Phase separation,physical properties and melt rheology of a range of variously transesterified amorphous poly(ethylene terephthalate)–poly(ethylene naphthalate) blends

Amorphous, partially transesterified poly(ethylene terephthalate)/poly(ethylene naphthalate) (PET/PEN) blends of different levels of transesterification and blend composition were investigated in terms of resultant phase behavior, thermal transitions, and melt rheological properties. Intrinsic viscosities of the lowest transesterified material were found to be significantly below those of a physical blend of an identical composition, but at higher levels of transesterification, there was little difference. This was similarly found in melt rheometry measurements, where the zero‐shear rate viscosity of the low and highly transesterified mixtures were similar. Both solution and melt rheometry indicated that the molecular weight decreased by thermal degradation from processing. This is believed to play an important role in determining the final molecular architecture and properties. For similar levels of ester interchange, there was a minimum observed in zero shear melt viscosity at around 40 wt % PEN. This is likely due to competition between the slightly transesterified copolymer chains having poorer packing in the melt and reduced entanglement. Differential scanning calorimetry and dynamic mechanical thermal analysis were used to investigate the phase behavior of partially and fully transesterified blends. Results for the glass transition of the highly transesterified blends were compared with the theoretical values calculated from the Fox equation and were found to be close, although slightly lower. A correlation between the melting temperature of the blend and the degree of transesterification was shown to exist. This correlation can be used to estimate the degree of ester exchange reaction from these melting transitions. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 1556–1567, 2002     

增韧PC/聚酯合金研究

对增韧聚碳酸酯(PC)/聚酯[聚对苯二甲酸乙二醇酯(PET)和聚对苯二甲酸丁二醇酯(PBT)]合金进行了研究,结合合金的相形貌结果,分别选择PC和聚酯是连续相的合金进行了研究,同时对比了相同树脂比例下PC/PET和PC/PBT之间性能的差别。增韧剂选择甲基丙烯酸甲酯-丁二烯-苯乙烯共聚物(MBS)或MBS和接枝环氧基团的丙烯酸酯类增韧剂(X-GM A)复配物。结果表明,使用相同的增韧剂,PC是连续相的情况下,冲击强度更高,相同树脂比例情况下,PC/PET合金冲击强度比PC/PBT的差,拉伸和弯曲强度相差不大,PC/PET合金的熔体稳定性能比PC/PBT的差,PC是连续相合金的熔体稳定性比聚酯是连续相的要好,含有X-GMA的合金熔体稳定性能更好,这些结果和酯基的热分解、PET分子链运动活性比PBT的差以及酯交换程度的差异等有直接的关联。     

Structure‐property relationships of blends of polycarbonate

Three grades of bisphenol‐A polycarbonate—high molecular weight linear, high molecular weight branched and low molecular weight linear—and their blends have been studied by GPC, DMTA, DSC, rheometry and impact measurements. The molecular weight distribution of the blends agred with that predicted from the component's distributions, indicating that no transesterification reactions had occurred during melt blending. The T_g of the blends varied with blend composition according to the Fox equation and was related to the reciprocal molecular weight predicted by the Flory‐Fox equation. The low shear rate viscosity of the blends agreed with a logarithmic rule of mixtures and showed power‐law dependence on the weight average molecular weight. At higher shear rates, shear thinning was observed. The steady shear viscosity correlated well with the dynamic viscosity, as suggested by the Cox‐Merz relation. The stress relaxation behavior of the melt was very sensitive to the blend composition and molecular weight and correlated well with the real modulus. Temperature studies of the dart impact energy showed that only the low molecular weight polymer underwent a brittle‐duetile transition at ea ?30°C and that all the blends were tough at room temperature. The enhanced stress triaxiality inherent in the notched lzod test caused the impact strenght at room temperature to decrease almost linealy with blend composition.     

Transesterification reaction kinetics of poly(ethylene terephthalate/poly(ethylene 2,6‐naphthalate) blends

The transesterification reaction of poly(ethylene terephthalate)/poly(ethylene 2,6‐naphthalate) blends during melt‐mixing was studied as a function of blending temperature, blending time, blend composition, processing equipment, and different grades of poly(ethylene terephthalate) and poly(ethylene 2,6‐naphthalate). Results show that the major factors controlling the reaction are the temperature and time of blending. Efficiency of mixing also plays an important role in transesterification. The reaction kinetics can be modeled using a second‐order direct ester–ester interchange reaction. The rate constant (k) was found to have a minimum value at an intermediate PEN content and the activation energy of the rate constant was calculated to be 140 kJ/mol. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 2422–2436, 2001     

Synthesis and rheological properties of poly(styrene-co-butyl methacrylate) as an ink vehicle

Poly(styrene-co-butylmethacrylate) as an ink vehicle was synthesized using free radical polymerization. The molecular weights and monomer ratios in copolymers were determined. According to the results, the molecular weight could be controlled by the addition of a chain transfer agent and the copolymer ratio was nearly the same as the mole ratio of the monomer feed. The effect of the copolymer ratio on the rheological property was also studied. The polymer melt resembled a very viscous Newtonian fluid at a rate above the critical shear rate. Also, it is possible to synthesize a copolymer whose activation energy value is independent of the shear rate. The viscosity and melt behavior of the copolymer can be controlled with proper blending.     

Properties of a branched polyester ether as a function of the preparation method

Properties of a branched polyester ether elastomer have been examined by using two widely differing preparation methods: (1) prepared to final molecular weight by using melt polycondensation (MP) and (2) prepared to an intermediate molecular weight by using melt polycondensation followed by solid phase polycondensation to the final molecular weight (SP). Differences in T_m were attributed to annealing during the SP process and also to apparent changes in monomer sequence distribution in the polymer chains. Crystallization during cooling (DSC) and melt viscosity appeared to be solely a function of molecular weight rather than of preparation history. Molecular weight distribution was exponentially dependent on viscosity average molecular weight for the MP samples, but the distribution was linearly dependent for the SP case which more nearly represents equilibrium conditions. Polymer mechanical properties did not vary much in spite of the pronounced differences observed.     

Depolymerization of nylon 6 waste fibers

The depolymerization of nylon 6 was carried out with various solvents, such as formic acid, hydrochloric acid, and sulfuric acid, followed by heating under reflux for different times. From the polymer dissolved and refluxed in formic acid, degradation products with different ranges of molecular weights were collected by fractional precipitation, with small lots of distilled water added as a nonsolvent. The characterization of different fractions was carried out by the measurement of the viscosity‐average molecular weight, the number‐average molecular weight, and the number of amino end groups. The presence of the monomer, aminocaproic acid, was confirmed by thin‐layer chromatography in the case of hydrochloric acid treated nylon 6. With a strongly acidic ion‐exchange resin, the monomer was separated in its purest form, and the melting point was noted. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 186–190, 2006     

Synthesis of poly(dodecyl methacrylate)s and their drag‐reducing properties

Dodecyl methacrylate was synthesized as the intermediate monomer for the preparation of poly(dodecyl methacrylate)s, which were synthesized with emulsion polymerization techniques. The intrinsic viscosities were measured, and the viscosity‐average molecular weights were calculated. Polymers of dodecyl methacrylate with ultrahigh molecular weights (viscosity‐average molecular weight > 10⁷) were synthesized through orthogonal experiments. The drag‐reduction properties of these polymers were studied in kerosene. The drag‐reducing behavior of these polymers exhibited a strong dependence on the molecular weight and Reynolds number, and these polymers could be used as effective oil‐soluble drag reducers and had good shear stabilities. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 1622–1626, 2003     

Synthesis and characterization of the biomaterial poly(lactic acid‐co‐Nε‐carbobenzoyloxy‐L‐lysine) via direct melt copolymerization

With D,L ‐lactic acid and N^ϵ‐carbobenzoyloxy‐L ‐lysine [Lys(Z)] as the starting monomer material and tin dichloride as the catalyst, the drug carrier material poly(lactic acid‐co‐N^ϵ‐carbobenzoyloxy‐L ‐lysine) was synthesized via direct melt polycondensation. The copolymer was systematically characterized with intrinsic viscosity testing, Fourier transform infrared spectroscopy, ¹H‐NMR, gel permeation chromatography, differential scanning calorimetry, and X‐ray diffraction. The influences of different feed molar ratios were examined. With increasing molar feed content of Lys(Z), the intrinsic viscosity, weight‐average molecular weight, and polydispersity index (weight‐average molecular weight/number‐average molecular weight) gradually decreased. Because of the introduction of Lys(Z) with a big aromatic ring into the copolymer, the glass‐transition temperature gradually increased with increasing feed charge of Lys(Z), and all of the copolymers were amorphous. The copolymers, with weight‐average molecular weights from 10,500 to 6900 Da, were obtained and could reach the molecular weight level of poly(lactic acid) modified by Lys(Z) via the ring‐opening polymerization of the cyclic intermediates, such as lactide and morpholine‐2,5‐dione. However, a few terminal carboxyl groups might have been deprotected during the polymerization reaction under high temperatures. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Effect of initiators and ethoxylation degree of non‐ionic emulsifiers on vinyl acetate and butyl acrylate emulsion copolymerization in the loop reactor

Vinyl acetate and butyl acrylate copolymers were synthesized in the presence of ammonium persulfate and potassium persulfate initiators, mixture of non‐ionic and anionic emulsifiers, and polyvinyl alcohol as protective colloid in a loop reactor. The monomer ratio was chosen 85:15. The series of non‐ionic emulsifiers, which have 10–40 moles ethoxylated nonyl phenol, were combined with Nansa 66 (sodium dodecyl benzene sulfonate). The effects of the initiators on the physicochemical properties of copolymers were investigated by measuring conversion, viscosity, molecular weight, molecular weight distribution, and surface tension, respectively by using gravimetric method, Brookfield viscometer, gel permeation chromatograpy (GPC), and ring method. The effects of ethoxylation degrees of the non‐ionic emulsifiers to the same properties of copolymers were also investigated. It was determined that the copolymer viscosities showed different tendency for two initiators. They were increased by the increasing ethoxylation degree of the non‐ionic emulsifier for ammonium persulfate. In contrast, latex viscosity was decreased by increasing the ethoxylation degree in presence of potassium persulfate. Similar changes were also found in number average molecular weights of copolymers. On the other hand, weight average molecular weights of copolymers increased by increasing the ethoxylation degree of the non‐ionic emulsifier for both initiators. In the case of potassium persulfate, the surface tension values of copolymers increased by increasing the ethoxylation degree, but generally increasing the ethoxylation degree did not affect the surface tension of copolymer very seriously for two initiators. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 537–543, 2003     

Review on transesterification in polycarbonate–poly(butylene terephthalate) blend

Various polycarbonate - poly(butylene terephthalate) polyester (PC-PBT) blend prepared by reactive melt blending primarily in extruder with range of temperature and time are discussed in this review article. In the melt blended PC-PBT blend system, transesterification plays a major role in formation of PC-PBT blend. Transesterification reactions between these two polymers have been analyzed by proper polymer sample, end-capped or having reactive chain end group. The kinetics of mechanism is a function of temperature and PC-PBT ratio. Trace catalyst residue present in PBT catalyzes the transesterification reaction. As the extent of transesterification is increased, it forms various composition of copolymer. Inhibition in the transesterification reaction of PC-PBT blend has been observed when different type of alkyl, aryl, and alkyl-aryl group of phosphite are introduced into it, otherwise there has been collateral change in the morphology, thermal, and mechanical property of blend. Therefore, this PC-PBT blend has been an interesting topic of research in academia and industries.     

螺环二醇改性PET共聚酯的合成及性能

为了扩大聚对苯二甲酸乙二醇酯（PET）的应用范围,常通过引入第三单体来改变其性能。本研究以螺环二醇（SPG）为原料,采用酯交换法熔融缩聚合成了一系列不同单体含量的共聚酯。采用超高效聚合物色谱-多角度激光光散射仪（APC-MALLS）联用分析了共聚酯的分子量与分子量分布,利用核磁氢谱（¹H NMR）、傅里叶红外光谱（FTIR）研究了共聚酯的化学结构,同时采用差示扫描量热仪（DSC）、热重分析仪（TGA）和X射线衍射仪（XRD）研究了共聚酯的热性能以及结晶性能,测试了共聚酯的拉伸性能。结果表明,成功合成了符合纤维级聚酯数均分子量（M_n）和重均分子量（M_w）要求的共聚酯,分子量分布较窄,随着第三单体含量的增加,玻璃化转变温度从77℃提升至85℃,而熔融温度从255℃降低至222℃,热分解温度无明显变化,结晶性能下降。     

Aromatic polyesters via transesterification of dimethylterephthalate/isophthalate with bisphenol-a

As a part of our work in the area of transesterification chemistry, we have studied the transesterification of dimethyl terephthalate/isophthalate with bisphenol-A for the synthesis of aromatic polyester. The process comprises two steps. The first step comprises preparation of aromatic polyester prepolymer by reacting the dimethyl esters of terephthalic/isophthalic acids and bisphenol-A in the melt phase via catalyzed interchange reaction. The second step involves the postpolycondensation of aromatic polyester prepolymer under reduced pressure, eliminating the by-product and driving the equilibrium of the reversible reaction to the formation of a high molecular weight aromatic polyester. In both steps, methanol is eliminated as a by-product. The method explored is the simplest one, permits the use of commercial materials as the feed stock, and leads to a low boiling by-product that can be recycled. © 1996 John Wiley & Sons, Inc.     

Synthesis of functionalized copolymers and their compatibilization effects on acrylonitrile butadiene styrene/poly(butylene terephthalate) blends

In this study, the copolymers of methyl methacrylate-co-glycidyl methacrylate (MGD) with different epoxy contents and molecular weights, the styrene-co-glycidyl methacrylate (SGD) and methyl methacrylate-co-maleic anhydride (MAD) were synthesized. The synthesized copolymers, styrene-co-maleic anhydride (SMA) and styrene-acrylonitrile-co-glycidyl methacrylate (SAG) were used as compatibilizers to enhance the impact strength of the acrylonitrile butadiene styrene/poly(butylene terephthalate) (ABS/PBT). The effects of differences in the structure, reactive group type, and molecular weight of the compatibilizers on the mechanical properties, phase morphology, melt viscosity, thermal stability, and melting temperature of the blend were studied. The results showed that functionalized copolymers were successfully synthesized with high monomer conversions. Addition of the functionalized copolymers increased melt viscosity but did not considerably affect thermal stability, tensile strength, flexural strength and melting temperature of the ABS/PBT blends. The compatibilizers improved the dispersion of the PBT phase and prevented brittle fracture, thereby increasing the impact strength of the blend. Among the studied compositions, the ABS/PBT/MGD-5 blend exhibited the highest impact strength of 25.8 kJ/m² and an appropriate melt flow index of 19.1 g/10 minutes. The compatibilizer should have an appropriate molecular weight to improve the interface bonding force. Regarding the melting viscosity, the reactive group content and compatibilizer dosage should be adjusted to ensure high impact strength.     

Transesterifications of poly(bisphenol A carbonate) with aromatic and aliphatic segments in ethylene terephthalate–caprolactone copolyester

In this article, transesterification of poly(bisphenol A carbonate) (PC) with a ethylene terephthalate–caprolactone copolyester at a weight ratio 50/50 (TCL50) was investigated by infrared spectroscopy (IR), proton nuclear magnetic resonance spectroscopy (¹H‐NMR), and a model compound. The IR and ¹H‐NMR results showed that transesterification occurred between PC and ethylene terephthalate (ET) segments in TCL50 and resulted in the formation of bisphenol A–terephthalate ester units as in the annealed blend of PC with the PET homopolyester. By comparison with a model compound, the new signal at 2.55 ppm in the ¹H‐NMR spectrum confirmed the appearance of bisphenol A–caprolactone ester units resulting from the exchange reaction of PC with caprolactone (CL) segments. The ¹H‐NMR analysis of the transesterification rates revealed that the reactions of PC with aromatic and aliphatic segments in TCL50 proceeded in a random or free manner. In addition, we separately examined the interchange reaction between a PC and poly(ε‐caprolactone) (PCL) homopolyester in an annealed blend. It was found that in the presence of a Ti compound catalyst the predominant reaction was a transesterification rather than a thermooxidative branching reaction. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 1558–1565, 2001     

Characterization and Properties of Reactive Poly(lactic acid)/Polyamide 610 Biomass Blends

A low molecular weight bisphenol‐A type epoxy resin was used as a reactive compatibilizer for poly(lactic acid) (PLA)/polyamide 610 (PA 610) biomass blends. To the best of our knowledge, this blend is the first biomass PA 610 blend in the literature. The epoxy functional groups could react with the terminal groups of both PLA and PA 610. An ester–amide interchange reaction led to a polyester–polyamide copolymer formation, and improved the compatibility of PLA and PA 610. The blends with epoxy resin showed an enhancement in the phase dispersion and interfacial adhesion compared with the blend without epoxy resin. The differential scanning calorimetry (DSC) analysis showed that the crystallization peak temperatures decreased with increasing epoxy content. The melting temperature of PA 610 decreased with the addition of PLA, but remained unchanged with increased compatibilizer dosages. The dynamic mechanical analysis (DMA) showed that the glass transition temperature (T_g) of the blend, with the addition of 0.5 phr epoxy resin, slightly increased compared with that of neat PLA. However, the T_g of the blends remained unchanged with increasing epoxy resin content, and the higher content of epoxy resin in the blends resulted in improved mechanical properties and higher melt viscosity. The unnotched impact test showed that PA 610 could toughen PLA with the addition of epoxy resin. Moreover, the no‐break unnotched impact behavior was observed with the medium content of the compatibilizer, improving the notch sensitivity of PLA. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 2563–2571, 2013     

Rheological behavior and mechanical properties of high‐density polyethylene blends with different molecular weights

The dynamic rheological and mechanical properties of the binary blends of two conventional high‐density polyethylenes [HDPEs; low molecular weight (LMW) and high molecular weight (HMW)] with distinct different weight‐average molecular weights were studied. The rheological results show that the rheological behavior of the blends departed from classical linear viscoelastic theory because of the polydispersity of the HDPEs that we used. Plots of the logarithm of the zero shear viscosity fitted by the Cross model versus the blend composition, Cole–Cole plots, Han curves, and master curves of the storage and loss moduli indicated the LMW/HMW blends of different compositions were miscible in the melt state. The tensile yield strength of the blends generally followed the linear additivity rule, whereas the elongation at break and impact strength were lower than those predicted by linear additivity; this suggested the incompatibility of the blends in solid state. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Synthesis and characterization of methacrylated star‐shaped poly(lactic acid) employing core molecules with different hydroxyl groups

A set of novel bio‐based star‐shaped thermoset resins was synthesized via ring‐opening polymerization of lactide and employing different multi‐hydroxyl core molecules, including ethylene glycol, glycerol, and erythritol. The branches were end‐functionalized with methacrylic anhydride. The effect of the core molecule on the melt viscosity, the curing behavior of the thermosets and also, the thermomechanical properties of the cured resins were investigated. Resins were characterized by Fourier‐transform infrared spectroscopy, ¹³C‐NMR, and ¹H‐NMR to confirm the chemical structure. Rheological analysis and differential scanning calorimetry analysis were performed to obtain the melt viscosity and the curing behavior of the studied star‐shaped resins. Thermomechanical properties of the cured resins were also measured by dynamic mechanical analysis. The erythritol‐based resin had superior thermomechanical properties compared to the other resins and also, lower melt viscosity compared to the glycerol‐based resin. These are of desired characteristics for a resin, intended to be used as a matrix for the structural composites. Thermomechanical properties of the cured resins were also compared to a commercial unsaturated polyester resin and the experimental results indicated that erythritol‐based resin with 82% bio‐based content has superior thermomechanical properties, compared to the commercial polyester resin. Results of this study indicated that although core molecule with higher number of hydroxyl groups results in resins with better thermomechanical properties, number of hydroxyl groups is not the only governing factor for average molecular weight and melt viscosity of the uncured S‐LA resins. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45341.     

Determination of the molecular characteristics of commercial polyethylenes with different architectures and the relation with the melt flow index

The molecular weight distribution curves of several commercial polyethylene samples were evaluated by high‐temperature gel permeation chromatography with two detectors (a refractive‐index detector and a viscometer) to determine the molecular sizes and architectures (branching). The polymer samples included high‐ and low‐density polyethylenes with different molecular weight distributions (wide, medium, unimodal, and bimodal) from nine producers. The results were tested against the melt flow index and zero‐shear melt viscosity to find correlations. The data for high‐density polyethylene correlated well with the molecular weight, whereas the data for low‐density polyethylene did not correlate. However, when the weight‐average molecular weight was corrected by the branching parameter and a factor form, all the polyethylene samples fit a single equation. These results indicate that the melt flow index is dependent not only on the molecular weight but also on the molecular shape, including branching. The relation accounted for samples of different resin producers, molecular weights (65,000–638,000), and polydispersities (2.9–20). The use of the branching parameter for the correction of the molecular weight allowed the correlation of these parameters despite differences in the technologies, molecular weights, and molecular architectures. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 1572–1578, 2007     

Blends of thermoplastic polyurethane and maleic-anhydride grafted polyethylene. I: Morphology and mechanical properties

Thermoplastic polyurethane elastomers (TPU) and polyethylene (PE) form immiscible blends with an extremely low compatibility. In order to improve the dispersion, stability, and properties of these blends, polyethylene was grafted with maleic anhydride (PE-g-MA). Subsequently, it was blended with a commercial polyester - type TPU in a twin-screw extruder. With PE-g-MA as blend component, the particle size was dramatically reduced in comparison with PE. Coalescence was significantly reduced and the increase in particle size with composition was less pronounced than in blends with PE. In addition, the phase adhesion and the mechanical properties were improved by using PE-g-MA as minor component. Grafting of the MA onto the PE leads to a decrease of the molecular weight, the melt viscosity, and the mechanical properties of the pure PE. Hence, the reactive blend system exhibits a lower viscosity ratio. Comparison of these results with those from uncompatibilized blends with different viscosity ratios revealed that the reduction in viscosity ratio has a big influence on the blend morphology and because of that on the mechanical properties. In addition, there is a further effect on morphology and properties caused by the reduction in interfacial tension, which results from the compatibilizer formed at the interface.