Preparation And Properties Of Cashew Nut Shell Liquid Modified Novalac Phenolic Resin And Its Molding Materials

In this paper, the synthesis and the properties of the cashew nut shell liquid (CNSL) modified Novalac phenolic resin are studied. Also the molding composite materials based on the cashew nut shell liquid (CNSL) modified phenolic resin are prepared and their properties are studied. The reaction process stability for the synthesis of the CNSL modified Novalac phenolic resin was related to the mole ratio of phenol and formaldehyde, the adding amount of the catalyst and the cashew nut shell liquid respectively. The molding composite materials were prepared with a series of cashew nut shell liquid (CNSL) modified phenolic resin which were prepared by changing the mole ratio of phenol and formaldehyde; the adding amount of cashew nut shell liquid correspondingly, and the mechanical properties of cashew nut shell liquid (CNSL) modified phenolic molding composite materials were also investigated and were compared with the common Novalac phenolic resin based molding composite material.The synthesis and properties of the CNSL modified Novalac phenolic resins were studied. The FT-IR and ¹³C-NMR techniques were used to analyse the structure of the CNSL modified phenolic resin, the average molecular weight was also obtained by using the GPC technique. It was found that the mole ratio of phenol and formaldehyde had a great effect on the reaction system stability of the CNSL modified Novalac phenolic resin. When the mole ratio of formaldehyde and phenol was in the range of 0.84-0.87, the temperature changing of the reaction system was appropriate, the reaction system for the whole process was stable. The adding amount of the catalyst also had influence on the reaction system stability. It was found that the reaction system remained stable when the pH value of the system was 2.0-2.5. The adding amount of cashew nut shell liquid had little effect on the reaction system stability of the CNSL modified Novalac phenolic resin. The mole ratio of formaldehyde and phenol also had great effect on the properties of the CNSL modified Novalac phenolic resin. When the mole ratio of formaldehyde and phenolwas more than 0.85, the soft point of the CNSL modified Novalac phenolic resin was appropriate; the content of free phenol was lower than 5%.The isothermal DSC and dynamic DSC technique were used to analyse the curing characteristics of the CNSL modified Novalac phenolic resin. The results showed that the curing activation energy of CNSL modified Novalac phenolic resin rised according to the increased adding amount of cashew nut shell liquid, the curing speed of CNSL modified Novalac phenolic resin was lower than that of Novalac phenolic resin. The thermal degradation of the CNSL modified Novalac phenolic resin was analysed by using the TGA technique. The thermal degradation of CNSL modified Novalac phenolic resin depended on the adding amount of cashew nut shell liquid. When the adding amount of cashew nut shell liquid was 10%, the thermal degradation of CNSL modified Novalac phenolic resin behaved as that of the common Novalac phenolic resin.The mechanical properties, dielectric property, thermal property of the molding composite materials based on CNSL modified phenolic resin were studied respectively. The notched impact strength and the flexural strength increased first and then reduced with the increase of the adding amount of the cashew nut shell liquid in the modified phenolic resin, yet the thermal distortion temperature reduced with the increase of the content of the cashew nut shell liquid in the resin, the dielectric strength increased with that too. When the adding amount of cashew nut shell liquid is 10%, the flexural and the notched impact strengths were increased by 14.8% and 10.7% separately, the dielectric strength is 25% higher, yet the thermal distortion temperature is only 1.9% less than that of the common Novalac phenolic resin.