Photosensitive polynorbornene based dielectric. II. Sensitivity and spatial resolution

Photodefinable poly(decylnorbornene‐co‐epoxidenorbornene) copolymer has been developed as a dielectric material for electronic packaging applications. The photodefinition properties of the polymer are affected by the copolymer composition, the concentration of photoactive compound and the process conditions. In particular, ultra‐high contrast conditions were found to promote the fabrication of vertical sidewall structures. For photodefined structures, the vertical sidewalls were obtained at specific formulations and process conditions. Under different conditions, non‐vertical features were observed. Rutherford backscattering analysis (RBS), X‐ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FTIR), and scanning electron microscopy (SEM) were used to study the photodefinition properties. In this article, a mechanism based on the diffusion of photoactive compounds from the exposed area to the unexposed area is presented. The transport of photoactive compounds takes place through the free volume that results from solvent evaporation. The diffusion of the photoactive compounds to the surface of the polymer film results in a higher concentration of photogenerated acid at the surface. The movement of the photoactive compounds occurs in both the in‐plane and through‐plane directions. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 91: 3031–3039, 2004     

Structure–property relationships in photopolymerizable polymer networks: Effect of composition on the crosslinked structure and resulting thermomechanical properties of a (meth)acrylate‐based system

Photoinitiated polymer networks were formed by copolymerization of tert‐butyl acrylate with di(ethylene glycol) dimethacrylate (DEGDMA) or poly(ethylene glycol) dimethacrylate (PEGDMA). The degree of crosslinking was systematically varied by modifying the weight fraction and molecular weight of the dimethacrylate crosslinking agent. An increase in effective crosslink density with increasing crosslinking agent concentrations was confirmed by decreasing equilibrium swelling ratios (q) and increasing rubbery moduli (E_R). Glass transition temperatures (T_g) varied from ?22 to 124°C, increasing with increasing DEGDMA content and decreasing with increasing PEGDMA content. Tensile deformation behavior (at T_g) ranged from an elastomeric‐like large‐strain response for lightly crosslinked materials to a small‐strain brittle response for highly crosslinked networks. At low crosslinking levels, the strain‐to‐failure of the network polymers decreased quickly with increasing crosslinking agent concentration. The stress at failure demonstrated a more complex relationship with crosslinking agent concentration. The effect of composition on network structure and resulting properties (q, E_R, strain‐to‐failure) decreased as the crosslinking agent concentration increased. The results reveal trade‐offs in T_g, E_R, strain‐to‐failure, and failure stress with composition and network structure, and are discussed in light of the wide range of potential applications suggested in the literature for (meth)acrylate‐based photopolymerizable polymer networks including biomaterials and shape‐memory polymers. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Structure–property study of polyurethane anionomers based on various polyols and diisocyanates

Polyurethane (PU) anionomers were prepared as aqueous dispersions using dimethylol propionic acid (DMPA) as the stabilizing moiety. The principal diols used were polytetrahydrofuran of molecular weight 1000 (PTHF1000) and cyclohexane dimethanol (CHDM). The diisocyanates used in this study were isophorone diisocyanate (IPDI), hydrogenated methylene bisphenylene diisocyanate (H₁₂MDI), tetramethylene xylene diisocyanate (TMXDI), hexamethylene diisocyanate (HDI), and a 50 : 50 blend of IPDI and HDI. All these samples were neutralized using triethylamine (TEA) and chain-extended using hydrazine monohydrate. The dispersions were prepared at a NCO/OH ratio of 2 so that a comparison of their structure–property relationships could be made with respect to their mechanical and viscoelastic properties and solvent resistance. Also, two further samples were prepared of similar composition to the IPDI-based sample, but using poly (propylene glycol), PPG1000, and PTHF2000 polyols. The effects on the structure and properties of the PPG1000 and the higher molecular weight PTHF sample were compared with the PTHF1000 sample. Dynamic mechanical thermal analysis, tensile testing, solvent spot, and swelling studies were employed for the characterization of these materials. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 66: 2035–2044, 1997     

Studies on Indian silk. II. Structure–property correlations

This second in a series of articles deals with studies on the structure and physical properties of five varieties of Indian silk: two mulberry (bivoltine and crossbreed) and three nonmulberry (tasar, muga, and eri). A detailed analysis of the microstructural parameters and mechanical properties was reported. Significant differences between and within the varieties with respect to microstructural parameters (crystallinity, density, birefringence, dichroic ratio, sonic modulus, etc.), as well as the effect of microstructural parameters on mechanical properties, were discussed. Some of the observations made on the inverse stress relaxation behavior of the different silk varieties were also reported. The extent of variation of these morphological parameters was found to correlate well with the mechanical properties. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 1098–1115, 2004     

Structure–property relationship of polyimides based on pyromellitic dianhydride and short‐chain aliphatic diamines for dielectric material applications

Most polyolefins that are used for dielectric materials exhibit a low dielectric constant and operating temperatures up to 70°C. Polyimides offer a means to a higher dielectric constant material by the introduction of a polar group in the polymer backbone and are thermally stable at temperatures exceeding 250°C. A common dianhydride, pyromellitic dianhydride (PMDA), is reacted with various short‐chain diamines to produce polymers with high imide density. Homopolymers and copolymers synthesized had dielectric constants ranging from 3.96 to 6.57. These materials exhibit a dielectric constant twice that of biaxially oriented polypropylene and therefore a twofold increase in capacitance as well as maintaining low dissipation factors that are acceptable for this application. The experimental dielectric constants of these materials are also compared to density functional theory calculations and exhibit a close relationship. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 1276‐1280, 2013     

Processing–morphology–property relationships of polypropylene–graphene nanoplatelets nanocomposites

Polypropylene (PP) nanocomposites reinforced with graphene nanoplatelets (GNPs) were prepared via melt extrusion. A special sheet die containing with two shunt plates was designed. The relationships among the flow field of the special die, exfoliation, and dispersion morphology of the GNPs in PP and the macroscopic properties of the nanocomposites were analyzed. Flow field simulation results show that the die with shunt plates provided a high shear stress, high pressure, and high velocity. The differential scanning calorimetry, X‐ray scattering, and electron microscopy results reveal that the nanocomposites prepared by the die with the shunt plates had higher crystallinity values and higher exfoliation degrees of GNPs. The orientation of the GNPs parallel with the extrusion direction was also observed. The nanocomposites prepared by the die with shunt plates showed a higher electrical volume conductivity, thermal conductivity, and tensile properties. This indicated that the high shear stress exfoliated the GNPs effectively to a thinner layer and then enhanced the electrical, thermal, and mechanical properties. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44486.     

Thermotropic glazings for overheating protection. II. morphology and structure–property relationships

This article completes a systematic strategy for formulation and optimization of thermotropic systems with fixed domains (TSFDs) for overheating protection purposes. Focus was on characterization of morphology and on revealing optimization potential. A comprehensive characterization of scattering domain size and shape was done applying optical microscopy and scanning electron microscopy. In general, scattering domains exhibited inappropriate size and/or shape for optimum overheating protection performance. Moreover, several TSFD displayed defects (vacuoles, voids) resulting from thermomechanical or physicochemical interaction of matrix material and thermotropic additive during manufacturing. Morphological features along with solar optical and thermorefractive properties allowed for establishment of structure–property relationships. Light‐shielding efficiency of TSFD correlated well with scattering domain size and shape. The majority of TSFD showing defects exhibited an increase of solar hemispheric transmittance upon heating. Several strategies to overcome defect formation and to improve scattering morphology were suggested and proof of concept was shown partially, thus indicating a significant optimization potential of the established TSFD. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 39910.     

Structure–property relationship of polyetheramines as clay‐swelling inhibitors in water‐based drilling fluids

The influences of structure parameters of polyetheramines as clay‐swelling inhibitors in water‐based drilling fluids on the application performances were studied. Interactions of polyetheramines with clays were investigated through elemental analysis (EA), X‐ray diffraction (XRD), and thermogravimetric analysis (TGA). The results showed that lower molecular weight, hydrophobic oxypropylene segment, and plentiful amino group of polyetheramines favored improvement of inhibitive properties, enhancement of adsorption abilities, and expelling interlayer bound waters of clays (as confirmed by cutting rolling test, bentonite inhibition test, EA, XRD, and TGA studies). Simultaneously, the polyetheramines did not produce adverse effect to filtration control of the drilling fluids. In addition, XRD patterns revealed that these polyetheramines could intercalate into interlayer spaces of clays and display a monolayer arrangement. The corresponding basal spacing of clays was correlated only with molecular weight of polyetheramines. The dense loading of polyetheramines in the interlayer of clays was beneficial in improving inhibitive properties. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Effect of vegetable‐based polyols in unimodal glass‐transition polyurethane slabstock viscoelastic foams and some guidance for the control of their structure–property behavior. I

We investigated the synthesis and structure–property behaviors of two types of vegetable‐oil polyols (soy oil and castor oil) and their use in viscoelastic (VE) polyurethane foams (PUFs). This article is the first in a two‐part series. In this initial part, we principally address the dynamic mechanical analysis (DMA) behavior of these foams in conjunction with information on the cellular morphology, sol fraction, and rise and reaction temperature profile behavior (the latter two parameters were determined during the foaming process). Particular emphasis is placed on the DMA damping characteristics, which represent one of the most critical parameters in the application of VE PUFs. It is also shown that the damping characteristics could be modified in such foams by the variation of the isocyanate/hydroxyl (×100) index, the addition of plasticizer, and in the case of soy polyols, the soy content. The frequency dependence of the VE PUFs is also briefly addressed. In the second article in this series, which directly follows this article, we further address the details of other relevant physical properties of these same foams in view of their applied nature. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Structure and property of tetrafluoroethylene‐propylene elastomer‐OVPOSS composites

Tetrafluoroethylene‐propylene elastomer‐octavinyl‐polyhedral oligomeric silsesquioxane (TFE/P‐OVPOSS) composites containing various percentages of OVPOSS are prepared via room temperature milling and heat vulcanization at 170°C. The composites are characterized by FTIR, ¹³C‐NMR, ²⁹Si‐NMR, XRD, DSC, SEM, tensile test, DMA, and TGA. The crosslink bond formation between TFE/P and OVPOSS conforms to the structural characterization of the composites. The OVPOSS cages aggregate when the OVPOSS dosage is more than 6 as observed from the XRD curves and SEM images. The swelling test shows that the experimental crosslink density is lower than the calculated crosslink density, indicating that not all reacted vinyl groups are converted into crosslink bonds. Meanwhile, the incorporation of OVPOSS significantly enhances the mechanical property and elevates the glass temperature of the composites. However, the thermal property is only improved slightly. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 1281‐1288, 2013     

A structure–property study of IPDI-based polyurethane anionomers

Polyurethane (PU) anionomers were prepared as aqueous dispersions and as solutions in tetrahydrofuran or absolute ethanol using dimethylol propionic acid (DMPA) as the stabilizing moiety, isophorone diisocyanate, polytetrahydrofuran, and cyclohexane dimethanol. The structure–property relationships were investigated for these PUs, cast as films, at similar and differing chain-extension levels. Comparisons were made with respect to the mechanical and viscoelastic properties and solvent resistance. Finally, the consequences of DMPA incorporation into the PU backbone were determined for two solvent-borne compositions of similar structure with and without DMPA. Dynamic mechanical thermal analysis, tensiometry, solvent spot tests, and swelling studies were employed for the characterization of the materials. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 67:1437–1448, 1998     

Structure−property relationships of halogen‐free flame‐retarded poly(butylene terephthalate) and glass fiber reinforced PBT

Flame retardancy for thermoplastics is a challenging task where chemists and engineers work together to find solutions to improve the burning behavior without strongly influencing other key properties of the material. In this work, the halogen‐free additives aluminum diethylphosphinate (AlPi‐Et) and a mixture of aluminum phosphinate (AlPi) and resorcinol‐bis(di‐2,6‐xylyl phosphate) (AlPi‐H + RXP) are employed in neat and reinforced poly(butylene terephthalate) (PBT), and the morphology, mechanical performance, rheological behavior, and flammability of these materials are compared. Both additives show submicron dimensions but differ in terms of particle and agglomerate sizes und shapes. The overall mechanical performance of the PBT flame‐retarded with AlPi‐Et is lower than that with AlPi‐H‐RXP, due to the presence of larger agglomerates. Moreover, the flow behavior of the AlPi‐Et/PBT materials is dramatically changed as the larger rod‐like primary particles build a percolation threshold. In terms of flammability, both additives perform similar in the UL 94 test and under forced‐flaming combustion. Nevertheless, AlPi‐Et performs better than AlPi‐H + RXP in the LOI test. The concentration required to achieve acceptable flame retardancy ranges above 15 wt %. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Polystyrene foams. III. Structure–tensile properties relationships

In the previous two parts of this series of articles, the relations among the foaming conditions, microstructure, and impact properties of expanded microcellular polystyrene (EPS) were discussed. In this article, the effects of the foaming conditions and structure on the tensile properties of EPS were investigated. A systematic investigation was performed based on a statistical experimental design. Various processing conditions were used and a wide range of cellular structures was developed. Regression analysis was conducted on the data and expressions were developed to quantify the relationship between the tensile properties and the cellular structure. Foaming time and foaming temperature were the most important processing parameters influencing the tensile modulus and strength. The tensile modulus and strength increased with an increasing foam density, but they decreased slightly when the cell size increased. Two different approaches were used to develop models relating the modulus to the foam density of EPS. Both models fitted the experimental data quite well. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 1427–1434, 2003     

Strontium(II) ion uptake on poly(N‐vinyl imidazole)‐based hydrogels

In this article, we report on the extraction of Sr(II) ions from aqueous solution with a series of poly(N‐vinyl imidazole)‐based hydrogels. The hydrogels were synthesized by the crosslinking of N‐vinyl imidazole with four different crosslinkers with γ rays as initiators. The well‐characterized hydrogels were used as Sr(II) sorbents. Sr(II) uptake was determined with a colorimetric method with Rose Bengal anionic dye. Scanning electron microscopy–energy‐dispersive spectroscopy analysis of the Sr(II)‐loaded polymers was recorded to ascertain the uptake of Sr(II) ions. The experimental adsorption values were analyzed with the Freundlich and Temkin equations, and the kinetics of adsorption were investigated with a pseudo‐second‐order sorption kinetic model. The results show that the equilibrium data fit well in the Freundlich isotherm and followed a pseudo‐second‐order kinetic model. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Effect of vegetable‐based polyols in unimodal glass‐transition polyurethane slabstock viscoelastic foams and some guidance for the control of their structure–property behavior. II

Building on the dynamic mechanical analysis (DMA) characterization of the viscoelastic (VE) foam materials discussed in part I of this two‐part sequential series of articles, in this second part, we provide further information on the general physical properties of many of the same soy polyol and castor‐oil VE foams. In particular, the tensile, tear, elongation, indentation force deflection, support factor, compression set, hysteresis and ball‐rebound (resilience), and density properties are addressed in this article. The air flow and force buildup after compression deformation are also considered. Particular attention is also given to noting the degree of correlation of ball‐rebound behavior to that of the DMA damping data provided in part I. We concluded that when all of the properties of these vegetable‐based VE foams were taken as a whole, they had acceptable structure–property behaviors for VE applications, although certainly, the formulations could undoubtedly be further fine‐tuned for additional optimization. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Selection of thinner for epoxy–amine system used as binder for polymeric mortars

Epoxy resin mortars are mainly used in the implementation of precast items used in the civil engineering field. The workability of these mortars represents a major obstacle to the development of this field. In order to improve this property, different types of thinners are selected to study their effect on the rheological properties of the epoxy–amine system. Rheological tests are performed in order to estimate the resin gel point and to measure its viscosity during the crosslinking reaction. It appears that viscosity is the lowest for mixtures prepared with methyl octanoate, o‐xylene, and butyl glycidyl ether. Methyl octanoate is chosen as an ecofriendly thinner. The curing process is evaluated by varying the amount of the selected thinner using isothermal and dynamic DSC to determine the end of crosslinking. The mechanical properties using dynamic mechanical analysis (DMA) and tensile resistance testing of the cured epoxy resin with different amounts of methyl octanoate are also investigated. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43970.     

Structure–properties relationship in toughening of poly(butylene terephthalate) with core–shell modifier

The performance of acrylonitrile–butadiene–styrene (ABS) core–shell modifier with different grafting degree, acrylonitrile (AN) content, and core–shell ratio in toughening of poly(butylene terephthalate) (PBT) matrix was investigated. Results show PBT/ABS blends fracture in ductile mode when the grafting degree is high, and with the decrease of grafting degree PBT/ABS blends fracture in a brittle way. The surface of rubber particles cannot be covered perfectly for ABS with low grafting degree and agglomeration will take place; on the other hand, the entanglement density between SAN and PBT matrix decreases because of the low grafting degree, inducing poor interfacial adhesion. The compatibility between PBT and ABS results from the strong interaction between PBT and SAN copolymer and the interaction is influenced by AN content. Results show ABS cannot disperse in PBT matrix uniformly when AN content is zero and PBT/ABS fractures in a brittle way. With the addition of AN in ABS, PBT/ABS blends fracture in ductile mode. The core–shell ratio of ABS copolymers has important effect on PBT/ABS blends. When the core–shell ratio is higher than 60/40 or lower than 50/50, agglomeration or cocontinuous structure occurs and PBT/ABS blends display lower impact strength. © 2006 Wiley Periodicals, Inc. J Appl PolymSci 102: 5363–5371, 2006     

Synthesis and properties of poly(ether imide)s derived from 2,5‐bis(3,4‐dicarboxyphenoxy)biphenyl dianhydride and aromatic ether–diamines

A series of poly(ether imide)s (PEIs) with light colors and good mechanical properties were synthesized from 2,5‐bis(3,4‐dicarboxyphenoxy)biphenyl dianhydride and various aromatic ether–diamines via a conventional two‐step polymerization technique that included ring‐opening polyaddition at room temperature to poly(amic acid)s (PAAs) followed by thermal imidization. The precursor PAAs had inherent viscosities ranging from 0.71 to 1.19 dL/g and were solution‐cast and thermally cyclodehydrated to flexible and tough PEI films. All of the PEI films were essentially colorless, with ultraviolet–visible absorption cutoff wavelengths between 377 and 385 nm and yellowness index values ranging from 10.5 to 19.9. These PEIs showed high thermal stabilities with glass‐transition temperatures of 206–262°C and decomposition temperatures (at 10% weight loss) higher than 478°C. They also showed low dielectric constants of 3.39–3.72 (at 1 MHz) and low water absorptions below 0.85 wt %. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Phosphorus‐containing polyhedral oligomeric silsesquioxane/polyimides hybrid materials with low dielectric constant and low coefficients of thermal expansion

Novel phosphorus‐containing polyhedral oligomeric silsesquioxane (POSS)/polyimides (PI) hybrid materials with low dielectric constant and low linear coefficients of thermal expansion (CTE) were prepared and characterized. The POSS/PI hybrid materials were synthesized with octa(aminopropyl)silsesquioxane (OAPS) and a series of phosphorus‐containing polyamide acids(PAA). The PAAs were synthesized with bis(4‐aminophenoxy) phenyl phosphine oxide (BAPPO), 4,4’‐diaminodiphenyl ether (ODA) and 3,3',4,4'‐biphenyl tetracarboxylic diandhydride (BPDA). The structures and properties of the hybrid materials were characterized. And the effect of the phosphorus‐containing structure on the POSS/PI hybrid materials was discussed. The dielectric constants and CTE of the hybrid materials were remarkably lower than that of the unmodified POSS/PI films. The lowest values of dielectric constant and CTE could achieve as low as 2.64 (1 MHz) and 27.45 ppm/K. Besides, the hybrid materials also had excellent thermal properties. The highest 5% weight loss temperature of the hybrid materials was as high as 580°C under air. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42611.