Vapor‐induced crystallization behavior of bisphenol‐A polycarbonate

The effects of exposure time and vapor pressure on the crystallization behaviors of bisphenol‐A polycarbonate (BAPC) films were investigated at 25°C by using differential scanning calorimetry (DSC). Double melting peaks were observed for various BAPC samples after vapor‐induced crystallization. The low temperature melting peak shifted to higher temperature and became sharper with increasing exposure time, and could be assigned to defective crystals with smaller crystal size. Crystallinity and average crystal dimension normal to (020) were calculated from wide‐angle X‐ray diffraction spectra. A good agreement was obtained between crystallinity values obtained from WAXD and those from DSC. The morphology of crystallized samples after various exposure time periods was examined by means of polarized optical microscopy. Nucleation occurred at the initial stage of vapor‐induced crystallization. Poor crystals become perfect through segment reorganization with increasing exposure time, and spherulites' growth was observed. The average diameter of spherulites increased from 2 μm for 1 h, to 7 and 16 μm after 3 and 56 h, respectively. POLYM. ENG. SCI., 46:729–734, 2006. © 2006 Society of Plastics Engineers     

Antisolvent crystallization and solid‐state polymerization of bisphenol‐A polycarbonate

Bisphenol‐A polycarbonate (BAPC) was synthesized by solid‐state polymerization (SSP) using a semicrystalline prepolymer crystallized by antisolvent method. The antisolvent crystallization was investigated as a function of antisolvent types using X‐ray diffraction (XRD), different scanning calorimetry (DSC), and scanning electron microscopes (SEM). The results showed antisolvent types had a significant effect on the crystallization of BAPC. Prepolymer induced by acetone as an antisolvent gained a higher crystallinity of 37.0%, more uniform particle size, and mature crystal structure compared with the samples crystallized by methanol and ethanol. Then crystallization of BAPC by acetone was carried out at crystallization temperature in the range of 40–80 °C for 1–5 h. A high crystallinity of 42.0% was acquired with the crystallization conducted at 70 °C for 2 h. Prepolymer with appropriate crystallinity of 37.8% resulted in high‐molecular‐weight polymer of 57,411 via SSP due to the effect of crystallinity and plasticization of residual solvent. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43636.     

A perspective on emerging polymer technologies for bisphenol‐A replacement

Recent attention surrounds bisphenol‐A (BPA) due to potential estrogen mimicry and human health hazards. The public's negative reactions to these concerns threaten the commercial use of BPA requiring the global polymer community to investigate suitable replacements for commercial products that demand very good thermal and mechanical properties from BPA. This review highlights four classes of polymers that often utilize BPA for enhancing specific properties: polycarbonates, polyesters, epoxies and polyimides. A compilation of recent efforts involving the design of BPA‐free polymers is provided. Alternative monomers include 2,2,4,4‐tetramethyl‐1,3‐cyclobutanediol and isosorbide, and emerging polymers that exhibit acceptable thermal and mechanical properties are discussed. Copyright © 2012 Society of Chemical Industry     

The stabilization of bisphenol‐A based polycarbonate by phosphine oxide

A Bisphenol‐A based polycarbonate was stabilized by a new polymer stabilizer named di(p‐butoxyphenyl)cyclohexylphosphine oxide. The stabilizer was mixed with the polymer in methylene chloride solution. Later, the solution was vaporized and the stabilized polymer was dried. Specimens were cut and heat treated at different temperature and durations. Small amounts of stabilizer enhanced the breaking strength and elongation at break properties of as molded and heat treated polycarbonate. The modulus of elasticity reduced with stabilization. The stabilizer had a plasticizing effect too. At high stabilizer rates (c > 1%) both thermal and mechanical properties were deteriorated. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Kinetic study on epoxy bisphenol‐A diacrylate IPN formation

Interpenetrating polymer networks (IPN) based on diglycidyl ether of bisphenol‐A (DGEBA) and bishenol‐A diacrylate (BADA) in weight ratios of 100/0, 50/50, and 0/100 were blended and were cured simultaneously by using benzoyl peroxide (BPO) and 4,4′‐methylenedianiline (MDA) as curing agents. Kinetic study during IPN formation was carried out at 65, 70, 75 and 80 °C. Absorbance changes at 1623.3 cm⁻¹ and 914 cm⁻¹ relating to concentration changes of CC and epoxide were monitored with Fourier‐transform infrared spectroscopy (FTIR). The epoxide cure kinetic data revealed a combination of non‐catalytic bimolecular reaction and a catalyzed termolecular reaction, while the CC cure kinetic data fitted a first‐order reaction. The calculated kinetic parameters indicated decreased rate constants and increased activation energies of the IPN compared with those of the individual components. Presumably, chain entanglements between the two networks provide a sterically hindered environment for the cure reactions and vitrification restrains the chain mobility, accounting for the kinetic parameters. © 1999 Society of Chemical Industry     

Fabrication of pH‐responsive molecularly imprinted polyethersulfone particles for bisphenol‐A uptake

pH‐responsive molecularly imprinted particles were successfully fabricated by pore‐filling poly (acrylic acid) (PAA) gels into bisphenol‐A (BPA)‐imprinted polyethersulfone particles. The adsorbed BPA amount (or rate) decreased after filling the PAA gels both for the imprinted and nonimprinted particles. However, it was confirmed that changing the acidity of the solution reversibly controls the rebinding ability toward BPA and that the BPA uptake of the pore‐filled particles exhibited chemical valve behavior at a pH between 3 and 6. This finding can be attributed to the swelling of the PAA gels in the particles. The present methodology provides a simple way to prepare pH‐responsive molecularly imprinted materials and is expandable to the imprinting of other hydrophobic molecules, such as dibenzofuran. Also, the results of this work demonstrate the potential of stimuli‐responsive molecularly imprinted polymer materials as smart chemicals and as drug‐delivery systems. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Poly(oxyethylene)diamine‐derived hydrophilic copolymers for emulsifying diglycidylether of bisphenol‐A

A series of reactive surfactants were synthesized by the reaction of hydrophilic poly(oxyethylene)diamines of 2000–6000 g/mol molecular weight and diglycidylether of bisphenol‐A resin. The synthesized surfactants consisted of multiple functionalities including tertiary amines, hydrophobic alkylphenoxys, and reactive oxirane groups. After treatment with hydrochloric acid, the surfactants consisted of two different hydrophilic groups: cationic quaternary ammonium salts and nonionic oxyethylene segments. By prudent selection of the proper hydrophile–lipophile balance, the surfactant can be highly effective for solubilizing the epoxy resin in water to form a stable emulsion at a fine particle size of 350 nm. Another advantage is that the surfactant may participate in a curing process through the built‐in oxirane reaction and become a nonextractable component in polymer matrix. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 1797–1802, 2004     

Epoxy toughening using low viscosity liquid diglycidyl ether of ethoxylated bisphenol‐A

Two new epoxy resins, diglycidyl ether of ethoxylated bisphenol‐A (BPA) with two and six oxyethylene units (DGEBAEO‐2 and DGEBAEO‐6) were synthesized and characterized. DGEBAEO‐6 was used to toughen the conventional epoxy resin diglycidyl ether of BPA (DGEBA). The blends of DGEBA with different amounts of DGEBAEO‐6 were cured by 4,4′‐diamino diphenylmethane (DDM), and their thermal and mechanical properties were examined. The DSC and DMA results presented that DGEBA/DGEBAEO‐6 blends exhibited a homogenous phase, and the glass transition temperature of the blends was inversely proportional to the content of DGEBAEO‐6. The impact strength of the cured blends was directly proportional to the content of DGEBAEO‐6, and reached five times higher than that of the neat DGEBA when 50 wt % DGEBAEO‐6 was used; the same impact strength was achieved for DDM‐cured DGEBAEO‐2. The viscosities of the blends decreased with increasing the DGEBAEO‐6 content, whereas the tensile and flexural strength and the thermal stabilities were not obviously affected. Scanning electron microscopic results confirmed that the plastic deformation inducing by the incorporated flexible oxyethylene units was responsible for the toughness improvement. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Melt polymerization of bisphenol‐A and diphenyl carbonate in a semibatch reactor

The effect of thermodynamic phase equilibrium on the kinetics of semibatch melt polycondensation of bisphenol‐A and diphenyl carbonate was studied for the synthesis of polycarbonate. In the melt‐polymerization process, a partial loss of diphenyl carbonate occurs as the reaction by‐product phenol is removed from the reactor. To obtain a high molecular weight polymer under high temperature and low‐pressure conditions, a stoichiometric mol ratio of the two reactive end groups needs to be maintained during the polymerization. In this work, vapor–liquid equilibrium data for a binary mixture of phenol and diphenyl carbonate are reported and they are used in conjunction with the Wilson equation to calculate the exact amounts of diphenyl carbonate and phenol returned from a reflux column to the reactor. A good agreement between the reactor model simulations and the experimental polymerization data was obtained. It was also observed that diphenyl carbonate is quickly consumed during the early stage of polymerization and the fraction of evaporated diphenyl carbonate refluxed to the reactor is essentially constant during this period. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 1253–1266, 2001     

Chain extension of poly(ethylene terephthalate) with bisphenol‐A dicyanate

Chain extension of poly(ethylene terephthalate) (PET) with bisphenol‐A dicyanate (BADCy) was studied using an internal mixer under reactive blending conditions. The reaction between PET and BADCy was confirmed by Fourier transform infrared (FTIR) and chemical titration. With increasing amount of BADCy introduced, the modified PET gave rise to higher torque during stirred in an internal mixer, higher viscosity (η′), and higher storage modulus (G′). Measurement of intrinsic viscosity showed that BADCy indeed extended the molecular weight of PET. DSC analysis represented that T_m and T_c of the modified PET were shifted to low temperatures. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Thermally activated polymerization behavior of bisphenol‐S/methylamine‐based benzoxazine

A bifunctional benzoxazine monomer, 6,6′‐bis(3‐methyl‐3,4‐dihydro‐2H‐benzo[e] [1,3]oxazinyl) sulfone (BS‐m), was synthesized from bisphenol‐S, methylamine, and formaldehyde via a solution method. The chemical structure of BS‐m was characterized with ¹H and ¹³C‐nuclear magnetic resonance (NMR) spectroscopy, Fourier transform infrared (FTIR) spectroscopy, and elemental analysis. The ring‐opening polymerization reaction of BS‐m monomer was studied by FTIR, ¹³C solid‐state NMR, and differential scanning calorimetry. With the polymerization reaction proceeding, the intensities of the FTIR absorption peaks of CH₂, C? O? C, and C? N? C of the oxazine ring decreased gradually, and some of these absorption peaks disappeared. The shapes and intensities of the absorption peaks associated with benzene ring, sulfone group, and aromatic C? S bond changed in various ways. The changes in the solid‐state ¹³C‐NMR pattern, including chemical shifts, intensity of resonances, and line‐width, were observed from the spectra of BS‐m and the corresponding polybenzoxazine. The melting process of BS‐m overlapped with the beginning of the ring‐opening polymerization reaction. The polymerization kinetic parameters were evaluated for nonisothermal and isothermal polymerization of BS‐m. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Thermal characterization of diglycidyl ether of bisphenol‐A/phosphorus containing amines

In order to improve the thermal resistance of diglycidyl ether of bisphenol‐A (DGEBA), phosphorus‐containing di‐ and tri‐amines, i.e., bis (3‐aminophenyl) methyl phosphine oxide (B) and tris (3‐aminophenyl) phosphine oxide (T), were used as curing agents. The effect of phosphorus content on the curing characteristics and char residue of cured resins in nitrogen atmosphere was evaluated by using different molar ratios of conventional curing agent, i.e. 4, 4′‐diaminodiphenyl sulfone (D) and amine B or T. Activation energy of curing, as evaluated by using the multiple heating rate method, was lowest when triamine T (61.0 kJmol^?1) was used as hardener and was highest when D (68.7 kJmol^?1) was used. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 390–395, 2001     

Miscibility of polymer blends of poly(styrene‐co‐4‐hydroxystyrene) with bisphenol‐A polycarbonate

The miscibility of blends of bisphenol‐A polycarbonate (BAPC) and tetramethyl bisphenol‐A polycarbonate (TMPC) with copolymers of poly(styrene‐co‐4‐hydroxystyrene) (PSHS) was studied in this work. It has been demonstrated that BAPC is miscible with PSHS over a region of approximately 45–75 mol % hydroxyl groups in the copolymer. TMPC has a wider miscible window than BAPC when blended with PSHS. The blend miscibility was considered to be driven by the intermolecular attractive interactions between the hydroxyl groups of the PSHS and the π electrons of the aromatic rings of both polycarbonates (PCs). As the FTIR measurements showed, after blending of BAPC with PSHS, there is no visible shift of the carbonyl band of BAPC at 1774 cm⁻¹, whereas the stretching frequency of the free hydroxyl groups of the copoly‐ mers at 3523 cm⁻¹ disappeared. The large positive values of the segment interaction energy density parameter B_st‐HS calculated from the group contribution approach indicated that the intramolecular repulsive interaction may also have played a role in the promotion of the blend miscibility. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 74: 639–646, 1999     

Aromatic polyesters based on bisphenol‐A for liquid insulating systems: A synthetic approach

This work concentrates on the area of the synthesis of polymers for liquid insulating systems. We have studied reactions of aromatic esters like diphenyl terephthalate/isophthalate, diphenyl carbonate with Bisphenol‐A, and tri functional glycerol for the synthesis of aromatic polyesters that can be used as liquid insulating systems. The process comprises a transesterification resin synthesis based on a single pot process, with a temperature profile up to 250°C and an inert atmosphere of nitrogen. The byproduct of the phenol is continuously removed under a steady flow of nitrogen to enable polycondensation. The resins obtained were tested for their physical properties, such as melting range, relative viscosity, and hydroxyl value. These resins were also used in solution film formation to establish their film forming properties. The method explored is the simplest one, and permits the use of commercial materials as the feedstock. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 95: 606–614, 2005     

Dynamics of lipase catalyzed enzymatic degradation of poly(bisphenol‐A carbonate)

Poly(bisphenol‐A carbonate) (PC) was degraded in solution at various temperatures (26–70°C) by different lipases, Candida Rugosa (CR), Hog Pancreas (HP), Lipolase (LL), and Novozyme (NV), in various solvents. The degradation of PC was monitored using gel permeation chromatography (GPC). The molecular weights of oligomers obtained were around ～1,400 irrespective of the lipases used. Continuous distribution kinetics was proposed to determine the rate coefficients of the polymers and deactivation of the enzyme. The FTIR analysis of the polymer before and after degradation showed that there is large reduction of carbonate linkages and generation of hydroxyl and acidic groups in the broken chains. The optimal temperatures for HP and other lipases were 50 and 60°C, respectively. HP showed higher degradation activity at lower temperatures and the overall degradability of the lipases was in the order of LL > CR > NV > HP. The effect of viscosity and polarity of the solvents on the degradation of the polycarbonate was also investigated. While the degradation rate decreased with viscosity, it increased with polarity for the solvents. © 2003 Wiley Periodicals, In6c. J Appl Polym Sci 91: 2391–2396, 2004     

Enthalpy relaxation in bisphenol‐A polycarbonate/poly(methyl methacrylate) blends

Bisphenol‐A polycarbonate (PC)/poly(methyl methacrylate) (PMMA) blends (PC/PMMA) were prepared by melt mixing with and without a trans‐esterification catalyst (tetrabutylammoniun tetraphenylborate), which is able to promote inter‐exchange reactions between PC and PMMA. Evidences of the ester–ester exchange reaction taking place were pointed out via Fourier Transform Infra‐Red and size exclusion chromatography analyses. A series of enthalpy relaxation measurements were carried out for the pure polymers and for blends thereof. The data were analyzed on the basis of the Tool–Narayanaswamy–Moynihan/Kohlraush–Williams–Watts model. This model characterizes the structural relaxation in the glass transition region by means of four parameters: the apparent activation energy (Δh*), the nonlinearity (x), the nonexponentiality (β), and the pre‐exponential factor (τ₀). The apparent activation energy can be determined from the cooling rate dependence of the fictive temperature (T_f) measured using DSC. Δh* values of homogeneous blend and of the starting polymers were determined in this way, while an estimation of x, β and τ₀ was proposed. Comparisons were made between a single glass transition temperature PC/PMMA blend and homopolymers data. The experimental values of Δh* suggest that the degree of cooperativity decreases on going from the starting polymers to the blend. POLYM. ENG. SCI., 47:218–224, 2007. © 2007 Society of Plastics Engineers.     

Surface and wetting characteristics of textured bisphenol‐A based polycarbonate surfaces: Acetone‐induced crystallization texturing methods

Polycarbonate (PC) sheet is a promising material for facile patterning to induce hydrophobic self‐cleaning and dust repelling properties for photovoltaic panels’ protection. An investigation to texture PC sheet surfaces to develop a self‐cleaning structure using solvent induced‐crystallization is carried out using acetone. Acetone is applied in both liquid and vapor states to generate a hierarchically structured surface that would improve its contacts angle and therefore improve hydrophobicity. The surface texture is investigated and characterized using atomic force microscopy, contact angle technique (Goniometer), optical microscopy, ultraviolet‐visible spectroscopy (UV–vis) and Fourier transform infrared spectroscopy. The findings revealed that the liquid acetone‐induced crystallization of PC surface leads to a hierarchal and hydrophobic surface with an average contact angle of 135° and average transmittance <2%. However, the acetone vapor induced‐crystallization results in a slightly hydrophilic hierarchal textured surface with high transmittance; in which case, average contact angle of 89° and average transmittance of 69% are achieved. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43074.     

Non‐catalytic anhydride curing of hydrogenated bisphenol‐A glycidyl ether with 1,2,4‐cyclohexanetricarboxylic anhydride and light emitting diode encapsulation

Noncatalytic anhydride curing of hydrogenated bisphenol‐A glycidyl ether (YX8000) using hydrogenated trimellic anhydride (1,2,4‐cyclohexanetricarboxylic anhydride, H‐TMAn) and methylhexahydrophthalic anhydride (MeHHPA) were studied. Differential scanning calorimetry data shows no exthothermal under 190°C using MeHHPA without catalyst because of the low reactivity. On the other hand, H‐TMAn had higher reactivity and it can be cured without catalyst. The effect of anhydride concentration both on curing and on properties was studied in detail. For example, the highest T_g was found when YX8000 : H‐TMAn = 100 : 75 or YX8000 : MeHHPA = 100 : 100. The highest curing exothermal was found at similar ratio. Following, the encapsulation of light emitting diode (LED) was prepared with two anhydrides. Surface volume decrease was observed with MeHHPA by its evaporation, but H‐TMAn gave flat surface. After thermal cycle test of these LED, H‐TMAn was found to have better crack resistance than MeHHPA. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 962–966, 2006     

Synergistic barrier flame‐retardant effect of aluminium poly‐hexamethylenephosphinate and bisphenol‐A bis(diphenyl phosphate) in epoxy resin

Two flame retardants, aluminium poly‐hexamethylenephosphinate (APHP) and bisphenol‐A bis(diphenyl phosphate) (BDP), were incorporated into diglycidyl ether of bisphenol A (DGEBA) thermoset with 4,4′‐diaminodiphenyl sulfone (DDS) as curing agent, and then the synergistic flame‐retardant behaviors of the cured thermosets were investigated. Compared with thermosets containing 10 wt% APHP and 10 wt% BDP alone, the sample with 3.3 wt% APHP and 6.7 wt% BDP (3.3%APHP/6.7%BDP/EP; EP is DGEBA/DDS) possessed a better flame‐retardant effect since its limited oxygen index reached 35.0% and in the UL94 test it passed the V‐0 rating. The cone calorimeter test revealed that the 3.3%APHP/6.7%BDP/EP sample generated less gaseous fragments and more smoke particles instead of fuels and verified that APHP and BDP exhibited an outstanding synergistic effect on the barrier effect. Macroscopic digital photos and micrographs from scanning electron microscopy further disclose that BDP facilitated the formation of a flexible film covering holes in the residue. The flexible film was combined with aluminium phosphate particles which were produced by decomposed APHP, thereby forming a char layer with increased barrier effect. The synergistic barrier effect from APHP and BDP imposed a better flame‐retardant performance for epoxy thermosets. © 2017 Society of Chemical Industry     

Nonisothermal cure kinetics of diglycidylether of bisphenol‐A/amine system reinforced with nanosilica particles

Epoxy‐silica nanocomposites were obtained from directly blending diglycidylether of bisphenol‐A (DGEBA)‐based epoxy and nanoscale silica (NS) and then curing with 4,4′‐diaminodiphenylamine (DDA). The effect of amount of nanosilica (NS) particles as catalyst on the mechanism and kinetic parameters of cure reaction of DGEBA/DDA system was studied. The kinetics parameters were obtained from nonisothermal differential scanning calorimeter (DSC) data using the Kissinger and Ozawa equations. The exothermic peak was shifted toward lower temperatures in DGEBA/DDA/NS system with increasing the amount of nanoslica particles. However, the existence of NS particles with hydroxyl groups in the structure in the mixture of DGEBA/DDA catalyzes the cure reaction and increases the rate constant. The activation energy of cure reaction of DGEBA/DDA system obtained from two methods were in good agreement, and showed a decrease when NS particles were present in the mixture. The mechanism of reaction of DGEBA with DDA was carried out by isothermal curing in the oven at 130°C and measuring the disappearance peak of epoxide group at 916 cm^?1 using FTIR. The diffusive behavior of two systems was investigated during water sorption at 25°C and the experimental results fitted well to Fick's law. Diffusion coefficient of cured sample from DGEBA/DDA/10% NS blend decreased in comparison with the sample without NS particles. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 3855–3863, 2007