Polymer Testing, Polymer Analysis, Plastic Testing, and Plastic Analysis by ExcelPlas
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Acrylic – Panels

Title

CRACKED ACRYLIC PANELS

Date

2012

Objective

To investigate the root cause of cracking of acrylic panels used as decorative cladding panels on a foot bridge in NZ.

Photo

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Figure 1. Cracking around mounting holes

 

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Figure 2. Resistance to ESC. Cracking observed on bent strip only where adhesive film was applied

Testing Undertaken

Failure Analysis Methodology (Scheirs 2000)

Determination of Resistance to Environmental Stress Cracking (ESC) ISO 22088-3: 2006

GC/MS

Failure Analysis

Cracking of the acrylic sheet was typical of ESC and Cyclic Stress Loading (CSL).

Computer modelling showed that the panels were subjected to high strains concentrated around the mounting holes due to thermal stresses andwind gusting in service.

The adhesive backed decorative film applied to the acrylic panels was the most likely root cause of the stress cracking owing to the various potent stress cracking chemicals detected in it.

 

Acrylonitrile butadiene styrene (ABS) – Mesh for work platforms

Title

UV RESISTANCE TESTING

Date

2012

Objective

To further study the UVResistance of two different supplied plastics samples

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Figure 1a and 1b. Grey Mesh after UV exposure showing slight discolouration

 

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Figure 1a and 1b. Yellow Mesh after UV exposure showing slight discolouration

Testing Undertaken

Strips of mesh that had previously undergone accelerated UV aging were re-loaded into a QLabs UV Weatherometer and exposed to a second period of accelerated UV aging. The samples were then visually inspected.

Failure Analysis

Visual inspection of both the grey and yellow mesh samples showed some dis-coloration but no evidence of substantial polymer degradation.

 

Acrylonitrile butadiene styrene (ABS) – Mouldings
(1 of 3)

Title

CAUSE OF CRACKING ON AN ABS ASSEMBLY

Date

2013

Objective

To determine the cause for the cracking of an ABS drain assembly

Photo

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Figure1. Sample showing major lateral crack

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Figure 2. Sample showing cracks at side of moulding

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Figure 3. Magnified image of side cracks

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Figure 4. Detailed image of crack structure

Testing Undertaken

Infrared measurement to determine relative quantities of acrylonitrile in materials

Visual assessment of nature of cracks using microscope at various magnification.

Failure Mode

The moulding cracked due to environmental stress cracking caused bycyclohexanone in the adhesive used during assembly.

IR-spec indicated no deficiency in acrylonitrile content.

 

Acrylonitrile butadiene styrene (ABS) – Mouldings
(2 of 3)

Title

DEFECTS IN ABS USED FOR PLATING

Date

2013

Objective

To investigate the origin of defects in ABS mouldings used for plating

Photo

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Figure 1. Sample 5

Testing Undertaken

Microtoming

Grazing Angle Optical Microscopy (GAOM)

SEM

Microprobe Elemental X-ray Analysis (EDAX)

Failure Analysis

The defects in the ABS mouldings and plated ABS could be attributed to: carbonized black specks rich in bromine (poorly purged extruder), and blue pigment particles based on ultramarine blue (poorly purged extruder). The black specs may also be related to the use of recycled ABS which has additional heat histories

 

Acrylonitrile butadiene styrene (ABS) – Mouldings
(3 of 3)

Title

DEFECTS IN ABS USED FOR PLATING

Date

24 May 2013

Objective

To investigate the origin of defects in plated ABS mouldings.

Photo

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Figure 1. Sample 26 (Chrome Plated)

Testing Undertaken

Microtoming

Grazing Angle Optical Microscopy (GAOM)

SEM

Microprobe Elemental X-ray Analysis (EDAX)

Failure Analysis

The defects in the plated ABS could be attributed to: pimples formed by surface bubbles (due to gas evolution from surface contamination or hydrogen bubbles) and silica or sand contamination (on one sample).

 

Crosslinked polyethylene (PEX) – Hot water pipe (1 of 2)

Title

FAILURE ANALYSIS OF PEX HOT WATER PIPE

Date

2013

Objective

To conduct a failure analysis on samples of PEX pipes that have cracked in service (a hot water system)

Photo

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Figure 1. Sample internal surface (Low Mag.)

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Figures 2. Internal cracks on sample (40x Mag.)

Testing Undertaken

Wall thickness measurements

Photomicroscopy

ATR-FTIR

Carbonyl Index per ASTM F2102

OIT by DSC per ASTM D3895

Degree of crosslinking per AS2492

Failure Mode

The inner surface of the PEX pipe is totally degraded and embrittled down to ~ 2/3rd total
wall thickness. The PEX pipe has undergone a Stage III failure which is caused by depletion/extraction of its antioxidants.

 

Crosslinked polyethylene (PEX) – Hot water pipe (2 of 2)

Title

CRACKING OF PEX HOT WATER PIPE

Date

2013

Objective

To investigate the cause of failure of a sample of PEX black hot water pipe

Photo

 

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Figure 1. Pipe showing brittle slit failure

 

 

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Figure 2a and 2b. SEM Photo of fracture surface through wall of pipe

Testing Undertaken

SEM

Fractographic analysis

OIT (per ASTM D-3895)

Failure Analysis

The pipe failed prematurely by Fatigue Crack Propagation  initiated at the inner surface.

 

Elastomer – Safety wear (kneepads)

Title

FLEX CRACK TESTING OF KNEEPADS

Date

2013

Objective

To investigate the flex fatigue crack resistance of two kneepads.

Photo

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Figure 1. Failure after 1,000,000 flex cycles

Testing Undertaken

Flex cracking resistance of rubbers and elastomers by AS 4878.9-2001

Conclusion

Delamination failure was observed for the rectangular knee pad at the interface between the black rubber and the grey foam after 1,000,000 cycles.

 

Epoxy – Castings

Title

ASSESSMENT OF A CRACKED EPOXY CASTING

Date

2013

Objective

To assess the cause of cracking in a moulded epoxy casting.

Photo

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Figure 1. Crack in Casting

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Figure 2. Close up of crack in moulding

Testing Undertaken

Failure analysis

Failure Mode

Temperature at time of mixing components estimated to be as high as 50°C, possibly causing the reaction to proceed four times faster than normal and generate four times as much heat. This could create a crack due to the thermal stresses generated.

 

Epoxy – Sewer Pipes

Title

FAILURE ANALYSIS OF COLLAPSED POLYMER LINER IN SEWER PIPE

Date

2012

Objective

To investigate the cause of failure of an epoxy liner in a sewer relining application

Photo

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Figure 1. Photograph of failed liner in situ

 

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Figure 2. Photograph of cured reference liner

 

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Figure 3. Photograph of recovered liner section

Testing Undertaken

DSC Thermal Analysis

IR-Spec

Durometer Shore D Hardness Measurements

Failure Analysis

There were some dry felt areas on the recovered liner, thus indicating resin poor zones suggesting the liner may not have been properly impregnated with epoxy resin. The cured liner has limited stress resistance and thus should not be in a load bearing service application as it lacks ring crush resistance and buckling resistance

 

 

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Contact Us

Polymer Testing (Division of ExcelPlas)

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Moorabbin VIC 3189

Postal Address
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Moorabbin VIC 3189

e. info@polymertesting.com.au
p. 03 9532 2207

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