Development of stable and active PVA‐PSSA/SA‐PVA catalytic composite membrane for esterification enhancement

An active and stable catalytic composite membrane (CCM), poly(vinyl alcohol)–poly(styrene sulfonic acid)/sodium alginate–poly(vinyl alcohol) (PVA‐PSSA/SA‐PVA), was prepared to enhance the esterification of ethanol and propionic acid. The morphologies and crystal structures of the CCMs were investigated by Fourier transform infrared spectroscopy, scanning electron microscopy, and X‐ray diffraction. The effects of catalytic layer thickness, mass ratio of PVA to PSSA, concentration of catalytic layer solution, ratio of reaction volume to membrane area, and molar ratio of propionic acid to ethanol were discussed. The pervaporation results showed that the flux of CCM increased from 118 to 320 g m^?2 h^?1 compared with the SA‐PVA membrane because of the close affinity and low resistance of PSSA to water. After crosslinking with 3‐aminopropylmethyldiethoxysilane, the CCMs had good catalytic activities. The acid conversion reached 92.8% at 75 °C in 12 h, and the stabilization of the CCM was greatly improved. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46514.     

Nitrofurazone‐loaded PVA–PEG semi‐IPN for application as hydrogel dressing for normal and burn wounds

Hydrogels have been used in a wide variety of biomedical devises, particularly in the field of drug delivery, tissue engineering, and wound healing. In this study, a polyvinyl alcohol (PVA)–polyethylene glycol (PEG) semi‐interpenetrating hydrogel network (IPN)‐based wound dressing system containing nitrofurazone (NFZ) was synthesized by chemical crosslinking technique. The introduction of PEG to PVA matrix led to reduction in the water vapor transmission rate, which in‐turn resulted in improved healing activity. Drug‐loaded IPNs were prepared by mixing aqueous solution of NFZ with the optimized PVA–PEG formulation subsequent to the crosslinking step. The in vitro diffusion studies of NFZ indicated a relatively slow release of drug resulting from its microencapsulation in the polymeric matrix. Subsequently, in vivo wound healing efficacy toward acute and burn wound healing in experimental rats was investigated. Semi‐IPN hydrogel loaded with NFZ dressing improved the overall healing rate in both acute and burn wounds, as evidenced by significant increase in total protein, hydroxyproline and hexosamine contents. Histological examinations also correlated well with the biochemical findings. A faster wound contraction was also observed in hydrogel treated acute and burn wounds. The results indicated that PVA–PEG semi‐IPN hydrogel based dressing systems containing NFZ could be used as an effective wound dressing material. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Laboratory scale study on rheological behavior,morphological and structural properties of crosslinked polyacrylamide composite hydrogels embedded with date seed powder

Incorporation of biofillers in polymeric hydrogels has continued to receive great attention in recent times because of their excellent properties. In this study, polyacrylamide (PAM) and polyethyleneimine (PEI) were used to develop novel composite hydrogels filled with date seed powder (DSP) via chemical crosslinking technique. Pristine PAM/PEI hydrogel and PAM/PEI‐DSP hydrogels at various DSP loadings were fabricated and subjected to gelation at 40°C for 24 h. The impact of various DSP loadings on the hydrogel samples developed was investigated using hybrid rheometer, SEM, XRD, and FTIR instruments, respectively. Rheological measurements confirmed the viscoelastic responses of the neat PAM/PEI hydrogel and the PAM/PEI‐DSP hydrogels reinforced with various DSP contents (0.8, 2.4, and 4 wt %). The dynamic strain, dynamic frequency and time sweep tests demonstrated that PAM/PEI‐DSP hydrogels were slightly more elastic than the virgin PAM/PEI hydrogel. The SEM characterization revealed the surface micrographs of the neat PAM/PEI hydrogel and the PAM/PEI‐DSP hydrogels at different DSP loadings to be smooth, homogeneous, and dense. Besides, the SEM micrographs supported the incorporation of DSP in the PAM/PEI‐DSP hydrogel samples. XRD analysis showed that the structures of neat PAM/PEI hydrogel and PAM/PEI‐DSP hydrogels filled with various DSP contents were predominantly amorphous while FTIR results confirmed the functional groups and evidence of crosslinking in the neat PAM/PEI hydrogel and the PAM/PEI‐DSP hydrogels embedded with different DSP contents. It is believed that these new hydrogels have huge development potentials and promising future in wastewater treatment and removal of heavy metal ions in aqueous solutions. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42110.     

Influences of different gravity environments on the curing process and cured products of carbon‐nanotube‐reinforced epoxy composites

The influences of different gravity environments on the curing process and the cured products of carbon‐nanotube‐reinforced epoxy composites were investigated in this study. Different gravity environments were simulated with a superconducting magnet on the basis of which resin matrix composites with different amino‐functionalized multiwalled carbon nanotube (NH₂‐MWCNT) concentrations of 0.1, 0.3, 0.5, and 1 wt % were tested. Fourier transform infrared spectroscopy, differential scanning calorimetry, dynamic mechanical analysis, thermomechanical analysis (TMA), thermogravimetric analysis, scanning electron microscopy, transmission electron microscopy, and three‐point bending tests were used to analyze the characteristics of different curing processes and cured products. From the results, we observed that the curing rate of the epoxy composites was influenced by different gravity values, and there was anisotropy in the NH₂‐MWCNT‐reinforced epoxy composites cured in the simulated microgravity environment. More effects of gravity on the curing process and cured products could be obtained through detailed experiments and discussion; this is important and fundamental for improving and enhancing the properties of composite materials used in different gravity environments. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41413.     

Ultraviolet‐crosslinked hydrogel sustained‐release hydrophobic antibiotics with long‐term antibacterial activity and limited cytotoxicity

To prolong erythromycin (EM) release and prevent the side effects of EM, a Pluronic F‐127 diacrylate macromer (PF127) was synthesized and then self‐assembled into micelles with their hydrophobic cores loaded with EM. The EM‐loaded micelles were mixed with a photoinitiator to form the EM/PF127 hydrogels rapidly under a low‐intensity UV light. Afterward, the hydrogel properties, antibacterial performance, and cytotoxicity of this novel hybrid hydrogel were investigated. The results show that the EM/PF127 hydrogel had a rapid gelation time. The sustained release of EM reduced its side effects. With controlled antibacterial activity, the use of EM would be safer and more efficient. What is more, the EM/PF127 hydrogel showed a slight cytotoxicity, and this suggests great potential application as antibacterial hydrogels in the prevention of postoperative infection. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40438.     

Study on a carboxyl‐activated carrier and its properties for papain immobilization

BACKGROUND: Most enzymes, including protease, play a key role in biotechnology, but their use is quite limited due to poor recovery, limited reusability and instability. Immobilized enzymes offer advantages over free enzymes. This paper reports a simple method for the preparation of immobilized papain, an endolytic cysteine protease (EC: 3.4.22.2), on carboxyl‐activated silica nanoparticles. RESULTS: The carboxyl‐activated carriers produced reactive carboxyl groups which then react with the free amino groups of enzyme to give peptide bonds (? CO? NH? ). The results showed that the thermal and pH stabilities of the immobilized papain were higher than those of free enzyme. And the apparent K_m value of the immobilized papain was 1.26 times higher than that of free enzyme. Moreover, the immobilized papain retained more than 45% of the original activity after ten reuses continuously. CONCLUSION: The results indicated that papain was successfully immobilized on the surface of the activated carriers. The immobilized papain had not only higher activity recovery, but also better stability, reusability and environmental adaptability. Copyright © 2012 Society of Chemical Industry     

β‐cyclodextrin‐conjugated hyaluronan hydrogel as a potential drug sustained delivery carrier for wound healing

In order to develop a potential drug sustained delivery carrier suitable for wound healing, a series of β‐cyclodextrin conjugated hyaluronan hydrogels (β‐CD‐HA) with adjustable crosslink densities were synthesized and characterized, meanwhile the delivery kinetics and mechanism of diclofenac as a model anti‐inflammatory drug from these hydrogels were investigated. By controlling the feeding molar ratio of β‐CD/HA, a β‐CD substitution degree of 4.65% was obtained by ¹H‐NMR analysis. The incorporation of β‐CD modification had little effect on the internal porous structure, water swelling ratio, and rheological property of HA hydrogel, which however were influenced by the crosslink density. Although the crosslink density had an influence on the drug loading and release profile by altering the water swelling property, the interaction between β‐CD and drug was the primary factor for the high loading capacity and long‐term sustained delivery of diclofenac. The semiempirical equation fit showed that the release of diclofenac from HA‐based hydrogels followed a pseudo‐Fickian diffusion mechanism. By the aid of β‐CD and controlled crosslink density, a β‐CD‐HA hydrogel with a diclofenac sustained delivery period of over 28 days and desirable physicochemical properties was achieved, which will be a promising drug sustained delivery carrier for wound healing. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43072.     

Synthesis and swelling properties of a pH‐ and temperature‐dual responsive hydrogel by inverse microemulsion polymerization

A novel pH‐ and temperature‐dual responsive hydrogel was synthesized by inverse microemulsion polymerization, using itonic acid (IA) as pH‐responsive monomer, N‐isopropylacrylamide (NPAM) as thermo‐responsive monomer and acrylamide (AM) as the nonionic hydrophilic monomer. Factors affecting water and salt absorption, as well as swellability of the dual responsive hydrogels, such as IA/NPAM mass ratio and crosslinker amount, were investigated. pH‐ and temperature‐sensitivity and dynamic viscoelasticity behaviors of the dual responsive hydrogels were also studied. The dual responsive responsive hydrogels showed suitable water and salt absorbency, remarkable pH‐, and temperature‐sensitivity, adjustable swellability and enhanced viscoelastic behaviors under high stress. Water absorbency and pH‐sensitivity increased while salt absorbency and temperature‐ sensitivity decreased with increasing IA/NIPAM mass ratio. Both water absorbency and salt absorbency increased first with crosslinker amount increased to 0.2 wt %, and then decreased with increasing crosslinker amount. Temperature‐induced shrinkage range of the dual responsive hydrogels was higher and broader than that of the conventional poly(N‐isopropylacrylamide) hydrogel. TEM indicated that the as‐synthesized hydrogel particles were regular and spherical‐like in shape and had the mean particle size of 49nm in the range of 30–78 nm. FTIR indicated the structure of the dual responsive hydrogels. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42139.     

Gellan gum–O,O′‐bis(2‐aminopropyl)‐polyethylene glycol hydrogel for controlled fertilizer release

A gellan gum–Jeffamine superabsorbent hydrogel was obtained with different crosslink densities using different amounts of (1‐ethyl‐3‐(3‐dimethylaminopropyl)carbodiimide hydrochloride) and N‐hydroxysuccinimide. Infrared spectroscopy and thermal analysis confirm the crosslinking. A morphology analysis indicates denser structures for samples with higher crosslinking points. The swelling degree in high‐acyl gellan gum hydrogels was equivalent to 145 times their dry weight, and 77 times when low‐acyl gellan gum was used. Hydrogels also showed a 450 min water retention, as opposed to 280 min for pure water, evidencing good humidity control, suitable for use in arid climates. They also demonstrated a maximum release of commercial fertilizer of about 400 mg per gram for KH₂PO₄ and about 300 mg per gram for NPK 20‐5‐20. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 45636.     

Design of robust and photoluminescence‐responsive materials based on poly(methacrylic acid‐co‐m‐phenylenediamine) with graphene oxide composite hydrogels and its adsorption

A promising strategy to design crosslinked photoluminescent hydrogel (PL hydrogel) is to synthesize the covalently bonded polymer chains by thermal polymerization. A proper ratio of methacrylic acid and m‐phenylenediamine was used to prepare the PL hydrogel, and doping with graphene oxide and carboxymethyl chitosan improves the structure of the gel. The green and efficient hydrothermal synthesis realized a high polymerization and a short reaction time. Meanwhile, a series of properties were investigated for several combinations of hydrogels. Ultraviolet spectra, fluorescence spectra, and particle size distributions were used to characterize the PL composites. Scanning electron microscopy, Fourier transform infrared spectroscopy, X‐ray photoelectron spectroscopy, thermogravimetric analysis, rheological studies, and stress–strain tests were conducted to characterize the morphology, structure, and performance of the compound hydrogel. The adsorption properties of the PL hydrogel were characterized in adsorption tests. The results indicated that the PL hydrogel exhibited a favorable luminescence property, a certain degree of mechanical strength, and good adsorption performance. The prepared PL hydrogel has potential applications in adsorption and visual detection. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46354.     

Piezo and dielectric properties of PHB–PZT composite

Flexible piezoelectric composite films made of poly(3‐hydroxybutyrate) (PHB) in powder form and lead zirconate titanate (PZT) ceramic powder were obtained by mixing both powders and pressing at 180°C. The effect of PZT on PHB crystallization was investigated using differential scanning calorimetry (DSC). The relative dielectric constant and dielectric loss factor were analyzed by dielectric spectroscopy and the α‐relaxation of amorphous phase of PHB was observed. After suitable polarization, the composite film displayed piezoelectric activity indicating the possibility of using that material as a sensor. POLYM. COMPOS., 2009. © 2008 Society of Plastics Engineers     

Improvement in mechanical and hygroscopic properties of modified SA fiber crosslinking with PEGDE

Modified sodium alginate (mSA) fiber is prepared through the wet spinning process using poly(ethylene glycol) diglycidyl ether (PEGDE, the molecular weight of PEGDE is 400) as the crosslinking agent to improve the mechanical and hygroscopic properties. Flowing property of the spinning solution and properties of the mSA fiber are characterized by DV-C digital viscometer, single fiber electronic tensile strength tester and other instruments. Results show that viscosity of the spinning solution dropped firstly, then increased and decreased lastly with increasing PEGDE content in mSA fiber. The optimal value of the tensile strength of mSA fiber is 2.47 cN/dtex increasing by 64.67% compared to pure SA fiber. Both the crosslinking degree and crystallinity of mSA fiber rise first and then descended with the increase of PEGDE content. The hydroscopicity of mSA fiber increase from 30.5% to 70.9% at 20 wt % PEGDE in mSA fiber. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47155.     

钢塑复合管专用交联HDPE的研制

研制了钢塑复合管专用交联高密度聚乙烯(HDPE),并研究了其性能。结果表明．交联后的HDPE具有更加优异的力学性能;随着交联剂(VS—1)用量的增加,交联HDPE的拉伸强度、冲击强度、凝胶率增加,但其断裂伸长率和流动性下降,当VS—l质量分数为1．8％时,交联HDPE的性能最佳：拉伸强度为40．8MPa,冲击强度为117J／m^2,凝胶率为73．8％,断裂伸长率为280％,熔体流动指数为0．3g／10min;将5000S与2480共混,并添加质量分数不低于1．0％的流变剂YL—1,其加工流动性最佳;用二月桂酸二丁基锡作催化剂使HDPE的交联反应在5h后就完成了90％以上．比不加催化剂提前15h。     

Viscoelastic properties of borax loaded CMC‐g‐cl‐poly(AAm) hydrogel composites and their boron nutrient release behavior

Borax (Na₂B₄O₇, 10.5% Boron) loaded CMC‐g‐cl‐poly(AAm) hydrogel composites were prepared by in situ grafting of acrylamide on to sodium carboxymethyl cellulose in the presence of borax by free radical polymerization technique to develop slow boron (B) delivery device. The composition, morphology, and mechanical properties of synthesized composites were studied by X‐ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy, texture analyser, and dynamic shear rheometer. Characterization revealed formation of borate ion ( ) from borax during polymerization reaction leading to extensive crosslinking of cellulosic chains and generation of mechanically strong composite hydrogels. Dynamic release of from the synthesized composites hydrogels followed Fickian diffusion mechanism and composites with high mechanical strength resulted in slow release of B. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43969.     

Water‐soluble polymers and gels from the polycondensation between cyclodextrins and poly(carboxylic acid)s: A study of the preparation parameters

Native cyclodextrins (CDx) and some of their derivatives were reacted with poly(carboxylic acid)s (PCAs) [citric acid (CTR), 1,2,3,4‐butanetetracarboxylic acid (BTCA), and poly(acrylic acid) (PAA)]. These reactions were carried out in the dry state at a temperature greater than 140°C in air or in vacuo. They resulted in water‐soluble and insoluble polymers formed by polyesterification between CDx and PCA. In this study, the parameters of the reaction were studied, and their influence on the water solubility or swellability of the obtained polymers was investigated. High reaction temperatures, high PCA/CDx molar ratios, and long reaction times preferably yielded insoluble gels, whereas softer conditions resulted in very soluble polymers. The gels could swell up to 10 times their initial volume in water, and the water‐soluble fraction had a solubility of 1 g/mL. A reaction mechanism was proposed that required the use of PCA carrying at least three neighboring carboxylic groups (CTR, BTCA, and PAA), and it was confirmed experimentally by the unsuccessful use of some dicarboxylic acids. A preliminary characterization by Fourier transform infrared spectroscopy and size exclusion chromatography was also conducted. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 433–442, 2005     

Study on strength and gelation time of polyacrylamide/polyethyleneimine composite gels reinforced with coal fly ash for water shut‐off treatment

This study investigates the influence of coal fly ash (CFA) as a reinforcing material on the strength and the gelation of polyacrylamide (PAM)/polyethyleneimine (PEI) composite gels. Pure PAM/PEI gel and PAM/PEI gels containing CFA up to 2 wt % were synthesized via the cross‐linking reaction between PAM and PEI solutions at room temperature (25°C) in distilled water dispersed with CFA. The strength of each composite gel was measured at temperature of 80°C, while the gelation was determined from 80°C to 95°C. Rheological measurements indicated that the strength of PAM/PEI composite gels filled with CFA contents was significantly rigid and stronger than that of pure PAM/PEI gel as a result of the enhanced interfacial interaction of well‐dispersed CFA contents in PAM/PEI gel matrix. The gelation times of PAM/PEI gels containing CFA up to 2 wt % deviated from the gelation time of pure PAM/PEI gel. It was further observed that an increase in temperature resulted in a decrease in gelation time of PAM/PEI gel containing 2 wt % CFA. The scanning electron microscopy revealed the surface micrographs of PAM/PEI gels filled with CFA to be very dense without any noticeable micropores. The micropores were absent as scanning was performed on the dried composite gels. It also establishes the strong interaction between CFA and PAM/PEI gel matrix. Experimental findings showed that PAM/PEI composite gels reinforced with CFA are potential candidates for total water shut‐off treatment in oilfields. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41392.     

Hydrophobic and nanoporous chitosan–silica composite aerogels for oil absorption

Hydrophobic and nanoporous chitosan–silica composite aerogels with low density, high porosity, and superior oil absorbency were successfully prepared by a typical sol–gel method and a two‐step hydrophobic treatment. The morphologies, porosity characteristics, mechanical properties, thermal stability, hydrophobicity, and oil absorbencies of the composite aerogels were systematically investigated. The nitrogen physisorption analysis showed that composite aerogels had large specific surface areas and uniform nanoporous structures. In addition, the composite aerogels could support 7000 times its own weight; this indicated the role of the supporting skeleton played by chitosan. The hydrophobicity and lipophilicity was demonstrated with a water contact angle of 137° and an oil contact angle of 0°. Importantly, the composite aerogel with 20 wt % chitosan had a relatively high oil absorbency of 30 g/g and could be reused up to 10 times. Therefore, the chitosan–silica composite aerogels in this study had a broad prospect to be used as efficient and recyclable oil absorbents. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41770.     

The effect of an anhydride curing agent,an accelerant,and non‐ionic surfactants on the electrical resistivity of graphene/epoxy composites

This study investigated different contents of an anhydride curing agent, an accelerant, and non‐ionic surfactants on the electrical resistivity of cured graphene/epoxy composites. The anhydride curing agent was hexahydrophthalic anhydride (HHPA), the accelerant was 2‐ethyl‐4‐methyl‐1H‐imidazole‐1‐propanenitrile (EMIP), and the non‐ionic surfactants were Triton X surfactants with different numbers of polyethylene oxide (PEO) groups (m) that influence the electrical resistivity of cured graphene/epoxy composites. During the curing process, differential scanning calorimetry (DSC) was used to determine the effects of the extent of the crosslinking for different contents of the curing agent and how different enthalpy (ΔH) on the electrical resistivity of the cured graphene/epoxy composites was then generated. The cured graphene/epoxy composite—which consisted of a 1 : 0.85 weight ratio of epoxy resin and anhydride, a 0.5 wt % accelerant, and a 13 wt % graphene powder—had a low electrical resistivity of 11.68 Ω·cm and a thermal conductivity of 1.7 W/m·K. In addition, the cured composites contained a 1.0 wt % polyethylene glycol p‐isooctylphenyl ether (X‐100) surfactant, which effectively decreased their electrical resistivity. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41975     

Dynamic rheological properties for HDPE/CB composite melts

A study on the dynamic viscoelastic properties of carbon black (CB)‐filled high‐density polyethylene (HDPE) in the molten state was carried out. When the temperature was above 180°C in an air atmosphere, the storage modulus G′, loss modulus G″, and loss tangent δ showed particular characteristics. In the low‐frequency region, the modulus increased with increase of the testing time while the tan δ obviously decreased. Also, the higher the temperature, the more notable was the change. We can detect these changes from the deviation of G′ (G″) against ω plots from the linearity and the appearance of a characteristic plateau phenomenon. The width and height of the modulus plateau increased with increase of the temperature. When temperature was below 180°C, the testing time and the temperature had no effect on the viscoelastic parameters of HDPE. However, if we used 99% nitrogen gas as the atmosphere, substituting for air, the viscoelastic parameters revealed an undiscernible change, different from that in an air atmosphere. No changes were found under the protection of the antioxidant B215. This phenomenon indicated that HDPE can be oxidized at a temperature higher than 180°C. Nitrogen gas and an antioxidant agent can prevent HDPE from crosslinking. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 2160–2167, 2003     

Application of Plackett–Burman screening design to the modeling of grafted alginate–carrageenan beads for the immobilization of penicillin G acylase

Grafted alginate–carrageenan beads were used to immobilize the industrial enzyme penicillin G acylase (PGA). Sixteen factors were screened with the Plackett–Burman design (PBD) to test their significance on the gel beads formation and enzyme immobilization process. The results of PBD showed a wide variation of 30‐fold in the amount of immobilized penicillin G acylase (iPGA) from 11.9 to 354.16 U/g of beads; this reflected the importance of the optimizing process. Among the 16 tested factors, only 3 were proven to be significant. These factors were the enzyme buffer pH (N), enzyme soaking time (Q) with the gel beads, and enzyme concentration (P). The Pareto chart revealed that both Q and P exerted significant positive effects on the amount of iPGA, whereas N had a negative effect. We recommend further study to optimize only these three significant, distinctive enzyme factors. The PGA covalent attachment to the gel beads were proven by Fourier transform infrared spectroscopy, elemental analysis, and NaCl and reusability tests. The best gel bead formula succeeded in the immobilization of 354.16 U/g of beads and proved to be reusable 14 times, retaining 84% of the initial enzyme activity. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40295.