Preparation and properties of water‐swellable elastomer

A series of water‐swellable elastomers were prepared by blending chlorinated polyethylene (CPE) with poly(acrylic acid–acrylic amide) [P(AA–AM)]. The effect of component on its water‐absorbent properties such as degree of swelling, swelling ratio, and weight loss ratio was discussed. Mechanical behavior of blends was also investigated. The results indicate that swelling rate of CPE/P(AA–AM) was very quick; the blend reached its equilibrium state in only 30 min. The equilibrium swelling ratio increased with increasing amounts of water‐absorbent resin, the greater the amount of P(AA–AM), the higher the swelling degree. The effect of temperature on swelling ratio was very interesting, below 30°C, with an increase of temperature, the swelling ratio of blend increased, but above 30°C, with an increase of temperature, the swelling ratio decreased, indicating that this is a temperature‐sensitive water‐swellable elastomer. The effect of pH of solutions on the swelling behavior showed that water absorption of blends was heavily influenced by pH. The effect of different metal ions on the swelling behavior were also studied and the results showed that the absorption of blends was decreased dramatically with increasing the charge number of the cation, but was not influenced by radius and valence state of the anion. Owing to the compatibility of the amphiphilic graft copolymer (CPE‐g‐PEG), the equilibrium swelling ratio of the blends increased and the weight loss ratio decreased. Adding CPE‐g‐PEG can improve the mechanical behavior of blends. But too much grafted copolymer can worsen the tensile strength of blends. Tensile strength of blends decreased with an increase in P(AA‐AM). After absorbing water, the material's strength is greater than in the dry state. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 1719–1723, 2004     

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     

聚醚型吸水膨胀聚氨酯弹性体的合成

采用亲水性聚醚多元醇(PPE)与甲苯二异氰酸酯(TDI)反应的预聚体,与混合扩链剂制备了吸水膨胀聚氨酯弹性体。实验结果表明:当聚乙二醇醚(PEG)与聚丙二醇醚(PPG)的物质的量比为6∶4,PEG相对分子质量为2 000,预聚体中异氰酸酯基(—NCO)的质量分数为5.2%;采用混合扩链剂,且1、4-丁二醇与丙三醇的物质的量比为2∶1,增塑剂邻苯二甲酸二辛酯(DOP)的质量分数控制在8%时,制备的聚氨酯弹性体吸水膨胀率高,综合性能良好。     

Chlorohydrin water‐swellable rubber compatibilized by an amphiphilic graft copolymer. III. Effects of PEG and PSA on water‐swelling behavior

Chlorohydrin water‐swellable rubber—composed of chlorohydrin rubber (CHR), crosslinked polyacrylate (CPA), the amphiphilic compatibilizer poly(vinyl alcohol)‐g‐poly(butyl acrylate) (PVA‐g‐PBA), precipitated silica (PSA), and poly(ethylene glycol) (PEG)—was prepared. The dispersion of PEG in the blend was characterized by wide‐angle X‐ray diffraction (WAXD). The dependence of the water absorbing ratio by weight, the water‐swelling ratio by volume, and the percentage loss by weight on PEG and PSA contents were investigated. The effects of PEG and PSA on the second water‐swelling behaviors and long‐term water‐retention behaviors were also studied. Optimums for the water‐absorbing and water‐swelling abilities within the range of the experiment were obtained. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 79: 2509–2516, 2001     

Chlorohydrin water‐swellable rubber compatibilized by an amphiphilic graft copolymer. II. Effects of PVA‐g‐PBA and CPA on water‐swelling behaviors

A water‐swellable rubber (WSR), compatibilized by the amphiphilic graft copolymer, has been prepared by blending chlorohydrin rubber (CHR) with crosslinked polyacrylate (CPA), Poly(vinyl alcohol)‐g‐poly(butyl acrylate) (PVA‐g‐PBA), precipitated silica (PSA), and poly(ethylene glycol) (PEG). The WSR was characterized by scanning electron micrography (SEM). The dependence of the water‐absorbing ratio by weight, the water‐swelling ratio by volume, and the percentage loss by weight on PVA‐g‐PBA and crosslinked polyacrylate contents was investigated. The effect of PVA‐g‐PBA and crosslinked polyacrylate contents on second water‐swelling behaviors and long‐term water‐retention behaviors were also studied. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 74: 3145–3152, 1999     

Enhancing water swelling ability and mechanical properties of water‐swellable rubber by PAA/SBS nanofiber mats

Investigation of the potential use of nanofibers to reinforce composites has gained significance in many applications. In this article, the nanofiber mats of poly(acrylic acid) (PAA) and styrene–butadiene–styrene (SBS) triblock copolymer with composites structure were interweaved by double needle electrospinning process. The multiple nanofiber mats were added to conventional water‐swellable rubber (WSR). Improved mechanical and physical properties of WSR were obtained. Enhancement of the swellability of WSR + PAA/SBS nanofiber mats was derived from the PAA constituent absorbing water from the surface into the bulk and introducing random internal water channels between discontinuous superabsorbent polymers. The role of SBS nanofibers in the composite of WSR + PAA/SBS nanofiber mats was more related to the mechanical properties, where the breaking force of the composite increased to twice that of the conventional WSR. Interestingly, after immersion of the WSR + PAA/SBS nanofiber mats in water for 1 week, there was only a slight decrease in their mechanical properties of less than 5% compared to the dry state. The mechanisms and effects of the nanofiber mats in enhancing the mechanical and water swelling properties of WSR are also discussed. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 44213.     

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     

Biodegradation and swelling studies of gelatin‐grafted polyethylene

In this article, we report on biodegradation studies and the swelling/solubility behavior of gelatin‐grafted polyethylene (PE). The successful synthesis of graft copolymers of PE with gelatin was carried out with benzoyl peroxide as the radical initiator. Biodegradation studies of the grafted PE were carried out via a soil burial test (with and without the addition of urea). Percentage weight loss was studied as a function of time, and we observed that the percentage weight loss increased with time and was higher for urea‐enriched soil samples. Microanalysis of the soil containing the samples was carried out after a specified number of days. An increase in the colonies of microorganisms with increasing number of days was observed. This revealed that the microorganisms fed upon the grafted material, which led to an increase in the percentage weight loss. Hydrolysis of the samples, taken out from the soil after a specified number of days, revealed a continuous loss of weight with increasing number of days. The effect of the degradation of the grafted samples buried in soil and urea‐enriched soil on the growth of plants was studied, and we found that the plants grew normally in the soil containing the grafted material. Swelling studies were made in binary and ternary solvent systems comprising water–ethanol and water–ethanol–dimethyl sulfoxide, respectively, to study the maximum swelling and solubility of the grafted PE. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2008     

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     

Water‐swelling behavior of hydrophobic porous copolymer resins composed of two kinds of crosslinkers

Hydrophobic, but water‐swellable, porous copolymer resins composed of divinylbenzene (DVB) and ethylene glycol dimethacrylate (EGDM) or ethylene glycol diacrylate (EGDA) were prepared by using purified DVB (98.8%) in the presence of toluene as porogen. The EGDM/DVB resins thus obtained, whose polarity was nearly identical to that of the resins based on DVB and methyl methacrylate (MMA) at the same DVB levels, were water‐swellable by direct contact with water up to a DVB content of 64%, whereas the latter did not swell in water at any DVB levels. EGDA is also hydrophobic, but with a polarity greater than that of EGDM. As a result, the EGDA/DVB resins were more water swellable than EGDM/DVB resins, and could also be prepared as water‐swellable materials by using technical DVB (79.3%), besides the use of the purified DVB. All these results were explained on the basis of the network rigidity (crosslinking density) and the polymer polarity of the resins that were formed in the presence of a well‐solvating porogenic solvent. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 997–1004, 2004     

CPE-g-PEG在CPE/P(AA-AM)吸水膨胀弹性体中的增容作用

选择自制的吸水树脂丙烯酸/丙烯酰胺共聚物(P(AA-AM))与氯化聚乙烯(CPE)为共混原料,以CPE-g-PEG两亲性接枝共聚物为增容剂,机械共混制备了增容型吸水膨胀弹性体(WSE).对共混物的亚微形态、吸水膨胀特性以及力学性能进行了研究.TEM结果表明简单共混时,CPE/P(AA-AM)共混物试样的相容性差.添加CPE-g-PEG后CPE与P(AA-AM)相间有一定程度的连接.接枝物的加入,改善了共混试样的重复使用情况,降低了其质量损失率,提高了WSE的稳定性,改善了试样的力学性能,接枝物加入量为6份时,拉伸强度最大.     

Preparation and characterization of water‐swellable natural rubbers

Water‐swellable rubbers were prepared by dispersing the superabsorbent polymer particles, sodium polyacrylate particles, in natural rubber, and their water absorption properties were investigated. Sodium polyacrylate particles were synthesized using the inverse suspension polymerization technique, and their thermal and water absorption properties were characterized. The equilibrium water uptake in sodium polyacrylate particles was strongly dependent on both the salt concentration of aqueous media and crosslinking density of polymer. The dynamic and equilibrium water‐swelling behavior of the prepared rubbers were significantly affected by addition of carbon black, hydrophilic polymer, and coupling agent. Those effects were well explained by microphotographic morphologies obtained using a scanning electron microscope. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 115–121, 2001     

Graft modification of highly chlorinated polyethylene (HCPE) with methyl methacrylate by the mechanochemistry reaction. I. Synthesis and characterization

Highly chlorinated polyethylene‐graft‐methyl methacrylate (HCPE‐g‐MMA; HCPE with chlorine contents > 60%), obtained by a mechanochemistry reaction, is discussed in detail. A two‐roll mill was used in the process. The reaction conditions affecting the structure of HCPE‐g‐MMA copolymers were measured in terms of calculation of graft efficiency (GE), graft degree (GD), and copolymerization rate/homopolymerization rate (R_c/R_h) by ¹H‐NMR spectroscopy. Based on these results, it is concluded that the chlorine contents of HCPE, the additional amount of MMA, and the mechanochemistry reaction time all have impacts on the structure of the polymer. The results also confirm that grafting is very much favored by the mechanochemistry reaction. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 811–816, 2003     

Synthesis of highly swellable hydrogels of water‐soluble carboxymethyl chitosan and poly(ethylene glycol)

Highly swellable hydrogels were produced by crosslinking of high molecular weight carboxymethylated chitosan (CmCHT) with poly(ethylene glycol) (PEG) oligomers. The hydrogel swelling capacity could be controlled via the crosslinking density and ranged from 900% to 5600%. The hydrogels showed good homogeneity with a high interconnected porosity in the swollen state and with nanodomains rich in CmCHT and others rich in PEG diglycidyl ether. Oscillatory frequency sweep analysis showed a storage modulus of 27 kPa for the hydrogel with the highest crosslinking density, which together with the exhibited enzyme degradability with lysozyme at 59 days indicate that these hydrogels have potential use in delivery systems or soft tissue regeneration. © 2017 Society of Chemical Industry     

Graft copolymerization of sodium acrylate onto organophilic montmorillonites initiated by potassium diperiodatonickelate (IV) and application of graft copolymer in water‐superabsorbent

The graft copolymerization of sodium acrylate (SA) onto organophilic montmorillonites (OMMT) initiated by redox reaction of potassium diperiodatonickelate (IV) [Ni(IV)] with reactive groups on OMMT substrate was studied in alkaline medium. The grafting parameters have been investigated as a function of the ratio of monomer to OMMT, the concentration of initiator, temperature, and pH value. The structure of the graft copolymer (OMMT‐g‐PSA) was systematically characterized by Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), and scanning electron microscope (SEM). It was found that [Ni(IV)] belongs to a highly efficient initiator for graft copolymerization of SA onto OMMT via the redox iniation (grafting efficiency > 95%). Furthermore, the experimental results also showed that the graft copolymer gels synthesized under optimal condition exhibited a maximum water absorbency of 1104 g/g in distilled water and 111 g/g in 0.2 wt % NaCl solution, respectively, and its water retention ability is more than 91% after centrifugal separation for 2 h. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Synthesis and characterization of dextrin‐grafted polypropylene

We carried out the graft copolymerization of the water‐soluble natural polymer dextrin onto preirradiated polypropylene (PP) in an aqueous medium using benzoyl peroxide (BPO) as the radical initiator. PP was irradiated by γ rays from a Co⁶⁰ source at a constant dose rate of 3.40 kGy/h to introduce hydroperoxide linkages, which served as the sites for grafting. The graft copolymerization was studied as a function of different reaction parameters, and the maximum percentage grafting (P_g; 55%) of dextrin onto PP was obtained at optimum conditions of [BPO] = 5.165 × 10⁻² mol/L, temperature = 60°C in 120 min with 15 mL of water. Different grafting parameters, such as the percentage apparent grafting, percentage grafting, and percentage true grafting have been evaluated. The graft copolymers were characterized by Fourier transform infrared spectroscopy, thermogravimetric analysis, and scanning electron microscopy. Swelling studies were carried out in pure, binary, ternary, and quaternary solvent systems composed of water, ethanol (EtOH), dimethyl sulfoxide (DMSO), and N,N‐dimethylformamide (DMF) at different ratios. The maximum swelling percentage PP‐g‐dextrin (both composite and true graft) was observed in pure DMSO and DMF followed by EtOH and water. Water‐retention studies of PP and PP‐g‐dextrin (both composite and true graft) were investigated at different time periods, temperatures, and pH values. The maximum percentage water retention of PP‐g‐dextrin (composite, 124%) was observed at 8 h and 50°C in a neutral medium (pH 7). © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Preparation and applicability of functionalized polyethylene with an ethylene/1,7‐octadiene copolymer

The copolymerization of ethylene and 1,7‐octadiene was carried out to synthesize polyethylene with unreacted vinyl groups. The prepared copolymer [poly (ethylene‐co‐1,7‐octadiene) (PEOD)] was epoxidized with peracetic acid, m‐chloroperbenzoic acid, or formic acid/H₂O₂. Of these, peracetic acid gave the best results. Epoxidized PEOD was subjected to a reaction with 2‐mercaptobenzimidazole and poly(L ‐lactic acid). The bromination of PEOD was also performed in the presence of a Br₂/HBr solution at room temperature. The brominated poly(ethylene‐co‐1,7‐octadiene) (PEOD‐Br) was used as a macroinitiator for atom transfer radical polymerization. The polymerization of styrene, butyl methacrylate, and glycidyl methacrylate was performed in bulk or solution at 120°C with a PEOD‐Br/CuBr/2,2′‐dipyridyl initiator system. The thermal properties of the graft copolymers and the efficiency of the graft polymerization were investigated. These graft copolymers have potential applications as interfacial modifiers. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Study on the properties of polyethylene–octene elastomer/wood flour blends

In the present study, the properties of metallocene polyethylene–octene elastomer (POE) and wood flour (WF) blends were examined by Fourier transform infrared (FTIR) spectroscopy, differential scanning calorimetry (DSC), an Instron mechanical tester, and scanning electron microscopy (SEM). The results showed that the mechanical properties of POE were obviously lowered, due to the poor compatibility between the two phases, when it was blended with WFs. A fine dispersion and homogeneity of WF in the polymer matrix could be obtained when acrylic acid‐grafted POE (POE‐g‐AA) was used to replace POE for manufacture of the blends. This better dispersion is due to the formation of branched and crosslinked macromolecules since the POE‐g‐AA copolymer had carboxyl groups to react with the hydroxyls. This is reflected in the mechanical and thermal properties of the blends. In comparison with a pure POE/WF blend, the increase in tensile strength at break was remarkable for the POE‐g‐AA/WF blend. The POE‐g‐AA/WF blends are more easily processed than are the POE/WF blends, since the former had a lower melt viscosity than that of the latter. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 1919–1924, 2003     

Synthesis,swelling behaviors,and slow‐release characteristics of a guar gum‐g‐poly(sodium acrylate)/sodium humate superabsorbent

Superabsorbents used in agricultural and ecological projects with low‐cost, slow‐release fertilizers and environmentally friendly characteristics have been extensively studied. The use of a natural polymer as the matrix and then further polymerization with some functional material has become the preferred method. In this work, with natural guar gum (GG), partially neutralized acrylic acid, and sodium humate (SH) as the raw materials, ammonium persulfate as the initiator, and N,N′‐methylenebisacrylamide (MBA) as the crosslinker, GG‐g‐poly(sodium acrylate) (PNaA)/SH superabsorbents were synthesized through a solution polymerization reaction and were characterized with Fourier transform infrared spectroscopy, scanning electron microscopy, and thermogravimetric analysis. The effects of the SH content and MBA concentration on the water absorbency were investigated. The results showed that the introduction of SH into the GG‐g‐PNaA system could improve the water absorbency, swelling rate, pH‐resistant property, and reswelling capability, and the superabsorbent containing 15 wt % SH had the highest water absorbency of 532 g/g of sample in distilled water and 62 g/g of sample in a 0.9 wt % NaCl solution. The slow release in water and water retention in sandy soil tests revealed that the superabsorbent could act as a fertilizer as well as an effective water‐saving material for agricultural applications. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Temperature/pH‐sensitive comb‐type graft hydrogels composed of chitosan and poly(N‐isopropylacrylamide)

Comb‐type graft hydrogels, composed of chitosan and poly(N‐isopropylacrylamide) (PNIPAAm), were prepared to manifest rapid temperature and pH sensitivity. Instead of directly grafting the NIPAAm monomer onto the chitosan chain, semitelechelic PNIPAAm with carboxyl end group was synthesized by radical polymerization using 3‐mercaptopropionic acid as the chain‐transfer agent, and was grafted onto chitosan having amino groups. The comb‐type hydrogels were prepared with two different graft yields and grafting regions, such as surface‐ and bulk‐grafting, and then compared with a chitosan hydrogel. The synthesis of telechelic PNIPAAm and the formation of amide group were confirmed by using FTIR spectroscopy and gel permeation chromatography. Results from the water state and thermal stability revealed that the introduction of the PNIPAAm side chain disturbed the ordered arrangement of the chitosan molecule, resulting in an increase in the equilibrium water content. Comb‐type graft hydrogels showed rapid temperature and pH sensitivity because of the free‐ended PNIPAAm attached to the chitosan main chain and the chitosan amino group itself, respectively. In particular, the surface graft hydrogel maintained its dimension at low pH, although the chitosan main chain was not crosslinked, whereas chitosan and bulk graft hydrogel were dissolved as a result of the coating effect of pH‐independent PNIPAAm. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 2612–2620, 2004