Preparation method of grafted fibrilia modified and reinforced composite material

[0024] The preparation method of the hemp fiber reinforced resin-based composite material of the present invention is suitable for raw hemp, refined hemp, yarn or fabric of ramie fiber, flax fiber or sisal fiber. First, pre-treat the hemp fiber, including degumming, degreasing and alkali treatment; then graft the treated fiber with diisocyanate; then use weaving technology to weave the hemp fiber into a fiber bundle or fabric, or first weave the hemp fiber into a fiber The bundle or fabric is then grafted with diisocyanate; finally, it is compounded with resin to prepare a composite material.

[0025] The degumming in the pre-treatment can be complete or incomplete degumming, both of which adopt the existing conventional textile hemp degumming process; the degreasing treatment is to soak natural hemp fiber in acetone for 10h-25h; alkali treatment is to make natural hemp fiber at a concentration of 5wt% Soak in ~25wt% NaOH aqueous solution for 10h-30h, and then wash with water to neutral (pH=7).

[0026] The grafting of hemp fiber and diisocyanate is adopted: the pre-treated hemp fiber is added to the acetone solution according to the bath ratio of 1:25~35, and then the diisocyanate is added. The dosage ratio of diisocyanate (ml) to hemp fiber (g) is 1~4:1~4, using strong inorganic acid as catalyst to make the reaction pH between 2~3, ultrasonic heating at 50~70℃, after reaction for 4~15h, wash away the diisocyanate adsorbed on the fiber with acetone and dry , The grafted hemp fiber is obtained, and the diisocyanate can be toluene-2.4-diisocyanate, toluene-2.6-diisocyanate, hexamethylene diisocyanate or lysine diisocyanate.

[0027] The existing textile technology is used for grafting and then weaving or weaving and then grafting to obtain continuous long fiber bundles or fabric structure reinforcement.

[0028] The continuous long fiber reinforced resin-based composite material is prepared by the conventional composite material molding process such as hot pressing, that is, natural hemp fiber reinforced resin-based composite material is prepared.

[0029] Example 1

[0030] The completely degummed ramie fiber (refined dried hemp), soaked in 15wt% NaOH aqueous solution for 24h, washed with water until the pH is neutral (pH=7), dried under vacuum at 60°C for 4~5h, soaked in acetone solution for 24h for degreasing, then put it in In the reactor, add acetone solution with a bath ratio of 1:30, and then add toluene-2.4-diisocyanate. The ratio of toluene-2.4-diisocyanate (ml) to hemp fiber (g) is 2:1. Sulfuric acid, make the pH between 2 and 3; heating in an ultrasonic water bath, keeping the reaction temperature at 50℃, reaction time 10h, grafting rate 45%, take out the ramie fiber, wash with acetone to remove unreacted toluene-2.4-diisocyanate, wash with water , Dried at 80°C; woven into yarn or textile structure reinforcement, and unidirectionally laid with 0.06mm polyethylene (PE) film barrier; 125°C, 1.5MPa hot press molding, 105°C annealing for 2h to obtain ramie fiber reinforced PE composite material The board has a strength of 190MPa after testing.

[0031] Example 2

[0032] The flax fiber bundle after degumming and weaving is soaked in 10wt% NaOH aqueous solution for 25h, washed with water until the pH is neutral (pH=7), dried under vacuum at 60℃ for 4~5h, soaked in acetone solution for 25h for degreasing, and then placed in the reactor Add acetone solution with a bath ratio of 1:25, then add toluene-2.6-diisocyanate, the dosage ratio of toluene-2.6-diisocyanate (ml) to hemp fiber (g) is 1:1, drop concentrated sulfuric acid, Make pH=2~3, heat in ultrasonic water bath, keep reaction temperature 65℃, reaction time 6h, grafting rate 39%, take out flax fiber, wash with acetone to remove unreacted toluene-2.6-diisocyanate, wash with water, 80 Dry at ℃, and lay unidirectionally with a 0.06mm polyethylene (PE) film barrier; hot press at 125℃, 1.5MPa; annealing at 105℃ for 2h to obtain a flax fiber reinforced PE composite board. After testing, its strength is 185MPa.