橡胶鞋外底表面涂层剥离特征研究

Peeling Characteristics of Removed Coating on Rubber Outsole Surface

目的研究橡胶鞋外底表面涂层剥离特征及其在刑事侦查与鉴定中的价值。方法用四氧化三铁粉末和自粘纸提取不同警用皮鞋外底若干天的鞋印,观察其整体涂层剥离痕迹,总结涂层剥离的形态种类。对各区域出现涂层剥离特征的鞋外底数量进行统计,对不同鞋外底涂层最大剥离面积进行统计,对不同鞋外底不同位置的涂层剥离特征的消失时间进行统计,对仍然存在涂层剥离特征的鞋外底最大剥离面积进行统计。最后观察涂层剥离痕迹的变化规律。结果涂层剥离特征反映为两种痕迹——涂层未脱落的涂层剥离痕迹与剥离的涂层本身形成的涂层剥离痕迹。雨水天气后的0~2 d以内,涂层剥离程度较大的鞋外底数量最多。涂层的最大剥离面积集中在0.019~1.451 mm2范围内,仅有9只涂层喷涂较厚的鞋外底剥离的涂层面积较大。涂层剥离痕迹主要出现在外底中腰部位、外底掌后部位、外底前端部位和轻微擦划处。穿用一个月以后,28只鞋外底仍有涂层剥离特征,其中包括9只喷涂较厚的鞋外底,28只鞋外底的最大剥离面积集中在0.204~3.805 mm2范围内。外底前端部位的涂层最先停止剥离;外底中腰部位的涂层,其剥离特征持续的时间最久,外底掌后部位次之,最次为外底前端部位。涂层剥离痕迹的总体变化规律为由边缘向内部收缩并逐渐消失。结论涂层剥离特征的反映性与鞋外底所喷涂层多少、水浸环境、客体粘附力,以及客体表面几何形状与涂层剥离部位的结合能力相关。其特定性和稳定性与鞋外底所喷涂层多少、出现的位置等相关。涂层剥离特征对于刑事侦查与鉴定有一定的意义。

The work aims to study peeling characteristics of removed coating on rubber outsole surface and corresponding values in criminal investigation and identification. Footwear impression samples of 86 police shoes were collected every day with Fe3O4 powder and self-adhesive films in 27 days. Overall coating peeling pattern was observed and then the coating peeling forms were classified into different types. Following items were counted： outsoles with different parts showing peeling characteristics, maximum peeled area of different outsole coatings, disappearance time of coating peeling characteristics in different positions of the outsoles, and maximum peeled area of outsoles still showing coating peeling characteristics. Finally, change rule of coating peeling patterns was observed. Two different patterns were reflected in the coating peeling characteristics： coating peeling pattern of coating not being peeled and that generated by the peeled coating. Largest number of outsoles exhibited greatest degree of peeling in 0~2 days after recent rainy day. Maximum peeled area of the coating was mainly in the scope of 0.019~1.451 mm2, only 9 outsoles painted thickly exhibited large area of peeled coating. Coating peeling patterns mainly appeared in arch part, posterior ball part, anterior part and slightly scratched part. After being worn for one month, 28 outsoles still exhibited coating peeling characteristics, including the above-mentioned 9 outsoles being painted thickly. The maximum peeled area of these 28 outsoles were mostly in the scope of 0.204~3.805 mm2. Coating in the anterior part stopped peeling first. The coating peeling characteristics in arch part lasted for the longest time, followed by those in the posterior ball part, and those in the anterior part the shortest. The general change rule of coating peeling patterns was that they shrunk from edge to inside and disappeared gradually. The reflective ability of coating peeling characteristics depends on volume of coating pained on outsoles, water immersion environment, adhesive force of the object, geometry of object surface and binding capacity of peeled part. The specificity and stability of paint removing characteristic are related to volume of the painted coating and the part in which they appear. Coating peeling characteristics are of certain significance to criminal investigation and identification.