均苯四甲酸二酐改性回收PET的研究

以扩链剂均苯四甲酸二酐对回收PET进行扩链增黏,从特性黏度和端羧基含量的变化考察了其扩链效果,并用DSC研究了不同添加量的扩链剂对回收PET的热性能的影响。结果表明,该扩链剂对回收PET具有良好的扩链增黏效果,并且当其质量分数为1.25%时,回收PET的特性黏度达到0.813 dL/g,可作为工程塑料使用;且影响PET的冷结晶行为。     

Modification of poly(vinyl alcohol) polymers by aliphatic carboxylic acids via reactive blending

The modification of poly(vinyl alcohol) with a series of long-chain aliphatic carboxylic acids via reactive blending was studied. The method involves the reaction in the melt of polymer hydroxyl groups with carboxylic acids using a laboratory scale reactor, a medium-scale Brabender rheomixer, and a large-scale twin-screw extruder. The presence of the long aliphatic chains acted as lubricants during reactive processing. The reactivity was generally low, and increased with decreasing chain length of the acids. All modified polymers displayed lower temperature thermal transitions and improved thermal stabilities compared to the parent polymer. Thermogravimetry established that polymers incorporating short chain residues were more thermally stable than their long-chain analogs. The polymer obtained in the twin-screw extruder showed a higher degree of incorporation with improved thermal stability compared to the polymers obtained in the laboratory mixer or the rheomixer. Intermediate degree of incorporation and thermal stability was exhibited by the polymers obtained in the rheomixer. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 69: 1885–1890, 1998     

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.     

扩链改性对聚对苯二甲酸乙二酯挤出吹膜成型的影响

通过添加多官能团环氧扩链剂对聚对苯二甲酸乙二酯(PET)进行扩链改性,然后用改性PET进行吹膜成型,研究了扩链剂含量对PET特性黏度、膜泡稳定性及薄膜力学性能和透明度的影响。结果表明,扩链剂的添加显著提升了PET的特性黏度;随着扩链剂含量的增加,薄膜膜泡稳定性以及表面质量、最大吹胀比、拉伸强度得到显著改善,断裂伸长率呈先增大后减小的趋势。当扩链剂质量分数为0.7%时,PET的特性黏度由纯PET的0.71 d L/g上升至0.94 d L/g,最大吹胀比则由1.9提高至4.5,横纵向拉伸强度分别为61.7 MPa和64.4 MPa,横纵向断裂伸长率达到最高,分别为12%和12.45%,较扩链剂质量分数为0.2%时提高了105.5%以及125.1%,而透光率仅下降1.4%,得到了性能较优的吹塑薄膜制品。     

2，2-双（2-噁唑啉）改性回收PET的研究

以扩链剂2，2-双(2-噁唑啉)对回收PET进行扩链增粘，从特性粘度和羧值的变化考察了其扩链效果，并用DSC法研究了不同添加量噁唑啉对PET热性能的影响。结果表明：双噁唑啉对PET有一定的扩链效果，且影响PET的冷结晶行为。     

扩链剂联用技术对PET扩链反应的影响

通过对PET扩链反应前后的特性粘数 [η]和羧基 [COOH]值的比较 ,讨论了扩链剂联用条件下不同扩链剂种类、用量以及加入方式对于扩链反应的影响。实验结果表明 ,扩链剂联用对于PET树脂增粘是一个良好的方法 ,可使扩链产物的特性粘数由 0 .62dL g增至 1.1dL g ,同时 [COOH]含量降至很低 ;少量荧光剂同时加入显著改善扩链产物的色泽。在一定的联用条件下扩链产物的热稳定性可保持在较好水平。     

Ultraviolet‐induced chain extension of poly(ethylene terephthalate) based on radical reaction with the aid of trimethylolpropane triacrylate and glycidyl methacrylate during extrusion

In order to improve the processing properties of poly(ethylene terephthalate) (PET), carbon–carbon double bonds were end‐capped onto the chain end of PET by reacting with glycidyl methacrylate (GMA) and then the product was reacted with trimethylolpropane triacrylate (TMPTA) based on a free radical reaction initiated by ultraviolet light to form long‐chain branching structures. The reaction was demonstrated by intrinsic viscosity measurements, carboxyl content analysis, Fourier transform infrared spectroscopy and size exclusion chromatography. Then the rheological and thermal properties of PET were investigated with various TMPTA and GMA contents. Chain extended PET displayed higher complex viscosity than pristine PET and pronounced shear‐thinning behavior. Moreover, the relaxation time spectrum revealed that the modified PET displayed a longer relaxation time during the relaxation process, which was attributed to the higher degree of entanglements resulting from long‐chain branching. Besides, its crystallization temperature and melt temperature shifted to lower temperatures, and the glass transition temperature shifted to higher temperature, indicating that the thermal properties of the modified PET had also been improved. Thus this method can be used to improve the overall properties of PET. © 2020 Society of Chemical Industry     

回收PET的反应挤出扩链

在回收的废弃聚对苯二甲酸乙二醇酯(PET)瓶片中添加不同质量分数的均苯四甲酸二酐（PMDA）和环氧树脂作为扩链剂,利用反应挤出技术在同向双螺杆挤出机中反应,分析测试反应产物的特性黏度、端羧基的质量摩尔浓度及结晶性能。结果表明： PMDA和环氧树脂均对PET有一定的扩链作用,且二者合用时扩链效果更佳,反应后PET的特性黏度由0.45 dL/g提高到0.58 dL/g,摩尔质量也显著提高;其中单独使用环氧树脂作为扩链剂时,可以使反应后的PET端羧基含量显著下降,结晶度有所提高。     

Properties of high‐speed spun high molecular weight poly(ethylene terephthalate) filaments

High‐speed spinning of high molecular weight poly(ethylene terephthalate) (PET) having an intrinsic viscosity of 0.98 dL/g was performed at the take‐up velocity range of 2.5–5.5 km/min. The structure of the as‐spun filaments was analyzed by density, birefringence, WAXS, DSC, boiling water shrinkage, and tensile properties. Stress‐induced crystallization takes place above 3 km/min, which is confirmed by the steep increase in density, the growth of the crystal size, melting point increase, and the decrease in boiling water shrinkage. The plot of crystallinity versus birefringence shows that crystallinity increases drastically after birefringence reaches the value of about 0.075. A comparison with the data of other researchers will clearly present the effects of molecular weight on the properties of PET filaments spun at high speed, for example, the take‐up velocity range of the steep increase in density for high molecular weight PET is lower than that for low molecular weight PET by about 1 km/min. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 71: 1283–1291, 1999     

Chain extension of recycled poly(ethylene terephthalate) with 2,2′‐(1,4‐phenylene)bis(2‐oxazoline)

The present work provides improved recycled high molecular weight poly(ethylene terephthalate) (PET) by chain extension using 2,2′‐(1,4‐phenylene)bis(2‐oxazoline) (PBO) as the chain extender. PBO is a very reactive compound toward macromolecules containing carboxyl end groups but not hydroxyl end groups. In the case of PET, where both species are present, for even better results, phthalic anhydride (PA) was added in the initial sample, before the addition of PBO. With this technique, we succeeded in increasing the carboxyl groups by reacting PA with the hydroxyl terminals of the starting polymer. From this modification of the initial PET sample, PBO was proved an even more effective chain extender. So, starting from a recycled PET with intrinsic viscosity [η] = 0.78, which would be [η] = 0.69 after the aforementioned treatment without a chain extender or M̄_n = 19,800, we prepared a PET grade having [η] = 0.85 or M̄_n = 25,600 within about 5 min. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 2206–2211, 2000     

聚对苯二甲酸丙二醇酯的热性能研究

研究了聚对苯二甲酸丙二醇酯 (PTT) ,PET ,CDP在不同温度和时间下的特性粘数和端羧基含量的变化。结果表明 ,一定温度下 ,PTT熔体特性粘数随熔融时间的延长而下降 ,一定时间下 ,随温度的升高而下降。PTT端羧基含量随温度升高而增大 ,PTT的热稳定性较PET明显下降。     

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。     

双酚A型氰酸酯的三聚体对PET扩链的影响

使用双酚A型氰酸酯(BADCy)的三聚体Tri-mer-60作为扩链剂,与BADCy单体进行对比,对聚苯二甲酸乙二醇酯(PET)进行扩链.通过比较扩链后的PET的熔体扭矩,发现三聚体对PET的扩链效果优于单体.并研究了不同含量的Tri-mer-60对PET的扭矩、特性黏度、羧基含量、流变性能以及结晶性能的影响.结果表明:随着Tri-mer-60含量的增加,扩链反应速度增加,PET的特性黏度增加,羧基含量降低.扩链反应的发生改善了PET的流变性能,但阻碍了PET的结晶.     

熔融挤出-固相增黏循环处理对PET性能的影响

将特性黏数为0.679 dL/g的纤维级聚对苯二甲酸乙二酯(PET)切片进行5次熔融挤出-固相增黏循环处理,对固相增黏后的PET切片进行纺丝,分析了处理后的PET切片的热性能,测试了PET纤维的断裂强度及色值。结果表明:随着PET熔融挤出-固相增黏循环处理次数的增加,固相增黏后PET切片的特性黏数下降,熔点降低,纤维断裂强度和断裂伸长率下降,色值b值增加,L值减小;5次固相增黏后PET切片的特性黏数均大于0.75 dL/g,但其可纺性变差,纤维力学性能下降。     

Blends of poly(ethylene terephthalate) and poly(butylene terephthalate)

Commercial grade poly(ethylene terephthalate), (PET, intrinsic viscosity = 0.80 dL/g) and poly(butylene terephthalate), (PBT, intrinsic viscosity = 1.00 dL/g) were melt blended over the entire composition range using a counterrotating twin‐screw extruder. The mechanical, thermal, electrical, and rheological properties of the blends were studied. All of the blends showed higher impact properties than that of PET or PBT. The 50:50 blend composition exhibited the highest impact value. Other mechanical properties also showed similar trends for blends of this composition. The addition of PBT increased the processability of PET. Differential scanning calorimetry data showed the presence of both phases. For all blends, only a single glass‐transition temperature was observed. The melting characteristics of one phase were influenced by the presence of the other. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 75–82, 2005     

Dynamic thermomechanical and tensile properties of chain-extended poly(ethylene terephthalate)

A series of chemically modified poly(ethylene terephthalate) (PET) samples was received after chain extension of a virgin sample at different reaction times with a new diepoxide as chain extender. These samples showed different intrinsic viscosity and degrees of branching or crosslinking. The effect of this differentiation on thermal properties was studied by dynamic mechanical thermal analysis and the determined T_g values were found to be in good agreement with those obtained by differential scanning calorimetry and thermomechanical analysis. Also, the branching or crosslinking exhibited significant improvement in tensile mechanical properties, which were studied, and the results are discussed. © 1998 John Wiley & Sons, Inc. J. Appl. Polym. Sci. 70: 797–803, 1998     

双噁唑啉类扩链剂增黏回收的PET的研究

从扩链剂用量、反应时间分别研究了2,2一双（2-噁唑啉）（BOZ）与2,2-（1,3-苯撑）-双（2-噁唑啉）（PBO）对回收的聚对苯二甲酸乙二醇酯（PET）的扩链效果。结果表明：扩链剂量为理论量的3倍,反应时间为4～6rain时获得最大扩链效果。其中BOZ对PET特性黏数的提高效果较好,从0．61提高到0．80。利用红外差减光谱分析了BOZ与PET的扩链反应前后的结构变化,酰胺基团出现以及酯基增加、羧基减少证实了扩链反应的发生;而五元环的存在则表明反应过程是分两步进行的。利用差示扫描量热分析仪分析了残余扩链剂对产物热性能的影响;当扩链剂的添加量较低时,熔融过程中产物的相对分子质量进一步提高,结晶度下降;而当扩链剂添加量较高时,相对分子质量反而下降,结晶度上升。     

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%。     

Recycling PET beverage bottles and improving properties

Recycling PET from bottles has been carried out by three different extrusion methods. Under optimized processing conditions, a virgin poly(ethylene terephthalate (PET), recycled PET and a mixture of virgin and recycled PET, with and without the modifier polypropylene functionalized with maleic anhydride [PP‐graft‐MA]), were processed. Different methods were used to characterize the processed products. The results showed that the intrinsic viscosity and molecular weight decreased as the blend ratio of recycled PET was increased. This was due to thermal exposure as well as shear degradation of recycled PET. Thermal cycles of the processes used for recycling PET and its blending specimens with virgin PET show the importance of the thermal treatment in the improvement of mechanical strength and increased crystallinity. Nevertheless, the properties of the functionalized blends were improved. This behaviour is attributed to a series of chemical and physico‐chemical interactions taking place between the two components. Copyright © 2004 Society of Chemical Industry     

Recycling of poly(ethylene terephthalate) into closed‐cell foams

The increase of the elongational viscosity of recycled poly(ethylene terephthalate) (PET) is investigated with the aim of producing closed‐cell foams by means of a cost‐effective reactive extrusion technique. A recycled PET grade containing controlled contamination levels of polyvinyl chloride (PVC) and poylethylene (PE) is selected, and compared with virgin bottle‐grade PET as a reference. Reactive processing with a tetrafunctional epoxy additive induces randomly branched molecules with a lower degree of branching in recycled PET than in virgin PET, as shown by a molecular structure analysis. The corresponding increase in elongational viscosity is related to foaming experiments performed using supercritical CO₂ in a pressurized vessel. Observations of foam microstructures reveal that modified virgin PET forms closed‐cell structures under a large variety of foaming conditions, as opposed to unmodified virgin and recycled PET, which collapse as a result of insufficient elongational resistance. Closed‐cell foams are also obtained using modified recycled PET, providing that the temperature at which the pressure is released is lowered to 260°. Recycling of PET into closed‐cell foams is thus achieved, although the processing window is slightly reduced compared to virgin PET.