Influence of the fold surface of the lamellae on radiation effects—research on irradiated polyamide-1010 containing heterogeneous nuclei

Irradiated polyamide-1010 (PA 1010) and PA 1010 containing 0.5% (wt) heterogeneous nuclei were studied by ESR, WAXD, DSC and the determination of gel fractions. The fold surface of the lamellae plays an important role in the effects of radiation on crystalline PA1010. The results show that the direct radiation effects on both samples vary, while after being heated to 220°C, the final radiation effects are identical, regardless of the difference in the amount of the fold surface of the lamellae. The post-radiation effects result predominantly from the fold surface.     

聚酰胺1010电池壳的生产工艺探讨

介绍聚酰胺1010电池壳的生产工艺,探讨了影响聚酰胺1010注塑件质量的因素及可采取的相应对策。     

高分子共混物的相结构对力学性能的影响

本文以聚丙烯 尼龙1010(PP PA1010)共混体系为模型研究了高分子共混物的微观相结构对宏观力学性能的影响,并通过微观力学模型来预测共混物的拉伸强度。通过光散射试验和扫描电镜结果讨论了两相平均弦长比(L1 L2)以及分散相的质心相关距(D)与拉伸性能的关系。结果表明,当分散相一定时,拉伸强度随两相相对尺寸的增大和分散相颗粒相关性的减弱而减小。理论计算的分散相最小体积分数与相形貌观察的结果非常接近,添加增容剂的体系,由于改善了界面粘合,使理论预测值与试验结果很好的吻合。     

Crack growth mechanism in some polyamides

Fracture toughness was measured with single-edge notched three-point bend specimens. The materials used were semicrystalline polymers, polyamide-66, polyamide-1010 and polyamide-610. Their fracture surface was investigated with the help of scanning electron microscopy. The crack growth mechanism is revealed and a model suggested. The stable crack growth feature of the fracture surface is the dimples. The stable crack growth includes: the crack tip blunting, the voids initiating, coalescing and extending, the fibrillated polymer rupturing and contracting, then the formation of dimples on the fracture surface. The unstable crack growth formed a fan cleavage zone. The crack growth passed along the boundaries of spherulitic crystals in which many subcracks have occurred. The mechanism of discontinuous subcrack propagation in ductile polyamide-610 was discovered. In the compressive zone of the bend specimen, the fracture mechanism is similar to the cleavage zone and exhibits shear failure response.     

离聚体增容PA1010／SBS共混物的研究

采用磺化丁基胶锌盐(ZnSIIR)离聚体作为PA1010/SBS共混物的增容剂,研究了共混体系的结构、形态、相容性及对材料冲击性能的影响。结果表明,ZnSIIR的加入有效改善了SBS在PA1010中的相容性;对PA1010结晶起成核作用,并加快其结晶速率;共混物缺口冲击强度得到提高,且在PA1010/SBS为90/10、ZnSIIR为SBS的10％左右时效果较佳。     

Effect of multi-walled carbon nanotubes on the lamellae morphology of polyamide-6

We show that crystal organization on both micro and nanoscales can be profoundly modified by dispersing carbon nanotubes (CNTs) in polyamide-6 by melt compounding. X-ray diffraction and transmission and scanning electron microscopies all indicate that when CNTs are well dispersed, crystalline spherulites are not present and remarkably crystalline lamellae grow aligning perpendicularly to the surface of the nanotubes. Such an epitaxial growth induced by CNTs during melt processing is particular to polyamide-6 because of crystallographic matching of CNTs and polyamide-6 crystal lattices. Macroscopically this epitaxial nucleation and growth can be detected and quantified by examining the splitting of the exothermic peak in calorimetric (DSC) experiments. Using optical microscopy and image analysis we show that the amount of trans-crystalline epitaxial crystallites increases when CNTs' dispersion quality is improved.     

Molecular Dynamics Simulations of Calcium Silicate Intergranular Films between Silicon Nitride Crystals

Molecular dynamics simulations were used to study the structure of calcium silicate intergranular films (IGFs) formed between the basal planes of silicon nitride crystals. A multibody potential was used to describe the interactions between ions. Samples with different film thickness and CaO contents were studied. Epitaxial adsorption of Si and O atoms from the intergranular films onto N and Si, respectively, in the crystal surface was observed. This epitaxial order induced a structural order into the nominally amorphous IGF that decreased as a function of distance from the IGF/crystal interface. A higher concentration of strained siloxane bonds was observed at the IGF/crystal interface in comparison to the amorphous interior of the IGF. While Ca ions were observed to segregate to the IGF/crystal interface in simulations of calcium silicate glass IGFs between alumina crystals, no segregation of calcium to the first adsorbed layer on the nitride was found in these simulations using silicon nitride crystals. Planar alignment of Ca ions parallel to the IGF/crystal interface occurred with either the largest concentrations of CaO or with the thinnest IGFs studied here. This alignment creates localized nonbridging oxygen that would affect the stability of the IGF/crystal system.     

The effect of reactive compatibilization of carboxylated polystyrene on morphology and toughness of polyamide-1010/polystyrene blends

The morphology and notched impact behaviour of polyamide-1010/polystyrene (PA1010/PS) (90/10) blends compatibilized by carboxylated polystyrene (CPS) have been studied. It is found that the addition of CPS has a beneficial effect upon the morphology of the resulting blends which leads to a finer dispersion of the PA1010 spherulites and of the PS particles in the PA1010 matrix. However, with increasing CPS content, the shape of the PS domains appears less regular, which may be due to the cracking of the PS spherical domains. Infrared analysis was performed to confirm the formation of PS–PA1010 graft copolymer during the blending process. The notched impact toughness of the compatibilized blends shows a maximum which is almost triple that of the binary blend at approximately 5 wt% of the CPS addition based on the amount of PS. © 1999 Society of Chemical Industry     

Interfacial Interpretation of Autohesion of Ethylene/1-Octene Copolymers by Atomic Force Microscopy

The T-peel fractured surfaces of bonded films of ethylene/1-octene copolymers with different 1-octene contents were characterized using atomic force microscopy (AFM) and analyzed by fractal analysis. The AFM images showed strong dependence on the bonding temperature, peel rate, and the 1-octene content visually. This dependence has been demonstrated quantitatively by the fractal analyses which quantified an irregular surface by fractal dimensions and characteristic sizes. Two regimes showing fractal features were identified for each surface. In Regime I (higher magnifications) the welding and the following T-peel fracture procedures did little to change the fractal dimensions compared with the original surfaces before welding. But there were significant changes in Regime II (lower magnification) before welding and after T-peel fracture tests. The length scale that separated these two regimes is of the same order as that of polyethylene lamellar crystal structures. This suggests that the amorphous chains interdiffused across the interface while unmelted interfacial crystal structures remain essentially unaltered during the autohesion process. A “stitch-welding” autohesion mechanism was proposed to describe the bonding process in which only chains in the amorphous portions could interdiffuse. During the T-peel fracture tests, a crystal structure on the interface is either pulled over to the other side of the interface due to the interdiffused chains, remains unchanged, or is used as an anchor to pull a crystal structure from the other side of the interface. The characteristic sizes at which the fractal characteristics emerge were shown to be larger for the surfaces fractured at higher peel rates, which corresponds to higher fracture energy. This suggests that the appearance of fractal behavior at larger scales requires higher fracture energies. The characteristic sizes and fractal dimensions were also shown to depend on the molecular structure.     

Interfacial Interpretation of Autohesion of Ethylene/1-Octene Copolymers by Atomic Force Microscopy

The T-peel fractured surfaces of bonded films of ethylene/1-octene copolymers with different 1-octene contents were characterized using atomic force microscopy (AFM) and analyzed by fractal analysis. The AFM images showed strong dependence on the bonding temperature, peel rate, and the 1-octene content visually. This dependence has been demonstrated quantitatively by the fractal analyses which quantified an irregular surface by fractal dimensions and characteristic sizes. Two regimes showing fractal features were identified for each surface. In Regime I (higher magnifications) the welding and the following T-peel fracture procedures did little to change the fractal dimensions compared with the original surfaces before welding. But there were significant changes in Regime II (lower magnification) before welding and after T-peel fracture tests. The length scale that separated these two regimes is of the same order as that of polyethylene lamellar crystal structures. This suggests that the amorphous chains interdiffused across the interface while unmelted interfacial crystal structures remain essentially unaltered during the autohesion process. A “stitch-welding” autohesion mechanism was proposed to describe the bonding process in which only chains in the amorphous portions could interdiffuse. During the T-peel fracture tests, a crystal structure on the interface is either pulled over to the other side of the interface due to the interdiffused chains, remains unchanged, or is used as an anchor to pull a crystal structure from the other side of the interface. The characteristic sizes at which the fractal characteristics emerge were shown to be larger for the surfaces fractured at higher peel rates, which corresponds to higher fracture energy. This suggests that the appearance of fractal behavior at larger scales requires higher fracture energies. The characteristic sizes and fractal dimensions were also shown to depend on the molecular structure.     

PA／PP—g—MAH／PP共混物的界面和形态研究

用小角X光衍射和偏光显微镜等方法研究了具有相容区的PA101／PP-g-MAH/PP熔融共混物的界面和结晶开态，PA101和PP－g-MAH在熔融共混过程中生成新的基团，在相间存有界面，体系中两相的结晶形态均匀，共混物的拉伸屈服强度随着界面层厚度的增大而提高。     

A contribution to the understanding of polyethylene/ionomer/polyamide-6 blends

It has been reported that the addition of specific copolymers can improve the mechanical properties of blends of polyethylene with polyamide-6. One of these, a poly(ethylene-co-methacrylic acid) (EMA) containing between 4 and 15 mol % of methacrylic acid units, has often been used. Binary polyethylene/EMA and EMA/polyamide-6 blends were studied with the hope that the role of EMA as a compatibilizer in polyethylene/EMA/polyamide-6 ternary blends might be better understood. Differential scanning calorimetry (DSC), laser small-angle light scattering, and mechanical property results are discussed. DSC measurements show that one component of the binary blends does not modify the crystallinity of the other. However, laser small-angle light scattering shows that the morphology of the mixtures changes under similar conditions. Tensile properties of polyethylene/EMA binary blends vary linearly as a function of composition, whereas those of EMA/polyamide-6 blends deviate slightly from linearity. These results indicate no interaction between the crystalline components of the mixtures, and weak interactions in the amorphous phase.     

钛宝石晶体中的位错以及退火对位错的影响

用化学腐蚀剂腐蚀出样品的 (0 0 0 1)表面上的位错蚀坑 ,在原生态和退火样品的对应径向线上测量了位错腐蚀坑的密度分布 .由位错腐蚀坑的形成理论确定出原生态晶体中很可能有 3种位错类型 ,即Burgers矢量b =13〈112 0〉 ,13〈110 1〉和〈10 10〉的位错线 ,然而长时间在还原性高温气氛中的退火难以降低晶体中的总的位错密度 .在晶体的放肩至等径生长阶段 ,沿着晶体的生长方向 ,晶体棒中心的位错密度由高变低 ,这显示出 :在晶体的放肩至等径生长的转变过程中 ,生长界面发生了翻转 ,由凹形界面转变为凸形界面 ,位错线随之从晶体棒的中心向边缘发散 .     

Investigation of UV aging influences on the crystallization of ethylene-vinyl acetate copolymer via successive self-nucleation and annealing treatment

Influences of UV aging on the crystallization of ethylene-vinyl acetate copolymer (EVA) were researched via successive self-nucleation and annealing (SSA) treatment. During the aging process, the polar vinyl acetate (VAc) units in the amorphous region were the most vulnerable structure. FTIR results demonstrated that, VAc units were initially attacked by the UV radiation, which further resulted in chain scission of molecules. Degradation expanded from the amorphous region to the crystal region gradually. Chain scission reaction freed crystallizable ethylene sequences from inter-/intra-molecular tanglement and confinement of neighboring VAc units. Although the crystallinity decreased after aging, newly freed crystallizable sequences preferentially arranged into more densely packed lamellae, leaving less residual fraction to arrange into loosely packed crystal region. WAXD patterns showed that the predominant orthorhombic crystal phase did not vary during aging. Simultaneously, re-arrangement in crystallization also resulted in the growth in lateral crystal size of EVA.     

溶胶-凝胶法制备SiO2-TiO2纳米复合薄膜的结构及光学性能研究

采用ｓｏｌ－ｇｅｌ工艺制备了（－ｘ）ＳｉＯ２－ｘＴｉＯ２（ｘ＝５％,８％,２０％,３０％,４０％,５０％摩尔分数）纳米复合薄膜,Ｘ射线衍射及折射率测量表明,随着ＴｉＯ２摩尔分数的增加,薄膜的折射率呈线性增加,而ＴｉＯ２的析晶温度则降低,随着薄膜热处理的提高,其折射率亦增加,主要来自于薄膜结构转变的贡献,即由非晶态转变为锐钛矿相,由锐钛矿转变为金红石与锐钛矿两相共存两转变为完全的金红石相结构,并诱导     

Tensile deformation of semi-crystalline polymers by molecular dynamics simulation

In this work, the microstructure evolution of semi-crystalline polymers during tensile deformation is analyzed by molecular dynamics simulation. A perfect semi-crystalline lamellar structure with crystalline/amorphous interface perpendicular to tensile direction is created with the help of coarse-grained (CG) model of poly(vinyl alcohol) (PVA). During the tensile test, two kinds of strain rates are applied to the lamellar stack to determine the stress–strain curves, yield stresses, and crystallinities. Consistent with experimental findings, two yield points were observed in the semi-crystalline sample which was corresponded to the fine and coarse crystallographic slips in the lamellar structure, where the crystal stems gradually rotated into the direction of applied stress during chain slips. After the second yielding point when the crystal stems had been rotated fully into the direction of applied stress, the lamellar structure was destroyed and it resulted in a decrease of crystallinity. In addition, the increase of the strain rate led to the acceleration of destruction of crystal structures. It is worth noting that the stress induced crystallization was observed in the interfacial region, and newly crystallized beads were belonged to the same microcrystalline domain as crystalline region due to memory effects. This work provides direct comparison of structure evolution between crystalline and amorphous region in semi-crystalline polymers during tensile deformation, and it is helpful for the design and mechanical property analysis of semi-crystalline polymers.     

Milling media effects on synthesis,morphology and structural characteristics of single crystal hydroxyapatite nanoparticles

Abstract

This paper presents a dry mechanochemical process to produce hydroxyapatite (HAp) nanoparticles. Two distinct chemical reactions are introduced to prepare HAp powders using milling process. Structural and morphological properties of the obtained materials are studied by X-ray diffraction and transmission electron microscopy. The results reveal that the single crystal HAp nanoparticles have been successfully produced in metallic and polymeric vials through two different experimental procedures. Tempered chrome steel and polyamide-6 materials are adopted as the metallic and polymeric vials respectively. Nanoellipse, nanorod and nanosphere powders are obtained in these experimental procedures. Moreover, the obtained HAp powders through two distinct reactions exhibit average sizes about 12 and 15?nm using the tempered chrome steel vials, and about 16 and 17?nm using the polyamide-6 vials. The results indicate that single crystal HAp nanoparticles produced in polyamide-6 vials have suitable morphology and high production efficiency without any chemically stable contaminations.     

等通道转角挤压对PA1010结晶结构和力学性能的影响

探索了各种挤压工艺条件对PA10 10结晶结构和力学性能的影响。结果表明 :经过挤压后PA10 10的结晶度高于原始试样的结晶度 ,拉伸强度也高于未经挤压的PA10 10的拉伸强度 ,最大增加幅度为 2 1% ,增大幅度与挤压工艺条件有关。等通道转角挤压对材料结晶结构和力学性能均有重要的影响。     

SPET离聚物与尼龙6共混纤维结构性能的研究

将分子链相对较为刚性的ＳＰＥＴ离聚物与尼龙６(ＰＡ６)进行共混纺丝实验,通过ＷＡＸＤ、ＤＳＣ、Ｓ－Ｓ曲线的测定等方法着重考察了体系中离子基团的引入对共混物结晶性、晶体结构、力学性能等的影响,结果表明:离聚物的存在有利于体系结晶成核,但也在一定程度上破坏了晶区的完善性。ＳＰＥＴ/ＰＡ６共混纤维的初始模量随其所含离聚物量的增多而下降。     

Structure and drawability of gel films from formalization of high molecular weight poly(vinyl alcohol) aqueous solution

In this work, the structure and drawability of dried formalized gel films prepared from the formalization of high molecular weight polyvinyl alcohol (PVA) aqueous solutions were studied. Structure changes in PVA crystal were found in the formalized samples, i.e., the spacing of the (100) plane for PVA crystal became much larger while that of the (020) plane became smaller, indicating that some disordered crystals were formed from formalized PVA chains. The crystal relaxation temperature, T_αc, and its dependence on the draw ratio in formalized films were lower than those in original the PVA. Irrespective of the lower crystalline properties and the crystal relaxation temperature, the drawability of formalized PVA films could not be improved. The crystal orientation function, f_c, decreased as the degree of formalization at a given draw ratio was increased, indicating that the acetal groups in the amorphous region must be a hindrance to the drawing of the formalized PVA. These results implied that the drawability of PVA is not only related to the properties of the crystalline region but also to those of the amorphous region.