Improvement of Structural and Thermal Stabilities of PVC and Wood/PVC Composite by Zn and Pb Stearates,and Zeolite

Three different chemical stabilizers were introduced into neat PVC and a wood/PVC composite (containing 50 phr wood flour) to improve their thermal and structural stabilities. The changes in CIE yellowness index, polyene index, %wt loss, and decomposition temperature (T_d) were monitored. The effects of type and content of thermal stabilizers, thermal ageing time, and the presence of wood flour were our main interests. The experimental results suggested that the additions of Zn and Pb stearates into PVC and wood/PVC composite could improve the thermal stability of the PVC. At the test temperature of 177°C, the additions of Zn and Pb stearates could improve the thermal stabilities of PVC by retarding the upzipped reaction and by reducing the conjugated double bonds in PVC, Pb stearate being the most suitable for thermally stabilizing the PVC. Around the T_d range (～264°C), the addition of Zn stearate reduced the T_d value of PVC whereas that of Pb stearate had no effect on the change in T_d value. Zeolite loading could shift the T_d value of the PVC from 264 to 280°C. The addition of wood particles increased the polyene content and decreased the decomposition temperature of the PVC. The effect of wood flour on the thermal and structural changes of PVC overruled that of thermal stabilizer loading.     

芯棒与口模反向旋转挤出聚乙烯管结构与性能的研究

采用自行研制的新型旋转挤出装置,通过芯棒与口模同时反向旋转挤出制备聚乙烯(PE)管.结果表明,在口模与芯棒反向旋转挤出过程中,管道内外壁除受到轴向应力作用外,还受到芯棒和口模旋转所施加的环向应力,其合力方向不再是沿管道轴向而是与其有一定的角度.因此,分子链的取向方向和以此链为初级成核点形成的串晶偏离轴向,增强了管道抵抗...     

Extrusion Cooking Effect on Carbohydrate Fraction in Novel Gluten-Free Flours Based on Chickpea and Rice

Extrusion cooking allows the development of value-added products from pulses, such as gluten-free snacks with added functional properties. The main objective of this study was to evaluate the changes induced by the extrusion process on the carbohydrate fraction (total carbohydrates, soluble sugars and oligosaccharides, dietary fiber, and arabinoxylans) of novel flour formulations based on chickpeas and rice enriched with different dietary fiber sources. Moreover, the influence of the addition of fiber-rich ingredients, such as Fibersol^® and passion fruit, on the analyzed compounds was also evaluated. Sucrose was the main soluble sugar found in analyzed formulations, and raffinose was the prevalent oligosaccharide, followed by stachyose. The content of total α-galactosides tended to be higher after extrusion cooking. As a consequence of the extrusion treatment, the content of total and soluble dietary fiber was statistically increased in most of the analyzed samples. In general, no significant changes were observed in total arabinoxylan content as a consequence of the extrusion process, while the content of water-soluble arabinoxylans was significantly increased in extruded formulations. It was observed that the content of total available carbohydrates, stachyose, and water-soluble arabinoxylans were significantly influenced by the addition of passion fruit, Fibersol^®, and both. The incorporation of these ingredients in gluten-free formulations based on chickpeas and rice allows one to obtain suitable functional formulations for the development of innovative, gluten-free, extruded snack-type products, which could be an interesting alternative for people with celiac disease.     

Effect of the Amount of Polysorbate 80 and Oregano Essential Oil on the Emulsion Stability and Characterization Properties of Sodium Alginate Microcapsules

Essential oils have a high volatility that leads to evaporation and loss of their pharmacological effect when exposed to the environment. The objectives of the present work were to prepare microcapsules with oregano essential oil by extrusion using sodium alginate as a shell material and non-ionic surfactant polysorbate 80 as an emulsifier to stabilize the emulsion. The present study was aimed to evaluate the physical parameters of microcapsules and to compare the influence of the amount of emulsifier and the essential oil-to-emulsifier ratio on the capsules’ physical parameters and encapsulation efficiency; to our knowledge, the existing research had not yet revealed whether unstable emulsion affects the encapsulation efficiency of oregano essential oil. This study showed that increasing the emulsifier amount in the formulation significantly influenced encapsulation efficiency and particle size. Moreover, increasing the emulsion stability positively influenced the encapsulation efficiency. The emulsion creaming index depended on the emulsifier amount in the formulation: the highest creaming index (%) was obtained with the highest amount of polysorbate 80. However, the essential oil-to-polysorbate 80 ratio and essential oil amount did not affect the hardness of the microcapsules (p > 0.05). In conclusion, the obtained results could be promising information for production of microcapsules. Despite the fact that microencapsulation of essential oils is a promising and extremely attractive application area for the pharmaceutical industry, further basic research needs to be carried out.     

Optical Probes for Monitoring Intercalation and Exfoliation in Melt‐Processed Polymer Nanocomposites

Summary: Laser‐induced fluorescence spectroscopy of the optical probe Nile Blue A in polymer clay nanocomposites is described. Concentration quenching of the fluorescence dominates the probe behavior until the clay platelets are physically separated by polymer intercalation. Further separation into an exfoliated structure results in an intense increase in probe fluorescence. Preliminary results indicate the ability to discriminate between intercalated and exfoliated structures in nanocomposites formed by melt processing.

Polyamide 6 nanocomposites: Purple, 1 minute processing (left). Red, 7 minute processing (right).     

苯乙烯/丁二烯聚合反应挤出多嵌段共聚物结构表征及共聚机理的研究

以双螺杆挤出机为反应器,采用丁二烯(B)与苯乙烯(S)混和单体,以有机锂为引发体系,本体一步合成了S B多嵌段共聚物.采用过氧化氢在四氧化锇作用下对聚合物分子链进行了深度氧化,然后通过精制除去氧化降解产生的低分子物.1H- NMR和FT IR分析表明共聚物中的双键全部被氧化断裂,而共聚物中聚苯乙烯的链节并未破坏.利用18角度小角激光光散射仪(MALLS)联用GPC对氧化降解后的聚苯乙烯碎片进行了分析,证明共聚物分子是由1条1×104～4×104分子量的聚苯乙烯链段连接着数十个(S- B)嵌段的结构.TEM分析表明调节反应过程的工艺条件可以控制共聚物的织态结构.     

Waxes for powder coatings

Since the first beginnings at the end of the 50^th, the powder coating technology has become a perfected alternative in product and procedure respect to liquid paints. Powder coatings are primarily a mixture of synthetic resins, pigments and additives offering economical and ecological advantages compared to other coating systems. The raw materials are mixed, extruded and ground to coating powders. Waxes play an important part as additives in powder coatings. Production, storage and processing as well as the properties of the applied powder coating can be influenced positively by different waxes. Various waxes and their advantages are demonstrated by practical advantages.     

凹坑表面活塞与缸套挤压润滑油的流固耦合数值模拟

在准油膜润滑条件下,采用Coupling Euler Lagrange(CEL)方法对凹坑表面活塞-缸套挤压润滑油过程进行了流固耦合数值模拟.润滑油动力学方程由Euler坐标系下的Navier-Stokes(N-S)方程来描述,活塞-缸套采用Lagrange坐标系下的线弹性力学方程来描述.罚函数约束方法将Lagrange结构的物理量传递给润滑油流体单元,实现流体和固体的直接耦合.仿真结果表明:CEL模型较好地追踪了挤压过程中润滑油的自由液面;凹坑表面裙部将润滑油挤压到贮油凹坑中,而光滑裙部只有挤压过程,无法贮存润滑油;随着润滑油的逐渐排出,接触应力逐渐增大,光滑裙部的接触应力增大尤为明显;凹坑中贮存的润滑油承载比稳定在0.3,该油膜具有一定的承载能力.数值模拟结果和试验数据的变化趋势吻合.     

THERMOCHROMIC EFFECTS OF LEUCO DYES STUDIED IN POLYPROPYLENE

A series of thermochromic polypropylene foils were prepared by embedding various leuco dye-developer-solvent systems in the polymer matrix. Bisphenol A, laurylgallate, ethylgallate and p-hydroxybenzoic acid methyl ester were used as developers, crystal violet lactone and 3,3-bis-（1-n-butyl-2-methyl-3-indolyl）-phthalide as dyes and l-octanoic acid methyl ester as solvent. The molar ratio between the three components of the investigated leuco dye-developer-solvent systems was kept constant. All obtained polypropylene foils exhibit an excellent thermochromic behavior. The foils, prepared by extrusion technology, switch from color to colorless with increasing temperature. The influence of molecular structure of the developer on the intensity of the colored state and the influence of a developer-surfactant complex on the resulting thermochromic properties were investigated. The results are presented and discussed in detail according to a molecular model suggesting that the ring-opening process of the leuco dye is triggered by the formation of dye-developer complexes via H-bondings.     

Multifunctionality for the nanojunction of a rotating p-phenylene vinylene molecule between graphene leads

With the multi-functional molecular device based on graphene nanoribbon being deeply studied in experiment, the zigzag-edged graphene device is still worth to investigate. Employing the ab-initio method, the spin transport properties have been studied for the nanojunctions consisting of a p-phenylene vinylene (PPV) molecule sandwiched between two-probe leads of zigzag-edged graphene nanoribbons (ZGNRs). A series of obvious electromagnetic transmission functionalities, including spin switching, negative differential resistance (NDR), dual spin-filtering, magnetoresistance and spin-diode behaviors, are numerically referred in the proposed molecular junction within spin parallel or antiparallel configurations. The performance of switching and double spin filtering can be explained by the transport spectra or total transmission pathways. Besides, the rectification effect is due to the asymmetry spatial distribution of the local density of states as well as the corresponding coupling between the PPV molecule and leads. It is expected that the designed models can be ideal candidate for future spintronic device.