Melt Intercalation of PMMA into Organically-Modified Layered Silicate
- PDF / 396,366 Bytes
- 6 Pages / 420.48 x 639 pts Page_size
- 95 Downloads / 222 Views
137
Mat. Res. Soc. Symp. Proc. Vol. 576 ©1999 Materials Research Society
EXPERIMENT Materials The starting materials included an organically-modified bentonite: tetraallkyl ditallow ammonium bentonite (1334), which had been made from bentonite by cation exchange and is a commercial material from Rheox in USA and was used as received. The polymers were mainly poly(methyl methacrylate), PMMA (Scientific Polymer Products, Inc., USA), of different molecular weights and tacticities with poly(phenyl methacrylate) (PPMA) included as a comparison with different structure. The polymers are shown in detail in Table I. Table I. The Molecular Weights and Tgs of Methacrylate Polymers Material Notation Mn Mw Poly-dispersity DSC Tg
.(C)
a-P• A .. #424 7,580 13,781 i-PMMA #689 40,887 79,512 a-PMMA #037-A 14,266 30,845 s-PMIMA #908 36,170 38,373 a-PMMA JX 42,913 83,243 a-PMMA AY 23,282 80,213 a-PMMA PX 190,640 458,114 a-PPMA #227 80,640 165,159 a-: atactic; i-: isotactic; s-: syndiotactic.
1.81 1.95 2.16 1.06 1.94 3.44 2.40 2.05
93.5 45.5 116.0 128.8 110.6 108.2 119.5 120.8
Intercalation Nanocomposites of PMMA and B34 system were synthesized via melt intercalation. The starting powders with particular weight ratios of polymer-to-silicate were mechanically mixed using an agate mortar and pestle, and then formed into pellets using hydraulic pressure at 70MPa. The pellets were annealed in an electric furnace under vacuum at selected temperature for more than 12 hours. The selected heating temperature for PMMA #424 (Tg - 93°C) was 210 0 C, for PMMA #689 (Tg - 45QC) was 160'C and for the other PMMA or PPMA samples in Table I was between 230'C and 250'C. Characterization and Experimental Methodology The properties and structural characteristics of raw materials and intercalated hybrids were identified by several techniques. X-ray diffraction (XRD) patterns on powder samples were gained on a Rigaku-Geigerflex X-ray diffractometer using Ni filtered Cu Kct radiation at a scanning speed of 1°/min, and a step of 0.05'. Fourier transform-infrared (FTIR) spectra were collected using a Perkin Elmer 1600 from 400cm-1 to 4000cmnl with a nominal resolution of 4 cm 1 . For each spectrum, 64 runs were collected and averaged. The specimens were made by adding 1 wt % of the sample powder to KBr powder and pressed into a disc of 13 nun in diameter and 1-2 mm thick under vacuum. Thermogravimetric analysis (TGA) was performed on a SETARAM TG-DTA 92 at a heating rate of 10°C/min from 50'C to 1000°C under an air or nitrogen flow. Differential scanning calorimetry (DSC) data were obtained on a Perkin Elmer
138
differential scanning calorimeter DSC 7. Samples, approximately 10 mg, were loaded into an aluminum crucible and both the sample chamber and the reference were heated at 10°C/min. RESULTS AND DISCUSSION
XRD Fig. 1 shows XRD patterns of different mixtures of B34 and PNMMA or PPMA before and after heating. PMMA and PPMA are amorphous materials, and thus show no reflection peak in the XRD spectrum other than, perhaps, a broad underlying hump.
Data Loading...
