r-PET扩链增粘工艺及其单丝力学性能

在废旧聚对苯二甲酸乙二酯(r-PET)泡泡料中分别加入2,2'-(1,3-亚苯基)二恶唑啉(BOZ)、均苯四甲酸二酐(PMDA)扩链剂,利用双螺杆反应挤出进行扩链试验,并经熔融纺丝后多级拉伸制得r-PET单丝。通过改变扩链剂含量、挤出温度、停留时间以及抽真空条件,对扩链后的r-PET特性黏度以及单丝力学性能等进行了测试。结果表明,抽真空可显著提高扩链效果;BOZ质量分数为2.5%时,在250℃下停留60 s,特性黏度上升最高为0.77 dL/g,单丝断裂强度为4.9 cN/dtex,断裂伸长率为21.4%;PMDA质量分数为1.25%时,在260℃下停留60 s,特性黏度上升最高为0.82 dL/g,单丝断裂强度为5.2 cN/dtex,断裂伸长率为15.6%;BOZ与PMDA联用时,其含量应比各自单独扩链时的最佳含量低,当联用体系中BOZ质量分数为2%,PMDA质量分数为0.75%时,在270℃下停留60 s,r-PET特性黏度可达0.88 dL/g,单丝断裂强度为5.8 cN/dtex,断裂伸长率为18.2%。     

Chain extension and branching of poly(ethylene terephthalate) (PET) with di- and multifunctional epoxy or isocyanate additives: An experimental and modelling study

The effect of two difunctional chain extenders, 1,6-diisocyanatohexane (NCO) and 1,4-butanediol diglycidyl ether (EPOX), in the reactive melt-processing of a post-consumer poly(ethylene terephthalate) (r-PET) was investigated. The torque evolution during processing in a batch mixer and the molecular weight of the chain-extended r-PET, as determined by SEC analysis, were comparatively evaluated. A simple mathematical model proposed here was used to fit the obtained molecular weights. Two polyfunctional chain extenders, poly(phenyl isocyanate-co-formaldehyde) (P-NCO) and a styrene-acrylate copolymer bearing epoxide groups (P-EPOX), were also used and their reactivity was compared with that of the difunctional ones by analysing torque and melt flow rate data. The different reactivity of the two functional groups and the structure of the final polymer (either linear or branched depending on the type of chain extender) affect both crystallization behaviour and tensile properties of the modified r-PET. Fine tuning of the latter properties by suitable chain extender(s) selection and formulation is anticipated.     

Modification of poly(ethylene terephthalate) by combination of reactive extrusion and followed solid‐state polycondensation for melt foaming

A combination of reactive extrusion and followed solid‐state polycondensation (SSP) was applied to modify the virgin fiber grade poly(ethylene terephthalate) (v‐PET) and recycled bottle‐grade PET (r‐PET) for melt foaming. Pyromellitic dianhydride (PMDA) and triglycidyl isocyanurate (TGIC) were chosen as the modifiers for the reactive extrusion performed in a twin‐screw extruder. For comparison, commercially available chain extender ADR JONCRYL ADR‐4370‐S was also used. The characterizations of the intrinsic viscosity, i.e., [η], and rheological properties whose changes were correlated to the long chain branches introduced in the molecular structure were performed on the modified PET to evaluate their chain extension extent. The results revealed that the [η] of 1.37 dL/g was obtained for PMDA modified v‐PET while that of 1.15 dL/g for TGIC modified r‐PET. Such difference was attributed to the different reactivity of the two chain extenders with the two types of PET. Increases in shear viscosity and storage modulus, and the high pronounced shear thinning behavior were also observed in the modified PET. Finally, the foamability of the certain modified PET was verified by the batch melt foaming experiments. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42708.     

Molecular structure and rheological properties of a poly(ethylene terephthalate) modified by two different chain extenders

This paper compares the molecular structure and rheological properties of a commercial poly(ethylene terephthalate) (PET) after reactive processing with different concentrations of either pyromellitic dianhydride (PMDA) or a multifunctional epoxide (Joncryl®ADR-4368) as a chain extender. By size exclusion chromatography with triple detection, an increase of molar mass, a broadening of molar mass distribution, and the generation of long-chain branched molecules were found for both chain extenders. While gel-free materials were obtained with PMDA, the processing with Joncryl leads to the formation of gels. The effect of branching, indicated by the Mark–Houwink exponent, is more pronounced for materials with Joncryl compared to PMDA and points to a more compact branching structure of the PET/Joncryl molecules. Rheological measurements in shear and elongation support the analysis from SEC and reveal a complex tree-like branching structure for both chain extenders. In addition, the role of the two modifiers with respect to processing was assessed.     

Effect of Two‐Step Chain Extension using Joncryl and PMDA on the Rheological Properties of Poly (lactic acid)

This research considers a two‐step chain extension reaction in the presence of two chain extenders, Joncryl and Pyromellitic dianhydride (PMDA), as a solution for poor melt properties of poly (lactic acid) (PLA). The aim of adding PMDA is to increase the carboxyl groups via the anhydride ring‐opening reaction so that the reaction between PLA and Joncryl could be facilitated since the reactivity between the epoxy and carboxyl group is more than epoxy and hydroxyl group. The reactions are confirmed by measuring the acid value, and a two‐step reaction mechanism is suggested. Shear and elongational rheological properties of the samples are investigated; furthermore, gel permeation chromatography analyses and tensile tests are exploited for studying the molecular weight and tensile properties, respectively. The results show that the chain extension reactions lead to an increase in the storage modulus, complex viscosity, and molecular weight. Also, the PLA chains which are extended utilizing both chain extenders simultaneously evince a synergistic improvement in the shear and elongational rheological properties due to longer segments between branching points on the structure.     

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     

扩链剂联用对PETG扩链反应与流变性能的影响

通过扩链反应对聚对苯二甲酸乙二醇1,4环己烷二甲醇酯（PETG）进行改性以提高PETG的熔体强度和黏度。采用熔体流动速率仪、旋转流变仪及转矩流变仪考查了扩链剂的使用方式对PETG结构及流变性能的影响。结果表明,酸酐类和环氧类多官能团单体联用对PETG的扩链效果最好,PETG的熔体流动速率由12.83 g/10 min降低至7.50 g/10 min,零剪切黏度（η0）由2022.8 Pa·s增加到4764.2 Pa·s,特征松弛时间（τ0）由0.78 s增加到3.58 s;改性后PETG仍保持着线形结构而未形成凝胶。     

Rheological/thermal properties of poly(ethylene terephthalate) modified by chain extenders of pyromellitic dianhydride and pentaerythritol

Due to low molecular weight and wide molecular weight distribution, polyethylene terephthalate (PET) shows weak melt strength properties. In this study, the synergistic effect of using different types of chain extenders and catalyst on rheological behavior of PET has been investigated. Long-chain branching is known as a suitable method for developing the structure of PET during reactive melt processing. Thus, pyromellitic dianhydride (PMDA) and pentaerythritol (PENTA) were added to the fiber grade PET. The best formulation was determined based on rheological results, which revealed an improvement in both storage modulus and complex viscosity of PMDA-modified samples. Samples containing 1.5% PMDA and 0.5% PENTA exhibited the best rheological properties. Also, dibutyltin dilaurate (DBTDL) acted as an accelerator for chain extension reaction during reactive melt blending. Subsequently, the rheological properties were improved by increasing the chain extending rate. Moreover, thermal properties such as crystallization and melting temperatures and the degree of crystallinity for modified PET were investigated by differential scanning calorimetry.     

扩链剂对聚对苯二甲酸乙二醇酯流变性能和发泡性能影响

采用均苯四甲酸酐（PMDA）作为聚对苯二甲酸乙二醇酯(PET)的扩链剂制备了扩链改性PET（CEPET）,并以超临界二氧化碳(CO2)为物理发泡剂,采用釜压法制备了CEPET泡沫;通过旋转流变仪和扫描电子显微镜研究了CEPET的流变性能和CEPET泡沫的泡孔结构。结果表明,随着PMDA含量的增加,CEPET试样的储能模量逐渐增加,损耗因子逐渐降低,CEPET的熔体强度明显高于纯PET;CEPET泡沫的泡孔形态得到改善,发泡倍率得到提高;加入1.0 份（质量份,下同）扩链剂时,发泡倍率能够达到32.55倍。     

Expanding the application field of post‐consumer poly(ethylene terephthalate) through structural modification by reactive blending

With the aim of up‐grading the material properties of post‐consumer PET, making them suitable for extrusion of thermoformable thick sheets, a series of polyepoxy chain extenders have been comparatively evaluated as melt viscosity modifiers for a toughened compatibilized blend containing up to 80 wt % of bottle‐grade post‐consumer recycled poly(ethylene terephtalate) (r‐PET). Combinations of a commercial modifier with pentaerythritol were also successfully employed to cause simultaneous hyperbranching and controlled chain scission, thereby modifying the melt rheology of the material without excessively increasing the molecular weight, as highlighted by common technological melt viscosity measurements such as online torque and off‐line melt flow rate (MFR). Since the high melt fluidity of PET plays a critical role on its flame resistance, the combined effect of chain extenders and halogen‐free phosphorated additives on the fire resistance of the modified toughened blends was also investigated. Preliminary results indicate that the chemical reactions among polymer and additives must be taken into careful account to prevent unfavorable effects on the ultimate melt rheology and mechanical properties. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40881.     

各种扩链剂对PET瓶片反应挤出扩链作用的研究

分别采用甲苯二异氰酸酯、三氧化二锑、邻苯二甲酸酐、均苯四酐、萘四甲酐以及均苯四酐和邻苯二甲酸酐混合物作为聚对苯二甲酸乙二醇酯（PET）瓶片的扩链剂,研究了反应挤出后产物特性黏度的变化。结果表明,甲苯二异氰酸酯、三氧化二锑、邻苯二甲酸酐和萘四甲酐对PET瓶片的扩链效果较弱;均苯四酐可明显提高PET的特性黏度。均苯四酐和邻苯二甲酸酐复配后的扩链效果最为显著;当均苯四甲酸二酐用量为0.3 %、邻苯二甲酸酐用量为0.2 %时,PET的特性黏度达到0.96 dL/g。     

r-PET/OBC/OBC-g-(GMA-co-St)共混材料的制备及性能

以自制的甲基丙烯酸缩水甘油酯/苯乙烯熔融接枝乙烯-辛烯嵌段共聚物(OBC-g-(GMA-co-St))为相容剂,回收聚对苯二甲酸乙二醇酯(r-PET)为基体材料,乙烯-辛烯嵌段共聚物(OBC)为增韧材料,通过高速混合、双螺杆挤出、注塑成型等工艺制备了r-PET/OBC/OBC-g-(GMA-co-St)共混材料,并利用扫描电子显微镜(SEM)、差示扫描量热仪(DSC)、动态热机械分析仪(DMA)测试并分析了OBC-g-(GMA-co-St)对r-PET/OBC共混材料界面性能、结晶性能、储能模量等的影响,另外还通过拉伸和冲击试验测试了r-PET/OBC/OBC-g-(GMA-co-St)共混材料的力学性能。结果表明:随着OBC-g-(GMA-co-St)用量的增加,r-PET/OBC/OBC-g-(GMA-co-St)共混材料的拉伸强度呈先增大后减小趋势,断裂伸长率大幅度上升然后趋于平缓,缺口冲击强度随之增大,弯曲强度则有所降低。其中,在OBC-g-(GMA-co-St)用量为1.5%的r-PET/OBC/OBC-g-(GMA-co-St)共混材料中,OBC球状粒子嵌入了r-PET基体,二者界面黏结力增强。与纯r-PET相比,该共混材料的熔融温度和结晶温度升高,过冷度和结晶度降低,玻璃化转变温度向低温方向移动,储能模量略有降低,另外,其断裂伸长率和缺口冲击强度分别提高了260.97%和119.64%。     

Melt rheological properties of ETFE: an attempt to illuminate the fluorine-substitution effect

Flow behaviors and rheological properties of ethylene tetrafluoroethylene alternating copolymer (ETFE) under high-shear conditions were first reported. Flow instabilities, shear and extensional viscosities, and die swell of ETFE were investigated. Rheological behaviors of perfluorinated ethylene propylene copolymers (FEP), partially fluorinated ETFE, and non-fluorinated polyethylenes (PE) were compared for understanding the role of fluorine incursion on materials properties. It is found that (1) ETFE does not have sharkskin region or second smooth region which frequently occurs in FEP and linear PE; (2) critical shear stresses at which surface melt fracture occurs for the three polymers follow the order: FEP?<?ETFE?<?PE; (3) stable flow region narrows, die swell weakens, and flow activation energy increases when fluorine content of polymer increases. After time?Ctemperature superposition, shifted shear viscosity, extensional viscosity, and elastic data (die swell) present universal scaling characteristic and superpose well in term of the same shift factors.     

Melt foamability of reactive extrusion‐modified poly(ethylene terephthalate) with pyromellitic dianhydride using supercritical carbon dioxide as blowing agent

By reactive extrusion with pyromellitic dianhydride (PMDA), foamable poly(ethylene terephthalate) (PET) was obtained, which achieved a maximum intrinsic viscosity of 1.36 dL/g with PMDA content 0.8 wt%. Dynamic shear rheological properties were measured to characterize the structure evolution of modified PET. And the Avrami analysis was extended for the non‐isothermal crystallization process of modified PET, which relates to cell stabilization in the melt foaming process. Based on the batch foaming process with supercritical carbon dioxide as blowing agent, broad foaming temperature windows were obtained for PETs modified with 0.8 and 0.5 wt% PMDA, in which PET foams with the expansion ratio between 10 and 50 times, the cell diameter between 15 and 37 μm, and the cell density between 6.2 × 10⁸ and 1.6 × 10⁹ cells/cm³ were controllably produced. POLYM. ENG. SCI., 55:1528–1535, 2015. © 2014 Society of Plastics Engineers     

反应挤出过程中PET扩链反应的研究

分别加入羧基加成型的双噁唑啉(BOZ)和羟基加成型的均苯四甲酸酐(PMDA)为扩链剂,考察了反应挤出前后PET特性黏度([η])和羧基值的变化情况。实验结果表明:BOZ的扩链效果不明显;PMDA能较大程度地提高PET的[η],但产品羧基值较高;BOZ和PMDA联用可得到高[η]低羧基值的产品,扩链效果最佳。当挤出机工艺条件为:反应段温度260℃、螺杆转速45 r/min、反应段压力1 kPa、BOZ和PMDA质量分数均为0.2%时,可得到[η]为0.90 dL/g,羧基值为25 mol/t的PET产品。     

Preparation of long‐chain branched poly(ethylene terephthalate): Molecular entanglement structure and toughening mechanism

Poly(ethylene terephthalate) (PET) was long‐chain branched (LCB) by ring‐opening reaction with both pyromellitic dianhydride and tetrahydrophthalic acid diglycidyl ester as chain extenders through reactive melt processing. It was found that with the increase of chain extenders dosage, the intrinsic viscosity of PET increased and melt index decreased greatly, while both the tensile strength and impact strength of PET were remarkably improved. The elastic modulus (G′) and viscous modulus (G″) were enhanced by chain branching. Compared with PET, the complex viscosities of LCB‐PET were much higher at full frequency range, and obvious shear thinning was presented. The Cole–Cole curve deviated from the semicircular shape and the curve end was inclined to upward in high viscosity region, indicating the formation of the multiple hierarchical structures. The molecular weight of the branch (M_B) was much greater than critical entanglement molecular weight (M _e), which essentially confirmed the existence of LCB structure and fairly strong molecular entanglement in the LCB‐PET molecular chain. When subjected to external force, the entanglement point, acting as physical crosslinking point between the molecules, was in favor of increasing the molecular interaction, reducing the molecular slippage, and bearing a large deformation. POLYM. ENG. SCI., 59:1190–1198 2019. © 2019 Society of Plastics Engineers     

HDPE/r-PET原位微纤物微观形态与力学性能

以高密度聚乙烯(HDPE)和回收聚对苯二甲酸乙二醇酯(r-PET)为原料,通过反应挤出、冷拉伸、退火工艺制备了HDPE/r-PET原位微纤物。研究了扫描电镜(SEM)的制样方法即用液氮冷冻、脆断样品、聚四氟乙烯带包覆、在沸腾的二甲苯中刻蚀7～10min和不同r-PET用量、不同拉伸比制备出的系列HDPE/r-PET原位微纤物的力学性能。结果表明,通过SEM可清晰地看到形成的微纤,原位微纤物的拉伸强度和冲击强度都随拉伸比的增大而增大;r-PET质量分数为15%时,原位微纤物的拉伸强度和无缺口冲击强度达到最大值;HDPE/r-PET原位微纤物的适宜注塑温度为210℃。     

r-PET/POE/EAA共混材料性能的研究

以回收聚对苯二甲酸乙二醇(酯r-PET)为基体材料,乙烯-辛烯共聚(物POE)为增韧材料,乙烯-丙烯酸共聚物(EAA)为相容剂,制备了r-PET/POE/EAA共混材料。用DSC、SEM分析了POE及EAA对r-PET结晶性能、断面结构的影响,并测试了共混材料的力学性能。结果表明:加入12%POE后,r-PET/POE共混材料的熔融温度降低了1.76℃,结晶度降低了16.49%,断裂伸长率及缺口冲击强度明显提高,弯曲强度和拉伸强度略有下降;在r-PET/POE共混材料中加入1.5%EAA后,POE球状粒子嵌入r-PET基体中,二者相容性提高,结晶速率加快;与纯r-PET相比,r-PET/POE/EAA共混材料的断裂伸长率和缺口冲击强度分别提高了698.01%和227.45%柔,韧性也大幅度提高。     

Effect of copolymers synthesized by nitroxide‐mediated polymerization as chain extenders of postconsumer poly(ethylene terephthalate) waste

In this contribution, the use of glycidyl methacrylate and styrene copolymers synthesized by nitroxide‐mediated polymerization (NMP) as chain extenders of postconsumer poly(ethylene terephthalate) waste (r‐PET) is described. Our observations revealed that the copolymers synthesized by NMP act as efficient chain extenders for the regeneration of PET waste. Epoxide groups in the copolymers react with PET end reactive groups producing chain extended PET with higher molecular weight and improving performance. The increase in molecular weight of PET waste results in important improvement in both, elongation‐at‐break, and strength impact. r‐PET complex viscosity and rheological moduli are also greatly improved as the epoxide content in the chain extenders increases. The loss tangent and phase angle versus angular frequency plots for chain‐extended r‐PET reveal that melt elasticity is also improved. These results confirm that use of NMP‐synthesized copolymers is a plausible solution for the recycling of PET. POLYM. ENG. SCI., 59:2255–2264, 2019. © 2019 Society of Plastics Engineers     

Reactively Modified Poly(lactic acid): Properties and Foam Processing

Summary: In order to produce modified poly(lactic acid) (PLA) resins for applications requiring high melt viscosity and elasticity (e.g., low‐density foaming, thermoforming), a commercial PLA product has been reactively modified in melt by sequentially adding 1,4‐butanediol and 1,4‐butane diisocyanate as low‐molecular‐weight chain extenders. By varying amounts of the two chain extenders associated to the end group contents of PLA, three resulted samples were obtained. They were then structurally characterized by FTIR spectroscopy and molecular structure analysis. Their thermal, dynamic mechanical thermal properties and melt viscoelastic properties were investigated and compared along with unmodified PLA. The results indicated that chemical modification may be characterized as chain scission, extension, crosslinking, or any combination of the three depending on the chain extender amounts. The increase of PLA molecular weight could be obtained by properly controlling amounts of two chain extenders. The samples with increased molecular weights showed enhanced melt viscosity and elasticity. Such property improvements promised a successful application for modified PLA in a batch foam processing by producing foams with reduced cell size, increased cell density and lowered bulk foam density in comparison with plain PLA foam.

Cellular morphology of a modified PLA foam.