1.Core Scorching (Reaction center temperature exceeds material oxidation temperature):
Polyether polyol quality issues: Excessive moisture, high peroxide, low-boiling impurities, high metal ions, improper antioxidant type/concentration.
Formulation: High TDI index in low-density formulas, incorrect water to physical blowing agent ratio, insufficient physical blowing agent, excessive water.
Climate impact: High summer temperatures, slow heat dissipation, high material temperatures, high humidity, causing the center temperature to exceed the oxidation temperature.
Improper storage: Increased TDI index leading to heat accumulation during post-curing, causing internal temperature rise and core scorching.
2.Large Compression Deformation:
Polyether Polyol: Functionality < 2.5, propylene oxide ratio > 8%, high low molecular weight components, unsaturation > 0.05 mol/kg.
Process Conditions: Incorrect reaction center temperature, poor post-curing, incomplete reaction, partial scorching.
Process Formula: TDI index too low (105-108), excess silicone oil stannous octoate, low foam air content, high closed-cell content.
3.Foam too Soft (Decreased hardness at same density):
Polyether Polyol: Low functionality, low hydroxyl value, high molecular weight.
Process Formulation: Low T9 octoate tin content, slow gel reaction speed, low water content, high physical blowing agents, high activity silicone oil, low TDI index.
4.Large Cell Size:
Poor Mixing: Uneven mixing, short cream time. Increase mixer speed, decrease mixer pressure, increase air injection. For small cells, increase mixer pressure, decrease mixer speed, reduce air injection.
Process Formulation: Low silicone oil, low/inactive octoate tin dosage, slow gel speed.
5.Density Higher than Set Value:
Polyether Polyols: Low activity, high molecular weight.
Process Formulation: Low silicone oil, low TDI index, low foaming index.
Climate Conditions: Low temperature, high pressure increases density.
6.Collapsed Cells and Hollows (Gas release faster than gelation):
Polyether Polyols: High acid value, high impurities, low activity, high molecular weight.
Process Formulation: High amine, low tin (fast foaming, slow gelation), low TDI index, inadequate silicone oil. High TDI index with same tin leads to faster gas release than gelation.
Low-pressure foaming machine: Reduce gas injection and mixer head speed.
7.High Closed-Cell Ratio:
Polyether Polyols: High ethylene oxide ratio, high activity, often when switching polyols.
Process Formulation: High octoate tin, high isocyanate reactivity, fast crosslinking, excessive amine/physical blowing agents lead to low foam pressure, preventing cell opening.
8.Shrinkage (Gelation faster than foaming):
High closed-cell ratio: Shrinkage during cooling.
Process Conditions: Low air and material temperature.
Process Formulation: Excessive silicone oil, low amine, high tin, low TDI index.
Low-pressure foaming machine: Increase mixing head speed, gas injection.
9.Cracking:
Shape and Position: “八”-shaped cracks (excess amine), single line cracks (excess water), middle/bottom (high amine), top (imbalance in gas-generating gelation speed), internal (low air temperature, high center temperature, low TDI, excess tin), side (increase tin), throughout process (disharmony between dropping plate and reaction).
Main Causes: Imbalanced catalyst, improper TDI isomer ratio, excess vibration, prolonged polyether storage increasing water content.
10.Unclear Cell Structure:
Stirring Speed: Too fast.
Air Injection: Excessive.
Metering Pump Flow: Inaccurate.
Material Pipelines/Filters: Blocked.
11.Bottom Corner Cracks:
Excessive Amine: Rapid foaming.
Large Surface Pores: Excess physical blowing agent, poor silicone oil/catalyst.
12.Poor Low-Temperature Performance:
Polyether Polyols: Low functionality/unsaturation, low TDI index.
13.Poor Ventilation:
Climate Conditions: Low temperature.
Raw Materials: High polyether polyol content, high silicone oil activity.
Process Formula: Excessive tin, low water/amine content, high TDI index.
14.Poor Rebound Resilience:
Raw Materials: High polyether polyol activity, low molecular weight, high silicone oil activity.
Process Formulation: High silicone oil/tin content, more water, high TDI index, large white oil, excess powder.
15.Low Tensile Strength:
Raw Materials: Excessive low-molecular-weight polyether polyols, low functionality.
Process Formulation: Insufficient tin, high TDI index, low crosslinking due to low water.
16.Smoke During Foaming:
Excessive Amine: Causes heat release, evaporating low-boiling substances, resulting in smoke.
Excessive TDI: Surface evaporation.
17.Foam with White Streaks:
Fast Foaming/Gelation: Slow transfer during continuous foaming, causing local dense layer and white streaks. Increase transfer speed, reduce material temperature, reduce catalyst.
18.Brittle Foam:
Formulation: Excess water, many urea compounds, poor tin catalyst, incomplete cross-linking, high low-molecular-weight polyether, high reaction temperature, reduced foam strength due to ether bond breakage.
19.Foam Density Lower than Set Value:
Foaming Index: Too large due to inaccurate metering, high air temperature, low air pressure.
20.Foaming with Skin, Edge Skin, Bottom Air:
Excess Tin, Low Amine: Slow foaming, fast gelation, low temperature during continuous foaming.
21.Elongation Rate Too High:
Raw Materials: High polyether polyol activity, low functionality.
Process Formulation: Low TDI index, insufficient cross-linking, high tin.
22.Chaotic Foaming:
Small Bubbles: Rapidly moving beneath the surface.
Low-pressure Foaming Machine: Increase mixing head speed, decrease gas injection.
High-pressure Foaming Machine: Increase mixing head pressure.
23.Milky Moving Lines:
Increase Conveyor Speed.
Adjust Cushion Plate Inclination.
Reduce Amine Catalyst Usage.
24.Inserted Material Backflow:
Increase Conveyor Speed.
Adjust Cushion Plate Inclination.
Increase Amine Catalyst Usage.
25.Crescent-shaped Pits:
Low-pressure Foaming Machine: Reduce mixing head speed and gas injection.
High-pressure Foaming Machine: Increase mixing head pressure.
Silicone Oil Quality: Ensure adequate cell opening.
26.Slow Curing, Sticky Surface:
Manifestations: Slow polymer strength increase, soft/sticky foam, difficult cutting, unstable foam blocks.
Solution: Increase catalyst dosage, check polyol, water, TDI metering.