Quantitative study of the annealing of poly(vinyl chloride) near the glass transition

Poly(vinyl chloride) displays a normal DSC of DTA curve for the glass transition when quenched from above its T_g. However if cooled slowly or annealed near the glass transition temperature, a peak appears on the DSC or DTA curve at the T_g. In this paper quantitative studies of the time and temperature effects on the production of this endothermal peak during the annealing of PVC homopolymer and an acetate copolymer are presented. The phenomenon conforms to the Williams, Landell, and Ferry equation for the relaxation of polymer chains, the rate of the peak formation becoming negligible at more than 50°C below T_g. The energy difference between the quenched and annealed forms is small. For a PVC homopolymer annealed 2 hr at 68°C, which is T_g ?10°C, the difference is 0.25 cal/g. For a 13% acetate copolymer of PVC similarly annealed, the difference is 0.36 cal/g. The measured rates of the process give a calculated activation energy of 13–14 kcal/mole for PVC homopolymer and copolymer. This appearance of a peak on the T_g curve for a polymer when annealed near the glass temperature appears to be a general phenomenon.     

Enthalpy relaxation of filled copolymers

Excess enthalpy following annealing at various periods of time at T_g ?10°C was measured by differential scanning calorimetry of electrophotographic toners, copolymers of styrene and butyl methacrylate containing carbon black. An approximate equilibrium enthalpy relaxation after annealing the pure copolymers for one month was 3.30 kJ/kg for a copolymer with 66.5% styrene and 2.72 kJ/kg for a copolymer containing 49.8% styrene. The rate of enthalpy relaxation was reduced by increasing the styrene content of the pure copolymer. The incorporation of a carbon black with high surface area reduces the rate of enthalpy relaxation, increasing in effectiveness with butyl methacrylate concentration.     

Thermomechanical behavior of poly(carborane–siloxane)s containing ?CB5H5C? cages

The thermomechanical spectra of two new carborane–siloxane polymers containing five-boron carborane cages in the backbones are reported and discussed. The polymers are the homopolymer, HO? [Si(CH₃)₂? CB₅H₅C? Si(CH₃)₂? O? ]_nH, and the random copolymer with 20 mole-% of the ten-boron meta-carborane analogue, ? [Si(CH₃)₂? CB₁₀H₁₀C? Si(CH₃)₂? O? ]. The mechanical spectra (～1 cps) were determined from ?180° → +625° → ?180°C (ΔT/Δl = 3.6°C/min for T > 25°C and 2°C/min for T < 25°C) using the semimicro thermomechanical technique, torsional braid analysis. In nitrogen, both polymers displayed secondary transitions at ?140°C. The glass transition (T_g) for the homopolymer was ?60°C and for the copolymer was ?52°C. The homopolymer had a melting point of +70°C. The copolymer was amorphous. The high-temperature stability in nitrogen of both polymers appeared to be identical; thermal stiffening commenced at 400°C, continued to 625°C, and resulted in materials that were typical of highly crosslinked resins. In air, the homopolymer began to stiffen catastrophically near 270°C, while the copolymer began to stiffen similarly nearly 50°C higher. The intrinsic elastomeric nature together with the thermomechanical results prompted further study of the copolymer. Thermomechanical cycling studies in nitrogen and air are reported for the copolymer. Some correlating TGA and DTA are also discussed.     

Polymerized high internal‐phase emulsions: Properties and interaction with water

The synthesis and characterization of novel polymerized high internal‐phase emulsions (polyHIPE) materials are described. Homogeneous, highly porous, low‐density, open‐cell crosslinked copolymers were prepared by polymerizing the continuous phase of HIPE containing styrene and varying amounts of 2‐ethylhexyl methacrylate. The glass transition temperatures (T_gs) of the homopolymers were similar to the literature values, but the copolymer T_gs were lower than expected. These results indicate that the copolymer composition is richer in 2‐ethylhexyl methacrylate than the feed composition. The homopolymer moduli, calculated from the foam moduli, were similar to the literature values. The influence of composition and surface treatment on the water absorbed by the foams was investigated. For example, washing a polyHIPE based on poly(ethylhexyl acrylate) in water at 70°C increased water absorption because of the removal of the residual salt. Adding a fluorinated comonomer to the HIPE reduced hydrophilicity and, thus, water absorption. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 2018–2027, 2002; DOI 10.1002/app.10555     

Poly(methyl methacrylate-co-acrylonitrile)

Stable macroradicals of methyl methacrylate were prepared by the azobisisobutyronitrile-initiated polymerization of methyl methacrylate in hexane whose solubility parameter value (δ) differed from that of the macroradical by more than 1.8 hildebrand units and in 1-propanol at temperatures below its theta temperature (84.5°C). The rates of heterogeneous polymerization in hexane and 1-propanol were much faster than that of the homogeneous polymerization in benzene. Stable macroradicals were not obtained in benzene which was a good solvent nor at temperatures above the glass transition temperature (T_t) of the macroradicals. Thus, stable macroradicals of butyl methacrylate (T_g20°C) and and methyl acrylate (T_g3°C) were not obtained at a polymerization temperature of 50°C. Good yields of block copolymers of methyl methacrylate and acrylonitrile were obtained by the addition of acrylonitrile to the methyl methacrylate macroradical in methanol, ethanol, 1-propanol and hexane at 50°C. The rate of formation of the block copolymer decreased in these poor solvents as the differences between the solubility parameter of the solvent and macroradical increased.The block copolymer samples prepared at temperatures of 50°C and above were dissolved in benzene which is a non-solvent for acrylonitrile homopolymer, but is a good solvent for poly(methyl methacrylate) and the block copolymer. The presence of acrylonitrile and methyl methacrylate in the benzene-soluble macromolecule was demonstrated by pyrolysis gas chromatography, infra-red spectroscopy and differential thermal analysis.     

Investigation of thermal behavior of poly(2‐hydroxyethyl methacrylate‐co‐itaconic acid) networks

The thermal behavior of poly(2‐hydroxyethyl methacrylate) [PHEMA] homopolymer and poly(2‐hydroxyethyl methacrylate‐co‐itaconic acid) [P(HEMA/IA)] copolymeric networks synthesized using a radiation‐induced polymerization technique was investigated by differential scanning calorimetry, thermogravimetric analysis, and Fourier transform infrared spectroscopy. The glass‐transition temperature (T_g) of the PHEMA homopolymer was found to be 87°C. On the other hand, the T_g of the P(HEMA/IA) networks increased from 88°C to 117°C with an increasing amount of IA in the network system. The thermal degradation reaction mechanism of the P(HEMA/IA) networks was determined to be different from the PHEMA homopolymer, as confirmed by thermogravimetric analysis. It was observed that the initial thermal degradation temperature of these copolymeric networks increased from 271°C to 300°C with IA content. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 1602–1607, 2007     

Morphologies of polybutylacrylate/poly(styrene‐co‐methyl methacrylate) latex prepared by starved emulsion polymerization Part I. Thermodynamics equilibrium morphology

Heterogeneous latexes were prepared by a semicontinuous seeded emulsion polymerization process under monomer starved conditions at 80 °C using potassium persulfate as the initiator and sodium dodecyl sulfate as the emulsifier. Poly(butyl acrylate) latexes were used as seeds. The second‐stage polymer was poly(styrene‐co‐methyl methacrylate). By varying the amounts of methyl methacrylate (MMA) in the second‐stage copolymer, the polarity of the copolymer phase could be controlled. Phase separation towards the thermodynamic equilibrium morphology was accelerated either by ageing the composite latex at 80 °C or by adding a chain‐transfer agent during polymerization. The morphologies of the latex particles were examined by transmission electron microscopy (TEM). The morphology distributions of latex particles were described by a statistical method. It was found that the latex particles displayed different equilibrium morphologies depending on the composition of the second‐stage copolymers. This series of equilibrium morphologies of [poly(butyl acrylate)/poly(styrene‐co‐methyl methacrylate)] (PBA/P(St‐co‐MMA)) system provides experimental verification for quantitative simulation. Under limiting conditions, the equilibrium morphologies of PBA/P(St‐co‐MMA) were predicted according to the minimum surface free energy change principle. The particle morphology observed by TEM was in good agreement with the predictions of the thermodynamic model. Therefore, the morphology theory for homopolymer/homopolymer composite systems was extended to homopolymer/copolymer systems. © 2002 Society of Chemical Industry     

Thermal properties of poly(tetramethyl-p-silphenylene siloxane) and (tetramethyl-p-silphenylene siloxane-dimethyl siloxane) copolymers

Some physical properties of poly(tetramethyl-p-silphenylene siloxane) homopolymer and random block copolymers of tetramethyl-p-silphenylene siloxane-dimethyl siloxane have been determined and correlated with polymer structure. Differential scanning calorimetry (d.s.c.), differential thermal analysis (d.t.a.), density gradient column measurements and optical hot stage melting point determination and diluent techniques were used. The thermodynamic melting temperature of the homopolymer was estimated to be 160°C and its heat of fusion, ΔH_u, found to be 54.4 J/g (13 cal/g or 2710 cal/mol of monomer repeat units). Its limiting glass transition temperature, T_g, was ?20°C. T_g of the copolymer was found to vary almost monotonically with increasing dimethyl siloxane (DMS) content ranging from ?20° (0% DMS) to just above ?123°C, for pure DMS polymer. The copolymer melting temperature was found to increase as the fraction of the crystalline (hard) TMPS constituent was increased. Based upon copolymer theory and extrapolated melting point data, it was estimated that the block size of soft DMS component in the copolymer most probably consists of twelve monomer units distributed amongst TMPS sequences of varying length.     

High-quality N-substituted maleimide for heat-resistant methacrylic resin

A preparation procedure for colorless, transparent N-substituted maleimide of high quality which can provide heat-resistant transparent methacryl resins was developed. N-Alkylmaleimide, the alkyl substituent of which was composed of 2 to 4 carbons, is employed, giving a polymer with enhanced heat distortion temperature (HDT) because of the higher T_g. The advantages of relatively low melting points and high vapor pressure of N-alkylmaleimide can be used for the preparation of a high-quality product with purification of the monomer by distillation. N-Isopropylmaleimide (IPMI), which fulfills these requirements, is especially useful as a monomer for transparent resins. IPMI was synthesized in a high-yield using a mixture of orthophosphoric acid and orthophosphoric acid-isopropylamine salt as catalyst. IPMI, the purity of which is 99.9 wt % or above, contains 100–200 ppm of N-isopropylmaleamic acid, maleic anhydride, dimethylmaleic anhydride, solvent, and water. IPMI, which solidifies at 25.8°C, is obtained as a colorless liquid and is freely soluble in common monomers such as methyl methacrylate (MMA), styrene (St), and acrylonitrile (AN). The obtained IPMI showed excellent thermal stability, and no quality change was observed after heating for 100 h at 50°C. The copolymer of MMA and IPMI exhibited the same YI value as a measure of coloration, and almost the same transparency as the homopolymer of MMA. An increase in IPMI content in the copolymer by 1 mol % increased the polymer T_g by 0.8°C. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 63: 1055–1062, 1997     

Preparation of poly(styrene‐co‐isobornyl methacrylate) beads having controlled glass transition temperature by suspension polymerization

The styrene (St) and isobornyl methacrylate (IBMA) random copolymer beads with controlled glass transition temperature (T_g), in the range of 105–158°C, were successfully prepared by suspension polymerization. The influence of the ratios of IBMA in monomer feeds on the copolymerization yields, the molecular weights and molecular weight distributions of the produced copolymers, the copolymer compositions and the T_gs of these copolymers was investigated systematically. The monomer reactivity ratios were r₁ (St) = 0.57 and r₂ (IBMA) = 0.20 with benzyl peroxide as initiator at 90°C, respectively. As the mass fraction of IBMA in monomer feeds was about 40 wt %, it was observed that the monomer conversion could be up to 90 wt %. The fractions of IBMA unit in copolymers were in the range of 35–40 wt % and T_gs of the corresponding copolymers were in the range of 119.6–128°C while the monomer conversion increased from 0 to greater than 90 wt %. In addition, the effects of other factors, such as the dispersants, polymerization time and the initiator concentration on the copolymerization were also discussed. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Synthesis and characterization of hydrophilic copolymers of maleimide derivatives with 2‐hydroxyethyl methacrylate: electrochemical and thermal behavior

BACKGROUND: The high‐technology industries have been the driving force in the development of new synthetic polymers that combine thermal stability with specific functional properties. In this study p‐chlorophenylmaleimide, p‐hydroxyphenylmaleimide and p‐nitrophenylmaleimide (R‐PhMI) with 2‐hydroxyethyl methacrylate (HEMA) were synthesized by free radical polymerization to obtain hydrophilic polymers, in order to study the effect of the p‐chloroaryl, p‐hydroxyaryl or p‐nitroaryl group on the copolymer composition, electrochemical behavior and thermal properties. RESULTS: The thermal behavior was correlated with the copolymer composition and functional groups, maleimide derivatives, on the copolymers. Thermal decomposition temperature (TDT) and glass transition temperature (T_g) were influenced by the functional groups of R‐PhMI moiety on the copolymer. The polymers showed an electrochemically irreversible reduction process under the conditions tested. CONCLUSION: Poly[(p‐chloromaleimide)‐co‐(2‐hydroxyethyl methacrylate)] copolymer shows a higher TDT than poly[(p‐hydroxymaleimide)‐co‐(2‐hydroxyethyl methacrylate)] or poly[(p‐nitromaleimide)‐co‐(2‐hydroxyethyl methacrylate)] (NPHE). T_g decreases in going from nitro to hydroxyl to chloro groups. The NPHE copolymer shows a lower stability, losing weight at 200 °C. The NPHE copolymer shows a well‐defined reduction wave which is similar to those of the other copolymers and it also shows an additional quasi‐reversible reduction wave corresponding to the nitrobenzene group. Copyright © 2009 Society of Chemical Industry     

Improvement in Low Temperature Izod Impact Strength of SAN/ASA/HNBR Ternary Blends Considering Competing Effects of Glass Transition Temperature and Compatibility

The competing effects of glass transition temperature (T_g) and compatibility on the low temperature Izod impact toughness of styrene–acrylonitrile copolymer/acrylonitrile–styrene‐acrylate terpolymer (SAN/ASA, 75/25, w/w) blends were investigated by using a series of hydrogenated nitrile butadiene rubbers (HNBRs) with different acrylonitrile (AN) contents. The results showed that the HNBR with AN mass content ranging from 21% to 43% had good compatibility with polymer matrix and exhibited dramatic toughening effect at 25°C. Owing to their low T_gs, only the HNBRs (AN = 21% and 25%) remained favorable toughening effect at 0 and ?30°C, respectively. Furthermore, the HNBR with 0% AN content was represented by butadiene rubber (BR). Although, BR has an extremely low T_g (?94.5°C), it is incompatible with polymer matrix, and then could not toughen the material at three temperatures (?30, 0, and 25°C, respectively). Various characterizations including solubility parameters, scanning electron microscopy (SEM), dynamic mechanical thermal analysis (DMTA), Fourier transform infrared (FTIR) spectroscopy, and so on were carried out to elucidate the toughening mechanism. J. VINYL ADDIT. TECHNOL., 25:225–235, 2019. © 2018 Society of Plastics Engineers     

Diffusion of p-aminoazobenzene in SBS block copolymer

The temperature dependence of p-aminoazobenzene diffusion in a styrene–butadiene–styrene (SBS) triblock copolymer film, prepared from a toluene or ethyl acetate solution, was investigated in the temperature region from 40° to 110°C by using a sublimative desorption method. Parallel studies on the mechanical relaxations of this copolymer were carried out in the same temperature range to be compared with the diffusion data. The penetrant-diffusion characteristics were interpreted in terms of Fujita's free-volume theory with due consideration of the different SBS domain morphology. The value of B_d, defined as the diffusional volume ratio of a penetrant molecule to a segment, was then estimated as 0.45–0.55 above the T_g of the polystyrene phase or 0.7 below that temperature. Interestingly, sigmoidal desorption appeared in the range under the T_g of the polystyrene phase for film cast from ethyl acetate; the anomalous behavior was considered to reflect the slow relaxation process of the copolymer chain ascribable to the predominant exposure of the polystyrene phase on the film surface.     

Synthesis of random or tapered solution styrene–butadiene copolymers in the presence of sodium dodecylbenzene sulfonate as a polar modifier

Random or tapered solution styrene–butadiene copolymer (SSBR) is very difficult to prepare in an isothermal batch process without the use of polar modifiers because of the diverse reactivity ratios of the styrene and the butadiene in hydrocarbon solvents. In the presence of polar modifiers, the random SSBR can be synthesized by anionic living polymerization with the variety of microstructures, which results in the change of glass transition temperature (T_g). This article will discuss the use of sodium dodecylbenzene sulfonate as a polar modifier in isothermal batch process that controls the microstructure of the SSBR resulting in a random as well as tapered SSBR with low T_g (?67°C to ?80°C). The T_g of SSBR was controlled by the styrene content rather than the microstructure of polybutadiene. Physical properties of SSBR compounding were discussed for tire tread applications. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Glass‐transition temperatures and rheological behavior of methyl methacrylate–styrene random copolymers

Poly(methyl methacrylate‐ran‐styrene) copolymers were synthesized under monomer‐starved conditions by emulsion copolymerization. The glass‐transition temperatures (T_g's) of the copolymers were measured by differential scanning calorimetry (DSC) and torsional braid analysis (TBA). The results showed that the methyl methacrylate–styrene random copolymers produced an asymmetric T_g versus composition curve, which could not even be interpreted by the Johnston equation with different contributions of dyads to the T_g of the copolymer considered. A new sequence distribution equation concerning different contributions of triads was introduced to predict the copolymer's T_g. The new equation fit the experimental data exactly. Also, the T_g determined by TBA (T_gTBA) was higher than the one determined by DSC (T_gDSC) and the difference was not constant. The rheological behavior of the copolymers was also studied. T_gTBA ? T_gDSC increased with increasing flow index of the melt of the copolymer, and the reason was interpreted. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 2891–2896, 2003     

Nonequilibrium particle morphology development in seeded emulsion polymerization. II. Influence of seed polymer Tg

Most structured latex particles are formed in the nonequilibrium state as a result of the reaction kinetics proceeding faster than the phase separation kinetics. Of the many factors controlling such morphologies, the polarity and glass transition temperature (T_g) of the seed polymer are important. In order to study the direct effect of the seed polymer T_g on morphology, we produced a series of poly(methyl methacrylate)/poly(methyl acrylate) seed copolymers having glass points between 52 and 98°C, and particle sizes between 320 and 390 nm. We then used styrene as a second‐stage monomer reacting in both the batch and semibatch process modes, and utilized reaction temperatures (T_r) between 50 and 70°C. Monomer feed rates were varied between flooded and starve‐fed conditions. The equilibrium morphology for these composite particles is an inverted core–shell structure, but all morphologies obtained in our experiments were nonequilibrium. Under monomer starved conditions only core–shell structures were formed when (T_r?T_g) < 0, but significant penetration of the polystyrene into the acrylic core occurs when (T_r?T_g) > 15°C. These results are reasonably well predicted using the “fractional penetration” model developed earlier. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 905–915, 2003     

Preparation and characterization of biodegradable polymer blends from poly(3‐hydroxybutyrate)/poly(vinyl acetate)‐modified corn starch

Biodegradable polymer blends prepared by blending poly(3‐hydroxybutyrate) (PHB) and corn starch do not form intact films due to their incompatibility and brittle behavior. For improving their compatibility and flexibility, poly(vinyl acetate) (PVAc) was grafted from the corn starch to prepare the PVAc‐modified corn starch (CSV). The resulting CSV consisted of 47.2 wt% starch‐g‐PVAc copolymer and 52.8 wt% PVAc homopolymer and its structure was verified by FT‐IR analysis. In comparison with 35°C of the neat PVAc, the glass transition temperature (T_g) of the grafted PVAc chains on starch‐g‐PVAc was higher at 44°C because of the hindered molecular mobility imposed from starch on the grafted PVAc. After blending PHB with the CSV, structure and thermal properties of the blends were investigated. Only a single T_g was found for all the PHB/CSV blends and increased with increasing the CSV content. The T_g‐composition dependence of the PHB/CSV blends was well‐fitted with the Gordon‐Taylor equation, indicating that the CSV was compatible with the PHB. In addition, the presence of the CSV could raise the thermal stability of the PHB component. It was also found that the presence of the PHB and PVAc components would not hinder the enzymatic degradation of the corn starch by α‐amylase. POLYM. ENG. SCI., 55:1321–1329, 2015. © 2015 Society of Plastics Engineers     

A new class of transparent polymeric materials. II. Synthesis and properties of poly(N-cyclohexylmaleimide-alt-isobutene) modified with lauryl methacrylate

Transparent polymeric materials with high heat resistance and low water absorption were designed based on the alternating copolymers of N-substituted maleimide (RMI) with isobutene (IB). The N-substituent of the maleimide significantly affected the glass transition temperature (T_g) and water absorption of the copolymers. Poly(N-cyclohexylmaleimide-alt-JB) [poly(CHMI-IB)] showed a T_g value as high as 192°C and relatively low water absorption. Furthermore, the incorporation of a small amount of lauryl methacrylate in the copolymers was confirmed to reduce the water absorption of the copolymer drastically, although it decreased the T_g of the copolymers at the same time. Poly(CHMI-IB), containing 4 mol % lauryl methacrylate, showed a good balance of excellent transparency, high heat resistance, acceptable mechanical properties, and low water absorption. The heat deflection temperature was as high as 141°C. The water absorption at 23°C after immersion for 14 days was 0.56% and the dimensional change after 7 days was 0.06%. They are half and one-quarter of those of poly(methyl methacrylate), respectively. © 1996 John Wiley & Sons, Inc.     

Synthesis and characterization of heat‐resistant N‐phenylmaleimide–styrene–maleic anhydride copolymers and application in acrylonitrile–butadiene–styrene resin

The heat‐resistant copolymer of N‐phenylmaleimide (NPMI)–styrene (St)–maleic anhydride (MAH) was synthesized in xylene at 125°C with di‐tert‐butyl diperoxyterephthalate as an initiator. The characteristics of the copolymer were analyzed by Fourier transform infrared spectroscopy, nuclear magnetic resonance spectroscopy (¹H‐NMR and ¹³C‐NMR), gel permeation chromatography, and elemental analysis. The ¹³C‐NMR results show that the copolymer possessed random sequence distribution; this was also supported by the differential scanning calorimetry experiment, in which a single glass‐transition temperature (T_g) of 202.3°C was observed. The thermal stability and degradation mechanism of the copolymer were investigated by thermogravimetric analysis. Using the Kissinger equation and Ozawa equation, we proved a nucleation controlling mechanism with an apparent activation energy of 144 kJ/mol. Blends of acrylonitrile–butadiene–styrene with the NPMI–St–MAH copolymer with various contents were prepared with a twin‐screw extruder processes. The mechanical and thermal properties of the materials, such as the tensile and flexural strength, T_g's, and Vicat softening temperatures, were all enhanced with the addition of the modifier, whereas the melt flow index decreased. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Thermal analysis of styrene–alkyl methacrylate polymers. I. Glass transition temperatures

The glass transition temperatures (T_g's) of several polystyrenes and styrene–alkyl methacrylate copolymers and terpolymers were measured using thermomechanical analysis (TMA) and differential scanning calorimetry (DSC). The polymers studied had number-average molecular weights from 3000 to 250,000 g/mole. The results indicate that the composition dependence of the T_g's for the copolymers and terpolymers can be satisfactorily described by a general Fox equation. In general, the measured T_g's of the copolymer and terpolymer samples depend more on the steric effects of the constituent pendent groups than on their molecular weights. The chain flexibility rather than the size of the pendent group is the determining factor in the glass transition properties of the styrene polymers.