Page 61 - 《摩擦学学报》2021年第4期

504 摩 擦 学 学 报 第 41 卷

after irradiation were characterized by infrared spectroscopy, X-ray diffraction and differential scanning calorimetry.
The thermal stability, tensile properties and tribological properties of the materials were compared with those of
irradiated pure PTFE. The results show that the chemical composition and thermal stability of PTFE/POB materials are
not significantly changed under irradiation, but the molecular weight of PTFE decreases sharply, and the small molecular
chains spontaneously form crystalline phase, leading to the increase of crystallinity. Compared with pure PTFE, the
addition of POB improves the radiation resistance of PTFE to a certain extent, and delays the decrease of molecular
weight and recrystallization ability of PTFE. The results showed that the tensile strength of PTFE and PTFE/POB
decreased significantly after irradiation, but for PTFE/POB, with the increase of irradiation dose, the decreasing trend of
the tensile strength of PTFE/POB was not significant, but gradually stabilized. The effect of irradiation on the elongation
at break of PTFE and PTFE/POB is complex. The elongation at break of pure PTFE increases first and then decreases
with the increase of irradiation dose, while the elongation at break of PTFE/POB decreases with the increase of
irradiation dose. The effect of irradiation on the wear resistance of PTFE/POB is not significant, but the friction
coefficient decreases to some extent. With the increase of irradiation dose, the friction coefficient first increases and then
decreases. This is mainly because with the continuous increase of irradiation dose, the molecular chain length of PTFE
becomes shorter and the size of crystal band becomes smaller, leading to the obvious increase of the grain boundaries. It
results in the increase of shear strength gradually, leading to the increase of friction coefficient.
Key words: polytetrafluoroethylene; γ-ray irradiation; crystallinity; molecular weight; friction and wear

聚四氟乙烯(PTFE)是核电站各级密封中的关键 研究了1 000 Gy~3 000 Gy剂量γ射线辐照后PTFE及其
密封材料，不仅承受高压、高速摩擦磨损，而且需满足 复合材料的摩擦磨损性能，重点考察γ射线辐照对材
4年以上的耐辐照寿命. PTFE虽具有优异的自润滑、 料化学结构、耐热性、力学等各项参数和性能的影响
耐高温和化学稳定性，但抗核辐照能力较差，在γ射线 程度，以期建立辐照环境下PTFE结构变化与摩擦磨
[1]
辐射下，极易发生分子链降解、交联和断裂 . Fayolle 损性能之间的相关性，为核电密封材料的设计提供指导.

[2]
等 研究发现，在γ射线辐射下，PTFE分子量随着辐照
1 试验部分
剂量的增大急剧降低. PTFE的形貌、化学结构均会因
γ射线辐照而发生改变，在无氧、高于其熔点温度环境 1.1 试验材料及制备
下，辐照会导致分子链的交联 [3-4] ；辐照导致的PTFE分 试验材料为中国科学院兰州化学物理研究所自
子链断裂、交联等可明显改变PTFE材料的力、光、热、 主研发的PTFE/POB材料，采用冷压烧结工艺制备. 辐
电学等性能 [5-6] . 此外，辐照同样会对PTFE材料的摩擦 照试验委托甘肃天辰辐照科技有限责任公司完成，辐
60
[7]
磨损性能产生影响. Singh等 研究了γ射线辐照后石 照源为 C ，辐照室温度12 ℃，辐照剂量率100 Gy/h，
O
墨改性PTFE材料摩擦磨损性能,发现50~150 kGy的辐 辐照剂量通过调整辐照时间来控制.

照剂量能够显著提高材料的摩擦磨损性能. Tang等 [8] 1.2 试验方法
研究了交联PTFE材料在γ射线辐照后的摩擦磨损性 采用万能试验机测试材料的拉伸强度和断裂伸
能，发现其摩擦系数随着辐照剂量的增加而减小，当 长率，试样为哑铃型，参考标准为GB/T 1 040.2-2 006，
辐照剂量达到0.2 MGy时，磨损率保持稳定，然后急剧 拉伸速率为50 mm/min. 采用德国Nerzsch公司的同步
[9]
恶化. Wang等 研究了0.1~20 MGy辐照剂量内PTFE 热分析仪测量试样的热分解温度，气氛为氮气，升温
材料的摩擦学性能，发现PTFE的摩擦系数随着辐照 速度为10 K/min. 采用德国Nerzsch公司的差示扫描量
剂量的增加逐渐增加然后趋于稳定，而磨损率却始终 热仪测量试样的熔融和结晶温度，气氛为氮气，升降

呈现上升趋势，尤其在5 MGy辐照剂量后，呈现急剧 温速度为10 K/min. 采用X射线衍射仪测量试样的结
上升趋势. 晶度. 利用傅立叶红外光谱仪对试样的化学结构进行
从上述关于辐照PTFE的摩擦学研究来看，现有 表征. 采用场发射环境扫描电子显微镜(FEI Quanta
研究均涉及的辐照剂量较高，最低剂量也高于50 kGy， 200FEG)观察材料的磨痕形貌.
而对于低辐照剂量下PTFE摩擦学性能的研究很少. 在 采用M-200摩擦磨损试验机测试试样的摩擦磨损
低辐照剂量下，PTFE材料的摩擦磨损性能是否表现 性能，参考标准为GB/T 3 960-2 016，试样尺寸为30 mm×
出高剂量下相同的结果尚未可知. 鉴于此，本文作者 6 mm×7 mm，摩擦对偶为GCr15，试验速度0.42 m/s，