperatures (150–200°C). Six concentrations of DCP in range 0.2–0.7 wt.% were investigated. Cross-linking was studied by rubber process analyzer (RPA). From RPA data analysis real part modulus s′, tan(delta) and reaction rate constant K were investigated as a function of peroxide content and temperature. The highest s′max and the

In this paper, crosslinking process and thermo-mechanical properties of epoxy materials containing diglycidyl ether bisphenol-A (DGEBA) as the epoxy resin and JEFFAMINE ® D-230 polyoxypropylenediamine as the hardener have been studied using molecular dynamics simulation. An algorithm to create the crosslinked epoxy has been developed, and the crosslinking process is monitored. The simulation results disclose the effectiveness of the using annealing in the crosslinking process to achieve higher crosslinking densities within shorter reaction radiuses while producing more desirable conformation. The evolution of the complex network of cured epoxy is studied by radial distribution function (RDF). The important properties of the epoxy material such as glass transition temperature (T g ), the coefficient of thermal expansion (CTE), and elastic constants are calculated. Furthermore, the variation of the properties through the evolution process is considered, and the improvement of them is captured. The results obtained from our simulation are in good agreement with the experimental results, revealing the strength of molecular dynamics to predict the material properties.

This study was conducted to explain the tensile strength loss of wood due to the modification with 1,3-dimethylol-4,5-dihydroxyethyleneurea (DMDHEU) and glutaraldehyde (GA). Modified and control wood blocks were macerated to deliberate fibres, and handsheets were produced thereof. The nitrogen content of the fibres indicated that maceration removed the major proportions of DMDHEU. The stability of GA in wood during maceration was not assessed. Tensile strength determined at zero span (z-strength) and finite span (f-strength) was equal for the handsheets from DMDHEU-modified fibres and the control handsheets. The microscopic appearance of the tested finite-span paper strips from DMDHEU-modified fibres mainly indicated interfibre failure and did not differ from the fibre fracture mode of the control handsheets. In contrast, the z-strength of the handsheets from GA-modified fibres was lower than that of controls and decreased with increasing content of GA in the initial modified wood. ...

We present the preparation and characterization of viscoelastic formulations of hyaluronic acid functionalized with polymerizable methacrylate groups. We explored three different processing strategies for controlling microstructure and interchain interactions: lightly cross-linked near-gels, emulsion-cross-linked microspheres, and an elastic microgel formed through centrifuging the microspheres. The component structure and rheological properties of these formulations were compared to those of high molecular weight hyaluronic acid solutions, which displayed classical behavior of high molecular weight polymer solutions reported by other investigators. We demonstrate that these processing strategies allow the tuning of solution properties from strongly viscoelastic behavior, observed in lightly cross-linked near-gels and concentrated microsphere solutions to elastic behavior in elastic microgels, behaving like pseudoplastic liquids having a well-defined yield stress above which viscous behavior was observed. In the centrifuged microspheres, the hyaluronic acid degree of methacrylation was inversely proportional to the gel elasticity, and a mechanism based on failure due to microsphere brittleness is proposed to explain this behavior. These results suggest that processing methacrylated hyaluronic acid can lead to a diversity of solution properties, providing methods for delivering this biologically active polymer in a broad range of applications.

Melamine formaldehyde (MF) resin was synthesized by the reaction between melamine and formaldehyde under alkaline condition in tetrohydrofuran medium with 1:3 melamine to formaldehyde molar ratio. The synthesized resins were characterized by differential scanning calorimetry (DSC), Fourier transform infrared spectroscopy (FTIR) and thermal gravimetric analysis (TGA). Curing and reaction mechanism was studied by thermal and spectroscopic analysis. Two exothermic peaks were observed in the DSC analysis indicating a two-step crosslinking reaction process was correlated to TGA analysis. FTIR studies at different temperatures explained the two-stage curing mechanism which is concurring with the DSC data. At a temperature range of 140–160 1C, reversible demethylolation is dominating to the crosslinking reaction. At temperature 4160 1C, the crosslinking reaction dominates. On the basis of DSC and FTIR data, a possible crosslinking reaction route was derived and explained. The first stage of curing is the conversion of methylol groups to primary amine and the second stage is the crosslinking of methylol groups to the final product, methylene bridges. The thermal stability of the methylol groups, methylene bridges and the triazine ring, as well as the evaporation of effluents at different stages of curing, are also discussed based on combined TGA and DSC results. INTRODUCTION Melamine (1, 3, 5-triamino-2, 4, 6-triazine) formaldehyde (MF) is one of the hardest and stiffest thermosetting polymers, which provides good properties and performance. It is an amino resin and has various material advantages, such as transparency, better hardness, thermal stability, excellent boil resistance, scratch resistance, abrasion resistance, flame retardant, moisture resistance and surface smoothness , which lead MF to large industrial applications. 1 These polymers were originally used as wood adhesives and have now found applications in flooring and decorative laminates, molding compounds, coatings and adhesives. 2,3,4 MF resins are incorporated in wide variety of products that are valued for its toughness and relative ease of manufacture. 5 The curing behavior and the degree of crosslinking of MF resin determine the tailored product properties such as mechanical, thermal and electrical properties. 6 Cured MF polymers are sufficiently hard and exhibit high resistance against temperature, chemicals and hydrolysis, making them suitable for interior working surfaces. 7 If the resin is not cured properly, MF will lack mechanical strength and surface finishes. For example, MF impregnated papers will lack hardness, durability, brilliance and resistance to hydrolysis and chemical agents. 8 The condensation reaction and the resulting structure of MF resins vary significantly with the reaction conditions such as molar ratios of the reactants, pH and reaction temperature

Introduction: Prompt and efficient management of epistaxis is a required skill set for otolaryngology and emergency physicians. Existing simulators do not accurately model the anatomical features required for training of proper epistaxis management. The goals of this work were to: 1) Create a realistic adult epistaxis model with high anatomic fidelity; and 2) Evaluate preliminary validity evidence of this novel simulator for the use of training and assessing learner epistaxis management skills. Methods: Modifying a de-identified patient CT, a 3D model of relevant features and anatomy was printed and assembled. 'Blood' was selectively run through the catheters to simulate bleeding from 3 primary sources. In a two-phase process, two groups of expert-level Otolaryngology faculty independently evaluated the simulator using a web-based survey. In Phase 1, 6 faculty evaluated the simulator and ratings guided improvements. In Phase 2, 17 faculty evaluated the revised simulator across two primary domainsY the degree of realism presented by the simulator (Realism), and ability to perform five sequential relevant tasks (Ability). Realism was measured by 20 items across 5 subdomains: visual attributes, materials' response, realism of experience, value/ relevance, and global value using 4 point rating scales. Ability was scored using 5-point rating scales, ranging from 1 (too difficult to perform) to 5 (very easy to perform). Validity evidence was evaluated using a many-Facet Rasch model. Results: Participating faculty self-reported treating between 3 and 15 epistaxis cases monthly (M=8.8). Following improvements, Phase 2 observed averages (OA) across the four Realism domains ranged from 3.2 (Realism of experience) to 3.5 (Value). Lowest ratings were associated with Visualization, posterior source of bleeding, and Tactile properties of insertion of nasal speculum (both OA= 3.2). Although greatly improved from Phase 1 [Mphase1= 2.5 (SD=0.8); Mphase2=3.1 (SD=0.9), p=0.05], relatively low observed averages of Tactile property during insertion of nasal speculum was consistent with comments such as ''I needs more nostril/nasal sill laxity.'' Global OA= 2.7/4.0, indicating the overall, respondents believed the new simulator could be used for teaching epistaxis management, but could be improved slightly. Following simulator improvements, participants' Ability improved across four of the five aspects (pG 0.05), with all OA= 4.0, aligning with the ideal ''Somewhat easy to perform.'' Conclusion: Using 3D printing technology, we successfully created a novel simulator for training of proper epistaxis management. Early evidence suggests the model is considered relevant to trainees' educational needs, and valuable as a testing and training tool. 3D printing technology allows for minor modifications to be addressed virtually, and easily alter the print based on expert feedback. With minor modifications, the novel epistaxis simulator can be implemented in a simulation-based curriculum.