Determination of the leveling‐off degree of polymerization of cotton and rayon
Determination of the leveling‐off degree of polymerization of cotton and rayon
复制标题
棉和人造丝均化聚合度的测定
DOI：
10.1002/pol.1953.120100608
复制
发表时间：
1953
影响因子：
3.4
通讯作者：
V. Tripp
中科院分区：
文献类型：
--
作者：
M. L. Nelson;V. Tripp
酸对纤维素的作用已经通过许多实验表明，随着处理时间的延长，首先非常迅速地降低残余物溶液的特性粘度。然而，很快达到这样一个阶段，即延长酸处理时间对粘度产生的进一步变化非常小。由该极限特性粘度计算的纤维素的聚合度被称为“极限聚合度”。Battista 6更喜欢术语“聚合的拉平度”（用DP表示，表示平均拉平“DP”），因为如果纤维素充分水解，它应该降低到真正的“限制DP”，即，葡萄糖。[6]拉平DP的重要性在于它是一个精细结构单元，即作为平均微晶长度 * s 7或通过一个结晶区和一个无定形区的纤维素链的平均长度的指示。Kanby、Ribis和M~ rehead的电子显微照片以及Jiirgensen关于水纤维素中链长频率分布的9-11数据提供了证据，证明了平坦化DP与平均微晶长度有关;但是没有足够的信息来得出关于无定形区域是否有助于平坦化DP值的结论。鉴于平整DP作为精细结构特征参数的可能有用性，本研究旨在了解其数值是否受水解条件变化的影响，并确定将来用于表征各种样品的条件，在此条件下可能获得平整DP的可靠值。建议收集和检查适当的数据，以确定水解可能导致的结晶-无定形比增加的迹象。Inger~ oll，Howsmon，13 Hermans and Weidinger，14 Battista，6 and Rozegare讨论了这种效应. [16]选择测量的性质是吸湿性，因为它是美国化学学会的一个通用性质，大西洋城，新泽西，1949年9月18-23日。
The action of acids on cellulose has been shown by a number of to decrease the intrinsic viscosity of solutions of the residues at first very rapidly with time of treatment. However, a stage is soon reached when prolongation of the acid treatment produces very little further change in the viscosity. The degree of polymerization of the cellulose calculated from this limiting intrinsic viscosity has been termed by some 3-5 the “limiting degree of polymerization.” Battista6 prefers the term,“leveling-off degree of polymerization”(symbolized by DP to signify the average leveling-on’DP), since if cellulose is hydrolyzed sufficiently it should be reduced to a true ‘‘limiting DP” of one-ie., to glucose. 6 The importance of the leveling-off DP lies in its interpretation as a finestructural unit, that is, as an indication of either the average crystallite length* s7 or the average length of cellulose chains passing through one crystalline and one amorphous regi~ n.~ The electron micrographs of Kanby and Ribis and M~ rehead,~ arid Jiirgensen’s 9-11 data on chain-length frequency distributions in hydrocelluloses, afford evidence that the levelingoff DP is related to the average crystallite length; but there is insufficient information to conclude as to whether the amorphous regions do or do not contribute to the leveling-off DP value. In view of the probable usefulness of the leveling-off DP as a parameter of fine-structural characteristics, this study was designed to find out if its numerical value is affected by variations in the hydrolysis conditions, and to establish, for future use in characterizing various samples, the conditions under which a reliable value of the leveling-off DP might be obtained. It was deemed advisable to collect and examine appropriate data for indications of an increase in the crystalline-amorphous ratio which might occur as a result of hydrolysis. Such an effect has been discussed by Inger~ oll,’~ Howsmon, I3 Hermans and Weidinger, 14 Battista, 6 and Roseveare. 16 The property chosen for measurement was moisture adsorption, since it is gener-of the American Chemical Society, Atlantic City, New Jersey, September 18-23, 1949.