Direct evidence for chain orientation in poly(acetylene)

Two conflicting structural models (platelet and fibril) have been proposed in the literature for pristine cis-poly(acetylene). The respective models have separate, distinct implications for the chemical, physical and electrical properties of the material, in particular, the cis-trans isomerization, doping and conduction mechanisms. Luttinger-type cis-poly(acetylene) was prepared and studied in the transmission electron microscope (TEM) by low-dose conventional imaging, in dark-field mode and by electron diffraction. Thin ‘films’ of the material were shown to consist of fibrillar nets, having fibrils of diameter 5–25 nm. Combined electron diffraction and dark-field observations in the TEM indicated the structural arrangement within the fibrils as that having polymer molecular chains aligned parallel to fibril axes.     

The far infra-red spectrum of poly(vinyl chloride)

The far infra-red spectrum of a poly(vinyl chloride) sample prepared by the urea clathrate (UC) route has been measured at various temperatures in the range 60 to 320 K. The results, taken in conjunction with those for two less highly ordered polymers, indicate that a revision of the assignments of earlier workers, based on normal coordinate calculations and on the measured spectra of secondary alkyl chlorides such as 2-chlorobutane, is required. The band at 65 cm^?1 is attributed to a lattice mode and is not indicative of weak hydrogen bonds of the type CH…ClC. However, it is suggested that the band at 185 cm^?1, which is particularly clear and sharp with the UC polymer, probably originates from an interaction of this type, occurring specifically at tight chain folds.     

Diffusion of additives and plasticizers in poly(vinyl chloride): 4. A programmed temperature technique for the determination of the diffusion parameters of three dialkylphthalates

A programmed temperature technique has been developed for the measurement of the self-diffusion coefficients of additives in polymers. This has been applied to the diffusion of three dialkylphthalate plasticizers in poly(vinyl chloride). Values of the self-diffusion coefficients and the calculated activation energies obtained in this way have been compared with values previously obtained from measurements at constant temperature. It has been shown that the programmed temperature technique gives a very rapid method for the estimation of the activation energy of self-diffusion.     

Change of the amorphous state by heat treatment below the glass transition temperature

This study was undertaken to elucidate the state of a polymer in the amorphous state through a change of motion of the molecular chain caused by heat treatment below the glass transition temperature. From dielectric measurements of amorphous poly(ethylene terephthalate) heat-treated below T_g, it was found that the average relaxation time, the distribution of relaxation time and the dielectric strength increase with increase of heat treatment. From these results, it was concluded that the amorphous state becomes more random by heat treatment.     

Size and mechanical properties of craze zones at propagating crack tips in poly(methyl methacrylate) during fatigue loading

In specimens of high molecular weight poly(methyl methacrylate) the microregion at the crack tip has been investigated during fatigue crack propagation by applying the optical interference method in a specially constructed experimental set-up. Thus, in the frequency range of 0.4 to 50 Hz the size and contour of the craze zone were directly measured at upper and lower load of the cycles. In contrast to previous assumptions it is established that the maximum craze width at the crack tip and hence the maximum length of stretched fibrils increases strongly with crack propagation rate. The directly measured craze data and also the material parameters indirectly derived by the aid of the Dugdale model are related to those data which have been measured during continuous crack propagation under quasi-static tensile load. The spacings of the fatigue striations on the fracture surfaces are compared with the lengths of the craze zones.     

The determination of molecular orientation in uniaxially compressed PMMA by X-ray scattering

A procedure is presented for obtaining full molecular orientation information from wide angle X-ray scattering patterns of deformed non-crystalline polymers. The method is based on the analysis of experimental and calculated scattering patterns into their spherical harmonics. The results obtained for PMMA are compared with values predicted by the pseudo affine and affine deformation schemes.     

Antimicrobial activities of ZnO powder-coated PVC film to inactivate food pathogens

In this work, the effects of two different amounts of zinc oxide (ZnO) nanoparticles on the antimicrobial activities of poly (vinyl chloride)-based films to inactivate food pathogens were investigated. Results showed that the ZnO-coated film exhibited a good inhibition effect on the growth of Escherichia coli and Staphylococcus aureus and its ability was attributed to the ZnO nanoparticles. The ZnO-coated films exhibited more effective antibacterial activity for S. aureus . However, antifungal activity of the ZnO-coated films (20 mm × 25 mm) against Aspergillus flavus and Penicillium citrinum was not observed. It is likely due to the complexity of the fungal cell wall and the ZnO nanoparticles without UV light irradiated or the insufficient amount of nanoparticles. Our findings reveal that ZnO nanoparticles have a good potential to be coated on a plastic film to make antimicrobial packaging against bacteria such as E. coli and S. aureus .     

聚丙烯酸-g-非离子性聚氨酯在复鞣中的应用(续)

以丙烯酸(AA)与可聚合非离子性聚氨酯表面活性剂(PUA)为原料,通过自由基共聚制备了一种阴非离子性的多功能型树脂复鞣剂,采用FT-IR、DSC对其分子结构进行了表征,并将其应用于复鞣工序。研究结果表明:共聚物组成对该类接枝共聚物的实际复鞣效果影响显著。其中m(AA)∶m(PUA)为1∶1.5的共聚物Ⅳ,具有更好的填充增厚性和丰满性;而m(AA)∶m(PUA)为1∶19的共聚物Ⅱ则具有更好的助染性,成革的柔软度和粒面效果更佳。     

功能化碳纳米管复合薄膜及其膜卷纱的电热性能

碳纳米管(CNT)具有优异的电学性能,为了更好地将其应用于纺织品加热领域,采用加捻CNT薄膜的方法制备膜卷纱,并通过预喷涂导电聚合物聚(3,4-乙烯二氧噻吩):聚(苯乙烯磺酸盐) (PEDOT:PSS)溶液的方式进一步优化CNT膜卷纱的电热性能;随后分析PEDOT:PSS喷涂浓度对CNT薄膜及其膜卷纱的结构和导电性能的影响,以及施加不同电压条件下CNT薄膜及其膜卷纱的温度变化。结果表明:随着PEDOT:PSS质量分数从0.01%增加至1.4%,所喷涂的CNT薄膜电导率由344.2 S/cm逐渐增大至668.9 S/cm;当PEDOT:PSS质量分数为0.07%时,所制备的CNT复合膜卷纱具有优异的电热性能,当在其两端施加电压时,温度可到达214 ℃,响应时间为5 s,发热温度是其未加捻薄膜的1.6倍,具有较好的应用潜力和开发价值。