| Isotactic Polypropylene (iPP) is a widely used thermoplastic plastics, and it has good mechanical properties, low price and easy processing. With the development of world economy, the proportion of general polypropylene applied in automobile, household appliances etc. is increasing year by year.The disadvantages of generalpolypropylene are low bending modulus, poor anti erosion ability and poor heat resistance. Meanwhile, high rigidity and thermal distortion temperature of polypropylene can be increased by 10% than the general polypropylene, which can be widely used in high temperature surroundings and fields require high strength and high rigidity. It means that demand of consumers about high rigidity, heat resistance polypropylene is increasing, so the development of high rigidity and heat resistant polypropylene is meaningful and has further prospects. Among them, adding nucleating agent or inorganic particle is an effective method to improve the properties of polypropylene. In addition, based on a small amount of nucleating agent addition,addingtalc to control mechanical and thermal properties of polypropylene will be the novel method to produce high rigidity, high temperature resistance polypropylene.Therefore, it is of great significance to further study the effect of talc and nucleating agents on the rigidity and heat resistance of polypropylene composites.Firstly, the synergistic effect between sodium phosphate nucleating agent NA-40 and talc on polypropylene composites has been studied. The results showed that talc and nucleating agent had good synergistic effect, so the polypropylene had excellent mechanical properties and good heat resistance, especially in the low dosage of talc cooperating with a small amount of nucleating agent. They could effectively improve the performance of the polypropylene composite. When adding 10 wt% talc and 0.2 wt% nucleating agents, the flexural modulus of polypropylene reaches 2316.0 MPa, the flexural strength reaches 54.3 MPa, the tensile strength reaches 39.4 MPa, the impact strength reaches 49.1 J/m, and the heat distortion temperature reaches 120.0 ℃. Compared with the blank polypropylene, the properties increased by 63%, 28%,11% ,29% and 35%, respectively. In addition, the melt flow index of polypropylene was 3.7g/10min and the crystallization temperature was 131.0 ℃. It showed that the addition of talc did not adversely affect the processing performance of PP composite system.Then, surface modification were conducted on the talc used above.Modifying agents such as y-amino propyl triethoxy silane (KH550) and n-octyl triethoxy silane (OTES) were applied and the effects of silane coupling agent with different chain length on talc and the mechanical properties of polypropylene were studied. It is found that OTES with long alkyl chain had better performance. And NA-40/talc-polypropylene had excellent mechanical properties and good heat resistance, but the modification effects between two kinds of silane coupling agents is not obvious. For consideration for cost-effective, KH550 was chosen as a relatively low price of modifying agents. The surface modification of talc by adding lwt% KH550 could improve the mechanical properties, heat resistance and crystalline properties of NA-40/talc-polypropylene. The flexural modulus reached 2400.0 MPa, the flexural strength reaches 57.1 MPa, the tensile strength reaches 39.1 MPa, the impact strength reaches 57.0J/m, heat distortion temperature reaches 121.0 ℃ and crytallization temperature was 134.3℃, increased by 69%,34%,10%, 48%,36% and 9%, respectively.Then, annealing treatment was conducted on the polypropylene adding 10 wt% talc and 0.2 wt% nucleating agents. The effects of annealing temperature, annealing time on properties of polypropylene were studied, such as mechanical properties and crystal structure changes. It was found that annealing could indeed improve the mechanical properties and obtain more excellent heat resistance. And that under the annealing temperature of 120.0 ℃ forl hour, flexural modulus and flexural strength of polypropylene can amazingly reach 2389.0 MPa and 60.7 MPa, as tensile strength was 38.1 MPa, the impact strength was 78.1J/m and heat distortion temperature was 129.0 ℃.At last, the annealing temperature was selected as 120℃. Annealing treatment was conducted on the NA-40/modified talc-polypropylene composites. It was found that after annealing, the properties improved differently. Expecially when annealing for 1 hour, the flexural modulus was up to 2520.0 MPa, the flexural strength was up to 61.3MPa, the tensile strength was up to 39.0MPa, the impact strength was up to 79.9J/m and the heat distortion temperature reached 130.0 ℃. Obviously, by this method, a high performance polypropylene was prepared. |
