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Molecular origin of the foam structure in model linear and comb polystyrenes: I. Cell density
Polymer ( IF 4.6 ) Pub Date : 2020-03-09 , DOI: 10.1016/j.polymer.2020.122351
Mahdi Abbasi , Lorenz Faust , Manfred Wilhelm

The effect of the molecular architecture of anionically synthesized linear and comb atactic polystyrenes (PS), as well as lab-scale emulsion polymerized PS and commercial PS on the cell density of foam (number of cells per unit volume of neat polymer) was investigated using CO2 as foaming agent in a batch foaming setup. The effects of molecular weight, Mw, dispersity (Ð), low molecular weight components, i.e. oligomers and residual surfactant, and the number of long chain branches per molecule, Nbr, in a series of comb-PS with the same entangled backbone, Mw,bb ≈ 290 kg/mol, Zbb ≈ 20 entanglements, and similar branches, Mw,br ≈ 44 kg/mol, Zbr ≈ 3 entanglements, but different numbers of branches, 3 ≤ Nbr ≤ 190, on the cell density were investigated. Specimens for foaming have been prepared with three different methods, which resulted in non-purified, treated, and purified samples. Well-purified samples produced foams with cell density above 109 cell/cm3, while foams out of the non-purified PS had one to three orders of magnitude lower cell density. However, artificial addition of 6 wt% oligomer PS or 3 wt% surfactant to the purified samples did not reduce the cell density significantly. Treated samples prepared by only dissolving the PS in a solvent followed by removing the solvent, produced a foam with slightly lower cell density, ∼5 × 108 cell/cm3, than the purified PS. Lower cell density in non-purified PS was supposed to be related to the formation of a continuous ionic thin film layer (e.g. surfactant) rather than only the presence of low molecular weight components as impurity in the polymer. In the absence of such low molecular weight components, other molecular parameters, i.e. Mw, Ð, and Nbr in these series of comb-PS had surprisingly no distinct effect on the cell density.



中文翻译:

模型线性和梳状聚苯乙烯中泡沫结构的分子起源:I.孔密度

研究了阴离子合成的线性和梳状无规聚苯乙烯(PS)的分子结构,以及实验室规模的乳液聚合的PS和商用PS对泡沫的孔密度(每单位体积的纯聚合物孔数)的影响。在分批发泡设置中,CO 2作为发泡剂。分子量,的效果中号瓦特,分散度(d),低分子量成分,即低聚物和残留表面活性剂,和每分子的长链支链的数量Ñ BR,在一系列梳-PS的具有相同的缠绕骨架,M w,bb≈290  kg / mol,Z bb≈20纠缠和类似的分支,中号瓦特,BR  ≈44公斤/摩尔,ž BR ≈3个缠结,但不同数量分支的,3≤ Ñ BR ≤190,对细胞密度进行了调查。用三种不同的方法制备了用于发泡的样品,这产生了未纯化,已处理和已纯化的样品。经过充分纯化的样品所产生的泡沫的泡孔密度高于10 9 孔/ cm 3,而未纯化PS中的泡沫则使泡孔密度降低了1-3个数量级。但是,向纯化的样品中人工添加6 wt%的低聚物PS或3 wt%的表面活性剂不会显着降低细胞密度。通过仅将PS溶解在溶剂中,然后除去溶剂而制备的处理样品,产生的泡沫的泡孔密度比纯化的PS稍低,约5×10 8 孔/ cm 3。认为未纯化的PS中较低的细胞密度与连续的离子薄膜层(例如表面活性剂)的形成有关,而不仅与低分子量组分作为聚合物中杂质的存在有关。在没有这种低分子量成分的情况下,其他分子参数(即M wdÑ BR在这些系列梳-PS的对细胞密度出奇没有明显的影响。

更新日期:2020-03-09
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