Comparative study on phase and properties between rPET/PS and LCP/PS in situ microfibrillar-reinforced composites

Microfibrillar-reinforced composites based on two dispersed phases, liquid crystalline polymer (LCP) and recycled poly(ethylene terephthalate) (rPET), and polystyrene (PS) were prepared using extrusion process. The rheological behavior, morphology, and thermal stability of LCP/PS and rPET/PS blends containing various dispersed phase contents were investigated. All blends and LCP exhibited shear thinning behavior, whereas Newtonian fluid behavior was observed for rPET. The incorporation of both LCP and rPET into PS significantly improved the processability. The potential of rPET as a processing lubricant by bringing down the melt viscosity of the blend system was as good as LCP. The elongated LCP domains were clearly observed in as-extruded strand. Although the viscosity ratio of rPET/PS system was lower than that of LCP/PS system, most rPET domains appeared as small droplets. An addition of LCP and rPET into PS matrix improved the thermal resistance in air significantly. The obtained results suggested the high potential of rPET as a processing aid and thermally stable reinforcing-material similar to LCP. The mechanical properties of the LCP-containing blends were mostly higher than those of the corresponding rPET-containing blends when compared at the same blend composition.     

Morphology and mechanical performance of pregenerated and “in-situ” PP/vectra B composites

Polypropylene/Vectra B blends were obtained at different LCP contents and barrel temperatures by an extrusion-injection process. The wide barrel injection temperature range chosen, from 200 to 300°C, gave rise to blends in which the pregenerated extruded morphology was preserved, partially preserved, or lost. The blends processed at 260 and 300°C showed the usual morphology and properties of “in-situ” composites. The blends injected at 240°C showed the worst properties because of their partially melted and agglomerated morphology. A barrel temperature of 200°C (80°C below the melt temperature of Vectra B) was needed to maintain the pregenerated fibers. These pregenerated composites, without post-extrusion drawing, showed smaller modulus of elasticity and tensile strength than those of the “in-situ” composites, but an increased notched impact strength as a consequence of their less perfectly oriented but more homogeneous morphology.     

Effect of LCP and rPET as reinforcing materials on rheology,morphology, and thermal properties of in situ microfibrillar‐reinforced elastomer composites

Microfibrillar‐reinforced elastomer composites based on two dispersed phases, liquid crystalline polymer (LCP) and recycled poly(ethylene terephthalate)(rPET), and styrene‐(ethylene butylene)‐styrene (SEBS) were prepared using extrusion process. The rheological behavior, morphology, and thermal stability of SEBS/LCP and SEBS/rPET blends containing various dispersed phase contents were investigated. All blends and LCP exhibited shear thinning behavior, whereas Newtonian fluid behavior was observed for rPET. The incorporation of both LCP and rPET into SEBS significantly improved the processability by bringing down the melt viscosity of the blend system. The fibrillation of LCP dispersed phase was clearly observed in as‐extruded strand with addition of LCP up to 20–30 wt %. Although the viscosity ratio of SEBS/rPET system is very low (0.03), rPET domains mostly appeared as droplets in as‐extruded strand. The results obtained from thermogravimetric analysis suggested that an addition of LCP and rPET into the elastomer matrix improved the thermal resistance significantly in air but not in nitrogen. The simultaneous DSC profiles revealed that the thermal degradation of all polymers examined were endothermic and exothermic in nitrogen and in air, respectively. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Non-isothermal crystallization kinetic of recycled PET and its blends with PBT modified with epoxy-based multifunctional chain extender

A fundamental understanding of crystallization behavior is essential for the processing of both virgin and recycled polymers. This research delves into the crystallization characteristics and non-isothermal crystallization kinetics of recycled polyethylene terephthalate (rPET) and its blends with poly butylene terephthalate (PBT), which have been modified using epoxy-based multifunctional chain extenders (CE). The preparation of rPET/PBT blends involved a twin-screw extruder, with varying weight ratios and different CE concentrations. Differential scanning calorimetry was employed to perform crystallization analysis on the samples. The results underscore the profound impact of blend composition on the thermal characteristics of the system, with CE exerting only a marginal influence. The glass transition temperatures (T_g) of the two polymers were measured at 49 and 79°C. During blending, the T_g values demonstrated variations relative to the proportions but did not adhere to the Fox equation. Furthermore, PBT was found to enhance the crystallization tendencies of rPET, resulting in an increase in relative crystallinity from 11% to 36%. Notably, the crystallization rate of PBT at 0.40 min⁻¹ exceeded that of rPET at 0.36 min⁻¹. PBT minimally affected the crystallization rate constant of rPET-dominant blends, while rPET significantly reduced the crystallization rate in PBT-dominant blends.     

Toughening high density polyethylene submitted to extreme ambient temperatures

The use of polyethylene is limited due to its low impact strength among other mechanical properties at extreme ambient temperatures, for example at ?46 °C and 66 °C. In this work, different polymer components, such as ultra-high molecular weight polyethylene (UHMWPE) and ethylene-vinyl acetate (EVA), were incorporated in high density polyethylene (HDPE) to test their ability to improve toughness of HDPE at extreme ambient temperatures. The polymer blends were processed by extrusion and injection molding and characterized by rotational rheometry, electron microscopy, thermal analysis, tensile, impact and dynamic mechanical tests. The results showed that low concentrations of EVA and UHMWPE in HDPE increased substantially the impact strength of HDPE at room temperature as well as in extreme ambient temperatures (?46 °C and 66 °C). This result indicates that these HDPE blends can be considered good candidates to replace pure HDPE in applications in which high values of toughness are required at extreme ambient temperatures.     

Effect of dynamic cross‐linking on melt rheological properties of polypropylene/ethylene‐propylene‐diene rubber blends

Study of melts rheological properties of unvulcanized and dynamically vulcanized polypropylene (PP)/ethylene‐propylene‐diene rubber (EPDM) blends, at blending ratios 10–40 wt %, EPDM, are reported. Blends were prepared by melt mixing in an internal mixer at 190°C and rheological parameters have been evaluated at 220°C by single screw capillary rheometer. Vulcanization was performed with dimethylol phenolic resin. The effects of (i) blend composition; (ii) shear rate or shear stress on melt viscosity; (iii) shear sensitivity and flow characteristics at processing shear; (iv) melt elasticity of the extrudate; and (v) dynamic cross‐linking effect on the processing characteristics of the blends were studied. The melt viscosity increases with increasing EPDM concentration and decreased with increasing intensity of the shear mixing for all compositions. In comparison to the unvulcanized blends, dynamically vulcanized blends display highly pseudoplastic behavior provides unique processing characteristics that enable to perform well in both injection molding and extusion. The high viscosity at low shear rate provides the integrity of the extrudate during extrusion, and the low viscosity at high shear rate enables low injection pressure and less injection time. The low die‐swell characteristics of vulcanizate blends also give high precision for dimensional control during extrusion. The property differences for vulcanizate blends have also been explained in the light of differences in the morphology developed. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 1488–1505, 2000     

相容剂对rPET/mLLDPE共混物性能的影响

以回收聚对苯二甲酸乙二醇酯(rPET)为基体材料,茂金属线型低密度聚乙烯(mLLDPE)为共混材料,马来酸酐接枝线型低密度聚乙烯(LLDPE-g-MAH)、丙烯酸酯复合接枝苯乙烯-丁二烯弹性体为相容剂,制备了rPET/mLLDPE共混物。采用DSC和SEM分析了相容剂对共混物结晶性能及断面结构的影响,并检测了共混物的力学性能。结果表明:mLLDPE的加入使得rPET/mLLDPE共混物的熔体结晶峰向右移动,结晶温度提高了29.03℃;相容剂的加入使得共混物中rPET的玻璃化转变温度向低温方向移动,rPET与mLLDPE相容性增强;含3%LLDPE-g-MAH的rPET/mLLDPE共混物中,MAH基团与rPET中的羟基发生接枝反应,相界面模糊,rPET与mLLDPE界面黏结力增强,与纯rPET相比,其断裂伸长率提高了93.73%,缺口冲击强度提高了54.6%。     

Mechanical and thermal properties of polypropylene/recycled polyethylene terephthalate/chopped rice husk composites

The various ratios of recycled polyethylene terephthalate (rPET) into polypropylene (PP) filled with 40 parts chopped rice husk per hundred part of polymer have been studied. Composites were prepared using a corotating twin screw extruder at temperature zones of 165–215, well below 250°C (rPET mp temperature) and characterized by mechanical and thermal properties. To improve the compatibility between different components, PP grafted with maleic anhydride was added as a coupling agent in all the compositions studied. The results showed that the addition of rPET improved the tensile and flexural modulus and impact strength of the composite while reducing its tensile and flexural strength. The scanning electron microscopy micrographs of samples in the injection direction showed that some particle shaped rPET inside the composites appear as drawn fibrils and some appear as plates. Differential scanning calorimetric studies showed that the addition of rPET particles to the composites decrease the PP crystallization temperatures. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Effects of extrusion conditions on the properties of recycled poly(ethylene terephthalate)/nanoclay nanocomposites prepared by a twin‐screw extruder

The effects of extrusion conditions on the mechanical properties of recycled poly(ethylene terephthalate) (rPET)/clay nanocomposites were studied. Nanocomposites of recycled PET containing 2.5 and 5.0 wt % of montmorillonite modified with organophilic quaternary ammonium salt (DELLITE 67G) were prepared by melt compounding using a corotating twin‐screw type extruder at two different screw rotation speeds: 250 and 150 rpm. The highest value of Young's modulus was found for low screw rotation speed (150 rpm). Morphological analysis using transmission electron microscopy (TEM) revealed the presence of fully exfoliated clay platelets in samples prepared at 150 rpm. It was concluded that the screw rotation speed should be optimized when preparing recycled PET/clay nanocomposites by melt compounding. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

rPET/POE/LDPE-g-AA复合材料的制备及性能

以回收聚对苯二甲酸乙二酯( rPET)为基体材料,乙烯-辛烯共聚物(POE)为增韧材料,丙烯酸接枝低密度聚乙烯( LDPE-g-AA)为增容剂,制备了rPET/POE/LDPE-g-AA复合材料.分析了POE、LDPE-g-AA对rPET 玻璃化转变温度、断面相结构、结晶性能、力学性能的影响.结果表明,加入POE...     

Experimental investigation of the effects of a compatibilizing agent on the properties of a recycled poly(ethylene terephthalate)/polypropylene blend

This study deals with the behavior of a recycled polyethylene terephthalate (PET)/polypropylene (PP) blends. The compatibilizing effect has been investigated to examine the recycling feasibility in industrial production. The compatibilizing efficiency of olefinic copolymers containing epoxy groups for a/polypropylene (PET/PP) blends was examined using scanning electron microscopy (SEM), differential scanning calorimetry (DSC), mechanical testing and rheological one. The effect of ethylene-glycidyl methacrylate (E-GMA, 92/8 wt%, Lotader AX8840) and ethylene–methyl acrylate-glycidyl methacrylate (E-MA-GMA, 68/24/8 wt%, Lotader AX8900) copolymers was investigated. The blends of PET/PP/compatibilizer at compositions 80/15/5, 85/11.25/3.75, 90/7.5/2.5 and 95/3.75/1.25 (wt%) were prepared by melt mixing in a single-screw extruder. Test specimens were prepared by compression moulding at processing temperatures of 250 °C. The incorporation of the compatibilizers has a large effect on the dispersion of the PP phase. Moreover, the copolymer was more efficient than the terpolymer. Especially, E-GMA was found to improve the elongation at break of the blends containing 80 % PET.     

Studies on fiber formation of thermotropic copolyesters

Thermotropic copolyesters PET/60 PHB and PET/80 PHB fibers are melt spun at different extrusion temperatures and at different draw-down ratios. The flow behavior of PET/60 PHB is studied at different temperatures and shear rates. The melt of (PET/60 PHB) at temperatures above 265°C exhibit low viscosity and low activation energy of flow. The modulus and strength for both PET/60 PHB and PET/80 PHB fibers increase with the increase in extrusion temperature and draw-down ratio in the ranges studied. High birefringence, indicating the presence of mesophase is observed between 265 and 300°C on a hot stage polarizing microscope. X-ray diffraction patterns show that the molecular orientation increased with increasing draw-down ratio. Scanning electron microscopy of these fibers shows a well-developed highly oriented fibrillar structure. Superior mechanical performance of fibers spun at around 275°C are attributed to the presence of nematic mesophase in the polymer melt. © 1993 John Wiley & Sons, Inc.     

Effects of carbonate salts on crystallization kinetics and properties of recycled poly(ethylene terephthalate)

In this study, thermal and microscopic analyses were used to evaluate a variety of carbonate and bicarbonate salts (alkali, alkaline—earth, and other metals), having different thermal stability within the range of poly(ethylene terephthalate) (PET) processing temperatures, as nucleating agents for recycled bottle PET. In addition, the effects of the salts on the melt viscosity and MW of the resin after melt processing were investigated in attempts to determine their overall relative performance as potential nucleating agents during injection molding. It was found that among the additives tried sodium salts are the most effective nucleating agents for recycled PET crystallization with a concomitant relatively small reduction in molecular weight. All other salts were less effective nucleating agents and, in some cases, caused also significant resin degradation. Mechanisms explaining the behavior of the different salts are proposed. With regard to processability of recycled PET in injection molding, it was found that for certain additives temperatures below 100°C could be effectively used, resulting in short cycles that produced crystalline products with satisfactory mechanical properties. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 64: 1423–1435, 1997     

Study of compatibilization of HDPE–PET blends by adding grafted or statistical copolymers

The reactive compatibilization of blends of HDPE–PET [high‐density polyethylene–poly(ethylene terephthalate)] was investigated in this study. The compatibilizers used were two grafted copolymers prepared by reactive extrusion containing 1.20–2.30 wt % GMA such as HDPE‐g‐GMA and one statistical copolymer containing 1 wt % GMA such as Lotader AX8920. HDPE was successfully functionalized using a melt free‐radical grafting technique. Grafting was initiated in two ways: adding an initiator in the polymer–monomer mixture or activation by ozone of polymer. Ozonization of HDPE by the introduction of a peroxide lead to a better grafting yield and to better grafting efficiency of the samples. The effects of the three compatibilizers were evaluated by studying the morphology and the thermal and mechanical properties of HDPE–PET (70/30 wt %) blends. Significant improvements were observed, especially in morphology, elongation at break, and Charpy impact strength of the compatibilized blends. A more pronounced compatibilizing effect was obtained with the statistical copolymer, for which the elongation at break and the impact strength were increased by 100%, while the uncompatibilized blends showed a 60% decrease in the Young's modulus and the strength at break. We also were able to show that the grafting yield increase of 1.20–2.30 wt % of GMA did not affect the properties of the blends because the grafted copolymers possess very similar chemical structures. However, compatibilization of blends with grafted copolymers is an interesting method, particularly for recycled blends, because the synthesis of these compatibilizers is easy and cheap in comparison to statistical copolymer. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 2377–2386, 2001     

Mechanical and Thermal Properties of Poly(phthalazinone biphenyl ether sulfone)/PEEK Blends

A series of blends with various compositions are prepared by melt extrusion on the basis of novel copoly(phthalazinone biphenyl ether sulfone) (PPBES) and poly(ether ether ketone) (PEEK). The melt flowability, mechanical and thermal properties of the blends are studied. The results show that the incorporated PEEK has a large influence on the melt viscosity and thermal stability of blends. The tensile strength of the blends remains at about 90 MPa at room temperature; PPBES improves the mechanical properties of PEEK at 150°C. The flexural strength and modulus of the PPBES/PEEK blends also increase with the addition of PEEK.     

Cocontinuous morphologies in polystyrene/ethylene–vinyl acetate blends: The influence of the processing temperature

The influence of the compression‐molding temperature on the range of cocontinuity in polystyrene (PS)/ethylene–vinyl acetate (EVA) copolymer blends was studied. The blends presented a broad range of cocontinuity when compression‐molded at 160°C, and they became narrower when compression‐molded at higher temperatures. A coarsening effect was observed in PS/EVA (60:40 vol %) blends upon compression molding at higher temperature with an increase in the phase size of the cocontinuous structure. Concerning PS/EVA (40:60 vol %) blends, an increase in the mixing and molding temperatures resulted in a change from a cocontinuous morphology to a droplet–matrix morphology. This effect was observed by selective extraction experiments and scanning electron microscopy. The changes in the morphology with the molding conditions affected the storage modulus. An increase in the storage modulus in blends compression‐molded at 160°C was observed as a result of dual‐phase continuity. An EVA copolymer with a higher vinyl acetate content (28 wt %) and a higher melt‐flow index resulted in blends with a broader range of cocontinuity. This effect was more pronounced in blends with lower amounts of PS, that is, when EVA formed the matrix. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 386–398, 2003     

Structure and properties of injection moldings of polypropylene/polystyrene blends

A homoisotactic polypropylene (PP) was melt blended with 0–30 wt % of three kinds of polystyrene (PS) with melt flow indexes lower than, similar to, and higher than that of PP. The blends were injection molded at cylinder temperatures of 200–280°C, and the structure and properties of the injection moldings were studied. With PS blending, although the PP molding whitened, no surface defect such as layer peeling and pearl-like appearance occurred. The rigidity and dimensional accuracy of the molding improved without much deterioration in impact strength and heat resistance. At the same time the fluidity also improved. The injection moldings of PP/PS blends did not show clear skin/core structure under a polarizing microscope. The degrees of crystallinity and crystalline c-axis orientation decreased with PS blending. PS particles were the smallest when the ratio of the viscosity of the PS to that of PP at molding shear rate was slightly lower than unity. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 63: 1015–1027, 1997     

Structural characteristics,rheological properties,extrusion, and melt spinning of 60/40 poly(hydroxybenzoic acid-coethylene terephthalate) (PHB/PET)

The rheological properties, extrusion, and melt spinning characteristics, and concomitant morphological features of 60/40 PHB/PET aromatic copolyester have been investigated. The material flows at temperatures above 190°C, but all crystallites may not melt completely until about 250°C. The material exhibits a yield stress value in shear flow. In fact, yield stress values were measured over a range of temperature from 190 to 260°C and estimated at higher temperatures. Extrudate swell measurements were also made in the same range. Significant extrudate swell does not occur until the fluid is at a temperature where the yield stress is approximately 1/50th of its maximum value. Extrudates are fibrillar in character and exhibit significant levels of crystalline orientation. The level of crystalline orientation in melt spun fibers does not vary significantly with drawdown ratio, since it is apparently developed to near its limiting extent during its flow through the die. All of these responses are similar to those observed in melt flow/processing studies of thermotropic liquid crystalline hydroxypropylcellulose.     

Rheology and impact characteristics of compatibilized polypropylene-liquid crystalline polymer composites

Polypropylene-liquid crystalline polymer (PP/LCP) and maleic anhydride compatibilized PP/LCP blends were prepared using the extrusion technique followed by injection molding. The LCP employed was Vectra A950 which consists of 25 mol % of 2,6-hydroxynaphthoic acid and 75 mol % of p-hydroxybenzoic acid. The rheology, morphology, and impact behavior of compatibilized PP/LCP blends were investigated. The rheological measurements showed that the viscosity of LCP is significantly higher than that of the PP at 280°C. This implied that the viscosity ratio of the LCP to the polymer matrix is much larger than unity. Scanning electron microscopy (SEM) observations revealed that the LCP domains are dispersed mainly into elongated ellipsoids in the PP/LCP blends. However, fine fibrils with large aspect ratios were formed in the compatibilized PP/LCP blends containing LCP content ≥ 10 wt %. The development of fine fibrillar morphology in the compatibilized PP/LCP blends had a large influence on the mechanical properties. The Izod impact strength of the PP/LCP blends showed little dependence on the LCP concentrations. On the other hand, the impact strength of the compatibilized PP/LCP blends was dependent on the LCP concentrations. The correlation between the LCP fibrillar morphology and spherulitic structure with the impact properties of the compatibilized PP/LCP blends is discussed. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 67: 521–530, 1998     

Recycling of high density polyethylene/poly(vinyl chloride)/polystyrene ternary mixture with the aid of high energy radiation and compatibilizers

Ternary mixtures of waste plastics of high density polyethylene (HDPE), poly(vinyl chloride) (PVC), and polystyrene (PS) was recycled using a single‐screw extruder. Poly(ethylene‐co‐vinyl acetate) and poly(styrene‐b‐ethylene/butylenes‐b‐styrene) were introduced as compatibilizers for HDPE/PVC and HDPE/PS, respectively. After the polymer blends was prepared via extrusion, they were subjected to high energy irradiation. The morphology and the mechanical properties of the hybrid blends were examined. Scanning electron micrographs and transmission electron micrographs showed that both compatibilizers and irradiation improved the uniformity and dispersion of the system. The heterogeneous crosslinking generated by irradiation resulted in an optimum impact strength. High elongation at break was achieved by using compatibilizers. The improvement of tensile strength was moderate. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 12: 2756–2762, 2003