Innovation: SELF-REINFORCED SHEETS FROM NEAT POLYMERS

Last update: 29.06.2013
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Keywords: 
plastics, self-reinforced, winding, polymers, sheets, composite, moulding, mechanical properties, tensile strength
The stationary technical and technological content in materials, machinery and products of the material handling sector together with the high percentage incidence of costs due to manual operations have resulted in a heavy rise of products being imported from low labour cost countries, such as China. Launching cost-competitive products with high technological content and superior technical performances could indeed face this trend. This perfectly marries the wish of plastics manufacturers. As a matter of facts, the manufacturing of plastic products has dramatically decreased during the last years. Therefore, several SMEs are opening their market to a wide range of not exploited sectors and developing advanced/innovative products through the use of cutting edge materials and technologies. The hand pallet truck (HPT) production has been identified as one possible application where techno-plastics could play a crucial role in, totally modifying the performances as well as the business of the material handling sector.
The main aim of the project ECOPAT is to design and develop the new generation of all-plastic, lightweight, chemically passive and cost-effective HPTs to be efficiently used in material handling applications. This purpose has been achieved thanks to the production of one full-scale HPT prototype made of glass-reinforced plastic which has allowed the final evaluation of the performances of the product and the benefits on health and safety in handling environments. The novel HPT is more than 55% lighter than traditional steel pallet trucks which turns into easiness of use, greater manoeuvrability and reduced noise and is also deemed to have better aesthetical quality, easiness in keeping it clean and strong resistance to corrosion. The novel HPT has therefore considerably improved handling performances over existing products though still allowing the safely lift of loads up to 1000 kg.
In parallel, basic research on self-reinforced plastic materials and their manufacturing processes has been conducted in the project, with the future aim to apply this novel category of plastics to the HPTs production. Dog-bone samples have been produced from self-reinforced pellets and sheets by injection and compression moulding processes and used for characterization of mechanical and physical properties. Also, two heating methods have been applied, i.e., classical resistance heating and novel induction heating. Test samples have been compared against percentage and orientation of reinforcing fibres, layout and processing conditions. The following conclusions have been achieved:
a) Despite the narrow processing window between low melting matrix polymer and high melting reinforcing fibres and independently on the heating system applied, the fibres still exist in the test samples.
b) Injection moulded samples have only marginally improved mechanical properties over the un-reinforced samples because of relaxation, partial degradation and agglomeration of fibres. Further research is needed to improve the properties of self-reinforced pellets and their application to the injection moulding process before proceeding with the scale-up of the processing route – co-extrusion and injection moulding – from laboratory to industrial level.
c) Compression moulded samples show considerably increased mechanical properties over the un-reinforced samples. Mechanical properties evidently benefit from the presence of fibres especially if oriented along the direction of the applied load. No further basic research is needed but the scale-up of the processing route – winding and compression moulding – from laboratory to industrial level.
d) Induction heating is proved to allow shorter processing cycles and faster controller response, to be more energy-efficient and not to affect the properties of the self-reinforced material. If applied to the moulds for compression, it requires careful design supported by FEM analyses to ensure uniform heating of the parts. Oppositely, its application to injection equipment is easy and turns into substantial energy savings.

PROJECT GOALS:

The main goal of the project ECOPAT is to design and develop the new generation of all-plastic, lightweight, chemically passive and cost-effective HPTs to be efficiently used in material handling applications. The main drivers and needs which address this specific goal are:
1. To improve hand pallet truck technical characteristics and operational performances, such as strength, stiffness, lightness, life cycle, to name but a few;
2. To reduce hand pallet truck environmental impact through the employment of resource efficient manufacturing processes;
3. To improve health & safety working conditions;
4. To extend business markets and employment sectors by guaranteeing technically competitive cost-effective HPTs.
Based on these primary drivers, the project has been broken down into a series of likely solutions to the problems. Fostering research on self-reinforced plastics and moulding technologies needed to produce components from this new family of materials is key to the development of novel HPTs with high technical and technological content. At the time of the proposal submission, early commercial grades of self-reinforced plastics were only available as non-flowing sheet materials, which was restricting their use to simple parts with constant wall thickness. Moreover, the properties of plastics were only improved by adding mineral powders or fibres, which increases the weight of the material, significantly reduces the recyclability (and the purity of the recyclate) and increases the wear of tools and processing equipment. In this context, the project ECOPAT would lead to a step change in cutting-edge self-reinforced plastics technology by developing flowing and mouldable versions of self-reinforced plastics. Complex, net-shape parts would be possible, thereby reducing material use and eliminating trimming waste and process energy. This would reduce the amount of material required to make a part and open the door to a vast range of applications for these sustainable materials. The related scientific and technical objectives which mainly concern self-reinforced plastics definition and manufacturing processes were identified to be:
• Identification of the most suitable polymer materials to be processed both as matrix and fibres among polyolefins, polyamides and polyesters, based on a critical analysis of their mechanical and thermal properties;
• Maximization of the difference between the melt temperature of the matrix phase and the temperature at which the reinforcement phase becomes unstable;
• Identification of suitable impregnation methods of the high melting polymeric fibres with the low melting polymeric matrix to produce self-reinforced composites for subsequent injection and compression moulding;
• Determination of suitable moulding process conditions taking into account the need for selectively pre-heating – by means of classical and novel heating techniques – the compound in order not to affect the properties of fibres;
• Manufacturing of small-scale samples and definition of an experimental testing campaign introductory to analyze the developed self-reinforced plastic characteristics in terms of mechanical and chemical properties;
• Designing of HPT components through the identification of the most simple HPT geometry though taking into account the static and dynamic structural response of the parts, the constraints from the moulding processes and the need for easy assembling/disassembling;
• Full-scale prototype manufacturing followed by its industrial validation accomplished through both traditional testing procedures and material handling in-field demonstrations;
• Dissemination of the findings/results of the project and patent issue request.
Metocene PP matrix polymer and nucleated Moplen HP500N reinforcement polymer were used to produce semi-finished sheets. Semi-finished sheets were produced by means of a motorized winding process which allows laboratory production of uni-directionally and bi-directionally self-reinforced sheets with different combinations of reinforcing layers. Sheets were then pressed and plates heated up by resistance and induction heating alternatively.
The applied method of pressing of oriented polypropylene fiber layers and low-melting PP film leads to effective production of SPC of acceptable mechanical properties. When applied as composite matrix, polypropylene Metocene PP facilitates lowering the temperature of SPC pressing. However, it requires precise selection of processing conditions which would enable a proper connection of matrix with reinforcing phase, while preserving the excellent mechanical properties of the latter. Additional challenge is the choice of film layer of appropriate thickness and the amount of fiber layers which is crucial to obtain a composite containing maximum number of fibers and the most advantageous mechanical properties.
The results of tensile strength tests can be considered satisfactory. Significant increase of tensile strength in comparison to neat matrix can be obtained with even small amount of oriented PP fibres into PP matrix. When the content of fibres in the composite amounts to about 30% tensile strength equals 130 MPa (about +225% in comparison to neat matrix) while E modulus is about 1.7 GPa (about +20% in comparison to neat matrix). By the way, the mechanical properties of SPC compound substantially depend on reinforcing fibres arrangement. The fibres arranged parallel to the load direction make the material clearly stiffer and reinforced. On the other hand, perpendicular arrangement of the fibres results in material weakening. Tensile tests of samples from compression molding with inductive system, despite technical problems like non uniform heating and matrix flow from mould show very common results.

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This innovation is the result of the project

Title: Development of a cost-effective and lightweight hand pallet truck for application in material handling

Acronym: 
ECOPAT

Runtime: 
01.08.2010 to 31.10.2012

Status: 
completed project

Organisations and people involved in this eco-innovation.

Please click on an entry to view all contact details.

OFFICINE MECCANO-PLASTICHE SPA

(Italy)

Role in project: Project Coordination

Contact person: Ms. SALVI Monica

Website: http://www.ompspa.com

Phone: +39 035 4500139

Contact

CENTRO DE CONTRATACION DE TRANSPORTES DE MURCIA, SOCIEDAD COOPERATIVA

(Spain)

Contact person: Mr. SOLANA PEDREÑO Miguel

Phone: +34-968160099

Contact

CHABELI TRANS SL

(Spain)

Contact person: Mr. PEREZ Manuel

Phone: +34-663110243

Contact

CIM-MES PROJEKT SP ZOO

(Poland)

Contact person: Mr. KRASUCKI Janusz

Website: http://www.cim-mes.com.pl

Phone: +48-226312244

Contact

D'APPOLONIA SPA

(Italy)

Contact person: Ms. BERTOLUCCI Laura

Website: http://www.dappolonia.it

Phone: +39-0103628148

Contact

IMPRIMA CONSTRUCTION CZ A.S.

(Czech Republic)

Contact person: Mr. TORRI Diego

Website: http://www.imprimaconstruction.cz

Phone: +39-3357488279

Contact

INDUSTRIAL TECHNOLOGY INVESTMENTS POLAND SP ZOO

(Poland)

Contact person: Mr. GORALEWSKI Krzysztof

Website: http://www.iti-poland.com.pl

Phone: +48-525669262

Contact

LIFTER S.R.L.

(Italy)

Contact person: Ms. BIANCHI Rosella

Phone: +39-0577965241

Contact

MACIEJ I TADEUSZ POPIELAWSCY PIMETSJ

(Poland)

Contact person: Mr. POPIELAWSKI Maciej

Website: http://www.pimet.com.pl

Phone: +48-22-7234205

Contact

POZNAN UNIVERSITY OF TECHNOLOGY

(Poland)

Contact person: Ms. DOPIERALA Barbara

Website: http://www.put.poznan.pl

Phone: +48-616653612

Contact