Section 66. Actions brought against employers to recover damages for personal injuries or consequential damages sustained within or without the commonwealth by an employee in the course of his employment or for death resulting from personal injury so sustained shall be commenced within twenty years from the date the employee first became aware of the causal relationship between the disability and his employment. In such actions brought by said employees or by the Workers' Compensation Trust Fund pursuant to the provisions of subsection (8) of section sixty-five, it shall not be a defense:
1. That the employee was negligent;
2. That the injury was caused by the negligence of a fellow employee;
3. That the employee had assumed voluntarily or contractually the risk of the injury;
4. That the employee's injury did not result from negligence or other fault of the employer, if such injury arose out of and in the course of employment.