剪切变形对PPR断裂韧性的影响

采用等通道转角挤压(ECAE)方法,研究了剪切变形对无规共聚聚丙烯(PPR)结构和断裂韧性的影响。实验发现,在挤压温度为45℃时,进行ECAE加工有利于PPR球晶的取向形变和非晶区取向。断裂韧性实验表明:经过ECAE挤压后试样的裂纹扩展方向与球晶的取向方向一致;经45℃挤压后,试样产生单位新断裂表面所需的能量是未挤压试样的3.7倍,且该能量的98%是通过塑性变形来吸收的;断面形态表明由剪切变形产生的层状结构是其断裂扩展所需能量增加的原因。     

Studies on the radiation stability of ion exchange membranes

This article deals with some aspects of γ-radiation stability of (phenolsulfonic acid, PSA) cation exchange membranes synthesized in the laboratory. The changes in cation exchange capacity, moisture content, coion sorption, concentration potential, area resistance, counterion transference number, and solute flux of the membranes were evaluated before and after irradiation. The membrane samples were irradiated under wet conditions using a ⁶⁰Co source up to a total dose of 18.65 Mrads. The experimental data point out the possibility of degradation of PSA membranes beyond a dose of 9.78 Mrads, resulting in the loss of functional groups from membrane matrix.     

Effect of gamma radiation on polyNIMMO

PolyNIMMO is regarded as an energetic polymer. It consists of a nitrate ester group and an ether linkage, which are known to degrade naturally with time, a process which is increased drastically with heat and/or light. The general mechanism for heat ageing of polyesters is the homolytic scission of the CH₂O-NO₂ bond to produce CH₂O and NO₂ radicals. Often at low temperatures the NO₂ radicals can initiate autoxidation, reacting with oxygen resulting in chain scission of the polyether backbone. In this investigation polyNIMMO was subjected to gamma radiation which is a more aggressive form of radiation. Gamma irradiation of a polymer generally produces radicals, which in turn may produce more radicals through chain scission, chain transfer or quench radicals through recombination or crosslinking. Gamma radiation may also lead to internal plasticisation of the polymer. This is achieved by breaking the polymer backbone into smaller chain lengths, providing compatible, small molecules to plasticise the polymer. Thermal ageing of polyNIMMO tends to induce degradation, however, and surprisingly this was not observed in the bulk irradiation of polyNIMMO. Gamma radiation did not break down the polymeric chains into smaller lengths and therefore internal plasticisation did not occur.     

阻垢剂对悬浮液稳定性的影响

以油含量、固含量、界面张力及界面剪切黏度为指标,研究了阻垢剂羟基亚乙基二膦酸(HEDP)对胜利油田原油、模拟固体颗粒与模拟水所形成的悬浮液稳定性的影响。结果表明,HEDP浓度增加,悬浮液体系中固含量增加,油含量降低。当HEDP浓度为0~120 mg/L时,体系中固含量由136 mg/L增加至260 mg/L,而油含量由818 mg/L降至421 mg/L。HEDP浓度增加,油水界面张力降低,而界面剪切黏度增大,悬浮液体系稳定性增加。     

Colloidal stability of surfactant-free radiation curable polyurethane dispersions

Radiation-curable polyurethane dispersions (UV-PUDs) are colloidal dispersions whose stability is mainly ensured by the electrostatic repulsion between the negatively charged polymer particles. In this article, particle stabilization is presented in terms of the physico-chemical characteristics of the polymer dispersion and its microstructure. The phenomenon of the colloidal destabilization at higher temperature is studied by multiple light scattering, then correlated with the evolution of the particle size distributions and the measurement of the apparent critical coagulation concentration of a salt as an indication of the energy barrier at the surface of the particles. The investigation of selected chemical parameters of the polymer on the colloidal stability aims to identify the most relevant ones with an understanding of the underlying mechanism. The study underlines that UV-PUDs constitute a waterborne polymer family with its own identity, adding complexity to the traditional radiation curing chemistry. Finally, it highlights the new perspectives offered for novel environmental-friendly products with high-end performance and extended stability and robustness.     

Kinetic effects of silica nanoparticles on thermal and radiation stability of polyolefins

The effects of γ-irradiation as the accelerated degradation procedure were analyzed for the evaluation of material stability. Low density polyethylene, polypropylene and ethylene–propylene terpolymer were studied in formulations with SiO₂ nanoparticles (2 and 5 wt%) or as neat materials. High energy irradiation (up to 100 kGy) has revealed a faster increase in the absorption of carbonyl band in comparison with the corresponding change in hydroperoxide band. The three studied materials present increased oxidation rates as the received energy transferred from incidental rays is enhancing, because the thermal regime of degradation depends on the structural characteristics, namely initial number of tertiary carbon atoms and unsaturation level. The fate of hydroperoxides as oxidation initiators is discussed.     

Effect of electron-beam radiation on thermoplastic composites

Abstract

The effect of electron beam (EB) radiation on carbon fibre reinforced (CF) thermoplastic (PBT, PPS, PA) composites was investigated. To clarify whether crosslinking could take place without or only with the presence of a crosslinking agent, special attention was paid to the incorporation of this agent into polymer sheets with a carbon fibre content of 50% by volume. The thermal and mechanical properties of the materials before and after exposure under different irradiation doses were evaluated. For materials based on PBT, PPS and PA46, no significant changes in properties after irradiation could be observed. However, CF/PA66 exhibited some changes in the presence of a crosslinking agent after irradiation, which could be related to an irradiation-induced crosslinking reaction. The effect of irradiation on the flexural properties was insignificant but an improvement in the creep behaviour was observed. Non-reinforced PA66 plates were also manufactured and a gel content measurement indicated that crosslinking was successfully induced. Additional studies allowed the changes in the polymer due to this crosslink to be quantified.     

Effect of viscosity on liquid curtain stability

The effect of viscosity on liquid curtain stability was explored by high‐speed visualization. Measurements of the velocity within the curtain revealed the presence of a viscous boundary layer along the edge guides. The critical condition at the onset of curtain breakup was determined by identifying the flow rate below which the curtain broke for two different edge guide geometries: parallel and convergent. Curtain breakup was initiated by the expansion of a hole within the curtain. For low viscosity liquid, the measured hole retraction speed is independent of the viscosity and equal to the Taylor‐Culick speed. For high viscosity liquids, the retraction speed is lower than the Taylor‐Culick speed due to viscous forces that resist the flow. The results also show the effect of liquid viscosity on the curtain stability is a strong function of the edge guide design. © 2017 American Institute of Chemical Engineers AIChE J, 64: 1448–1457, 2018     

聚丙烯无纺布预辐射接枝改性及胺化研究

采用丙烯酸(AA)、二乙烯三胺(DETA)依次对聚丙烯(PP)无纺布进行预辐射接枝改性及胺化处理,研究了接枝反应及胺化反应的影响因素,并用红外光谱对产物进行表征。结果表明:随着AA用量的增加,接枝率呈先增长后下降趋势;随着反应温度的升高,反应时间的延长,接枝率增加;随着接枝率的增大,胺化反应温度的升高及反应时间的增加,胺化率增加。接枝反应温度为95℃,25 mL AA与无纺布反应2 h,接枝率可达到276%;接枝率为250%的无纺布与50 mL DETA反应7 h,胺化温度205℃,胺化率可达到73%。红外光谱分析表明,经辐射接枝及胺化处理后的PP无纺布有胺基基团。     

Effect of ultraviolet radiation on photodegradation of collagen

Photodegradation of solvent-cast collagen type I films and photostabilization of collagen by vitamin E were studied. These films were exposed to polychromatic radiation from a medium-pressure mercury lamp or monochromatic radiation from the Okazaki Large Spectrograph (OLS). Changes in the molecular structure of collagen were followed by UV-visible and FTIR spectroscopic measurements. Electron spin resonance (ESR) spectroscopic measurements were also carried out to identify the reaction intermediates of photodegradation. Photoreaction from phenylalanine, which is one of the main constituents of collagen to tyrosine and the scission of peptide linkage of collagen, were confirmed. Vitamin E was found to be an efficient photostabilizer for photodegradation of collagen. Action spectra of photodegradation and photostabilization of a collagen molecule were reported. A possible mechanism for the photodegradation of the collagen and photostabilization scheme based on these experimental results are presented. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 73: 1259–1265, 1999     

聚丙烯无纺布预辐射固相接枝丙烯酸的研究

以聚丙烯(PP)无纺布为基材,以丙烯酸为单体,进行预辐射固相接枝聚合,考察了外部环境、辐射剂量、温度、反应时间、单体用量、介质、阻聚剂、交联剂对接枝率的影响。结果表明,通过预辐射固相接枝聚合方法,可将丙烯酸单体接枝在PP无纺布上,辐射剂量增大可提高接枝率;反应时间对接枝率的影响在低、高温阶段有所不同。最佳反应条件为:氮气环境,辐射剂量大于50 kGy,反应温度65℃,反应时间3 h,单体浓度30%,反应介质为水,阻聚剂0.8 g,交联剂用量为5 mL。     

Effect of radiation treatment on silver azide sensitivity

A novel technique is proposed for studying the effect of radiation treatment on sensitivity of energetic materials, based on irradiation of specimens by a series of pulses on an electron accelerator. Data obtained in experiments with silver azide crystals are reported. The explosion probability in irradiated specimens is shown to be a nonmonotonic function of the radiation dose, exhibiting a rise for low doses and a fall for high doses. The experimental data obtained agree with the divacancy model for heavy metal azide initiation. __________ Translated from Fizika Goreniya i Vzryva, Vol. 42, No. 2, pp. 116–120, March–April, 2006.     

Effect of gamma radiation on low density polyethylene

Low density monofilaments of polyethylene with varying draw ratios were subjected to high energy radiation using Co⁶⁰ gamma radiation source. It was found that the tensile strength is sharply improved with the increasing dose up to 20 Mrd beyond which a sharp decrease in tenacity and initial modulus was observed. The swelling behaviour also decreased with the increased in dose of irradiation. However, density showed an increasing trend. The shrinkage behaviour of all the filaments was found to increase with increasing dose and draw ratios. The results have been explained in terms of continuous increase in crosslink density with the increasing dose of irradiation along with loss of crystallinity, which appears to be more severe in the latter stages of exposure. The samples exhibited memory effect after redrawing at 100°C and cooling under tension followed by further heating at 110°C under relaxed condition. The shrinkage was still much higher but independent of draw ratio.     

Battery performance of PMMA-grafted PE separators prepared by pre-irradiation grafting technique

Poly(methyl methacrylate)-grafted polyethylene (PE-g-PMMA) separators were prepared by pre-irradiation grafting technique of methyl methacrylate onto a commercial polyethylene separator. The prepared separators were characterized by using charge/discharge (C/D) cycling test, AC impedance, and thermal stability analyses. Thermal shrinkage (TS) of the PE-g-PMMA separators decreased with an increasing degree of grafting up to 70% above which it was saturated. The PE-g-PMMA separators showed a better oxidation stability on the anode up to 5 V and a better cycle life performance than the original PE separator. These characteristics make the prepared separators suitable for applications in high voltage secondary lithium batteries.     

Effect of gamma radiation and annealing on ultra-oriented polyethylene

Filaments of ultra-oriented high density polyethylene were solid-state extruded at an extrusion (draw) ratio of 26 and subsequently irradiated under vacuum by a cobalt-60 source at doses of 10,15, 20, 40 and 60 megarads (MRad). Several identically prepared but unirradiated strands were also tested. One set of samples at each dose was immersed in a silicone oil bath for one half hour at 128°C and one set was given no post-irradiation thermal treatment. Characterization of the resultant morphologies included differential scanning calorimetry (DSC), birefringence, thermomechanical analysis (TMA), and tensile testing. Results from DSC measurements indicate that initial radiation crosslinking only slightly disrupts the crystal lattice, but on subsequent melting and re crystallization, the chains are unable to recrystallize effectively in their former habit. In all cases, melting point and crystallinity decrease with increasing radiation dose. Birefringence and TMA results indicate that orientation is not disrupted by irradiation. For unannealed samples, Young's modulus increases slightly then levels off while tensile strength and elongation at break increase initially, then drop, For annealed irradiated samples, Young's modulus rises at first, then levels off at higher doses. Tensile strength and elongation at break increase significantly with increasing radiation treatment, then essentially reach constant values at highest doses.     

稀土对化学镀镍溶液稳定性的影响

研究了4种稀土元素(La、Y、Eu和Nd)对化学镀镍镀液稳定性、沉积速度以及镀层耐磨性的影响,并初步探讨了稀土元素在镀液中的作用机理。结果表明：4种稀土元素对镀液均有影响,其中Y的效果最明显,La的影响程度较小。适量的稀土均能增加镀液的稳定性,提高镀层的沉积速度和耐磨性。稀土元素Y的添加量在0,04g/L时,所得镀层的综合性能最好。