Chemical nucleation,a new concept applied to the mechanism of action of organic acid salts on the crystallization of polyethylene terephthalate and bisphenol—A polycarbonate

Bisphenol-A polycarbonate (PC) and Polyethylene terephthalate (PETP) systems containing different concentrations of sodium o-chlorobenzoate (SOCB) as crystallization promoters have been studied by d.s.c., i.r. and g.p.c. It is shown that the time and temperature of mixing of the salt with the polymer considerably affects the crystallization rates. G.p.c. and i.r. show that a chemical reaction occurs during the mixing process between the salt and the ester links of the macromolecules. This reaction produces ionic end-groups which are responsible for the acceleration of the crystallization rate. This phenomenon is called ‘chemical nucleation’. The same behaviour is observed also with other alkali metal salts derived from aromatic carboxylic acids.     

Size-controllable nanospheres prepared by blending a thermoset monomer in confined morphology with thermoplastic elastomer

Bisphenol-A based benzoxazine monomer (BZ) forms a polybenzoxazine (polyBZ) thermoset after thermal curing. However, when BZ is blended with polystyrene-block-poly(ethylene-co-1-butene)-block-polystyrene triblock copolymer (SEBS) matrices and is allowed to polymerize, phase separation at the nanometer level confines BZ in a way that can be controlled by the blending process, resulting in nanospherical polyBZ (polyBZ-NS) in the SEBS matrix. By simply changing the morphology of BZ and SEBS, through blending protocols ranging from sheet to electrospun micro-fibers and to electrospun core-sheath nanofibers, the sizes of polyBZ-NS so obtained vary from～150–500 nm, to ～80 nm, and to as low as ～12 nm, respectively. This shows a new method to obtain well-defined mono-disperse nanospherical thermoset resins with a controllable size by controlling blend conditions.     

Synthesis of novel bisphenol containing phthalazinone and azomethine moieties and thermal properties of cured diamine/bisphenol/DGEBA polymers

A novel bisphenol(1,2-dihydro-2-(4-((4-hydroxy)phenyliminomethylidene)phenyl)-4-(4-((4-(4-hydroxy)phenyliminomethylidene)phenoxy)phenyl)(2H)phthalazin-1-one, DPP) and a diamine(1,2-dihydro-2-(4-aminophenyl)-4-(4-(4-aminophenoxy)phenyl)(2H)phthalazin-1-one, DAP) were synthesized and characterized. The novel epoxy polymers containing phthalazinone and/or azomethine moieties were prepared by binary polymerization of DAP (or DPP) with diglycidyl ether of biphenyl A (DGEBA) and ternary polymerization of hybrid curing agents, DAP/DPP (DAP and DPP under different molar ratios) with DGEBA. The cure behaviors of these new epoxy systems were studied by dynamic differential scanning calorimeter (DSC) and Infrared (IR) scans. Especially, the activation energy of DAP/DGEBA calculated by Kissinger and Ozawa methods were 73.8 and 77.4 kJ/mol, respectively. For ternary epoxy system, it was found that hybrid curing agents of DAP/DPP exhibited significant associated effect on their reactivity towards the oxirane group. Glass transition temperatures (T_g's) of these new epoxy polymers were all above 150 °C from the results of DSC, and the initial thermal decomposition temperatures (T_d,5%'s) and integral procedure decomposition temperatures (IPDT's) of these new epoxy polymers are above 350 and 850 °C, respectively from results of thermogravimetric analyses (TGA). These results show that new epoxy polymers containing phthalazinone and/or azomethine moieties exhibited excellent thermal properties. Especially, thermal properties of the ternary epoxy polymers could be modified by changing the content of DAP and DPP. The linear relationships between char yield (Y_c,wt%) and the structural compositions of these new polymers (weight percentage of phthalazinone, azomethine and nitrogen, C/H weight ratio) were built.     

Bisphenol-A free dental polymeric materials

Bisphenol-A (BPA) is suspected to be an endocrine disrupter. Current polymeric dental materials are based on BPA derivatives, for example, Bisphenol-A diglycidylether methacrylate (Bis-GMA) which may leach out unreacted monomers and their degradation products. Consequently, the objective of the present work was to study the properties of BPA-free alternatives, for potential use in dental polymers and composites.

Experimental results indicated that BPA-free monomers from natural and commercial sources can replace Bis-GMA with adequate physical and mechanical properties of the final dental polymeric adhesives and composites.     

Cationic polymerization of diglycidly ether of bisphenol a resins initiated by benzylsulfonium salts

Benzylsulfonium salts are latent thermal cationic initiators that dissociate on heating to form benzyl cations that can initiate polymerizations. This paper describes the cure behavior of commercial epoxy resins using 1 -(p-methoxybenzyl)tetrahydrothiophenium hexafluoroantimonate [ 2 ]. The thermal cationic cure of bisphenol A diglycidylether (DGEBA) resins was investigated using differential scanning calorimetry (DSC). DSC revealed complex cure behavior as indicated by multiple exotherms. The resins cured rapidly at low initiator concentrations with gelation occuring in 3.5 and 1.5 min at 75 and 85 °C, respectively, at conversions of epoxy groups α = 0.2–0.3. Cure kinetics were evaluated from both dynamic and isothermal DSC measurements. The effects of initiator concentration, isothermal cure temperature and heating rate on the cure behavior and mechanisms, especially involving potential termination pathways, are discussed.     

UV light copolymerization of dimethyl vinylphosphonate with bisphenol A ethoxylate dimethacrylate

Dimethyl vinylphosphonate (DMVP), a very promising monomer, was copolymerized with acrylic monomer bisphenol A ethoxylate dimethacrylate (BEMA), in different molar ratios, by radical photoinitiated polymerization in the presence of photoinitiator Darocur 4265 (3 wt%) and in the absence of solvent. The UV light polymerization was an efficient method to obtain polymers in a green procedure. The molar ratio between DMVP and acrylic monomer BEMA varied between 1:1 and 5:1. The copolymers were characterized by FTIR, thermal analysis, water uptake and conductivity. From the ATR-FTIR spectra of DMVP-BEMA copolymers at the molar ratios of 1:1–5:1, it was observed that the intensity of P-O-C aliphatic band increased with increases in DMVP content. The synthesized copolymers showed good thermal stability in the range of 335–390 °C. DMVP:BEMA copolymer at 1:1 molar ratio displayed the highest stability, with decomposition temperature above 390 °C, the highest temperature in the series. The water uptake decreased with increases in DMVP content and this behavior was correlated with the ionic conductivity. Based on the Bode diagrams, the ionic conductivity of DMVP:BEMA of 1:1 molar ratio was 6.15 × 10^?8 S cm^?1 and that of DMVP:BEMA of 2:1 molar ratio was 3.69 × 10^?8 S cm^?1 which were considered promising as valuable conducting materials.     

Dietheramine from an alkaline-stable phosphinated bisphenol for soluble polyetherimides

This study focuses on economic preparation of a phosphinated dietheramine for soluble polyetherimides. For this purpose, a phosphinated dietheramine, 1,1-bis(4-(4-aminophenoxy)phenyl)-1-(6-oxido-6H-dibenz <c,e> <1,2> oxaphosphorin-6-yl)ethane (3), was prepared from the nucleophilic substitution of a alkaline-stable biphenol, 1,1-bis(4-hydroxyphenyl)-1-(6-oxido-6H -dibenz <c,e> <1,2> oxaphosphorin-6-yl)ethane (1), with 4-chloronitrobenzene using inexpensive potassium carbonate as catalyst, followed by catalytic hydrogenation. Light color, and foldable polyetherimides (PEIs) with good thermal stability, improved organo-solubility, and good flame retardancy were synthesized from the condensation of (3) with various aromatic dianhydrides in DMAc, followed by thermal imidization. Properties of the resulting PEIs were evaluated and compared with those of PEIs based on a commercially available dietheramine, 2,2-bis (4-(4-aminophenoxy)phenyl) propane (BAPP). The T_gs of the resulting PEIs range from 271 °C to 314 °C by dynamic mechanical analysis. The degradation temperatures (T_d 5%) range from 453 to 467 °C in N₂ atmosphere, and 435-451 °C in air atmosphere. The resulting PEIs also show good flame retardancy.     

双酚A型苯并二噁嗪树脂粘接性能研究

以环氧树脂(EP)、双马来酰亚胺(BDM)作为纯双酚A型苯并二噁嗪(BA-a)树脂的改性共聚单体,研究了不同改性BA-a体系的粘接性能和热稳定性能。结果表明:纯BA-a树脂与钢材之间的拉伸剪切强度为15.34 MPa,说明纯BA-a树脂具有作为胶粘剂的潜力;当m(BA-a)∶m(EP)∶m(BDM)=100∶60∶0或100∶27∶27时,改性BA-a体系的拉伸剪切强度为24.81 MPa或21.36 MPa,160℃时凝胶时间为150 min或20 min;改性BA-a体系的热稳定性能依次为BA-a/甲基四氢苯酐体系>BA-a/EP体系>BA-a/BDM体系>纯BA-a体系。     

Thermal degradation of bisphenol A polycarbonate by high-resolution thermogravimetry

Thermal degradation of bisphenol A polycarbonate (PC) has been studied in nitrogen and air from room temperature to 900 °C by high-resolution thermogravimetry (TG) with a variable heating rate in response to changes in the sample's degradation rate. A three-step (in nitrogen) or four-step (in air) degradation process of the PC, which was hardly ever revealed by traditional TG, has been found. The initial thermal degradation temperature of the PC is higher in nitrogen than in air, but the three kinetic parameters (activation energy E, decomposition order n, frequency factor Z) of the major degradation process are slightly lower in nitrogen. The average E, n and lnZ values determined by three methods in nitrogen are 154 KJ mol⁻¹, 0.8 and 21 min⁻¹, respectively, which are almost the same as those calculated by traditional TG measurements. © 1999 Society of Chemical Industry     

Viscosity and relaxation times temperature behaviour above the glass transition in some glassy polymers

We have performed mechanical and dielectric dynamic measurements above the glass-transition temperature range of two glassy-polymers: Poly(Hydroxyether of Bisphenol-A) and Poly(Carbonate of Bisphenol-A). From these measurements the temperature dependence of mechanical and dielectric mean relaxation times has been calculated. Results obtained have been compared with the viscosity temperature behaviour of the same polymers, which has been reported elsewhere. Both, relaxation times and viscosity temperature behaviour can well be described by Doolittle functional forms, exp{1/[_f(T-To)]}, with the same values of To but different values of the apparent free-volume expansion coefficient, _f. This difference in the experimental behaviour has been addresed in the framework of the free-volume model ideas. In this context, the different values of _f obtained from viscosity and relaxation times temperature behaviour can be understood assuming different values of critical volume controlling the molecular motions associated to viscosity and relaxation processes. Similar conclusions have also been obtained by means of a fine revision of the viscosity and relaxation times data of another two glassy-polymers: Poly(Arylate) and Poly(Sulfone of Bisphenol-A), reported previously.     

Post sulfonation of bisphenol A poly(arylene ethers)

In this study, bisphenol A polyetherimide (PEI) was sulfonated by a novel postsulfonation route using trimethylsilylchlorosulfonate. Different degrees of sulfonation were achieved by varying the mole ratio of the sulfonating agent to the PEI repeat unit and the reaction time. Comparison was made with respect to bisphenol A polysulfone (PSU) to study the influence of electron withdrawing group in the sulfonated poly(arylene ethers) (SPAE) backbone on sulfonation. Structural characterization of SPAE was conducted by ¹H‐NMR and FTIR spectroscopy. The enhanced reaction rate with PSU compared to PEI was attributed to the deactivation of bisphenol A unit due to the stronger electron withdrawing effect of imide group. The sulfonation of PEI was also carried out with chlorosulfonic acid for comparative study. The effects of degree of sulfonation on thermal and mechanical properties of SPAE‐s were studied by thermogravimetric analysis (TGA), differential scanning calorimetry (DSC) and a tensile testing machine. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Thermal properties of new bismaleimide resins containing hydrogen silsesquioxane and diallyl bisphenol A

Bismaleimide (BMI) resins modified with hydrogen silsesquioxane (HSQ) and diallyl bisphenol A (DABPA) (BMI‐HSQ‐DABPA resins) were prepared. DSC, FTIR, and TGA were used to characterize the curing behaviors, structures, and thermal properties of the BMI‐HSQ‐DABPA resins, respectively. The results showed that the glass transition temperatures and thermal stabilities of the cured BMI‐HSQ‐DABPA resins increased with the rise of the contents of HSQ. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Oxidation of bisphenol a polymers

Polysulfone, polycarbonate, and phenoxy resins were aged under thermal and ultraviolet light conditions. Thermoxidative processes in polysulfone and polycarbonate are of such minor significance as not to impart noticeable losses in these materials below 125°C. In phenoxy, however, thermal oxidation above 100°C results in rapid deterioration of all physical properties. This probably results from the low glass transition temperature of this polymer. Photo-oxidation rapidly degrades polysulfone. This appears to be a consequence of scission at the sulfone link. In polycarbonate, however, the only serious result of short-term irradiation is discoloration. For phenoxy resin, crosslinking through reactions at the hydroxyl group is the principal result of photo-oxidation. In all processes the bisphenol A portion of the three polymers appears to play only a small role.     

A new,nonphosgene route to poly(bisphenol a carbonate) by melt‐phase interchange reactions of alkylene diphenyl dicarbonates with bisphenol A

This article describes a new, nonphosgene method for the synthesis of poly(bisphenol A carbonate) (PC). The method involves three steps: the reaction of an aliphatic diol with phenyl chloroformate to form an alkylene diphenyl dicarbonate, the reaction of the alkylene diphenyl dicarbonate with bisphenol A to produce an aromatic–aliphatic polycarbonate, and the thermal treatment of the polycarbonate at 180–210°C under a stream of nitrogen with Ti(OBu)₄ to give PC and a cyclic alkylene carbonate. The method furnished low to moderate molecular masses of PC upon the complete elimination of the aliphatic moieties. The approach may be considered a new method, based on polycarbonate thermochemical degradation, for the synthesis of cyclic aliphatic carbonates. The obtained polymers were characterized by intrinsic viscosity and IR, ¹H‐NMR, and ¹³C‐NMR spectroscopy. The thermal treatment step was conducted in a glass reaction tube at 180–210°C under a stream of nitrogen, and the reaction was completed by heating to 250°C. In the thermal treatment step, semisolid effluents composed of cyclic alkylene carbonates were formed and subsequently eliminated from the reaction mixture. Heating to 250°C under nitrogen or under a dynamic vacuum furnished the pure aromatic PC residue. This intrachange reaction provides a flexible method for the synthesis of polycarbonates with alkylene diols containing two or three methylene groups, from which the pure PC homopolymer can be prepared. The potential of this approach was demonstrated by the successful synthesis of PC homopolymer from five different polycarbonates with a bisphenol A unit linked to 1,2‐propylene, 1,3‐propylene, 2‐methyl‐1,3‐propylene, 2,2‐dimethyl‐1,3‐propylene, and 1,3‐butylene as the alkane chains. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Mechanical and thermal properties of bisphenol A-based cyanate ester and diallyl phthalate blends

Cyanate ester resins are a high performance class of compounds. They have excellent mechanical properties, dielectric properties and thermal properties; however, their major drawback is their brittleness. An attempt was made to improve the impact strength of the cyanate ester resin. In the present study a commonly used cyanate resin, bisphenol A dicyanate (BADCy), was modified by the addition of diallyl phthalate (DAP) and was cured with benzoyl peroxide. The properties of the blends such as thermal and mechanical properties were investigated in detail by scanning electron microscope, dynamic mechanical analysis, thermogravimetric analysis, and mechanical measurement. The results indicate that the addition of the appropriate amount of DAP can effectively improve the impact toughness and the flexural strength while sacrificing the thermal properties of the blends. The maximum impact strength and flexural strength were observed on addition of 15 phr DAP content. However, the thermal stability of the blends was found to be lower than that of the unmodified BADCy resin.     

Preparation,curing kinetics,and thermal properties of bisphenol fluorene epoxy resin

Diglycidyl ether of 9,9‐bis(4‐hydroxyphenyl) fluorene (DGEBF) was synthesized to introduce more aromatic structures into an epoxy resin system. The structure of DGEBF was characterized with Fourier transform infrared and ¹H‐NMR. 4,4′‐Diaminodiphenylmethane (DDM) was used as the curing agent for DGEBF, and differential scanning calorimetry was applied to study the curing kinetics. The glass‐transition temperature of the cured DGEBF/DDM, determined by dynamic mechanical analysis, was 260°C, which was about 100°C higher than that of widely used diglycidyl ether of bisphenol A (DGEBA). Thermogravimetric analysis was used to study the thermal degradation behavior of the cured DGEBF/DDM system: its onset degradation temperature was 370°C, and at 700°C, its char yield was about 27%, whereas that of cured DGEBA/DDM was only 14%. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

Preparation and properties of bisphenol A polyetherketoneketone based phthalonitrile resins

A promising high temperature phthalonitrile (PN) resin composed of a polyetherketoneketone (PEKK) core bridged by two bisphenol A linkers and end capped with PN groups is presented. This PEKK-PN resin was characterized via differential scanning calorimetry, thermogravimetric analysis, proton nuclear magnetic resonance spectroscopy, scanning electron microscopy, dynamic mechanical analysis, attenuated total reflection Fourier transform infrared, and rheometry. The PEKK-PN resin was evaluated with two different compositions containing 1) 70:30 PEKK-PN to bisphenol A PN (n = 0) and 2) pure PEKK-PN. The 70:30 PEKK-PN resin was mixed with bis[4-(3-aminophenoxy)phenyl]sulfone and exhibited a melt viscosity of 271 cP, much lower than the 657 cP viscosity of the pure PEKK-PN mixture. Void-free PEKK-PN polymers were easily prepared by degassing and curing up to 380°C, resulting in fully crosslinked networks exhibiting thermal stability above 500°C and a 75% char yield. Additionally, the cured PEKK-PN polymer samples displayed good mechanical integrity retaining 50% stiffness at 300°C. This combination of properties suggests these new PEKK-PN resins are excellent materials for high temperature thermosets in composite applications.     

Influence of Nano-Inorganic Particles on Properties of Epoxy Nanocomposites

Solution polymerization of Bisphenol-A and Epichlorohydrine gives epoxy resin. Spray pyrolysis technique was found to be promising method for synthesis of nanomaterials like CaCO₃ of different sizes (10, 15, and 18 nm). The nanomaterial (2 to 10 mass % loading) was added at the time of resin formation. Mechanical stirring as well as an ultrasonication technique were used for uniform distribution of nanomaterials inside the resin. The effect of nanomaterials on thermal behaviors like curing time and glass transition temperature (Tg) were studied. Addition of nanomaterials accelerates the rate of curing of epoxy resin during composite formation. Moreover, addition of nanomaterial doesn't show any consequent change in Tg of epoxy composite but cross-linking density changes linearly. The rheological parameters like viscosity and torque were recorded on a Brookfield viscometer and correlated with M = CS^α and τ = κ(γ)ⁿ.     

Crazing,yielding, and fracture of polymers. I. Ductile brittle transition in polycarbonate

Most thermoplastics far below their glass transition give a brittle fracture when de-formed in uniaxial tension. Bisphenol-A polycarbonates are an exception and deform in a ductile manner. However, it has been observed in Izod impact studies of notched samples that the mode of failure changes from a ductile to a brittle fracture on annealing samples below T_g. It has been found that, when notched samples are stressed, a Griffith type flaw is formed under the notch. The criterion for the ductile brittle transition is evaluated in terms of σG (the stress required to propagate the Griffith flaw), and σ_y, the yield stress for the polymer. It has been found that the density and yield stress for the samples annealed at various temperatures are dependent upon previous thermal history and in particular on the molecular weíAght. On the basis of these measurements, it is concluded that many of the so-called anomalous effects observed with polycarbonate can be explained.