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     

成核剂对PET非等温结晶动力学的影响

利用差示扫描量热仪(DSC)研究了滑石粉、苯甲酸钠和离子聚合物Surlyn对聚对苯二甲酸乙二醇酯(PET)非等温结晶行为的影响,并用Ozawa模型计算了非等温结晶动力学参数。结果表明:三种成核剂均是PET的良成核剂,其中苯甲酸钠的成核效果最为显著。与纯PET相比,三种成核剂的加入均使PET的结晶峰温度Tmc向高温偏移,过冷度(Tm-Tmc)明显降低,结晶速率常数K明显增大。纯PET和PET/成核剂共混体系的Ozawa指数n值介于1-4之间,均不为整数,且PET/成核剂共混体系的Ozawa指数n值小于纯PET的n值。     

3D打印用聚对苯二甲酸乙二醇酯的研究

选用聚对苯二甲酸乙二醇酯（PET）作为基体材料,通过添加聚对苯二甲酸丁二醇酯（PBT）、相容剂、增韧剂和成核剂制得适用于熔融沉积技术的PET丝材。结果表明,当PET∶PBT为7∶3时,熔体流动速率最低;过多相容剂在螺杆进料口架桥,不利于螺杆挤出;当增韧剂含量为15份（质量份,下同）时,材料能够正常打印,样条无翘曲且表面光滑,材料的拉伸强度和弯曲强度都较高,分别为25.95 MPa和45.99 MPa,冲击强度为50.4 kJ/m²;添加0.5份滑石粉后材料的力学强度的改善效果更佳。     

Crystallization kinetics of glass fiber reinforced PBT composites

The effect of glass fibers on the crystallization of poly(butylene terephthalate) (PBT) was investigated by crystallization kinetics analysis under isothermal and nonisothermal conditions. From the crosspolar optical micrographs of melt‐ and solvent‐crystallized PBT composites, the glass fibers were found to increase the number density and decrease the size of crystallites. The glass fibers provided heterogeneous nucleation sites, and thus enhanced the overall rate of PBT crystallization in isothermal experiments. However, the Avrami exponent and the regime transitions were not significantly affected by the presence of glass fibers. For the nonisothermal kinetics of PBT composites, the model prediction was excellent in most ranges of crystallization, but it deviated above 70% of crystallization especially at fast cooling rates (>40°C/min). This discrepancy of the model seemed to result from the growth regime transitions, which were clearly observed especially at high undercoolings. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 78: 576–585, 2000     

Crystallization kinetics of poly(1,4‐butylene‐co‐ethylene terephthalate)

The crystallization kinetics of poly(butylene terephthalate) (PBT), poly(ethylene terephthalate) (PET), and their copolymers poly(1,4‐butylene‐co‐ethylene terephthalate) (PBET) containing 70/30, 65/35 and 60/40 molar ratios of 1,4‐butanediol/ethylene glycol were investigated using differential scanning calorimetry (DSC) at crystallization temperatures (T_c) which were 35–90 °C below equilibrium melting temperature . Although these copolymers contain both monomers in high proportion, DSC data revealed for copolymer crystallization behaviour. The reason for such copolymers being able to crystallize could be due to the similar chemical structures of 1,4‐butanediol and ethylene glycol. DSC results for isothermal crystallization revealed that random copolymers had a lower degree of crystallinity and lower crystallite growth rate than those of homopolymers. DSC heating scans, after completion of isothermal crystallization, showed triple melting endotherms for all these polyesters, similar to those of other polymers as reported in the literature. The crystallization isotherms followed the Avrami equation with an exponent n of 2–2.5 for PET and 2.5–3.0 for PBT and PBETs. Analyses of the Lauritzen–Hoffman equation for DSC isothermal crystallization data revealed that PBT and PET had higher growth rate constant G_o, and nucleation constant K_g than those of PBET copolymers. © 2001 Society of Chemical Industry     

Non-isothermal Crystallization Kinetics of Poly (Ethylene Terephthalate)/Grafted Carbon Black Composite

Summary The grafted carbon black (GCB) was prepared by in-situ grafting low molecular weight compound on the surface of carbon black (CB) using a new technique. Poly(ethylene terephthalate)/grafted carbon black (PET/GCB) and poly(ethylene terephthalate)/ carbon black (PET/CB) composites were prepared by melt blending. The non-isothermal crystallization process of virgin Poly(ethylene terephthalate)(PET), PET/CB, and PET/GCB composites were investigated by differential scanning calorimetry (DSC), and the non-isothermal crystallization kinetics was analyzed using different approaches, i.e. modified Avrami equation, Ozawa equation and the method developed by Liu. The effective energy barrier ΔE of virgin PET, PET/CB, and PET/GCB composites were calculated using the differential iso-conversional method. All of the results showed that GCB and CB acted as nucleating agents and increased the crystallization rate of PET. Compared with CB, GCB was a more effective nucleator for PET.     

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。     

Kinetics of isothermal and non‐isothermal crystallization of poly(butylene terephthalate)/ liquid crystalline polymer blends

The melting behavior and isothermal and non‐isothermal crystallization kinetics of poly(butylene terephthalate) (PBT)/thermotropic liquid crystalline polymer (LCP), Vectra A950 (VA) blends were studied by using differential scanning calorimetry. Isothermal crystallization experiments were performed at crystallization temperatures (T_c), of 190, 195, 200 and 205°C from the melt (300°C) and analyzed based on the Avrami equation. The values of the Avrami exponent indicate that the PBT crystallization process in PBT/VA blends is governed by three‐dimensional morphology growth preceded by heterogeneous nucleation. The overall crystallization rate of PBT in the melt blends is enhanced by the presence of VA. However, the degree of PBT crystallinily remains almost the same. The analysis of the melting behavior of these blends indicates that the stability and the reorganization process of PBT crystals in blends are dependent on the blend compositions and the thermal history. The fold surface interfacial energy of PBT in blends is more modified than in pure PBT. Analysis of the crystallization data shows that crystallization occurs in Regime II across the temperature range 190°C‐205°C. A kinetic treatment based on the combination of Avrami and Ozawa equations, known as Liu's approach, describes the non‐isothermal crystallization. It is observed that at a given cooling rate the VA blending increases the overall crystallization rate of PBT.     

玻纤增强阻燃PET的研制

研制了一种玻纤增强阻燃聚对苯二甲酸乙二酯(PET),着重考察了滑石粉、苯甲酸钠、Na2CO3、硬脂酸镁、ZnO及自制的几种结晶成核剂对材料力学性能和熔体流动速率的影响。结果表明,在没有加入结晶成核剂的情况下,单独加入玻纤对PET的增强增韧效果并不明显;适当的结晶成核剂能明显提高玻纤增强PET的力学性能,并改善其熔体流动性,促进PET制品定型,缩短生产周期;添加12份十溴二苯醚/Sb2O3复合阻燃剂,可使玻纤增强PET的阻燃性能达到UL94 V-0级。     

Melting,crystallization behaviors,and nonisothermal crystallization kinetics of PET/PTT/PBT ternary blends

The melting, crystallization behaviors, and nonisothermal crystallization kinetics of the ternary blends composed of poly(ethylene terephthalate), poly(trimethylene terephthalate) (PTT) and poly(buthylene terephthalate) (PBT) were studied with differential scanning calorimeter (DSC). PBT content in all ternary blends was settled invariably to be one‐third, which improved the melt‐crystallization temperature of the ternary blends. All of the blend compositions in amorphous state were miscible as evidenced by a single, composition‐dependent glass transition temperature (T_g) observed in DSC curves. DSC melting thermograms of different blends showed different multiple melting and crystallization peaks because of their various polymer contents. During melt‐crystallization process, three components in blends crystallized simultaneously to form mixed crystals or separated crystals depending upon their content ratio. The Avrami equation modified by Jeziorny and the Ozawa theory were employed to describe the nonisothermal crystallization process of two selected ternary blends. The results spoke that the Avrami equation was successful in describing the nonisothermal crystallization process of the ternary blends. The values of the t_1/2 and the parameters Z_c showed that the crystallization rate of the ternary blends with more poly(ethylene terephthalate) content was faster than that with the lesser one at a given cooling rate. The crystal morphology of the five ternary blends investigated by polarized optical microscopy (POM) showed different size and distortional Maltese crosses or light spots when the PTT or poly(ethylene terephthalate) component varied, suggesting that the more the PTT content, the larger crystallites formed in ternary blends. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007     

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     

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。     

Crystallization kinetics and nucleating agents for enhancing the crystallization of poly(p-phenylene sulfide)

An experimental study of crystallization kinetics and the influence of nucleating agents on the solidification of poly(p-phenylene sulfide) (PPS) is described. The effect of molecular weight is considered by investigating PPS samples having different viscosity levels. We studied the effect of a range of nucleating agents including aluminum oxide, calcium oxide, silicon dioxide, titanium dioxide, kaolin, and talc. All of these compounds were found to enhance the rate of crystallization; in particular, silicon dioxide, kaolin, and talc were the most effective nucleating agents. An effort to study particle size effects of the silicon dioxide showed that the nucleation was very sensitive to the source of the material. These studies did, however, show that nucleation rates tended to increase with decreasing particle size and increasing loading of silicon dioxide. Comparison of PPS crystallization rates with those of other polymers indicates that it crystallizes much more slowly than polyethylene or isotactic polypropylene and is slower than polyetherether-ketone, when comparisons are made on an equivalent basis. PPS crystallizes at similar rates to polyethylene terephthalate (PET). However, our nucleated PPS does not crystallize as rapidly as nucleated PET.     

Kinetics of non-isothermal cold crystallization of uniaxially oriented poly(ethylene terephthalate)

The non-isothermal equation was extended to describe non-isothermal cold crystallization kinetics of oriented polymers. The validity of the equation was examined by using a DSC crystallization curve of oriented poly(ethylene terephthalate) (PET) fibers with a constant heating rate. The double cold crystallization peaks appeared in the DSC curve. The relative degrees of crystallinity at different temperatures were analyzed by using the equation. The results show that the value of the Avrami exponent near to 1 at lower temperatures implies the bundle-like crystal growth geometry and the value of the Avrami exponent near to, 2, at higher temperatures implies the higher dimension crystal growth geometry. The first crystallization process crystallizes at faster rate than that of the isotropic sample, while the second process crystallizes at slower rate than that of isotropic sample. If a simple single process model was used, the value of the Avrami exponent, 0.77, was obtained. The result shows the simple single process model cannot describe the processes of crystallization of oriented PET fibers satisfactorily.     

PBT／PET并列型复合纺丝的研究

就ＰＢＴ、ＰＥＴ两种聚合物材料的流变性能和ＰＢＴ／ＰＥＴ并列型复合纤维的熔纺温度之间的关系进行了讨论，指出ＰＢＴ宜低温熔融、高温纺丝，ＰＥＴ则相反．同时．还考察了复合比对初生丝热性能、ＤＴ丝卷缩性能的影响，表明随着ＰＢＴ组份量的增加，Ｔｇ转变和冷结晶放热峰移向较低温位．且后者峰面积相应缩小；ＰＢＴ熔融吸热峰面积增大．ＰＥＴ的则相应缩小；ＤＴ丝的卷缩率增大．卷缩稳定性则变差．此外．还就纺丝速度对初生丝热性能和结晶度的影响进行了探讨．发现随着纺丝速度的提高，初生丝ＤＳＣ扫描曲线上的冷结晶移向较低温位，而两组份的熔融吸热峰似无变化；初生丝结晶应随纺速的提高而略有增加．但增幅不大．     

Nonisothermal crystallization behavior and UV screening ability of poly(ethylene terephthalate)/carbon black transparent films

A UV absorbent was blended with virgin carbon black to prepare modified carbon black (m-CB) using a solid phase modification. The mixed solutions of poly(ethylene terephthalate) (PET)/CB and PET/m-CB were coated on glass substrates to fabricate light screening films. Scanning electron microscopy (SEM) showed that m-CB had better dispersibility than CB in PET matrix. Nonisothermal crystallization kinetics of virgin PET, PET/CB, and PET/m-CB films were investigated by differential scanning calorimetry (DSC). The data were described by a modified Avrami model. The results showed CB and m-CB acted as nucleating agents and increased the crystallization rate of PET. But due to the low crystallization capacity of copolymerized PET (co-PET) matrix, the nucleating effects were not as obvious as expected. The addition of 4 wt% m-CB improved the UV screening ability of the composite film significantly and just slightly increased their haze.     

Effects of size and shape of dispersed poly(butylene terephthalate) on isothermal crystallization kinetics and morphology of poly(lactic acid) blends

The isothermal crystallization kinetics and morphology of the poly(lactic acid) (PLA) blends containing three different sizes of both spherical and fibrous poly(butylene terephthalate) (PBT) domains have been comparatively investigated by differential scanning calorimetry (DSC) and polarized optical microscopy (POM). The dynamic DSC measurement reveals that PBT domains significantly increase the degree of crystallinity of the PLA. Furthermore, the Avrami model is employed to evaluate the crystallization kinetics under isothermal conditions and it is found that PBT acts as nucleating agent, leading to a high overall crystallization rate constant k and shortened crystallization half time t_1/2. Furthermore, the crystallization rate of PLA is promoted with the incorporation of PBT with a large specific surface area. The average Avrami index n of all samples lies within the range of 3.3 ? 4.0, suggesting that morphologies of PBT do not affect the nucleation mechanism; however, the depression of equilibrium melting temperature in the blends ascribes the reductions of perfectness and size of the PLA crystallites. Besides, the nucleation of PLA crystallites around PBT fibers is probably faster than those around PBT spheres because the PBT chains oriented at the fiber surface as a result of flow‐induced crystallization during melt stretching may serve as the primary nuclei for PLA chains to drastically crystallize at the fiber surface. POLYM. ENG. SCI., 56:258–268, 2016. © 2015 Society of Plastics Engineers     

Effective nucleating chemical agents for the crystallization of poly(trimethylene terephthalate)

This study focused on the crystallization promotion of poly(trimethylene terephthalate) (PTT), with an aim at engineering thermoplastics applications. The effects of organic sodium (Na) salts, including Na stearate, Na benzoate, disodium‐p‐phenolsulfonate (2Na‐p‐PS), disodium‐p‐hydroxybenzoate (2Na‐p‐HB), and the sodium ionomer of poly(ethylene‐co‐methacrylic acid) (Na‐EMAA), were investigated as nucleating chemical agents with differential scanning calorimetry and capillary viscometry. For comparison, the effect of fine talc powder was also examined. The chemical agents were generally more effective than fine talc powder. Na stearate and Na benzoate caused large‐scale decomposition of PTT. 2Na‐p‐PS was quite thermally stable and caused little decomposition. 2Na‐p‐HB was the most efficacious of the nucleating chemical agents and caused mild decomposition. Na‐EMAA was the most thermally stable and induced an increase in melt viscosity. A remarkable improvement in the crystallization rate of PTT was successfully attained at a minimum polymer decomposition cost by the introduction of a suitable amount of 2Na‐p‐PS, 2Na‐p‐HB, or Na‐EMAA or by the concurrent proper incorporation of both of the latter two agents. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 590–601, 2004