摘要
塑料自问世以来给人类的日常生活带来极大改变和方便,但同时由于其难降解性而产生大量塑料垃圾.这些垃圾在光、物理、化学和生物等作用下发生破碎降解产生微塑料,成为环境中微塑料的一个重要来源.本研究选取生活中常见的食品包装袋、垃圾袋、厚塑料膜和快递包装袋等塑料薄膜制品开展UV光降解实验,通过拉伸性能检测,结合红外光谱和扫描电子显微镜手段,分析了它们在UV光降解过程中的性能变化特征.结果表明,6种塑料膜的断裂伸长率均随光照时间增加而降低,杨氏模量一般随光照时间增加先升高后降低,而拉伸强度随光照时间增加呈先升高后降低或者持续降低的变化趋势,食品包装袋和可降解垃圾袋在光照强度为160 W/m2的UV光照射36 h后发生脆化无法进行拉伸性能测试,易于破碎为微塑料,而快递包装袋180 h后断裂伸长率仍达76%;光降解过程中聚乙烯发生氧化断链反应,分子结构发生变化,食品包装袋光降解的主要产物为醚类物质,厚塑料膜和快递包装袋的降解产物包含酮、酯或酸类物质和乙烯基等,但聚乙烯作为塑料的主要成分没有变化;光降解后塑料的表面和拉伸断裂截面均产生细小裂纹,发生脆化.研究结果可以为环境中大片塑料垃圾的行为过程、微塑料来源及环境风险评估等研究提供基础数据.
Since its invention,plastic has brought great changes to our daily life.It is considered as one of the most basic materials for the development of modern society.Most of the plastic produced are used for packaging and disposable products.Due to the high disposable rate and mismanagement,a large amount of plastic debris enters the marine environment.Potentially lasting several hundred years in the environment,the large plastic debris can be continuously broken into microplastics which are smaller than 5 mm under the action of ultraviolet light,heat,wind,tide,wave and bacteria etc.Therefore,the amount of microplastics will keep rising in the ocean.Microplastics is considered as a new emerging pollutant and has become a global concern.Understanding the degradation process of plastic in the environment is important for evaluating the contribution of plastic debris as one microplastics source.In this work,polyethylene film from 6 kinds of packaging bags commonly used in our daily life,i.e.,food packing bag,garbage bag,thick film,and express packing bag,were selected to carry out photodegradation experiment under ultraviolet radiation in the laboratory.Properties of plastic films were investigated by tensile tests,infra-red spectrometry and scanning electron microscope at various time intervals.The results showed that the elongation-at-break of six kinds of polyethylene film decreased with increasing of UV exposure time.While Young’s modulus showed a trend of increase-decrease with increasing exposure time in general.The yield strength showed a general increasing-decreasing or decreasing trend with increasing exposure time.PE films from food packing bag and degradable garbage bag became brittle and tended to break into microplasics after 36 h under UV irradiation of 160 W/m^(2).However,the retained elongation-at-break of PE film from express packing bag was up to 76%after 180 h UV irradiation.Chain scission and structure changes occurred during photodegradation process.FT-IR spectra indicated that difference existed in photodegraded process among PE films from six kinds of plastic bags.Ether group existed in FT-IR spectra of PE film from food packing bag,while ketone,ester,carboxylic acid,and vinyl group appeared in the spectra of thick film and express packing bag.Carbonyl index,crystallinity index and vinyl index of films from food packing bag,thick film and express packing bag increased at various degrees with prolongation of exposure time.The microstructure at tensile fracture surface became smoother after photodegradation,showing appearance of small fragments.This indicated that the intermolecular force decreased significantly,which was consistent with the trend of mechanical properties.The plastic packing bags commonly used in our daily life tend to become brittle and fragment into small pieces under ultraviolet radiation and become one source of microplastics in environment.These results can provide basic data and theoretical support for study of environmental behavior processes of plastic debris and source of microplastics,assessment of environmental risk,etc.
作者
蒋凤华
谢林青
孙承君
张雨
李景喜
鞠鹏
Fenghua Jiang;Linqing Xie;Chengjun Sun;Yu Zhang;Jingxi Li;Peng Ju(Key Laboratory of Marine ECO-Environmental Science and Technology,Marine Bioresource and Environment Research Center,First Institute of Oceanography,Ministry of Natural Resources,Qingdao 266061,China;Laboratory of Marine Drugs and Bioproducts,Pilot National Laboratory for Marine Science and Technology(Qingdao),Qingdao 266071,China)
出处
《科学通报》
EI
CAS
CSCD
北大核心
2021年第13期1571-1579,共9页
Chinese Science Bulletin
基金
中央级公益性科研院所基本科研业务费专项(2019Y03,2020Q10)
自然资源部“自然资源调查评价实验试验技术支撑体系建设运行”项目资助。
关键词
光降解
微塑料
聚乙烯
拉伸性能
红外光谱
扫描电子显微镜
photodegradation
microplastics
polyethylene
tensile property
infrared spectroscopy
scanning electron microscope
