摘要
用单螺杆挤出机制备了马来酸酐-苯乙烯(MAH-St)多单体熔融接枝高密度聚乙烯(HDPE)体系,研究发现添加St共同接枝,可以显著提高接枝物的接枝率.随着St的增加,接枝率先增大后有所降低.当两种单体物质的量比约为1∶1时,接枝物的接枝率最高,此时接枝物的熔体流动速率(MFR)最小.即MAH接枝率越高,接枝物的MFR越低,说明接枝链的生成增加了分子间的缠结,提高了黏度.力学性能测试结果表明,在马来酸酐接枝时添加少量St制备的接枝物,其拉伸强度和冲击强度均优于纯HDPE.此外,对反应机理也进行了详细探讨,针对不同共单体添加量情况下的接枝反应进行了系统分析.在接枝体系中添加的少量St可以与MAH相互作用和共聚合生成SMA共聚物,该共聚物对PE的接枝提高了MAH的接枝率;当St用量超过MAH时,St会优先接枝到PE主链上,对SMA的接枝有所阻碍,使得MAH的接枝率有所降低,MFR略有升高.由于多单体体系接枝效率的提高,PE的交联得到良好抑制,几乎没有明显的凝胶生成.
Free radical melt-grafting of the multi-monomer system of maleic anhydride（MAH） /styrene（St） onto high density polyethylene（HDPE） prepared by a single-screw extruder was studied.It was found that the addition of St monomer could significantly improve the MAH grafting level of the grafted HDPE.With increasing the St concentration,the graft degree of MAH first increased and then decreased a little.The maximum MAH grafting degree and the minimum melt flow rate were obtained when the molar ratio of MAH to St was approximately 1∶ 1.The higher the graft degreet,he smaller MFR value was,suggesting that the grafted PE chains induced intermolecular entanglements.The mechanical properties of the grafted polymer with the addition of small portions of St monomer were better than those of the neat HDPE in this case.The mechanism of the multi-monomer melt grafting HDPE system was also discussed.It was proposed that MAH and St interacted and copolymerized with each other in the melt grafting system.The grafting of St-MAH copolymer（SMA） onto HDPE greatly increased the grafting degree of the grafted HDPE.When the amount of St is larger than MAH,St would be first grafted onto the PE backbonei,nhibiting the grafting of SMA.Besidest,he cross-linking of PE was well depressed due to the increase of graft degree in the multi-monomer melt grafting systems.And no obvious gel was obseved in the reflux process.
出处
《高分子学报》
SCIE
CAS
CSCD
北大核心
2011年第4期347-353,共7页
Acta Polymerica Sinica
关键词
高密度聚乙烯
熔融接枝
多单体
接枝机理
High density polyethylene
Melt grafting
Multi-monomer
Grafting mechanism
