Polypropylene Special For Lightweight And Low VOC Automotive Parts

With the strengthening of people's awareness of sustainable development and environmental protection,the requirements for automobile fuel saving,emission reduction and performance improvement are gradually increasing.Lightweight automobile has become the trend of modern automobile industry technology development.In recent years,the main ways to realize the light weight of automobiles are as follows: the main specifications of automobiles are continuously optimized,while the main parameters of specifications are kept,the structural strength of the whole automobile is improved,and the consumption of consumables is reduced;Light weight materials such as aluminum,magnesium,ceramic,plastic,glass fiber or carbon fiber composite materials are adopted;The structure is designed by computer.For example,finite element analysis,local reinforcement design,etc.It adopts a load-bearing body and reduces the thickness of the sheet metal of the body.Polypropylene,which accounts for the largest proportion of automotive plastics,has the advantages of low density,chemical corrosion resistance,weather resistance,good processing,etc.In this paper,polypropylene is foamed to further improve and reduce its density,thus achieving the goal of lightweight automobiles.In this paper,foamed polypropylene material was prepared by low pressure structure molding process.Firstly,high melt strength polypropylene was prepared by PP/PE blending.The foaming agents azodicarbonamide and sodium bicarbonate were modified by Zn O and stearic acid respectively.The melt strength of the prepared high melt strength polypropylene and the decomposition temperature of the modified foaming agent were tested and characterized.Then,the prepared high melt strength polypropylene,modified foaming agents azodicarbonamide and sodium bicarbonate were prepared by low pressure structure injection molding process,and the weight loss rate,microstructure and mechanical properties of the foamed polypropylene were tested.The results show that the melt strength of PP/PE blends increases with the increase of PE content.In a certain range,the higher the polyethylene content,the higher the melt strength of the blends,and the melt strength value of PP/LDPE blends is higher than that of PP/HDPE blends with the same ratio.Melt strength has obvious influence on the weight loss rate of foamed polypropylene.The weight loss rate of foamed polypropylene increases with the increase of melt strength.With the increase of CaCO₃ content,the weight loss of polypropylene first increased and then decreased.When CaCO₃ content was 2 parts,the weight loss rate of foamed polypropylene was the highest.The increase of melt strength and the addition of nucleating agent will reduce the cell combination and gas overflow of foamed polypropylene,improve its cell structure,and thus improve the mechanical properties of foamed polypropylene.The weight loss rate of foamed polypropylene using azodicarbonamide as foaming agent is slightly higher than that of sodium bicarbonate,but the mechanical properties of foamed polypropylene using sodium bicarbonate as foaming agent are better than those of foamed polypropylene using azodicarbonamide as foaming agent.