Spray-dried detergent granules have a complex and multi-scale structure, in which submicron sized crystals of inorganic salts along with multi-lamellar stacks of surfactant molecules are dispersed within a matrix phase. In this study, two model formulations based on sodium linear alkylbenzene sulphonate (NaLAS) and sodium sulphate were used to investigate the molecular structure of stacked lamellae. The parameters of lamellar d -spacing, bilayer thickness (d HH) and water layer thickness (d W) were determined using small-angle X-ray scattering. Four sets of lamellae were detected in nil-silicate detergent powders conditioned at 33% RH (relative humidity). The exposure of these samples to a higher RH level (75%) resulted in a reduced number of coexisting lamellar phases by two. This was accompanied by an increase in lamellar d -spacings and a considerable reduction in bilayer thicknesses (d HH). The reduction in number of sets of lamellae was explained by an increase in the fluidity of the lamellar phases and disappearance of water-poor solid polymorphs. This was consistent with the results of FTIR for nil-silicate samples, indicating an increase in the conformational disorder of the alkyl chains at a higher RH value. Interestingly, in the presence of sodium silicate the lamellar phases display a greater degree of swelling at a relatively low RH value (33% RH) as compared with those in the absence of sodium silicate. Nonetheless, the thickness of water layer was found to slightly decrease at a higher RH (75%), which was attributed to the moisture-induced glass transition and kosmotropic effect of sodium silicates.

喷雾干燥的洗涤剂颗粒具有复杂的多尺度结构，其中无机盐的亚微米级晶体与表面活性剂分子的多层堆叠在一起分散在基质相中。在这项研究中，基于线性烷基苯磺酸钠（NaLAS）和硫酸钠的两种模型配方被用来研究堆叠薄片的分子结构。使用小角度X射线散射确定层状d间距，双层厚度（d HH）和水层厚度（d W）的参数。在条件为33％RH（相对湿度）的无硅酸盐洗涤剂粉末中检测到四组薄片。这些样品暴露于较高的RH水平（75％）导致共存的层状相数量减少了两个。这伴随着层状d间距的增加和双层厚度（d HH）的显着减小。片层数减少的原因是层状相的流动性增加和贫水的固体多晶型物消失。这与零硅酸盐样品的FTIR结果一致，表明在较高的RH值下烷基链的构象无序性增加。有趣的是，与不存在硅酸钠的情况相比，在存在硅酸钠的情况下，层状相在相对较低的RH值（33％RH）下显示出更大的溶胀度。但是，在较高的相对湿度（75％）下，发现水层的厚度略有减小，这归因于湿气引起的玻璃化转变和硅酸钠的共溶作用。