The Impact of PVC and Silicone Material Properties on the Dispensing Process
Viscosity and Flowability
PVC: PVC used for dispensing is typically a paste-like resin (PVC paste), with a high viscosity (typically ranging from thousands to tens of thousands of centipoise) and poor fluidity, particularly at low temperatures. Heating or adding a diluent is necessary to adjust the fluidity, otherwise problems such as uneven dispensing and stringing can occur.
Silicone: Silicone used for dispensing is typically a two-component (A/B glue) or a one-component room-temperature vulcanizing (RTV) silicone. It offers a wider viscosity range (from low-viscosity self-leveling to high-viscosity thixotropic), offers better flow, and exhibits strong thixotropy (thinning under external force and thickening after standing). This makes dispensing easier and prevents runny, making it suitable for precise patterns or filling small gaps.
Curing Mechanism
PVC: Curing relies on heat-induced plasticization (typically baking at 150-200°C). The material is formed by solvent evaporation or resin melt cross-linking. Curing speed is significantly affected by temperature and thickness. Thick layers may require step-by-step curing to avoid air bubbles. Silicone:
Two-component silicone: Cures through a chemical reaction after mixing components A and B (e.g., condensation or addition). Curing can be performed at room temperature or accelerated by heating. The curing process is volatile-free and suitable for sealing and encapsulation applications.
Single-component silicone: Cures upon contact with moisture, with a progressively increasing cure rate from the surface toward the interior. Suitable for small-area dispensing, but with certain humidity requirements.
