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Thermoplastic Composite
Composite materials are defined by three primary types of components: a resin matrix, an armature and operational additives. Thermoset composites are transformed from a liquid to a solid through a no-reversible chemical change, while thermoplastic composites are solidified through a reversible thermal curing process.
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Thermoplastic Reinforced Plastics/Thermoplastic Composite
Thermoplastic reinforced materials are high-performance composites made from thermoplastic resins and reinforcing fibers. They feature lightweight properties, excellent impact resistance, recyclability, and re-processability. Through physical reinforcement and interface engineering, these materials achieve significantly higher mechanical performance than conventional plastics at much lower density, making them widely used in automotive components, rail transit, sports equipment, appliance structural parts, industrial devices, and lightweight aerospace applications.
Based on the length and structural form of the reinforcing fibers, thermoplastic reinforced materials can be classified into short-fiber reinforced, medium–long fiber reinforced, long-fiber reinforced, and continuous-fiber reinforced systems. Different applications require different reinforcement types to balance strength, toughness, processability, and cost.
Types of thermoplastic reinforced materials include:
- Long fiber reinforced materials (LFT-G, LFT-D)
- Unidirectional prepreg tapes (UD Tape)
- Short fiber reinforced thermoplastics (SFT)
- Medium–long fiber reinforced materials (MFT)
- Continuous fiber multi-axial reinforced composites (CFRTP/GFRTP sheet)
- Thermoplastic prepreg sheets (e.g., GMT)
- Various fiber-reinforced compound pellets (GF/CF/AF/mineral-filled)
Among these reinforcement systems, long fiber thermoplastic materials (LFT) and continuous fiber unidirectional thermoplastic tapes (UD Tape) are currently the fastest-growing and most performance-dominant categories.
Thermoplastic composite materials consist of two parts: the matrix and the reinforcement.
The matrix surrounds and bonds the fibers, and its main functions include:
- Transferring loads
- Protecting the fibers
- Providing toughness, heat resistance, and chemical resistance
- Determining processing temperature and processing conditions
Common matrix materials include PP, PA, PC, PPA, PET, PBT, PLA, TPU, PPS, and PEEK.
The reinforcement primarily determines the strength, stiffness, and mechanical performance of the composite.
Common reinforcing fibers include glass fiber, carbon fiber, aramid fiber, plant fiber, and basalt fiber.
Chuangbo provides the following solutions for thermoplastic reinforced materials:
- LFT-G long fiber thermoplastic compounding production lines
- UD Tape (unidirectional thermoplastic prepreg tape) production lines
Unidirectional Prepreg Tape
UD Tape Production Process
1、Resin Feeding & Melting (Extrusion)Thermoplastic resins (PP, PA, PPS, PEEK, etc.) are fed into a twin-screw extruder and plasticized into a homogeneous melt.
Key point: Temperature and viscosity control are critical for impregnation quality.
2、Fiber Spreading
Continuous fibers (glass, carbon, aramid, basalt) are fully spread using a spreading unit to separate individual filaments.
Purpose: Increase resin contact area, reduce voids, and improve impregnation uniformity.
3、Melt Impregnation
The spread fiber bundle passes through the impregnation die.
The die is filled with resin flow channels, allowing the molten resin to uniformly coat each individual filament, ensuring stable performance and consistent tape thickness.
At this stage, the resin does not need to fully penetrate into the interior of the fiber bundle; it only needs to form a uniform thin layer. This requires highly precise “thin-layer coating” of resin, typically with a thickness of 0.1–0.3 mm. Such an ultra-thin layer is ideal for tape stacking, laminate production, and compression molding.
Features: high impregnation depth, low void content, and minimal fiber damage.
4、Consolidation
The impregnated tape enters a consolidation section, where pressure and temperature compact the material and increase density.
5、Cooling
The consolidated tape is cooled and solidified, stabilizing its thickness and surface density.
6、Take-up & Winding
The finished tape is pulled and wound into rolls for weaving, multi-axial lay-up, compression molding, etc.
Reinforcement Materials for UD Tape
UD Tape requires the use of continuous fibers (Continuous Fiber), which must meet the following conditions:
1、Maintain Continuous Length Without Breakage
Since UD Tape is an uncut continuous reinforcement tape, the fibers must retain complete continuity. Examples include: glass fiber, carbon fiber, aramid fiber, basalt fiber, etc.
2、High Strength and High Modulus
The performance of UD Tape primarily comes from the reinforcing fibers. Therefore, fibers must have high tensile strength and high elastic modulus, especially for structural components.
3、Surface Treatment Compatible with Resin
The fiber surface must be treated with sizing to match the resin. For example:
- PP requires polyolefin-based sizing
- PA requires amide-compatible sizing
- PPS/PEEK require high-temperature resin-compatible sizing
- PC requires polycarbonate-compatible treatment
Incompatible fiber sizing can lead to delamination, poor adhesion, and reduced strength.
4、Good Spreadability, Uniform Filaments, No Fiber Loss
UD Tape production emphasizes the full spreading of individual filaments. Therefore, fiber bundles must be easy to spread, filaments must be uniform, and fibers should not fuzz or break easily. This is why plant fibers and polymer fibers are used only in certain low-temperature systems, while glass fiber and carbon fiber are most commonly used.
Matrix Materials for UD Tape
UD Tape must use thermoplastic resins and meet the following criteria:
1、Moderate Melt Flow / Viscosity
The resin must have good flow during extrusion and impregnation to penetrate fiber bundles adequately. Melt viscosity should not be too high (insufficient impregnation) or too low (sagging, uneven distribution). Typical resins:
PP, PA, PC, PPA, PET, PBT, PLA, TPU, PPS, PEEK, etc.
2、 Good Interfacial Adhesion with Fibers
The resin must be compatible with the fiber surface to ensure a strong bond. For example:
- PA, PPS, PEEK are highly compatible with carbon fibers
- PP with glass fiber requires MAH grafting for good adhesion
3、 Good Thermal Stability
UD Tape production requires high processing temperatures (180–380°C). Resins must be thermally stable, resistant to decomposition, and free of gas formation during prolonged heating.
4、High Reprocessability
UD Tape will undergo subsequent automated fiber placement (AFP/ATL), compression molding, and hot-press lamination. Resins must withstand multiple heating cycles without degradation.
5、Mature Pellet Quality Requirements
Resins typically need uniform particle size, low moisture content (especially PA, PBT), and may require compatibilizers or toughening agents.
Additional Material Requirements for Processing
1、Matching Coefficient of Thermal Expansion (CTE)
A large difference in thermal expansion between resin and fiber can cause internal stress and warpage.
2、Moisture Control (especially for PA and PBT)
UD Tape is extremely sensitive to bubbles in thin tapes. For example:
- PA must be dried to ≤ 0.08%
- PBT must be dried to ≤ 0.02%
3、Dispersibility
Resin must be free of impurities, coarse particles, or unmixed additives; otherwise, surface defects in the tape may occur.
LFT-G (Long Fiber Reinforced Thermoplastic) Pelletizing Production Line
LFT-G Production Process
In simple terms, the LFT-G process involves directly impregnating continuous fibers into molten resin, followed by pultrusion and cutting into pellets of uniform length.
The typical production process of LFT-G is as follows:
1、Material Metering and Feeding
- Resin is fed from the silo into a loss-in-weight feeder
- Ensures precise control of the resin-to-fiber ratio
2、Resin Melting (Twin Screw Extrusion)
- Resin enters a twin-screw extruder
- Plasticized and melted to form a stable molten resin
3、Fiber Feeding and Tension Control
- Continuous glass or carbon fibers are supplied from the fiber creel
- Ensures fiber feed rate matches the extrusion speed
4、Preheating and Pre-dispersion (Pretreatment)
- Improves fiber wetting by the resin
- Prevents incomplete impregnation due to temperature differences
5、Melt Impregnation (Core Step)
- Continuous fibers pass through the impregnation die
- Resin uniformly coats the fibers from the outside
- Fibers are fully impregnated within the die channels
Key Points: High impregnation depth, preservation of original fiber strength, controlled fiber content (typically 20–60%)
6、Cooling and Pulling
- Impregnated strips pass through a cooling water tank
- Pulled out steadily by the traction system
7、Pelletizing
Long-fiber specific pelletizer cuts the impregnated strands into 10–25 mm reinforced pellets
8、Screening and Packaging
- Irregular pellets are removed by sieving
- Finished pellets are stored in silos for packaging
Key Features of LFT-G
- Maximum fiber length retention
- High toughness and impact performance
- Excellent injection molding processability
- Suitable for single-piece molding, can replace metals and conventional engineering plastics
LFT-G Reinforcing Fibers
The LFT-G process requires fibers that are high-temperature resistant (200–350°C), non-decomposing, non-melting, and non-charring, such as glass fiber, carbon fiber, basalt fiber, and polymer fibers.
Tip: Aramid fibers and plant fibers may decompose at high temperatures. These materials can be seen in UD tape production, but are rarely used in LFT-G manufacturing.
LFT-G Matrix Materials
Compared with UD tape, LFT-G production requires higher resin flowability. The molten resin must fully, rapidly, and evenly impregnate the fiber bundle before pelletizing.
Common matrix resins for LFT-G include:
PP, PA6, PA12, PA66, PC, PPA, PET, PBT, PLA, TPU, PPS, PEEK, etc.
Tip: Unlike UD tape, within the PA family, different PAs have significant differences in melting temperature and process windows. Therefore, LFT-G raw materials usually specify the PA type, e.g., PA6, PA66, or PA12.
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