The paper presents the technique of production and characterization of polymer composites based on plasticized PVC and rubber powder from vulcanized nitrile rubber waste. The new polymer composites have lower hardness, higher elongation at break, a better tensile strength, and better ozone resistance, and the blend suitable for irrigations pipes for agricultural use was selected. The selected polymer composites have a good behavior under accelerated aging, repeated flexion at room temperature and at low temperature (−20°C), a very good behavior for immersion in water, concentrated acid and basis, animal fat, soya, and sun flower oil, proving their suitability for gaskets, hoses, protection equipment, rubber footwear, and so forth. The resulted thermoplastic polymer composites can be processed by injection, extrusion, and compression molding.
An efficient reclaiming of wastes resulted from the manufacture of mechanical rubber goods can be achieved by their use in producing composite thermoplastic elastomer materials [
The paper presents our work for producing polymer composites based on plasticized PVC and rubber powder from vulcanized nitrile rubber (NBR) waste and testing their characteristics. It deals with fitting the material characteristics in the standards for materials used for irrigation pipes.
Poly (vinyl chloride) (PVC) is a versatile polymer, used in flexible, semirigid, and rigid forms. In worldwide plastic production, it is second only to polyolefins. The rapid expansion and consumption of PVC is due to lower cost, greater availability, good mechanical properties, and diversity of its properties [
Regarding this aspect, composites based on PVC/vulcanized NBR rubber powder do not need any compatibility agents in order to improve their characteristics.
Materials used to obtain the polymer composites based on plasticized polyvinyl chloride and vulcanized nitrile rubber powder are as follows:
Rubber powder characteristics.
Reference number | Characteristic | Value |
---|---|---|
[ |
Acetone extract, % | 23.86 |
[ |
Ash, % | 19.61 |
[ |
HCl insoluble matter, % | 8.85 |
Polymer composites were obtained in two stages: PVC plasticizing was accomplished by plasticizer (DOP) absorption into PVC when mixing in a 2 L vessel of plasticorder PLV 330 Brabender at 70 rpm, temperature of 40°C for 10 min. For a good thermal stability, temperature stabilizer and antioxidants have been introduced over time. The resulted plasticized PVC is processed into a sheet on a laboratory roll electrically heated, the resulted sheet being used in the next stage in the blend preparation. Preparing the experimental polymer composites based on plasticized PVC and NBR rubber powder on the laboratory electrically heated roller mill. Process variables were as follows: temperature: 140–170°C, friction coefficient: 1 : 1.24. The ingredient addition sequence: plasticized PVC (7–15′), rubber powder (5–10′), homogenization, and removing from the roller mill (3–5′).
Table
Formulations of the polymer composites based on plasticized PVC/vulcanized NBR rubber powder.
Reference number | Ingredients/blends | C1 | C2 |
---|---|---|---|
[ |
NBR rubber powder, g | 75 | 135 |
[ |
PVC, g | 150 | 150 |
[ |
DOP, g | 75 | 75 |
[ |
LGR 8008, g | 6 | 6 |
[ |
Zinc stearate, g | 0.75 | 0.75 |
[ |
Uvinul 5050, g | 1.5 | 1.5 |
The resulted polymer composites were
Mechanical properties of samples were measured on a Schopper tensile tester with a nominal rate of the traverse of the moving grip of 460 mm/min. Modulus at 100% strain, tensile strength, and elongation at break tests were carried out according to the conditions described in ISO 37/2012, on dumb-bell shaped specimens of type 2 (the precision and the uncertainties of the test are ±0.64 for tensile strength and ±2.95 for elongation at break). Tearing strength tests were carried out using angular test pieces (type II) according to SR EN 12771/2003. Hardness of materials was measured using the Shore A scale with samples of 6 mm thickness, by using a hardener tester according to ISO 7619-1/2011 (the precision and the uncertainties of the test are ±0.05). Elasticity was evaluated with a Schob test machine using 6 mm thick samples, according to ISO 4662/2009. Residual elongation is the elongation of a specimen measured 1 minute after rupture in a tensile test. It was calculated using the following formula:
The precision and the uncertainties of the test are ±0.04.
Ozone resistance was determined using a MAST-700-1 device according to SR ISO 1431-1/2002.
For rubber powder, determine the ash in accordance with method a of ISO 247:2006 and determine the acetone extract in accordance with method a of ISO 1407:2011.
All measurements were taken several times and the result values were averaged on three to five measurements.
In Table
Physical-mechanical characteristics for the polymer composites based on PVC plasticized/vulcanized NBR rubber powder.
Reference number | Characteristics/blends | The uncertainties of tests | C1 compression molded sample | C1 injected sample | C2 compression molded sample | C2 injected sample | Limits according to STAS 10040-74 |
---|---|---|---|---|---|---|---|
[ |
Hardness, °ShA, | ±0.05 | 73 | 73 | 71 | 65 |
|
[ |
Elasticity, %, | 7 | 8 | 8 | 10 | ||
[ |
100% modulus, N/mm2 | 5.1 | 4.1 | 3.8 | 2.7 | ||
[ |
Tensile strength, N/mm2 | ±0.64 | 10.6 | 9.7 | 10.4 | 9.5 | Min. 6,37 |
[ |
Elongation at break, % | ±2.95 | 300 | 300 | 393 | 420 | Min. 300 |
[ |
Residual elongation, % | 20 | 21 | 17 | 20 | ||
[ |
Tear strength, N/mm | 56 | 50 | 40 | 46 | ||
[ |
density, g/cm3 | ±0.09 | 1.24 | 1.24 | 1.23 | 1.22 | |
[ |
Resistance to abrasion, mm3 | ±0.15 | 141 | 139 | 139 | 134 | |
[ |
Ozone resistance for 100 h, 30°C, 200 pphm ozone concentration and a 20% tension | No visible cracks under a 2X magnification | No visible cracks under a 2X magnification | No visible cracks under a 2X magnification | No visible cracks under a 2X magnification | No visible cracks under a 2X magnification |
The data in Table
The increase of rubber powder quantity leads to an increase of hardness, 100% modulus, tear strength, and a decrease of elongation at break. Similar modification of characteristics due to the increase of rubber powder quantity was determined also by other researchers [
C1 composite was selected for the production of irrigation hose, and further characterization was conducted in order to determine other fields of use.
The results (Table
Physical-mechanical characteristics for the selected polymer composites.
Reference number | Characteristics | UM | The uncertainties |
Value |
---|---|---|---|---|
[ |
|
|||
Hardness, °ShA, | °ShA | ±0.05 | 75 | |
Elasticity, %, | % | 9 | ||
100% modulus, N/mm2 | N/mm2 | 4,9 | ||
Tensile strength, N/mm2 | N/mm2 | ±0.64 | 9,5 | |
Elongation at break, % | % | ±2.95 | 333 | |
Residual elongation, % | % | 20 | ||
Tear strength, N/mm | N/mm | 52,5 | ||
| ||||
[ |
|
±300 | ||
(i) la −20°C | Flexions | 216000 | ||
(ii) la +23°C | Flexions | >150000 | ||
| ||||
[ |
|
±0.04 | ||
Water 20°C, 22 h | ||||
(i) Change in mass | % | 0 | ||
(ii) Change in volume | % | −0,8 | ||
Water 70°C, 22 h | ||||
(i) Change in mass | % | −1,04 | ||
(ii) Change in volume | % | −0,61 | ||
Sulfuric acid (H2SO4) 70% | ||||
(i) Change in mass | % | 0,29 | ||
(ii) Change in volume | % | −0,55 | ||
Nitric acid (HNO3) 50% | ||||
(i) Change in mass | % | 4,7 | ||
(ii) Change in volume | % | 2,8 | ||
Caustic soda (NaOH) 50% | ||||
(i) Change in mass | % | 0,24 | ||
(ii) Change in volume | % | −0,21 | ||
Sun flower oil | ||||
(i) Change in mass | % | −0,3 | ||
(ii) Change in volume | % | −0,56 | ||
Soya oil | ||||
(i) Change in mass | % | 0,82 | ||
(ii) Change in volume | % | 1,23 | ||
Animal fat | ||||
(i) Change in mass | % | 0,65 | ||
(ii) Change in volume | % | 1,16 | ||
Toluene | ||||
(i) Change in mass | % | 64,6 | ||
(ii) Change in volume | % | 94,6 | ||
Isooctane | ||||
(i) Change in mass | % | 0 | ||
(ii) Change in volume | % | 1,12 | ||
70% isooctane and 30% toluene solution | ||||
(i) Change in mass | % | 12,8 | ||
(ii) Change in volume | % | 22 |
Blending vulcanized nitrile rubber waste powder with plasticized PVC was obtained blends low hardness, high elongation at break, and high tensile strength. Two kinds of composites were produced and characterized in order to select the most suitable for irrigation pipes production. The results show for the selected polymer composites a good behavior to accelerated aging, to repeated flexions at room temperature and low temperature (−20°C), a very good resistance to water, acids and basis, animal fat, sun flower oil, and isooctane. According to these properties the selected blend is suitable to the next fields of use: gaskets, rubber hoses and pipes, rubber footwear, rubber protection equipment.
The resulted polymer composites can be used in the manufacture of a large range of products, like hoses, gaskets, shoe heels, joint packs, slab pavements in sport halls, and so forth, with competitive characteristics as compared to the similar products from virgin materials [
This is an efficient procedure for rubber waste reclamation as a result of polymer composites employed as substitutes for thermoplastics—thus resulting in material savings, rubber waste recycling, no wastes resulted from polymer composite processing, as the fleshes and refuses can be recycled. These composites can be processed by some techniques similar to those for plastics and rubber blends (pressing, injection, extrusion, etc.) [