Mechanical Strengths of Hydrogels of Poly(N,N‐Dimethylacrylamide)/Alginate with IPN and of Poly(N,N‐Dimethylacrylamide)/Chitosan with Semi‐IPN Microstructures

Tough hydrogels receive continuous attention because of their promising applications in many fields. Herein, tough hydrogels of poly (N,N‐dimethylacrylamide) (PDMAA)/alginate (SA) are prepared, with interpenetrating network (IPN) and of PDMAA/chitosan (CS) with semi‐IPN microstructure, respectively. The toughening of the hydrogel by incorporating natural polymers is studied by compressing tests and dynamic mechanical analyses. Moreover, cyclic load–unload compressing of the two types of hydrogels are performed at low strains and under relatively high strains, in order to compare their strength and anti‐fatigue properties. The results indicate that the mechanical strength can be markedly improved upon addition of the natural polymers, and the IPN hydrogel of PDMAA/SA reveals much higher mechanical performances but is less stable. However, the semi‐IPN hydrogel of PDMAA/CS displays excellent anti‐fatigue stability, but with relatively low strength. Swelling tests, scanning electron microscopy, and Fourier transform infrared spectroscopy are carried out to study the microstructures of the hydrogels, which are carefully analyzed to understand the difference in mechanical performances of those hydrogels. The results suggest that the presence of sacrificial unit and higher chain density in the IPN are helpful for toughening hydrogels, while the semi‐IPN network is beneficial to improve the energy dissipation efficiency.     

Rigid interpenetrating polymer network foams prepared from a rosin-based polyurethane and an epoxy resin

A series of rigid interpenetrating polymer network (IPN) foams, based on a rosin-based polyurethane and an epoxy resin, were prepared by a simultaneous polymerization technique. The changes in the chemical structure, dynamic mechanical properties, and morphology of the rigid IPN foams were investigated by Fourier transform infrared (FTIR) spectroscopy, dynamic mechanical thermal analysis, and scanning electron microscopy. The FTIR analysis showed clearly that the cure rate of the rosin-based rigid polyurethane foam and the epoxy resin were different and, as a result, these two networks formed sequentially in the final rigid IPN foams. All of the rigid IPN foams exhibited a single, broad glass transition that shifted to lower temperature as the epoxy resin content increased. The experimental composition dependence of T_g's of the rigid IPN foams showed slight positive deviation from the Fox equation for homogeneous polymer systems. No phase separation was observed from the scanning electron microscopy investigation. It could be concluded that these two component networks were compatible in the final rigid IPN foams. This compatibility could be attributed to a graft structure in the polyurethane and the epoxy resin networks arising from the reaction of the hydroxyl groups of the epoxy resin with the isocyanate groups of MDI, and from the reaction of the hydroxyl groups of the polyols with the epoxide groups of the epoxy resin, as suggested by FTIR analysis. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 69: 271–281, 1998     

Poly(ethylene oxide)/polybutadiene based IPNs synthesis and characterization

Interpenetrating polymer networks (IPNs) were prepared from hydroxytelechelic polybutadiene (HTPB) and poly(ethylene oxide) (PEO) via an in situ process. The PEO network was obtained by free radical copolymerization of poly(ethylene glycol) methacrylate and dimethacrylate. Addition reactions between HTPB and a pluri-isocyanate cross-linker (Desmodur^® N3300) led to the HTPB network. Polymerization kinetics were followed by Fourier transform spectroscopy in the near and middle infrared. Mechanical properties and the IPN morphology were investigated by dynamic mechanical analysis and transmission electron microscopy. The relation between the formation rates of the two networks and the IPN final morphology is discussed.     

Properties and Aggregate Structure of Unsaturated Polyester/Phenolic Resin Blends

In this study, unsaturated polyester resin (UP) is blended with resole type phenolic resin, co-crosslinking process performed and the resin blends show miscibility and interpenetration network (IPN) structure. Differential scanning calorimetry (DSC) and dynamic mechanical analysis (DMA) are employed to examine the aggregate structure of crosslinked network of the UP/phenolic resin blend. Tensile fractured sections of the resin blends are observed using scanning electronic microscopy (SEM) to shed light on their miscibility. Tensile and flexural tests were also conducted to examine the mechanical properties of the UP/phenolic resin blends. The results show that UP20/Ph80 and UP40/Ph60 resin blends have well-formed Interpenetrating Network (IPN) structures while phase separation is observed for UP60/Ph40 resin blend. Finally, thermal cure of UP80/Ph20 resin blend is incomplete, thus showing immiscibility. The mechanical properties of all resin blends at different mixing proportions deviate from a linear relationship and show a concave curve, indicating the non-additive effect of blending.     

Improvement of thermomechanical properties of a DGEBS/DDS system blended with a novel thermoplastic copolymer by realization of a semi‐IPN network

In this article we present the results of a study on the properties of a blend containing a 40:60 amine‐ended copolymer, poly(ether sulfone)—poly(ether ether sulfone), with a system composed of diglycidyl ether of biphenol S and 4,4′‐diaminodiphenyl sulfone (4,4′‐DDS). Five formulations, which varied in amounts of modifier, were characterized through dynamic thermal mechanical analysis and fracture mechanics studies. The morphology of the blends was studied by transmission electron microscopy (TEM). The addition of thermoplastics enhanced the toughness of the system, resulting in an increase in the glass‐transition temperature as a function of the amount of thermoplastics. No phase‐separated morphology was detected by TEM analysis, leading to the conclusion that the formation of a homogeneous semi‐IPN network occurred between the thermoplastics and the thermoset. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 3021–3025, 2003     

Mechanical and morphological study of polyurethane/polystyrene interpenetrating polymer networks containing ionic groups

The viscoelastic and mechanical properties and the morphology of polyurethane (PUR)/ olystyrene (PS) interpenetrating polymer networks (IPNs) containing ionic groups have been investigated. Dynamic mechanical thermal analysis (DMTA) revealed a pronounced change in the viscoelastic properties upon the introduction of ionic groups. For the 70 : 30 and 60 : 40 PUR/PS IPN compositions, the DMTA data changed from a dominant PUR to a dominant PS loss factor peak. Higher intertransition loss factor values indicated a significant improvement of IPN component mixing with increasing ionic content. The stress at break values increased only moderately, whereas sharp rises in Young's modulus and hardness values were found at 2 wt % ionic groups. At the same time, the strain at break values decreased by half. Scanning and transmission electron microscopy (TEM) indicated a grossly phase-separated morphology for the 70 : 30 PUR/PS IPN without ionic groups. With increasing methacrylic acid (MAA) content, the PS phase domain sizes decreased. At 2 wt % of ionic groups, a TEM micrograph showed interconnected PS phase domains resembling a network structure. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 67:1973–1985, 1998     

Cure kinetics and physical properties of dicyanate/polyetherimide semi‐IPNs

The curing behavior and physical properties of dicyanate/polyetherimide (PEI) semi‐interpenetrating polymer network (IPN) systems were investigated. Differential scanning calorimetry (DSC) was used to study the curing behavior of the dicyanate/PEI semi‐IPN systems. The curing rate of the semi‐IPN system decreased as the PEI content increased. An autocatalytic reaction mechanism can describe well the curing kinetics of the semi‐IPN systems. The reaction kinetic parameters were determined by fitting DSC conversion data to the kinetic equation. The glass transition temperature of the semi‐IPNs decreased with increasing PEI content. Two glass transitions due to phase‐separated morphology were observed for the semi‐IPN containing over 15 phr (parts per hundred parts of dicyanate resin) PEI. The thermal stability and dynamic mechanical properties of the semi‐IPNs were measured by thermal analysis.     

Poly(vinyl acetate)/polyacrylate semi‐interpenetrating polymer networks. II. Thermal,mechanical, and morphological characterization

The thermal, dynamic mechanical, and mechanical properties and morphology of two series of semi‐interpenetrating polymer networks (s‐IPNs) based on linear poly(vinyl acetate) (PVAc) and a crosslinked n‐butyl acrylate/1,6‐hexanediol diacrylate copolymer were investigated. The s‐IPN composition was varied with different monoacrylate/diacrylate monomer ratios and PVAc concentrations. The crosslinking density deeply affected the thermal behavior. The results showed that a more densely crosslinked acrylate network promoted phase mixing and a more homogeneous structure. The variation in the linear polymer concentration influenced both the morphology and mechanical properties. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Synergetic Effects of Graphene Oxide and Clay on the Microstructure and Properties of HIPS/Graphene Oxide/Clay Nanocomposites

In this paper, double-network structure nanocomposite with improved mechanical and thermal properties were prepared using high-impact polystyrene as a matrix phase, clay and graphene oxide as effective reinforcing fillers through a facile solution intercalation method. The structure and morphology of nanocomposites were characterized by transmission electron microscopy, scanning electron microscopy, X-ray diffraction analysis, and the synergetic effects of clay and graphene oxide on the final properties were investigated using tensile, dynamic mechanical thermal analysis (DMTA) and thermogravimetric analysis (TGA) analysis. Mechanical analysis showed that the combination of graphene oxide and clay exerted a favorable synergistic effect on the tensile modulus and the yield strength of the ternary composite that are greatly improved as compared with neat high-impact polystyrene, high-impact polystyrene/graphene oxide, and high-impact polystyrene/clay binary composites due to the double-network structure formation between the nanofillers as confirmed by the direct morphological observations using transmission electron microscopy and scanning electron microscopy analysis. The viscoelastic behavior showed that storage modulus of ternary composite significantly improvement over than that of the pure matrix, high-impact polystyrene/graphene oxide and high-impact polystyrene/clay while network structure made. TGA and DMTA measurements also demonstrated that thermal stability of high-impact polystyrene matrix modified by graphene oxide and clay slightly enhanced during the creation of dual network structure of graphene oxide and clay. Our data suggest a potential application for the combination of graphene oxide and clay in graphene-based composite materials.     

Structure and adhesive properties of the RFL‐coated continuous basalt fiber cord/rubber interface

The relationships between the structure of the resorcinol‐formaldehyde‐latex (RFL) layer, static adhesion, and interfacial fatigue properties between the RFL‐coated continuous basalt fiber (CBF) cord and a rubber matrix were studied using films prepared from RFL systems with various formulas and H samples prepared with RFL‐coated CBF cord and NR/SBR matrix. Thermomechanical analysis and tensile testing of the RFL films were carried out using a dynamic mechanical analyzer (DMA). The H pull‐out force and fatigue properties were tested using a universal testing machine and an MTS, respectively. The interfacial fatigue life of the RFL‐coated CBF cord/rubber samples exhibited different variation regularity from the variation of the H pull‐out force as F/R and L/RF changed. The static adhesion reflected the connection strength between the cord and the rubber matrix, whereas the characteristics and the properties of the RFL layer played a decisive role in determining the damage rate of the adhesion. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 44353.     

混合大二醇基聚氨酯弹性体/环氧树脂互穿网络聚合物的研究

以α,ω-双(γ-羟丙基)聚二甲基硅氧烷(BHPDMS)和聚氧四甲基二醇(PHMO)混合大二醇作为软链段,首先通过两步溶液聚合法合成了-NCO封端的混合大二醇基聚氨酯(PU)弹性体预聚物(PUT);然后以PUT和环氧树脂(EP)预聚物为原料、1,3-双(γ-氨丙基)-1,1,3,3-四甲基二硅氧烷(BATS)为交联剂,采用同步溶液聚合法合成了PUT/EP互穿聚合物网络(PUT/EP I PN)。使用傅里叶红外光谱(FT-I R)法、动力学分析(DMA)法和扫描电子显微镜(SEM)法,对PUT和PUT/EP I PN进行分析和表征,并对其力学性能和表面疏水性进行测试。实验结果表明,PUT/EP I PN中不存在宏观相分离状态,仅发生微观相分离状态;当PUT/EP I PN中w(PUT)=50%时,PUT/EP I PN具有优异的综合力学性能和表面疏水性。     

双酚F环氧/聚甲基丙烯酸甲酯互穿网络的研究

合成了双酚F环氧树脂(BPFER),测定了其环氧值。用同步法制备了不同配比的双酚F环氧树脂/聚甲基丙烯酸甲酯互穿聚合物网络(BPFER/PMMAIPN),讨论了配比对IPN的力学性能和热性能的影响。用透射电子显微镜对IPN进行了形态分析。     

Functionalized elastomeric compatibilizer in PA 6/PP blends and binary interactions between compatibilizer and polymer

Superior impact properties were obtained when maleic anhydride grafted styrene ethylene/butylene styrene block copolymer (SEBS-g-MAH) was used as a compatibilizer in blends of polyamide 6 (PA 6) and isotactic polypropylene (PP), where polyamide was the majority phase and polypropylene the minority phase. The optimum impact properties were achieved when the weight relation PA:PP was 80:20 and 10 wt% SEBS-g-MAH was added. The blend morphology was systematically investigated. Transmission electron microscopy (TEM) indicated that the compatibilizer forms a cellular structure in the PA phase in addition to acting as an interfacial agent between the two polymer phases. In this cellular-like morphology the compatibilizer appears to form the continuous phase, while polyamide and polypropylene form separate dispersions. In microscopy, PA appeared as a fine dispersion and PP as a coarse dispersion. The mechanical properties indicated that in fact PA, too, is continuous, and the blend can be interpreted as possessing a modified semi-interpenetrating network (IPN) structure with separate secondary dispersion of PP. The coarser PP dispersion plays an essential role in impact modification. Binary blends of the compatibilizer and one blend component were also investigated separately. The same cellular structure was observed in the binary PA/SEBS-g-MAH blends, and SEBS-g-MAH again appeared to form the continuous phase when the elastomer concentration was at least 10 to 20 wt%. By contrast, in PP/SEBS-g-MAH only conventional dispersion of elastomeric SEBS-g-MAH was observed up to 40 wt% elastomer. Impact strength was improved and the elastic modulus was lowered in both PA/SEBS-g-MAH and PP/SEBS-g-MAH blends when the elastomer content was increased. The changes in modulus indicate that the semi-IPN-like structure is formed in the binary PA/SEBS-g-MAH blends as well as in the ternary structure.     

Synthesis,characterization, mechanical properties and biocompatibility of interpenetrating polymer network–super‐porous hydrogel containing sodium alginate

In this investigation an interpenetrating polymer network–superporous hydrogel containing sodium alginate (IPN‐SPH_Alg) was synthesized. The morphology of the polymer was characterized using scanning electron microscopy, light images and porosity, and the polymer was further examined by swelling ratio, mechanical strength and biocompatibility. The results indicated that the IPN‐SPH_Alg possessed both large numbers of interconnected pores and an interpenetrating network. The swelling ratio of IPN‐SPH_Alg was lower than that of the superporous hydrogel (SPH) and it decreased as the sodium alginate/monomer ratio increased. The IPN‐SPH_Alg exhibited pH responsiveness and salt‐sensitive properties. Compared to SPH and SPH composites, the mechanical strength of IPN‐SPH_Alg was significantly enhanced. Thiazolyl blue assay on AD293 cells, in situ lactate dehydrogenase assay and morphological study of rat intestine showed that the polymer induced no significant cell or mucosal damage. The fast swelling, good mechanical properties, pH sensitivity and biocompatibility of the IPN‐SPH_Alg suggested it as a potential candidate in the field of drug‐delivery systems. Copyright © 2007 Society of Chemical Industry     

Tribological mechanism improving the wear resistance of polyurethane/epoxy interpenetrating polymer network via nanodiamond hybridization

The excellent synergistic effect of physical/mechanical properties of polyurethane/epoxy (PU/EP) interpenetrating polymer network (IPN) and the validity of nanofilling have one potential to improve the wear resistance of polymeric materials. With the aim of practical application, PU/EP IPN nanocomposites are prepared with nanodiamond (ND) as a reinforcing additive. Results showed the uniform thermal stability and the excellent compatibility between PU and EP in ND‐hybridized PU/EP IPN. Simultaneously, ND particles work as crosslinked points improving the physical/mechanical properties of ND‐hybridized PU/EP IPN, especially the wear resistance. The measurement of tribological property and the scanning electron microscope indicated that the wear resistance is able to be improved a lot by the formation of IPN and by the addition of ND. Consequently, the tribological mechanism of PU/EP IPN nanocomposites comes into being. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40244.     

Morphological structure and mechanical properties of polyurethane modified with methyl methacrylate

Three kinds of polyurethane-poly(methyl methacrylate) (PU–PMMA), that is, linear polymer, block copolymer, and interpenetrating polymer network (IPN), were synthesized by a simultaneous polymerization process, respectively. The effects of several factors such as ultraviolet (UV) setting, heat setting, chemical composition, and physical structure on the morphological structure and mechanical properties of polymers were studied by scanning electron micrograph, dynamic mechanical loss spectrum, and mechanical tests. The results show that PU–PMMA is a partially compatible system with a two-phase structure; the linear polymer has the highest elongation at break, and IPN has the strongest tensile strength, while the block copolymer has poor mechanical properties. In addition, the UV setting block copolymer and IPN system, with regular microphase domain structures, have higher tensile strength and elongation at break than those of heat setting polymers. With MMA content and hard segment in PU increasing, the tensile strength increases, and the elongation decreases. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 68: 1363–1369, 1998     

Synthesis and characterization of nanocellulose reinforced full‐interpenetrating polymer network based on poly(vinyl alcohol) and polyacrylamide (both crosslinked) composite films

An interpenetrating polymer network (IPN) is a novel blend of two polymers at least one of which is synthesized or crosslinked in the immediate presence of the other so that there is the least possibility of any gross phase separation. Full‐IPNs, prepared from poly(vinyl alcohol) and polyacrylamide, have shown superior performances over the conventional individual polymers. The ranges of applications have grown rapidly for such class of materials. Cellulose nanoparticles extracted from sugarcane bagasse in‐house are used to reinforce this PVA/PAAm (80:20) full‐IPN in different proportions during the synthesis of IPN. The characteristics of this new series of IPN composite materials have been evaluated by Fourier transform infrared spectroscopic analysis, mechanical, thermal (thermogravimetric analysis and differential scanning calorimetry), and scanning electron microscopy techniques. A loading of 5 wt% of nanocellulose lead to the highest tensile strength amongst the different IPN composite films. Although the non‐reinforced full‐IPN and the various reinforced composites with nanocelluloses are almost identical in their thermal stability, they prove to be much superior compared to the neat polymers. POLYM. COMPOS., 38:1720–1731, 2017. © 2015 Society of Plastics Engineers     

Polyisobutene/polycyclohexyl methacrylate interpenetrating polymer networks

Interpenetrating polymer networks (IPNs) combining polyisobutene (PIB) and poly(cyclohexyl methacrylate) (PCHMA) networks were prepared using an in situ strategy. PIB networks were formed by alcohol-isocyanate addition between the hydroxyl end groups of telechelic dihydroxypolyisobutene and an isocyanate cross-linker, catalyzed by dibutyltindilaurate (DBTDL). PCHMA networks were obtained from free-radical copolymerization of cyclohexyl methacrylate (CHMA) with ethylene glycol bismethacrylate (EGDM) in the presence of dicyclohexyl peroxydicarbonate (DCPD) as the initiator. The network formations into the IPN architecture were followed by FTIR spectroscopy. In a large composition range, transparent IPNs exhibit two mechanical relaxation temperatures as determined by dynamic mechanical thermal analysis (DMTA), corresponding to those of a PIB enriched phase and of one interpenetrating phase containing the PCHMA network. This morphology was confirmed by IPN surface analysis by AFM. As expected, mechanical properties of PIB networks are improved by the presence of PCHMA network in such IPN architectures.     

Curing and mechanical properties of dicyanate/poly(ether sulfone) semi‐interpenetrating polymer networks

Semi‐interpenetrating polymer networks (semi‐IPNs) composed of a dicyanate resin and a poly(ether sulfone) (PES) were prepared, and their curing behavior and mechanical properties were investigated. The curing behavior of the dicyanate/PES semi‐IPN systems catalyzed by an organic metal salt was analyzed. Differential scanning calorimetry was used to study the curing behavior of the semi‐IPN systems. The curing rate of the semi‐IPN systems decreased as the PES content increased. An autocatalytic reaction mechanism was used to analyze the curing reaction of the semi‐IPN systems. The glass‐transition temperature of the semi‐IPNs decreased with increasing PES content. The thermal decomposition behavior of the semi‐IPNs was investigated. The morphology of the semi‐IPNs was investigated with scanning electron microscopy. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 87: 1079–1084, 2003     

Thermal characterization and morphological study of polyphenylene sulfide–polycarbonate blends

The thermal behavior and phase morphology of binary blends of poly(phenylene sulfide) (PPS) with polycarbonate (PC) have been investigated. Differential scanning calorimetry and dynamic mechanical thermal analysis indicate the blends are immiscible, but the glass transition temperature of PC in the blends was found to be decreased due to the degradation of the PC. The PC degradation was investigated by measuring the molecular weight of PC extracted from the blends. Rheological properties of the blends were also studied using a rheodynamic spectrometer. An inversion of the phase morphology was observed from the scanning electron microscopy and dynamic mechanical thermal analysis. The increase of crystallinity of the PPS in the blends was found from a DSC study.