SPE Library
The SPE Library contains thousands of papers, presentations, journal briefs and recorded webinars from the best minds in the Plastics Industry. Spanning almost two decades, this collection of published research and development work in polymer science and plastics technology is a wealth of knowledge and information for anyone involved in plastics.
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Conference Proceedings
FLEXURAL PROPERTIES AND FAILURE MECHANISM ASSESSMENT FOR
ADDITIVE MANUFACTURED LOM BARS ON DIFFERENT BUILDING
ORIENTATIONS
Plastic Laminated Object Manufacturing has not been
assessed from the flexural properties point of view. The
deflection range in parts manufactured by this technique is
wider than in parts fabricated by other additive
manufacturing methods like SLS or FDM. This fact has
increased the interest on the final application of these parts
rather than restricted to Rapid Prototyping applications. In
this study it will be compared the impact of building
orientation and geometric features of parts over the
flexural properties. Through optical observation it will be
studied the failure mechanism
SEQUENTIAL INJECTION MOLDING: DESIGN CONSIDERATIONS
New injection processes have been developed last decades, improving the designer freedom in order to launch attractive functionalities. All these procedures should be carefully analysed before to decide their use, because it is necessary to understand their natural restrictions, cost and operation requirements and rheological implications in the tools construction. This contribution presents a wide study made in the T.I.I.P., research group from the University of Zaragoza, which gives simulation results and experimental values about sequential injection moulding, and some practical considerations for designers and toolmakers, in order to get successfully results.
KINETCIS AND CHEMICAL REACTIONS OF ACETALDEHYDE STRIPPING PROCESS IN POLY(ETHYLENE TEREPHTHALATE) RESIN
The Kinetics of acetaldehyde (AA) stripping from PET pellets were determined at different temperatures, along with the determination of the residual concentrations of other less volatile compounds such as 2-methyl-1,3-dioxolane (2MD). The rate constants for the polymerization and AA diffusivity coefficients were determined at different temperatures of air stripping of PET. The air stripping of AA from PET is shown to involve chemical reactions and physical changes including polymerization, diffusion and generation of AA, 2MD, EG and water. This paper discusses the mechanisms of the chemical reactions and the formation of the by-products. The techniques used to elucidate the mechanism include gas chromatography (GC), intrinsic viscosity (IV), and density.
FEED ENHANCEMENT TECHNOLOGY FOR LOW BULK DENSITY MATERIAL
INTO CO-ROTATING TWIN-SCREW COMPOUNDING EXTRUDERS
Effectively feeding low bulk density material into a
co-rotating twin-screw extruder has always been a
challenge. However with the introduction of even finer
particle size fillers (sub-micron in some cases) as well as
new generations of polymer reactor resins, the issue has
become even more problematic. Additionally as bulk
density decreases, the materials tend to fluidize more
easily. Fluidization lowers the “effective” bulk density
even further and exacerbates feeding issues. Typical unit
operations within the compounding process where
material is more susceptible to fluidization are: transfer
from storage vessel to feeders, from feeder to twin-screw
extruder and within the feed zone conveying section of the
twin-screw extruder. While there are methods to minimize
the potential for fluidization such as dense phase
conveying from storage to feeder, minimization of the
feeder height above the extruder feed opening,
incorporating a vent into the feed hopper, extending the
length of the conveying zone in the extruder feed section,
the process eventually reaches a feed volume limitation,
which more often than not is well below an economically
viable production rate. This paper will review a new Feed
Enhancement Technology (FET) that provides significant
improvement for the introduction of fine particle / low
bulk density materials into the extruder.
Co-rotating Fully Intermeshing Twin-screw Compounding Extruders Technology:
Advancements for Improved Performance and Productivity
The co-rotating fully intermeshing twin-screw
extruder is the primary production unit for compounding
of polymer based materials. It also has had a long term
presence in processing material in the chemical and food
industry and more recently in pharmaceuticals. While this
equipment celebrated its 50th anniversary several years
ago and might be considered a “mature” technology, it has
not experienced a decline in new developments as might
be expected, but rather a significant number of
advancements continue to evolve. This paper will
highlight several significant developments of the past 10
to 15 years. These are the implementation of high torque
(power) designs, the use of increased rpm in conjunction
with high torque for improved operating flexibility and
productivity, and finally a technology breakthrough for
feeding difficult to handle low bulk density materials.
COMPUTATIONAL ANALYSIS AND DESIGN OF SINGLE SCREW EXTRUDERS
HAVING SCREWS OF COMPLEX GEOMETRY WITH MIXING ELEMENTS
The methodology is based on some conventional
models for flow in the hopper, solids bed and melting
zone. In the melt pumping zone the Hele – Shaw
approximation is applied, which describes spreading flow
in two dimensions. The momentum and energy equations
are solved layer – by – layer starting from the barrel wall.
This methodology enables significant reduction of
computer time required for simulation of extruders with
complex screw geometry, over the fully 3D approach.
Good agreement was obtained with some available
experimental data and further evaluations of predictive
capabilities are currently underway.
PROCESSING AND PROPERTIES OF BIOABSORBABLE PLLA-HA COMPOSITES
Orthopedic procedures often require repair materials
that can carry large loads without excessive deformation or
failure. To this end, we designed composites using two
biocompatible/bioabsorbable polymers, poly(L-lactic acid)
(PLLA) and polycaprolactone (PCL). The latter was filled
with nano-needles of hydroxyapatite (HA), while the
PLLA was used in long-fiber form. Theory advises that
the HA nano-needles must be of high aspect ratio and be
aligned in the matrix to gain sufficient stiffness. We have
explored several processing techniques for accomplishing
this task, and have successfully made composites in the 8-
to 10-GPa range. Variations of this structure will also be
described.
STAGES MOULDING A NEW TECHNOLOGY FOR THE PRODUCTION OF PLASTIC PARTS
This paper presents a novel technology to produce
plastic parts called “Stages Moulding”. The patented
technology allows producing plastic parts with complex
shapes, from a wide variety of polymers, with excellent
surface quality, reduced thermal and mechanical stresses
and possibility to produce parts with reduced weights.
This novel process uses cheaper moulds and equipments
than those used in injection moulding. The specific
characteristics previously mentioned make this
technology very promising for the production of plastic
parts for different markets. The paper explains the main
characteristics of this technology presenting some real
examples of parts produced.
DEVELOPMENT OF STARCH BIOBASED AND BIODEGRADABLE PLASTICS
FOR THEIR USE IN TRAYS FOR FOOD-PACKAGING
This research work develops new methods to
produce biodegradable starch-based trays for the
purpose of replacing expanded polystyrene in the food
packaging market. The starch based biopolymers
present several drawbacks like poor mechanical
properties and very high density. In order to overcome
these drawbacks two research lines have been set up:
blending thermoplastic starch with biobased
reinforcements from agricultural wastes like barley
straw and grape wastes, and testing the foamability of
these materials with a Microwave-foaming method.
RELEVANCE OF THE FEMTOLASER NOTCH SHARPENING ON THE IMPACT
FRACTURE OF POLYCARBONATE
The traditional sharpening through the razor blade
method employed in the fracture characterization of
polymers creates plastic deformation at the notch tip,
which affects the fracture toughness values. Recently it
has been applied a technique based on femtosecond
pulsed laser ablation, which removes material with almost
no heat dissipation, preventing melting and thermal
deformation of the surrounding area and without plastic
deformation at the crack tip. In this work, the fracture
toughness of polycarbonate was studied using the Linear
Elastic Fracture Mechanics testing procedure at impact
velocity, evaluating the influence of crack sharpening by
femtolaser or razor blade sliding.
EFFECT OF NANOCLAYS ON THE FOAMING BEHAVIOR OF RIGID
POLYURETHANE MONITORED BY X-RAY RADIOSCOPY
X-ray radioscopy is a technique in which a series of
radiographies are acquired during an evolving process.
The present study aims to investigate the mechanisms
occurring during the reactive foaming process of rigid
polyurethane (PU) foams in its liquid state. The work
addresses a comparative study of in-situ pore growth
determination in PU foams with and without
nanoadditives (nanoclays), based on the mentioned
technique and thus providing a valid methodology to
investigate the foaming process in all its stages. The
results confirm that nanoparticles addition modify the
final pore size most probably based on a higher
nucleation rate at initial stages.
POLYURETHANE FOAM NANOCOMPOSITES: RELATIONSHIP BETWEEN MECHANICAL PROPERTIES AND FILLER-MATRIX CHEMICAL INTERACTION
Nanofillers are added to rigid PU foams to improve their mechanical properties, however this expected behaviour is not always found. A poor dispersion of the fillers is usually accepted as a possible explanation, but chemical interaction between matrix and fillers could also result in a reduction of the final foam properties. In this study, polyurethane rigid foams (with and without nanoclays) have been produced and characterized. Different dispersion techniques have been used. The experimental results suggested that chemical interaction between fillers and matrix plays a critical role in the mechanical behaviour of these type of systems.
IMPROVING THE THERMAL INSULATION OF POLYSTYRENE FOAMS BY THE
ADDITION OF CARBON BLACK.
This paper presents an investigation on the improvement
of the thermal conductivity of polystyrene foams by using
different types of carbon blacks as additives. Carbon
blacks with different morphologies were used as IRblockers.
To test the changes in the conductivity foams
with densities between 20 and 100 kg/m3 were produced
using the solid state foaming technique. The cellular
structure and thermal conductivity were analyzed in
detail. In addition the thermal conductivity was
analytically modeled to study the influence of the
different carbon black types on the heat flow by radiation.
The best morphology to reduce the thermal conductivity
has been detected.
STUDY ON RAPID MANUFACTURING TRAINING NEEDS IN THE EUROPEAN CONTEXT
Rapid Manufacturing (RM), as one of the most important emerging technologies, has a high potential as part of European industry, with a clear role in manufacturing process and economy. In this context, seven EU entities have proposed an e-learning program on these technologies, to increase its knowledge and use, with the aim of improving competitiveness in companies. Results on surveys prepared in this project with the aim of establishing the actual situation in Europe in this field and filled in by companies and training centres are presented in this communication, providing an overview of RM general knowledge and use.
THIN TPO FILM OVERMOLDING FOR VEHICLES INTERIORS DECORATION
Many vehicle manufacturers are aiming diversifying
their car interiors with more daring colours and textures
with limiting the amount of investment. For large
interior parts, like instrument or door panels, special
resins or painting technology was considered current
state of the art. A new technology, thin TPO film
overmoulding, could replace this current state of the art
technology.
The main paper objective of this paper is to describe the
advantages and the issues in using thin thermoplastic
olefin (TPO) foil overmolding as an alternative. This
paper presents the new generation of TPO “ready for
graining” soft foils and the innovative tooling & process
needed to laminate the foil during the PP direct injection
shot
EXPANDED INJECTED PP SYSTEM TO MAKE 25% LIGHTER ESTHETICAL
INSTRUMENT PANEL
By the year 2025, carbon emissions levels will require for
the main vehicle in the world important weight
reductions. Plastics components can now be expanded
during injection keeping correct mechanical behavior to
design vehicle interiors. The paper presents the
instrument panel application and describes the
importance of the Polypropylene (PP) material, the
expansion technology and the related component,
injection press and tooling designs. The paper aims to
demonstrate how applications like visible instrument
topper panels or side trimmings could be designed in
purpose to respect esthetical and mechanical
specifications
PRODUCTION OF POLYPROPYLENE (PP) FOAMS FROM A CONVENTIONAL PP
GRADE. ANALYSIS OF CELLULAR STRUCTURE AND MECHANICAL
PROPERTIES.
Foaming of polypropylene is not trivial due to its
weak melt strength and its semicristalline character. The
solutions proposed up to now are based in crosslinking
the polymeric matrix or in the use of special
polypropylene grades.
A collection of samples with relative densities in the
range of 0.3-0.6 have been produced using a conventional
PP grade. The improved compression moulding foaming
process which uses a chemical blowing agent was used to
produce the analyzed foams. The effect of chemical
composition on both cellular and mechanical properties
has been analyzed.
ADHESION BETWEEN POLYPROPYLENE AND STEEL BY OVER MOULDING
In this work, a hybrid polypropylene (PP)/steel car
part (Traverse leg) was created by over moulding. PP was
modified with 10%wt. of PP-g-Ma coupling agent.
Different surface treatments were applied to the steel
determining its influence on adhesion. Best peel strength
was reached when the steel was sanded. Etching and shot
peened plates showed similar but lower levels of
adhesion. In all cases, the application of torch heating was
necessary to create a thin layer of iron oxide strongly
bonded to the steel and by reaction to the PP-g-Ma. To
create adhesion a minimum steel temperature of 120ºC
was necessary.
T.I.I.P.: A TRAINING AND RESEARCH GROUP IN INJECTION MOLDING
Created from University of Zaragoza, the group T.I.I.P. has developed its activities since 1989 around injection molding. This team has always worked as near as possible to the industry (its name includes “workshop”, not “laboratory") and, in its aims, it promotes the research work pushed from market demands. However, for an effective knowledge exchange, the members of the group T.I.I.P. have promoted hundreds of training courses teaching to all the injection´s actors, about how to arrange the whole process to improve final results. During these twenty years, fifteen doctoral theses and twenty friendly computer programs for training were made, closing the loop.
HALOGEN-FREE FLAME RETARDANT POLYOLEFIN FOAMS
FOR AUTOMOTIVE APPLICATIONS
A new type of materials has been produced by means of
creating a cellular structure in blends of LDPE/LLDPEg-
MAH/ATH. The presence of the aluminium hydroxide
(ATH) in a polymer blend, both as flame retardant and
reinforcement, significantly increases the density of the
end product. The aim of this work is to achieve a cellular
structure by foaming these materials, when high loading
levels up to 60wt% of ATH are included. As a result, a
density reduction of 50% has been obtained together
with excellent mechanical and flame retardant
properties. A comparison of these properties between
solid and foamed materials is included.
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