汽车外饰聚丙烯材料发白条纹产生的机理及影响因素  

Formation mechanism and influencing factors of whitening stripes in PP materials for automotive exterior

作　　者：魏丽霞 黄润鹏 赖辛长 蔡宽 WEI Lixia;HUANG Runpeng;LAI Xinchang;CAI Kuan(BYD Automobile Industry Co.,Ltd.,Shenzhen 518118,China)

机构地区：[1]比亚迪汽车工业有限公司,广东深圳518118

出　　处：《工程塑料应用》2025年第3期146-152,共7页Engineering Plastics Application

摘　　要：汽车上的塑料件在长期使用后容易出现耐候失效等问题,其中轮眉和保险杠等外饰产品表面容易出现交替的发白条纹,严重影响外观和品质。为促进上述问题的解决,通过氙灯加速老化试验在滑石粉填充聚丙烯(PP)复合材料注塑样板上复现了发白条纹的现象,并对相关机理进行了探讨。结果表明,PP样板发白现象主要是由表面光老化开裂及其导致的滑石粉外露所致,表面发白的区域O,Mg和Si元素含量显著上升;表面弹性体拉伸取向程度较高的区域在光照后更容易开裂,不同程度的交替取向导致光照后产生黑白区,即形成发白条纹。此外,进一步研究了影响PP材料光照后产生发白条纹的两种因素:一是材料体系中的PP基材,含再生料的材料因其更容易产生老化降解而在光照后更易产生发白条纹;二是距离注塑模具浇口的位置,远离浇口位置的材料流动性下降,可能使PP材料体系中的弹性体组分更容易产生拉伸取向,光照后材料更易开裂发白。为减轻PP材料光照后发白条纹对塑件外观的不利影响,可采取的改进措施包括选用耐候性能更好的PP基材、降低再生塑料添加量以及减少模具设计中的流长比。Plastic parts on vehicle are prone to failure caused by weather after long-term use.Among them,exterior products such as wheel arches and bumpers are prone to alternating whitening stripes on the surface,which seriously affects their appearance and quality.To promote the resolution of above problems,the phenomenon with whitening stripes was reproduced on injection molding sample plates of talc powder filled polypropylene(PP)composites by accelerating aging with xenon lamps,and the relevant mechanisms were explored.The results show that the whitening phenomenon of PP sample plate is mainly attributed to surface photoaging-induced cracking and the resulting exposure of talc powder caused by such cracking.The contents of O,Mg and Si elements in the white areas on the surface significantly increase.Areas with a higher degree of rubber stretching orientation on the surface are more prone to cracking when it is exposed to light,and varying degrees of alternating orientation result in black and white areas after illumination,which causing the formation of whitening stripe.In addition,two influencing factors of the occurrence of whitening stripe in PP materials was further researched.One is the PP base materials in the material systems,materials containing recycled ingredients are more prone to whitening stripe after exposure to light due to their increased susceptibility to aging and degradation.The second is the distance from the gate of injection mould,the flowability of materials far away from the gate position decreases,which may make it easier for the tensile orientation of the rubber in the PP material systems,and the materials are more prone to cracking and whitening after illumination.In order to mitigate the adverse effects of the whitening stripe caused by light exposure of PP on the appearance of plastic parts,the improvement measures can be implemented including adopting PP base material with better weather resistance,reducing the use of recycled plastics and decreasing the flow-length ratio in mould design.

关 键 词：外饰件 聚丙烯 发白条纹 耐候性 再生料 

分 类 号：U465.41[一般工业技术—材料科学与工程]