Why PMA Is the Additive of Choice for Low-Temperature Hydraulic Fluids

Low-temperature hydraulic Fluid is a specialized fluid formulated for reliable operation in extreme cold. Its core function is to maintain a balance between excellent fluidity and low-temperature kinematic viscosity, ensuring systems can start and operate normally in the cold. These performance characteristics are primarily influenced by the base oil, viscosity index improvers (VII), and pour point depressants (PPD), making these oils suitable for cold-weather applications such as construction machinery, mining equipment, and ship deck machinery.

Advantages of PMA VIIs in Low-Temperature Hydraulic Fluids

PMA (Polymethacrylate) is a primary lubricant additive whose chief functions are to enhance the viscosity index, provide excellent shear stability, and offer thickening effects. It ensures that the oil maintains sufficient viscosity to form a protective oil film at high temperatures, while simultaneously preserving excellent fluidity at low temperatures. This dual-action ensures effective lubrication for engines and equipment across a wide temperature range, thereby extending their service life. Beyond VI improvement, specific PMA types also double as pour point depressants for reliable cold-start performance. It is widely used in automotive engine oils, industrial gear oils, hydraulic oils, and automatic transmission fluids (ATF).

Advantages of PMA in Low-Temperature Hydraulic Fluids

1. Excellent Low-Temperature Fluidity and Viscosity-Temperature Properties

The low-temperature performance of a Viscosity Index Improver (VII) encompasses two aspects: low-temperature startability and low-temperature pumpability. PMA Viscosity Index Improvers(VIIs) enhance the viscosity-temperature profile and fluidity of the oil, ensuring viscosity does not become excessive in cold conditions. This guarantees excellent low-temperature startability, reduces mechanical loss, and prevents hydraulic system blockages or cavitation. Conversely, as temperatures rise, the viscosity does not drop excessively, noticeable improving the system's volumetric efficiency, reducing internal leakage, and preventing wear caused by overheated hydraulic oil.

E.g.: In engine operation, 50% of cylinder wear occurs during the startup phase.

2. Pour Point Depletion

PMA crystallizes at certain temperatures, forming a defined, rigid comb-like structure. It can absorb small amounts of paraffin wax as they begin to precipitate from the oil, transforming them into micro-crystalline wax sites. This prevents the wax from forming large, interlocking crystalline structures, thereby effectively lowering the pour point.

3. Superior Shear Stability (SSI)

Shear stability is a critical performance metric for VIIs, and PMA Viscosity Modifier exhibit outstanding shear stability within oil formulations. At low temperatures, PMA molecular chains contract into spherical shapes, resulting in minimal internal friction and low kinematic viscosity. This prevents an excessive drop in lubricant viscosity during operation, ensuring sufficient oil film thickness and continuous, effective lubrication. Due to its minimal viscosity fluctuation, the performance degradation of the lubricant is slow throughout its service cycle, effectively extending its lifespan.

Example: In gear oils, the Shear Stability Index (SSI) values are: KRL (20 hours): 48%; Diesel Injector (30 cycles): 3.9%.

4. Thickening Capability

While the intrinsic viscosity of the base oil decreases at high temperatures, PMA possesses a strong thickening capability to compensate. It not only thickens the base oil but also improves the overall viscosity-temperature characteristics, ensuring the oil maintains both high-temperature lubricity and low-temperature fluidity.

Chorus T602HB Product Parameters
Shear Stability Index (SSI): When 10% T602HB is added to a specific Group II base oil(with an original pour point of -18℃), the measured SSI is 49.

Viscosity Increase (at 100°C): When 10% T602HB is added to the same Group II base oil, the measured viscosity increase at 100°C is 18.9 mm²/s (cSt).

Pour Point Depressant (PPD) Effect: A formulation of 1.5% T602HB and 98.5% Group II base oil (original pour point -18°C) achieves a markedly lowered pour point of -43°C.

Chorus offers a wide range of PMA Viscosity Index Improvers (VIIs) suitable for various applications, including engine oils, hydraulic oils, and gear oils. In lubricant formulations, PMA VIIs function as both pour point depressants (PPD) and thickening agents. In addition to PMA, we provide other types of viscosity index improvers, such as OCP (Olefin Copolymer) and PIB (Polyisobutylene).