定应变加速老化条件下HTPB衬层交联密度老化模型

为了对定应变贮存老化条件下端羟基聚丁二烯(HTPB)衬层横向弛豫特性和交联密度的变化规律进行研究,设计了0%、5%、10%、15%定应变水平下HTPB衬层的加速老化试验,采用低场~1H NMR CPMG序列对HTPB衬层的质子横向弛豫衰减曲线进行了测试,并根据修正的单链模型计算得到了HTPB衬层的交联密度,分析了交联密度的变化规律,同时建立了考虑物理拉伸和化学老化因素的交联密度老化模型,对老化模型参数的影响因素和变化规律进行了研究。结果表明,定应变贮存老化条件下HTPB衬层的交联密度呈现先增大后降低的趋势,定应变的存在会导致HTPB衬层的应力松弛时间增加,但是对HTPB衬层的老化反应速率常数没有显著的影响。建立的交联密度老化模型的具体形式为ν_(NMR)(ε,t)=ν_(p0)(ε)τ(ε)1-exp(-t/τ(ε))]+ν_(ini)-k (ε) t,该模型与试验结果的相关系数R0.9500(5%定应变时相关系数R0.9000),可以用来描述定应变条件下HTPB衬层交联密度的老化规律。

Cross-linking Density Aging Model of HTPB Liner under the Accelerated Aging Condition with Constant Strain

To study the change rule of transverse relaxation characteristics and cross-linking density of hydroxyl-terminated polybutadiene(HTPB) liner under the condition of constant strain storage aging, accelerated aging tests of HTPB liner at 0%, 5%, 10% and 15% constant strain levels were designed. The proton transverse relaxation decay curves of HTPB liner were measured by the low-field ¹H NMR CPMG sequence and the cross-linking density of HTPB liner was calculated and obtained based on the modified single chain model. The change rule of cross-linking density was analyzed. At the same time, a cross-linking density aging model considering physical stretching and chemical aging factors was established and the influence factors and changing rule of the parameters of aging model were studied. The results show that the cross-linking density of HTPB liner shows a trend of increasing firstly and then decreasing under the condition of constant strain storage aging. The existence of constant strain causes an increase of the stress relaxation time of HTPB liner, but it has no significant effect on the aging reaction rate constant of HTPB liner. The specific form of established cross-linking density aging model is . The correlation coefficient R is more than 0.9500 (R>0.9000 at 5% constant strain) between the model and the experimental results, which can be used to describe the aging law of crosslink density of HTPB liner under constant strain conditions.