The effect of gamma irradiation and shelf aging in air on the oxidation of ultra-high molecular weight polyethylene

This study has investigated the effect of shelf aging, for up to one year in air, on the properties of gamma-irradiated ultra-high molecular weight polyethylene (UHMWPE). A variety of techniques were used to characterize the properties of treated samples. Differential scanning calorimetery (DSC) was used to characterize the morphology. The extent of cross-linking in a polymer network was detected by swelling measurements. The durometer hardness test was used to measure the relative hardness of this material, and changes in density were also measured. Results from all these measurements were combined to explain the changes in the microstructure of the aged, irradiated UHMWPE. This study shows that crystallinity is increased with radiation dose and with aging due to chain scission, which leads to a reduction in the molecular weight of the material. This allows the chains to rearrange to form crystalline regions. Positron annihilation lifetime spectroscopy confirms these conclusions. Fractional free volumes have been deduced from lifetime parameters, which correlate with the data obtained by the other techniques.     

FRS-XRSA与SAXS研究硬弹性聚丙烯的结晶度、取向与超结构Ⅲ应变与回复

应用全倒易空间Ｘ 射线散射理论分析（ＦＲＳ ＸＲＳＡ）与ＳＡＸＳ研究了ＨＥＰＰ在应变（ε）与回复（Ｒ）过程中结晶、取向与超结构的变化．结果指出，ε可以诱发结晶，但当ε≥３０％后，结晶度（ＸＷＣ）趋于不变：ε可以导致晶粒破碎；ε与Ｒ对取向分布与平均取向基本上无影响，这符合片晶平行分离模型，而非叶簧弯曲模型；发现，在ε≤３０％时，层状片晶的分离为主要过程，而当ε＞３０％后，则分离的片晶会发生断层滑移；ε可以诱发微孔，类似地当ε＞２０％，微孔尺寸亦趋不变．从凝聚态结构阐明了ＨＥＰＰ在ε Ｒ过程中不同阶段的结构变化     

尼龙1010骤冷退火样品的晶体结构

尼龙1010的晶体结构属三斜晶系.作者最近导出了X射线衍射法(WAXD)测定尼龙1010结晶度的公式,进而考查了等温结晶时结晶温度T_C对结晶度X_C、晶粒尺寸L_(100)和氢键面相对衍射强度R的影响.发现X_C和L_(100)均随T_C升高而增大,达196℃后又减小;而R与T_C的关系则相反,呈线性降低.结晶速率快有利于分子链在垂直于氢键面的(100)晶面生长,但R值却降低了.本文利用WAXD考查了尼龙1010不同骤冷退火条件样品的晶体结构.     

Hydroxyapatite gels and nanocrystals prepared through a sol-gel process

We have investigated the effect of the Ca/P molar ratio on the structural and morphological properties of hydroxyapatite (HA) gels and nanocrystals. The sol-gel process was carried out in aqueous, and alternatively in alcoholic medium (50% water-50% ethanol), at 37°C. Gel samples were obtained by drying the sols at 37°C or at 80°C, whereas powder samples were obtained by filtering the sols. Heat treatment at temperatures as low as 300°C is enough to obtain pure HA from the gels with a Ca/P molar ratio of 1.00 and 1.67. At variance, heat treatment of the gels with a Ca/P of 2.55 always produces secondary phases. The degree of crystallinity of HA increases with the Ca/P molar ratio of the sols, and it is slightly affected by the presence of ethanol in the precipitation medium. Filtering of the sols provides powders constituted of nanocrystalline HA that exhibit degree of crystallinity, crystal morphology and thermal stability closely related to the sols composition.     

Using NaCl particles as porogen to prepare a highly adsorbent chitosan membranes

Macroporous chitosan membranes were prepared by using NaCl particles porogen and genipin as cross-linking agent. For characterization and sorption behavior comparison, other genipin cross-linked chitosan membranes were prepared by either freeze drying or by using silica particles as porogen. The mean pore diameter, the porosity, the crystallinity index (CrI) as well as the effect of the drying procedures of these chitosan membranes were examined. NaCl reduced the CrI of the chitosan membrane. The oven drying (OD) procedure decreased the mean pore diameter, the porosity, and increased the CrI of the chitosan membranes when compared with the vacuum drying (VD) procedure. The heat treatment of chitosan membrane in aqueous NaOH to attract silica porogen increased the CrI of the membrane. Under the same conditions, the membranes prepared with NaCl had better sorption performance on RR 189 and Cu²⁺ than other membranes. The maximum sorption capacity (q_e) reached 1836.17 mg RR 189/g chitosan and 151.98 mg Cu²⁺/g chitosan. The pore diameter (d_pore) of the membranes was much larger than the diameter of the adsorbate molecules (d_adsorbate), such that the ratio of d_pore/d_adsorbate had little influence on q_e. The porosity and the amorphous extent of the membranes were almost the same on q_e. When using tyrosinase catalyzing, the hydrocaffeic acid (HCA) grafted on the NaCl treated chitosan membrane was almost 10 times more than on chitosan beads. The chitosan membrane prepared with NaCl can be used as a good adsorbent with high loading capacity for implanting molecules (such as ligands, enzymes, etc.) on.     

溶液成膜的温度对聚对苯二甲酸乙二酯结晶度的影响

<正> 用溶液成膜是制备聚合物薄膜的常用方法之一。但是溶液成膜的条件,如成膜温度,溶液浓度等对半结晶聚合物结晶度的影响研究报道较少。制备聚对苯二甲酸乙二酯(PET)非晶态薄膜通常使用熔融热压其后淬火的方法。由于PET在熔点附近易于降解,在薄膜中产生气泡,因而很难制备较大面积的均一厚度的薄膜,如在拉伸试验中所需     

γ-射线辐照对尼龙6纤维结构的影响

<正> 过去的大多数研究表明,高能射线辐照会引起聚乙烯及聚丙烯等稀烃类聚合物分子链交联及降解,而且会导致结晶度下降。张利华等人最近的研究表明,对于尼龙1010塑料,仅当辐照剂量高到一定程度后,辐照才会破坏结晶。此外,Stowe等人曾经研究过近紫外线对尼龙66纤维结构的影响,结果表明,在空气气氛中的近紫外辐照主要导致尼龙66纤维降解,并使纤维结晶度提高。有关高能射线辐照对高度取向的合成纤维结构及性能的影响的研究尚不多见。本工作将讨论γ-射线对于尼龙6纤维结构的影响。     

含间苯基聚芳醚酮的合成与性能研究

含间苯基聚芳醚酮的合成与性能研究林权，张万金，吴忠文，尹玖梅（吉林大学化学系，长春，１３００２１）（中国科学院长春应用化学研究所）关键词聚芳醚酮，间苯基，熔点，结晶度聚芳醚酮作为一类耐高温特种工程塑料，由于具有优异的热、电、机械性能，已被广泛应用于电...     

偏氟乙烯／三氟乙烯共聚物介电松弛的结晶度效应

用改进的介电松弛谱仪（精度２‰）测定了ＶＤＦ／ＴｒＦＥ（７／２７、６５／３５、５２／４８ｍｏｌ％）共聚物溶液成膜、液氮淬火、熔融慢冷和热处理试样在－１２０—１３０℃、１０－２一１０４Ｈｚ范围的复数介电常数．介电松弛研究结果显示低结晶度的淬火试样较高结晶度的熔融慢冷和热处理试样的Ｔｃ高．结晶度上升，居里点处的介电常数增大．室温以下的介电频率谱分别由代表非晶区分子运动的β松弛（低频部）和局域运动的γ松弛（高频部）叠合而成．随结晶度提高，β松弛峰减小，γ松弛峰增大；非晶松弛强度减弱．晶区松弛强度增强．     

聚苯胺的化学合成及表征

本工作利用化学方法合成了具有较高电导率的聚苯胺.研究了聚合条件如反应介质的pH值,不同种类的酸及其浓度,氧化剂的用量对聚合的影响.用红外光谱、X-射线衍射、DSC等方法表征了所得的聚合物,并研究了该聚合物的掺杂反应.