Polypropylene with high melt flow rate and high isotacticity prepared by phosphate‐mixed external donors

Abstract

High melt flow rate (MFR) of polypropylene can improve its processability and its high isotacticity is favor of keeping good mechanical properties of polypropylene. In this study, as a convenient and effective method, the mixture of phosphate and alkoxysilane as mixed external donors for Ziegler-Natta catalyst is used to improve MFR of polypropylene. The MFR of polypropylenes prepared by mixed external donors is three to five time higher than that prepared by dicyclopentyl dimethoxysilane (Donor-D) alone, which is attributed to broad molecular weight distribution and low molecular weight of polypropylene prepared by mixed external donors. In addition, isotacticity and lamella thickness of polypropylene prepared by mixed external donors containing triisopropyl phosphate or phenyl-phosphonic acid dipentyl ester are very close to that prepared by Donor-D, which lead to keep high thermal properties and good mechanical properties for the polypropylenes.

Improving the stability and ductility of polylactic acid via phosphite functional polysilsesquioxane

“…High molecular weight and branching can lead to a decrease in MFR. 43,44 As shown in Table 1, however, 2 wt% PSQ showed only very limited effect on MFR of chain reacted PLA due to the amino group. When phosphite was graed onto PSQ, PPSQ-PLA was a minimum of 3.7 g 10 min À1 , which indicates that PPSQ can act as an effective chain extender or crosslinking agent of PLA.…”

Polyolefin microstructural deconvolution methods: The good, the bad, and the ugly

“…This approach has been used to understand the distribution of active site types in Ziegler-Natta catalysts for propylene polymerization as a function of polymerization temperature and time, type of cocatalyst and electron donor, copolymerizations with other α-olefins, and catalyst synthesis conditions. [51][52][53][54][55][56][57][58][59][60][61][62][63][64][65][66] Similar deconvolution studies were used to understand the effect of polymerization conditions and catalyst formulations for the polymerization of ethylene and α-olefins with Ziegler-Natta [67][68][69][70][71][72][73][74][75][76][77][78][79][80][81] and Phillips/chromium catalysts. [82][83][84] Other studies used MWD deconvolution to identify active site populations for the polymerization of 1-octene, [85] 1-hexene, [86][87][88][89] and 1-butene [90,91] with Ziegler-Natta catalysts.…”

Status and future development suggestions for China’spolyolefin industry

“…聚烯烃国家工程研究中心，我国的Ziegler-Natta催化剂部分技术达到国际领先 [29,30] 废旧聚烯烃资源化利用技术是决定聚烯烃产业未来的颠覆性技术 [35,36] 。在国家"双碳" 目标大背景下，面对日益严重的塑料污染，可预见在不久的将来整个塑料产业将进入"谁生 产，谁回收"时代。届时，如仍无科学有效的资源化利用技术，聚烯烃产业将无法实现可持 续发展。目前，熔融再加工的物理法回收技术是最常见且唯一被广泛采用的资源化利用技术 方案。由于不同塑料具有不相容性，物理法回收技术需重点研究能实现混合塑料相容的多效 相容剂技术 [37] 。然而，物理法回收技术有其局限性，温度敏感塑料、复合材料、和升温不熔 融流动的塑料(如热固性塑料)都无法进行物理回收；并且物理回收通常会使材料性能下降，…”