1. Introduction

Since the outbreak of CHINA-US trade friction in 2018, both countries have imposed additional tariffs on thousands of goods, including plastic products. By April 2025, cumulative US tariffs on certain Chinese goods had reached 104%, significantly increasing export costs for Chinese manufacturing. Polypropylene (PP), a critical material in the home appliance industry (accounting for over 40% of plastic usage in appliances), urgently requires technological innovation to reduce costs and improve efficiency. This article proposes systematic solutions for PP materials based on foaming theory,filling systems, structural optimization**, and **recycled material applications**, using refrigerator and washing machine components as case studies and integrating domestic and international research with industrial practices.  

2. Foaming Theory: Lightweighting and Cost Efficiency Maximization  

2.1 Microcellular Foaming Technology

Technical Principle 

Microcellular foaming injects supercritical fluids (e.g., CO₂ or N₂) into a polymer matrix to form closed-cell structures with pore sizes<100 μm, achieving up to 30% weight reduction. Its core advantage lies in replacing traditional injection molding pressure-holding stages with cell growth, reducing material shrinkage, warpage, and internal stress.  

International Cases 

- MuCell® Technology: Developed by US-based Trexel, this microcellular foaming technology is widely used in automotive and home appliance sectors. For example, a refrigerator door liner produced with MuCell® reduced wall thickness from 3 mm to 2 mm, lowering material costs by **25%** and shortening cycle time by **15%**.  

- Borealis ePP Technology: Extruded expanded PP (ePP) beads are used for refrigerator insulation layers, reducing costs by 60% compared to traditional autoclave processes.  

Domestic Progress

- Midea Group applied microcellular foamed PP in microwave oven casings, achieving 18% weight reduction while balancing mechanical performance and cost by optimizing foam density (0.6–0.8 g/cm³).  

2.2 Expanded Polypropylene (ePP)

Technical Features

ePP beads, formed via steam-chest molding, produce lightweight components with complex geometries. For instance, Haier’s refrigerator insulation layers using ePP reduced raw material consumption by 30% and logistics costs by 20% by eliminating intermediate storage.  

International Comparison

- Japan's JSP Corporation's ARPRO® ePP, with a density as low as 0.03 g/cm³ and compressive strength of 1.5 MPa, is widely used in automotive interiors, offering insights for appliance lightweighting.  

3. Filling Systems: Low-Cost, High-Performance Modification

3.1 Mineral Filler Reinforcement

Talc and Calcium Carbonate

- Economic Analysis: PP composites with 20-40% talc reduce costs by 15-25% versus pure PP. For example, Kelon’s refrigerator shelves using 30% talc-filled PP achieved a tensile strength of 33 MPa, saving ¥2,000 per ton compared to ABS.  

- International Research: Germany’s Fraunhofer Institute found that nano-sized talc (<1 μm) increases PP flexural modulus by 50% while maintaining 90% impact strength via silane surface treatment.  

Glass Fiber Reinforcement  

- Short Glass Fiber (SGF): 20% SGF-reinforced PP matches PA66's tensile strength at 60% lower cost. SABIC’s G1620B PP-SGF composite, used in washing machine drums, saves millions annually.  

- Long Glass Fiber (LGF): US-based RTP’s LGF-PP composites retain >70% fiber length, improving impact strength by 40% versus SGF systems, ideal for load-bearing parts like refrigerator brackets.  

3.2 Bio-Based and Recycled Fillers

Natural Fibers

- Southeast Asian firms use 15% palm fiber in PP outdoor furniture, reducing density by 20% while enhancing aesthetics.  

- BASF's coPaXX®series employs flax fiber-reinforced PP, cutting carbon emissions by 30% versus glass fiber systems.  

Recycled Plastic Blends

- East China University of Science and Technology blended recycled PET (R-PET) with PP using POE-g-GMA compatibilizers, achieving 35 MPa tensile strength and 18% cost reduction with 12% R-PET.  

- US-based Trex uses recycled HDPE/PP blends for outdoor flooring, matching pure PP’s performance while reducing material costs by 40%.  

4. Structural Optimization: Design-Driven Cost Reduction

4.1 Topology and Wall Thickness Optimization  

CAE Simulation  

- Borouge optimized PP fan blade wall thickness via ANSYS, reducing weight by 12% and material costs by 8% without compromising airflow.  

- Toshiba redesigned refrigerator drawer ribs using Moldflow, increasing rib height from 5 mm to 8 mm and reducing main wall thickness from 2.5 mm to 2 mm, achieving 15% weight reduction.  

Biomimetic Design  

- Haier's washing machine drums adopted a hexagonal honeycomb structure, thinning walls to 1.2 mm and shortening injection cycles by 10%.  

4.2 Surface Treatment Technologies 

Wear-Resistant Coatings  

- Dow's SILASTIC® silicone coatings increased PP surface hardness from Shore D60 to D80, reduced friction coefficient to 0.2, and tripled lifespan for refrigerator handles.  

- LG Chem’s nano-TiO₂ composite coatings combine wear resistance and antibacterial properties, achieving<5% haze="" and="">85% transmittance in refrigerator liners.  

Plasma Treatment

- Germany's Plasmatreat enhanced PP surface polarity via atmospheric plasma, improving coating adhesion by 5x and reducing primer use by 30% in microwave oven panels.  

5. Recycled Materials and Circular Economy

5.1 High-Value Waste PP Utilization

Chemical Recycling  

- UK's Recycling Technologies pyrolyzes waste PP into 99% pure naphtha via RT7000 units, lowering recycled PP costs by 25% versus virgin resin.  

- Chinese Academy of Sciences  supercritical water oxidation degrades contaminated PP into monomers, with<10% mechanical property loss after repolymerization.  

Physical Modification

- Xi'an Jiaotong University replaced HIPS with waste PP in yogurt cups, using β-nucleating agents to boost crystallinity and reduce costs by 20%.  

- IBM and HP developed carbon black-filled recycled PP 3D printing filaments (40 MPa tensile strength) for customized appliance parts.  

5.2 Bio-Based PP Development

- Brazil's Braskem produces Green PP from sugarcane ethanol, reducing carbon emissions by 70%, used in Electrolux refrigerator seals.  

- Netherlands Avantium's FDCA-based PP (PEF) offers superior barrier properties, potentially replacing multi-layer packaging by 2030 at cost parity.  

6. Case Study: Cost Reduction for Refrigerator Door Panels

6.1 Technical Approach

- Foaming Layer: MuCell® microcellular PP core (0.75 g/cm³) reduced weight by 20% and material costs by 30%.  

- Filling System: 30% talc-filled PP outer layer increased modulus by 40% and cut raw material costs by 25%.  

- Design: Topology optimization increased rib density from 5 to 8 ribs/m² and reduced main wall thickness from 3 mm to 2.5 mm, boosting stiffness by 15%.  

6.2 Economic Benefits

7. Conclusions and Future Trends

To address trade barriers and cost pressures, PP cost reduction requires multi-technology synergy:  

1. Foaming for lightweighting with advanced processes like MuCell®;  

2. Filling systems balancing mineral fillers and bio-based materials;  

3. Structural optimization via CAE and biomimetic design;  

4. Recycled materials enabling circular economies through chemical/physical methods.  

Future Trends:  

- AI-Driven Formulations: Braunschweig University’s neural networks optimize PP/elastomer/filler systems, boosting toughness 10x with<8% modulus loss.  

- Low-Carbon Processes: EU Green Deal promotes supercritical foaming over chemical agents, cutting emissions by 30%.  

- Multifunctional Integration: Antibacterial PP films (rare-earth nucleators + silver-loaded zirconium phosphate) replace HIPS in food packaging.  

8. STP New Materials Technology’s Innovative Solutions

Facing cost pressures and sustainability demands from Sino-US trade friction, STP proposes a "Foaming-Filling-Eco" integrated strategy to drive cost efficiency and green transformation for appliances, automotive, and construction industries.  

8.1 Chemical Foaming PP Solutions

- Foaming Agents: Eco-friendly azodicarbonamide (AC series) generates N₂/CO₂ for uniform closed-cell structures (0.7–1.0 g/cm³), reducing weight by 10–20%.  

- Applications: Refrigerator door liners (0.8 g/cm³, 15% weight reduction) and appliance packaging inserts (30% thinner than EPS).  

8.2 Filling System Optimization 

- Talc/Calcium Carbonate: 20-40% fillers enhance stiffness (flexural modulus ≥2500 MPa) and cut costs by 15–25%.  

- SGF Reinforcement: 20% glass fiber delivers PA66-level strength at 30–40% lower cost.  

8.3 Eco-Friendly Low-Cost Materials  

- Recycled PP Blends: 30-50% R-PP with compatibilizers retains ≥85% tensile strength and reduces costs by 30–40%.  

- Bio-Based Additives: Starch/lignin fillers (5-30%) lower petroleum dependency for disposable products.  

Why Choose STP?

✅ Cost Reduction: Verified 15-40% savings via foaming and filling.  

✅ Customization: Tailored formulas and processes.  

✅ Sustainability: Compliant with global green standards.  

Join STP in Building a Low-Carbon Future! 

Contact us:  

- Website: www.sustainpellet.com

- Email: stp@sustainpellet.com  Innovation-Driven, Responsibility-Led – STP Delivers High Value, Reliability, and Sustainability!