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Investigation of polymer properties after plastic deformation under pressure
Physica 139 & 140B (1986) 629-630 North-Holland, Amsterdam
INVESTIGATION OF POLYMER PROPERTIES AFTER PLASTIC DEFORMATION UNDER PRESSURE B.I. BERESNEV and N.V. SHISHKOVA Physico-Technical Institute, Academy of Sciences of the Ukr.SSR, 340114 Donetsk, ul. R. Luxemburg 72, USSR
S.A. T S Y G A N K O V Union "'PLASTOPOLYMER", Leningrad, Polustrovsky avenue 32, USSR
The data on hydrostatic extrusion and the properties of extruded thermoplastic polymers such as fluoroplastics, polyolefins, ABC-plastics are presented. It was found that the hydrostatic extrusion had a strong effect on the increase of the elasticity and strength of the polymers due to rearrangment of their initial structure. The question of the production of high-strength and high-modulus articles based on the studied thermoplastic polymers has been investigated.
1. Introduction
During the last few years the research aimed at the creation of the high-strength and highmodulus materials based on highly-oriented polymers has become increasingly important. The production technology for highly-oriented polymers is developing in two ways. Polymer orientation in a solution or melt by drawing with the consequent or simultaneous crystallization and orientation in the solid polymer systems by directed plastic deformation. The second way seems to be more interesting due to the great number of technological advantages for the production of various highlyoriented and high strength articles, made of complex shaped polymers. From this point of view the following techniques are the most likely: solid phase piston and hydrostatic extrusion, rolling, drawing and stamping.
2. Experimental
The deformation of materials as involved in these methods, takes place in the combined stressed state condition and the hydrostatic stress tensor component is rather big. The presence of the hydrostatic pressure during orientational deformation allows substantial single drawings of polymer materials without the usual failure
accompanying this method. So, the highlyoriented state may be implemented in the great bulk of a polymer material, providing the possibility to produce various high-strength and highmodulus articles. We have carried out a number of studies on the technological polymer deforming peculiarities by the above-mentioned methods. The polymer properties and structure were also studied. As the subjects of the study we employed: polyolefinsHDPE, LDPE, polypropylene (PP), poly-4methyl-pentene (PMP); fluoropolymers - PTFE, F-4MB, F-2, F-3, F-40P, F-50; styrene plasticspolystyrene (PS); high-impact polystyrene (HIPS); ABC-plastics, polyamides PA-6 and PA-12 and a number of composite polymerpolymer compounds and highly-filled systems. Deformation was performed over a wide temperature range: from room temperature to the melting point of thermoplastics. The percentage reduction of the material determined by the area ratio of the initial and deformed billet was as follows: for HDPE, 30; LDPE, 6; PP, 15; PMP, 10; for fusible fluoropolymers, 8; PTFE, 4; PA-6 and PA-12, 6. Polystyrene plastics may be deformed with the stretch ratio from 3.5 to 6. The increase of transparency, strength and rigidity was characteristic for all the tested materials. The elasticity increase (fig. 1, elasticity modulus at stretching) was 100 times as
0378-4363/86/$03.50 (~ Elsevier Science Publishers B.V. (North-Holland Physics Publishing Division)
630
B. 1. Beresnev et al. / Investigation of polymer properties after plastic deformation 300 ~00 6O
S/
f[ 40 3O
20 4 0
f
et~ R
2
Fig. 1. Effect of the degree of deformation (In R) on the elasticity modulus for the various polymer materials: 1, HDPE; 2, LDPE; 3, PMP; 4, PP; 5, PTFE; 6, F-2; 7, F-40; 8, ABC; 9, PS; 10, HIPS.
large for HDPE, for LDPE 7 times, for PP 9 times, for fluoropolymers 1.5-2 times, for polyamides 8 times, for polystyrene plastics 1.5 times. These high-elasticity characteristics of the materials studied occur over a wide range of temperature up to the melting point, for all the materials studied, excluding the polystyrene plastics, elongation at rupture, creep and other deformation characteristics decreased. Thermal shrinkage of the highly-oriented billets occurs only at annealing close to their melting point. The value of this shrinkage for HDPE, PP and PMP did not exceed 10-15%; for the fluoropolymers, LDPE and polystyrene plastics the annealing at temperatures close to the melting point, resulted in rather appreciable shrinkage (about 40%). This phenomenon may be used for the production of thick-walled tubing, rings etc. by thermoshrinking and thermoexpanding. The data of, the X-ray analysis and optical microscopy were used to study the structure of the materials. For the partially crystalline polymers the deforming in the range of high compressive stress results in the rearrangement of the initial spherulite structure and the formation of a
Fig. 2. Articles produced by the hydrostatic extrusion method.
fibrillar structure with a highly-dense amorphous interfibrillar interlayer. Completely straightened molecules have not been observed. The structure of polystyrene plastics (ABC and HIPS being subjected to cubic strain) was studied by optical microscopy. The elastomer phase shape changed from spherical to cylindrical-extended for these materials. So, they may be considered as laminar substances characterized by the corresponding variation in properties. A number of articles produced by the cubic strain method are shown in fig. 2. Transparency and rigidity are the characteristic properties of these articles in comparison with those produced by conventional casting and extrusion.
3. Conclusion
The methods discussed above add substantially to the existing methods of the formation of plastics and we think they will be widely used in the near future.
INVESTIGATION OF POLYMER PROPERTIES AFTER PLASTIC DEFORMATION UNDER PRESSURE B.I. BERESNEV and N.V. SHISHKOVA Physico-Technical Institute, Academy of Sciences of the Ukr.SSR, 340114 Donetsk, ul. R. Luxemburg 72, USSR
S.A. T S Y G A N K O V Union "'PLASTOPOLYMER", Leningrad, Polustrovsky avenue 32, USSR
The data on hydrostatic extrusion and the properties of extruded thermoplastic polymers such as fluoroplastics, polyolefins, ABC-plastics are presented. It was found that the hydrostatic extrusion had a strong effect on the increase of the elasticity and strength of the polymers due to rearrangment of their initial structure. The question of the production of high-strength and high-modulus articles based on the studied thermoplastic polymers has been investigated.
1. Introduction
During the last few years the research aimed at the creation of the high-strength and highmodulus materials based on highly-oriented polymers has become increasingly important. The production technology for highly-oriented polymers is developing in two ways. Polymer orientation in a solution or melt by drawing with the consequent or simultaneous crystallization and orientation in the solid polymer systems by directed plastic deformation. The second way seems to be more interesting due to the great number of technological advantages for the production of various highlyoriented and high strength articles, made of complex shaped polymers. From this point of view the following techniques are the most likely: solid phase piston and hydrostatic extrusion, rolling, drawing and stamping.
2. Experimental
The deformation of materials as involved in these methods, takes place in the combined stressed state condition and the hydrostatic stress tensor component is rather big. The presence of the hydrostatic pressure during orientational deformation allows substantial single drawings of polymer materials without the usual failure
accompanying this method. So, the highlyoriented state may be implemented in the great bulk of a polymer material, providing the possibility to produce various high-strength and highmodulus articles. We have carried out a number of studies on the technological polymer deforming peculiarities by the above-mentioned methods. The polymer properties and structure were also studied. As the subjects of the study we employed: polyolefinsHDPE, LDPE, polypropylene (PP), poly-4methyl-pentene (PMP); fluoropolymers - PTFE, F-4MB, F-2, F-3, F-40P, F-50; styrene plasticspolystyrene (PS); high-impact polystyrene (HIPS); ABC-plastics, polyamides PA-6 and PA-12 and a number of composite polymerpolymer compounds and highly-filled systems. Deformation was performed over a wide temperature range: from room temperature to the melting point of thermoplastics. The percentage reduction of the material determined by the area ratio of the initial and deformed billet was as follows: for HDPE, 30; LDPE, 6; PP, 15; PMP, 10; for fusible fluoropolymers, 8; PTFE, 4; PA-6 and PA-12, 6. Polystyrene plastics may be deformed with the stretch ratio from 3.5 to 6. The increase of transparency, strength and rigidity was characteristic for all the tested materials. The elasticity increase (fig. 1, elasticity modulus at stretching) was 100 times as
0378-4363/86/$03.50 (~ Elsevier Science Publishers B.V. (North-Holland Physics Publishing Division)
630
B. 1. Beresnev et al. / Investigation of polymer properties after plastic deformation 300 ~00 6O
S/
f[ 40 3O
20 4 0
f
et~ R
2
Fig. 1. Effect of the degree of deformation (In R) on the elasticity modulus for the various polymer materials: 1, HDPE; 2, LDPE; 3, PMP; 4, PP; 5, PTFE; 6, F-2; 7, F-40; 8, ABC; 9, PS; 10, HIPS.
large for HDPE, for LDPE 7 times, for PP 9 times, for fluoropolymers 1.5-2 times, for polyamides 8 times, for polystyrene plastics 1.5 times. These high-elasticity characteristics of the materials studied occur over a wide range of temperature up to the melting point, for all the materials studied, excluding the polystyrene plastics, elongation at rupture, creep and other deformation characteristics decreased. Thermal shrinkage of the highly-oriented billets occurs only at annealing close to their melting point. The value of this shrinkage for HDPE, PP and PMP did not exceed 10-15%; for the fluoropolymers, LDPE and polystyrene plastics the annealing at temperatures close to the melting point, resulted in rather appreciable shrinkage (about 40%). This phenomenon may be used for the production of thick-walled tubing, rings etc. by thermoshrinking and thermoexpanding. The data of, the X-ray analysis and optical microscopy were used to study the structure of the materials. For the partially crystalline polymers the deforming in the range of high compressive stress results in the rearrangement of the initial spherulite structure and the formation of a
Fig. 2. Articles produced by the hydrostatic extrusion method.
fibrillar structure with a highly-dense amorphous interfibrillar interlayer. Completely straightened molecules have not been observed. The structure of polystyrene plastics (ABC and HIPS being subjected to cubic strain) was studied by optical microscopy. The elastomer phase shape changed from spherical to cylindrical-extended for these materials. So, they may be considered as laminar substances characterized by the corresponding variation in properties. A number of articles produced by the cubic strain method are shown in fig. 2. Transparency and rigidity are the characteristic properties of these articles in comparison with those produced by conventional casting and extrusion.
3. Conclusion
The methods discussed above add substantially to the existing methods of the formation of plastics and we think they will be widely used in the near future.