1. Performance of PMMA:
PMMA is an amorphous polymer, commonly known as plexiglass (acrylic), with a density of about 1.18g/cm³, with excellent transparency and light transmittance of 92%. It is a very good optical material, with good heat resistance (thermal deformation temperature is 98 ℃). Its product has medium mechanical strength, low surface hardness, and is easily scratched by hard objects, which will leave traces and is less brittle than PS.
2. Application of PMMA:
Instrument lenses, optical products, electrical appliances, medical equipments, transparent models, decorations, sunglasses, dentures, billboards, clock panels, car taillights, windshields, etc.
In light of the coronavirus COVID-19, we are seeing a significant jump in demand for Acrylic Sheets for sneeze guards. These easy-to-assemble countertop sneeze guards are used in Convenience stores, Pharmacies, Urgent Care Centers & other public sites are using these shields to protect workers from spray and airborne spread of the virus.
3. Process characteristics of PMMA:
The processing requirements of PMMA are strict. It is very sensitive to moisture and temperature. It must be fully dried before processing. Its melt viscosity is large, and it needs to be formed at a high temperature (219 ~ 240℃) and pressure, better with a mold temperature of 65 ~ 80℃. The thermal stability of PMMA is not very good, and it will be degraded by high temperature or prolonged residence at high temperature. The screw speed should not be too large (about 60rpm is ok). The “void” phenomenon is easy to appear in the thick PMMA parts, it needs a large gate and “high material temperature, high mold temperature, slow”speed” injection conditions to process.
| 4. PMMA-Processing Conditions | |||
| Drying Temperature(℃) | 80～85 | Appr.Drying Time(hr) | 2～3 |
| Mold Temperature (℃) | 65～80 | Residual Material (mm) | 2～6 |
| Melting Temperature (℃) | 215～240 | Back Pressure (Mpa) | 13～28（Should be High） |
| Injection Pressure (Mpa) | 100～170 | Clamping Force Ton/in2 | 4 |
| Injection Speed | Low Speed | Return Material Rotating Speed(rpm) | 60～80 |
| Screw Category | Standard Screw ( a small screw can be used if a larger injection pressure is required) | ||
| Downtime Solution | Need to Use PP Material to Clean | Scraps Reuse | 0 |
| 5. PMMA-Mold Production | |||
| Appropriate Wall Thickness（mm) | The thickness is 1.5 ~ 4.0mm, but the injection molding technology of extra thick parts is different | ||
| Pouring Gate Design | Suitable or round gate, and need to use large size gate | ||
| Shrinkage | 0.4～0.7 | ||
