Shear modulus and internal friction of polymethyl methacrylate and polyethyl methacrylate between 4.2 and 100°K
Shear modulus and internal friction of polymethyl methacrylate and polyethyl methacrylate between 4.2 and 100°K
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聚甲基丙烯酸甲酯和聚甲基丙烯酸乙酯在4.2至100°K之间的剪切模量和内耗
DOI：
10.1002/pol.1959.1203512825
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发表时间：
1959
期刊：
影响因子：
--
通讯作者：
K. M. Sinnott
中科院分区：
文献类型：
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作者：
K. M. Sinnott
在4.2~100K温度范围内，测量了聚甲基丙烯酸甲酯和聚甲基丙烯酸乙酯的剪切模数和对数衰减率。所用的装置已在别处详细介绍过。它基本上是由一个悬挂在大型杜瓦容器底部刚性支撑上的小扭转摆组成的。摆的扭转运动是用电激发的，并用照相记录下来。图1和图2分别显示了聚甲基丙烯酸甲酯和聚甲基丙烯酸乙酯的剪切模数和对数衰减率随温度的变化。在4.2‘K下，聚甲基丙烯酸甲酯的剪切模数为3.20×10~(-1)达因厘米-z，在该温度下的对数衰减率为1.40×10~(-3)。在26K时，阻尼略降至1.04x，然后缓慢增加，达到5.87x。在4.2“K时，摆动频率为7.99秒-1。在聚甲基丙烯酸乙酯中，在4.2“K下的剪切模数为2.98×10~(-3)dynes·cm~(-2)，在此温度下的对数衰减率为5.37×10~(-3)。在此温度范围内，阻尼值随温度迅速增加，在41‘K时达到最大值39.7×10~(-3)。在这些实验期间，该装置没有被抽真空，因此给出的对数衰减值包括由于氦气体和支撑物而产生的衰减。这一估计约为0.1X的衰减对两种聚合物都是相同的，并在4.2-100K之间保持基本恒定，因此不会导致观察到的对数衰减随温度的变化。在98.1“K。
The shear modulus and logarithmic decrement of polymethyl methacrylate and polyethyl methacrylate were measured between 4.2 and 100 K. The apparatus used has been described in detail elsewhere.'It consists essentially of a small torsion pendulum suspended on a rigid support at the bottom of a large Dewar vessel. Torsional os-cillations of the pendulum are excited electrically and recorded photographically. The variation with temperature of the shear modulus and logarithmic decrement of polymethyl methacrylate and polyethyl methacrylate is shown in Figures 1 and 2, respectively. The shear modulus of polymethyl methacrylate was 3.20 X 1O1O dynes cm.-z at 4.2'K. The logarithmic decrement at this temperature was 1.40 X 10-3. The damping decreased slightly to 1.04 x at 26 K. and then increased slowly, reaching a value of 5.87 X The frequency of the pendulum oscillation at 4.2" K. was 7.99 sec.-1. In the case of polyethyl methacrylate, the shear modulus at 4.2" K. was 2.98 X 1Olo dynes cm.-2 and the logarithmic decrement at this temperature was 5.37 X The damping increased rapidly with temperature, reaching a maximum value in this temperature range of 39.7 x 10-3 at 41'K. Above this temperature the logarithmic decrement decreased slowly, reaching a value of 21.4 X 10-3 at 96.4" K. The frequency of the pendulum oscillation at 41 K. was 9.02 sec.-1. The apparatus was not evacuated during these experiments, so the values of the logarithmic decrement given include the damping due to the helium gas and the supports. This damping, which is estimated to be about 0.1 X would be the same for both polymers and would remain essentially constant between 4.2 and 100 K. It would not, therefore, contribute to the observed variation of the logarithmic decrement with temperature. at 98.1" K.