聚丙烯单聚合物复合材料的嵌件式注射成型方法及其机理研究

Polypropylene single-polymer-composite (PP SPC), made by integrating PP fibers with a matrix of PP, has low density, improved interfatial compatibility and enhanced recyclability. Development of injection molding technology is of great significance to realize the industrialization of PP SPC. PP could be ‘undercooled’ to a temperature well below the polymer melting temperature while crystallization is largely absent. Based on the undercooling property, the insert injection molding method for PP SPC has been proposed. The PP fiber reinforcement is fixed into the mold cavity as an insert, then the PP matrix is injected into the cavity to coat and permeate the reinforcement, the reinforcement will not be melted because of undercooling when the matrix contacts with the cavity wall and insert. The proposed research contents includes: the undercooling property of PP matrix and the coating and permeating process of PP matrix, the processing condition for PP SPC insert injection molding, mechanical properties and microstructures of PP SPC. The specific research objectives are: enlarge the difference between the melting temperatures of matrix and reinforcement, enhance the permeating quality of matrix in insert injection molding, realize the production of PP SPC by injection molding, obtain the influence law of physical parameters, equipment structure and processing conditions, improve the interface bonding performance and mechanical properties of PP SPC. Theoretical basis and technical support will be provided for injection molding of SPC parts. The research achievements will be helpful to promote the development and application for SPC and its processing techniques.

聚丙烯单聚合物复合材料（PP SPC）是基体和增强体同为聚丙烯（PP）的复合材料，具有密度小、界面粘结性高、易回收等优点。研究掌握注射成型技术以实现PP SPC产业化具有重要意义。PP具有在熔点以下未结晶而仍保持流动的“过冷”特性，本项目基于此性质提出了PP SPC嵌件式注射成型方法：将PP纤维增强体嵌入模腔中，注射基体填充型腔并包覆渗透增强体，基体在与模腔和嵌件接触过程中存在过冷而不会使增强体熔融。本项目主要研究PP基体的过冷特性及其包覆渗透增强体的过程规律，研究PP SPC嵌件式注射成型工艺条件及制品的力学性能与微观结构。着重解决基体和增强体熔融温度差扩大的难点，提高嵌件式注射过程中基体的渗透性能，实现PP SPC的注射成型；探明物性参数、设备结构、工艺条件的影响规律，提高PP SPC的界面粘结性能及力学性能。为注射成型SPC提供理论依据和技术支持，推动SPC及其制备技术的发展。

聚丙烯（PP）单聚合物复合材料（SPC）是基体和增强体同为PP的复合材料，具有密度小、界面粘结性高、易回收等优点。现有制备工艺受限于热压法，存在成型周期长等缺点，研究掌握注射成型技术实现PP SPC产业化具有重要意义。控制基体和增强体间的温度/熔融差是制备SPC的关键，传统注射成型工艺会使增强体熔融而失去增强效果。PP具有在熔点以下未结晶而仍保持流动的“过冷”特性，本项目基于此性质提出了嵌件式注射成型方法：将纤维增强体嵌入模腔中，注射基体填充型腔并包覆渗透增强体，基体在与模腔和嵌件接触过程中存在过冷而不会使增强体熔融。本项目主要研究了PP基体的过冷特性及其包覆渗透增强体的过程规律，通过模拟实验和数值仿真及工艺实验结合的方法重点研究了温度对PP基体包覆渗透增强体的过程，掌握了关键参数温度的影响规律；着重解决了基体和增强体熔融温度差扩大的难点，研究发现嵌件式注射成型方法可实现40℃的较宽加工温度窗口；研究得到了提高基体的渗透性能的工艺条件，研究了温度、压力、时间三个关键参数的交互影响规律，研究发现温度是最关键的控制参数，温度的选择需根据型腔结构确定，可通过预先模拟仿真确定合适的加工温度，在温度确定后，压力和时间可相互调配使用；研究了增强体嵌件嵌入位置、嵌件结构、增强体材料种类的影响，分别制备了不同结构（中间嵌和两边嵌）的PP SPC，制备了连续纤维束单向增强PP SPC和纤维布增强PP SPC，制备了单组分PP SPC和双组分PP SPC；制备的纤维布增强单组分PP SPC的纤维含量达36wt%，拉伸强度可达70MPa，为未增强PP的2.3倍，此强度也超过了普通短/长玻纤增强PP复合材料；而制备得到的双组份PP SPC的拉伸强度达到了120MPa，与直接热压纤维法和膜层热压法制备得到的同类材料的拉伸性能相当，其较优工艺条件为：注射温度260℃、注射压力96.6MPa、注射速率0.18m/s、保压时间60s；考察了PP SPC的界面粘结性能，其剥离力平均值最高达19.44 N/cm，超出了直接热压纤维法和膜层热压法制备得到的同类材料的撕裂性能。通过DSC、XRD、SEM等表征手段全面系统分析了制备样品，探明了物性参数、设备结构、工艺条件的影响规律，为注射成型SPC提供了理论依据和技术支持；同时推广实现了聚乙烯（PE）SPC的注射成型。