PLM-9892 Low Shrinkage & Low Profile Additive (LSA/LPA) for SMC/BMC
POLEMA's PLM-9892 Low-Shrinkage Additive (LSA) and Low Profile Additive (LPA) is a highly efficient unsaturated polyester resin additive designed for advanced SMC, BMC, and molding resins. Operating through a microscopic phase separation mechanism, this powerful anti-shrinkage additive effectively compensates for resin polymerization shrinkage, guaranteeing zero dimensional deformation and a flawlessly smooth, Class-A surface finish. It is indispensable for manufacturing high-precision automotive components, electrical enclosures, and premium sanitary ware.
The PLM-9892 Low Profile Additive is engineered to exhibit exceptional compatibility with various molding resins, glass fibers, and inorganic fillers, entirely without negatively impacting the system's curing speed or overall reactivity.
By incorporating PLM-9892 into your composite formulation, post-molding products achieve remarkable dimensional accuracy (acting as a true zero shrinkage resin additive) and structural consistency. It completely eliminates common molding defects such as sink marks, ripples, or pinholes, making it a highly sought-after Class A surface additive for SMC. This advanced additive is specifically formulated to meet the demanding aesthetic and precision standards of automotive body panels, electrical/electronic enclosures, sanitary ware, and precision structural parts.
Core Performance Advantages
High Efficiency Shrinkage Control
Acts as a robust shrinkage control agent for BMC and SMC, effectively preventing deformation, warping, and cracking at the source.
Class-A Surface Finish
Eliminates sink marks, ripples, and depressions, resulting in Class-A product surfaces that are flat, smooth, and highly glossy.
High Dimensional Precision
Ensures stable molded dimensions with extremely tight tolerances, delivering excellent consistency in mass production.
Strong System Compatibility
Integrates seamlessly with SMC, BMC, and various thermoset composite additives without compromising mechanical strength.
Product Specifications
| Properties | Range | Unit | Test Standard |
|---|
| Appearance | Light yellow, slightly hazy | — | TM 2265 |
| Viscosity (23℃) | 140–170 | mPa·s | TM 2013 |
| Acid Value | 4–8 | mgKOH/g | TM 2401 |
| Solid Content | 38–45 | % | TM 2033 |
Liquid Resin Properties (Typical Values)
| Properties | Value | Unit | Test Standard |
|---|
| APHA Color | ≤100 | — | — |
| Shelf Life (uninitiated, dark) | 3 | months | — |
Recommended Initial SMC Paste Formulation
| Component | Weight (kg) |
|---|
| PLM-128 (UP Resin) | 70 |
| PLM-9892 (Low Profile Additive) | 30 |
| TBPB (Initiator) | 1.5 |
| Zinc Stearate (Release Agent) | 4 |
| Ground Calcium Carbonate (Filler) | 150 |
| Magnesium Oxide Paste (35% active MgO) | 3.0 |
Typical Properties of SMC Molding Compound (PLM-9892 Based)
| Properties | Value | Unit | Test Standard |
|---|
| Density | 1.8 | g/cm³ | — |
| Shrinkage | 0 | % | — |
| Flexural Strength | 200 | MPa | ISO 178 |
| Flexural Modulus | 14500 | MPa | ISO 178 |
| Impact Strength | 120 | kJ/m² | ISO 179 |
| Glass Transition Temperature | 210 | °C | DIN 53455 |
| Coefficient of Linear Thermal Expansion | 23×10⁻⁶ | K⁻¹ | DIN 53752 |
Application
Automotive Components
Electrical Enclosures
Sanitary Ware
Precision Structural Parts
FAQ: Technical Insights
What are Low Profile Additives (LPA) and Low Shrinkage Additives (LSA) for molding resins?
Low Profile Additives (LPA) and Low Shrinkage Additives (LSA) for molding resins are functional auxiliaries specifically designed for molding processes (such as SMC, BMC, and general molding resins). They typically consist of thermoplastic polymers or composite systems.
Primary Function: Their core function is to compensate for the polymerization shrinkage and thermal shrinkage of the resin during the curing process through a mechanism of microscopic phase separation. This effectively reduces the molding shrinkage rate of the finished product, minimizing defects such as sink marks, deformation, surface depressions, cracks, and flow lines. Simultaneously, LPAs enhance the product's dimensional stability, surface finish, and flatness. They are well-suited for thick-walled and complex-shaped molded parts, particularly those demanding high molding precision and superior aesthetic quality.
What are the common types of Low Profile Additives (LPA)? How does one select the appropriate type?
Common types fall into four categories, allowing for precise selection based on product requirements:
① Non-polar type (e.g., Polystyrene/PS): Offers good internal colorability but provides only moderate low-shrinkage performance at a relatively low cost. Note: Due to its low polarity (approx. 0.3), it exhibits poor compatibility with unsaturated resins (polarity approx. 20) and therefore requires a compatibilizer.
② Weakly polar type (e.g., Polymethyl methacrylate/PMMA): Exhibits moderate resin compatibility and offers better shrinkage control than PS, though colorability is somewhat inferior.
③ Polar type (e.g., Polyvinyl acetate/PVAc, Saturated polyesters): Delivers the most effective low-shrinkage performance. It demonstrates excellent compatibility with unsaturated polyester resins (PVAc polarity is approx. 1.3, closely matching the resin), making it ideal for high-precision, Class-A surface products.
④ Combination type (e.g., Core-shell polymers): Offers excellent comprehensive performance, balancing shrinkage control, colorability, and mechanical strength while preventing macroscopic phase separation.
Selection Focus: Prioritize matching the specific resin type and the precision requirements of the final product. We highly recommend requesting samples for compatibility testing before mass production.
What is the recommended addition ratio for these anti-shrinkage additives?
The standard addition ratio is 5%–10% of the total resin weight.
Ratio Adjustments: For thick-walled or high-precision products, the ratio may be increased to 8%–12%; for standard parts, 5%–8% is sufficient. If inorganic fillers (such as calcium carbonate or talc) are used in the formulation, the LPA ratio must be fine-tuned to balance shrinkage control and paste flowability.
Impact of Addition Errors:
• Adding too little: Fails to effectively compensate for resin shrinkage, leaving the product prone to sink marks, warping, surface depressions, and poor dimensional stability.
• Adding too much: Leads to reduced product toughness and increased brittleness. It can exacerbate phase separation, causing surface mottling, additive migration (blooming), and delamination from the resin matrix. Additionally, it negatively impacts paste flowability, potentially causing incomplete mold filling.
Formulation & Molding: PLM-9892 is typically used in conjunction with PLM-128 to produce low-shrink molding compounds. The standard ratio of PLM-128 to PLM-9892 is 70:30, which can be fine-tuned based on actual processing conditions. Molding conditions: 140–160℃ at 50–100 kg/cm². Depending on dimensional precision requirements, 300–600 ppm of hydroquinone (calculated based on the total weight of resin and LPA) can be added as an inhibitor.
Storage Requirements: Before use, store the resin in its original unopened packaging in a dry indoor area maintained at 5℃–30℃, and consume as soon as possible. If prolonged storage is required, it must be kept in its original unopened packaging within a low-temperature environment or a cold storage facility.
Temperature & Light Warning: Elevated temperatures and light exposure will significantly shorten the shelf life. Strictly keep away from direct sunlight and heat sources. Furthermore, excessive temperature fluctuations may cause internal condensation, which severely negatively impacts resin curing and cross-linking.
Safety & Flammability: Unsaturated polyester resins and additives containing styrene are highly flammable. Keep strictly away from open flames, sparks, and ignition sources. Always refer to the official Safety Data Sheet (SDS) for comprehensive handling and emergency procedures.
