Effects of hygrothermally decomposed polyurethane on the curing and mechanical properties of carbon black‐filled epoxidized natural rubber vulcanizates

Hygrothermally decomposed polyurethane (HD‐PUR) was mixed up to 20 phr in epoxidized natural rubber (with 50 mol % epoxidation; ENR50) recipes, and the curing and mechanical behaviors were studied. Mechanical testing of the ENR50/HD‐PUR vulcanizates determined the tensile, tear, compression‐set, hardness, abrasion, hysteresis, and resilience properties. No significant changes were observed in the tensile properties with the incorporation of HD‐PUR. The ENR50 compounds showed an increase in compression set with increasing HD‐PUR content. Rubbers cured by a semi‐efficient vulcanization system gave the best overall performance. A further improvement in curing and mechanical properties was achieved by the carbon black grade N330 being replaced with a more active grade (N375). © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 2265–2276, 2002     

Photografting of PVC containing N,N‐diethyldithiocarbamate groups with vinyl monomers

Poly(vinyl chloride) (PVC) with pendent N,N‐diethyldithiocarbamate groups (PVC–SR) was prepared through the reaction of PVC with sodium N,N‐diethyldithiocarbamate (NaSR) in butanone and used as a photoinitiator for the grafting polymerization of three vinyl monomers [styrene (St), methyl methacrylate (MMA), and acrylamide (Am)]. The effects of ultraviolet (UV) irradiation time, PVC–SR amount, and the monomer amount on grafting and grafting efficiency were investigated. The results showed that PVC–SR could initiate the polymerization of three vinyl monomers effectively and obtained crosslinked copolymers. The grafting and grafting efficiency of styrene and methyl methacrylate were higher than those of acrylamide. The polymerization activity of three monomers was acrylamide > methyl methacrylate > styrene. By analyzing the UV spectrum of PVC–SR with a different irradiation time, it was confirmed that PVC–SR was dissociated mainly into macromolecular the sulfur radical PVC–S · and the small molecular carbon radical · C(S)N(C₂H₅)₂; the grafting polymerization mechanism was discussed. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 2569–2574, 2000     

Synthesis and properties of new polyurethane ionomers. I. Photosensitive cationomers with triazene units

New bifunctional triazene compounds 1‐(m‐ hydroxymethyl)phenyl‐3‐(2‐hydroxyethyl)‐3‐methyltriaz(1)ene and l‐p‐nitrophenyl‐3,3‐di(2‐hydroxyethyl)triaz(1)ene as intermediates in polyurethane synthesis were prepared. Photosensitive polyetherurethane cationomers based on poly(tetramethylene oxide) diol of 2,000 average molecular weight, tolylene‐2,4‐diisocyanate, and N‐methyldiethanolamine/triazene diols, as cochain extender, followed by a quaternization with benzyl chloride, were synthesized and characterized. Upon UV irradiation, feniltriazene chromophore in monomer and both polymers (ionomeric or nonionomeric type) is irreversibly cleaved, as evidenced in photolytic and kinetic studies. The rate constant of photolysis in ionomer film was lower than for the corresponding nonionic film. A positive pattern can then be developed by treatment with CHCl₃ that dissolves the exposed zone, while the unexposed area remains resistant and insoluble. By incorporating side nitrofeniltriazene groups, photostable polyurethanes were obtained. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 1203–1210, 2003     

Hydrolytic resistance of model poly(ether urethane ureas) and poly(ester urethane ureas)

Poly(ester urethane ureas) (PesURUs) and poly(ether urethane ureas) (PetURUs) synthesized from diphenylmethane-4,4′-diisocyanate and poly(butylene adipate) diol, and poly(tetramethylene oxide) diol or poly(propylene oxide) diol, respectively, were hydrolyzed at 70°C for various periods up to 16 weeks. Differences in thermal and mechanical properties of as-received dry samples are correlated with the number and strength of hydrogen bonds formed between urea/urethane groups of hard segments and polyester or polyether groups of soft segments. Gel permeation chromatography measurements show that the molar mass of linear PesURUs markedly decreases with the hydrolysis time, whereas that of linear PetURUs remains almost unaffected. PesURU crosslinked by polymeric isocyanate has lower crystallinity, but shows somewhat better resistance to hydrolysis than its linear counterpart because of its more stable three-dimensional molecular structure. Water uptake at 37°C, dynamic mechanical thermal analysis, and differential scanning calorimetry thermograms determined for redried hydrolyzed specimens concurrently show that advancing hydrolysis accounts for decrease in the crystallinity (if any) of soft polyester segments, in the efficacy of hydrogen bonding and in crosslinking density. Experimental data indicate that hydrolytic resistance of PetURUs is primarily determined by (1) the hydrolytic stability of individual types of present groups, (2) steric hindrances affecting the access of water molecules to these groups, and (3) the hydrophilicity of backbones. © 1998 John Wiley & Sons, Inc. J. Appl. Polym. Sci. 70: 577–586, 1998     

XPS studies of poly(acrylic acid) grafted onto UV photo-oxidized polystyrene surfaces

UV photo-oxidation of polystyrene was achieved with 253.7 and 253.7/184.9?nm radiation in the presence of an atmospheric pressure of oxygen and analyzed by X-ray photoelectron spectroscopy as a function of treatment time. A methodical increase in the atomic percentage (at.%) of oxygen occurred during 253.7?nm activation up to 2?h of treatment time. Photo-oxidation with the 253.7/184.9?nm lamps resulted in a saturation level of ca. 35 at.% O. Initially, C–O and C=O groups were formed and then O–C=O type moieties. Poly(acrylic acid) was partially and/or thinly grafted onto the oxidized polystyrene surfaces.     

聚四氟乙烯膜的亲水化改性研究进展

疏水性聚合物膜的亲水性改性是当前分离膜研究的热点之一。从等离子处理、等离子体接枝聚合、辐射接枝、化学改性和溅涂等几个方面综述了PTFE分离膜的各种亲水化改性方法的特点和改性效果,分析了其亲水改性机理,以及改性膜在生物和化工方面的应用。     

Thermogravimetric analysis of polyurethane–polysulfone blends

Thermal decomposition of blends of a poly(ester urethane) and poly(ether sulfone) with or without poly(urethane sulfone), taken as a compatibilizing agent, was studied by thermogravimetric analysis under dynamic conditions. Theoretical mass loss curves were compared with experimental ones and it was found that the blends studied possessed lower thermal stability than the pure polymers, indicating the presence of interactions in the degradation process. The shifts between the theoretical and experimental curves became smaller as the amounts of polysulfone increased, confirming the thermal stabilisation effect of this polymer. The analysis of activation energy revealed, for both binary and ternary systems, that E_CR (T_max corresponding to the main decomposition stage of polysulfone) increased as the amount of this polymer increased and also the reaction order became zero. For the polyurethane decomposition stages and blending revealed no significant changes as far as activation energy and order of reaction were concerned. © 2002 Society of Chemical Industry     

Radiation grafting of vinyl monomers onto poly(tetrafluoroethylene) powder produced by γ irradiation and properties of grafted poly(tetrafluoroethylene) filled low density polyethylene

Scrap poly(tetrafluoroethylene) (PTFE) was γ irradiated under an ambient atmosphere in order to produce extensive chain scission and oxidative degradation. After irradiation the PTFE was ground into a fine powder (2°‐PTFE) and grafted with styrene (St), vinyl acetate (VAc), and 4‐vinylpyridine (4‐VP) by using the direct irradiation technique. The grafted PTFE were then blended with low density polyethylene (LDPE). The study covered the characterization of irradiated PTFE and grafted 2°‐PTFE powder with various methods. Mechanical grinding was found to reduce trapped radicals formed during the irradiation process faster than the annealing process. Grafting on 2°‐PTFE was followed by gravimetric analysis, TGA, and the change in the particle size of the samples. Although we reached almost 20% grafting by weight in the St and 4‐VP monomers, VAc grafting was found to be maximum at around 8% by weight at the maximum absorbed dose. The addition of VAc grafted 2°‐PTFE into LDPE produced better final mechanical properties with a fine dispersion. However, as may be expected, the incorporation of the other two 2°‐PTFEs into LDPE showed low film quality and poor mechanical properties. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 79: 816–826, 2001     

Surface modification of kaolin. 2. Enhanced steric stabilisation of polymer-modified kaolin

The polymer-modified surface of kaolin was studied to determine the effect of changing the molecular weight of the polymer chain grafted on the surface. The particle was modified by attaching poly(ethylene oxide) to the surface using a urethane linkage. Upper critical flocculation temperature and contact angle measurements were conducted to quantify the changes in surface characteristics and stability in an aqueous dispersion. The effect of pH on stability and grafted density of polymer chains showed the mechanism of stabilisation to be that of enhanced steric stabilisation. The kaolin particle was also modified with the more hydrophobic poly(propylene oxide). The behaviour was characterised as for poly(ethylene oxide) and interesting differences in extent and mechanism for stabilisation were observed.     

Surface modification of a biomedical poly(ester)urethane by several low‐powered gas plasmas

Several low‐powered gas plasmas were employed to treat a biomedical poly(ester)urethane using the treatment gases of CO₂, O₂, NH₃, and SO₂ with different treatment time (2, 5, 10, and 15 min). The changes of the physical and chemical characteristics of the biopolymer surface were studied. Surface morphology was evaluated by scanning probe microscopy, which showed increased roughness of the surface after plasma treatment. The wettability of the surface was examined by static water contact angle (SCA) measurements, which presented that there was a decrease of SCA in all plasma treatments compared with the untreated surface and that each gas plasma had an optimum treatment time accompanied by a minimum contact angle. X‐ray photoelectron spectroscopy indicated the changes of the surface functional groups. The data demonstrated that CO₂ and O₂ plasmas resulted in the incorporation of oxygen‐containing groups, while NH₃ plasma resulted in the combination of nitrogen‐containing groups, and SO₂ plasma resulted in the formation of sulfur‐containing groups. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 1273–1282, 2006     

Preparation of hydrophilic woven fabrics: Surface modification of poly(ethylene terephthalate) by grafting of poly(vinyl alcohol) and poly(vinyl alcohol)-g-(N-vinyl-2-pyrrolidone)

One of the most industrially important synthetic textile materials, woven poly(ethylene terephthalate) (PET) fabrics, have limitations in the usage of casual apparel applications due to their unwanted hydrophobicity. For that reason, in this study, to impart permanent hydrophilicity to the PET fabrics, hydrophilic poly(vinyl alcohol) (PVA) and a PVA-based copolymer were introduced to the alkaline hydrolysis pretreated PET surface by graft copolymerization for the first time. The graft modification of PET fabric surface was performed with an industrial-adaptable approach. The synthesis of a novel PVA-g-(N-vinyl-2-pyrrolidone) copolymer was achieved by the introduction of glycidyl methacrylate monomer to the PVA backbone. The structure of the copolymer was evidenced by attenuated total reflection–Fourier transform infrared spectroscopy and ¹H-NMR techniques. The introduction of PVA and copolymer structures with desired functional groups to the PET fabric surface was confirmed with the X-ray photoelectron spectroscopy technique. It was obtained that the contact angle–wetting time of PET fabric (145° and 98 s) could be dropped to 37° and 0.1 s and 64° and 0.7 s after PVA and copolymer grafting, respectively. This suggests that the graft-modified PET fabrics may find the potential of use in the textile applications as the alternative hydrophilic materials. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48584.     

Synthesis and hydrophilicity of poly(butylene 2,6‐naphthalate)/poly(ethylene glycol) copolymers

Poly(butylene 2,6‐naphthalate) (PBN)/poly(ethylene glycol) (PEG) copolymers were synthesized by the two‐step melt copolymerization process of dimethyl‐2,6‐naphthalenedicarboxylate (2,6‐NDC) with 1,4‐butanediol (BD) and PEG. The copolymers produced had different PEG molecular weights and contents. The structures, thermal properties, and hydrophilicities of these copolymers were studied by ¹H NMR, DSC, TGA, and by contact angle and moisture content measurements. In particular, the intrinsic viscosities of PBN/PEG copolymers increased with increasing PEG molecular weights, but the melting temperatures (T_m)_, the cold crystallization temperatures (T_cc)_, and the heat of fusion (ΔH_f) values of PBN/PEG copolymers decreased on increasing PEG contents or molecular weights. The thermal stabilities of the copolymers were unaffected by PEG content or molecular weight. Hydrophilicities as determined by contact angle and moisture content measurements were found to be significantly increased on increasing PEG contents and molecular weights. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 2677–2683, 2006     

The effect of the soft segment of prepolymers on properties of poly(urethane‐ester) and its biodegradability

The influence of soft‐segment prepolymers prepared through the polymerization of δ‐valerolactone (VL) and 2,2‐dimethyl‐1,3‐propandiol (DP) monomers on the structure and properties of poly(urethane‐ester) as well as its biodegradability were investigated. Poly(urethane‐ester) was prepared in two steps. The first step was the preparation of prepolymers with various chain lengths by polymerizing VL and DP monomers in the presence of a distannoxane catalyst at 100 °C under nitrogen atmosphere. The second step was the preparation of poly(urethane‐ester) by polymerizing 4,4′‐methylene‐bis(phenyl isocyanate) (MDI) and prepolymers with various chain lengths in the absence of catalysts. The poly(urethane‐ester) was characterized through an analysis of functional groups (FTIR), thermal properties (differential thermal analysis/TGA), mechanical properties (tensile tester), crystallinity (XRD) and biodegradability. An increased chain length of the prepolymer used in polymerization with MDI leads to an increase in the thermal properties and crystallinity of poly(urethane‐ester). However, the maximum biodegradability in the activated sludge was observed in the poly(urethane‐ester) prepared by polymerizing MDI and prepolymers with a molar VL/DP ratio of 20/1. The amorphous parts of polymers were more easily decomposed by microorganism enzymes than were the crystalline parts after an incubation period of 30 days. Copyright © 2011 Society of Chemical Industry     

基于PVDF薄膜辐照接枝制备质子交换膜

含氟磺酸型质子交换膜是一类具有高热稳定性、化学稳定性及良好力学性能的离子交换膜,具有极其广阔的应用前景。采用⁶⁰Co辐照接枝技术,在聚偏氟乙烯（PVDF）基膜上产生自由基聚合位点,进而接枝对苯乙烯磺酰氯单体,经过一定条件酸碱处理得到一种新型偏氟磺酸型质子交换膜。并对其进行红外分析,结果显示PVDF膜上成功接枝上了对苯乙烯磺酰氯单体;定量研究了在相同辐照总剂量、不同剂量率条件下,所得质子交换膜的质子传导率、吸水率及离子交换容量与接枝率的关系,结果表明：当剂量率为40 Gy·min^-1时,所得质子交换膜接枝率为52.7%,吸水率为36.85%,80℃时质子传导率达到136 mS·cm^-1,离子交换容量为1.274 mmol·g^-1。     

Functionalization of poly(ester‐urethane) surface by radiation‐induced grafting of N‐isopropylacrylamide using conventional and reversible addition–fragmentation chain transfer‐mediated methods

The functionalization of poly(ester‐urethane) (PUR) surface was conducted using radiation‐induced grafting. A thermosensitive layer constructed from N‐isopropylacrylamide (NIPAAm) was introduced onto a polyurethane film and characterized using attenuated total reflection Fourier transform infrared and X‐ray photoelectron spectroscopies and contact angle measurements. Size exclusion chromatography was used to analyse the PUR‐graft‐PNIPAAm copolymers and homopolymers formed in solution. Additionally, reversible addition–fragmentation chain transfer (RAFT) polymerization was performed in order to obtain PNIPAAm‐grafted surfaces with well‐defined properties. Atomic force microscopy was used to evaluate the surfaces synthesized via conventional and RAFT‐mediated grafting methods. The results of various techniques confirmed the successful grafting of NIPAAm from PUR film. © 2015 Society of Chemical Industry     

Properties of modified polyacrylonitrile membranes prepared by copolymerization with hydrophilic monomers for water–ethanol mixture separation

A new kind of terpolymer membrane was employed to separate a permselective water–alcohol mixture. This membrane was prepared via the copolymerization of acrylonitrile, sodium salt styrene sulfonic acid (SStSA), and hydroxyethyl methacrylate in dimethylsulfoxide with azobisisobutyronitrile as an initiator. The reaction mechanism, resultant structure, and polymer composition were confirmed by IR and elemental analysis. The effects of the feed composition on the polymer composition, mechanical properties, thermal properties, and degree of swelling were investigated. It was found that water permeated through the membrane preferentially in a water/alcohol system. The flux increased with the increase of SStSA, but the separation factor decreased drastically with higher SStSA. For a 50 wt % water–ethanol mixture, a flux of 0.65 kg/m² h and a separation factor of 212 were obtained at 30°C when the membrane containing the highest SStSA content was used. The capacities of the metal ions absorbed by the membranes were investigated in the study. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 244–250, 2003     

A photochemical method for immobilization of azidated dextran onto aminated poly(ethylene terephthalate) surfaces

BACKGROUND: Dextran, a bacterial polysaccharide, has been reported to be as good as poly(ethylene glycol) in its protein‐rejecting and cell‐repelling abilities. In addition, the multivalent nature of dextran is advantageous for surface grafting of biologically active molecules. We report here a method to photochemically bind dextran hydrogel films to aminated poly(ethylene terephthalate) (PET) surfaces in aqueous media using a heterobifunctional crosslinker, 4‐azidobenzoic acid. In order to achieve this, dextran was first functionalized with the crosslinker using carbodiimide chemistry followed by photo‐crosslinking and immobilization onto the nucleophile‐rich aminated PET surfaces. RESULTS: The presence of the immobilized dextran on PET was verified by attenuated total‐reflection Fourier transform infrared spectroscopy, X‐ray photoelectron spectroscopy, scanning electron microscopy and contact angle measurements. The grafted surface was highly hydrophilic due to the heavily hydrated polysaccharide network on the surface as demonstrated by the near zero water contact angle. CONCLUSION: A photochemical method for surface immobilization of dextran onto aminated PET using aryl azide chemistry is a facile technique to generate highly hydrophilic and more hemocompatible surfaces. The aryl nitrenes generated by photolysis produce a metastable, electron‐deficient intermediate, azacycloheptatetraene, which is believed to be responsible for the simultaneous crosslinking of dextran and its immobilization onto the aminated PET surface. The aryl azide chemistry reported here for dextran could be useful as a versatile technique for surface modification of other nucleophile‐rich polymers to create dextran‐ or similar polysaccharide‐immobilized surfaces. Copyright © 2007 Society of Chemical Industry     

基于双硫键和氢键协效的高性能自修复聚氨酯脲的研制

为解决自修复弹性体同时具有优异的力学性能和自修复性能的矛盾,首先将原料胱氨酸（CYS）进行甲酯化得到含双硫键的二胺扩链剂胱氨酸二甲酯（CDE）,然后以聚四氢呋喃醚二醇（PTMG）为软段,异佛尔酮二异氰酸酯（IPDI）和CDE为硬段,固定摩尔比为1∶3∶2,采用两步法制备了自修复聚氨酯脲（SH-PUU）弹性体,并对SH-PUU进行了红外光谱测试、拉曼光谱测试、力学性能测试、自修复性能测试、划痕修复微观形貌观察、应力松弛和动态力学性能测试。实验结果表明：SH-PUU的软段和硬段的玻璃化转变温度分别为-38.5℃和77.6℃,微相分离程度较高,SH-PUU具有良好的力学性能,拉伸强度为13.6MPa,断裂伸长率达531.3%;同时SH-PUU具有高效的自修复能力,试样在经过80℃修复2h后,基于拉伸强度的自修复效率达到97.1%,SH-PUU的力学性能和自修复性能达到较好的平衡。SH-PUU的高自修复能力是由动态双硫键和氢键协效增强引起的,其通过加热方式的自修复机理为：SH-PUU中的动态双硫键在80℃发生可逆交换反应,SH-PUU中的氢键在低于100℃时会重新形成。     

Effects of reaction and cure temperatures on morphology and properties of poly(ester‐urethane)

Poly(ester‐urethane) was synthesized from poly(ethylene glycol adipate) (PEG) and 2,4‐toluene diisocyanate (TDI) to study the effects of reaction temperature and cure temperature on the crystallization behavior, morphology, and mechanical properties of the semicrystalline polyurethane (PU). PEG as soft segment was first reacted with TDI as hard segment at 90, 100, and 110°C, respectively, to obtain three kinds of PU prepolymers, coded as PEPU‐90, PEPU‐100, and PEPU‐110. Then the PU prepolymers were crosslinked by 1,1,1‐tris (hydroxylmethyl) propane (TMP) and were cured at 18, 25, 40, 60, and 80°C. Their structure and properties were characterized by attenuated total reflection Fourier transform infrared, wide‐angle X‐ray diffraction, scanning electron microscopy, dynamic mechanical analysis, and tensile testing. With an increase of the reaction temperature from 90 to 100°C, the crystallinity degree of soft segment decreased, but interaction between soft and hard segments enhanced, leading to the increase of the glass transition temperature (T_g) of soft domain and tensile strength. When the cure temperature was above 60°C, miscibility between soft and hard segments of the PEPU films was improved, resulting in relatively low crystallinity and elongation at break, but high soft segment T_g and tensile strength. On the whole, all of the PEPU‐90, PEPU‐100, and PEPU‐110 films cured above 60°C possessed higher tensile strength and elongation at break than that of the films cured at other temperatures. The results revealed that the reaction temperature and cure temperature play an important role in the improvement of the crosslinking structure and mechanical properties of the semicrystalline PU. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 708–714, 2006