Parfor loop for simulink

HI, I'm trying to run a simulink model from parfor loop. However the output generated from the loop seems to be identical when input variables changed.

I simulated this using sim command and for loop. The output is as expected. Could someone please help me to correct the parfor script.

Simulink and matlab scripts attached.

Parfor loop code:

%' M-File script to plot simulation data '
%%Load System
clc;clear all;
%  load_system('sine');  % move to parfor loop

%%Define Parameter sets
Volts = (1:2:20); % set voltage amplitude;
f = 2 ; % set simulation values for 2hz
iterations=numel(Volts);
simout =cell(1,iterations);

%%Run the sim command
tic 
parfor k = 1:iterations
load_system('sine');
set_param('sine/Amplitude','Gain', num2str(Volts(k)));
%sim('sine', [0 1.1]); % run simulation sine.slx  set simulation time 0<t<2
simout{k}=sim('sine');

end
toc

working for loop

%' M-File script to plot simulation data '
clc;clear all; 
load_system('sine');  % move to parfor loop
Volts = (1:2:20); % set voltage amplitude;
f = 2 ; % set simulation values for 2hz
iterations=numel(Volts);

for k = 1:iterations
set_param('sine/Amplitude','Gain', num2str(Volts(k))); %  set f value for simulation
sim('sine', [0 1.1]); % run simulation sine.slx  set simulation time 0<t<2
vc(k,:) = yout(:,1); % save capacitor voltage data
end

plot(tout,vc(1,:),tout,vc(2,:),tout,vc(3,:)); % values to plot
xlabel('Time (secs)'); grid;
ylabel('Amplitude (volts)');
st1 = 'F = ';
st2 = num2str(f); % convert V value to string
st3 = ' Hz'; % Greek symbol for Ohm
st4 = ', V = ';
st5 = num2str(Volts(1));
st6 = ' Volts';
sl1 = strcat(st1,st2,st3,st4,st5,st6); % legend 1
st5 = num2str(Volts(2));
sl2 = strcat(st1,st2,st3,st4,st5,st6); % legend 2
st5 = num2str(Volts(3));
sl3 = strcat(st1,st2,st3,st4,st5,st6); % legend 3
title('Voltage Plot Using SIM')
legend(sl1,sl2,sl3);