Study On Melt Cross-linking Reactions Of Waste PVB Films With MF Resin And CaCl2·nH₂O As Well As Their Foaming Properties

In recent years,more and more PVB films have been widely used as interlayer materials for safety glass.Due to the rapid development of these industries,a lot of waste PVB films have been produced.Waste PVB film is non-toxic,odorless,and still with excellent insulation,cold resistance,light resistance,impact resistance and so on.The recycling of waste PVB films could not only reduce environmental pollution,but also gain double benifites of society and economy.In this paper,melamine-formaldehyde resin（MF）and calcium chloride hydrate（CaCl₂·nH₂O）were used as cross-linking agents to react with waste PVB films through melt blending in torque rheometer and two-roll mill respectively.We studied the influence of the blending conditions and raw material ratio on the cross-linked structure and properties of PVB,such as mechanical properties,rheological behavior and thermal properties.The swelling of PVB/MF crosslinked materials in different solvents was investigated to explore the solubility parameters of PVB films.And the dissolution of PVB/CaCl₂ crosslinked materials in different solvents was investigated to study their ability to decrosslink.Furthermore,the two-roll mill was used to blend the crosslinker,foaming agent OBSH with waste PVB film at a lower temperature,and then foamed at high temperature to produce PVB foaming materials.We investigated the effect of the type,content of foaming agent and cross-linking agent on the foam cell morphology,mechanical properties,density,hardness and foaming rate,and tried to investigate the adsorption and buffering performance of some PVB foams.The results are as follows:（1）The waste PVB films and MF resin could be melted and crosslinked in torque rheometer,the crosslinked network formed by the PVB films and MF resin was relatively complete,only swelled and did not dissolve in the solvent.The solubility parameter of PVB films determined by the equilibrium swelling method was 12.1（cal/cm³）^0.5.（2）The waste PVB films and CaCl₂·nH₂O could react and form the coordination crosslinked PVB in two-roll mill under non-liquid conditions.The mechanical properties of PVB/CaCl₂ crosslinked materials improved gradually with the content of CaCl₂·nH₂O;under the premise of maintaining tensile strain at break,the maximum tensile strength and tear strength of PVB/CaCl₂ crosslinked materials were 31.4 MPa and 119.4 kN/m,respectively,which were 40%and 83%higher than those of waste PVB films.（3）PVB/CaCl₂ crosslinked materials were easily decrosslinked at room temperature with a solvent and dissolved in DMF and cyclohexanone solvent.（4）Both cross-linking agents could improve the foaming properties of PVB,and make its cells smaller and more evenly distributed.CaCl₂·nH₂O is more effective than MF.（5）In the PVB/CaCl₂ foaming system,when the content of CaCl₂·nH₂O was 0.5wt%,high foaming materials and low foaming materials could be obtained by controlling the content of OBSH.The low-foaming material had good compression performance and strong ability to absorb energy.The high-foaming material had good adsorption performance for vegetable oil.