Polystyrene
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Polystyrene is a clear non-crystalline plastic material which is brittle. Improvement to its impact strength can be made by compounding with more rubbery polymers. These high-impact grades can be extruded or molded into products for use inside buildings.
Physical Properties
Physical properties of solid polystyrene
| Density (kg/m³) | 1050 |
| Melting point (K) | 510 |
| Specific heat capacity (J/kg K) | 1300 |
| Coefficient of thermal expansion (/mm.mK) | 0.070 |
| Thermal conductivity (W/mK) | 0.08 |
| Tensile strength (MPa) | 50 |
| Young’s Modulus (MPa) | 3100 |
Classifications
| PS | a polystyrene foam produced by either an expansion process or an extrusion process |
| EPS | a polystyrene foam manufactured by moulding blocks boards or shapes from expandable beads, sometimes referred to as ‘bead board’ |
| XPS | an extruded polystyrene foam manufactured into boards. |
Physical properties of EPS (Method of tests are referred to BS 3837: Part 1)
| Physical properties | Grade | ||||
| SD | HD | EHD | UHD | ISD | |
| Maximum thermal conductivity at 10ºC (W/mK) | 0.038 | 0.035 | 0.033 | 0.033 | 0.041 |
| Compressive strength or stress at 10% strain (kPa)
Minimum Maximum |
70 – |
110 – |
150 – |
190 – |
25 45 |
| Minimum cross breaking strength (kPa) | 140 | 170 | 205 | 275 | NA |
| Dimensional stability at 80ºC
Maximum % linear change |
1.0 |
1.0 |
1.0 |
1.0 |
1.0 |
| Maximum water vapour permeability at 38ºC (ng/Pa.s.m) | 6.9 | 5.0 | 4.2 | 4.2 | 10.0 |
| Burning characteristics, extend burnt (mm)
type N type A |
>=125 <125 |
||||
| Safe working load at 1% strain (kPa) | 21 | 45 | 70 | 100 | 10 |
Physical properties of XPS (Method of tests are referred to BS 3837: Part 2)
| Physical properties | Skinned | Planned | |||||
| E1 | E2 | E3 | E4 | E5 | E6 | E7 | |
| Compressive stress (kPa)(min.) | 100 | 150 | 200 | 300 | 350 | 100 | 250 |
| Water vapour permeability (ng/Pa.s.m)(max) | 3.2 | 2.7 | 2.4 | 2.1 | 1.9 | 3.8 | 2.4 |
| Water absorption by immersion (max.% vol) | 1 | 1 | 1 | 1 | 1 | 2 | 2 |
| Water absorption by diffusion (max.% vol) | – | 4 | 4 | 3 | 3 | – | – |
| Thermal conductivity at 10ºC (W/mK)(max) | 0.032 | 0.030 | 0.030 | 0.028 | 0.028 | 0.035 | 0.030 |
| Dimensional stability for 2 days at 70ºC (change %)(max) | 5 | 5 | 5 | 5 | 5 | 5 | 5 |
| Compressive creep at 40 kPa and 70ºC for 7 days (change %)(max) | – | – | 5 | 5 | 5 | – | 5 |
| Burning characteristics of small specimens | Maximum extent of burning 125mm | ||||||