1 Overview

1.1 Introduction

LFT-D is short for Long Fiber Reinforce Thermoplastic In Direct Processing.


1.2 Process Characteristics

Compared with GMT and LDT-G, which rely on semi-finished plates or granules, LDT-D technology directly uses polymer masterbatch and glass fiber for daily production, which eliminates the intermediate process of plate making or granuleting, reduces cost and makes the selection of raw materials more convenient and practical.

The polymer granule can be quickly adjusted and converted according to the product demand and adverse conditions occurred in the production. The fiber used for reinforcement can be changed according to the mechanical properties. For some special physical properties and some special characteristics proposed by the vehicle manufacturer, such as thermal stability, flame retardant, heat aging, coloring, water absorption resistance, etc. The performance of the final product can be improved by adding other modification additives directly on line. The LFT-D manufacturing process is unique in its material formulation and can be adapted to the performance requirements of the vast majority of components.


1.3 Technological Process

The typical LFT-D process involves the delivery of polymer pellets and additives to a metering and feeding unit, which is initially programmed to ensure that the designed proportions are fed. The proportionally-measured material enters the twin-screw extruder for plasticizing and mixing, and the molten polymer passes through a thin film die to form a polymer film similar to a waterfall, directly into the opening of the twin-screw extruder. The glass fiber is introduced to the top of the polymer film through the specially designed longitudinal frame, after preheating and dispersing procedures, etc., and the film is combined into the second-stage twin-screw extruder, where the glass fiber is impregnated, cut and mixed to form a continuous material block, which is cut by the cutting tool at the front of the twin-screw glass fiber plastic mixed extruder into a material block in line with the molding area of the product. The conveyor belt transmits it to the appropriate location, and then sends it to the mold for low-temperature molding. The whole process is generally 30 ~ 50 seconds, which has great processing cost advantage compared with GMT type.


2. LFT-D features and advantages

2.1 Performance Features

(1) Light weight and high strength. LFT density is about 1.1g /cm, only 1/5~1/7 of steel, tensile strength 50~120MPa, bending strength 90 ~120MPa;

(2) Thermal performance.

General plastic use temperature is 50~100°C, the use of glass fiber reinforced, can be increased to more than 100°C,

Some special LFT can be used at temperatures above 200°C; The line swelling coefficient is 25% to 50% lower than that of unreinforced plastic, the thermal conductivity is 0.3 to 0.36W/(m •K), and the thermosetting composite material is very similar.

(3) chemical corrosion resistance. This property is mainly determined by the properties of the substrate materials. There are many types of thermoplastic resins, each of which has its own anti-corrosion characteristics. Therefore, the substrate resins can be optimized according to the LFT environment and medium conditions.

(4) Good dielectric properties. LFT does not reflect radio waves and has good performance through microwaves. Adding conductive material to LFT can improve its conductivity and prevent static electricity.

As a new technology competing with GMT at the same time, LFT-D products can be compared with the excellent application performance brought by GMT to a large extent.

The main advantage of GMT products is its excellent impact resistance, while the advantage of LDT-D products is that they have good toughness and can meet the actual market demand at a lower cost.

It has been shown that the mechanical properties of LFT products, especially the impact strength of cantilever beam, can be significantly improved by properly adding the reinforcement woven fabric into the raw material polymer masterbatch.



2.2 Economic Advantages

(1) The direct online production mode of raw materials greatly reduces the cost of products and avoids higher procurement and related logistics and warehousing costs of semi-finished products;

(2) Since the raw materials required for production are directly purchased, the rapid change of raw materials can make up for the problems of long cycle and high management cost caused by the purchase of semi-finished raw materials, and indirectly reduce the production cost;

(3) The consumption of raw materials in the processing process is lower than the starting consumption, which solves the problem of raw material loss at the initial stage of pressing;

(4) The residual temperature of plasticized material is used for immediate molding, which eliminates the energy loss caused by secondary heating of semi-finished plates. The production process is all controlled by the program, and the production line runs automatically, significantly reducing the overall energy consumption;

(5) Thermoplastic LFT material is recyclable plastic, LFT production line can process the recycled material online, environmental protection but also brings excellent economic benefits

(6) reduced a large number of manual operations, labor costs decreased significantly.



2.3 Technical Advantages

(1) The formula adjustment is more flexible and diverse. Only by making corresponding adjustments to the equipment of the LDT-D production line, different polymer granules such as PP, PA6, PET, ABS and PC can be used. In addition, the raw material ratio can be quickly adjusted on site for the special requirements of different products;

(2) As an important component to ensure mechanical properties of composite materials, the continuous adjustable molding technology will greatly optimize the performance of the products;

(3) The final product retains a glass fiber length of more than 20mm, which solves the problem of low mechanical strength caused by too short glass fiber length in mass rapid production

(4) Excellent mixing process, can ensure that the glass fiber and plastic are fully mixed, even in the rib can ensure uniform fiber distribution;

(4) Excellent mixing process, can ensure that the glass fiber and plastic are fully mixed, even in the rib can ensure uniform fiber distribution;

(5) Superior fluidity, greatly improving the surface quality of products;

(6) The high degree of automation of LFT-D equipment ensures the quality and stability of products.



3 Application Fields

3.1 Application Scope

At present, the main application field of LFT-D production technology is still the automobile manufacturing.

In the process of automotive lightweight, under the premise of ensuring vehicle safety, the conventional fuel efficiency can be increased by 6%~8% for every 10% reduction in vehicle weight. The replacement of metal materials by composite materials has become the mainstream trend of industrial development. As the leading lightweight technology in the automobile industry, LFT-D thermoplastic composite has been applied in many well-known vehicle factories. Currently, the parts with a more mature manufacturing mode include front end module, bumper bracket, instrument panel skeleton, seat skeleton, underbody protection plate, interior trim bracket, wheel cover, battery tray, utility box cover, rear hatchback door, spare tire box, etc.



3.2 Application Example:

LFT-D long fiber reinforced thermoplastic composite products intelligent production line is mainly used for the production of: front end module, bumper beam, instrument panel skeleton, battery

Bracket, tire compartment, seat frame, pedal and whole bottom plate, engine hood, luggage rack, spare placenta, fender, Fengkang blade, engine bottom

Plate, car roof lining frame, packaging products, pallets, military parts, sports equipment, electronic appliances and other parts.


3.2.1 Bottom protection plate/Bottom deflector plate

In the early stage, the underbody protection board was attached to the white car body for the protection of important components. Later, due to the late 1980s and early 1990s, Germany formulated a very strict vehicle noise protection law, which made it evolve into a large plate covering the whole chassis. With the development of the bottom guard plate, its shape has become more complex from a simple flat plate, and its functions have begun to combine sound absorption, heat insulation, corrosion resistance, high rigidity, high impact strength and other properties. The materials evolved from steel and aluminum to GMT. Until the late 1990s, the direct online mixing LFT-D technology with lower cost and more flexible molding methods was produced. Some manufacturers began to use the lightweight and high-strength thermoplastic LWRT with highly expanded fibers, which has lower toughness than traditional GMT but higher specific stiffness and excellent sound absorption performance. The manufacturing and application of automotive bottom guard plate has been relatively mature, and it is used in Volkswagen Tiguan, SAIC Roewe 350, 550, 750, and SAIC E50 electric vehicles.



3.2.2 Front-end Module

In traditional automobile front-end modules, sheet metal parts are sent to the vehicle factory by dozens of parts suppliers, and then final assembly is carried out. Due to the heavy front-end modules, the assembly efficiency and production tempo of the final assembly line are highly required. A new supply model is the use of LFT technology and the modular production model of components such as lighting, cooling and shock absorption, which are assembled in advance to form front end modules and then sent to the Oems.



3.2.3 Seat frame

By simulating and optimizing the layout of the metal seat skeleton model in professional analysis software, the shape of the parts can be customized for production in the LDT-D process. Local reinforcement can be performed by adding inserts to the assembly to protect the ride capacity to prevent misalignment in the event of a crash and optimize the ductility and deformation capacity of the LFT and local uninterrupted reinforcement during impact. LFT can replace steel weight reduction of more than 40%, and can achieve a high degree of integrated functions, to achieve functional integration. The seat frame of Great Wall Automobile Haver H5 is made of LFT-D technology.



4. Market status and development prospects

4.1 Domestic and international development

At present, in Europe, due to higher labor costs and environmental protection standards than other regions such as the United States and Asia, and relatively concentrated automobile composite parts manufacturers with large output of a single product, automotive composite parts suppliers are more likely to use the LDT-D production technology, while in other regions such as the United States, they are more likely to use the LDT-G pellet production technology. Mainly because of its parts procurement system, the manufacturers are all over the place, the output of a single product is small, the purpose is relatively scattered, so it is more suitable to use the LFT-G production technology.

In the past two years, more than 30 LDT-D production lines have been put into operation in the European and American markets. Japan and South Korea will also introduce LDT-D equipment in the next few years. The fast and efficient production mode will greatly reduce the cost of these auto parts manufacturers.

The research and development of LFT materials began in the late 1980s and early 1990s, which was about the same time as that in Europe and America. At present, some enterprises have initially formed LFT products with independent intellectual property rights, and have a certain production capacity.




4.2 Opportunities brought by modular production of auto parts

The so-called modular production of auto parts refers to a part or component as the center, the surrounding parts together, through a molding processing, which can reduce a lot of manufacturing costs and mold inspection tools.

Research conducted by Ford Company shows that the use of composite products in automobile manufacturing can reduce the number of parts to 80 to 90 percent of the original, the manufacturing cost will be reduced by 60 percent compared to metal materials, and the bonding cost will be reduced by 25 to 40 percent compared to welding.

BASF is working on a new idea to integrate the vehicle oil storage tank, permanent filter and oil pump into the bottom of the vehicle. A module made of 35% glass fiber reinforced PA66. The transmission assembly of the BMW series is made of 35% glass fiber reinforced PA66 produced by Bayer. It not only saves the precious space in the engine body, but also reduces the molding process.

TecAir, of Illinois, makes a five-pound, 22-inch-long auto-engine cooling fan from high-flow nylon, which combines the fan wheel with other intake components and is already used in a GM model.

Mercedes Benz utilizza la termoplastica rinforzata con fibra di vetro anziché l'alluminio per realizzare i coperchi delle punterie su tre modelli di autocarri leggeri, Atego, Vario e Unimog. La copertura è realizzata in resina di nylon Zyte170G35HSLRA4 di DuPont Automotive rinforzata con il 35% di fibra di vetro. Integra il separatore d'olio e il coperchio per ridurre sensibilmente il rumore del motore.

Come nuova forza nel campo dei materiali compositi, la tecnologia LFT-D presenta i vantaggi di progettabilità, alta efficienza, basso costo e ampia selezione di materiali, che soddisfano notevolmente le esigenze della produzione modulare nel processo di produzione automobilistica e diventerà una nuova forza che non può essere ignorata nell'industria automobilistica.



4.3 Prospettive di mercato

Negli ultimi decenni, LFT D è diventata una modalità di produzione con tecnologia all'avanguardia. Nel settore automobilistico domestico, LFT si è lentamente spostata verso prodotti con struttura complessa e funzioni speciali. Inoltre, LFT ha anche iniziato a sostituire alcuni processi tradizionali in molti campi al di fuori della produzione automobilistica e lo sviluppo del mercato ha compiuto i primi progressi.

Nel 2010 rappresentava il 9% del consumo totale di LFT, dopo Europa, Nord America e Giappone. Nel 2011, tuttavia, aveva superato il Giappone, che rappresenta l'11% del consumo attuale, secondo Townsend. Con il materiale LFT in crescita a un tasso annuo del 12% tra il 2006 e il 2011, almeno tre volte il tasso di crescita del PIL, questa tecnologia di stampaggio diretto termoplastico rinforzato con fibre lunghe rappresenta un'opportunità molto interessante sia nel settore automobilistico che in quello non automobilistico.

La tecnologia LFT-D si sta gradualmente sviluppando nella direzione di alte prestazioni, basso costo, modularizzazione, leggerezza e standardizzazione e svolgerà un ruolo maggiore nel risparmio energetico, nella riduzione delle emissioni e nell'industria automobilistica rispettosa dell'ambiente.