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		Technical Information Introduction Stacking Rough Handling Miscellaneous Introduction Back to top of page Twin-wall Polypropylene board is a one-piece extrusion of two layers of ethylene/propylene copolymer separated by Ribbing. It is a sheet which is tough and easy to work. The physical properties of Twin-wall Polypropylene all show that the material is particularly suited to rough handling conditions. High tensile and impact strength readings, together with good compression strength results demonstrate the ability of Twin-wall Polypropylene to withstand considerable edge crushing blows and drops - even after being fully crushed the Twin-wall Polypropylene flutes have a tendency to return to their original configuration and thus provide some cushioning against further blows or drops. A copolymer of ethylene and propylene has been used in order to increase toughness and improve low temperature performance, as compared with a propylene homo polymer. However, the copolymer has been carefully chosen to ensure that the extremely high flex resistance properties associated with polypropylene are still remaining unaffected at ambient temperatures by most oils, solvents and water. Hence it will perform extremely well under unfavourable weather conditions and in areas of high relative humidities. It has been established that Twin-wall Polypropylene can be nailed or bolted to other constructions quite satisfactorily. In addition it can be cut, scored, stitched, slit, diestamped and taped using normal box-making equipment. Letterpress and flexographic methods have been used to print Twin-wall Polypropylene and work is in hand to increase efficiencies with these processes. Printing on Twin-wall Polypropylene using the silk screen process has proved most successful. The information given on these pages has been compiled from a variety of sources. In several sections here, Twin-wall Polypropylene has been compared with B Flute fibreboard, not because Twin-wall Polypropylene is expected to directly replace fibreboard, but because B Flute fibreboard is a convenient "standard product" with which to make comparisons. The figures quoted are "typical" results and are not intended to constitute any specification. It is advisable, therefore, to use this information as a general guide to the properties that can be expected from Twin-wall Polypropylene and to carry out confirmatory tests relevant to each particular application. Stacking Back to top of page Actual stack loads on corrugated fibreboard cases are normally recommended to be the compression strength divided by a factor of 1.5 - 4.5 depending on the storage conditions. Tests carried out with Twin-wall Polypropylene indicate that a factor of the order of 2.5 - 3.5 will probably be adequate over normal temperature ranges. Although the stacking performance of Twin-wall Polypropylene can be reduced by extreme temperatures, it is unaffected by changes in humidity. The stacking performance of fibreboard, of course, falls off markedly with the increasing board moisture content which will result from high humidity conditions. Test Results Regulation Style Cases and cases with locking bases were tested at 23°C and 50% relative humidity. Compression was top to bottom. Twin-wall Polypropylene B Fluted Fibreboard Regulation Style 2.45 kN @ 1.14cm 1.87 kN @ 0.46cm Locking Base 2.58 kN @ 0.76cm 2.28 kN @ 0.38cm   Average load to failure (kN) and deflection (cm). Rough Handling Back to top of page The rough handling characteristics of Twin-wall Polypropylene compare well with those of fibreboard. Materials tests show that Twin-wall Polypropylene has significantly higher burst, puncture and edge and flat crush properties than B Flute fibreboard. However, the machine direction stiffness of Twin-wall Polypropylene is lower than that of fibreboard at normal humidities. At high humidities, the materials test results of the fibreboard would be significantly affected whereas those of Twin-wall Polypropylene would not. Test Results (average values are quoted) 1. Bursting Strength - BS 1133. SEC F. APP. M. (1967)   * Twin-wall Polypropylene:   Turnover 0.00 2. Impact Strength - ASTM D-781-59T   4/710 4/800 Twin-wall @ 23°C 1.6J 1.8J Polypropylene @ 20°C 1.1J 1.3J   Drop Hammer Indentation Test Twin-wall Polypropylene B Flute Fibreboard Peak stress to crush flutes 450-1200 kN/m2 500-750 kN/m2 Energy to crush flutes approx 1300 J/m2 1000-1100 J/m2   Drop Hammer Deceleration Test   Using 31.66 cm2 circular indentor   Static stress - 2.97 kN/m2   Drop Height   Peak Deceleration in Gravitation Units (mm) Drop 1 Drop 2 Drop 3 Drop 4 Drop 5 Drop 6 Drop 7   150 Sample 1 125 150 >300 Sample 2 150 215 240 >300 Sample 3 440 350 260 260 530*   300 Sample 1 355 140 220 265 >1000* Sample 2 410 200 280 380 380 920 Sample 3 225 200 270 312   Sample 1   470*   930*   >1000* Sample 2 385 555* 490* 660* 865* 880* >1000*   *Flutes fully crushed on impact   Miscellaneous Back to top of page Light Transmission (average values are quoted) Twin-wall Polypropylene: 75% 3mm Glass: 90%   Level of Surface Treatment (to improve print adhesion) Twin-wall Polypropylene: 45 dynes/cm   Coefficient of Linear Thermal Expansion Twin-wall Polypropylene: 1.1 x 10-4 per °C   Thermal Transmittance 4.27 (Max) to 2.42 (Min) - W/m2 per °C 0.75 (Max) to 0.43 (Min) - BTU/ft2h°F   3. Tensile Strength - ASTM D-828-60   4/710   4/800 Twin-wall Polypropylene Yield Point  4560 kN/m2 5200 kN/m2 Break Point  23500 kN/m2 27000 kN/m2 Elongation at Break  166% 166% Cushioning   Cushioning tests show that prior to complete crushing of the Twin-wall Polypropylene flutes, the peak decelerations are in the range 150-400g. The acceleration time pulses show that even when fully crushed on a preceding drop, the Twin-wall Polypropylene fluting resists subsequent compression, and hence provides some cushioning. Twin-wall Polypropylene is less easily compressed under both static and dynamic conditions than B Flute fibreboard, a higher stress is needed to crush the flutes, and higher energy is absorbed. This means that Twin-wall Polypropylene will cushion slightly heavier items or from higher drops. As the range of values shows, the amount of cushioning is highly dependent on flute formation. Low Speed Compression 4/710 4/800 Twin-wall Polypropylene Flat Crush Strain 1.04% 1.09% Compression 64 kN/m2 72 kN/m2 Compression to completely crush flutes 500-860 kN/m2* Energy to completely crush flutes 700-1050 J/m2** (* values for B Flute fibreboard: 100-300 kN/m2) (**values for B Flute fibreboard: 250-540 J/m2) Along Flutes Strain Compression 2.37% 1930kN/m2 2.50% 2200kN/m2 Across Flutes Strain Compression 1.70% 147kN/m2 1.80% 168kN/m2   Chemical Properties A. Resistance to Organic Chemicals (duration of test 90 days)   Reagent   Temperature 20°C 60°C Acetic Acid (1 0%) Nil Nil Acetone Nil Nil Ammonium Hydroxide (10%) Nil Nil Benzene Slight Moderate Carbon Tetrachloride Moderate Severe Citric Acid (1 0%) Nil Nil Cyclohexanol Nil Slight Detergent (liquid 2%) Nil Nil Ethanol (96%) Nil Nil Glycerine Nil Nil Isopropyle Alcohol Nil Nil Lactic Acid (20%) Nil Nil Methanol Nil Nil Methyl Ethyl Ketone Nil Slight Nitrobenzene Nil Nil Turpentine Slight Moderate Xylene Moderate Severe Paraffin Nil Nil Petroleum Spirit Nil Nil Lubricating Oil (Mobil DTE) Nil Nil Hydraulic Fluid (Aeroshell DTD585) Nil Nil Ester based Lubricated Oil (Aeroshell 2487) Nil Nil Phosphate Ester Hydraulic Fluid (Skydrol) Nil Nil   B. Resistance to Inorganic Chemicals (duration of test 90 days)   Reagent   Temperature 20°C 60°C Ammonium Hydroxide (10%) Nil Nil Hydrochloric Acid (30%) Nil Nil Hydrogen Peroxide (10%) Nil Slight Nitric Acid (70%) Slight Moderate Phosphoric Acid (85%) Nil Nil Potassium Hydroxide (50%) Nil Nil Sodium Hydroxide (50%) Nil Nil Sulphuric Acid (98%) Nil Moderate Sulphuric Acid (10%) Nil Nil Water Nil Nil Nil - Negligible effect Slight - Some attach, but function of part unimpaired Moderate - Satisfactory for some applications Severe - Unacceptable   C. Resistance to Mould Growth(duration of test 28 days) Growth of mould, such as aspergillus niger, is not supported. The information given here is based on our general experience and is given in good faith, but because of the many particular factors which are outside our knowledge and control and affect the use of Twin-wall Polypropylene, no warranty is given or is implied with respect to such information.

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