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Evaluation of Plasticisers for PVC for Medical Devices

6 Experimental

6.1 Preparation of compounds, films and test specimens

6.1.1 Preparation of PVC compounds plasticised with the selected substances

Approx. 25 kg of test compounds based on each of the selected substances as a plasticiser were prepared and pelletised at Hydro Polymers with the compositions shown in Table 3 below.

As a reference compound a standard DEHP plasticised PVC compound with a Shore A hardness of 80 was chosen, and the Shore A hardness of the test compounds should be as near as possible to 80 for comparison reasons.

Table 3
Formulation of the prepared PVC compounds (parts by weight)

¹) Sources of the ingredients are listed in appendix 3

6.1.2 Preparation by injection moulding of specimens for material characterisation

From the prepared PVC compounds dumbbell shaped tensile test specimens of type 1A according to ISO 527-2:1993 and square test specimens 4 mm thick and 50 mm in side length were made by injection moulding at the Danish Technological Institute.

The detailed injection moulding reports are enclosed as appendix 2.

Table 4 shows the injection moulding parameters used.

Table 4
Parameters used for the injection moulding of dumbbell shaped tensile test specimens and square specimens - zone, nozzle and mould temperatures [ºC]

6.1.3 Preparation by roll milling of film samples for testing

From the prepared compounds 185 - 400 µm thick film samples were made by direct roll milling at PapyroTex.

The temperature of the front roll was 166ºC; the temperature of the back roll was 160ºC. Prior to testing the film samples were conditioned at room temperature for four days.

6.2 Characterisation of the prepared compounds and of the alternative non-PVC material

The test program was conducted at Danish Technological Institute, Centre for Plastics Technology except from the tensile test of film samples, which was performed at the laboratory at Papyro-Tex. The laboratory at Danish Technological Institute, Centre for Plastics Technology is accredited according to DS/EN ISO/IEC 17025 to perform a long range of tests on plastics and similar materials.

6.2.1 Tensile properties determined on injection moulded specimens

Test method: ISO 527-2, specimen type 1A. Crosshead speed 100 mm/min. The detailed test reports are enclosed in appendix 4.

Table 5
Tensile strength and tensile strain at break of injection moulded specimens from PVC test compounds and from a selected grade of EVAC (source information enclosed in appendix 3)

*) No break at this strain
  

Fig. 1
Tensile strength of injection mouldings [MPa]
  

Fig. 2
Tensile strain at break of injection mouldings [%]

6.2.2 Density of the prepared compounds

The density of the prepared PVC compounds and of the alternative plastic material was determined on square injection moulded specimens.

Test method: ISO 2781 method A, ver. 1.

Table 6
Density determined on square injection moulded specimens

Fig. 3
Density [kg/m³]

6.2.3 Indentation hardness determined on square injection moulded specimens

Test method: DS/EN ISO 868:1998 read after 15 seconds.

Table 7
Shore A hardness determined on square injection moulded specimens

*) This value is beyond the interval valid for Shore A
 

Fig. 4
Shore A hardness

6.2.4 Cold flexibility

The cold flexibility temperature was derived from the torsional moduli at varying temperatures determined on plane-parallel specimens cut out from injection moulded tensile test specimens.

Test method: ISO 458/1-1985.

The cold flexibility temperature is defined as the temperature, at which the torsional stiffness, determined by apparent torsional modulus testing, is 310 N/mm at an angular deflection value of 200 degrees.

The resulted graphs are enclosed in appendix 5.

Table 8
Cold flexibility temperature of PVC test compounds and of a selected grade of EVAC determined by testing according to ISO 458/1-1986 [°C]. Also expected values for some compounds are shown.

*) These expected values are derived from ref. 19 and interpolated to the actual hardness values
   

Fig. 5
Cold flexibility tempature [degree C]

6.2.5 Tensile properties determined on roll milled film specimens

Test methods: ISO 527-3, specimen type 2. Width 10 mm, length 150 mm and clamp distance 100 mm. Crosshead speed 200 mm/min.

Prior to testing the film samples were conditioned at room temperature for four days. The mean values were derived from five single values. These tests were performed at Papyro-Tex. The detailed test reports are enclosed in appendix 6.

Table 9
Tensile strength and tensile strain at break of film samples from PVC test compounds. Note: The EVAC material was not available in the form of film.

Fig. 6
Tensile strength of film [MPa]
  

Fig. 7
Tensile strain at break of film [%]

6.2.6 Light transmission determined on roll milled film specimens

Test method: USP XXIV <661> with the exception for the washing and drying of the film samples and with a wider range for the light transmission measurements (290 nm to 800 nm).

Instrument model: Perkin Elmer LAMBDA 18; data interval: 1.0000 nm; scan speed: 240.00 nm/min; slit width: 2.0000 nm; smooth bandwidth: 0.00 nm.

The single light transmission graphs are enclosed in appendix 7.

Table 10
Maximum light transmission at 450 and 800 nm of film samples from PVC test compounds [%]. Note: The EVAC material was not available in the form of film.

¹) Shiny side towards the light source
²) Opposite side towards the light source
³) Read from the graphs
⁴) Calculated electronically by apparatus
  

Fig. 8
Light transmission of film [%]

6.3 Total assessment

Table 12 shows an attempt to make a total assessment

Table 12
Total assessment

Se her!

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