Preparation And Properties Of Rigid Polyurethane Foam Plastics With Thermal Resistance And Heat Insulation Performance

Steam injection is the best and the most extensive way in the thermal recovery of heavy oil.Because there are heat transfer process such as heat conduction,convection and radiation along,the steam heat loss is big.The steam heat used for heating the reservoir is reduced,and the utilization efficiency of steam heat is low.In this paper,in the purpose of reducing heat loss along steam injection in heavy oil reservoirs,the rigid polyurethane foam plastics usually used as heat insulation materials in the areas of buildings and pipelines were modified for improving their end-use temperature to make them meet the requirements of formation temperature.At the same time the materials can be applied to reduce heat loss in strata.In this paper innovative molecular structure was designed to introduce hyperbranched polyol structures into the raw materials of rigid polyurethane foam plastics.One of the objectives was using its high degree of functionality to increase the crosslinking density and hard segment content of the foam matrix.Then the thermal resistance performance and mechanical performance could be improved.The second objective was reducing the viscosity of polyol component taking advantage of the low viscosity of hyperbranched polymer.Then the rigid polyurethane foam plastics were used in cement slurry to impove heat insulation performance of the composite material and keep good mechanical properties.A type of hydroxyl-terminated hyperbranched polyurethane polyol(HBPU)was prepared with isophorone diisocyanate(IPDI)and trimethylolpropane(TMP)by solution polymerization with no catalyst.The influence of reaction temperature and reaction time on NCO conversion rate in the process of producing T3I prepolymer and HBPU were discussed,respectively.The reaction mechanism of hyperbranched polyurethane polyol was studied,and reaction kinetics equation and parameters of the hyperbranched polyurethane polyol were deduced.The molecular structure was characterized by FTIR,1HNMR and 13CNMR.The molecular weight and the distribution of molecular weight were determined by GPC.Thermal stability of hyperbranched polyurethane polyol was analyzed by TGA.The hydroxyl value,viscosity-temperature properties,rheological behavior and dissolution performance were also studied.The experimental results showed that the reaction of HBPU divided into two steps.First,the best reaction conditions of T3I were NCO:OH mole ratio of 2:1,reaction temperature of 80? and reaction time of 60 minutes.Second,the best conditions of HBPU were NCO:OH mole ratio of 1:3,reaction temperature of 80? and reaction time of 120 minutes.The HBPU contained carbamate and hydroxyl groups,with no NCO groups.The molecular structure was hyperbranched polyurethane polyol.The number-average molecular weight(Mn)of HBPU was 1348 g mol-1.The weight-average molecular weight(Mw)was 1702 g mol-1.The polydispersity index was 1.26.The hydroxyl value was 399 mgKOH/g.The average functionality of HBPU was 9.59.The kinetic data indicated the formation obeyed a second order function for HBPU prepolymers and a third order function for HBPU.With no catalyst,autocatalytic effect of urethane group played an important role in HBPU polymerization.The initial decomposition temperature Ts%of HBPU was 196?,and Tmax was 349?.The viscosity of HBPU was 1883 mPa s at 30?.The higher the temperature,the viscosity reduced.Within the scope of 30-70?,the viscosity of HBPU met the requirement of polyol to prepare rigid polyurethane foam.At the same temperature the viscosity of HBPU remained unchanged with the increasing of shear rate(0?50 sec-1).HBPU showed the characteristics of the Newtonian fluid.HBPU was insoluble in water and hexane,slightly soluble in acetone and ethanol,and completely dissolved in tetrahydrofuran and dimethyl formamide.HBPU was not soluble in chloroform at room temperature,but was completely dissolved up to 40?.The rigid polyurethane foam(RPUF)was prepared with polymethyl-polyphenyl isocyanate(PAPI)and HBPU as a polyol component.The influence of catalyst types and amount,foam stabilizer amount,and foaming agent types and amount on the foaming reaction characteristics were discussed.The effects of isocyanate index,polyol types,foaming agent types and amount on the apparent density and heat deformation temperature of RPUF were studied.The micro structures of RPUF,such as cell structure,cell diameter and distribution,were characterized by SEM.The effects of polyol types,foam stabilizer amount,foaming agent types and amount on cell structures of RPUF were discussed.Thermal properties of RPUF,including thermal resistance and thermal stability,were measured by the thermal deformation vicat temperature meter and TGA.Thermal decomposition kinetics of RPUF was studied.Thermal conductivity of RPUF was characterized by Hot Disk,and the mechanical properties were also measured.The results showed that with 100 parts of polyol,the isocyanate index of 1.2,catalyst of 1 part,foam stabilizer of 8 parts,foaming agent water of 1 part,the cream time,rising time and non-stick time of RPUF were moderate.The mass ratio of organic bismuth and triethylenediamine in the 1 part catalyst was 1:1.And the cells of RPUF were fine and uniform.Compared with the RPUF obtained from commercial polyols 4110A and H4110,the apparent density and heat deformation temperature of RPUF made from HBPU were the highest,about 170 kg/m3 and 155?,respectively.The polyhedral butt-joints of the cells were mainly irregular pentagons with large cell diameters,most above 200 ?m.Compared with the RPUF obtained from commercial polyols 4110A and H4110,the RPUF made from HBPU had a compressive strength of 1380 kPa with an increase of about 6 times,a flexural strength of 4162 kPa with an increase of 4 to 6 times,and a tensile strength of 600 kPa with an increase of about 4 times.The RPUF made from HBPU had a low coefficient of thermal conductivity about 0.031 W/(m K)and the thermal diffusion coefficient was 3.05×10-7 m2/s.That met the standards of heat insulation materials and the RPUF had excellent heat insulation performance.The initial decomposition temperature(T5%)of RPUF made from HBPU was 205? and the T50%was 361?.The temperature of maximum weight loss rate Tmax was 341?.The RPUF made from HBPU had good thennal stability.According to the Kissinger method,the apparent activation energy of thermal decomposition of the RPUF made from HBPU was 159.8 kJ/mol.According to the Flynn-Wall-Ozawa method,the thermal decomposition process was divided into three stages.The average activation energy of thermal decomposition at the first stage was 82.8 kJ/mol.The average activation energy of thermal decomposition at the second stage was 140.7 kJ/mol.At the third stage the average activation energy of thermal decomposition was 111.3 kJ/mol.RPUF/cement composite materials were prepared by using the RPUF particles made from HBPU as dispersed phase and the cement inorganic gelatin material as continuous phase.The influence of water-cement ratio,poly-cement ratio,and foam particle size on mechanical properties and thermal conductivity of the composite materials were studied.The effects of temperature on thermal conductivity of the composite materials were discussed.The microstructure of RPUF/cement composite materials was characterized by SEM.The results showed that when the water-cement ratio was 0.35,the apparent density of the RPUF/cement composite material was the highest about 724 kg/m3,and the compressive strength reached the maximum about 3.4 MPa.The apparent density of cement stone without RPUF was 1832 kg/m3,and the compression strength was 8.02 MPa.With the increase of the poly-cement ratio,the apparent density decreased,and the compression strength declined.The change of RPUF particle size had little influence on the apparent density of the composites,but with the particle size increasing,the compression strength of the composite materials slightly reduced.The coefficient of thermal conductivity of the cement stone without RPUF was 0.860 W/(m K),and the thermal diffusion coefficient was 4.96×10-7 m2/s.When RPUF amount was 6%,the coefficient of thermal conductivity of the composite material reduced to 0.077 W/(m K),fell by 91.0%than the pure cement stone.And the thermal diffusion coefficient reduced to 1.45×10-7 m2/s,reduced by 70.8%than the pure cement stone.The coefficient of thermal conductivity and the thermal diffusion coefficient of the RPUF/cement composite materials both had not changed with the rise of temperature.The cohesive strength between RPUF and cement slurry was strong forming a discontinuous,packing tightly,and stereo organic-inorganic compound structure.The composite materials had good integrity and compatibility.