SC-CO_(2)辅助发射药代料挤出过程中物料流动性与制品冲击强度

Impact Strength and Rheological Properties of Propellant Substitutes Assisted with SC-CO_(2)

为了研究超临界二氧化碳(SC⁃CO_(2))的注气量、醇酮溶剂比、加工温度、螺杆转速等工艺条件对SC⁃CO_(2)辅助发射药代料醋酸纤维素(CA)挤出过程中物料流动性与制品冲击强度的影响,采用在线狭缝流变仪、落锤冲击试验机、扫描电镜等实验方法,对不同的工艺条件下挤出过程中的物料流动性、制品的冲击强度及内部形貌进行了表征。研究结果表明:随着SC⁃CO_(2)注气量的增加,物料的挤出流动性得到有效改善,但制品的冲击强度出现了降低:在温度为50℃,SC⁃CO_(2)/CA注气质量比为0.173%时,螺杆转速为10 r·min^(-1)时,注气制品的冲击强度(6.32 kJ·m^(-2))仅占同条件未注气下冲击强度(11.90 kJ·m^(-2))的53.11%;提高螺杆转速可改善制品的冲击强度和制品形貌,螺杆转速为14 r·min^(-1)时制得的制品冲击强度(7.12 kJ·m^(-2))是螺杆转速为6 r·min^(-1)时制品冲击强度(4.18 kJ·m^(-2))的170.33%;制品断裂截面处的扫描电镜结果显示,SC⁃CO_(2)辅助挤出的制品中存在较多的泡孔:在温度为50℃,SC⁃CO_(2)/CA注气质量比由0.173%提高到0.347%时,制品内部的泡孔尺寸均大于2μm,部分甚至达到15~25μm。在SC⁃CO_(2)辅助发射药代料挤出过程中,提高SC⁃CO_(2)的注气量、醇酮溶剂比、加工温度、螺杆转速均能改善物料的流动性,提高螺杆转速能改善制品的冲击强度。

In order to study the problem of impact strength and rheological properties of propellant substitutes(Cellulose Ace⁃tate,CA)assisted with supercritical carbon dioxide(SC⁃CO_(2)),the in⁃line slit rheometer,drop hammer impact test machine,SEM were used,and the rheological properties,impact strength and cell morphology of product were characterized in varied ex⁃periment conditions.Research results prove that,when process temperature is 50℃,solvent ration is 1.2 mL·g^(-1),flowability of CA is optimized evidently as injection speed of CO_(2) increasing.However,impact strength of extrusion product only account for nearly 53.11%of those products prepared without SC⁃CO_(2)(when injected mass fraction of SC⁃CO_(2)/CA is 0.173%,screw speed is 10 r·min^(-1));SEM results prove that,quantities of irregular foam structure exist in product prepared with SC⁃CO_(2),foam size are both over 2μm,some of them even reach at 15-25μm.Impact strength and product appearance could be modified as screw speed increase,product prepared in 14 r·min^(-1) attain higher impact strength(nearly 170.33%)than 6 r·min^(-1).During the pro⁃cess of propellant substitutes assisted with supercritical carbon dioxide,rheological properties of CA in barrel could be optimized as injection speed,solvent ratio,process temperature and screw speed increase,however,impact strength of CA could be posi⁃tively modified as screw speed increase.