Plastics Materials (Part Two): In-Depth Analysis of PP+EPDM-TD

Time：2026-09-30 08:01:46 / Popularity： / Source：

For previous reading, please refer to Plastic Materials (Part 1): In-Depth Analysis of PP Material.
PP+EPDM-TD is one of the most classic and widely used material systems in automotive modified plastics. It uses polypropylene as matrix, toughened with EPDM rubber and reinforced with talc (Talc) filler. Three components work synergistically to achieve a balance of rigidity, toughness, heat resistance, and dimensional stability, making it preferred material for core automotive components such as bumpers, dashboards, and door panels.

I. What is PP+EPDM-TD? A Visual Guide

PP+EPDM-TD is a ternary composite modification system. Each letter has a specific function:

Components	Full Name	Function
PP	Polypropylene	Matrix material, providing basic mechanical properties, chemical resistance, and processability
EPDM	Ethylene Propylene Diene Monomer Rubber	Toughening phase, significantly improving impact strength and low-temperature toughness
TD	Talc Filled	Reinforcing phase, improving rigidity, heat resistance, and dimensional stability

Number after TD indicates percentage of talc filler: TD10 = 10% talc; TD15 = 15% talc; TD20 = 20% talc (most commonly used); TD25 = 25% talc; TD30 = 30% talc.
MD = Mineral Filled, similar to TD, but the filler type may differ slightly.
Three-phase microstructure

Blue PP matrix (image): Continuous phase, bearing main load. Orange flake-like talc: Dispersed in matrix, acting like "scales" to improve rigidity and heat resistance. Green spherical EPDM: Rubber particles that deform and absorb energy upon impact, improving toughness.
Influence of Talc Filler Content

Performance	With increasing TD content	Reasons
Stiffness (Flexural Modulus)	↑Increase	Talc's flake-like structure restricts molecular chain movement.
Heat Resistance (HDT)	↑Increase	Filler increases heat distortion temperature.
Dimensional Stability	↑Increase	Molding shrinkage decreases.
Impact Toughness	↓Decrease	Filler increases stress concentration points.
Density	↑Increase	Talc density (~2.7) is much higher than PP (0.9).
Surface Quality	↓Decrease	High filler content easily leads to loose fibers and rough surface.

Core principle: Higher TD content results in better rigidity but lower toughness. In engineering, a balance needs to be found between rigidity and toughness—this is precisely significance of EPDM rubber: using EPDM to "compensate" for toughness lost by talc.
TD10 (10% Talc): TD10 has a low filler content, good toughness, and low density (~0.96 g/cm³), but its rigidity and heat resistance are average. It is suitable for exterior parts requiring high toughness and with low loads.
TD15 (15% Talc): TD15 is "sweet spot" for interior trim parts, offering a good balance of rigidity and toughness, with excellent surface quality. It is widely used in dashboards and door panels.
TD20 (20% Talc) – Most Commonly Used Grade: TD20 is mainstream grade in automotive PP+EPDM system, offering the best balance of rigidity, toughness, heat resistance, and cost. It is widely used in bumpers and dashboards. Typical performance range: flexural modulus 1500~2000 MPa, density approximately 1.04 g/cm³.
TD25 (25% Talc): TD25 offers higher rigidity, suitable for structural components requiring high rigidity and dimensional stability. Low-VOC version meets automotive air quality regulations.
TD30 (30% Talc): TD30 has the highest filler content and the strongest rigidity (flexural modulus can reach over 2500 MPa), but its toughness decreases significantly. It also has the highest density (~1.10 g/cm³), making it suitable for replacing high-rigidity metal structural components. Data sources: Kingfa Science & Technology, Borealis, LyondellBasell official product pages and TDS; MatWeb, UL Prospector, SpecialChem databases; ISO/ASTM standard test methods. Detailed parameters for JSJ and some grades are subject to manufacturer's latest TDS.

II. Mechanical Property Laws and Yield-to-Trypsum Ratio

Mechanical properties of PP+EPDM-TD change systematically with talc content. Understanding these laws allows for quick selection.
Typical performance comparison of different TD contents

Properties	TD10	TD15	TD20	TD30	Test Standards
Density	~0.96 g/cm3	~1.00 g/cm3	~1.04 g/cm3	~1.10 g/cm³	ISO 1183
Flexural Modulus	1200~1500MPa	1500~1800MPa	1700~2100MPa	2400~3000MPa	ISO 178
Tensile Yield Strength	20~25 MPa	22~27 MPa	23~28 MPa	28~35 MPa	ISO 527
Notched Charpy Impact (23℃)	25~40 kJ/m2	20~35 kJ/m2	15~30 kJ/m²	8~15kJ/m²	ISO 179
Notched Charpy Impact (-30℃)	6~12 kJ/m2	5~10 kJ/m2	4~8kJ/m²	2~5 kJ/m²	ISO 179
Heat Deflection Temperature (0.45MPa)	85~95℃	90~100℃	95~105℃	105~115℃	ISO 75
Molding Shrinkage	1.0~1.4%	0.9~1.2%	0.8~1.1%	0.6~0.9%	ISO 294-4

Note: Above are typical ranges for materials of same grade. Specific values vary depending on EPDM content, talc mesh size, and matrix grade. Higher EPDM content results in better impact but lower rigidity.
Yield-to-tensile strength ratio analysis: Yield-to-tensile strength ratio = Yield strength / Tensile strength, reflecting material's plasticity reserve:
Low TD (TD10) + High EPDM: Low yield-to-tensile strength ratio (~0.5~0.6), good toughness, large deformation after yielding, suitable for energy-absorbing components such as bumpers.
Medium TD (TD15~20): Medium yield-to-tensile strength ratio (~0.6~0.7), balanced stiffness and toughness, the strongest for general use.
High TD (TD30): High yield-to-tensile strength ratio (~0.7~0.8), good rigidity but slightly brittle, suitable for structural load-bearing components.
Selection rule: For toughness, choose low TD and high EPDM; for rigidity, choose high TD; for balance, choose TD20.

III. Molding process: Mainly injection molding

Molding process of PP+EPDM-TD is similar to that of ordinary PP, but talc filler brings some special considerations.
Key Process Parameters

Parameters	Recommended Range	Explanation
Barrel Temperature	200~230℃	Segmented heating, highest at nozzle end
Mold Temperature	30~60℃	Higher mold temperature results in better surface finish and more uniform curing, but longer cycle time
Injection Pressure	70~130 MPa	Slightly poorer filler flowability, slightly higher pressure
Screw Speed	60~120 rpm	Excessive shearing can break talc flakes
Back Pressure	5~15 MPa	Appropriate back pressure improves plasticization uniformity

IV. Automotive Application Overview

PP+EPDM-TD is "main force" in automotive interior and exterior trim, with 40-60 kg of this material used in a passenger car.
Exterior Trim Components

Components	Common grades	Key requirements
Front and rear bumpers	TD20 (most common)/TD15	High impact resistance, low-temperature toughness, paintable, weather resistance
Side trim	TD10/TD15	Surface quality, UV resistance, dimensional stability
Spoiler	TD10/TD15	Lightweight, aesthetically pleasing, paintable
Wheel arch covers/mudguards	TD20/TD30	Stone chip resistance, good rigidity, dirt resistance
Grill	TD20	High flowability, dimensional stability, good appearance
Underbody protection	TD30	High rigidity, impact resistance, sand and gravel resistance

Why use TD20 for bumpers? Bumpers need to simultaneously meet following requirements: impact energy absorption (toughness), dimensional stability (rigidity), low-temperature crack resistance (low-temperature toughness), and paintability (surface quality). Combination of TD20 and EPDM toughening achieves the best balance among these dimensions.
Interior Trim Components

Components	Common grades	Key requirements
Instrument panel frame	TD15/TD20	High rigidity, heat resistance, low VOC, low odor
Door trim panels	TD15/TD20	Balance of rigidity and toughness, low emission, scratch resistance
Pillar trim panels (A/B/C pillars)	TD10/TD15	Low density, surface quality, weather resistance
Center console	TD15/TD20	Dimensional stability, scratch resistance, low VOC
Glove box/storage compartment	TD10/TD15	Good toughness, low odor

Why use TD15-20 for dashboards? Dashboard is the largest structural component in interior, requiring sufficient rigidity to prevent noise and deformation during driving, while also being heat-resistant (up to 90℃+ in summer) and meeting low VOC regulations. TD15-20 provides sufficient rigidity and heat resistance, while also meeting requirements for toughness and surface quality.
Functional Components

Components	Common Grades	Key Requirements
Air Filter Housing	TD20	Heat Resistance, Dimensional Stability
Fan Cover/Envelope	TD20/TD30	High Rigidity, Heat Resistance, Vibration Resistance
Battery Housing	TD20	Acid Resistance, Vibration Resistance
Seat Trim Panel	TD15/TD20	Balance of Rigidity and Toughness, Good Appearance

V. CAE Simulation

PP+EPDM-TD is a filled and modified viscoelastic-plastic material. Simulation modeling is more complex than for pure PP, requiring consideration of anisotropy and rate dependence introduced by filler.
Five Commonly Used Constitutive Models

Models	Applicable Scenarios	Features
Elastic-Plastic Model	Static stiffness, strength analysis	Most commonly used, input stress-plastic strain curve, sufficient engineering accuracy
Drucker-Prager	Multiaxial stress, snap-fit	Consides pressure-dependent yield, filler polymer yield is affected by hydrostatic pressure
Marlow Hyperelastic	Large deformation, low-speed bumper impact	Fits the entire yield-necking-hardening process, suitable for large strain problems
Viscoelastic/Viscoplastic	Dynamic impact, creep	Consides strain rate and time effects, essential for impact and long-term loads
Damage Coupling Model	Failure prediction, crack propagation	Consides filler interface debonding and matrix damage evolution

Typical Simulation of Automotive PP+EPDM-TD Components

Simulation Types	Model Used	Results to Consider
Instrument Panel Stiffness	Elastic-Plastic	Displacement, Stress Distribution
Modal/NVH	Linear Elastic	Natural Frequency, Mode Shape
Low-Speed Bumper Collision	Marlow/Elastic-Plastic + Damage	Energy Absorption, Intrusion, Cracks
Thermal Deformation/Warpage	Thermo-Elastic-Plastic	Warpage, Residual Stress
Creep (Long-Term Load)	Viscoelastic/Creep Model	Long-Term Deformation, Stress Relaxation
Vibration Fatigue	Elastic-Plastic + Fatigue Criterion	Fatigue Life, Safety Factor
Pedestrian Protection Collision	Elastic-Plastic + Rate-Related	Head Acceleration, HIC Value

Development Trends
High-flow TD material: Continuously improving MFR, supporting thin-walled and large-part integrated injection molding. Low VOC / Low odor: Standard for interior trim, achieved through optimized formulation and processing technology. No painting required / Matte finish: Special color powders and surface modification technologies save painting steps. High rigidity and low density: Achieving higher rigidity with lower filler content through talc surface treatment and morphology optimization. Long glass fiber reinforced PP (LFT-PP): Replacing short glass fiber and metal, used in structural components such as front-end modules and seat frames. Microfoamed PP+EPDM-TD: Chemical/physical foaming, reducing weight by 15~25% while improving sound insulation. Recycled / Regenerated TD material: Driven by automotive recycling regulations, increasing application in non-critical components, and continuously improving quality. Low warpage / High dimensional accuracy: Meeting higher assembly accuracy requirements through filler morphology optimization and orientation control