取代基对硫代磷酰胺酯摩擦磨损的影响

INFLUENCE OF SUBSTITUENTS ON FRICTION AND WEAR OF THIOPHOSPHORIC AMIDATES

采用四球机和SRV试验机研究了3类不同结构的硫代磷酰胺酯(TPA)的抗磨有效性,包括硫代磷酰单胺酯(TPMA)、硫代磷酰双胺酯(TPDA)和二硫代磷酰单胺酯(DPMA)。结果表明,TPA通常有较好的抗磨性和承载能力。其润滑性取决于酯基和胺基的结构、取代基的电负性和摩擦条件。在单向滑动和往复运动中性能都较佳的是硫脲基上连接有强烈吸电子作用的取代基的O-乙基、N-烷基和硫脲基单硫代磷酰胺酯(EAPTUT)。某些TPA的性能优于ZDTP、MoDTP、硫代磷酸酯、膦酸次膦酸胺盐、T305和T307等商品化的抗磨剂。1个TPA分子中同时含有S、P、N基团,分子内相互牵制作用使每个功能团都不会过度活泼,摩擦过程中的腐蚀磨损和磨粒磨损很易平衡,总磨损最小。SRV试验中每次往复运动磨出新鲜金属表面仅费时百分之几秒,而活性不够的抗磨剂可能无法及时生成新表面保护膜。

Three types of thiophosphoric amides（TPA）, i. e. thiophosphoric monoamide（TPMA）, thiophosphoric diamide（TPDA）, and dithiophosphoric monoamide（DPMA） had been tested on a Four Ball machine and a SRV tester for their relative antiwear effectiveness. The results indicated that three types of TPA, in general, had fairly good load carrying capacity and antiwear performance. The lubricity of these compounds was found to be dependent upon the structure of both the ester groups and the amine groups, the electronegativity of substituents, as well as rubbing conditions. The best performance in both unidirectional sliding and reciprocating sliding was observed for those O-ethyl N-alkyl phosphoro（thioureido）thioates （EAPTUT） in which a strong electron-withdrawing substituent was linking to the thioureido group. The superiority of some substituted EAPTUT and dialkyl dithiophosphoramidates （DADTPA） to many commercially available antiwear additives, including ZDDP, MoDTP, thiophosphates, amine salt of phosphonic acids and phosphinic acids, T305 and T307, was probably related to the intramolecular synergism of substituents, the effect of electron-withdrawing substituent on the cleavage of the P--N bond, as well as the high soften point of SPN type polymer films formed in rubbing surface. Functional groups containing sulphur, phosphorus and nitrogen on a single TPA molecule could control the molecule interaction with the surface without making any one bond too active, thus balance adhesive wear and corrosive wear and result in minimum total wear. In SRV test a fresh metal surface was generated after every cycle, which spent only a few hundredths seconds and could not allow low activity additives to form a protective surface film in time.