Viscoelastic Windows of Pressure-Sensitive Adhesives

A viscoelastic window (VW) concept has been proposed to identify different types of pressure-sensitive adhesives (PSA's). Such viscoelastic windows are constructed from the values of dynamic storage modulus: G′ and dynamic loss modulus G″ at frequencies of 10^?2 and 10² rad/sec. These frequencies are chosen because the range covers most of the time scales corresponding to the uses of PSA's at different application rates in performance tests. A four quadrant concept has also been recommended to categorize different types of PSA's based on the location of their VW's on the log-log cross plot of G′ and G″. It was found that for most PSA's, the range of G′ and G″ at room temperature within these selected frequencies falls between 10³ and 10⁶ Pascals. The proposed four-quadrants (top-left hand quadrant of high G′ and low G″, top-right hand quadrant of high G′ and high G″, lower left hand quadrant of low G′ and low G″, and lower right-hand quadrant of low G′ and high G″) correspond respectively to (1) non-PSA or release coatings (2) high shear PSA's, (3) removable PSA's and medical PSA's and (4) quick and cold stick PSA's. It was also observed that the VW's of general purpose permanent PSA's occupy the central region which straddles part of the four quadrants.     

范德华力对Lennard-Jones体黏弹性的影响

采用平衡态分子模拟方法对ρ^*=0.85~1.0,T^*=0.6~1.5范围内共30组的液固共存态Lennard-Jones体的黏弹性进行研究。模拟所得真实物质Ar的约化黏度与实验值误差为6.69%,验证了本模型对真实物质的可拓展性;同时,液固共存态下Lennard-Jones体模型的黏度模拟值与文献值吻合较好,误差小于5.16%,模拟精度较高。从环境参数（T^*、ρ^*）和分子参数（L-J势参数ε、σ）两方面,观测了Lennard-Jones体的静态（黏度η^*、无限大频率的剪切模量G_∞^*）及动态（储能模量G'^*、损耗模量G"^*）黏弹性的变化规律,并在此基础上解释范德华力对黏弹性的影响机理。结果表明,ρ^*升高或T^*降低将导致η^*、G_∞^*的升高,而T^*、ρ^*的升高则会使得中高频区的G'^*及G"^*增大;L-J势参数ε、σ的增大均能促进体系固态化,增强其静态及动态黏弹性,可为工程上高效利用单原子物质的黏弹性提供理论指导。     

Photorheologically reversible micelle composed of polymerizable cationic surfactant and 4-phenylazo benzoic acid☆

A photorheologically reversible micelle composed of polymerizable cationic surfactant n-cetyl dimethylallyl ammonium chloride(CDAAC) and trans-4-phenylazo benzoic acid(trans-ACA) was prepared.The effects of molar ratio of CDAAC/trans-ACA,time of UV and visible light irradiation and temperature on the rheological properties of micellar system were investigated.The results show that before UV irradiation the system with an optimum CDAAC/trans-ACA molar ratio of 1.4 forms viscoelastic micelles at 45 °C.After 365 nm UV irradiation,the viscosities of micelle systems with different concentrations at fixed molar ratio of 1.4 are decreased by 85%–95%.The CDAAC/trans-ACA(14 mmol·L-1/10 mmol·L-1) micelle system exhibits shear thinning property and its viscosity is decreased obviously with the increases of UV irradiation time less than 1 h.The rheological process during UV irradiation for CDAAC/trans-ACA(14 mmol·L-1/10 mmol·L-1) micelle proves that viscosity,elastic modulus G′ and viscous modulus G″ will reduce quickly with the UV light.Furthermore,the micelle system after 1 h UVirradiation is able to revert to its initial high viscosity with 460 nm visible light irradiation for 4 h,and the micelle can be cycled between low and high viscosity states by repetitive UV and visible light irradiations.The UV–Vis spectra of CDAAC/trans-ACA micelle indicate that its photosensitive rheological properties are related closely to photoisomerization of trans-ACA to cis-ACA.     

聚碳酸亚丙酯/热塑性氧化淀粉的流变、形态和性能

采用熔融共混的方法制备了马来酸酐接枝聚碳酸亚丙酯(PPCMA)/热塑性淀粉(TPS)、PPCMA/热塑性氧化淀粉(TPOS)和PPCMA/ DL-TPOS(铝酸酯预处理的TPOS)复合材料,研究淀粉的氧化以及偶联剂的加入对PPC复合材料流变、形态和性能的影响。加入淀粉后的PPC复合材料拉伸强度有较大提高,红外光谱结果显示淀粉和PPCMA之间形成了氢键作用,这可能是力学性能提高的主要原因;热塑性氧化淀粉与PPCMA基材的界面相容性提高,PPCMA/TPOS复合材料的力学性能、储能模量、损耗模量和复数黏度均高于PPCMA/TPS复合材料;铝酸酯对TPOS的预处理促进了TPOS在PPCMA中的分散,提高了复合材料的拉伸强度,在PPCMA/DL-TPOS体系中,当DL-TPOS含量为40%(质量分数)时拉伸强度达到最大值,与PPCMA相比,提高了4.6倍。     

Preparation of ultra-high-strength nylon-6 fibre by a multi-step zone-annealing method

A multi-step procedure to improve the zone-annealing method was attempted to prepare a high-modulus and high-strength nylon-6 fibre. By the adoption of this procedure, the dynamic storage modulus at room temperature was markedly increased and reached 15.7 × 10¹⁰ dyne cm⁻² which is 1.5 times that obtained by the previous zone-annealing method. Tensile properties, orientation, crystallinity and mechanical dispersion were also measured. Comparing the multi-step procedure with the previous one-step procedure, the excellent effects of the multi-step procedure on mechanical properties are discussed. Further, in order to prevent selective relaxation of amorphous molecular chains on removing the applied tension after zone-annealing, heat-setting at constant length was subsequently carried out on the as-zone-annealed fibre. The mechanical properties were further improved: for example, the dynamic storage modulus at room temperature of the resulting fibre was raised to 16.9 × 10¹⁰ dyne cm⁻², which was well beyond the highest modulus available in the literature, 14 × 10¹⁰ dyne cm⁻².     

海洋平台泄漏硫化氢中毒事故后果动态评估

综合考虑受灾人员的应急疏散行为与泄漏气体积聚状态的时空变化，结合剂量响应模型提出海洋平台硫化氢泄漏中毒后果动态评估方法。应用所提出的方法对假想的海洋平台硫化氢泄漏事故后果进行评估，事故场景中考虑紧急关断系统（ESD）与放空系统对泄漏速率的影响，结合应急响应时序建立应急撤离时间模型。将基于动态评估方法得出的结果与基于静态评估方法、半动态评估方法得出的结果进行对比。基于静态评估方法、半动态评估方法与动态评估方法所得作业人员硫化氢吸入剂量分别为1.062×10⁵、7.230×10⁴和6.020×10⁴，对应的死亡率分别为5.396×10^-2、2.848×10^-3和4.571×10^-4。对比结果表明所提出的动态评估方法更细致地考虑了事故场景中的动态因素，能有效提高事故后果预测的准确度。。     

The elastic modulus of the poly(phosphonitrilic chloride) crystal

The Young's modulus for a crystal of poly(phosphonitrilic chloride) (poly-dichlorophosphazene) (NPCl₂)_n has been calculated using force constants derived from spectroscopy. Assuming that the molecule is a uniform helix the value of the modulus is 1.38 × 10⁹ dyne cm⁻² [dyne cm⁻² = 0.1 N m⁻²]; the result is 1.66 × 10¹⁰ dyne cm⁻² if a cis-planar structure is assumed for the molecule. Neither value is close to those obtained experimentally (1.8 × 10⁶ to 6.5 × 10⁶ dyne cm⁻²). This is because experimental values relate to the amorphous polymer whereas the calculated values are those for the crystal. There is good agreement between the values calculated for the (NPCl₂)_n crystal and those for other polymer crystals.     

Effect of X-ray or γ-ray irradiation on the dielectric properties of KNbO3 single crystals

The dielectric constant (K) and loss (tanδ) of KNbO₃ single crystals have been measured E II a-axis as a function of frequency from 10² to 10⁶ Hz and in the temperature range 30°-355°C. These measurements have also been taken after irradiating the crystals with X-rays or γ-rays. K at 30°C for these crystals decreases with frequency reaching a constant value of 725 beyond 10⁵Hz; tanδ, having moderately large values at low frequencies decreases with frequency. X-ray irradiation is found to decrease the frequency-dependent K value of KNbO₃ significantly but has practically no effect on its high frequency value. Dielectric loss (tansδ) values, particularly at low frequencies, decrease appreciably on X-ray irradiation of these crystals. X-ray Irradiation also reduces the peak K and tanδ values at 10₂ Hz at the curie temperature (225°C) but does not have effect on these parameters at 10⁶ Hz. γ-ray irradiation is found to bring about similar results; however the decrease in K and tanδ values are more pronounced with γ-ray Irradiation compared to X-ray Irradiation. An attempt is made to interpret these results.     

Conformation of isotactic polystyrene (IPS) in the bulk crystallized state as revealed by small-angle neutron scattering

Neutron scattering experiments have been performed on isotactic polystyrene (IPS) samples in the bulk crystallized state (T_{crystallization} = 185°C). The determination of the conformation of tagged chains ranging from 2.5 × 10⁵ to 7 × 10⁵ has been undertaken on two different hydrogenated IPS matrices. A matrix of usual molecular weight (M_w = 4 × 10⁵) leads to results which do not agree with Flory's model. In this case, measurements on radius of gyration R_g show on the one hand an important increase of this parameter (40%) with increasing crystallinity for the highest molecular weight tagged chains and on the other hand a variation with molecular weight like M^0.78. These results are interpreted with a schematic model involving a long crystalline sequence incorporated in the monocrystal along the 110 plane and two amorphous wings. Such an assumption is confirmed by the scattering behaviours in the intermediate range. On the other hand, by using an IPSH matrix of very high molecular weight (M_w = 1.75 × 10⁶), and the same tagged chains previously considered, a very weak variation of R_g with increasing crystallinity is observed. This leads to consider in this case Flory's conformation which is corroborated by data obtained in the intermediate range.     

火山灰微粒改性聚苯胺/环氧涂层的防腐蚀和耐热冲击性能

通过向聚苯胺/环氧涂层中添加适量的火山灰微米粒子（TMP）,有效提高了涂层的防腐性能,同时考察了TMP含量对涂层防腐性能的影响。实验结果表明添加TMP后的涂层在95℃、12% NaCl溶液中浸泡60 d后仍具有较高的低频阻抗值;其中,添加量为10%（质量分数）的涂层的阻抗值最高,为1.27×10⁹ Ω·cm²,说明该涂层仍具有较好的防腐性能。另外,该复合涂层的附着力有所改善,并具有优异的耐热冲击性能。     

Swollen-state polymerization of poly(ethylene terephthalate) in fibre form

The swollen-state polymerization of poly(ethylene terephthalate) in fibre form was performed in hydrogenated terphenyl as the swelling solvent. Ultra-high-molecular-weight poly(ethylene terephthalate) (CHMW-PET) fibre with an intrinsic viscosity of 3–4dl g⁻¹ (M_n = 2–3 × 10⁵) was obtained. The polymerization rate of as-spun PET fibres in the swollen state was greater than that of PET granules in the swollen state. It was clarified that the polymerization rate was related to the chain mobility of the starting materials. The chain mobility was influenced by various conditions, such as changing rigidity of the segments during copolymerization, the chain orientation of the starting fibre before swollen-state polymerization and the temperature of pretreatment with the solvent. Pretreatment with solvent before polymerization was effective in increasing the chain mobility. The relation between chain mobility and polymerization rate was examined by wide-angle X-ray diffraction, density, differential scanning calorimetry, solvent content and viscoelastic measurements. Undrawn UHMW-PET fibres could be drawn 10 times or more by the zone drawing technique in spite of their high crystallinity, and the drawn fibre showed high tensile strength (12 g d⁻¹) and high modulus (240 g d⁻¹).     

Viscoelastic properties of polyamic acid solutions—precursors of polyimides

The rheology of polyamic acid (PAA) solutions, precursors of polyimides used in microelectronic device applications, has been investigated by dynamic (oscillatory) shear flow measurements. Frequency dependent storage and loss moduli and dynamic viscosity were measured in the frequency range 10^?1 to 10³ rad/s at 23°C. The storage modulus G′ (ω) and loss modulus G″ (ω) exhibited quadratic and linear dependence in frequency at low frequencies respectively, the viscoelastic fluid behavior commonly predicted for polymer solutions from many molecular theories. At high frequencies both dynamic moduli become proportional to ω^2/3. The results show that PAA solutions are very high loss viscoelastic fluids, judging from the loss tangent values which far exceed unity. It is suggested that dynamic viscoelastic properties could be used to monitor the degree of imidization since there is a gradual change from viscoelastic fluids to soft viscoelastic solids to hard viscoelastic solids as PAA is converted to polyimides. Onset of non-Newtonian flow as shown on the frequency dependent dynamic viscosity was in the range 30 to 200 rad/s. The viscoelastic constants, zero-shear rate viscosity η_o and steady-state compliance J_e⁰, where also determined from the dynamic data and compared to previous steady shear flow results.     

Influence of gel and molecular weight on the properties of natural rubber

The influence of gel and molecular weight on the properties of natural rubber has been described. Crystallization, stress relaxation and orientation properties of different samples have been studied. Samples having different gel contents but similar molecular weights and samples having the same gel content with varying molecular weights have been prepared by extracting whole natural rubber. The gel content was varied from 1.5 to 29% and molecular weight from 1 × 10⁵ to 9.9 × 10⁵ g mol⁻¹. The gels reduce the overall crystallinity measured by differential scanning calorimetric experiments after freezing the samples for different time periods at −15°C. They also have a stiffening effect on the tensile relaxation modulus and decrease the rate of relaxation significantly. Birefringence, which measures the orientation and stress-induced crystallization, increases with time at high elongation for samples containing gels. At lower elongation, however, the birefringence of unvulcanized samples decreases with time. This decrease is less for gel samples. Natural rubbers of high molecular weight behave similarly in the above properties when compared to low molecular weight samples. The effect of gel is more predominant than that of molecular weight.     

Diamond growth by carbon ion implantation of diamond

Medium energy (5–25 keV) ¹³C⁺ ion implantation into diamond (100) to a fluence ranging from 10¹⁶ cm⁻² to 10¹⁸ cm⁻² was performed for the study of diamond growth via the approach of ion beam implantation. The samples were characterized with Rutherford backscattering/channelling spectroscopy, Raman spectroscopy, X-ray photoemission spectroscopy and Auger electron spectroscopy. Extended defects are formed in the cascade collision volume during bombardment at high temperatures. Carbon incorporation indeed induces a volume growth but the diamond (100) samples receiving a fluence of 4 × 10¹⁷ to 2 × 10¹⁸ at. cm⁻² (with a dose rate of 5 × 10¹⁵ at. cm⁻² s⁻¹ at 5 to 25 keV and 800 °C) showed no He-ion channelling. Common to these samples is that the top surface layer of a few nanometers has a substantial amount of graphite which can be removed by chemical etching. The rest of the grown layer is polycrystalline diamond with a very high density of extended defects.     

基于CAM模型的热再生沥青混合料动态粘弹特性研究

为研究再生剂对沥青混合料动态粘弹特性的影响,分别选用重石油基与生物油基两种再生剂制备再生沥青及沥青混合料,并分别在不同掺量下进行沥青三大指标试验以及沥青混合料动态模量试验,根据时温等效原理及改进的Christensen-Anderson-Marasteanu(CAM)模型分析了再生沥青混合料的动态粘弹特性。结果显示,随着再生剂掺量的增加,沥青混合料回收料(RAP)的沥青针入度、延度升高,软化点下降,再生剂的掺入显著提高了沥青的延展性,综合考虑经济与路用性能,以12%(质量分数)作为再生剂最佳掺量并进行混合料动态模量试验。两种再生剂均改变了RAP的感温性与粘弹特性,使再生沥青混合料动态模量降低而相位角升高;改进的CAM模型能够良好拟合再生沥青混合料的动态模量和相位角随频率的发展变化,拟合精度均在0.950以上。两种再生沥青混合料动态模量与相位角大小关系受加载频率影响,当加载频率高于10 Hz后,生物油基再生沥青混合料动态模量更低而相位角更高,当加载频率低于0.01 Hz时则相反,这对于同时提高沥青混合料高温稳定性及低温抗裂性是有利的。     

MUCT工艺处理生活污水短程脱氮的实现及硝化菌群动态变化

采用连续流MUCT工艺处理实际生活污水,研究短程生物脱氮的实现,并采用实时荧光定量PCR方法(quantitative real time PCR,QPCR)分析全程脱氮向短程脱氮转变过程中氨氧化细菌(ammonia-oxidizing bacteria,AOB)和亚硝酸盐氧化菌(nitrite-oxidizing bacteria,NOB)的动态变化。通过降低溶解氧浓度为0.5mg·L^-1和缩短水力停留时间为6h,实现短程硝化,亚硝酸盐积累率达到90%。在短程硝化稳定运行阶段总氮去除率高达90%以上,远远大于全程阶段的74%。QPCR结果表明全程脱氮阶段水力停留时间的缩短使AOB细胞数呈现下降的趋势,NOB细胞总数稳定维持在10⁸cells·(g dried sludge)^-1。短程脱氮阶段,AOB细胞数小幅度上升,由3.17×10⁶cells·(g dried sludge)^-1增长到1.32×10⁷cells·(g dried sludge)^-1,同时AOB占全菌的比例也小幅度增长。NOB的细胞数在5.9×10⁷~1.78×10⁸cells·(g dried sludge)^-1之间波动。NOB占全菌的比例由1.44%下降到0.47%。因此,MUCT工艺处理实际生活污水的系统中NOB丰度降低及活性抑制是实现并维持短程生物脱氮的重要原因。短程脱氮运行期间由于控制低溶解氧浓度和短的水力停留时间,AOB丰度及相对含量没有显著增加,甚至下降,但不会影响氨氮和总氮的去除。     

Effects of oxygen concentration on the electrical properties of ZnO films

In this paper, electrical characteristics by various oxygen content in ZnO films were studied. To control the oxygen content of ZnO films, post-thermal annealing was performed in N₂ and air ambient, led to improve crystallinity and optical properties of ZnO films. The oxygen concentration was measured by Auger electron spectroscopy. The ZnO films having the deficiency of oxygen showed the electron concentrations between 10²¹ and mid 6 × 10¹⁷ cm⁻³ and resistivity at 10⁻³–10⁻¹ Ω cm. On the other hand, when the oxygen concentration of the ZnO films was up to the stoichiometry with Zn, the ZnO films showed low electron concentration at −10¹⁷ cm⁻³ and resistivity at 10 Ω cm.     

高热流低流速条件下超临界CO2在小圆管内的对流传热特性

为获取高热流、低流速条件下超临界CO₂的传热规律，开展了超临界CO₂在内径2 mm水平小圆管内对流传热试验研究，并重点探讨了变物性、浮升力和热加速等效应对传热过程的影响。试验参数范围：系统压力7.6~8.4 MPa，质量流速400~500 kg/(m²?s)，热通量0~200 kW/m²，流体温度20~60℃，Reynolds数1.2×10⁴~4.3×10⁴。分别采用Gr/Re ²和Kv作为浮升力效应和热加速效应的判别因子。结果显示，在高热流低流速工况下，浮升力效应显著（Gr/Re ² > 10^-3），同一个截面处的上壁面传热系数始终小于下壁面传热系数。浮升力效应是高热流低流速工况下传热恶化的主要诱发因素。试验中热加速因子较小（Kv < 8.5×10^-7），其效应可以忽略。将试验数据与典型的传热经验关联式作对比，结果表明Liao-Zhao关联式的计算结果与试验结果最吻合。     

Estimation of the contribution of tube renewal in the terminal relaxation of linear polybutadiene

A set of low-molecular-weight (low-MW) entangled linear polybutadienes with molecular weights between 1.1 × 10⁴ and 2.5 × 10⁵ have been dilutedly embedded in a high-molecular-weight linear polybutadiene (M_w = 7.6 · 10⁵) matrix. The viscoelastic properties of these blends with 9.1% low-MW polymer have been measured. The loss moduli-frequency master curves, G^″ (Щ), contain contributions from both polymers. The contribution of the low-MW polymer is obtained by subtracting the contribution of the matrix. The maximum in G^″, G^″_m, due to the low-MW polymer occurs at a lower frequency (0.3 to 0.5 log units) than in the homopolymer. This result indicates that the longest relaxation time of the entangled linear polymer embedded in a high-molecular-weight matrix is increased by a factor of 2.0 to 3.0 because tube renewal normally operating in the homopolymer is almost completely absent in the matrix. The longest relaxation time of the polymers in the matrix depends on M^3.3₀. This is only slightly less than the dependence found in linear polymer melts (M^3.3₇). This indicates that reptation and chain-end fluctuation together contribute to the relaxation of linear polymers in permanent networks.     

Influence of incorporating CaCO3 into room temperature vulcanized silicone sealant on its mechanical and dynamic rheological properties

Silicone sealants with low modulus and high elongation were prepared by using ketoxime silane as chain extender agent, and a novel silane coupling agent acting as adhesion promoting agent was synthesized. Mechanical properties of vulcanized polydimethylsiloxane (PDMS) filled with large amounts of carbonate calcium (CaCO₃) and dynamic viscoelastic properties of unvulcanized samples were investigated through electronic multifunctional tensile tests, dynamic mechanical analyzers, and dynamic rheological measurements. The results of mechanical tests indicate that diminishing the particle diameter size, narrowing the particle diameter distribution, and increasing the filler amount lead to a relative high tensile strength and modulus at 100% elongation, but a relative low elongation at break. The reasons for these are believed to be the evolution of molecular interactions and the formation of additional physical crosslinking induced by the filler network. Compared to virgin PDMS, there is a significant elevation of glass transition temperature with filler addition. On the other hand, the results of dynamic rheological measurements reveal that as filler amount increases, the span of the linear viscoelastic region in which dynamic storage modulus (G′) is constant in low strain amplitude narrows. However, a characteristic plateau phenomenon appears in low frequency regions together with increasing the width and height of the modulus plateau. This phenomenon is also ascribed to the formation of a filler network due to filler–polymer and filler–filler interaction. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 2027–2035, 2007