纸张烧毁机理的热重法研究（英文）  

Research on Mechanism of Paper Burning by Thermogravimetric Analysis

作　　者：秦达[1,2] 韩星周[1,2] 王晓光[1] 齐凤亮[1] 王子杰[3] 郭姿含[1] 郝红光[1] 

机构地区：[1]公安部物证鉴定中心,北京100038 [2]中国刑事警察学院文件检验鉴定公安部重点实验室,沈阳110854 [3]西安市公安局雁塔分局,西安710061

出　　处：《刑事技术》2015年第4期275-279,共5页Forensic Science and Technology

基　　金：supported by grant from Key Laboratory of Questioned Document Examination,MPS(No.2014KFKT06,No.2014KFKT05);the Basic Research Program Exclusive for Central Government-class Institutes of Public Welfare(No.2015JB014)~~

摘　　要：烧毁文件是指因人为故意或过失,或者因火灾事故,使具有物证、书证作用的文件被燃烧后的残留物。文件烧毁后,纸张变脆,保存能力差,通常呈现焦化、炭化或灰化三种表观变化状态,但是这三种状态的形成机理及其如何区别一直没有一个清晰的界定,导致三个词语的混淆使用。本文采用热重分析方法对烧毁文件进行分析,研究纸张烧毁的不同程度和阶段,并对其烧毁机理进行探讨。首先采用热重法(thermogravimetric analysis,TGA)对5种纸张进行测试,得到了空气和氮气气氛下的不同热重曲线,结果表明:(1)5种纸张的热重曲线形状基本相同,均存在着三个明显的失重过程,说明纸张随温度升高的变化机理相同;(2)其他参数不变,随着升温速率的增大,热重曲线向高温区方向移动。尽管纸张的起始分解温度及最大热分解速率温度有所差异,但是热重曲线的形状基本保持不变;(3)复印纸的热重(thermogravimetric,TG)曲线和微商热重(derivative thermogravimetric,DTG)曲线表明,氧气的存在可以加速纤维素的分解。氧气浓度增加,DTG曲线上纤维素以及残留的焦的分解峰向低温方向移动,峰形变化也比较明显;(4)室温状态下逐渐升温,纸张质量降低,至120°C时到达一个平台,该部分失重为纸张中纤维素物理吸附的水分,此过程中纸张的性质基本没有发生变化。从210°C到470°C,纸张有较多的失重,主要是纸张中纤维素分解造成的。从580°C到670°C,失重是由于高温下填料(主要是碳酸钙)的分解造成的。温度继续增加,质量变化不大,残余物为纸张中热稳定的物质,为纤维素氧化后的炭和填料等。在210°C到470°C范围内,纤维素开始时并没有完全分解,部分裂解为焦;345°C后残留的焦氧化为炭和挥发性气体,在图像上显示为两部分斜率不同的曲线;(5)牛皮纸由于其纤维素木浆成分较多,升温时极易剧烈氧化并燃烧,在空�The examination of charred document is a challenge and usually requires a careful application of certain scientific techniques due to its unstable property. To address this issue, the mechanism of paper burning was studied in this paper. Here thermal-gravimetry （TG） was applied to investigate five kinds of paper, along with their TG and derivative thermogravimetric curve （DTG） observed at different atmospheric conditions. The results showed that the shape of curves, albeit similar, varied with the physical and chemical composition of paper. In the burning process, dehydration and depolymerization are the two main pathways for cellulose, the major ingredient of paper. The heating rate indicated little influence on the curves while the sort of atmosphere worked strongly. The reason is due to the lack of tar oxidation when nitrogen used as the atmospheric environment. At moderate temperature, de-polymerization prevails and the tar can be observed. With temperature increasing, the tar and cellulose are further decomposed, leading to products of high boiling-point. According to the results, the charred document can be classified as one of the dehydrated, tarred, charred and ashed. Except the ashed stage, the other three can be handled and the writing whereon can be deciphered. The results exposed hereof may provide a fundamental for examining and deciphering charred document.

关 键 词：文件检验 烧毁文件 热重分析 机理 

分 类 号：DF794.2[政治法律—诉讼法学]