聚丙烯腈原丝的结构表征

叙述了聚丙烯腈(PAN)原丝的大分子构型、超分子结构和形态结构;研究了PAN的组成、立体规整性、结晶结构、取向结构、横截面和表面形态、皮芯结构、孔隙及缺陷等对性能的影响规律;认为优化原丝工艺、提高原丝质量是制备高性能碳纤维的关键。     

聚丙烯腈(PAN)基碳微球的制备

本文以MMA(甲基丙烯酸甲酯)和AN(丙烯腈)单体为原料,通过种子乳液聚合法先制备了PMMA/PAN微球。然后在其表面包覆一层交联的PMMA层,得到了170 nm左右的PMMA/PAN/交联PMMA三层复合微球。再以三层复合微球作为前驱体进行热处理,最终得到比表面积达1379.3 m~2/g的50~70 nm尺寸的PAN基碳微球。     

Changes in physical properties of methacrylonitrile (MAN)-grafted silk fibers

Changes in physical properties of silk fibers, grafted with methacrylonitrile (MAN), were investigated as a function of the weight gain. The weight gain increased steadily during the first 60 min of reaction and gradually attained an equilibrium value (60%) after about 4 h. The initial tensile resistance of silk fibers decreased by MAN grafting. The crystalline structure of silk fibers remained unchanged, regardless of MAN grafting, however. a minor and broad peak appeared in the X-ray diffraction curves of MAN-grafted silk fibers with a weight gain of 60%, corresponding to the unoriented MAN polymer attached inside the fibers. Molecular orientation of silk fibroin chains in the crystalline regions, evaluated from X-ray diffraction curves, did not change significantly, while both birefringence and isotropic refractive index decreased as the weight gain increased, implying that MAN polymer attached preferentially to the amorphous and not to the crystalline regions. Dynamic vis-coelastic measurements showed that the position at which the E′ value began to decrease shifted to a lower temperature as the weight gain increased. These findings suggest that the thermal movement of silk fibroin molecules was accelerated by the presence of the poly-MAN chains attached to the amorphous regions of silk fibroin fibers. © 1993 John Wiley & Sons, Inc.     

Preparation,morphology and properties of natural rubber composites filled with untreated short jute fibres

Green composites were obtained by incorporation of short jute fibres in natural rubber matrix using a laboratory two-roll mill. The influence of untreated fibre content (1, 2.5, 5, 7.5 and 10 phr) on the mechanical properties, dynamic mechanical properties, swelling properties was examined. The behaviour of prepared green composites under cyclic compression was also investigated. Fibre dispersion in rubber matrix was studied by scanning electron microscopy. The highest tensile strength (21.1 MPa) and highest tear strength (39.9 N/mm) were found for composites containing 2.5 and 5 phr of short jute fibres, respectively. The results also suggested that increasing fibrous filler content resulted in increasing of tensile moduli 100, 200 and 300 % of elongation and hardness, and decreasing of rebound resilience and abrasion resistance of prepared jute/natural rubber composites. The cyclic compression test showed that increasing the amount of short jute fibres in the rubber matrix is related to increase of the energy dissipated in the composite. The incorporation of short jute fibres into the rubber matrix improves the stiffness of the composites, and it is related to the interaction between fibre surface and rubber matrix. The application of short fibres in higher amounts leads to formation of fibre agglomerates reducing the mobility of the rubber polymer chains. The mentioned agglomerates act as defects in rubber matrix, which caused decreasing of some properties, e.g. relative elongation at break.     

Structure and physical properties of grafted jute fiber

Jute fiber was grafted by acrylonitrile and methylmethacrylate monomers in raw and bleached condition. It was also noted that optimum grafting takes place after about 4 h of grafting. It was also noted that in bleached jute fiber, the grafting percentage is higher at all stages of grafting but the tenacity value at the highest add-on is practically the same as that of raw fiber with much less add-on. The crystalline orientation of the grafted jute fiber was correlated with the fiber tenacity. The moisture regain (%) of the fiber after grafting showed a decreasing trend with an increase in grafting percentage. No structural change of the fiber occurred due to grafting. © 1995 John Wiley & Sons, Inc.     

臭氧预氧化聚丙烯腈纤维工艺条件的研究

通过在线监测聚丙烯腈纤维的热收缩行为,对臭氧预氧化工艺条件进行了研究。实验结果表明:超过150℃通入臭氧会引起纤维分子链断裂,对预氧化不利;低温下恒温,臭氧预氧化效果不明显;恒温温度过高,加快了臭氧的分解,臭氧预氧化的效果也不明显,因此最佳的恒温温度应为125℃。同时对恒温时间进行了优化,发现当恒温时间达到1h,臭氧会引起晶区PAN纤维分子链的断裂,对预氧化不利,因此最佳恒温时间应为0.5h。     

添加氧化锌晶须的聚丙烯腈纤维抗静电性研究

在聚丙烯腈纺丝原液中添加四针状氧化锌晶须对聚丙烯腈纤维抗静电性具有改善作用。研究表明:氯化锌晶须添加量为1%(相对于聚丙烯腈干粉质量)就可以使聚丙烯腈纤维达到抗静电要求,体积比电阻率为5.4×1010赘·cm。     

Modern carbon fibres from polyacrylonitrile (PAN)-polyheteroaromatics with preferred orientation

This contribution presents the mechanical data of high performance carbon fibres currently available on the market, based on experimental studies on stabilization and pyrolysis of PAN (SAF) from Courtaulds. The effects of stabilization and carbonization temperatures on the properties as well as on the ultra- and crystalline structures of the fibres are shown in more detail.     

氧化锌晶须渗入聚丙烯腈纤维的抗静电性能

在乳液中悬浮的氧化锌晶须渗入聚丙烯腈纤维中,起到抗静电作用,聚丙烯腈纤维的体积比电阻率可降到4.1×108Ω.cm;四针状和单针状的氧化锌晶须的渗入能力不同,得到抗静电性能不同;渗入工艺简单方便,同时解决了氧化锌晶须添加入聚丙烯腈纺丝原液所造成的喷丝孔阻塞问题。     

聚丙烯腈/水滑石插层共混体系的结构和性能研究

采用原位聚合法,以过氧化二苯甲酰为引发剂,在形成水滑石的同时单体丙烯腈进入其层间并发生聚合反应,制备出聚丙烯腈/水滑石插层复合材料.用红外光谱、扫描电镜和X射线衍射对这种插层复合材料的结构进行了分析和表征,并对其燃烧性能和热性能进行了初步研究.结果表明:在水滑石片层之间通过原位聚合的方法生成了聚丙烯腈大分子,使水滑石层间距有一定程度的增大.聚丙烯腈/水滑石共混复合物的阻燃性能有一定提高,其极限氧指数(LOI)从18%提高到了21%;耐热性能得到一定程度改善.     

Correlation of physical and chemical properties of c-h-n-o explosives (part II)

In our previous paper⁽¹⁾ we correlated the physical, chemical, and thermodynamic properties of C-H-N-O explosives with their constant-volume explosion properties calculated by using the Taylor model implemented in the Nitrodyne code. In this paper, we added the correlations for the Chapman-Jouguet detonation properties calculated by using the Becker-Kistiakowsky-Wilson equation of state implemented in the TIGER code. By splitting the correlation variable (F) used in Reference 1 into a density term and a density-independent term (f), Chapman-Jouguet detonation pressure and velocity showed simple linear relationships with square root of the new correlation variable (f). Other detonation properties were derived from the detonation pressure and velocity: Correlation of constant-volume explosion properties with the new correlation variable (f) showed both a moderate improvement, compared to those with the old correlation variable (F), and a much simpler relationship.     

The chemical and physical properties of electrochemically prepared polyaniline perchlorate (PAP)

Polyaniline perchlorate (PAP) was synthesized by electrochemical oxidation from 0.2 M aniline in acetonitrile solution containing 0.1 M tetraethylammonium perchlorate as supporting electrolyte. From polarographic and cyclic voltammetry results, the values of the half-wave potential (E_1/2), transfer coefficient (α), and number of electrons related to the electrode reaction (n) were calculated to be 825 mV, 0.894, and 1, respectively. The morphology of the PAP film was observed by using an SEM analyzer. From thermal analysis of the PAP sample, the reaction rate (R) for its thermal decomposition was obtained from the TGA result and a exothermic peak at 330°C was also observed in the DSC curve. The electrical conductivity of the PAP pellet was measured at temperatures from ?170 to 25°C. From a plot of conductivity vs. 1/T, the activation energy (E_a) was obtained to be 0.14 eV. The conduction mechanism in a pressed pellet of PAP is suggested to be electronic hopping conduction. The values of the ESR parameters were calculated from an ESR curve for PAP at room temperature.     

Pneumatic spinning of chemical fibres (review)

Scientific-Research Center for Problems of Resource and Waste Management, Mytishchi, Translated from Khimicheskie Volokna, No. 4, pp. 27–29, July–August, 1995.     

Thermomechanical and chemical properties of cross-linked polyacrylonitrile fibres

Conclusions 1. We have studied the thermomechanical and chemical properties of PAN fibres, cross-linked by treating with hydrazine hydrate, semicarbazide, and thiosemicarbazide.2. Cross-linked PAN fibres have increased heat resistances and thermal stabilities.3. Cross-linked PAN fibres do not dissolve in any known organic solvents and are resistant to hot mineral acids and alkalies.Third communication on: Deformation and thermomechanical properties of cross-linked polyacrylonitrile fibres.All-Union Synthetic Fibre Research Institute (VNIIV). Translated from Khimicheskie Volokna, No. 2, pp. 49–50, March–April, 1969.     

Some chemical and physical properties of tailings water from oil sands extraction plants

We have carried out quantitative analyses of dissolved sodium, potassium, calcium, magnesium, chloride, carbonate, bicarbonate, ‘alkalinity’, sulphate, aluminum, iron, and silicon in tailings water from the GCOS tailings pond and from the Syncrude pilot plant. Surface tensions of these waters have been measured over a range of pH values, and effects of added Mg²⁺ and Ca²⁺ ions on surface tension have been investigated. Some similar measurements have been made on ‘synthetic pond water’. Infrared and proton n.m.r. measurements have been made on the organic material extracted from GCOS pondwater. This information on tailings water is relevant to the large accumulation of tailings that has become known as the ‘pondwater problem’ in connection with extraction of bitumen from mined Alberta oil sands.     

The chemical and physical properties of electrochemically prepared polyaniline hexafluorophosphate (PAPF6)

Polyaniline hexafluorophosphate (PAPF₆) was synthesized by electrochemical oxidation from 0.2 M aniline in acetonitrile solution containing 0.1 M TEAPF₆ as the supporting electrolyte. From polarographic and cyclic voltammetry results, the values of the half-wave potential $\left( {{\rm E}{\textstyle{1 \over 2}}} \right)$ and αn were calculated to be 774 m V and 0.589, respectively. The morphology of the PAPF₆ sample was determined from SEM. Thermal analyses for PAPF₆ and other polyaniline-based systems show distinguishable, thermal characteristics depending on the doping methods for the anions. Also, the maximum values (R_max) of the reaction rates (R) for these polymers were obtained. The electrical conductivity of the PAPF₆ pellet was measured at temperatures from ?170 to 25°C. From a plot of conductivity vs. 1/T, an activation energy (Ea) of 0.057 eV was obtained. The conduction mechanism in the pressed pellet of PAPF₆ is suggested to be hopping conduction. The various ESR-parameters were obtained from the ESR curve at room temperature.     

Relationship between physical properties and chemical structures of poly(ethylene terephthalate-co-ethylene isophthalate)

A series of copolyesters based on different ratios of polyethylene terephthalate (PET) to polyethylene isophthalate (PEI) have been synthesized. With the involvement of PEI, the copolyesters become less crystallizable and even amorphous when PEI content is above 20%. The WAXD profiles of the crystallizable copolyesters infer that the crystals come from PET homopolymer. DSC cooling runs indicated that the copolyesters with PEI no more than 15% are easily crystallizable, while the copolyester with 20% PEI is not easily crystallized at a cooling rate above 5°C/min. Heating runs indicated that the copolyesters with PEI below 20% show melting processes. Nonuniform results were provided by WAXD and DSC, however, the effect of PEI on the ability of crystallization was deduced similarly from WAXD and DSC. Glass transition temperatures have been measured by DSC. Due to the flexibility of PEI chain, glass transition temperatures of the copolyesters decrease linearly with increasing composition of PEI as predicted by the principle of additive contribution. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 73: 1191–1195, 1999