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。     

Thermal and morphological characterization of composites prepared by solution crystallization method of high‐density polyethylene on carbon nanotubes

The morphology, nucleation, and crystallization of polyethylene/carbon nanotubes composites prepared by solution crystallization method of high density polyethylene on Multiwall Carbon Nanotubes (MWNTs) are studied. Transmission electron microscopy (TEM) results show that the center stems of MWNTs are decorated with lamellar crystals. The nonisothermal crystallization kinetics of pure PE and PE/MWNTs composites are investigated by differential scanning calorimetry at various cooling rates. It is found that the Avrami analysis modified by Jeziorny and Mo can describe the nonisothermal crystallization process of pure PE and PE/MWNTs very well. The difference in the value of exponent between PE and PE/MWNTs suggests that addition of the MWNTs influences the mechanism of nucleation and the growth of PE crystallites. On one hand, the increasing of temperature corresponding to the maximum rate of crystallization and the onset crystallization temperature and the study of the nucleation activity reveal that the inorganic component (MWNTs) can act as the nucleating agent to facilitate the crystallization of PE in the hybrids. On the other hand, the decreasing degree of crystallinity and the increasing of half‐crystallization time imply that the MWNTs networks confine the crystallization of PE. POLYM. COMPOS., 2010. © 2009 Society of Plastics Engineers     

NaCl／PEO成核剂对玻纤增强PET力学性能及结晶的影响

考察了氯化钠(NaCl)／聚氧化乙烯(PEO)作为成核剂对玻纤增强PET复合材料的力学性能和结晶性能的影响。与常用的成核剂苯甲酸钠进行了比较，发现NaCl／PEO具有比苯甲酸钠更好的成核效果和促进结晶作用，制得的复合材料具有更高的模量和更好的表面光洁度。分析NaCl／PEO对玻纤增强PET体系结晶性能的影响机理，我们认为可能在较高的加工温度下NaCl与PEO发生反应生成。PEO-Na^ 络合物，降低了PET的玻璃化转变温度，并提供了新的结晶生长点。     

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。     

Investigation of the effect of nano-clay type on the non-isothermal crystallization kinetics and morphology of poly(3(R)-hydroxybutyrate) PHB/clay nanocomposites

PHB is a thermoplastic biopolymer produced by fermentation of renewable resources. Secondary crystallization during storage leading to an increased degree of crystallinity is a principal reason of PHB brittleness. In addition, pure PHB has no residues of catalysts, meaning low nucleation density and slow crystallization rates, leading to the formation of large spherulites with cracks and brittleness. To overcome the brittleness of PHB, polymer composites based on PHB, plasticizers, and nano-clays A and B were prepared by solvent casting. The addition of plasticizer decreases T _g from 5 to ?13 °C in all composites. Furthermore, the addition of nano-clays acts as a nucleating agent to PHB. The effect of nano-clays A and B on spherulites morphology, thermal behavior, and crystal structure of PHB composites were tested by several techniques. Differential scanning calorimetry analysis shows that the addition of nano-clay A does not change the crystallization temperature and the crystallization half-time (t _1/2) of the PHB matrix but that nano-clay B accelerates the crystallization process. Thermogravimetric analysis revealed an increase in thermal stability of composites containing nano-clay B. Polarized optical microscopy showed that nano-clays serve as nucleating agents in PHB matrix. Therefore, the spherulites become smaller and the nuclei density increases at the selected crystallization temperature, compared to pure PHB.     

成核剂对PET/PEN共混物性能影响及其机理研究

利用差示扫描量热法、X射线衍射和转矩流变测试等手段,研究了成核剂碳酸氢钠、苯甲酸钠和乙烯-甲基丙烯酸离子键聚合物(Surlyn)对聚对苯二甲酸乙二醇酯/聚萘二甲酸乙二醇酯（PET/PEN）共混物结晶性能和力学性能的影响。结果表明,3种成核剂均能显著提高共混物的成核作用,其中,Surlyn和苯甲酸钠能明显提高共混物结晶性能,结晶峰温度提高约20 ℃,结晶速度提升近1倍;3种成核剂中,只有Surlyn在提高结晶性能的同时,还能提高共混物的力学性能;Surlyn是PET/PEN共混物理想的成核剂。     

An investigation on the rheology,morphology, thermal and mechanical properties of recycled poly (ethylene terephthalate) reinforced with modified short glass fibers

This work was done with the aim to solve an important environmental issue regarding poly (ethylene terephthalate), (PET) wastes. Samples of recycled PET (r-PET) were reinforced with 10 to 30 wt% modified short glass fibers (SGF) through a melt mixing process in an internal mixer and their performance were assessed and compared with those of commercial glass reinforced PET through investigation of their rheology, morphology, thermal, and mechanical properties. It was found that the mechanical properties of the glass reinforced r-PET composites in most cases were comparable or even higher than those of the commercial grades. The impact strength of the 30 wt% SGF filled r-PET composite was about 30% higher than the commercial grades. This led to a conclusion that the PET wastes can be successfully converted to easily moldable thermoplastic materials by incorporation of 30 wt% SGF having a good balance of properties. Through investigation of rheological and morphological properties the optimum conditions for the best reinforcement performance were determined. The r-PET with 30 wt% glass fiber content showed the highest level of orientation and improved interaction with the r-PET matrix while having an acceptable flow behavior and processability. In spite of significant fiber breakage during the melt mixing process, leading to about 20 times reduction in the fiber aspect ratio, the composites maintained their good mechanical properties and showed a shear thinning behavior at high shear rates. The incorporated glass fibers acted as nucleating agents and improved the crystallization rate of r-PET leading to an overall increase in the crystallinity. POLYM. COMPOS., 2009. © 2008 Society of Plastics Engineers     

成核剂对PET结晶行为及形态结构的影响

系统地研究了四种成核剂:N-A、液晶VectraA950、滑石粉(Talc)、乙撑双硬脂酰胺(EBS)对聚对苯二甲酸乙二醇酯(PET)的结晶行为的影响。采用差式扫描量热仪(DSC)研究了PET/成核剂复合体系的非等温结晶行为,通过小角激光散射(Sals)、X衍射(XRD)对PET/成核剂复合体系的晶体尺寸和晶体结构进行了研究。结果表明,引入成核剂后,PET的结晶行为有较大改善,结晶峰向高温方向移动,且变尖锐,结晶尺寸变小,结晶度提高,除EBS外,均使PET结晶诱导时间减少。在这四种成核剂中,离子聚合物成核剂N-A成核效果最好。     

无机成核剂改性聚酰胺6/碳纤维复合材料的结构与性能

以钛酸钾晶须（PTW）、高岭土（Kaolin）和滑石粉（Talc）为成核剂,制备了无机成核剂改性聚酰胺6/碳纤维（PA6/CF/NA）三元复合材料。通过分析复合材料的力学性能、动态热力学性能、微观形貌、结晶行为、晶体结构、热性能等对其结构和性能进行了系统的研究。结果表明,加入Talc可以大幅提高PA6/CF复合材料的冲击性能,添加2%（质量分数,下同）的Talc时,复合材料的冲击强度提高了44.5%;Talc在挤出过程中能够充分解离成片层并均匀地分散在PA6基体中,PA6/CF/Talc复合材料中存在大量纤维拔出后形成的孔洞,片层与基体黏结较好;与PTW和Kaolin相比,Talc突出的异相成核作用可以显著提高PA6/CF复合材料的结晶温度,并促进PA6形成更为完善的晶体结构。     

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.     

Poly(ethylene terephthalate) nanocomposite fibers with functionalized multiwalled carbon nanotubes via in-situ polymerization

Poly(ethylene terephthalate) (PET) hybrids with newly synthesized functionalized multiwalled carbon nanotubes (MWNTs) were obtained by carrying out the in situ polycondensation of ethylene glycol with dimethyl terephthalic acid. The PET hybrids were melt-spun to produce monofilaments with various functionalized MWNT contents and draw ratios (DRs). The thermomechanical properties and morphologies of the PET hybrid fibers were determined using differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), wide angle X-ray diffraction (XRD), electron microscopy (SEM and TEM), and a universal tensile machine (UTM). The XRD analysis and TEM micrographs show that the levels of nanosize dispersion can be controlled by varying the MWNT content. It was found that the addition of only a small amount of functionalized MWNTs was sufficient to improve the properties of the PET hybrid fibers. The maximum enhancement in the ultimate tensile strength was found to arise at a functionalized MWNT content of 0.5 wt %. However, the initial modulus was found to increase linearly with increases in the functionalized MWNT loading from 0 to 1.5 wt %. The thermal properties and conductivities of the PET hybrid fibers were found to be better than those of pure PET fibers. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Ideal surface geometries of nucleating agents to enhance cell nucleation in polymeric foaming processes

Ideal nucleating agents are expected to improve the cell morphology of plastics foams (i.e., increasing the cell density, reducing the cell size, and narrowing cell-size distribution) by providing heterogeneous nucleation sites. A nucleating agent's surface geometry is one factor that governs its nucleating power. This paper discusses the surface geometry of an ideal nucleating agent. On the basis of computer simulations of a batch foaming process using polystyrene and carbon dioxide, we found that nucleating agents having numerous crevices with small semiconical angles are the most desirable for polymeric foaming processes. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci 2008     

Structure and properties of PP/SBS/glass fiber hybrid composites. Part I: Crystallization behavior and morphology

The structure development, crystallization behavior and morphology were studied in hybrid composites made with polypropylene/styrene‐butadiene‐styrene (PP/SBS) containing glass fibers (GF). The techniques applied include optical polarizing microscopy, X‐ray diffraction and scanning electron microscopy (SEM). The isothermal crystallization studies of PP/SBS/GF revealed that SBS as well as GF could act as good nucleating agents for PP. However, the nucleation efficiency of GF is much higher than that of the SBS. At high concentrations of SBS (> 30%), the crystallization rate decreases even in the presence of GF. This was attributed to the strong bonding between SBS and glass, giving rise to an intermediate layer of SBS between PP and GF, which was confirmed from the SEM of the fractured morphology of the injection molded hybrid composite. The orientation of GF was observer in the injection molded samples for certain compositions, and this was accompanied by an increase of intensities of particular diffraction peaks in the XRD.     

Effect of nanoclay type on dyeability of polyethylene terephthalate/clay nanocomposites

Polyethylene terephthalate (PET)-based nanocomposites containing three differently modified clays were prepared by melt compounding. The influence of type of clay on disperseability, thermal, and dyeing properties of the resultant nanocomposite was investigated by various analytic techniques, namely, X-ray diffraction, optical microscopy (OPM), differential scanning calorimetry, thermal gravimetric analysis, dynamical mechanical thermal analysis, contact angle measurement (CAM), reflectance spectroscopy, and light fastness. OPM images illustrated formation of large-sized spherulites in pure PET, while only small-sized crystals appeared in PET/clay nanocomposites. Decreased glass transition temperatures for all PET/clay nanocomposites indicate that the amorphous regions of such composites become mobile at lower temperatures than those in pure PET. CAMs on the resultant PET composites demonstrated that the wettability of such composites depends on hydrophilicity of the nanoclay particles. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Crystallization processes in poly(ethylene terephthalate) as modified by polymer additives and fiber reinforcement

The effect of fiber reinforcement on the crystallization kinetics of poly(ethylene terephthalate), or PET, was investigated using differential scanning calorimetry. The objective of the study was to determine how the effects of fiber reinforcement on PET crystallization are modified by the presence of polymer nucleating and plasticizing additives. Undirectional fiber composites were prepared using aramid and glass fibers in PET. The rate of crystallization of PET, as reflected by crystallization half-time, is seen to depend on reinforcing fiber type, crystallization temperature, and presence of nucleant or plasticizer. Howerver, degree of crystallinity of PET is largely unaffected by the presence of additives and reinforcing fibers. Crystallization kinetics are analyzed using the Avrami model for PET volume crystallized as a function of time. Avrami plots for PET and fiber-reinforced PET exhibit two linear regions, possibly corresponding to primary and secondary crystallization. The crystalline morphology of fiber-reinforced PET was also studied using polarized light microscopy. Results concerning nucleation density and growth morphology are used in explaining differences seen in crystallization kinetics in fiber-reinforced systems. © 1994 John Wiley & Sons, Inc.     

Effects of hybrid nucleating agents on glass fiber‐reinforced polyethylene terephthalate/polybutylene terephthalate alloy crystallization

In this article, the Surlyn® 8920 and AX 8900 were mixed as hybrid nucleating agents for glass fiber (GF)‐reinforced polyethylene terephthalate (PET)/polybutylene terephthalate (PBT) alloy. The crystallization behaviors on GF‐reinforced PET/PBT alloy with compound nucleating agents of Surlyn® 8920 and AX 8900 were studied by differential scanning calorimeter. The Jeziorny method, Mo method, and Kissinger method were used for studying the non‐isothermal crystallization process of the composite alloys. While single AX 8900 cannot further improve the crystallization properties of the alloy and reduced the crystallization rate, the introduction of Surlyn® 8920 can effectively ameliorate the condition. The results demonstrated the hybrid nucleating agents of Surlyn® 8920 and AX 8900 not only can accelerate crystal growth, but also can significantly reduce the energy barrier, and it has a good effect in the alloy to the nucleation. POLYM. COMPOS. 37:1167–1172, 2016. © 2014 Society of Plastics Engineers     

Crystallization and Morphology of Poly(ethylene 2,6‐naphthalene dicarboxylate) Containing Additives

The influence of nucleating agents (AClyn^®, Surlyn^® and sodium benzoate (SB)) alone and together with nucleating promoter (Ceraflour^® 993 and Ceraflour^® 991 and poly(1,4‐butylene sebacate)) on the crystallization and morphology of poly(ethylene 2,6‐naphthalene dicarboxylate) (PEN) was investigated by means of differential scanning calorimeter, polarized optical microscopy and small angle light scattering. It was revealed that AClyn, Surlyn and SB effectively accelerate nucleation and crystallization of PEN with increasing the ratio of nucleating agent up to 1 wt.‐%. A combination of nucleating agent and nucleating promoter leads to further increase in crystallization rate at low temperature, but only a slight change at high temperature. Hedrites were obtained in pure PEN and the addition of SB and Ceraflour 993 produces small crystals with poor perfection upon crystallization in high temperature region. When crystallization temperature was below 210 °C, spherulites were observed in pure PEN and also in the samples of PEN/Ceraflour 993 and PEN/SB but with smaller size.

Crystal morphology of PEN crystallized at 240 °C for 40 min.     

多壁碳纳米管/高密度聚乙烯复合材料的导电行为研究

采用超声波分散溶液混合法,制备出导电性能优良的多壁碳纳米管(MWNTs)/高密度聚乙烯(HDPE)导电复合材料。研究了不同含量及长径比的MWNTs对HDPE导电性能的影响。结果表明:MWNTs可以显著提高复合材料的导电性,其体积电阻率由1017Ω.m降至107Ω.m;长径比较小的MWNTs分散性较好,并能显著提高材料的PTC(正温度系数效应)强度,当w(MWNTs-60100)=7%(相对于材料总质量而言)时,材料的PTC强度达到2.8。采用差示扫描量热(DSC)法分析了复合材料的结晶行为,证明MWNTs可以成为HDPE的成核剂,并能提高HDPE的成核速率,使晶粒尺寸分布变窄。     

Crystallization and chain adsorption of poly(etheretherketone) in discontinuous pitch-derived carbon fiber composites

The crystallization kinetics of poly(etherether ketone) (PEEK) in chopped mesophase pitch-derived carbon fiber/PEEK composites have been studied. Various processing techniques are used in order to obtain controlled fiber length in the composites. Scanning electron microscopy performed on properly etched long fiber composite samples reveals that the nucleating sites density is low at the carbon fiber surface: transcrystalline layers are rarely observed. This is confirmed by differential scanning calorimetry. However, samples processed by mixing carbon fibers and molten polymer in a high temperature mixer have a widely different behavior: the nucleation density and the crystallization rate increase, the glass transition of these samples is displaced towards higher temperatures, and the solubility is dramatically lowered. We ascribe these phenomena to the adsorption of the polymer chains on carbon particles created by attrition during the mixting.     

An efficient way to improve the mechanical properties of polypropylene/short glass fiber composites

Enhancement of tensile strength, impact strength, and flexural strength of polypropylene/short glass fiber composites by treating the glass fibers with coupling agent, mixing with maleated polypropylene (MPP) for compatibilization and adhesion, and with nucleating agent for improvement of polypropylene crystallization was studied. The results showed that both the silane coupling agent and MPP enhance tensile strength, impact strength, and flexural strength. In the absence of MPP, the effect of silane coupling agent on the mechanical properties of the composites decreases in the following order: alkyl trimethoxy silane (WD‐10) > γ‐methacryloxypropyl trimethoxysilane (WD‐70) > N‐(β‐aminoethyl)‐γ‐aminopropyl trimethoxysilane (WD‐52), whereas in the presence of MPP, the order changes as follows: WD‐70 > WD‐10 > WD‐52. When the glass fibers were treated with WD‐52, 4,4‐diamino‐diphenylmethane bismaleimide (BMI) can further enhance the mechanical properties of the composite. The three kinds of strengths increase with MPP amount to maximum values at 5% MPP. As a nucleating agent, adipic acid is better than disodium phthalate in improving the mechanical properties, except for the notched impact strength. Wide‐angle X‐ray diffraction showed that the adipic acid is an α‐type nucleating agent, whereas disodium phthalate is a β‐type nucleating agent. Blending with styrene–butadiene rubber can somewhat improve the notched impact strength of the composites, but severely lowers the tensile strength and bending strength. Scanning electron micrographs of the broken surface of the composite showed greater interfacial adhesion between the glass fibers and polypropylene in the modified composite than that without modification. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 96: 1414–1420, 2005