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Lab
Services
Whether it's a specific test or a program to qualify your product to your customer, we can provide the service you need. NPI has labs at both of its plants and provides lab services from the Brampton location. All tests are performed to ASTM standards. Lab testing capabilities include:
- Melt Index
- Density
- Ash Content
- DSC Analysis
- Instron Tensile Testing
- IZOD Impact
- Elmendorf Tear
- C.O.F
- Dart Drop and others
Our lab processing equipment includes:
- Lab Film Line
- Lab Pelletizing Line 2
- Lab Injection Molders.
We are always in the market for buying post-industrial feedstocks which include plastic films and molding regrinds. If you are interested please contact us and provide us with a representative sample of your material which we will quickly qualify in our lab.
Melt Index - back
Melt Flow Rate measures the rate of extrusion of thermoplastics through
an orifice at a prescribed temperature and load. It provides a means of
measuring flow of a melted material which can be used to differentiate
grades as with polyethylene, or determine the extent of degradation of
the plastic as a result of molding. Degraded materials would generally
flow more as a result of reduced molecular weight, and could exhibit reduced
physical properties. Typically, flow rates for a part and the resin it
is molded from are determined, then a percentage difference can be calculated.
Alternatively, comparisons between "good" parts and "bad" parts may be
of value.
Test Procedure:
Approximately 7 grams of the material is loaded into the barrel of the
melt flow apparatus, which has been heated to a temperature specified
for the material. A weight specified for the material is applied to a
plunger and the molten material is forced through the die. A timed extrudate
is collected and weighed. Melt flow rate values are calculated in g/10
min.
Test Specimen Size:
At least 14 grams of material is needed.
Data:
Flow rate = ( 600/t x weight of extrudate)
t = time of extrudate in seconds
melt flow rate = g/10 min.
The melt index of a resin describes the flow behavior that can be expected during processing. It usually varies due to the average molecular weight of the polymer. The melt index refers to the amount of resin in grams of a thermoplastic material which can be forced through a 0.0825 inch orifice when subjected to 2160 grams of force in 10 minutes at 190° C. If the melt index of a resin is high, the melt flow resistance during processing is low. That is, the material flows through a mold or extruder die faster than a resin with a low melt index.
Izod Impact - back
Notched Izod Impact is a single point test that measures a materials resistance
to impact from a swinging pendulum. Izod impact is defined as the kinetic
energy needed to initiate fracture and continue the fracture until the
specimen is broken. Izod specimens are notched to prevent deformation
of the specimen upon impact. This test can be used as a quick and easy
quality control check to determine if a material meets specific impact
properties or to compare materials for general toughness.
Test Procedure:
The specimen is clamped into the pendulum impact test fixture with the
notched side facing the striking edge of the pendulum. The pendulum is
released and allowed to strike through the specimen. If breakage does
not occur, a heavier hammer is used until failure occurs. Since many materials
(especially thermoplastics) exhibit lower impact strength at reduced temperatures,
it is sometimes appropriate to test materials at temperatures that simulate
the intended end use environment
Reduced Test Procedure:
The specimens are conditioned at the specified temperature in a freezer
until they reach equilibrium. The specimens are quickly removed, one at
a time, from the freezer and impacted. Neither ASTM n or ISO specify a
conditioning time or elapsed time from freezer to impact - typical values
from other specifications are 6 hours of conditioning and 5 seconds from
freezer to impact.
Specimen Size:
The standard specimen for ASTM is 64 x 12.7 x 3.2 mm (2½ x ½ x 1/8 inch).
The most common specimen thickness is 3.2 mm (0.125 inch), but the preferred
thickness is 6.4 mm (0.25 inch) because it is not as likely to bend or
crush. The depth under the notch of the specimen is 10.2 mm (0.4 inches).
The standard specimen for ISO is a Type 1A multipurpose specimen with
the end tabs cut off. The resulting test sample measures 80 x 10 x 4 mm.
The depth under the notch of the specimen is 8mm.
Data:
ASTM impact energy is expressed in J/m or ft-lb/in. Impact strength is
calculated by dividing impact energy in J (or ft-lb) by the thickness
of the specimen. The test result is typically the average of 5 specimens.
ISO impact strength is expressed in kJ/m2. Impact strength is calculated
by dividing impact energy in J by the area under the notch. The test result
is typically the average of 10 specimens. The higher the resulting number,
the tougher the material.
Ash Content - back
The Ash Content test is used to determine the amount of fillers in a specimen
after the polymer has been burned off. The ash can be looked at under
a microscope to determine its basic identification such as glass or mineral.
Test Procedure:
Generally, a 2 gram sample is weighed out and placed into a dried crucible.
The sample is then burned in a muffle furnace at 600 degrees C until the
entire polymer has been burned off. The crucibles are then placed into
a desiccator to cool. The ash that is left in the crucibles is then weighed
to give the ash content of the specimen.
Specimen Size:
A 2 gram sample weight is often used.
Data:
Ash content is the weight of the ash divided by the weight of the original
sample multiplied by 100 to give a percentage.
Density - back
Bulk density (see density below) is defined as the
weight per unit volume of material. Bulk density is primarily used for
powders or pellets. The test can provide a gross measure of particle size
and dispersion which can affect material flow consistency and reflect
packaging quantity.
Test Procedure:
A funnel is suspended above a measuring cylinder. The funnel is filled
with the sample and allowed to freely flow into the measuring cylinder.
The excess material on top of the measuring cylinder is scraped off with
a straight edge. The sample and the cylinder is then weighed and the weight
/ volume (Bulk Density) is determined.
Specimen Size:
Powder or Pellets
Data:
Apparent density value is recorded as g/cm3.
Density
Density is the mass per unit volume of a material. Specific gravity is
a measure of the ratio of mass of a given volume of material at 23°C to
the same volume of deionized water. Specific gravity and density are especially
relevant because plastic is sold on a cost per pound basis and a lower
density or specific gravity means more material per pound or varied part
weight.
Test Procedure:
There are two basic test procedures, Method A and Method B. The more common
being Method A, can be used with sheet, rod, tube and molded articles.
For Method A, the specimen is weighed in air then weighed when immersed
in distilled water at 23°C using a sinker and wire to hold the specimen
completely submerged as required. Density and Specific Gravity are calculated.
Specimen Size:
Any convenient size.
Data:
Specific gravity = a/[(a + w)-b]
a = mass of specimen in air.
b = mass of specimen and sinker (if used) in water.
W = mass of totally immersed sinker if used and partially immersed wire.
Density, kg/m3 = (specific gravity) x (997.6)
DSC - back
Using a DSC (differential scanning calorimeter) the following are commonly
found:
Tg = Glass Transition Temperature = The temperature
(°C) at which an amorphous polymer or an amorphous part of a crystalline
polymer goes from a hard, brittle state to a soft, rubbery state.
Tm = melting point = The temperature (°C) at which a crystalline
polymer melts.
Hm = the amount of energy in (joules/gram) a sample absorbs while
melting.
Tc = crystallization point = is the temperature at which a polymer
crystallizes upon heating.
Hc = the amount of energy (joules/gram) a sample releases while
crystallizing. The data can be used to identify materials, differentiate
homopolymers from copolymers or to characterize materials for their thermal
performance.
Test Procedure:
A sample of 10 to 20 mg. in an aluminum sample pan is placed into the
differential scanning calorimeter. The sample is heated at a controlled
rate (usually 10°/min) and a plot of heat flow versus temperature is produced.
The resulting thermogram is then analyzed.
Specimen Size:
A sample weight of 10 to 20 mg is used.
Data:
A thermogram is produced which can provide Tg, Tm, Hm or Hc.
Flexural Test - back
The Flexural test measures the force required to bend a beam under 3 point
loading conditions. The data is often used to select materials for parts
that will support loads without flexing. Flexural modulus is used as an
indication of a material's stiffness when flexed. Since the physical properties
of many materials (especially thermoplastics) can vary depending on ambient
temperature, it is sometimes appropriate to test materials at temperatures
that simulate the intended end use environment.
Test Procedure:
Most commonly the specimen lies on a support span and the load is applied
to the center by the loading nose producing three point bending at a specified
rate. The parameters for this test are the support span; the speed of
the loading; and the maximum deflection for the test. These parameters
are based on the test specimen thickness, and are defined differently
by ASTM and ISO.
Elevated or Reduced Temperature Test Procedure:
A thermal chamber is installed on the Instron universal test machine.
The chamber is designed to allow the test mounts from the base and crosshead
of the Instron to pass through the top and bottom of the chamber. Standard
test fixtures are installed inside the chamber, and testing is conducted
inside the controlled thermal environment the same as it would be at ambient
temperature. The chamber has internal electric heaters for elevated temperatures
and uses external carbon dioxide gas as a coolant for reduced temperatures.
Specimen Size:
A variety of specimen shapes can be used for this test, but the most
commonly used specimen size is 3.2mm x 12.7mm x 125mm (0.125" x 0.5" x
5.0") for ASTM, and 10mm x 4mm x 80mm for ISO.
Data:
Flexural strength, flexural stress at specified strain levels, and flexural
modulus can be calculated.
Mold Shrinkage - back
Mold shrinkage is the shrinkage of the polymer as it cools after the molding
process. It is typically used to properly machine injection molds so that
final part dimensions are as desired. Mold shrinkage can be dependant
upon the molding parameters used - often the extremes of the processing
range for the material plus a midrange value are tested.
Test Procedure:
The length or diameter of the cavity is measured depending on shape of
mold. Test specimens are molded under specified conditions. The parts
cool and after 48 hours, the molded parts are measured and the shrinkage
is calculated.
Specimen Size:
Enough resin to mold the required samples.
Data:
Mold shrinkage is calculated as inches per inch (or percent or mm per
mm) for the specified dimensions and conditions.
The Peel Test - back
The Peel Test measures the strength required to pull apart a bonded surface.
It is useful in evaluating adhesives, adhesive tapes, or other attachment
methods.
Test Procedure:
After the sample is measured for thickness, it is placed in a fixture
in a universal tester. The specimen is pulled at the specified speed until
either the part or the bond fails. Types of failure are noted as cohesive,
adhesive, or substrate failure.
Specimen Size:
Two 6 in. x 1 in. specimens are superimposed on one another and bonded
by adhesive, or other method, in the center.
Data:
Break type - cohesive, adhesive, or substrate. Peel strength.
Tensile Strength - back
Tensile tests measure the force required to break a specimen and the extent
to which the specimen stretches or elongates to that breaking point. Tensile
tests produce a stress-strain diagram, which is used to determine tensile
modulus. The data is often used to specify a material, to design parts
to withstand application force and as a quality control check of materials.
Since the physical properties of many materials (especially thermoplastics)
can vary depending on ambient temperature, it is sometimes appropriate
to test materials at temperatures that simulate the intended end use environment.
Test Procedure:
Specimens are placed in the grips of the Instron at a specified grip separation
and pulled until failure. For ASTM D638 the test speed is determined by
the material specification. For ISO 527 the test speed is typically 5
or 50mm/min for measuring strength and elongation and 1mm/min for measuring
modulus. An extensometer is used to determine elongation and tensile modulus.
Elevated or Reduced Temperature Test Procedure:
A thermal chamber is installed on the Instron universal test machine.
The chamber is designed to allow the test mounts from the base and crosshead
of the Instron to pass through the top and bottom of the chamber. Standard
test fixtures are installed inside the chamber, and testing is conducted
inside the controlled thermal environment the same as it would be at ambient
temperature. The chamber has internal electric heaters for elevated temperatures
and uses external carbon dioxide gas as a coolant for reduced temperatures.
The size of the chamber places a limitation on the maximum elongation
that can be reached, and extensometer are generally limited to no more
than 200° C.
Specimen Size:
The most common specimen for ASTM D638 is a Type I tensile bar. ASTM
D882 uses strips cut from thin sheet or film.
Data:
The following calculations can be made from tensile test results:
1. tensile strength (at yield and at break)
2. tensile modulus
3. strain
4. elongation and percent elongation at yield
5. elongation and percent elongation at break
Equipment used at Plastics Technology Laboratories, Inc.:
Instron Universal Tester Extensometers
Surface Resistivity -
back
Surface resistivity is the resistance to leakage current along the surface
of an insulating material. Volume resistivity is the resistance to leakage
current through the body of an insulating material. The higher the surface/volume
resistivity, the lower the leakage current and the less conductive the
material is.
Test Procedure:
A standard size specimen is placed between two electrodes. For sixty seconds,
a voltage is applied and the resistance is measured. Surface or volume
resistivity is calculated, and apparent value is given (60 seconds electrification
time).
Specimen Size:
A 4-inch disk is preferable, but may be any practical form, such as
flat plates, rods or tubes for insulation resistance.
Data:
Surface and Volume resistivity are calculated.
Surface Resistivity is expressed in ohms (per square)
Volume Resistivity is expressed in ohms - cm
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