Sequential interpenetrating polymer network of poly(ethyl methacrylate) and carboxylated nitrile rubber: Dynamic mechanical analysis and morphology

An interpenetrating polymer network (IPN) based on poly(ethyl methacrylate) (PEMA) and carboxylated nitrile rubber was synthesized. Peroxide crosslinked XNBR was swollen in ethyl methacrylate containing benzoyl peroxide as initiator and tetraethylene glycol dimethacrylate as crosslinking agent. A full and sequential IPN is formed by the two independently crosslinked phases of XNBR and PEMA. Dynamic mechanical analysis of the 50/50 XNBR/PEMA IPN shows a single, broad peak whereas a 50/50 blend shows two distinct peaks, indicating the pinning down of a microheterogeneous structure during the IPN formation rather that macrophase separation as in blends. SEM analysis confirms the development of a cocontinuous intimate structure of the IPN. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 96: 1487–1491, 2005     

Poly(ether urethane)/poly(ethyl methacrylate) IPNs with high damping characteristics: The influence of the crosslink density in both networks

Interpenetrating polymer networks (IPNs) with a controlled degree of microphase separation were synthesized from a poly(ether urethane) (PUR) and poly(ethyl methacrylate) (PEMA). The influence of the crosslink density of both networks was investigated in the 70:30 PUR/PEMA IPN. The extent of damping was evaluated by dynamic mechanical thermal analysis. Mechanical properties were studied using tensile testing and hardness measure-ments. Control of crosslinking was successful in tailoring the damping profile. Higher crosslinking in the first-formed network (polyurethane) seemed to increase slightly the area under the linear loss modulus curve, LA, whereas no influence was obvious when changing the crosslink density in the second network. TGA studies revealed improved thermal properties for the IPNs with a higher crosslink density in the PUR network. TEM micrographs confirmed a finer morphology for the materials with a higher crosslink density in the PUR, whereas increasing the crosslink density in the PEMA network resulted in a decrease of phase mixing. © 1996 John Wiley & Sons, Inc.     

Molecular demixing in poly[cross-(ethyl acrylete)]-inter-poly[cross-(methyl methacrylate)] interpenetrating polymer networks brought about by selective decrosslinking and annealing

The extent of molecular demixing of poly[cross-(ethyl acrylate)]-inter-poly[cross-(methyl methacrylate)] interpenetrating polymer networks (PEA/PMMA IPNs), of mid-range composition was investigated by decrosslinking and/or annealing using dynamic mechanical spectroscopy. A single broad transition characteristic of extensive but incomplete molecular mixing was observed for the PEA/PMMA IPN. The presence of crosslinking in both phases of an IPN enhances the mutual miscibility of the polymers. Through the use of a labile crosslinker, acrylic acid anhydride (AAA), polymer networks may be decross-linked, allowing the chains to separate and form two distinct phases. Annealing further sharpens the transitions, and phase separation becomes most pronounced when decrosslinking is followed by annealing.     

Mechanical performance of vinyl ester—polyurethane interpenetrating polymer network composites

In this study, a carbon fiber/vinyl ester-polyurethane interpenetrating polymer network (IPN) laminate composite was fabricated and characterized for the first time. The IPN matrix, consisting of a commercially available vinyl ester and polyurethane, was synthesized via a sequential method with vinyl ester as the rigid phase and polyurethane as the flexible phase. Good compatibility between the two phases in the matrix was achieved and confirmed via differential scanning calorimetry and dynamic mechanical analysis. The thermomechanical response of the IPN matrix was compared with that of an unmodified vinyl ester resin. The presence of the more ductile polyurethane in the IPN matrix depressed the glass transition temperature (from 94 to 84°C), but also served to improve damping response at all frequencies studied. Tensile and flexural tests were performed on the carbon fiber/IPN and carbon fiber/vinyl ester composites to determine their mechanical response. The IPN composite exhibited lower tensile properties than the vinyl ester composite. However, its flexural properties were on par with those of the vinyl ester composite.     

互穿聚合物网络技术对丁羟推进剂粘合剂体系性能的改善

通过互穿聚合物网络(IPN)技术,在原有丁羟推进剂粘合剂体系中添加甲基丙烯酸B酯作为塑料相,合成了3个系列的胶片。测定了预聚物的动态黏度,发现改性的预聚物黏度在反应初期明显低于原有预聚物黏度,丙烯酸酯的加入明显改善了其加工工艺性能;对胶片力学性能的测试则表明,拉伸强度可达到1.432 MPa,断裂伸长率达到576.614%。可见,丙烯酸酯对胶片力学性能的改善起到了显著的作用。玻璃化转变温度的测定表征了IPN体系的相分离程度。     

Solid‐state structure and properties of poly(ethyl methacrylate)/phenoxy blends

Poly(ethyl methacrylate)/poly(hydroxy ether of bisphenol A) (PEMA/phenoxy or PEMA/Ph) blends were obtained by melt mixing to investigate their solid‐state characteristics and mechanical properties. The slight structural change from poly(methyl methacrylate) (PMMA) to PEMA spoiled the miscibility of PMMA/Ph blends leading to biphasic PEMA/Ph blends. It is proposed that an antiplasticizer in the case of PEMA, and a low molecular weight component in the case of Ph, as well as minor amounts of each component, migrated to the other phase during melt mixing. The mechanical properties of the blends were good, given that they were biphasic. The modulus of elasticity and yield stress values were found to be additive. Despite the below‐additivity ductility values, ductile behavior was observed. The minor amount of the other component in each phase, and the migration of the antiplasticizer of PEMA, are proposed as the main causes of the observed mechanical properties. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 74: 1539–1546, 1999     

Synthesis and characterization of sequential interpenetrating polymer networks of novolac resin and poly(ethyl acrylate)

Interpenetrating polymer networks (IPN) of Novolac/poly(ethyl acrylate) have been prepared via in situ sequential technique of IPN formation. Both full and semi IPNs were characterized with respect to their mechanical properties that is, ultimate tensile strength (UTS), percentage elongation at break, modulus, and toughness. Physical properties of these were evaluated in terms of hardness, specific gravity, and crosslink density. Thermal behavior was studied by differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). The morphological features were observed by an optical microscope. There was a gradual decrease in modulus and UTS, with consequent increases in elongation at break and toughness for both types of IPNs with increasing proportions of PEA. An inward shift and lowering (with respect to pure phenolic resin) of the glass transition temperatures of the IPNs with increasing proportions of PEA were observed, thus, indicating a plasticizing influence of PEA on the rigid, brittle, and hard matrix of crosslinked phenolic resin. The TGA thermograms exhibit two‐step degradation patterns. An apparent increase in thermal stability at the initial stages, particularly, at lower temperature regions, was followed by a substantial decrease in thermal stability at the higher temperature region under study. As expected, a gradual decrease in specific gravity and hardness values was observed with increase in PEA incorporation in the IPNs. A steady decrease in crosslink densities with increase in PEA incorporation was quite evident. The surface morphology as revealed by optical microscope clearly indicates two‐phase structures in all the full and semi IPNs, irrespective of acrylic content. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci, 2006     

Polysiloxane-Cellulose acetate butyrate cellulose interpenetrating polymers networks close to true IPNs on a large composition range. Part II

Interpenetrating polymer networks combining cellulose acetate butyrate (CAB) and α,ω-divinyl-polydimethylsiloxane (PDMS) in different weight proportions have been synthesized. The synthesis involves a one pot-one shot process in which all components are first mixed together. For each composition, the relative CAB and PDMS network formation rates are adjusted through the concentration of DBTDL used as CAB network formation catalyst. Thus, the chemically independent networks are formed quasi-simultaneously in order to avoid phase separation. The CAB cross-linking density effect on the PDMS/CAB IPN mechanical properties has also been particularly studied. All synthesized IPNs are transparent and only one mechanical relaxation temperature lying between those of the single CAB and PDMS networks is observed by DMTA analysis. These results show that the networks are correctly interpenetrated and no phase separation is observed at the DMTA level. Some mechanical properties of the PDMS network are significantly improved in this IPN combination and their stress-strain behavior has highlighted a synergistic effect arising from the IPN architecture. Thus, these IPNs exhibit many characteristics, which would allow defining them as close to ‘true’ IPNs.     

Studies on engineering properties of PVC–PMMA semi‐interpenetrating polymer networks

Semi1 and semi2 interpenetrating polymer networks (IPNs) of PVC and in situ formed PMMA have been synthesized using diallyl phthalate and ethylene glycol dimethacrylate as the crosslinkers of PVC and PMMA, respectively. These two types of IPNs have been compared w.r.t their physical, mechanical, and thermal properties and an endeavor has been made to find a correlation of these properties with the morphology generated in these systems. The semi1 IPNs displayed a decrease in their mechanical parameters and the physical properties as well, while in contrast, the semi2 IPNs exhibited a marginal increase in the corresponding values after an initial drop upto about 15% of crosslinked PMMA incorporation when compared to the crosslinked PVC in the case of semi1 IPN and linear PVC in the case of semi2 IPN. The various samples of semi1 and semi2 IPNs showed a two‐stage degradation typical of PVC, while confirming the increased stability with the samples having higher percentages of PMMA. The influence of crosslinking of the major matrix in semi1 IPN was almost counterbalanced by the influence of crosslinking in the dispersed PMMA phase in the case of semi2 IPN. The softening characteristics as detected by the extent of penetration of the probe, as has been detected by thermomechanical analysis, are in conformity with their mechanicals. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 1725–1735, 2005     

Interpenetrating polymer network of blocked polyurethane and phenolic resin. I. Synthesis,morphology, and mechanical properties

Interpenetrating polymer networks (IPNs) based on blocked polyurethane (BPU)/phenolic (PF) were prepared using simultaneous polymerization method. The IPN was prepared from BPU prepolymer with m‐xylylenediamine as the chain extender and PF prepolymer using p‐toluene sulfonic acid as a catalyst. From Fourier transform infrared spectra analysis, it was found that the major reactions in the BPU/PF IPN system are the polymerization of BPU/MXDA and the self‐polymerization of PF. It was confirmed from scanning electron micrography that the BPU/PF IPN compatibility of the networks was improved, and the system was heterogeneous and more than one phase existed in the IPN. The tensile properties, flexural properties, impact, and hardness of the prepared IPN were studied. To obtain the best mechanical properties of IPN materials, the filler added in IPN materials has to be investigated. POLYM. ENG. SCI., 2011. © 2010 Society of Plastics Engineers     

Reaction-induced phase separation during the formation of a polyurethane-unsaturated polyester interpenetrating polymer network

In this study, an interpenetrating polymer network (IPN) based on a polyurethane (PU) and a partially end-capped unsaturated polyester (UPE) was prepared. The reaction-induced phase separation process of the IPN was studied using a phase contrast optical microscope and a transmission electron microscope (TEM), while reaction kinetics and onset of gelation were determined by a differential scanning calorimeter and a rheometer respectively. Except at low temperatures, the phase separation patterns were found to follow the spinodal decomposition mechanism. An interconnected phase developed quickly and was followed by coalescence of the periodic phase to form droplet/matrix type of morphology. A second level of phase separation also occurred within both the droplet and the matrix phases in some cases. The domain sizes resulting from both levels of phase separation gradually increased until the structure was locked by chemical gelation. Reaction temperature, PU reaction rate, and UPE reaction rate all had significant effects on the final morphology of the formed IPNs.     

Synthesis, Characterization and Reactivity Ratios of Phenylethyl Acrylate/Methacrylate Copolymers

2-Phenylethyl acrylate (PEA) and 2-Phenylethyl methacrylate (PEMA) were synthesized by reacting 2-Phenyl ethanol with acryloyl and methacryloyl chloride respectively. Homopolymers and copolymers were prepared by free radical polymerization technique using benzoylperoxide as initiator. Copolymers of PEA and PEMA with methyl acrylate (MA) and N-vinyl pyrollidone (NVP) of different compositions were prepared. The monomers and polymers were characterized by IR and NMR techniques. Thermal stability of the polymers were determined by TG analysis. The composition of the copolymer was determined using ¹H-NMR analysis. The reactivity ratios of the monomers were determined by the application of Finemann–Ross and Kelen–Tudos methods. The prepared copolymers were tested on leather for their pressure sensitive adhesive property.     

Interpenetrating polymer networks of polyurethane and furfuryl alcohol,IIa. Processability and properties of pultruded fiber-reinforced composites

A feasibility study of pultrusion of fiber-reinforced polyurethane/furfuryl alcohol (PU/FA) interpenetrating polymer/network IPN composites has been made. From the viscosity study, it was found that the pot life of the PU/FA IPN prepolymers increased with PU content and showed high reactivity at elevated temperature. It was confirmed from the morphological study that the wetting of fibers by the PU/FA IPN resins was improved with PU content. The appearance of the tensile failure surfaces of the pultruded glass fiber-reinforced PU/FA IPN composites showed “hackle patterns” for PU contents below 15 phr. The mechanical property study shows that the tensile strength of pultruded PU/FA IPN composites is the highest when the PU content is 5 phr. However, the flexural strength, flexural modulus and HDT decreased with PU content. The mechanical properties of various fiber-reinforced (glass, carbon, and Kevlar 49 aramid fiber) pultruded PU/FA IPN composites increased with fiber volume content.     

Characterization of anionic/cationic sequential IPNs. II. Studies of swelling,modulus, and alternate phase staining with CsF and LiI

Anionic/cationic interpenetrating polymer networks (IPNs) were synthesized by sequential polymerization from crosslinked polystyrene, PS, as polymer I and crosslinked poly(4-vinyl pyridine), P(4-VP), as polymer II. Ionomeric substitution of the two networks was based on sulfonation and quaternization of the phenyl and pyridine rings, respectively. The swelling, morphological, and dynamic mechanical behavior of ionomeric and unsubstituted IPNs was explored as a function of overall IPN composition. A theoretical analysis of the unsubstituted IPNs via the Thiele–Cohen equation showed that essentially no additional physical or chemical crosslinks were developed in the swollen state. Modulus studies showed that network I tends to dominate the mechanical properties in the bulk state. Swelling studies on the ionomeric IPNs as a function of pH demonstrated a complex change in behavior with the addition of NaCl, possibly due to an ionic screening effect. Electron microscopy involved alternate staining of the anionic and cationic phases using CsF and Lil and showed a two-phase structure, with the possibility of additional phases within phases due to separation of the ionomeric components. Comparison of the two staining techniques yielded strong evidence of a positive/negative–negative/positive phase contrast, depending on the phase being stained. In each case, domains were less than 100 nm (1000 Å), with the domain size decreasing as the P(4-VP) content increased. Also, a phase inversion appeared to occur between 50 and 80% P(4-VP). The dynamic mechanical studies supported the two-phase morphology and gave evidence of significant molecular mixing between the phases.     

蓖麻油聚氨酯互穿网络型聚合物性能的研究

分别用甲苯二异氰酸酯(TDI)和六亚甲基二异氰酸酯(HDI)与蓖麻油(CO)反应制备出两种聚氨酯预聚体,再用预聚体与苯乙烯、丙烯腈、甲基丙烯酸甲酯、环氧树脂(E-44或E-51)等单体制备出蓖麻油聚氨酯互穿网络型聚合物(CO-PU IPN),研究了体系组成对该聚合物拉伸强度的影响。结果表明,随着固化时间的延长,CO-PU IPN的拉伸强度逐渐增大,TDI型CO-PU IPN比HDI型的拉伸强度大;烯类单体比环氧树脂单体所制CO-PU IPN的拉伸强度大,不同烯类单体之间的差别不大;增加预聚体中NCO/OH的摩尔比,CO-PU IPN的拉伸强度都是先增加,后减小,在摩尔比为2.25时出现最大值;添加抗氧剂1010、紫外光吸收剂UV-327和光稳定剂292等对CO-PUIPN的拉伸强度基本没有影响。     

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。     

Synthesis of biodegradable PU/PEGDA IPNs having micro-separated morphology for enhanced blood compatibility

Summary New biodegradable hydrophobic polyurethane (PU)/hydrophilic poly (ethylene glycol) diacrylate (PEGDA) IPN was simultaneously synthesized with changing the molecular weight of PEGDA to investigate the effect of crosslinking density on the degree of phase separation. PU was modified using biodegradable poly(-caprolactone)diol and the hydroxy group of PEG was substituted to crosslinkable acrylate group having double bond, which induce photo-polymerization. The sturucture of PEGDA was confirmed by NMR. Because the reaction rate of PEGDA was faster than that of PU, the continuous matrix of the micro-separated PU/PEGDA IPNs having amphiphilic character was made of hydrophilic PEGDA-rich phase. All IPNs have sea-island morphology resulting from the suppressed phase separation. The effect of the degree of phase separation on blood compatibility was investigated.     

Compatibilization of Polyamide‐6/Polyarylate Blends by Means of an Ionomer

Summary: Polyamide‐6 (PA6)/polyarylate of bisphenol A (PAr) blends rich in PA6 and modified with an additional 15% poly[ethylene‐co‐(methacrylic acid)] partially neutralized with zinc (PEMA‐Zn) as a compatibilizer were obtained by melt mixing. Their phase structure, morphology, and mechanical performance were compared with those of the corresponding binary blends. The ternary blends were composed of a PA6 amorphous matrix and a dispersed PAr‐rich phase in which reacted PA6 and PEMA‐Zn were present. Additionally, minor amounts of a crystalline PA6 phase, and a PEMA‐Zn phase were also present. The chemical reactions observed led to a clear decrease in the dispersed particle size when PEMA‐Zn was added, indicating compatibilization. Consequently, the mechanical behavior of the blends with PEMA‐Zn improved, leading, mainly in the case of the blend with 10% PAr, to significant increases in both ductility and impact strength with respect to those of the binary blends. These increases were more remarkable than the slight decrease in stiffness as a consequence of the rubbery nature of the compatibilizer.

Cryogenically fractured surface of the PA6/PAr‐PEMA‐Zn 70/30‐15 ternary blend.     

Dielectric and viscoelastic studies of poly(ethyl methacrylate) containing cholesteric compounds

Poly(ethyl methacrylate) (PEMA) containing small amounts of cholesteryl additives was studied by dielectric and dynamic mechanical spectroscopy. Dielectric data from pure PEMA and PEMA + additive systems were fitted to the WLF equation. Using the WLF constants obtained from the data for pure PEMA, the To values for PEMA + additive systems were determined in order to get the best fit of the experimental points to the WLF curve. Values of tan δmax (dielectric and mechanical) for all the PEMA + additive systems shift to higher temperatures compared with that for pure PEMA. In the glassy region, the moduli of PEMA + additive systems are higher than that of pure PEMA. Viscometric studies of PEMA + additive systems indicate the presence of some interaction. FTIR spectra of the polymer + additive systems show no shift in carbonyl bond frequency. The shift of Tg to higher temperatures indicates that chain motion in this region is hindered greatly by these additives and the reason for this may be the fitting or aligning of the additive molecules in the polymer matrix.     

Membrane properties of microporous structures prepared from polyethylene/polymethacrylate IPN

Polyethylene/polymethacrylate interpenetrating polymer networks (PE/PMA IPN) form a matrix–particle or a co‐continuous morphology that can be adjusted by the composition and synthesis conditions. Based on the fact that PMA degrades whereas PE crosslinks when they are exposed to energetic irradiation, we developed a new approach to create a porous structure by electron beam irradiation. IPN systems that differ in the methacrylate components and composition were studied. One system contains poly(butyl methacrylate‐co‐methyl methacrylate) (BMA‐co‐MMA) and the other contains poly(dodecyl methacrylate‐co‐ethyl methacrylate) (DMA‐co‐EMA) as the PMA phase. After electron beam irradiation followed by extraction with xylene, both IPN systems have a porous structure that is permeable to water. However, the structure and size of the pores depend on the PMA components and the synthesis conditions. PMAs with long aliphatic side chains degrade less than PMAs containing only short aliphatic pendant groups. Therefore, the PE/BMA‐co‐MMA IPN forms bigger pores than PE/DMA‐co‐EMA, resulting in a higher water flux. The molecular cutoffs of the IPN are characteristic for microfiltration or ultrafiltration.© 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 1976–1982, 2003