Physical aging in poly(methyl methacrylate) glass: densification via density fluctuation
Physical aging in poly(methyl methacrylate) glass: densification via density fluctuation
复制标题
聚甲基丙烯酸甲酯玻璃的物理老化：通过密度波动实现致密化
DOI：
10.1016/s0032-3861(98)00580-1
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发表时间：
1999
期刊：
影响因子：
4.6
通讯作者：
Takashi Inoue
中科院分区：
文献类型：
--
作者：
K. Takahara;H. Saito;Takashi Inoue
采用光散射和振荡dsc方法研究了聚甲基丙烯酸甲酯（甲基丙烯酸甲酯）在低于tg的退火过程中的物理老化，其中在传统的线性温升上施加正弦温升。光散射强度随散射角的增大而单调减小。随着退火时间的延长，强度先增大后逐渐减小。相关长度和deye - bueche图均方密度波动随时间的增加先增大后减小。振荡DSC热流的傅里叶变换处理得到的玻璃化转变宽度在早期随温度升高而增大，然后减小。由振荡DSC热流的非反转部分给出的吸热峰即使在老化的早期也出现了。结果表明：(1)淬火PMMA玻璃部分致密化，密度不均匀，相关长度约为200nm；(2)退火过程中，密度波动的增长首先表现为低密度区域密度的减小和低密度区域密度的扩大，从而增加了相关长度；(3)然后在低密度区域进行致密化，通过接近相当均匀的玻璃态来减小相关长度并获得整体上更高的密度。
The physical aging in poly(methyl methacrylate) during annealing just below Tgwas investigated by light scattering and oscillating-DSC in which a sinusoidal temperature rise was imposed over the conventional linear temperature rise. Light scattering intensity decreased monotonously with increasing scattering angle. The intensity was found to increase rapidly and then to decrease gradually with annealing time ta. The correlation length and the mean-square density fluctuations by Debye–Bueche plot increased at an early stage and then decreased with ta. The width of the glass transition, obtained by the Fourier transform treatment of the oscillated DSC heat flow, increased with taat an early stage and then decreased. The endothermic peak, given by the non-reversing part of the oscillating DSC heat flow, appeared even at an early stage of the aging. These results suggest that: (1) as-quenched PMMA glass is partially densified to yield an inhomogeneity in density with a correlation length about 200nm; (2) by the annealing, the density fluctuations grow at first by a decrease in density at the low density regions and an expansion of the low density regions to increase the correlation length; and (3) the densification then proceeds at the low density regions to reduce the correlation length and to get higher density as a whole, by approaching a rather homogeneous glassy state.