Effect of high content of carbon black on non-isothermal crystallization behavior of poly(ethylene terephthalate)

With the aid of co-rotating twin screw extruder, poly(ethylene terephthalate) (PET)/carbon black (CB) masterbatches were fabricated through melt-compounding using a separate feeding and metering technique and their homogeneous dispersion morphologies were confirmed by scanning electron microscopy and transmission electron microscopy. Moreover, the ultimate content of CB in the masterbatches was verified via thermogravimetric analysis method. The non-isothermal crystallization process of pristine PET and PET/CB masterbatch were investigated by differential scanning calorimetry and the different methods such as Jeziorny modified Avrami equation, Ozawa equation, and the method developed by Mo were employed to analyze their non-isothermal crystallization kinetics. The results show that CB particles uniformly dispersed in PET matrix act as heterogeneous nucleating agents, while crystallization activation energy (ΔE) of PET/CB masterbatch is much greater than that of virgin PET according to Kissinger formula, Takhor model, and Augis-Bennett model. Whereas, the results obtained from the above mentioned three methods simultaneously demonstrate the addition of CB greatly increases crystallization temperature and crystallinity and accelerates crystallization rate. The results reveal that crystal growth has little effect on the crystallization rate and crystal nucleation dominates the crystallization process of PET/CB masterbatch containing very high CB loading (20 wt%).     

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.     

Effect of coupling agent on crystallization and rheological properties of poly(ethylene terephthalate) composite masterbatches

Poly(ethylene terephthalate)/carbon black/coupling agent composite masterbatches were fabricated using separate feeding technique. The effect of coupling agent on crystallization of composite masterbatches was investigated by differential scanning calorimetry, wide‐angle X‐ray diffraction, and Fourier transform‐infrared spectroscopy, respectively. The results show that the strong interfacial interaction among poly(ethylene terephthalate) (PET), coupling agent and carbon black hinders chains mobility in process of PET crystallization, which is illustrated by interfical structure model. Whereas, the crystallinity of composite masterbatch increases due to uniform dispersion of carbon black modified by coupling agent. Activation energy of viscous flow of the composite masterbatches is closer to that of virgin PET, so the spinning parameters can be controlled according to each other. Besides, structural viscosity index of composite masterbatches is greater due to strong interfacial interaction among PET, coupling agent and carbon black. Thus, in order to smooth spinning, the composite masterbatches need greater shear rate compared with PET/carbon black masterbatch. POLYM. COMPOS., 38:2358–2367, 2017. © 2015 Society of Plastics Engineers     

Morphology,crystallization, and mechanical properties of poly(ethylene terephthalate)/multiwalled carbon nanotubes composites

Poly(ethylene terephthalate)/multiwalled carbon nanotubes (PET/MWCNTs) with different MWCNTs loadings have been prepared by in situ polymerization of ethylene glycol (EG) containing dispersed MWCNTs and terephthalic acid (TPA). From scanning electronic microscopy images of nanocomposites, it can be clearly seen that the PET/MWCNTs composites with low‐MWCNTs contents (0.2 and 0.4 wt %) get better MWCNTs dispersion than analogous with high‐tube loadings (0.6 and 0.8 wt %). The nonisothermal crystallization kinetics was analyzed by differential scanning calorimetry using Mo kinetics equation, and the results showed that the incorporation of MWCNTs accelerates the crystallization process obviously. Mechanical testing shows that, in comparison with neat PET, the Young's modulus and the yield strength of the PET nanocomposites with incorporating 0.4 wt % MWCNTs are effectively improved by about 25% and 15%, respectively. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

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。     

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.     

具有原位导电微纤网络的CB/PET/PE复合材料的力学性能

在前期热塑性塑料原位成纤研究的基础上，尝试利用原位成纤方法制备炭黑(CB)／聚对苯二甲酸乙二醇酯(PET)／高密度聚乙烯(HDPE)原位导电微纤网络复合材料(CEMN)，以期增强复合体系的力学强度。通过对CEMN体系与CB／PE体系的力学性能测试发现，CEMN体系的拉伸强度低于普通CB/PE复合物。为增强复合体系的力学性能，应改变加工过程及降低体系中CB的用量。     

Non-isothermal Crystallization Behavior of Poly(ethylene terephthalate)/Poly(trimethylene terephthalate) Blends

Summary Non-isothermal crystallization behavior of Poly(ethylene terephthalate)/Poly(trimethylene terephthalate) blends was investigated by XRD and DSC. By XRD spectra analysis, it could be concluded that PET and PTT crystals coexisted. They did not form the cocrystals due to different chemical structures. The Avrami equations modified by Jeziorny and Ziabicki’s kinetic crystallizability analysis were employed to describe the non-isothermal crystallization process of PET/PTT blends. The results suggested that the entanglement of the two polymer chains decrease the crystallizability of PET and PTT in blend. The crystallization activation energies of the blend evaluated by the Friedman method also indicated that the presence of two components in the blends hinders the crystallization process of both components.     

Morphology,resistivity, and thermal behavior of EVOH/carbon black and EVOH/graphite composites prepared by simple saponification method

Poly(ethylene‐co‐vinyl alcohol) (EVOH)/carbon black (CB) and EVOH/graphite (GP) electro‐conductive composites were prepared by saponification of poly(ethylene‐co‐vinyl acetate) (EVA)/CB and EVA/GP composites in ethanol/KOH solution. The electrical resistivity change and positive temperature coefficient (PTC) behavior of these composites were investigated. The volume resistivity of EVA/CB and EVA/GP composites was decreased with saponification time. It can be observed that EVA/CB10 and EVA/GP05 composites showed a significant reduction in resistivity after saponification for 1 h. With the increase in saponification time, PTC peak temperature of both composites was shifted at a higher temperature. Tensile properties, morphology, and thermal behavior of the prepared composites have been also evaluated using universal test machine, scanning electron microscopy, and differential scanning calorimetry, respectively. POLYM. COMPOS., 2011. © 2011 Society of Plastics Engineers     

Polyvinylidene fluoride/poly(ethylene terephthalate) conductive composites for proton exchange membrane fuel cell bipolar plates: Crystallization,structure, and through‐plane electrical resistivity

Polyvinylidene fluoride/poly(ethylene terephthalate) (PVDF/PET)‐based composites for proton exchange membrane fuel cell bipolar plates (BPs) were prepared at different crystallization temperatures and characterized by X‐ray diffraction, differential scanning calorimetry, and resistivity setup. Composite conductivity was made possible by using a mixture of carbon black (CB) and graphite (GR). To improve composite processability, its viscosity was reduced by adding a small amount of cyclic butylene terephthalate (c‐BT) oligomer and thermoplastic polyolefin elastomer. In the PVDF/PET‐based composite, it was found that PVDF phase could crystallize easily but PET crystallization was difficult. Because of the CB/GR additives, the formed crystals in PVDF/PET phases had a poor perfection degree and showed a lower melting temperature when compared with pure PVDF and PET. It was observed that PET nucleation was accelerated but not that of PVDF. According to through‐plane resistivity results, composite crystallization temperature range was divided into two parts (below/above 170°C), in which a different variation behavior of through‐plane resistivity was observed. It has been proved that the resistivity was mainly governed by the network of CB/GR developed inside the PET phase, and decreasing the crystallinity of PET led to a decrease of through‐plane resistivity, which is desirable for BPs. POLYM. ENG. SCI., 2012. © 2012 Society of Plastics Engineers     

Poly(butylene terephthalate)/ poly(ethylene‐co‐alkyl acrylate)/ carbon black conductive composites: Influence of composition and morphology on electrical properties

Poly(butylene terephthalate)/Poly(ethylene‐co‐alkyl‐acrylate)/carbon black (PBT‐EXA‐CB) blends, prepared through extrusion, were characterized as electrical conductive materials. In the composition range studied (55 ≤ PET % ≤ 75 w/w 5.5 ≤ CB % ≤ 11.1 w/w), various conductive behaviors were observed depending mainly on composition and poly(olefin) crystallinity. The observed positive temperature coefficient (PTC) is quite small compared to poly(olefin)‐CB systems, and our blends do not present a negative temperature coefficient (NTC) on complete melting of the CB‐containing phase, thus offering new possibilities for a regular electric power control. Volume expansion of both PBT and EXA was postulated to be the main parameter responsible for the thermal resistivity evolution through the range +20 to +170°C. A double‐percolation system between both the co‐continuous polymer phases and CB‐particles included in the poly(olefin) phase is postulated to explain these results.     

PET/PE/CB导电母料的研制

采用分离喂料技术在聚对苯二甲酸乙二酯(PET)/聚乙烯(PE)共混物中加入导电炭黑(CB),通过布斯往复式脉动挤出机熔融共混、挤出造粒,制备了综合性能较好的纤维级PET/PE/CB导电母料。研究发现,以PET/PE不相容共混物代替PET作母料的基体树脂,能以较低的CB用量获得较好的导电性能;CB的质量分数为15%时,母料的体积电阻率随PET用量的增加呈先减小后增大的趋势,在PET与PE的质量比为60∶40时,母料的体积电阻率最低。     

HT／Surlyn／PEG复合成核剂对PET结晶性能的影响

研究了水滑石(HT)/离子键聚合物(Surlyn)/聚乙二醇(PEG)复合成核剂对聚对苯二甲酸乙二醇酯(PET)非等温结晶性能的影响。通过正交实验选择最佳复合成核剂配方。差示扫描量热分析表明,HT/Surlyn/PEG复合成核剂各组分与PET的质量比为0．5/3/3/100时,PET的结晶温度提高,半结晶时间明显减少,说明PET的成核能力提高,结晶能力增强,结晶速率加快；同时,结晶放热焓和熔融吸热焓增加,说明PET的结晶度得到提高。     

Preparation and characterization of poly(trimethylene terephthalate)‐poly(ethylene oxide terephthalate) segmented copolymer/multiwalled carbon nanotubes composites by in situ polymerization

Poly(trimethylene terephthalate)‐poly(ethylene oxide terephthalate) block copolymer (PTG)/multiwalled carbon nanotubes (MWCNTs) composites were prepared via in situ polymerization. To improve the dispersion of MWCNTs in the PTG matrix, the poly(ethylene glycol)‐grafted multiwalled carbon nanotubes (MWCNT‐PEG) were produced by the “graft to” method. The transmission electron microscopy observation demonstrated that a homogeneous dispersion of MWCNT‐PEG was obtained. As a consequence, the percolation threshold for the rheology was around 0.5 wt% and the conductivity was ～1 wt%, respectively. Differential scanning calorimetry and polarized optical microscopy results confirmed that MWCNT‐PEG can act as an effective heterogeneous nucleating agent. Interestingly, the effects of MWCNT‐PEG on crystallization and melting of the poly(ethylene oxide terephthalate) blocks were more pronounced than on those of the PTT blocks. POLYM. ENG. SCI., 2013. © 2012 Society of Plastics Engineers     

溶胶-凝胶法制备PET/SiO2纳米复合材料及其TG、DSC分析

采用溶胶-凝胶（sol-gel）法，将正硅酸乙酯和水加入到制备聚对苯二甲酸乙二酯（PET）的中间产物对苯二甲酸双羟乙酯(BHET)中,在液态下均匀混合，高温下快速发生溶胶-凝胶反应，再按PET缩聚反应制得PET/SiO₂纳米复合材料。通过TEM、TG、DSC对材料进行了表征和研究。结果表明，SiO₂在PET中均匀分散，其尺寸在10～100 nm之间，PET/SiO₂纳米复合材料的热降解活化能较普通PET有明显提高，但初始降解温度和结晶性能均有所降低。     

Effect of coupling agent on structure and properties of micro–nano composite fibers based on PET

Poly(ethylene terephthalate) (PET)/carbon black (CB) micro–nano composite fibers were manufactured by melt spinning method. To achieve good dispersion, nano‐CB particles were modified by coupling agent (CA). The effect of CA on structure and properties of the fibers were investigated via scanning electron microscopy (SEM), tensile testing, differential scanning calorimetry (DSC), wide‐angle X‐ray diffraction (WAXD), sonic orientation, and birefringence, respectively. At 2 wt % CA dosage, CB particles present the optimal dispersion in the fibers, shown in SEM images. Besides, the fibers possess the maximum breaking strength, the lowest crystallization temperature, and the highest crystallinity. After CA modification, the superior interfacial structure between PET and CB is beneficial to improve mechanical properties of the fibers. The well dispersed CB particles provide more heterogeneous nucleation points, resulting in the highest crystallinity. Furthermore, the fibers with 2 wt % CA dosage possess the maximum orientation and shrinkage ratio. According to Viogt–Kelvin model, the thermal shrinkage curves of the fibers can be well fitted using single exponential function. The three‐phase structure model of crystal phase–amorphous phase–CB phase was established to interpret the relationship among shrinkage, orientation, and dispersion of CB particles. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43846.     

Effect of modified carbon black on the UV/IR screening ability of poly(ethylene terephthalate) transparent films

The mixed solution of poly (ethylene terephthalate) (PET)/carbon black (CB) and PET/modified CB (m‐CB) were coated on glass substrates to fabricate light screening films. m‐CB was prepared using a solid phase modification method through mechanical blending of CB and 2‐(2′‐Hydroxy‐5′‐methylphenyl)‐benzotriazole (UV‐P) in weight composition of 50 : 50. The results of dynamic light scattering (DLS), optical microscopy, and scanning electron microscopy (SEM) showed that the modification of CB obviously reduced the particle and aggregate sizes of CB, leading to better dispersion of m‐CB in PET films. Fourier transform infrared spectroscopy (FTIR) proved that UV‐P was grafted on CB after blending and changed the molecular structure of CB. Ultraviolet‐visible‐Infrared (UV‐vis‐IR) spectrophotometer tests showed that the UV/IR absorption property of the films improved obviously while the visible light transmittance reduced gradually with the increase of m‐CB content from 0.5 to 6 wt%. Differential scanning calorimeter (DSC) results showed the addition of 4 wt% m‐CB decreased the crystallinity of PET matrix, which effectively inhibited the destruction of the film transparency with the addition of more CB. POLYM. COMPOS., 2011. © 2010 Society of Plastics Engineers     

Non-isothermal crystallization kinetics of poly (lactic acid)/modified carbon black composite

A novel method was employed to modify the surface of carbon black (CB) by an organic small molecule in a Haake Rheomix mixer. Jeziorny equation, the Ozawa model and Mo equation were employed to describe the non-isothermal crystallization process of poly (lactic acid) (PLA), PLA/CB and PLA/modified carbon black (MCB) composites. It is found that the Ozawa model fail to describe the non-isothermal crystallization process for PLA and its composites, while Jeziorny equation and Mo’s theory provide a good fitting. The comparison of crystallization kinetics between PLA/MCB and PLA through Lauritzen–Hoffman model indicates that there appears a transition from regimes II to III in PLA and PLA/MCB. The fold surface free energy σ _e of PLA/MCB composite is higher than that of neat PLA, implying that the existence of nucleating agent is unfavorable for the regular folding of the molecule chain.     

Uniaxial Orientation and Crystallization Behavior of Amorphous Poly(ethylene terephthalate) Fibers

The effects of drawing conditions on the orientation and crystallinity of poly(ethylene terephthalate) (PET) fibers were investigated by using optical birefringence, sonic velocity, and wide-angle X-ray diffraction measurements, respectively. The preferred condition for preparation of uniaxially oriented amorphous PET fibers was suggested. The crystallization behavior of oriented PET fibers under relaxed and fixed length conditions was investigated by using differential scanning calorimetry (DSC). The multi-overlapping peaks were observed in the non-isothermal DSC curves of oriented PET fibers under relaxed condition. The kinetics of non-isothermal crystallization of oriented PET fibers under relaxed condition was analyzed by using an equation which takes the multi-crystallization processes into account. The kinetic parameters of every process were obtained and the crystallization mechanism was discussed. The crystallization behavior under fixed length condition differs from that under relaxed condition.