Toughening Of Polypropylene And Chain Extension As Well As Flame Retardant Modification Of Polyamide

Polypropylene (PP) and polyamide (PA) are most commonly used thermoplastics with wide application in the field of civil, industry and military. In order to overcome the weaknesses of the pristine materials and further broaden the application range, we carried out the modifications of these two materials.1, Vistamaxx (VM) is a novel ethylene-propylene copolymer with high propylene content. In the research, two different VM were used to toughen polypropylene. The mechanical properties, crystallinity and microstructures of the compounds were investigated by tensile and impact tests as well as differential scanning calorimetry (DSC) and scanning electron microscopy (SEM). Results showed PP could be effectively toughened by VM. An obvious brittle-ductile transition was observed for the PP/VM 3000 compound. The crystallization temperature slightly increased, while the crystallization peak broadened and the peak area decreased. After the modification, the number of PP spherulites increased and the PP spherulite size was sharply increased.2, Ethylene-vinyl acetate rubber (EVM) is a random copolymer of ethylene and vinyl acetate (VA) with VA content of 40-80 wt%. It is a special-purposed rubber with excellent heat resistance, oil resistance, flame resistance and low temperature performance. In order to facilitate the forming and re-use of the material, PP and EVM were utilized as raw materials to prepare a thermoplastic elastomer (TPE) by dynamic vulcanization. And we studied the effects of processing conditions, the amounts of curing agent (dicumyl peroxide, DCP) and the compatibilizer (maleic anhydride grafted polypropylene, MPP) on the properties of the material (mechanical properties, anti-hot oil and anti-hot air performance, crystallinity, etc.). Results showed that when the DCP load was less than 1.5 phr, the mechanical properties , the hot air and hot oil aging-resistance became better with increasing DCP dosage. The introduction of MPP can significantly improve the compatibility of the two phases, thus improve the mechanical properties of the TPEs. In addition, we innovatively used salt of unsaturated carboxylic acid and antioxidants to modify the TPE. Results showed that when the contents were within a certain range, both additives could effectively improve the mechanical properties of the material.3, Low viscosity Polyamide 6 (PA6) was usually low molecular weight polymer with poor mechanical properties. So 2,2'-(1,3-phenylene)bis(2-oxazoline) (MPBO) , a chain extender, was used to do modification. The chain-extension behavior of MPBO was studied to evaluate its coupling effect on PA6 in an extruder. The effects of MPBO content on the mechanical properties, rheology and crystallizing behavior were investigated. Results showed that MPBO had an evident chain extension effect on PA6. The best dose of MPBO was around 2.0% at 240℃when the molecular weight of PA6 increased from 1.4×10~4 to 2.5×10~4. After the chain-extension reaction, tensile strength, elongation at break and intrinsic viscosity of the material were all improved to some extent while the melt flow index dropped gradually. Decreases of both crystallinity and crystallization temperature were observed when MPBO was introduced to the resin.4, Heat resistant polyamide, known as high temperature nylon (HTN), with excellent heat and solvent resistance as well as dimensional stability is widely applied in the electrical and electronic filed. Because the UL-94 V-0 class is a requirement for the used material, organic phosphinate OP1230, a flame retardant, was utilized to improve the flame retardance of poly(decamethylene terephthalamide) (PA10T). Results showed the introduction of OP1230 accelerated the degradation of the material and led to an increase in char mass. OP1230 could effectively improve the flame retardance of PA10T. Though the 0.8 mm samples did not pass the UL-94 test, the limiting oxygen index (LOI) of the composites increased from 23% to 45.5% when the amount of flame retardant reached 18%. As to the 1.6 mm samples, V-0 class was attained when 12% OP1230 was applied and the LOI jumped to 47% when 18% OP1230 was introduced.