Pyrogallol–formaldehyde thermosetting adhesives

A new thermosetting wood adhesive system from pyrogallol has been developed. Pyrogallol can be easily obtained from tara pods (Caesalpinia spinosa) a native leguminosae of low cost widely distributed in Peru. In this work, polymerization of formaldehyde with pyrogallol was carried out at different pH values and optimal conditions were determined to establish the adhesive formulation. The reactivity of this resin was characterized by differential scanning calorimetry (DSC) and the results were compared with those obtained with resins made with tara tannin, gallic acid, and phenol. The results show that tara tannin and gallic acid are less reactive due to the presence of deactivating groups (i.e., carboxylates) in the phenolic moieties while their polymerization is limited to that of a bidimensional network upon curing. In contrast, pyrogallol–formaldehyde kinetic parameters (Ea and ΔH) were determined and they are comparable with those of phenol-formaldehyde adhesives. In addition, mechanical property values (MOR, MOE, and IB) of particleboards prepared with pyrogallol–formaldehyde compare favorably to those of Canadian standard requirements (CSA). Main assets of the new thermosetting adhesive is lower pressing times and temperatures than those currently used in the industry. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 65:399–408, 1997     

Effect of in situ apatite on performance of collagen fiber film for food packaging applications

This study attempted to prepare apatite in situ in acid‐swollen cowhide collagen film by an ammonia gas fumigating method and assess its reinforcement effect on a collagen fiber film for food packaging applications. The X‐ray diffraction and Fourier transform infrared spectroscopy results confirmed the successful synthesis of apatite in collagen fiber films. SEM images showed that tiny apatite particles appeared as a coating on the film surface and also made the film's inner structure more compact and less porous than pure collagen fiber film. Apatite significantly (p < 0.05) increased the tensile strength and improved the water vapor barrier and water insolubility properties of collagen fiber film. Moreover, the thermogravimetric and differential scanning calorimetry results confirmed that the thermal stability of collagen was improved with the increasing apatite. The in situ–synthesized apatite provided a practical reinforcement approach to improving the collagen fiber film's performance and benefited its application as a food packaging material. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 44154.     

The Wood Preservative Potentials of Valonia,Chestnut, Tara and Sulphited Oak Tannins

This study investigated antifungal properties of four different tannins as potential environmentally friendly wood preservatives. Scots pine wood samples were impregnated with 3, 5, 10, and 15% valonia, chestnut, tara, and sulphited oak tannins, and then were exposed to brown rot fungi Coniophora puteana and Postia placenta, and white rot fungi Trametes versicolor and Pleurotus ostreatus attack to determine the best tannin type and the optimum concentration level for sufficient decay resistance. Leaching test was conducted in order to evaluate any loss in effectiveness in decay resistance due to possibility of tannin leaching. Tannins were found efficacious in suppressing brown rot fungi attacks when no leaching prior the decay test was used, however, they seemed to be ineffective against white rot fungi attacks. The lowest weight losses were obtained with valonia and chestnut tannins both for brown and white rot fungi probable related with their high ellagic tannin content.     

紫外法和皮粉法测定塔拉单宁含量的对比研究

分别采用紫外法和皮粉法对5种不同含量的塔拉单宁进行对比研究,并利用SPSS软件对单宁含量测定结果进行显著性检验,结果表明：高纯度塔拉单宁(93%)分别用紫外法和皮粉法测定单宁含量时实验结果并未显著差异(P>0.05),而4种纯度为60%左右塔拉单宁的实验结果均具有显著性差异(P<0.05),皮粉法测得的单宁含量均比用紫外法测得的结果高,差值约为1.5%～2.0%,并由此计算出紫外法测定塔拉单宁含量计算公式中的矫正常数p为1.03。紫外-可见吸收光谱与HPLC分析结果表明：塔拉单宁与五倍子单宁的最大吸收峰均为276 nm,同质量浓度下塔拉单宁的吸收峰强度高于五倍子单宁,塔拉单宁成分出峰时间主要在20～40 min,五倍子单宁主要在30～45 min。     

膜分离法制备塔拉单宁的研究

采用聚砜中空纤维膜处理塔拉单宁水提取液,研究了聚砜膜的截留分子质量,跨膜压差、膜面流速以及溶液温度对膜性能和产品质量的影响。结果表明,以截留分子量为10000,跨膜压差0.2 MPa,膜面流速2.0 m/s,40～45℃下对塔拉单宁水提液进行膜分离,可以得到浊度0.5 NTU以下,纯度85%以上的高品质塔拉单宁。     

Polymer structure of commercial hydrolyzable tannins by matrix‐assisted laser desorption/ionization‐time‐of‐flight mass spectrometry

The structures of six commercial hydrolyzable tannins, chestnut, oak, tara, sumach, chinese gall, and turkey gall tannins have been examined by matrix‐assisted laser desorption/ionization‐time‐of‐flight (MALDI‐TOF) mass spectrometry. Their oligomeric structures and structure distributions have been defined. Degradation products of rather different structure than what previously reported were present. Different galloyl glucose monomers were observed for chestnut and oak tannin extracts and in chinese gall gallotannin extract. Combination of positive‐ and negative‐mode MALDI‐TOF showed that most galloyl residues of the galloyl glucose chains were stripped from a skeletal glucose chain. Oligomers, in some cases up to 16 or 17 glucose units long, almost totally stripped of galloyl residues were observed. This indicated that a wide distribution up to very long gaIloylglucose chains exist in most commercial hydrolyzable tannin extracts. This indicated that these commercial tannin extracts are mainly composed of long galloyl glucose chains of mixed di‐, tri‐, and pentagalloyl glucose repeating units being present in the same chain. The presence of long glucose chains where most of the galloyl residues have been stripped indicates that their linkage may be sugar residue to sugar residue. Commercial tara and turkey gall tannins have been shown to be mainly polygallic oligomers of up to eight gallic acid residues linked to each other in a chain. Commercial sumach extract revealed itself a more complex mixture of glucose oligomers up to 13 repeating units. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Antibacterial polycaprolactone electrospun fiber mats prepared by soluble eggshell membrane protein–assisted adsorption of silver nanoparticles

Antibacterial polycaprolactone (PCL) electrospun fiber mats were prepared by coelectrospinning PCL with soluble eggshell membrane protein (SEP) in 1,1,1,3,3,3‐hexafluoro‐2‐propanol (HFIP), followed by adsorption of silver nanoparticles (Ag NPs) through hydrogen‐bonding interaction between the amide groups of SEP and the carboxylic acid groups capped on the surfaces of Ag NPs. The PCL/SEP fiber mat was characterized by X‐ray photoelectron spectroscopy, indicating the presence of some SEP on the fiber surface. The adsorption of Ag NPs was confirmed by transmission electron microscopy and quantitatively characterized by thermogravimetric analysis. The pH value of the silver sol used for adsorption is very important in view of the amount and dispersion state of Ag NPs adsorbed on the fibers. The Ag NP–decorated PCL/SEP fiber mats prepared at pH 3–5 exhibit strong antibacterial activity against both gram‐negative Escherichia coli and gram‐positive Bacillus subtilis. Antibacterial PCL fiber mats were also obtained similarly with the assistance of collagen (another protein) instead of SEP, showing that protein‐assisted adsorption of Ag NPs is a versatile method to prepare antibacterial electrospun fiber mats. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43850.     

Polyacrylonitrile solution homogeneity study by dynamic shear rheology and the effect on the carbon fiber tensile strength

Poly(acrylonitrile‐co‐methacrylic acid) (PAN‐co‐MAA)/N,N‐dimethylformamide (DMF) solutions were prepared and dynamic shear rheology of these solutions were investigated. With increasing stirring time up to 72 h at 70°C, the polymer solution became less elastic (more liquid‐like) with a ～60% reduction in the zero‐shear viscosity. Relaxation spectra of the PAN‐co‐MAA/DMF solutions yield a decrease in relaxation time (disentanglement time, τ_d), corresponding to an about 8% decrease in viscosity average molecular weight. The log‐log plot of G′ (storage modulus) versus G″ (loss modulus) exhibited an increase in slope as a function of stirring time, suggesting that the molecular level solution homogeneity increased. In order to study the effect of solution homogeneity on the resulting carbon fiber tensile strength, multiple PAN‐co‐MAA/DMF solutions were prepared, and the precursor fibers were processed using gel‐spinning, followed by continuous stabilization and carbonization. The rheological properties of each solution were also measured and correlated with the tensile strength values of the carbon fibers. It was observed that with increasing the slope of the G′ versus G″ log‐log plot from 1.471 to 1.552, and reducing interfilament fiber friction during precursor fiber drawing through the addition of a fiber washing step prior to fiber drawing, the carbon fiber strength was improved (from 3.7 to 5.8 GPa). This suggests that along with precursor fiber manufacturing and carbonization, the solution homogeneity is also very important to obtain high strength carbon fiber. POLYM. ENG. SCI., 56:361–370, 2016. © 2016 Society of Plastics Engineers     

Adsorption of bismuth(III) by bayberry tannin immobilized on collagen fiber

The adsorption behavior of collagen fiber‐immobilized bayberry tannin towards Bi(III) at acidic pH values was investigated. The adsorption capacity of the adsorbent towards Bi(III) was 0.348 mmol g^?1 at 303 K, and increased with the rise in temperature. The adsorption isotherms of Bi(III) were in the shape of so‐called type II isotherms and could be described by an empirical equation, ln q_e = k + (1/n)C_e, which implies that chemical adsorption is predominant at lower concentrations of Bi(III) and that physical adsorption is involved at higher concentrations. The adsorption kinetics of Bi(III) on the immobilized bayberry tannin could be well described by the pseudo‐second‐order rate model, and the adsorption capacities calculated by the model were almost the same as those determined by actual measurements. The adsorbent could be regenerated by using 0.02 mol dm^?3 ethylenediaminetetraacetic acid (EDTA) solution after adsorption of Bi(III). The adsorption selectivity of the immobilized bayberry tannin towards Bi(III) in a Cu(II)–Bi(III) binary solution in acidic medium was remarkable. Therefore, it is strongly suggested that the immobilized bayberry tannin could be applied to the removal of Bi(III) from crude Cu(II) samples under proper conditions. Copyright © 2006 Society of Chemical Industry     

Bleached extruder chemi‐mechanical pulp fiber‐PLA composites: Comparison of mechanical,thermal, and rheological properties with those of wood flour‐PLA bio‐composites

An environmentally friendly bleached extruder chemi‐mechanical pulp fiber or wood flour was melt compounded with poly(lactic acid) (PLA) into a biocomposite and hot compression molded. The mechanical, thermal, and rheological properties were determined. The chemical composition, scanning electron microscopy, and Fourier transform infrared spectroscopy results showed that the hemicellulose in the pulp fiber raw material was almost completely removed after the pulp treatment. The mechanical tests indicated that the pulp fiber increased the tensile and flexural moduli and decreased the tensile, flexural, and impact strengths of the biocomposites. However, pulp fiber strongly reinforced the PLA matrix because the mechanical properties of pulp fiber‐PLA composites (especially the tensile and flexural strengths) were better than those of wood flour‐PLA composites. Differential scanning calorimetry analysis confirmed that both pulp fiber and wood flour accelerated the cold crystallization rate and increased the degree of crystallinity of PLA, and that this effect was greater with 40% pulp fiber. The addition of pulp fiber and wood flour modified the rheological behavior because the composite viscosity increased in the presence of fibers and decreased as the test frequency increased. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 44241.     

Combination of lignin polyol–tannin adhesives and polyethylenimine for the preparation of green water‐resistant adhesives

In this study, a green adhesive from renewable lignin and tannin was developed with polyethylenimine (PEI) with a method to improve the water resistance of the lignin/tannin adhesive. Lignin polyols were prepared through the liquefaction of oil‐palm empty fruit bunches. The characteristics of the adhesive samples were compared with those of a commercial phenol–formaldehyde resin. Three plywood specimens bonded with the new adhesive showed a very high tensile strength (63.04 MPa) and were very water resistant. The effect of the solid content of the adhesives on the tensile strength and gel time and various weight ratios of PEI on the tensile strength and water resistance of the plywood specimens were evaluated. Thermal stability tests revealed that the lignin polyol–tannin/PEI adhesives had a high heat resistance (360 °C). © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43437.     

Thermally exfoliated graphene oxide reinforced fluorinated pentablock poly(l‐lactide‐co‐ε‐caprolactone) electrospun scaffolds: Insight into antimicrobial activity and biodegradation

Three‐dimensional fluorinated pentablock poly(l ‐lactide‐co‐ε‐caprolactone)‐based scaffolds were successfully produced by the incorporation of thermally exfoliated graphene oxide (TEGO) as an antimicrobial agent with an electrospinning technique. In a ring‐opening polymerization, the fluorinated groups in the middle of polymer backbone were attached with a perfluorinated reactive stabilizer having oxygen‐carrying ability. The fiber diameter and its morphologies were optimized through changes in TEGO amount, voltage, polymer concentration, and solvent type to obtain an ideal scaffold structure. Instead of the widely used graphene oxide synthesized by Hummer's method, TEGO sheets having a low amount of oxygen produced by thermal expansion were integrated into the fiber structure to investigate the effect of the oxygen functional groups of TEGO sheets on the degradation and antimicrobial activity of the scaffolds. There was no antimicrobial activity in TEGO‐reinforced scaffolds in the in vitro tests in contrast to the literature. This study confirmed that a low number of oxygen functional groups on the surface of TEGO restricted the antimicrobial activity of the fabricated composite scaffolds. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43490.     

Effect of grafting yield and molecular weight of m‐TMI‐grafted‐PP on the mechanical properties of wood fiber filled polypropylene composites

m‐Isopropenyl‐α, α‐dimethylbenzyl isocyanate (m‐TMI) was grafted on isotactic polypropylene (PP) using di‐cumyl peroxide as a reaction initiator under varying reaction conditions to yield m‐TMI‐g‐PP coupling agent with four sets of grafting yield and molecular weight. Grafting yield of the synthesized m‐TMI‐g‐PP were 1.80%, 2.01%, 9.05%, and 8.86% and molecular weight of the corresponding grafted polymer were 129,225; [Correction made here after initial online publication.] 187,240; 124,130; and 180,838, respectively. Rubberwood flour reinforced polypropylene composites were prepared using these coupling agents and tested for mechanical properties. m‐TMI‐g‐PP coupling agent with 9.09% grafting and 124230 M_w was found to give the highest tensile and flexural strengths. Flexural modulus of the coupled composites was higher than uncoupled composites. Interfacial region of the composites characterized by scanning electron microscope (SEM) suggest effective wetting of fiber by PP in the case of coupled composites. The effect of fiber loading on composites indicates continuous increment in tensile and flexural strengths in coupled composites. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 44196.     

Preparation and properties of L‐lactide‐grafted sisal fiber–reinforced poly(lactic acid) composites

Pretreatment of the sisal fiber (SF) grafting with L‐lactide (LA) monomer via a ring‐opening polymerization catalyzed by a Sn(II)‐based catalyst was performed to improve the interfacial adhesion between SF and poly (lactic acid) (PLA). Biocomposites from LA‐grafted SF (SF‐g‐LA) and PLA were prepared by compression molding with fiber weight fraction of 10, 20, 30, and 40%, and then were investigated in contrast with alkali‐treated sisal fiber (ASF) reinforced PLA composites and untreated SF reinforced PLA composites. PLA composites reinforced by half‐and‐half SF‐g‐LA/untreated SF (half SF‐g‐LA) were prepared and studied as well, considering the disadvantages of SF‐g‐LA. The results showed that both the tensile properties and flexural properties of the SF‐g‐LA reinforced PLA composites were improved noticeably as the introduction of SF‐g‐LA, compared with pure PLA, untreated SF reinforced PLA composites and ASF reinforced PLA composites. The mechanical properties of the half SF‐g‐LA reinforced PLA composites were not worse, even better in some aspects, than the SF‐g‐LA reinforced PLA composites. Fourier transform infrared analysis and differential scanning calorimetry analysis exhibited that both the chemical composition and crystal structure of the SFs changed after LA grafting. In addition, the fracture surface morphology of the composites was studied by scanning electron microscopy. The morphological studies demonstrated that a better adhesion between LA‐grafted SF and PLA matrix was achieved. POLYM. COMPOS., 37:802–809, 2016. © 2014 Society of Plastics Engineers     

塔拉单宁水解废液回收奎尼酸的工艺试验

从塔拉单宁水解制备没食子酸的废液着手 ,用真空蒸发法分离去除盐酸 ,用不同的溶剂萃取法分离去除没食子酸 ,用活性炭吸附法和强碱阴离子交换法分离去除色素和糖类物质。从而提出了从塔拉单宁水解废液中回收目标产品奎尼酸的方法 ,产品得率约为理论值的 78%     

Application of citric acid as natural adhesive for wood

The development of natural adhesives derived from nonfossil resources is very important for the future. Besides, it is desirable to be safe adhesives without using harmful chemical substances. In this study, application of citric acid as a natural adhesive was investigated. Citric acid powder and bark powder obtained from Acacia mangium were used as raw materials. Citric acid powder was mixed with the bark powder, and the resulting powder mixture was poured into a metal mold. The mold was hot‐pressed at 180°C and 4 MPa for 10 min, and a bark molding was then obtained. The specific modulus of rupture and modulus of elasticity values of the molding containing 20 wt % citric acid were 18.1 MPa and 4.9 GPa, respectively. The molding did not decompose during a repeated boiling treatment. To clarify the effect of tannin on the adhesiveness of molding, bark was separated into tannin and residue. The molding was not obtained while using the tannin due to the marked fluidity, whereas it was obtained while using the residue, the same as while using the bark. It was considered that components other than tannin contributed to the adhesiveness. Based on the results of Fourier transform infrared spectra, the formation of ester linkages between carboxyl groups derived from citric acid and hydroxyl groups in the bark was confirmed. Accordingly, citric acid brought an adhesion by chemical bonding, and it could be used as a safe natural adhesive. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Graft copolymers from commercial chlorinated polypropylene via Cu(0)‐mediated atom transfer radical polymerization

Commercially available chlorinated polypropylene has been used as a macroinitiator for the Cu(0)‐mediated atom transfer radical polymerization of methyl methacrylate and tert‐butyl acrylate to obtain well‐defined graft copolymers. The relatively narrow molecular weight distribution in the graft copolymers and linear kinetic plots indicated the controlled nature of the copolymerization reactions. Both Fourier transform infrared and ¹H NMR studies confirmed that the graft reactions had taken place successfully. After graft copolymer formation, tert‐butyl groups of poly(tert‐butyl acrylate) side chains were completely converted into poly(acrylic acid) chains to afford corresponding amphiphilic graft copolymers. © 2016 Society of Chemical Industry     

Chemical grafting of polyaniline onto nylon66 fiber in different media

Graft copolymerization of polyaniline (PANI) onto nylon 66 fiber was carried out in two different media, hydrochloric acid and p‐toluene sulfonic acid (PTSA), using peroxodisulfate (PDS) as an initiator. Percentage grafting, percentage efficiency, and rate of grafting were determined. The grafting of PANI onto nylon 66 was confirmed through FTIR spectroscopy, cyclic voltammetry (CV), weight‐loss study, and conductivity measurement. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 79: 1283–1296, 2001     

Replacement of styrene with acrylated epoxidized soybean oil in an unsaturated polyester resin from propylene glycol,isophthalic acid,and maleic anhydride

Commercial unsaturated polyester (UPE) resins typically contain a high amount of volatile toxic styrene. A non‐volatile acrylated epoxidized soybean oil (AESO) was found to be an excellent replacement of styrene in a commercially available UPE resin [designated as Styrene‐(PG‐IPA‐MA)] that is derived from propylene glycol (PG), isophthalic acid (IPA), and maleic anhydride (MA) in terms of the mechanical properties of the resulting kenaf fiber‐reinforced composites. The AESO‐(PG‐IPA‐MA) resins had low viscosity and long pot life below 70°C for a typical fiber‐reinforced composite application. AESO and PG‐IPA‐MA were not able to form a strong polymer matrix individually for fiber‐reinforced composites. However, a combination of AESO and PG‐IPA‐MA saw strong synergistic effects between them. The flexural, tensile, and water absorption properties of kenaf fiber‐reinforced composites made from AESO‐(PG‐IPA‐MA) resins were comparable with or even superior to those from the Styrene‐(PG‐IPA‐MA) resin. The AESO/(PG‐IPA‐MA) weight ratio was investigated for maximizing the mechanical properties of the kenaf fiber‐reinforced composites. The curing mechanism of the AESO‐(PG‐IPA‐MA) resins is discussed in detail. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43052.     

Photo/pH dual‐responsive biocompatible poly(methacrylic acid)‐based particles for triggered drug delivery

A novel dual‐responsive (light and pH) particle based on poly(methacrylic acid), poly(methacrylic acid)–poly[1‐(2‐nitrophenyl)ethane‐1,2‐diyl bis(2‐methylacrylate)]was prepared with the facile method of two‐step homogeneous radical polymerization with methacrylic acid as the monomer and 1‐(2‐nitrophenyl)ethane‐1,2‐diyl bis(2‐methylacrylate) as a photodegradable crosslinker. Photolytic assessments were conducted upon irradiation with a UV lamp; this led to particle disintegration caused by cleavage of the photolabile crosslinking points. The light‐dependent degradation was investigated through particle size changes, absorption spectra variations, surface morphology changes, Fourier transform infrared spectroscopy, and the release of Nile red from the particles after irradiation. The pH dependence of the particle systems induced by the protonation and deprotonation of poly(methacrylic acid) was also confirmed by fluorescence spectroscopy. The triggered release of fluorescein diacetate was investigated to demonstrate that the release behavior in cells was light dependent. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 44003.