Effects of fillers on mechanical properties of a water‐swellable rubber

The mechanical properties of the water‐swellable rubber prepared by blending polychloroprene with precipitated silica, crosslinked sodium polyacrylate, polyethylene oxide, and vulcanizing agents—such as stress at break, strain at break, modulus, energy at break, and hardness—were studied before and after swelling with water. The results showed that the addition of the reinforcing filler (precipitated silica) increased the mechanical properties, while adding crosslinked sodium polyacrylate decreased the mechanical properties, although it could improve water‐absorbent properties of the water‐swellable rubber. If some polyethylene oxide was included in the rubber formulation, the water‐absorbent properties and the mechanical properties of the rubber both increased; but, with the increase of more polyethylene oxide, the mechanical properties decreased. Wide‐angle X‐ray diffracting analysis was conducted to study the crystalline behavior of the rubber, which showed that the crystallinity of the vulcanized polychloroprene increased first and then decreased with an increase in the amount of polyethylene oxide. The crosslink density of the rubber was calculated by the Flory–Rehner equation. The mechanical strength of the rubber significantly decreased after swelling with water, compared with that before swelling with water. The morphology of blends was shown by scanning electron microscopy graphs. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 72: 577–584, 1999     

Synthesis and characterization of novel poly(acrylamide‐co‐acrylic acid‐co‐2‐hydroxy ethyl actylate) hydrogels: Mathematical approach in investigation of swelling kinetics and diffusion models

In this study, a series of poly(acrylamide‐co‐acrylic acid‐co‐2‐hydroxy ethyl actylate) [AM‐co‐AA‐co‐HEA] hydrogels have been synthesized by varying the acrylic acid (AA)content over eightfold in feed in the range of 33.34–93.76% by keeping other monomer constant. These hydrogels were characterized by FTIR, SEM analysis, elemental analysis, residual acrylic acid analysis, network parameters, and dynamic swelling behavior. The swelling study showed that equilibrium swelling ratio was nonlinearly increased with increasing AA content. Interestingly, the equilibrium swelling ratio decreased from 53.42 to 48.52 for 75–80% AA content hydrogel. The swelling data were found to satisfactorily fit Fick's second law, demonstrating that diffusion rate of water uptake was primarily Fickian. From model fitting, it was observed that early model was applicable for first 30% water absorption, and late model was applicable for latter 70% water absorption for increasing AA content from 33.34–90.90%. For 93.76% AA, early‐time model was extended up to first 50% of water absorption and late model was contracted for latter 50% water absorption, indicating that excessive AA content affects the applicability range of early‐time and late‐time diffusion models for water absorption. Etters model was best applicable to all type of hydrogels and followed over all swelling range. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

TPEE/P(AA⁃co⁃AM)吸水膨胀弹性体的制备及性能研究

针对吸水膨胀弹性体(WSE)在含盐溶液中膨胀倍率普遍不高、吸盐水性能和耐热性能不佳等问题,采用反向悬浮聚合方法,将丙烯酸(AA)单体与丙烯酰胺(AM)单体进行共聚,制备了新型聚丙烯酸?丙烯酰胺[P(AA?co?AM)]耐盐吸水树脂,并以热塑性聚醚酯弹性体(TPEE)为基体,制备了TPEE/P(AA?co?AM)吸水膨胀...     

Mechanical properties,water‐swelling behavior,and morphology of water‐swellable rubber prepared using crosslinked sodium polyacrylate

A novel water‐swellable rubber (WSR) has been prepared by blending chlorobutadiene rubber (CR), reactive clay and other additives with crosslinked sodium polyacrylate (CSP), which was modified by interpenetrating polymer networks (IPNs) technology with crosslinked P(AA‐co‐BA). The structure of WSR was characterized by scanning electron microscopy (SEM). The mechanical properties, water‐swelling ratio by mass, and the percentage loss of CSP in the WSR were investigated. The results showed that the modified CSP grains can be dispersed well in the CR, and that it resulted in increase of mechanical properties and water‐swelling ratio and in decrease of percentage loss of CSP, compared with the unmodified one. When the percentage content of crosslinked P(AA‐co‐BA) used to modify CSP reached 30%, the tensile strength, elongation at break, and water‐swelling ratio of WSR exhibited maximum value, and percentage loss of CSP exhibited minimum value. When the content of CSP in WSR was 30 phr, the tensile strength, elongation at break, and water‐swelling ratio and percentage loss of CSP of the WSR containing CSP modified were 7.7 MPa, 1530, 438, and 2.5%, respectively. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 1489–1496, 2006     

Synthesis and swelling properties of grafting‐type and crosslinking‐type water‐swellable elastomers

A grafting water‐swellable elastomer (WSE) that is, chlorinated polyethylene (CPE)‐graft‐poly(ethylene glycol) (PEG), was synthesized by a grafting reaction. The synthesis was based on the reaction between chlorine in CPE and sodium salt of PEG. PEG with molecular weights of 600 and 1000 were used. The maximum grafting percentage of the resulted copolymers after purification was 9.79%. The structure of the copolymer was confirmed by an IR spectrum. The grafting degree and PEG content increased with increasing reaction time and reaction temperature. The equilibrium swelling degree of the grafting copolymer was very small, only 16.94%. However, for the crosslinking WSE, the swelling degree was influenced by the absorbency temperature and absorbency time. The absorbency rate was faster than that of the grafting WSE, and the swelling degree in the equilibrium state was higher than that of the grafting WSE, too. The maximum swelling degree of the crosslinking WSE was 70%. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 2637–2642, 2007     

Swelling behavior and determination of diffusion characteristics of acrylamide–acrylic acid hydrogels

In this study, a random copolymer of acylamide and acrylic acid [poly(AAm‐co‐AA)] was prepared by a redox copolymerization method of their aqueous solutions. The effects of initial AAm/AA mole ratio, PEG 4000 content, and N,N′‐methylenebisacrylamide concentration on swelling behavior were investigated in water. Average molecular weights between crosslinks, percentage swelling, swelling equilibrium values, and diffusion/swelling characteristics (i.e., the structure of network constant, the type of diffusion, the initial swelling rate, swelling rate constant) were evaluated for every hydrogel systems. The hydrogels showed mass swelling capabilities in the range 789–1040% (for AAm/AA hydrogels), 769–930% (for AAm/AA hydrogels in the presence of PEG 4000), and 716–1040% (for AAm/AA hydrogels containing different concentrations of the crosslinker). The swelling capabilities of the hydrogels decreased with the increasing AA, PEG 4000, and crosslinker concentrations. The diffusion of water into AAm/AA hydrogels was found to be a non‐Fickian type. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 1289–1293, 2004     

改性组分对遇水膨胀橡胶吸水膨胀性能影响的逾渗理论分析

根据逾渗理论模型对自制遇水膨胀橡胶的平衡吸水膨胀率与吸水树脂用量之间的关系进行了分析和相关的计算,并确定了该遇水膨胀橡胶共混体系的临界基层厚度Tc,在此基础上证明了所制备的遏水膨胀橡胶共混体系的平衡吸水膨胀率（Sw）与复合球体积分数（φs）间的关系服从逾渗理论的标度定律关系,并求得了不同共混体系的临界指数g值;最后将改性吸水树脂中改性组分用量与临界指数g值的大小、遇水膨胀橡胶平衡吸水膨胀性能之间的关系等相联系进行分析。结果表明,临界指数g值越接近理论值,遇水膨胀橡胶的平衡吸水膨胀率越大,当改性组分质量分数为30％,吸水树脂用量为30质量份时,遇水膨胀橡胶的平衡吸水膨胀率达到438％,临界指数g值为0．44,其主要原因是改性组分的引入使吸水树脂在橡胶中的分散性得到了明显的改善。     

CPE-g-(AM-co-MAH)增容氯化聚乙烯吸水膨胀弹性体的研究

采用机械共混法将氯化聚乙烯(CPE)与自制吸水树脂丙烯酸钠-丙烯酰胺-甲基丙烯酸羟乙酯三元共聚物P(NaAA-AM-HMA)共混合成吸水膨胀弹性体,讨论了吸水树脂用量、增容剂CPE-g-(AM-co-MAH)用量对吸水膨胀弹性体吸水性能、力学性能的影响。结果表明,未添加增容剂的共混物随吸水树脂量增大,吸水率增大,但是力学性能降低。将增容剂添加到共混试样中,改善了CPE与吸水树脂P(NaAA-AM-HMA)的相容性,提高了体系的力学性能和吸水性能,以加入3Phr的CPE-g-(AM-co-MAH)的增容效果最为明显。     

Synthesis of multifunctional high strength,highly swellable,stretchable and self‐healable pH‐responsive ionic double network hydrogels

The multifunctional double network (DN) soft hydrogels reported here are highly swellable and stretchable pH‐responsive smart hydrogel materials with sufficient strength and self‐healing properties. Such multifunctional hydrogels are achieved using double crosslinking structures with multiple physical and chemical crosslinks. They consist of a copolymer network of acrylamide (AM) and sodium acrylate (Na‐AA) and other reversible network of poly(vinyl alcohol)–borax complex. They were characterized by Fourier transform IR analysis and studied for their hydrogen bonding and ionic interaction. The degree of equilibrium swelling was observed to be as high as 5959% (at pH 7.0) for a hydrogel with AM/Na‐AA = 25/75 wt% in the network (GS‐6 sample). The highest degree of swelling was observed to be 6494% at pH 8.5. The maximum tensile strength was measured to be 1670, 580 and 130 kPa for a DN hydrogel (GS‐2 sample: AM/Na‐AA =75/25 wt% with 20, 40 and 60 wt% water content, respectively). The self‐healing efficiency was estimated to be 69% for such a hydrogel. These multifunctional DN hydrogels with amalgamation of many functional properties are unique in hydrogel materials and such materials may find applications in sensors, actuators, smart windows and biomedical applications. © 2018 Society of Chemical Industry     

双亲性氯化聚乙烯接枝共聚物的吸水膨胀性能

采用反相悬浮法制备了颗粒状接枝共聚物———氯化聚乙烯接枝丙烯酸(CPE-g-AA)、氯化聚乙烯接枝丙烯酰胺(CPE-g-AM)和氯化聚乙烯接枝混合单体丙烯酸、丙烯酰胺[CPE-g-(AA-AM)],并通过热压法制得接枝共聚物片材。考察了颗粒状接枝共聚物和接枝共聚物片材的吸水膨胀性能。结果表明,接枝共聚物的吸水性能与接枝单体的种类及其接枝率有关,相同接枝率的CPE-g-AA的吸水量比CPE-g-AM的大。当混和单体丙烯酸/丙烯酰胺的质量比为2/2时,所得接枝共聚物的抗盐性能最好。接枝共聚物片材可反复吸水膨胀,接枝率为62%的CPE-g-AA片材的二次吸水达到平衡时的吸水率和膨胀率分别为120%和41%。通过测定接枝共聚物的接触角表明,CPE-g-AA对水的润湿作用比CPE-g-AM明显。     

P(AA/AM/APEG)/纳米二氧化硅复合高吸水树脂的合成及性能

以丙烯酸(AA)、丙烯酰胺(AM)、烯丙基聚氧乙烯醚(APEG)为单体,再引入纳米二氧化硅(nano-SiO_2),以过硫酸铵为引发剂,N,N-亚甲基双丙烯酰胺(MBA)为交联剂,采用水溶液聚合法制备了P(AA/AM/APEG)/纳米二氧化硅有机/无机复合高吸水性树脂,考察了交联剂加量、引发剂加量、纳米二氧化硅加量对树脂吸水倍率的影响,并用红外光谱和扫描电镜对产物进行了表征。结果表明:合成最佳条件加入纳米二氧化硅能提高树脂的吸水性能,粒径在80~120目时,复合树脂吸水倍率达到1 865 g/g,P(AA/AM/APEG)树脂吸水倍率为1 681g/g;温度在20~60℃时,复合吸水树脂吸水倍率变化幅度不大;pH在6~8时,其吸水性能最好,吸水倍率为1 865~1 444 g/g;此外,复合树脂具有较好的保水性能,树脂常温下保存15 d,其保水率达到83.2%。红外光谱和扫描电镜分析表明,纳米二氧化硅成功接枝到聚合物上并形成海绵状结构。     

Undesirable effects of heating on hydrogels

Heating is the most conventional drying method for removing water from as‐synthesized hydrogels in laboratory and industry. In this article, the effects of the heating temperature (60–200°C) and time (10 min–24 h) on swelling properties of highly absorbent hydrogels based on 2‐acrylamido‐2‐methylpropane sulfonic acid (AMPS), acrylic acid (AA), potassium acrylate (KA), and acrylamide (AM) were studied. Crosslinkers methylene bisacrylamide (MBA) and poly(ethyleneglycol) dimethacrylate (PEGDMA) were used in the syntheses. Depending on the hydrogel structural composition and its drying temperature and time, the swelling capacities were extremely changed. Generally, AA‐, KA‐, and AM‐based hydrogels showed more hydrolytic‐thermal stability than the corresponding AMPS‐based hydrogels. MBA‐crosslinked hydrogels generally exhibited higher vulnerability against heating. Swelling of PEGDMA‐crosslinked poly(AM‐KA‐AA) hydrogel was greatly increased after heating, whereas its analogousAM‐free sample exhibited huge loss of swelling. PEGDMA‐crosslinked poly(AMPS) samples also exhibited swelling reduction after drying. Rheological studies showed that the storage modulus was highly reduced (～ 5200 Pa) after heating of MBA‐crosslinked poly(AMPS) hydrogels, which reconfirmed the crosslink cleavage. Mechanistic discussions were proposed for the thermal‐induced swelling changes. It was concluded that the chemical nature of both crosslinker and monomer must be taken into consideration to choose the temperature and time of the hydrogel drying. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

P(AM-g-NBR)改性共混型吸水膨胀丁腈橡胶制备与性能研究

以两亲性接枝聚合物丙烯酰胺接枝丁腈橡胶P(AM-g-NBR)为增溶剂,将丁腈橡胶(NBR)与自制的吸水树脂(SAR-PA)共混制备出了吸水膨胀丁腈橡胶WSR-NB。考察了P(AM-g-NBR)及SAR-PA对吸水橡胶性能的影响。实验结果表明,P(AM-g-NBR)的加入可明显改善吸水橡胶的力学性能及吸水性能;随吸水树脂用量增大,吸水橡胶的拉伸强度降低,吸水率增大。     

淀粉接枝丙烯酸/丙烯酰胺耐盐型高吸水性树脂的制备

以淀粉为主要原料,丙烯酸（AA）和丙烯酰胺（AM）为接枝单体,采用水溶液聚合法制备具有耐盐型高吸水性树脂。探讨了原料配比、丙烯酸中和度、反应温度等因素对产物吸水性能的影响,结果表明,在聚合温度为50℃,淀粉、丙烯酰胺、引发剂和交联剂用量分别为丙烯酸用量的15%、40%、2.4%和0.03%的条件下,所制备的耐盐型高吸水...     

Polypropylene/polypropylene‐grafted acrylic acid blends for multilayer films: Preparation and characterization

Polypropylene (PP) was functionalized with acrylic acid (AA) and styrene (st) as a comonomer by means of a radical‐initiated melt‐grafting reaction. FTIR, ESCA, and ¹H‐NMR spectroscopies were used to characterize the formation of polypropylene grafted with acrylic acid (PP‐g‐AA) and polypropylene grafted with acrylic acid and styrene (PP‐g‐AAst). The content of AA grafted onto PP was determined by using volumetric titration. Blends of PP with 0–100 wt % of PP‐g‐AA were prepared by melt mixing. The effect of the modified polymer content on the surfaces of cast films was characterized through FTIR–ATR and ESCA analysis as well as contact‐angle, wetting‐tension, and ink‐adhesion measurements. The influence of the content of AA on the melting and crystallization temperature of PP was investigated by DSC. The contact angles of water on cast‐film surfaces of PP/PP‐g‐AA blends decreases with increasing modified polymer content and decreasing PP‐g‐AA molecular weight. A notorious improvement on wetting tension was observed with increasing modified polymer content and decreasing PP‐g‐AA molecular weight. From FTIR–ATR and ESCA spectra of the blends, a calculation was made of the carbonyl index on the films' surfaces. It was found that the higher the carbonyl index, the lower the contact‐angle value for the polypropylene blends. An increase in crystallization temperature of PP was observed when AA monomers were grafted into PP and with increasing PP‐g‐AA content in the blend, probably caused by a nucleation effect of AA monomers that would improve the crystallization capability of PP. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 79: 1497–1505, 2001     

In situ formed internal water channels improving water swelling and mechanical properties of water swellable rubber composites

In this study, electrospun nanofibers of poly (vinyl alcohol) (PVA) and styrene–butadiene–styrene triblock copolymer (SBS) were employed in conventional water‐swellable rubber (WSR) to design WSR composites with improved water swelling and mechanical properties. With the introduction of PVA nanofibers, considerable improvement in elasticity, strength, and water‐swelling behavior was observed. After immersion, PVA nanofibers dissolved within the composite to in situ form water channels to connect isolated super‐absorbent polymers (SAPs). Those water channels led to an increase in water uptake by the WSR composite. Furthermore, the secondary water‐swelling behaviors of the WSR composite showed a remarkable increase in swelling rate as well as in mechanical properties. The addition of SBS nanofibers had a marked impact on the mechanical properties of the WSR composite. Their roles became more pronounced after water immersion. The proposed enhancement mechanism is also discussed. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44548.     

Synthesis and properties of electrically‐sensitive poly(acrylic acid‐co‐acetoacetoxy ethyl methacrylate) gels

A series of electric field sensitive copolymer P(AA‐co‐AAEM) gels of acrylic acid (AA) with acetoacetoxy ethyl methacrylate (AAEM) were prepared by free‐radical copolymerization, with N,N′‐methylene bisacrylamide (MBAAm) and ammounium persulfate (APS) as crosslinking agent and initiator, respectively. The structures and properties of the gels were tunable by changing the monomer feed weighty ratio (R) (R = W_AAEM/(W_AAEM + W_AA) of AAEM and AA. The influences of the NaCl concentration and pH buffer solutions on the equilibrium swelling ratios of the gels were studied in detail. It is shown that both NaCl concentration and pH value of the buffer solution affect the swelling properties of the P(AA‐co‐AAEM) gels greatly. Moreover, the gel deswelling behavior induced by a direct current electric field was investigated and an excellent electric‐sensitivity was found. Among all the samples, the gel with monomer feed weighty ratio (R) = 0.1479 showed the best electrical contraction properties. On the basis of the experimental results, the mechanism of the electricity‐induced deswelling behavior was presented. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Characteristics of water-absorbent polymer emulsions

Water-in-Oil (W/O) and Oil-in-Water (O/W) type water absorbent polymer emulsions were studied using two different polymerization methods. W/O type water absorbent polymer emulsions were prepared by the inverse emulsion polymerization of ammonium acrylate (AA), the quaternized salt of dimethyl-aminoethyl methacrylate (DMQ) and acrylamide (AM) with N,N-methylene-bisacrylamide (MBA) as a crosslinker. A pH sensitive water absorbent polymer emulsion was prepared by the conventional emulsion polymerization of diethyl-aminoethyl methacrylate (DEAEMA) with ethylene glycol dimethacrylate (EGDMA) as a crosslinker. It was confirmed that the water absorption capacity of crosslinked polymers in inverse emulsion was controlled by crosslink density and dissociative charge density, and the crosslinked polyDEAEMA particles had a phase transition property of swelling and shrinking with pH. The dispersions of these water swollen crosslinked polymer particles exhibited an increase in viscosity and thixotropic fluidity.     

Synthesis and network parameters of hydrophobic poly(N‐[3‐(dimethylaminopropyl)]methacrylamide‐co‐lauryl acrylate) hydrogels

Hydrophobic poly(N‐[3‐(dimethylaminopropyl)]methacrylamide‐co‐lauryl acrylate) [P(DMAPMA‐co‐LA)] hydrogels with different LA content were synthesized by free‐radical crosslinking copolymerization of corresponding monomers in water by using N,N‐methylenebis(acrylamide) as the crosslinker, ammonium persulfate as the initiator, and N,N,N′,N′‐tetramethylethylenediamine as the activator. The swelling equilibrium of the hydrogels was investigated as a function of temperature and hydrophobic comonomer content in pure water. An interesting feature of the swelling behavior of the P(DMAPMA‐co‐LA) hydrogels with low LA content was the reshrinking phase transition where the hydrogels swell once and collapse as temperature was varied in the range of 30–40°C. The average molecular mass between crosslinks (M?_c) and polymer–solvent interaction parameter (χ) of the hydrogels were calculated from equilibrium swelling values. The enthalpy (ΔH) and entropy (ΔS) changes appearing in the χ parameter for the hydrogels were determined by using the Flory–Rehner theory based on the phantom network model of swelling equilibrium. The positive values for ΔH and ΔS indicated that the hydrogels had a positive temperature‐sensitive property in water, that is, swelling at a higher temperature and shrinking at a lower temperature. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 4159–4166, 2006     

Water‐swelling elastomer prepared by in situ formed lithium acrylate in chlorinated polyethylene

Lithium acrylate (LiAA) was in situ prepared in a chlorinated polyethylene (CPE) matrix through the neutralization of lithium hydroxide (LiOH) and acrylic acid (AA) during mixing. The obtained compounds were vulcanized with dicumyl peroxide (DCP). The in situ preparation and polymerization of LiAA were characterized with Fourier transform infrared spectrometry. The crosslink density analysis results indicated that the CPE/LiAA vulcanizates contained both covalent bonds and ionic bonds. The effects of the DCP and LiAA contents on the mechanical properties and water‐swelling properties of the CPE/LiAA vulcanizates were studied. The relationship between the LiOH/AA molar ratio and the properties of the CPE/LiAA vulcanizates was investigated. The results showed that LiAA could improve the mechanical and water‐swelling properties of CPE/LiAA vulcanizates, providing a new approach to the preparation of water‐swelling elastomers. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 1804–1812, 2004