In situ suspension polymerization of vinyl chloride/3-(trimethoxysilyl) propyl methacrylate (MPTMS)-intercalated Mg-Al-hydroxide layered double hydroxide: I. Grain properties

Abstract

Suspension polymerization of vinyl chloride (VCM) was carried out in the presence of particle of both pristine Mg-Al layered double hydroxide (LDH) and LDH intercalated by 3-(trimethoxysilyl) propyl methacrylate (MPTMS-LDH) in a pilot-scale reactor. The experiments were conducted at different concentrations of each type of the particles (0, 1, 3, 5, 7 wt. % of VCM). The pure LDH and MPTMS-intercalated LDHs were used as co-monomer for fabrication of LDH or MPTMS-LDH/PVC nanocomposites; the particles were directly pre-dispersed in monomer phase before dispersing in the continuous aqueous phase and starting the suspension polymerization. The basal spacing obtained from the X-ray powder diffraction (XRD) showed that the reaction between VCM and MPTMS-LDH was effective, with a further intercalation of PVC chains in the interlayer space. The molecular characterization showed that the polydispersity index (PDI) and molecular weight of the poly (vinyl chloride) (PVC) resin do not change in the presence of the pristine LDH. The MPTMS-LDH, however, decrease the molecular weight and increase the PDI of PVC resin. Also, from the morphological point of view, scanning electron microscopy (SEM) showed that PVC grains produced with high particles content had a smoother surface with more regular shape. Moreover the incorporation of nanoparticles in the VCM suspension polymerization, made particles with a narrower size distribution. The LDH results in the formation of smaller primary particles with higher internal porosity whereas, the larger primary particles with lower internal porosity in the presence of modified particles was observed.

In situ suspension polymerization of vinyl chloride/3-(trimethoxysilyl) propyl methacrylate (MPTMS) intercalated Mg-Al-layered double hydroxide: II. Morphological, thermal properties and diffusion behavior

“…Modified or unmodified LDH contained PVC grains prepared by the in-situ polymerization process according to our earlier work. 19 The recipes that are used for PVC compound preparations are categorized in Table 1. All materials were purchased from Baerlocher (Germany) and used without further purification.…”

“…It should be noted that the polymerization procedure and how to achieve LDH contents of 5 wt% were presented in detail in earlier work. 19 In our previous work, the surface characteristic of LDH particles before and after the modification with MPTMS was considered, and in addition, the content of particles on molecular properties, including K-value, molecular weight distribution (MWD), and particle morphology such as particle internal structure, primary particles size, and particle size distribution were investigated on PVC grains. The present work studied and evaluated the impact of LDH nanoparticles on thermal stability and fusion.…”

“…Using the Brabender ® plastograph method and differential scanning calorimetry (DSC), the degree of fusion of the prepared samples was compared. 19…”

Propyl methacrylate(MPTMS)-intercalatedMg-Al-layered double hydroxide: II.Morphological, thermal propertiesand diffusion behavior

“…This difference in stability can be originated from the decrease in melt viscosity of the PVC/LDH blend, which is a result of a rise in the temperature of fusion as shown in table 3. [22] Highly ordered and closely packed structures of grains (as described in detail in our previous work [19]) avoid fast fusion between the grains and primary particles; as a result, the friction forces and viscous shear heat caused by it are low, which makes a growth in fusion temperature. As a result, the thermal stability of pure PVC will decrease with increasing fusion temperature.…”

“…Using the Brabender ® plastograph method and differential scanning calorimetry (DSC), the degree of fusion of the prepared samples was compared. [19] 2 Exprimental…”