Effects of nano‐ and micro‐fillers and processing parameters on injection‐molded microcellular composites

The effects of submicron core‐shell rubber (CSR) particles, nanoclay fillers, and molding parameters on the mechanical properties and cell structure of injection‐molded microcellular polyamide‐6 (PA6) composites were studied. The experimental results of PA6 nanocomposites with 5.0 and 7.5 wt% nanoclay loadings and of CSR‐modified PA6 composites with 0.5 and 3.1 wt% CSR loadings were compared to their neat resin counterparts. This study found that nanoclay was more efficient in promoting a smaller cell size, larger cell density, and higher tensile strength for microcellular injection molding parts. A higher nanoclay loading led to more brittle behavior for microcellular parts. It was found that a proper amount of CSR particles could be added to the microcellular injection‐molded PA6 to reduce the cell size, increase the cell density, and enhance the toughness of the molded part. However, CSR particles were less effective cell nucleation agents as compared to nanoclay for producing desirable cell structures, and a higher CSR loading was found to have diminishing effects on the process and on the properties of the parts. POLYM. ENG. SCI., 45:773–788, 2005. © 2005 Society of Plastics Engineers     

Mechanical properties study of micro‐ and nano‐hydroxyapatite reinforced ultrahigh molecular weight polyethylene composites

This is a comparative study between ultrahigh molecular weight polyethylene (UHMWPE) reinforced with micro‐ and nano‐hydroxyapatite (HA) under different filler content. The micro‐ and nano‐HA/UHMWPE composites were prepared by hot‐pressing method, and then compression strength, ball indentation hardness, creep resistance, friction, and wear properties were investigated. To explore mechanisms of these properties, differential scanning calorimetry, infrared spectrum, wettability, and scanning electron microscopy with energy dispersive spectrometry analysis were carried out on the samples. The results demonstrated that UHMWPE reinforced with micro‐ and nano‐HA would improve the ball indentation hardness, compression strength, creep resistance, wettability, and wear behavior. The mechanical properties for both micro‐ and nano‐HA/UHMWPE composites were comparable with pure UHMWPE. The mechanical properties of nano‐HA/UHMWPE composites are better compared with micro‐HA/UHMWPE composites and pure UHMWPE. The optimum filler quantity of micro‐ and nano‐HA/UHMWPE composites is found to be at 15 wt % and 10 wt %, separately. The micro‐ and nano‐HA/UHMWPE composites exhibit a low friction coefficient and good wear resistance at this content. The worn surface of HA/UHMWPE composites shows the wear mechanisms changed from furrow and scratch to surface rupture and delamination when the weight percent of micro‐ and nano‐HA exceed 15 wt % and 10 wt %. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 42869.     

Fracture behavior of PVC/Blendex/nano‐CaCO3 composites

PVC/Blendex/Nano‐CaCO₃ composites were prepared by melt‐blending method. The Blendex (BLENDEX® 338) (GE Specialty Chemicals Co., Ltd., Shanghai, China) was an acrylonitrile‐butadiene‐styrene copolymer with high butadiene content. The fracture behavior of PVC/Blendex/nano‐CaCO₃ composites was studied using a modified essential work of fracture model, U/A = u₀ + u_dl, where u₀ is the limiting specific fracture energy and u_d is the dissipative energy density. The u₀ of PVC/Blendex blend could be greatly increased by the addition of nano‐CaCO₃, while the u_d was decreased. Nano‐CaCO₃ with particle size of 38 nm increased the u₀ of PVC/Blendex blend more effectively than that with particle size of 64 nm, when nano‐CaCO₃ content was below 10 phr. Both the u₀ and u_d of PVC/Blendex/nano‐CaCO₃ composites were not much affected by increasing specimen thickness from 3 mm to 5 mm, while the two fracture parameters were increased with increasing loading rate from 2 mm/min to 10 mm/min, and u_d was found to be more sensitive to the loading rate than u₀. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 95: 953–961, 2005     

Evaluation of PVC compound on the Brabender torque rheometer

Increasing the rotor speed during the equilibrium portion of a Brabender torque rheometer test makes the test more sensitive to small changes in critical additives. The improved sensitivity of the instrument can assist processors in selecting the level of an additive for optimum performance and efficiency; in troubleshooting a processing or property problem; and in evaluating the performance of additives, for example, in the laboratory, before production trials.     

Rheological characterization of ABS,PC, and their blends through the interpretation of torque rheometer data

The blends of acrylonitrile-butadiene-styrene (ABS) and polycarbonate (PC) prepared on a Haake Torque Rheometer System 9000 were studied in order to investigate the effect of ABS addition on the flow properties of PC. The recorded data obtained from the rheometer were converted, into values of shear rate, shear stress, and viscosity, following the method suggested by Laguna. The viscosity of the blends was found to decrease with the shear rate according to the concept of pseudoplasticity. An improvement in the PC processability through the ABS addition was confirmed. Along with the possibility of yielding rheological parameters, this method seems to be an efficient way to enlarge the application of this instrument in the polymer industry.     

转矩流变仪在测定PVC树脂塑化性能方面的应用

介绍了运用附带数据处理机的流变仪PL2000-6分析通用PVC树脂的流变行为,通过“相关程序”研究了国内外同牌号PVC树脂的熔融曲线,发现国产PVC树脂和进口产品在塑化性能方面存在着一定的差距。     

转矩流变仪在PVC管材生产中的应用

本文从转矩流变仪的构成、实验原理以及PVC干混料的动态热稳定性曲线的分析入手,重点介绍了转矩流变仪在PVC管材生产中的应用,并对辅料配方工艺等方面的调整给出了建议。     

转矩流变仪法测定PVC材料的热稳定时间

分析了转矩流变仪法测量PVC材料热稳定时间的标准化和技术现状.指出了转矩流变仪法测量PVC材料热稳定时间的标准化及理论研究存在的不足,提出了在采用转矩流变仪法测量PVC材料热稳定时间过程中如何合理确定热稳定时间的起点和终点,以准确获得试验结果.     

Fusion characteristics of rigid PVC/wood‐flour composites by torque rheometry

This study was aimed at examining the effects of wood flour contents, wood species (softwood vs. hardwood), and particle size on the fusion characteristics (fusion time, fusion temperature, fusion torque, and fusion energy) of rigid PVC/wood‐flour composites in a torque rheometer. Neat rigid PVC exhibited one fusion peak, whereas the addition of wood flour into the PVC matrix led to two fusion peaks. Increased wood flour content caused a significant increase in the time, temperature, and energy at which fusion between the primary particles started, thereby leading to increased fusion torque, irrespective of the wood flour species. These results implied that rigid PVC filled with wood flour must be processed at higher temperatures than neat resin. Although fusion characteristics of the composites were influenced by the wood species, a clear trend between softwood and hardwood species could not be established. However, finer particles fused more quickly and needed less energy than coarse ones. J. VINYL ADDIT. TECHNOL., 13:7–13, 2007. © 2007 Society of Plastics Engineers.     

Relationship between torque and capillary rheometer thermal stability measurements for PVC compounds

A method is described to predict the time-temperature behavior and hence thermal stability of PVC melts in a Brabender Plasticorder torque rheometer from basic rheological data(flow and thermal stability observations) obtained on an Instron capillary rheormeter. The predicted and experimentally determined values of the Brabender thermal stability are shown to be in good agreement.     

转矩流变仪系列实验设备在PVC加工中的应用

介绍了混合器流变仪在测试PVC干混料的流变性能、动态热稳定性能的实验及PVC增塑剂热吸收实验中的应用,单、双螺杆挤出机流变仪在测试物料挤出性能实验中的应用。实验结果表明：用流变仪测试的结果是相对的,需要与“标准物料”进行对照,以优化配方,改善产品质量。     

Processing and properties of polymeric nano‐composites

Polymeric nano‐composites are prepared by melt intercalation in this study. Nano‐clay is mixed with either a polymer or a polymer blend by twin‐screw extrusion. The clay‐spacing in the composites is measured by X‐ray diffraction (XRD). The morphology of the composites and its development during the extrusion process are observed by scanning electron microscopy (SEM). Melt viscosity and mechanical properties of the composites and the blends are also measured. It is found that the clay spacing in the composites is influenced greatly by the type of polymer used. The addition of the nano‐clay can greatly increase the viscosity of the polymer when there is a strong interaction between the polymer and the nano‐clay. It can also change the morphology and morphology development of nylon 6/PP blends. The mechanical test shows that the presence of 5–10 wt.% nano‐clay largely increases the elastic modulus of the composites and blends, while significantly decreases the impact strength. The water absorption of nylon 6 is decreased with the presence of nano‐clay. The effect of nano‐clay on polymers and polymer blends is also compared with Kaolin clay under the same experimental conditions.     

A novel method of hyperbranched poly(amide‐ester) modifying nano‐SiO2 and study of mechanical properties of PVC/nano‐SiO2 composites

A new method of surface chemical modification of nano‐SiO₂ was proposed in the paper. In the presence of catalyst, the active hydroxyl groups on the surface of nano‐SiO₂ reacted with AB₂‐type monomer (N,N‐dihydroxyethyl‐3‐amino methyl propionate) by one‐step polycondensation. And the product's Fourier transform infrared graphs and transmission electron microscopy (TEM) images proved that hyperbranched poly(amine‐ester) (HPAE) was grafted from nano‐SiO₂ surface successfully. Moreover, polyvinyl chloride (PVC)/modified nano‐SiO₂ composites were made by melt‐blending. The composites' structures and mechanical properties were characterized by TEM, scanning electron microscopy, and electronic universal testing machine. The results showed that nano‐SiO₂ grafted by HPAE increased obviously in dispersion in PVC matrix, and mechanical properties of PVC were effectively improved. Additionally, it was found that mechanical properties of PVC/nano‐SiO₂ composites reached the best when weight percent of nano‐SiO₂ in PVC matrix was 1%. Compared with crude PVC, the tensile strength of HPAE grafted nano‐SiO₂/PVC composite increased by 24.68% and its break elongation, flexural strength, and impact strength increased by 15.73, 4.07, and 184.84%, respectively. POLYM. COMPOS., 2008. © 2008 Society of Plastics Engineers     

Plasticization of nano‐CaCO3 in polystyrene/nano‐CaCO3 composites

The shear rheological properties of polystyrene (PS)/nano‐CaCO₃ composites were studied to determine the plasticization of nano‐CaCO₃ to PS. The composites were prepared by melt extrusion. A poly(styrene–butadiene–styrene) triblock copolymer (SBS), a poly(styrene–isoprene–styrene) triblock copolymer (SIS), SBS‐grafted maleic anhydride (SBS–MAH), and SIS‐grafted maleic anhydride were used as modifiers or compatibilizers. Because of the weak interaction between CaCO₃ and the PS matrix, the composites with 1 and 3 phr CaCO₃ loadings exhibited apparently higher melt shear rates under the same shear stress with respect to the matrix polymer. The storage moduli for the composites increased with low CaCO₃ concentrations. The results showed that CaCO₃ had some effects on the compatibility of PS/SBS (or SBS–MAH)/CaCO₃ composites, in which SBS could effectively retard the movement of PS chain segments. The improvement of compatibility, due to the chemical interaction between CaCO₃ and the grafted maleic anhydride, had obvious effects on the rheological behavior of the composites, the melt shear rate of the composites decreased greatly, and the results showed that nano‐CaCO₃ could plasticize the PS matrix to some extent. Rheological methods provided an indirect but useful characterization of the composite structure. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci, 2006     

Rheological behaviors of glass bead‐ and wollastonite‐filled polypropylene composites modified with thermoplastic elastomers

Steady‐ and oscillatory‐shear rheological behaviors of polypropylene/glass bead (PP/GB) and PP/wollastonite (PP/W) melts modified with thermoplastic elastomers, poly(styrene‐b‐ethylene‐co‐butylene‐b‐styrene) copolymer (SEBS) and the corresponding block copolymer grafted with maleic anhydride (SEBS‐g‐MA), were examined by means of a parallel‐plate rheometer. With adding the elastomers (SEBS and SEBS‐g‐MA) and fillers (spherical GB and acicular W) to PP, viscosity especially at low shear rates and shear‐thinning flow behavior at high shear rates were pronounced as evidenced quantitatively by Carreau–Yasuda (CY) parameters, but Cox–Merz analogy became weakened. Besides, melt‐elasticity in terminal region and relaxation time (t_c) in crossing point increased, indicating an enhancement in quasi‐solid behavior of molten PP. Comparing with the elastomers, rheological behaviors of molten PP were more influenced with adding the rigid fillers, especially with W due to distinct acicular shape of W particles. SEBS‐g‐MA elastomer more affected rheological behaviors of the ternary composites than SEBS elastomer, implying that SEBS elastomer and the filler particles behaved individually (i.e., development of separate microstructure) in (PP/GB)/SEBS and (PP/W)/SEBS ternary composites, but core‐shell microstructure developed with strong interfacial adhesion by adding SEBS‐g‐MA elastomer, and the filler particles encapsulated with the thick SEBS‐g‐MA elastomer interlayer (i.e., core‐shell particles) acted like neither big elastomer particles nor like individual rigid particles in melt‐state. Moreover, effects of SEBS‐g‐MA elastomer reached a maximum on rheological behaviors of (PP/W)/SEBS‐g‐MA ternary composite, indicating a synergy between core‐shell microstructure and acicular W particles. Correlations between oscillatory‐shear flow properties and microstructures of the blends and composites were evaluated using Cole–Cole (CC), Han–Chuang (HC), and van Gurp–Palmen (vGP) plots. COMPOS., 2012. © 2012 Society of Plastics     

Minimum pickup velocity: The transition between nano‐scale and micro‐scale

The transport of nano‐scale particles has become increasingly important, but the knowledge base available is limited. This study aims to bridge the knowledge gap between the nano‐ and micro‐scales for pneumatic conveying. A key parameter is the minimum pickup velocity (U_pu), which is the minimum fluid velocity required to initiate motion in a particle originally at rest. The U_pu values of nine alumina particles with particle diameters (d_p) ranging from 5 to 110,000 nm were determined using the weight loss method, then compared against the established pickup Zones (analogous to the Geldart Groups). Results indicated that: (1) U_pu varied non‐monotonically with increasing d_p, thus revealing the missing link between the nano‐ and micro‐scales; (2) the intermediate particle diameters surprisingly did not agree with any pickup Zone; (3) Zone III (analogous to Geldart Group C) is inadequate for all the nano‐scale particles, so new boundaries and a new Zone are proposed. © 2016 American Institute of Chemical Engineers AIChE J, 63: 1512–1519, 2017     

转矩流变仪在PVC型材生产与质量管理中的应用

介绍了转矩流变仪与双螺杆挤出机工作原理,分析了二者的对应关系,提出了理想的PVC物料标准流变曲线概念,阐述了转矩流变曲线在PVC型材生产与质量管理中的应用方法。     

Investigation of the addition of nano‐CaCo3 at dry mixing or onset of fusion on the dispersion,torque, and mechanical properties of compounded PVC

A Brabender torque rheometer equipped with an internal mixer was used to study the influence of compounding method on the properties of (rigid PVC)/(treated and untreated nano‐CaCO₃) nanocomposites. Two different methods were studied for the addition of surface treated and untreated nano‐CaCO₃ during the melt mixing of rigid PVC. Direct dry mixing of rigid PVC and nano‐CaCO₃, and addition of nano‐CaCO₃ at the onset of PVC fusion were investigated. Dispersion of treated and untreated nano‐CaCO₃ was studied by X‐ray diffraction and scanning electron microscopy. Results showed that using direct dry mixing improved the dispersion of nano‐CaCO₃ in the PVC matrix by lowering the fusion time. The mechanical properties of the nanocomposite samples such as impact strength, tensile strength, and elongation at break were improved by using this method. The addition of treated nano‐CaCO₃ at the onset of fusion caused a simultaneous decrease in torque. Also, rigid PVC nanocomposites prepared with treated nano‐CaCO₃ showed better mechanical properties than those of nanocomposites prepared with the untreated nano‐CaCO₃. J. VINYL ADDIT. TECHNOL., 18:153–160, 2012. © 2012 Society of Plastics Engineers     

Zein‐based micro‐ and nano‐particles for drug and nutrient delivery: A review

Zein is the major storage protein from corn with strong hydrophobicity and unique solubility and has been considered as a versatile food biopolymer. Due to the special tertiary structures, zein can self‐assemble to form micro‐ and nano‐particles through liquid–liquid dispersion or solvent evaporation approaches. Zein‐based delivery systems have been particularly investigated for hydrophobic drugs and nutrients. Recently, increasing attention has been drawn to fabricate zein‐based advanced drug delivery systems for various applications. In this review, the molecular models of zein tertiary structure and possible mechanisms involved in zein self‐assembly micro‐ and nano‐particles are briefly introduced. Then, a state‐of‐the‐art introduction and discussion are given in terms of preparation, characterization, and application of zein‐based particles as delivery systems in the fields of food science, pharmaceutics, and biomedicine. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40696.