Effect of screw rotation speed on the properties of polystyrene/organoclay nanocomposites prepared by a twin‐screw extruder

We discuss the effect of screw rotation speed on the mechanical and rheological properties and clay dispersion state of polystyrene (PS)/organoclay (clay) nanocomposites prepared by melt compounding with a counterrotating‐type twin‐screw extruder. Poly(styrene‐co‐vinyloxazolin) (OPS) was used as an additional material. The Young's modulus of the PS/OPS/clay nanocomposites showed the maximum value at a screw rotation speed of 70 rpm in this study. This implied the existence of an optimized screw rotation speed for the melt compounding of the polymer/clay nanocomposites. For PS/clay systems without the addition of OPS, the peak intensity from clay increased and the distance between clay platelets in the nanocomposites decreased with the screw rotation speed. On the other hand, inverse results were obtained for PS/OPS/clay systems. According to the transmission electron microscopy photographs, the PS/OPS/clay nanocomposite at 70 and 100 rpm had fully exfoliated clay platelets. The dynamic rheological properties of the PS/clay nanocomposites were almost the same as those of neat PS. On the other hand, the storage and loss moduli of the PS/OPS/clay nanocomposites at the same frequency were larger than those of the PS/clay system. On the whole, the bonding between clay platelets and PS was important for increasing the viscosity and elasticity in the melts of the PS/clay system. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 1165–1173, 2006     

Synthesis and properties of poly(ethylene terephthalate)/clay nanocomposites by in situ polymerization

Poly(ethylene terephthalate) (PET)/clay nanocomposites (PCNs) with N‐methyl diethanol amine (MDEA)‐based organoclays are synthesized by using in situ polymerization. Four kinds of MDEA‐based materials are prepared and used as organifiers of pristine montmorillonite. The clay treated with the organifiers has a d‐spacing range that is about 14–21 Å. The PCNs with these organoclays are characterized by using wide‐angle X‐ray diffraction, scanning and transmission electron microscopy, atomic force microscopy, capillary rheometry, and tensile and barrier testing. The PCNs form an intercalated and delaminated structure. The well‐stacked nanoclays are broken down into small pieces in the PET matrix and the thickness of the clay bundle decreases to 20 nm. The melt viscosity and tensile strength of these PCNs increases with only 0.5 wt % clay. In oxygen barrier testing, the PCN with 1 wt % well‐dispersed organoclay shows a twofold higher barrier property than pure PET. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 1262–1271, 2007     

Low temperature solid‐state extrusion of recycled poly(ethylene terephthalate) bottle scraps

The processing of poly(ethylene terephthalate) (PET) involves thermal and hydrolytic degradation of the polymer chain, which reduces not only the intrinsic viscosity and molecular weight, but also the mechanical properties of recycled materials. A novel PET/bisphenol A polycarbonate/styrene–ethylene–butylene–styrene alloy based on recycled PET scraps is prepared by low temperature solid‐state extrusion. Hydrolysis and thermal degradation of PET can be greatly reduced by low temperature solid‐state extrusion because the extrusion temperature is between the glass‐transition temperature and cold‐crystallization temperature of PET. Modification of recycled PET by low temperature solid‐state extrusion is an interesting method; it not only provides an easy method to recycle PET scraps by blend processing, but it can also form novel structures such as orientation, crystallization, and networks in the alloy. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 2692–2699, 2006     

Thermal and mechanical properties of poly(ethylene terephthalate)/lamellar zirconium phosphate nanocomposites

The preparation of nanocomposites of poly (ethylene terephthalate) (PET) and lamellar zirconium phosphorous compounds by melt extrusion was investigated. Two types of zirconium phosphorous compounds were synthesized by the direct precipitation reaction method: α‐zirconium bis(monohydrogen orthophosphate) monohydrate (ZrP) and organic–inorganic hybrid layered zirconium phenylphosphonate (ZrPP). Composites containing 2 and 5 wt % ZrP and ZrPP were prepared in a twin‐screw extruder and specimens were obtained by injection molding. The extent of dispersion of the layered filler in the composite matrix was investigated by X‐ray diffraction and transmission electron microscopy (TEM). The crystallization and thermal properties were analyzed by differential scanning calorimetry and thermogravimetry, and the mechanical properties were evaluated by tensile tests. Whereas ZrP‐containing composites showe characteristic diffraction peaks at 2θ 11.7° (d = 7.54 Å), indicative of no delamination, ZrPP showed practically no low‐angle diffraction peak at 2θ 5.5° (d = 15.24 Å), indicating loss of the layered order. TEM images of ZrPP particles indicated the formation of an intercalated/partially delaminated nanocomposite. The behavior was attributed to the higher affinity of the polyester with phenyl groups on the platelet surface of ZrPP. In both cases, the addition of the fillers increased the crystallization rate and the modulus. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 3868–3876, 2006     

Synthesis and characterization of poly(ethylene terephthalate)/attapulgite nanocomposites

A kind of clay with fibrous morphology, attapulgite (AT), was used to prepare poly (ethylene terephthalate) (PET)/AT nanocomposites via in situ polymerization. Attapulgite was modified with Hexadecyltriphenylphosphonium bromide and silane coupling agent (3‐glycidoxypropltrimethoxysilane) to increase the dispersion of clay particles in polymer matrix and the interaction between clay particles and polymer matrix. FTIR and TGA test of the organic‐AT particles investigated the thermal stability and the loading quantity of organic reagents. XRD patterns and SEM micrographs showed that the organic modification was processed on the surface of rod‐like crystals and did not shift the crystal structure of silicate. For PET/AT nanocomposites, it was revealed in TEM that the fibrous clay can be well dispersed in polymer matrix with the rod‐like crystals in the range of nanometer scale. The diameter of rod‐like crystal is about 20 nm and the length is near to 500 nm. The addition of the clay particles can enhance the thermal stability and crystallization rate of PET. With the addition of AT in PET matrix, the flexural modulus of those composites was also increased markedly. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 1279–1286, 2007     

Preparation and properties of poly(ethylene terephthalate)/ATO nanocomposites

Antimony doped tin oxide (ATO) nanoparticles modified poly(ethylene terephthalate) (PET) composites used for manufacturing antistatic PET fiber were synthesized by in situ polymerization. The crystallization and multiple melting behavior of the nanocomposites were systemically investigated by means of Differential Scanning Calorimeter (DSC), Fourier Transform Infrared (FTIR), X‐ray Diffraction (XRD) techniques. The degree of crystallinity in nanocomposites increased with increasing ATO content. Smaller and more incomplete crystals are presented in the crystalline regions of the nanocomposites with increasing the content of ATO, which could be attributed to heterogeneous nucleation effects of ATO nanoparticles. Dynamic Mechanical Analysis (DMA) measurements showed that the storage moduli of the nanocomposites increased with increasing the content of ATO, due to formation of immobilized layer between polymer and filler. The interactions between ATO and PET molecules result in high tan δ for the PET/ATO nanocomposites. Percolation threshold of PET/ATO hybrid fibers prepared by the nanocomposites at room temperature was as low as 1.05 wt %, much lower than that of the composites filled with conventional conductive particles. Adding ATO nanoparticles obviously improves the conductivity of PET. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

玻璃纤维增强回收聚对苯二甲酸乙二醇酯复合材料的力学性能

用熔融共混制备了玻璃纤维（GF）增强的回收聚对苯二甲酸乙二醇酯（rPET）复合材料,研究了复合材料的力学性能并进一步利用Halpin-Tsai模型、Krenchel-COX模型和Kelly-Tyson模型探讨了GF的近程和远程结构与复合材料性能间的关系。结果表明,GF对rPET具有较为显著的增强、增韧效果。当玻璃纤维含量为30 %(质量分数,下同)时,复合材料的冲击强度、拉伸强度以及弯曲强度分别提高了245 %、113 %以及84 %;长径比和取向度是影响GF改性rPET复合材料性能的重要结构参数;Halpin-Tsai方程能够较好地描述rPET/GF复合材料中GF的有效长径比;而相比于Krenchel-COX方程,由Kelly-Tyson方程获得的GF的取向度更接近实验结果。     

Preparation and crystallization of poly(ethylene terephthalate)/SiO2 nanocomposites by in‐situ polymerization

Poly(ethylene terephthalate) (PET)/SiO₂ nanocomposites were prepared by in situ polymerization. The dispersion and crystallization behaviors of PET/SiO₂ nanocomposites were characterized by means of transmission electron microscope (TEM), differential scanning calorimeter (DSC), and polarizing light microscope (PLM). TEM measurements show that SiO₂ nanoparticles were well dispersed in the PET matrix at a size of 10–20 nm. The results of DSC and PLM, such as melt‐crystalline temperature, half‐time of crystallization and crystallization kinetic constant, suggest that SiO₂ nanoparticles exhibited strong nucleating effects. It was found that SiO₂ nanoparticles could effectively promote the nucleation and crystallization of PET, which may be due to reducing the specific surface free energy for nuclei formation during crystallization and consequently increase the crystallization rate. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 655–662, 2006     

The effects of metallic derivatives released from montmorillonite on the thermal stability of poly(ethylene terephthalate)/montmorillonite nanocomposites

By in situ polycondensation, poly(ethylene terephthalate) (PET)/montmorillonite (MMT) nanocomposites was prepared, which were characterized via X‐ray diffraction and transmission electron microscope. The processing stability of these nanocomposites was investigated by the change of number–average molecular weight and carboxyl terminal group content during injection molding, and the thermal stability of the nanocomposites was investigated via thermogravimetric analysis. It was found that some metallic derivatives released from MMT during polycondensation had a great influence on the processing and thermal stabilities of the nanocomposites. The quantity of these metallic derivatives was determined by inductively coupled plasma. The stabilization effect of phosphorous compounds generated from MMT modified with phosphonium was observed. Processing stability and thermal stability of these nanocomposites exhibited similar trend because of almost the same causes. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 1692–1699, 2006     

Morphology and properties of polymer/organoclay nanocomposites based on poly(ethylene terephthalate) and sulfopolyester blends

Poly(ethylene terephthalate) (PET) nanocomposite films containing two different organoclays, Cloisite 30B^® (C30B) and Nanomer I.28E^® (N28E), were prepared by melt blending. In order to increase the gallery spacing of the clay particles, a sulfopolyester (PET ionomer or PETi) was added to the nanocomposites via a master‐batch approach. The morphological, thermal and gas barrier characteristics of the nanocomposite films were studied using several characterization techniques such as scanning electron microscopy, transmission electron microscopy, X‐ray diffraction, differential scanning calorimetry, dynamic mechanical analysis, rheometry and oxygen permeability. PET and PETi were found to form immiscible polymer blends and the nanoparticles were preferentially located in the PETi dispersed phase. A better dispersion of clay was obtained for nanocomposites containing N28E with PETi. On the contrary, for nanocomposites containing C30B and PETi, the number of tactoids increased and the clay distribution and dispersion became worse than for C30B alone. Overall, the best properties were obtained for the PET/C30B nanocomposite without PETi. Higher crystallinity was found for all nanocomposite films in comparison to that of neat PET. © 2012 Society of Chemical Industry     

Toughening of recycled poly(ethylene terephthalate) with clay‐compatibilized rubber phase

Recycled bottle‐grade PET (rPET) is a valuable low‐cost polymeric material. However, enhancement of its mechanical properties is necessary for many applications. This work is focused on clay‐reinforced/compatibilized rPET/elastomer system. Although the clay addition to various rPET/elastomer blends caused a remarkable refinement of structure, more pronounced for clay with less polar modification, both a gain or decrease in strength and toughness occurred, whereas an increase in modulus was found for all systems. This is a consequence of simultaneous complex affecting many parameters by clay and both antagonistic and synergistic combination of respective effects. Best results were found for low contents of EPR rubber and its preblending with clay. The presented results indicate that a suitable combination of nanosilicates with rubber can lead to rPET materials with fairly enhanced properties. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Effects of the recycled poly(ethylene terephthalate) fibers on the rigid polyurethane foam

Recycled poly(ethylene terephthalate) (PET), subjected to the treatment with the flame retardant first, was used to reinforce the rigid polyurethane foams (RPUFs). Different loadings of PET fibers (3–12 wt %) of different lengths (5, 10, 15, and 20 mm) were added into RPUF. The mechanical properties of composites were studied by compressive strength test and shear stress test. The flame-retardant properties were evaluated by cone calorimeter and limited oxygen index test. The results showed that the proper addition of PET fibers could improve the mechanical and flame-retardant properties of the material. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47758.     

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。     

Synthesis and characterisation of copolyesters from poly(ethylene terephthalate) and poly(hexamethylene terephthalate)

Copolyesters containing poly(ethylene terephthalate) and poly(hexamethylene terephthalate) (PHT) were prepared by a melt condensation reaction. The copolymers were characterised by infrared spectroscopy and intrinsic viscosity measurements. The density of the copolyesters decreased with increasing percentage of PHT segments in the backbone. Glass transition temperatures (T_g). melting points (T_m) and crystallisation temperatures (T_c) were determined by differential scanning calorimetry. An increase in the percentage of PHT resulted in decrease in T_g, T_m and T_c. The as-prepared copolyesters were crystalline in nature and no exotherm indicative of cold crystallisation was observed. The relative thermal stability of the polymers was evaluated by dynamic thermogravimetry in a nitrogen atmosphere. An increase in percentage of PHT resulted in a decrease in initial decomposition temperature. The rate of crystallisation of the copolymers was studied by small angle light scattering. An increase in percentage of PHT resulted in an increase in the rate of crystallisation.     

Phase structure and properties of poly(ethylene terephthalate)/high‐density polyethylene based on recycled materials

Blends based on recycled high density polyethylene (R‐HDPE) and recycled poly(ethylene terephthalate) (R‐PET) were made through reactive extrusion. The effects of maleated polyethylene (PE‐g‐MA), triblock copolymer of styrene and ethylene/butylene (SEBS), and 4,4′‐methylenedi(phenyl isocyanate) (MDI) on blend properties were studied. The 2% PE‐g‐MA improved the compatibility of R‐HDPE and R‐PET in all blends toughened by SEBS. For the R‐HDPE/R‐PET (70/30 w/w) blend toughened by SEBS, the dispersed PET domain size was significantly reduced with use of 2% PE‐g‐MA, and the impact strength of the resultant blend doubled. For blends with R‐PET matrix, all strengths were improved by adding MDI through extending the PET molecular chains. The crystalline behaviors of R‐HDPE and R‐PET in one‐phase rich systems influenced each other. The addition of PE‐g‐MA and SEBS consistently reduced the crystalline level (χ_c) of either the R‐PET or the R‐HDPE phase and lowered the crystallization peak temperature (T_c) of R‐PET. Further addition of MDI did not influence R‐HDPE crystallization behavior but lowered the χ_c of R‐PET in R‐PET rich blends. The thermal stability of R‐HDPE/R‐PET 70/30 and 50/50 (w/w) blends were improved by chain‐extension when 0.5% MDI was added. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Sequence analysis of poly(ethylene terephthalate)/poly(butylene terephthalate) copolymer prepared by ester-interchange reactions

The molecular structure of the copolyester formed through the interchange reaction in poly(ethylene terephthalate)/poly(butylene terephthalate) blends was investigated with ¹³C-NMR spectroscopy. The molar fractions of heterolinkage triads in the copolyesters were lower than the values calculated by Bernoullian statistics; this indicates that the sequence of heterolinkages was far from a random distribution at the initial stage of the interchange reaction. However, the randomness increased and the number-average sequence length decreased with reaction time. The solubility of the blend decreased with increasing sequence length, resulting from the formation of block copolymers with long sequence lengths at the initial stage of the interchange reaction. The solubility of the copolyester formed by a dibutyltin dilaurate (DBTDL)-catalyzed reaction was higher than that of the copolyester formed by a titanium tetrabutoxide-catalyzed reaction; this is related to the fact that alcoholysis prevailed in the DBTDL-catalyzed reaction. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 159–168, 2001     

Supercritical carbon dioxide (scCO2) dispersion of poly(ethylene terephthalate)/clay nanocomposites: Structural,mechanical, thermal,and barrier properties

Dispersed poly(ethylene terephthalate) (PET)/clay nanocomposites can lead to materials with superior barrier and mechanical properties. PET/clay nanocomposites were prepared by melting extrusion of PET with as‐received or supercritical carbon dioxide (scCO₂) predispersed Cloisite^® 30B (30B). The predispersion of 30B was assessed by WAXD, SEM, and TGA, and results indicated that scCO₂ processing could predisperse 30B and the surface modification of the clay was preserved after processing. The structure of PET/30B nanocomposites was investigated by WAXD and TEM confirming that PET has penetrated into the clays inter‐galleries and the predispersed clays lead to improved interfacial interaction and homogenous clay dispersion. Both tensile strength and Young's modulus were improved by 12.1% and 24.9% respectively, as incorporating of 3 wt % of scCO₂ processed clay. Differential scanning calorimetry (DSC) results indicated that clay particles served as nucleation agent could increase the crystallinity whereas had no impact on melting process. In addition, with the addition of 1 wt % of predispersed clay, a significant reduction of oxygen permeation (～33%) was achieved at 23 °C and the maximum reduction (44%) was achieved by adding 3 wt % processed clay. Moreover, we confirmed the effect of temperature on the permeation of PET/30B nanocomposites depended both on the Arrhenius behavior of the organic phases and tortuous path effects, where improved clay dispersion resulted in a higher effective activation energy. Moreover, the transparency of PET matrix was preserved for all nanocomposites. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44779.     

Microstructure and crystallization of melt‐mixed poly(ethylene terephthalate)/poly(ethylene isophthalate) blends

Physical blends of poly(ethylene terephthalate) (PET) and poly(ethylene isophthalate) (PEI), abbreviated PET/PEI (80/20) blends, and of PET and a random poly(ethylene terephthalate‐co‐isophthalate) copolymer containing 40% ethylene isophthalate (PET₆₀I₄₀), abbreviated PET/PET₆₀I₄₀ (50/50) blends, were melt‐mixed at 270°C for different reactive blending times to give a series of copolymers containing 20 mol % of ethylene isophthalic units with different degrees of randomness. ¹³C‐NMR spectroscopy precisely determined the microstructure of the blends. The thermal and mechanical properties of the blends were evaluated by DSC and tensile assays, and the obtained results were compared with those obtained for PET and a statistically random PETI copolymer with the same composition. The microstructure of the blends gradually changed from a physical blend into a block copolymer, and finally into a random copolymer with the advance of transreaction time. The melting temperature and enthalpy of the blends decreased with the progress of melt‐mixing. Isothermal crystallization studies carried out on molten samples revealed the same trend for the crystallization rate. The effect of reaction time on crystallizability was more pronounced in the case of the PET/PET₆₀I₄₀ (50/50) blends. The Young's modulus of the melt‐mixed blends was comparable to that of PET, whereas the maximum tensile stress decreased with respect to that of PET. All blend samples showed a noticeable brittleness. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 3076–3086, 2003     

PEN/PET共混物结晶行为研究

用差示扫描量热法(DSC)研究了不同共混比例PEN/PET共混物的熔体结晶行为,并进行了等温结晶动力学测定。结果表明:随着两种组分向中间比例(50/50)靠近,共混物的熔融温度越低,结晶速率也越慢。     

Spinning and properties of poly(ethylene terephthalate)/organomontmorillonite nanocomposite fibers

By in situ polycondensation, a intercalated poly(ethylene terephthalate)/organomontmorillonite nanocomposite was prepared after montmorillonite (MMT) had been treated with a water‐soluble polymer. This nanocomposite was produced to fibers through melt spinning. The resulting nanocomposite fibers were characterized by X‐ray diffraction (XRD), differential scanning calorimeter (DSC), and transmission electron microscopy (TEM). The interlayer distance of MMT dispersed in the nanocomposite fibers was further enlarged because of strong shear stress during processing of melt spinning. This was confirmed by XRD test and TEM images. DSC test results showed that incorporation of MMT accelerated the crystallization of poly(ethylene terephthalate) (PET), but the crystallinity of the drawn fibers just had a little increasing compared with that of neat PET drawn fibers. Also compared with pure PET drawn fibers, tensile strength at 5% elongation and thermal stability of the nanocomposite fibers were improved. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 95: 1443–1447, 2005