Nonisothermal crystallization kinetics of poly(butylene terephthalate)/poly(ethylene terephthalate)/glass fiber composites

The influences of the glass fiber (GF) content and the cooling rate for nonisothermal crystallization process of poly(butylene terephthalate)/poly(ethylene terephthalate) (PBT/PET) blends were investigated. The nonisothermal crystallization kinetics of samples were detected by differential scanning calorimetry (DSC) at cooling rates of 5°C/min, 10°C/min, 15°C/min, 20°C/min, 25°C/min, respectively. The Jeziony and Mozhishen methods were used to analyze the DSC data. The crystalline morphology of samples was observed with polarized light microscope. Results showed that the Jeziony and Mozhishen methods were available for the analysis of the nonisothermal crystallization process. The peaks of crystallization temperature (T_p) move to low temperature with the cooling rate increasing, crystallization half‐time (t_1/2) decrease accordingly. The crystallization rate of PBT/PET blends increase with the lower GF contents while it is baffled by higher GF contents. POLYM. COMPOS. 36:510–516, 2015. © 2014 Society of Plastics Engineers     

Isothermal crystallization kinetics of commercially important polyalkylene terephthalates

The isothermal crystallization kinetics of virgin, melt‐mixed, and nucleated specimens of polyethylene terephthalate (PET), polypropylene terephthalate (PPT), and polybutylene terephthalate (PBT) were measured. The purpose of the study was to determine the difference in crystallization rate of PPT, which is to be commercially available in the near future, to the extensively studied, commercially important polyalkylene terephthalates PET and PBT. At equivalent supercooling, the crystallization rate of PPT was between that of PET and PBT, with PBT being the fastest crystallizing polymer. Melt‐mixing virgin materials resulted in a substantial increase in the crystallization rate for all three polyalkylene terephthalates. The addition of talc or sodium stearate as a nucleating agent resulted in a further increase in crystallization rate for all three polyesters. Although the addition of talc or sodium stearate to PPT and PET greatly enhanced crystallization rate, these nucleating agent–containing materials still did not crystallize as fast as PBT melt‐mixed in the absence of any intentionally added nucleating agents. Analysis of the crystallization kinetic data using the Avrami equation showed that melt‐mixing and the addition of sodium stearate resulted in an increase in the average Avrami exponent. This result suggested a change in the mechanism of nucleation toward more sporadic nucleation. For the sodium stearate–nucleated materials, the Avrami exponent was found to increase with increasing crystallization temperature, but a precise explanation of this behavior could not be provided without a knowledge of crystallite morphology. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 76: 1296–1307, 2000     

Study of poly(trimethylene terephthalate) as an engineering thermoplastics material

Poly(trimethylene terephthalate) (PTT) was systematically studied as an engineering thermoplastics material. Crystallization rates, crystalline degrees, and mechanical properties of two commercial PTT polymers and one glass fiber–reinforced PTT compound were investigated and compared with those of poly(butylene terephthalate) (PBT). PTT raw polymers have crystallization temperature (T_c) values around 152°C, and their kneaded polymers show T_c values of about 177°C, about 15°C lower than the values of PBT polymers used in this study. From the exothermic heat values of DSC measurements, both PTT and PBT show the crystalline degree order greater than 30%. Injection‐molded PTT specimens and PBT specimens exhibit crystalline degrees from 18 to 32% and 23.8 to 30%, respectively. PTT polymers show higher tensile and flexural strengths, but lower impact strengths and elongations than those of PBT polymers. The low elongation behavior of PTT does not change with the intrinsic viscosity and the molder temperature. PTT‐GF30 promotes better mechanical properties than those of PBT‐GF30, close to those of PET‐GF30. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 1657–1666, 2004     

节能灯PBT材料阻燃、增韧与抗黄变研究

研究了节能灯用玻璃纤维(GF)增强阻燃聚对苯二甲酸丁二酯(PBT)材料,分别探讨了新的阻燃体系,不同丙烯酸酯类增韧剂对其影响和材料的抗黄变问题。结果表明,新的阻燃体系溴代三嗪/三氧化二锑/OMMT阻燃效果较好,增韧剂中丙烯酸酯类接枝甲基丙烯酸缩水甘油酯(GMA)AX8900效果最好,其次为核壳结构丙烯酸酯类2M,最差为接枝MAH的丙烯酸酯类3M,但三者增韧效果差距不明显。抗黄变母粒的添加使得GF增强阻燃PBT材料在氙灯老化试验后颜色基本不变黄。     

一种高效无卤阻燃PBT复合材料的制备及性能

以次磷酸盐类复合物TF9309为主阻燃剂,三聚氰胺氰尿酸盐(MCA)为协效阻燃剂,采用增韧剂AX8900、偶联剂KH–560和30%的玻璃纤维对聚对苯二甲酸丁二酯(PBT)进行共混挤出改性,研究了无卤阻燃剂用量和不同复配比例对PBT燃烧行为和综合性能的影响,考察了增韧剂和偶联剂对复合材料力学性能的影响。结果表明,当TF9309与MCA两者复配比例为4∶1,总含量为15%,AX8900含量为2%,加入适量偶联剂KH–560时,30%玻纤增强PBT复合材料的阻燃性能和力学性能最佳。     

Properties of glass‐filled thermoplastic polyesters

The thermal, mechanical, and rheological properties of glass‐filled poly(propylene terephthalate) (GF PPT) were compared to glass‐filled poly(butylene terephthalate) (GF PBT). The impetus for this study was the recent commercial interest in PPT as a new glass‐reinforced thermoplastic for injection‐molding applications. This article represents the first systematic comparison of the properties of GF PPT and GF PBT in which differences in properties can be attributed solely to differences in the polyester matrices, that is, glass‐fiber size and composition, polymer melt viscosity, nucleant content and composition, polymerization catalyst composition and content, and processing conditions were kept constant. Under these controlled conditions, GF PPT showed marginally higher tensile and flexural properties and significantly lower impact strength compared to GF PBT. The crystallization behavior observed by cooling from the melt at a constant rate showed that GF PBT crystallized significantly faster than did GF PPT. Nucleation of GF PPT with either talc or sodium stearate increased the rate of crystallization, but not to the level of GF PBT. The slower crystallization rate of GF PPT was found to strongly affect thermomechanical properties of injection‐molded specimens. For example, increasing the polymer molecular weight and decreasing the mold temperature significantly increased the modulus drop associated with the glass transition. In contrast, the modulus–temperature response of GF PBT was just marginally influenced by the polymer molecular weight and was essentially independent of the mold temperature. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 74: 889–899, 1999     

Nonisothermal crystallization kinetics of poly(butylene terephthalate)/epoxidized ethylene propylene diene rubber/glass fiber composites

Nonisothermal crystallization kinetics of poly(butylene terephthalate) (PBT)/glass fiber (GF) and PBT/epoxidized ethylene propylene diene rubber (eEPDM)/GF composites were investigated by differential scanning calorimetry (DSC) at a cooling rates of 2.5, 5, 10, and 20 °C/min, respectively. Morphologies of samples were observed with scanning electron microscopy and polarized optical microscopy. The specimens were prepared by melt blending. Analyses of the melt crystallization data by various macrokinetic models such as Jeziorny‐modified Avrami, Liu–Mo models, and Lauritzen–Hoffman equation revealed that GF accelerated the crystallization rate of PBT; furthermore, the eEPDM had two functions: on the one hand, eEPDM promoted PBT to form nuclei; on the other hand, eEPDM hindered the diffusion of polymer chains, but the nucleation effect exceeded the diffusion effect, thus, the eEPDM could increase the crystallization rate of PBT in PBT/eEPDM/GF. These results were further supported by the effective activation energy calculated by isoconversional method of Friedman. POLYM. ENG. SCI., 59:330–343, 2019. © 2018 Society of Plastics Engineers     

复合成核剂对PBT结晶行为的影响

采用熔融共混法制备了聚对苯二甲酸丁二醇酯(PBT)和成核剂二苄山梨醇(DBS)或苯甲酸钠(SB)的共混物,通过差示扫描量热仪(DSC)、X射线衍射仪(XRD)、偏光显微镜(PLM)分析了各成核剂对PBT的结晶行为的影响,结果表明:添加任何一种成核剂均能明显改善PBT的结晶行为,即加快结晶速度、提高结晶度、细化晶体及完善晶体形态;其中复合成核剂要明显优于单一成核剂,复合成核剂中SB的影响程度要大于DBS。还采用热重分析(TGA)仪对体系的热性能进行了研究,发现成核剂的加入并未降低体系的热性能。     

回收PET玻纤复合材料的结晶性能研究

制备了成核回收PET及其玻璃纤维复合材料，研究了成核回收PET及其玻璃纤维复合材料的结晶与熔融行为、力学性能和加工性能。结果表明，无论是有机羧酸盐成核剂还是无机成核剂都使回收PET的冷结晶温度逐渐降低，热结晶温度逐渐提高。PBT作为PET结晶促进剂，降低回收PET的冷结晶温度，提高热结晶温度。成核回收PET复合材料的力学性能提高，加工性能改善，成型周期缩短。     

Supramolecular Nucleating Agents for Poly(butylene terephthalate) Based on 1,3,5‐Benzenetrisamides

1,3,5‐Benzenetrisamide‐based supramolecular nucleating agents for poly(butylene terephthalate) (PBT) are reported. 1,3,5‐Benzenetrisamides combine excellent thermal stability with chemical resistance, basic requirements for the use in high‐melting thermoplastics. To establish structure–property relationships, the central core and peripheral substituents are varied systematically. Dissolution and crystallization behavior of the additives in the PBT melt and the crystallization temperature of PBT are investigated as a function of the additive concentration. Efficient nucleating agents can increase the crystallization temperature of PBT by 10.6 °C to 199.1 °C. A visualization of supramolecular nano‐objects formed in the polymer melt is provided.

     

Rheological and thermal properties of blends of modified poly(ethylene terephthalate) with p‐acetoxybenzoic acid and poly(butylene terephthalate)

Blending of thermotropic liquid crystalline polyesters (LCPs) with conventional polymers could result in materials that can be used as an alternative for short fiber‐reinforced thermoplastic composites, because of their low melt viscosity as well as their inherent high stiffness and strength, high use temperature, and excellent chemical resistance and low coefficient of expansion. In most of the blends was used LCP of 40 mol % of poly(ethylene terephthalate) (PET) and 60 mol % of p‐acetoxybenzoic acid (PABA). In this work, blends of several copolyesters having various PABA compositions from 10 to 70 mol % and poly(butylene terephthalate) (PBT) were prepared and their rheological and thermal properties were investigated. For convenience, the copolyesters were designated as PETA‐x, where x is the mol % of PABA. It was found that PET‐60 and PET‐70 copolyesters decreased the melt viscosity of PBT in the blends and those PBT/PETA‐60 and PBT/PETA‐70 blends showed different melt viscosity behaviors with the change in shear rate, while blends of PBT and PET‐x having less than 50 mol % of PABA exhibited totally different rheological behaviors. The blends of PBT with PETA‐50, PETA‐60, and PETA‐70 showed the morphology of multiple layers of fibers. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 74: 1797–1806, 1999     

Surface modification of a calcium fluoride filler and the effect on the nonisothermal crystallization behavior of poly(ethylene terephthalate)

Two different types of calcium fluoride particles (～325 nm), one of them surface modified using a long‐chain organophosphorous reagent, were incorporated into a poly(ethylene terephthalate) (PET) matrix. The CaF₂ particles were synthesized by a simple chemical precipitation method. To modify the particles surface, a heat treatment using Cyanex^® 921 [tri‐n‐octylphosphine oxide (TOPO)] dissolved in isopropanol, was carried out. Therefore, unlike the as‐synthesized particles, the modified particles contained an amount of TOPO. The composite materials were prepared by melt‐blending PET and particles at different filler loadings. The influence of the particles surface modification on the nonisothermal crystallization behavior of PET was investigated by using differential scanning calorimetry and field emission scanning electron microscopy. The Jeziorny‐modified Avrami equation was applied to describe the crystallization kinetics and several parameters were analyzed (half‐crystallization time, Avrami exponent, and rate constant). According to the results, the fluorite particles act as nucleating agents, accelerating the PET crystallization rate. However, the effect on the polymer crystallization rate was more noticeable with the addition of the nonmodified particles where the surface might play an important role for epitaxial crystallization, while the addition of the particles, with an organic coating layer on the surface, resulted in a crystallization behavior more similar to the observed for neat PET. POLYM. ENG. SCI., 54:2938–2946, 2014. © 2014 Society of Plastics Engineers     

The hydrolytic stability of glass fiber reinforced poly(butylene terephthalate), poly(ethylene terephthalate) and polycarbonate

The hydrolytic stability of glass fiber reinforced poly(butylene terephthalate) (PBT), poly(ethylene terephthalate) (PET) and polycarbonate (PC) was studied. The activation energies in kcal/mole for hydrolysis are 26 for PBT and 23 for PET. Both PBT and PET contain 30 percent glass fiber reinforcement. The hydrolysis rates for a series of experimental PC's containing 10, 30 and 40 percent glass were obtained from GPC data. These increase with glass concentration but are lower than that of the unreinforced PC. Melt flow rate changes are a good measure of the hydrolytic degradation of PET. However, in the time scale of these experiments, the tensile properties of glass reinforced PBT and PC do not correlate well with M?_w changes, unlike unreinforced PBT and PC polymers. Consequently, to compare these three glass fiber reinforced polymers, estimates of failure time must be based on changes in tensile strength rather than melt flow rate.     

Crystallization of poly(ethylene terephthalate) and poly (butylene terephthalate) modified by diamides

Poly(ethylene terephthalate) (PET) and poly (butylene terephthalate) have been modified by diamide units (0.1–1 mol%) in an extrusion process and the crystallization behavior studied. The diamides used were: for PET, T2T‐dimethyl (N, N′‐bis(p‐carbomethoxybenzoyl)ethanediamine) and for PBT, T4T‐dimethyl (N, N′‐bis(p‐carbomethoxybenzoyl)butanediamine). The above materials were compared to talc (0.5 wt%), this being a standard heterogeneous nucleator, and to diamide modified copolymers obtained by a reactor process. Two PET materials were used: a slowly crystallizing recycled grade obtained from soft drink bottles and a rapidly crystallizing injection molding grade. The crystallization was studied by differential scanning calometry (DSC) and under injection molding conditions using wedge shaped specimens; the thermal properties were studied by dynamic mechanical analysis. T2T‐dimethyl is effective in increasing the crystallization of PET in both of the extrusion compounds as well as in the reactor materials. It was also found that the crystallization temperature of poly(butylene terephthalate) could be slightly increased by the addition of nucleators.     

Non-isothermal crystallization kinetics of poly(ethylene terephthalate)/mica composites

The non-isothermal crystallization kinetics of pure poly(ethylene terephthalate) (PET), PET/mica and PET/TiO₂-coated mica composites were investigated by differential scanning calorimetry with different theoretical models, including the modified Avrami method, Ozawa method and Mo method. The activation energies of non-isothermal crystallization were calculated by Kissinger method and Flynn–Wall–Ozawa method. The results show that the modified Avrami equation and Ozawa theory fail to describe the non-isothermal crystallization behavior of all composites, while the Mo model fits the experiment data fair well. It is also found that the mica and TiO₂-coated mica could act as heterogeneous nucleating agent and accelerate the crystallization rates of PET, and the effect of TiO₂-coated mica is stronger than that of mica. The result is further reinforced by calculating the effective activation energy of the non-isothermal crystallization process for all composites using the Kissinger method and the Flynn–Wall–Ozawa method.     

成核剂对不同特性粘数PET结晶性能的影响

研究了新型复合成核剂水滑石(HT)／离聚物(Surlyn8920)／聚乙二醇(PEG)对不同特性粘数聚对苯二甲酸乙二醇酯(PET)非等温结晶性能的影响。通过差示扫描量热仪测试了PET的结晶峰温度T_(mc)和熔融峰温度(T_m)。结果表明,复合成核剂各组分及PET的质量比为0.5:3.0:3.0:100.0时,各种PET的过冷度(T_m-T_(mc))均显著减少．半结晶时间(1gt_(1／2))也明显降低。而且,复合成核剂对不同特性粘数PET结晶性能的改善是一致的。     

Kinetics of water absorption and hygrothermal aging rubber toughened poly(butylene terephthalate) with and without short glass fiber reinforcement

The objectives of this paper were to investigate the water absorption and hygrothermal aging behavior of rubber‐toughened poly(butylenes terephthalate) (RT‐PBT) with and without short glass fiber (SGF) reinforcement. The rubbers used in the study were AX8900 and EXL2314, both of which are acrylate‐based terpolymer. The effect of the hygrothermal aging on its fracture properties was also studied. The kinetics of the water absorption study were carried out on the injection‐molded samples of the RT‐PBTs and the SGF‐reinforced rubber‐toughened PBT (SGF‐RT‐PBT) at three immersion temperatures, 30, 60 and 90°C, for a total of 450 h. The study of the deterioration caused by the hygrothermal aging was conducted by investigating the fracture parameters and flexural properties of all the materials as both hygrothermally aged (HA) and redried state (RD). The modes of the failure of HA and RD samples were studied using the scanning electron microscopy (SEM) technique. It was found that all the samples conformed to Fickian behavior and the kinetics of absorption exhibited a strong dependency on the rubber types, presence of SGF, as well as the immersion temperature. Generally, SGF‐RT‐PBT showed a better resistance to hygrothermal aging than that of RT‐PBT and PBT, though a declining trend was observed in the fracture parameters, K_c and G_c. However, an opposite observation was exhibited in the flexural properties in some, but not all cases. Finally, the results obtained from SEM micrographs showed that permanent damage occurred in the materials and the hygrothermal aging had suppressed the plastic deformation ability of the PBT matrix and both types of impact modifiers where brittle failure was observed. Fiber pull‐out was apparently the failure mode of the SGF‐reinforced materials. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 506–516, 2004     

Thermal and crystallization characteristics of poly(ethylene terephthalate) with poly(oxybenzoate‐p‐trimethylene terephthalate) copolymer

Poly(ethylene terephthalate) (PET) was blended with two different poly(oxybenzoate‐p‐trimethylene terephthalate) copolymers, designated T28 and T64, with the level of copolymer varying from 1 to 15 wt %. All samples were prepared by solution blending in a 60/40 (by weight) phenol/tetrachloroethane solvent at 50°C. The crystallization behavior of the samples was studied by DSC. The results indicate that both T28 and T64 accelerated the crystallization rate of PET in a manner similar to that of a nucleating agent. The acceleration of PET crystallization rate was most pronounced in the PET/T64 blends with a maximum level at 5 wt % of T64. The melting temperatures for the blends are comparable to that of pure PET. The observed changes in crystallization behavior are explained by the effect of the physical state of the copolyester during PET crystallization as well as the amount of copolymer in the blends. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 1599–1606, 2002     

Fast crystallization of liquid crystalline copolyesters based on poly(ethylene terephthalate)

Crystallization of a series of liquid crystalline copolyesters prepared from p‐hydroxybenzoic acid (HBA), hydroquinone (HQ), terephthalic acid (TA), and poly(ethylene terephthalate) (PET) was investigated by using differential scanning calorimetry (DSC). It was found that these copolyesters are more crystalline than copolyesters prepared from PET and HBA. Insertion of HQ–TA disrupts longer rigid‐rod sequences formed by HBA and thus enhances molecular motion and increases the crystallization rate. The effects of additives on the crystallization of the copolyesters were also studied. Sodium benzoate (SB) and sodium acetate (SA) increase the crystallization rate of the copolyesters at low temperature, but not at high temperature. It is most likely that liquid crystalline copolyesters do not need nucleating agents, and small aggregates of local‐oriented rodlike segments in nematic phase could act as primary nuclei. Chain scission of the copolyesters caused by the reaction with the nucleating agents was proved by the determination of intrinsic viscosity and by the IR spectra. Diphenylketone (DPK) was shown to effectively promote molecular motion of chains, leading to an increase in the crystallization rate at low temperature, but it decreased the crystallization rate at high temperature. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 79: 497–503, 2001